Anchor Sponges

Sponges are, by their very nature, a challenging group taxonomically. At the macroscopic level, they are often amorphous and indeterminate in appearance. As one taxonomist complained in 1842 (as quoted in Hooper & Van Soest 2002): "there is so much that is in common to them, and each adapts itself so readily to circumstances and assumes a new mask, that it requires a tact, to be gained only by some experience, to recognize them under their guises; while we labour, perhaps in vain, to devise phrases which shall aptly portray to others the characteristics of objects that have no fixed shape, and whose distinctive peculiarities almost cheat the eye". Reliable identification typically requires the close examination of microscopic details, in particular the conformation and arrangement of the mineralised spicules that make up the skeleton of many sponges.

Myxilla incrustans, copyright B. E. Picton.

The Myxillidae are a family of marine sponges that, so far as we currently know, are most diverse in temperate and frigid waters. Like other members of the class Demospongiae, the most diverse of the recognised sponge classes, they have a skeleton of spicules constructed from silica. Different arrangements of spicules allow the body of the sponge to be divided into two layers. In the outer ectosoma, which can be thought of as the 'skin' of the sponge, elongate spicules are vertically radiating or placed in 'bouquet' arrangements with a palisade of vertical spicules surmounted by radiating clusters. These spicules generally have each end similar and may be smooth or spiky. In the inner choanosoma, within which are placed the feeding chambers of the sponge, elongate spicules are placed in a reticulate arrangement. These spicules generally have one end pointed and the other blunt.

Skeletal arrangements and individual spicules from various Myxillidae, from Hooper & Van Soest (2002).

Mixed in amongst these larger megasclere spicules are smaller microscleres that do not form part of the main structural skeleton, though presumably they do help hold the sponge body together. In myxillids, the microscleres generally take the form of anchorate chelae, small curved structures with incurved rounded prongs at each end. Members of the boreal genus Melonanchora have a mixture of chelae and a different type of microsclere shaped like a ribbed rugby ball (Santín et al. 2021). In the Indo-West Pacific genus Psammochela, growing sponges will also incorporate sand from the surrounding environment to supplement the microscleres (de Voogd 2012).

Growth habit of Myxillidae can vary from encrusting to massive to branching. The species Stelodoryx procera, found around the Azores, has a distinctive growth habit with a flattened main body at the end of an elongate stalk. On the whole, though individual species may be distinguished by growth habit, species within a single genus may differ greatly in form. For determining genera, examination of spicules is really the only way to go.

REFERENCES

Hooper, J. N. A., & R. W. M. Van Soest. 2002. Systema Porifera: A guide to the classification of sponges vol. 1. Kluwer Academic/Plenum Publishers.

Santín, A., M.-J. Uriz, J. Cristobo, J. R. Xavier & P. Ríos. 2021. Unique spicules may confound species differentiation: taxonomy and biogeography of Melonanchora Carter, 1874 and two new related genera (Myxillidae: Poecilosclerida) from the Okhotsk Sea. PeerJ 9: e12515.

Voogd, N. J. de. 2012. On sand-bearing myxillid sponges, with a description of Psammochela tutiae sp. nov. (Poecilosclerida, Myxillina) from the northern Moluccas, Indonesia. Zootaxa 3155: 21–28.

The Sordariales: In the Soil and Under the Skin

Microfungi are a very important factor in our lives. They play a key role in assuring that we are not literally up to our armpits in shit. Their hungry little hyphae break down ordure, cleaning up the planet and unlocking nutrients that will then be made available to other organisms. And among the most significant lineages of these largely unseen decomposers are the members of the order Sordariales.

Lab culture of Sordaria fimicola, copyright BlueRidgeKitties.

Members of the Sordariales are, without exception, minute. Many species are coprophilous, growing on dung. Others may be found on rotting wood, or other decaying plant matter or soil. Fruiting bodies, when they appear, are flask-shaped perithecia protruding to a greater or lesser degree from the surface of their substrate. The walls of the perithecia are made up of large cells and have a membranous or coriaceous (leathery) texture. Within the fruiting body, the asci are single-walled and contain one- or two-celled ascospores that are often surrounded by a gelatinous sheath or bear various appendages. If the ascospores are two-celled, the cells are typically differentiated into an apical head and a basal tail (Kruys et al. 2015; Marin-Felix et al. 2020). Genera of Sordariales have historically been recognised on the basis of ascospore morphology but the advent of molecular data has indicated that such genera are highly polyphyletic. As a result, the Sordariales have seen (and are still seeing) a great deal of taxonomic reassessment. Miller & Huhndorf (2005) suggested that the structure of the fruiting body walls are more consistent with molecular phylogenies than ascospore morphology.

Cake of oncom-fermented beans, copyright Hariadhi.

Apart from their significant role as decomposers, most Sordariales have little direct impact on human economics. The mould Neurospora intermedia is used to make oncom, a fermented food similar to tempeh. A number of species of Sordariales such as Neurospora crassa and Sordaria fimicola have been widely used in genetic research, to the extent that they have been labelled the 'fruit flies of the fungal world'. Seriously, it's one of those expressions almost every publication seems obliged to crow-bar in somewhere. The analogy is made even more apropos by the fact that one of the most widely used species, Triangularia née Podospora anserina, has been made the subject of debate whether taxonomic considerations should be allowed to shake up the name of a popular model organism.

Molecular studies have also shown that the Sordariales encompass Madurella mycetomatis, a fungus causing subcutaneous inflammation in humans (van de Sande 2012). Seeing as sexual fruiting bodies are unknown in this species, and even asexual spore-producing structures are exceedingly rare, this organism would have previously been all but impossible to classify. Infection by M. mycetomatis is characterised by the production of granular swellings. It is most significant in central Africa but is also known from other tropical regions of the world. Madurella mycetomatis infects people via trauma such as animal bites and other wounds, and it has been isolated from soil and ant nests. In its normal state, M. mycetomatis is probably a quite innocent soil fungus. The trouble comes when it finds itself somewhere it shouldn't be.

REFERENCES

Kruys, Å., S. M. Huhndorf & A. N. Miller. 2015. Coprophilous contributions to the phylogeny of Lasiosphaeriaceae and allied taxa within Sordariales (Ascomycota, Fungi). Fungal Diversity 70: 101–113.

Marin-Felix, Y., A. N. Miller, J. F. Cano-Lira, J. Guarro, D. García, M. Stadler, S. M. Huhndorf & A. M. Stchigel. 2020. Re-evaluation of the order Sordariales: delimitation of Lasiosphaeriaceae s. str., and introduction of the new families Diplogelasinosporaceae, Naviculisporaceae, and Schizotheciaceae. Microorganisms 8: 1430.

Miller, A. N., & S. M. Huhndorf. 2005. Multi-gene phylogenies indicate ascomal wall morphology is a better predictor of phylogenetic relationships than ascospore morphology in the Sordariales (Ascomycota, Fungi). Molecular Phylogenetics and Evolution 35: 60–75.

van de Sande, W. W. J. 2012. Phylogenetic analysis of the complete mitochondrial genome of Madurella mycetomatis confirms its taxonomic position within the order Sordariales. PLoS One 7 (6): e38654.

The Cephalodiscids

Among the more obscure inhabitants of the world's oceans are the Cephalodiscidae, a family of small (only a few millimetres in length), largely sessile animals that mostly live in colonies within a shared domicile. Though rarely observed, cephalodiscids have received their fair share of attention due to being among the closest living relatives of the graptolites that once dominated the world's oceans during the early Palaeozoic era.

Preserved Cephalodiscus colony, copyright E. A. Lazo-Wasem.

Cephalodiscids are one of the two living branches of the pterobranchs (the other being the Rhabdopleuridae), which together with the acorn worms make up the phylum Hemichordata. Hemichordates are in turn one of the three living phyla of the deuterostomes, together with the echinoderms and chordates (to which, of course, we ourselves belong). Pterobranchs are filter feeders, using an arrangement of tentaculated arms arising just behind the head to collect particles from the water. In cephalodiscids, each individual usually possesses multiple pairs of arms in contrast to the single pair in rhabdopleurids (though at least one species of Cephalodiscus has small males with a single pair). The head carries a large glandular disc (hence the name of the family) that is used to secrete the horny tissue making up the external dwelling (referred to as the tubarium) in which a colony of Cephalodiscus lives. Both cephalodiscids and rhabdopleurids have a contractile stalk at the end of the body from which new individuals (zooids) are budded. However, whereas the zooids of rhabdopleurids (and presumably their extinct graptolite relatives) remain attached to each other throughout their life, cephalodiscid zooids split away from their parent by the time they mature. The majority of cephalodiscid species have distinct males and females though a small number may be hermaphrodites. Some species exhibit sexual dimorphism; males may be considerably smaller than females.

Individual zooid of Cephalodiscus dodecalophus, from Sedgwick et al. (1898).

About twenty species of living cephalodiscids are currently recognised. The majority of these have been included in a single genus Cephalodiscus, albeit divided between a number of subgenera. The single outlier, Atubaria heterolopha, was described in 1936 from a single dredge haul near Japan (Mitchell et al. 2013). No dwelling material was found in the haul so it was presumed this species does not construct a tubarium like other cephalodiscids. However, its zooids were otherwise little different from those of Cephalodiscus. The subgenera of Cephalodiscus are mostly distinguished by tubarium structure. In some species, each individual in the colony will have its own separate tube closed off at the base. In other species, tubes will open into a central chamber shared between multiple zooids (Maletz 2014). Openings of the tubarium may be surrounded by spines and the like, secreted by the zooids as they creep out from their domicile.

Recent studies have indicated that cephalodiscids represent the sister group to all other pterobranchs/graptolites, implying an history that may extend back to the Cambrian. However, the fossil record of cephalodiscids themselves is minimal. This is largely due to practical difficulties: because the soft-bodied zooids are not preserved, fossils can only be identified from the external tubarium structure alone. Unless the origin point of the tubarium is preserved and identifiable, there is little to distinguish a cephalodiscid tubarium from a benthic graptolite (graptolite colonies begin with a differentiated larval chamber called a sicula, cephalodiscids produce no such structure). A handful of fossil cephalodiscids have been identified, notably the early Devonian Eocephalodiscus, but as yet they tell us little about the evolution of this ancient lineage.

REFERENCES

Maletz, J. 2014. The classification of the Pterobranchia (Cephalodiscida and Graptolithina). Bulletin of Geosciences 89 (3): 477–540.

Mitchell, C. E., M. J. Melchin, C. B. Cameron & J. Maletz. 2013. Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite. Lethaia 46: 34–56.

The Fate of Oligochiton

Chitons are one of the most distinctive and evolutionarily divergent groups of molluscs alive today. But compared to other groups of molluscs, the fossil record of chitons is rather sparse—or at least sparsely studied. It's not hard to see why. The multi-plated nature of the chiton shell means that it tends to fall apart after death, and the structure of the plates is such that critical features are easily abraded.

(Clockwise from top left) head, intermediate and tail valves of Lepidochitona lioplax, from Dell'Angelo et al. (2011).

Lepidochitona lioplax is one example of a fossil chiton. It was originally described from Oligocene rocks belonging to the Sooke Formation of southern Vancouver Island in British Columbia. Only four moderate-sized valves were initially identified: one head valve, one intermediate, and two tails (so at least two individuals were involved). The valves had a smooth outer surface without a strong distinction in appearance between the central and lateral areas. The insertion plates (lateral projections of the lower surface of the valves that in life anchor them into the surrounding girdle) were very short. The sutural laminae (anterior projections of the lower surface of the intermediate and tail valves that articulate with the valve in front) were low, wide, and divided in the middle by a broad shallow surface. Slits in the lateral insertion plates were numerous, with several in the tail valves and probably two or three on each side in the intermediate valves (Smith 1960). When first described, this species was thought distinct enough to belong in its own genus Oligochiton.

Oligochiton lioplax would then go little reported on until 2011 when Dell'Angelo et al. described an assemblage of chiton fossil from the latest Eocene or early Oligocene of the Lincoln Creek Formation in Washington State. Specimens of lioplax were relatively numerous in this collection and Dell'Angelo et al. were able to examine close to a hundred valves. Their observations would lead to something of a downgrade in the species status. Rather than deserving its own extinct genus, Dell'Angelo et al. felt that lioplax could be comfortably accommodated in the living genus Lepidochitona. Its smooth valves are unusual within Lepidochitona but not unique. The supposed multiple slits in the sides of the valves did not stand up to scrutiny. Instead, intermediate valves of L. lioplax bore only a single slit on each side, in line with other Lepidochitona species. The original inference of multiple slits was an error due to the original specimen being still partially embedded in the surrounding matrix.

Lepidochitona lioplax is one of the earliest known representatives of its genus but its exact significance is obscure. It has been suggested as a direct ancestor of the modern subgenus Spongioradsia but this, again, was based on the supposed slits in the intermediate valves that Dell'Angelo et al. refuted. To know how L. lioplax connects to the big picture of Lepidochitona evolution, we would probably need a better picture of Lepidochitona evolution overall.

REFERENCES

Dell'Angelo, B., A. Bonfitto & M. Taviani. 2011. Chitons (Polyplacophora) from Paleogene strata in western Washington State, U.S.A. Journal of Paleontology 85 (5): 936–954.

Smith, A. G. 1960. Amphineura. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I41–I76. Geological Society of America, and University of Kansas Press.

In the Arms of Pseudisograptus

From the Ordovician to the early Devonian, the graptoloids were a major component of the oceanic fauna. These colonial floaters are among the characteristic fossils of the early Palaeozoic and have received a lot of attention due to their use in biostratigraphy. The evolution of graptoloids has been presented as a process of increasing simplification, of progressive reductions in colonial complexity and density. Like all illustrations of evolutionary trends, this is an overly simplistic representation of how things actually occurred but it's not entirely incorrect. The history of graptoloids was indeed marked by a number of significant transitions were particular growth forms overran their predecessors. One genus that may have played a significant role in the lead-up to one of these turnovers was Pseudisograptus.

Pseudisograptus manubriatus koi, entire fossil and close-up diagram of initial thecae, from Cooper & Ni (1986).

The graptoloid genus Pseudisograptus has been collected from rocks in Australia, North America and eastern Asia dating to the latter part of the Floian stage of the early Ordovician, a bit over 470 million years ago (Cooper & Ni 1986). It is characterised by colonies growing in two branches (stipes) with the stipes spreading outwards and upwards like a pair of wings (indeed, one species of this genus luxuriates in the name of Pseudisograptus angel). In large specimens, the stipes reach about two centimetres in length and about three millimetres wide (from inner margin to the outer apex of the individual thecae). Pseudisograptus species are very similar to, and until 1972 where classified with, species of the related genus Isograptus. They differ, however, in the arrangement and growth of the earliest thecae in the colony. Whereas Isograptus stipes grow outwards immediately from the oldest theca, Pseudisograptus have the first few thecae on each stipes elongated and growing downwards before the stipes makes a later sharp turn upwards. As a result, between the two 'wings' of the stipes there is a more or less distinct triangle (referred to as the manubrium) formed from the bases of the early thecae. At the top of the manubrium is an upright thread, the nema. In a number of graptoloid fossils, an inflated structure has been identified at the top of the nema that probably functioned as a float. I don't know if such a structure has ever been identified in a Pseudisograptus fossil but I imagine it would quite easily be lost in the course of preservation.

Basal section of Cardiograptus amplus, from Fortey et al. (2005). Not a true biserial graptoloid but illustrative of the way biserial forms may have evolved from biramous ancestors.

Pseudisograptus' disappearance from the fossil record coincides with one of the aforementioned turnovers in graptoloid diversity, the appearance of the biserial graptoloids. These forms, which had two rows of thecae arising from a single central line, rapidly replaced most of the earlier branched forms. The rapid appearance of the biserial graptoloids has made their origins difficult to work out but current thinking is that they arose from a form similar to Pseudisograptus, in which the upward growth of the stipes became steep enough that they met in the middle along the nema. One interesting detail is that two lineages appear to have achieved biseriality at about the same time from closely related but separate ancestors. In the glossograptids, the conjoined stipes met each other side-by-side; in the diplograptids, they met back to back. Pseudisograptus has, at different times, been implicated in the ancestry of both of these groups. Cooper & Ni (1986) regarded Pseudisograptus as paraphyletic and including the direct ancestors of the glossograptids. In contrast, more recent studies by Fortey et al. (2005) and Maletz et al. (2009) have placed Pseudisograptus closer to the diplograptids. These studies have been more agnostic as to whether Pseudisograptus was a direct ancestor or a close relative. If the former is the case then, while the exact Pseudisograptus morphotype would disappear at the end of the Floian, their genetic lineage would continue strong for nearly ninety million more years.

REFERENCES

Cooper, R. A., & Ni Y. 1986. Taxonomy, phylogeny, and variability of Pseudisograptus Beavis. Palaeontology 29 (2): 313–363.

Fortey, R. A., Y. Zhang & C. Mellish. 2005. The relationships of biserial graptolites. Palaeontology 48 (6): 1241–1272.

Maletz, J., J. Carlucci & C. E. Mitchell. 2009. Graptoloid cladistics, taxonomy and phylogeny. Bulletin of Geosciences 84 (1): 7–19.

Gastrotrichs and their Tacky Little Tubes

When I was a student, I was taught that known animal diversity could be divided between somewhere in the region of a couple of dozen 'phyla'. These were the fundamental units of animal classification, the basic archetypes of animal morphology. Many of these were the major assemblages with which we all were familiar: chordates, arthropods, molluscs and the like. But many were the so-called 'lesser phyla', those taxonomic orphans that, whether small in size or small in number or both, tended to escape observation and study by the majority of people. One such 'minor phylum' was the collection of small worm-like animals known as the Gastrotricha.

Polymerurus nodicaudus, a paucitubulate gastrotrich, from Balsamo et al. (2015). Scale bar equals 100 µm.

Gastrotrichs are, in general, minute (Todaro et al. 2019). The largest reach about three-and-a-half millimetres in length, the smallest are about sixty microns, and there are probably many more at the lower range than the higher. They are dorsoventrally flattened with numerous cilia, and their cuticle may often be differentiated into a covering of scales or spines. Gastrotrichs are aquatic and are often referred to as part of the meiofauna, the assemblage of animals specialised for living within and crawling through the spaces between sand grains. That is indeed the preferred habitat for many species and gastrotrichs may be among the most abundant inhabitants of this milieu, edged out only by the nematodes and copepods. However, other species live above the sediment surface, crawling over the surface of aquatic vegetation or even floating among the plankton. Over 850 species are known to date, of which are a bit over 500 are marine (with all marine species being meiofaunal) and the remainder are found in fresh water. They feed on micro-organisms such as bacteria and algae, swallowing them by means of a muscular pharynx.

Gastrotrichs differ from other animals in a number of significant features. Among these is the differentiation of the outer cuticle into two distinct layers. The outermost of these layers, the epicuticle, covers the entire outer surface of the body, including coating the cilia. Gastrotrichs also possess characteristic tubular outgrowths ending in adhesive glands. Their relationships to other animals remain uncertain. Most authors now agree that they represent an early-diverging branch of the Lophotrochozoa, the animal superclade including such creatures as molluscs and annelids. It is possible that they are more closely related to flatworms than anything else but even then the relationship would hardly be close.

Pseudostomella etrusca, a macrodasyidan gastrotrich, from Todaro et al. (2011). Scale bar = 50 µm.

Historically, gastrotrichs have been divided between two orders, the Macrodasyida and Chaetonotida. This division was supported by structural features of the pharynx and the body wall but is also reflected in the distribution of the adhesive tubes. The Macrodasyida, which are usually vermiform, possess adhesive tubules at both the anterior and posterior ends of the body, as well as laterally. Macrodasyidans are always interstitial in habits and usually marine. The Chaetonotida, on the other hand, lack anterior tubules. Chaetonotidans were further divided between two major taxa. One of these was the isolated genus Neodasys which is vermiform and interstitial like a macrodasyidan, and possesses both lateral and posterior tubules. The remaining Chaetonotida were recognised as the suborder Paucitubulatina. As indicated by their name (meaning 'few tubules'), members of this suborder are characterised by the reduction in number of adhesive tubules, usually to a single pair at the end of the body (a few species have two pairs of tubules, others lack distinct tubules and have the adhesive glands opening directly on the main body). They are short, generally shaped more or less like a bowling pin, and are the most ecologically diverse major gastrotrich group, including both marine and freshwater forms.

A phylogenetic analysis of gastrotrichs by Kieneke et al. (2008), however, questioned the established classification of the group. Rather than affirming a basal division between Chaetonotida and Macrodasyida, their results placed Neodasys as the sister group of all other gastrotrichs. Such a division may be reflected in the nature of their adhesive tubules: Neodasys has tubules containing a single gland but Macrodasyida and Paucitubulatina have two glands per tubule (unfortunately, because of the lack of close outgroups, it's hard to know which tubule type was ancestral). Within the Macrodasyida + Paucitubulatina clade, the macrodasyidans were then paraphyletic to the paucitubulates. Interestingly, the sister group to the Paucitubulatina was a clade of the only two known freshwater macrodasyidans, Marinellina and Redudasys. The implication was that gastrotrichs may have made the move to fresh water on just one occasion (followed by a number of returns to the sea among paucitubulates). This is not an isolated case: a number of phylogenetic studies of micro-organisms have found deep divides between marine and freshwater lineages. It seems it's hard to adjust to a life less salty.

REFERENCES

Kieneke, A., O. Riemann & W. H. Ahlrichs. 2008. Novel implications for the basal internal relationships of Gastrotricha revealed by an analysis of morphological characters. Zoologica Scripta 37 (4): 429–460.

Todaro, M. A., J. A. Sibaja-Cordero, O. A. Segura-Bermúdez, G. Coto-Delgado, N. Goebel-Otárola, J. D. Barquero, M. Cullell-Delgado & M. Dal Zotto. 2019. An introduction to the study of Gastrotricha, with a taxonomic key to families and genera of the group. Diversity 11: 117.

Eurotiomycetes: Small but Significant Fungi

Mention the word 'fungi' and most people's thoughts will probably go to images of mushrooms or toadstools. A few may conjure up pictures of lichens. Nevertheless, the great majority of fungal species are microscopic and likely to pass unremarked by most observers. That does not, however, mean that they are of no consequence. Today's post involves one major group that, for all their visual insignificance, include some of the most significant fungal species for modern human society: the Eurotiomycetes.

Developmental stages of Aspergillus glaucus, with cleistothecia as figs 21–23, from Raper & Fennel (1965).

The class Eurotiomycetes has been recognised in recent years as including a diverse assemblage of fungi, associated with a wide range of morphologies and habitats, that are united as a clade by molecular analyses. Réblová et al. (2017) recognised five subclasses within the Eurotiomycetes of which the two largest (or at least the most studied) are the Eurotiomycetidae and the Chaetothyriomycetidae. The Eurotiomycetidae are, for the greater part, saprobes. They were largely recognised as a distinctive group even before the advent of molecular phylogenetic analysis owing to the production by sexually reproducing forms of a distinctive type of fruiting body, the cleistothecium. In cleistothecia, the fruiting body is completely enclosed with no openings to faciliatate the release of spores, which only escape when the fruiting body itself breaks down. Cleistothecia are most commonly produced by fungi that grow in enclosed locations such as underground (the Eurotiomycetidae are not the only group of fungi to produce cleistothecia though they are one of the most diverse). Within the cleistothecium, spores develop within globular asci with a single wall that breaks down shortly after maturity (Geiser et al. 2015).

Penicillium expansum on rotting pear, copyright H. J. Larsen.

For many people, though, the most familiar members of the Eurotiomycetidae are likely to be asexually reproducing forms. This is the clade containing the moulds of the genera Aspergillus and Penicillium. Even before a species of the latter achieved fame as the shource of the first known antibiotic, penicillin, members of these genera had a great impact on human lives. Species of Penicillium are the moulds used in the production of cheeses such as Roquefort and camembert. Species of Aspergillus are used to ferment soy beans and rice in the production of comestibles such as soy sauce and sake. On the flip side, a number of species of Eurotiomycetidae act as pathogens of mammals including humans, causing conditions such as respiratory illnesses or tinea, with the former being of particular concern in immunocompromised individuals. Eurotiomycetid moulds may also cause problems for food storage and the like, particularly as many species are capable of growing under remarkably hot and/or dry conditions. Some Aspergillus moulds produce dangerous toxins, capable of causing acute poisioning or cancer development.

Verrucaria maura, copyright Richard Droker.

The Chaetothyriomycetidae are less clearly defined morphologically than the Eurotiomycetidae but fruiting bodies are mostly produced as perithecia: flask-shaped structures with an apical pore through which spores are released. The asci within the perithecium usually possess a double wall. Like many eurotiomycetids, chaetothyriomycetids have a tendency to be associated with habitats where water availability is a concern such as in very dry and/or saline environments. A number of chaetothyriomycetid species form lichens. One genus, Verrucaria, is often found as a thin black lichen growing on rocks along the seashore. Some species grow within the cavities of myrmecophytes, plants that form mutualistic associations with ants (the plant provides food and/or accomodation for the ants and the ants help keep the plant clear of grazers or sap-suckers). The fungi are cultivated by the ants that use them for food.

The other three subclasses of the Eurotiomycetes are less well known and recognised as containing a single order each. The Sclerococcales were first recognised as such by Réblová et al. (2017) via molecular analysis. Fruiting bodies, where known, are apothecia (open bowls) bearing single-walled asci. Representatives are known from marine and terrestrial habitats, growing on wood or lichens, and some have been isolated from within the digestive tracts of bark beetles. The Coryneliaceae, living as parasites on podocarps, have been considered as morphologically intermediate between chaetothyriomycetids and eurotiomycetids. Molecular analysis positions them as sister to the latter (Wood et al. 2016). Finally, the Mycocaliciales live as parasites or commensals of other fungi, particularly lichens.

There are other representatives of the Eurotiomycetes that I haven't even had the time to gloss over, such as endophytes and ectomycorrhizal truffles. You may not know they're there but that doesn't mean they don't mean anything to you.

REFERENCES

Geiser, D. M., K. F. LoBuglio & C. Gueidan. 2015. Pezizomycotina: Eurotiomycetes. In: D. J. McLaughlin, & J. W. Spatafora (eds) The Mycota 2^nd ed. vol. 7. Systematics and Evolution part B pp. 121–141. Springer-Verlag: Berlin.

Réblová, M., W. A. Untereiner, V. Štěpánek & W. Gams. 2017. Disentangling Phialophora section Catenulatae: disposition of taxa with pigmented conidiophores and recognition of a new subclass, Sclerococcomycetidae (Eurotiomycetes). Mycological Progress 16: 27–46.

Wood, A. R., U. Damm, E. J. van der Linde, J. Z. Groenewald, R. Cheewangkoon & P. W. Crous. 2016. Finding the missing link: resolving the Coryneliomycetidae within Eurotiomycetes. Persoonia 37: 37–56.

The Glyceriforms: Stabby Worms and Grabby Worms

Historically, the annelid worms have been considered a difficult group to classify. Whereas most of the recognised families have been fairly well established, higher taxa uniting these families have tended to be a bit on the vague side. Nevertheless, there are some supra-familial groups that can be considered well established, one such group being the Glyceriformia.

Specimen of Goniadidae (head to the right), from NOAA Fisheries.

The glyceriforms are two families of marine worms, the Glyceridae and Goniadidae. More than a hundred species are known in this clade (over forty glycerids and over sixty goniadids), found in habitats ranging from the intertidal to the abyssal. They range in size from about a centimetre in length to well over half a metre. The front end of the body tapers to a narrow, elongate conical point in front of the mouth, bearing two terminal pairs of small, slender appendages that may correspond to the antennae and palps of other worms. Eyes may be present or absent. The pharynx forms a remarkably elongate, eversible proboscis. In Glyceridae, the proboscis ends in a ring of four hook-shaped jaws, all similar to each other. In Goniadidae, the arrangement of jaws is more complex with the usual arrangement being small micrognaths on one side of the ring and larger macrognaths on the other. Glycerids usually have a transparent skin and an overall red or white colour reflecting the coloration of the internal fluids (red-coloured individuals are sometimes known as 'bloodworms', as are many other similarly coloured worm-like invertebrates). Goniadids have a more opaque cuticle and often have an iridescent sheen (Rouse & Pleijel 2001).

Glycera dibranchiata with everted proboscis, from the Yale Peabody Museum.

Glyceriforms most commonly live as burrowers in muddy or sandy substrates though some live on the surface of rocks. Most are carnivores of active invertebrates such as crustaceans or other worms; some may be detritivores. They may be vagile or they may construct permanent galleries of burrows with multiple entrance and exit openings in which they wait to lunge at anything foolish enough to pass nearby. In glycerids, the stabby jaws are associated with venom glands leading to ducts opening through pores on the jaw's underside. In some species, this venom is strong enough to cause a painful reaction in humans (though I haven't come across any references to long-term consequences). Goniadids lack venom glands and seem to rely on the physical use of their jaws to capture prey. As with many other marine worms, reproduction happens via pelagic epitokes. As a suitable time approaches (Prentiss, 2020, records goniadid epitokes emerging only during a full moon), the glyceriform worm undergoes a metamorphosis involving the break-down of the digestive system and enlargement of the parapodia. The transformed epitokes swim towards the surface where they release gametes through ruptures of the body wall, ending their life in a suicidal orgasm.

Close-up on proboscis of Glycera alba, copyright Hans Hillewaert.

Because of their hardened jaws, which are mostly constructed of protein but partially mineralised, glyceriforms have quite a good fossil record compared to many other worms (Böggemann 2006). Fossilised glyceriform jaws have been found as far back as the Triassic and are little different from those of modern glyceriforms. Body fossils are, unsurprisingly, much rarer but a worm from the Carboniferous Mazon Creek fauna, Pieckonia helenae, has been identified as a stem-group goniadid. The glyceriform body plan seems to have been a very successful one, remaining essentially unchanged over hundreds of millions of years.

REFERENCES

Böggemann, M. 2006. Worms that might be 300 million years old. Marine Biology Research 2: 130–135.

Prentiss, N. K. 2020. Nocturnally swarming Caribbean polychaetes of St. John, U.S. Virgin Islands, USA. Zoosymposia 19: 91–102.

Rouse, G. W., & F. Pleijel. 2001. Polychaetes. Oxford University Press.

Tricolia: Fluorescent Seashells

Tricolia pullus, copyright Ar rouz.

Search among patches of seaweed along the shores of Africa, Australia or warmer parts of Eurasia and you may be able to find represents of the marine gastropod genus Tricolia. Tricolia are small shells, less than a centimetre in height, with shiny shells that may be smooth or spirally ribbed. Most species have a moderately high spire and an ovate shape but some are lower and more globose (Knight et al. 1960). The shell may or may not have an umbilicus, and there is a calcareous, externally convex operculum. Tricolia belongs to the Phasianellidae, commonly known as pheasant shells, presumably in reference to the bold, intricate colour patterns of many species. Species of Tricolia and the closely related genus Eulithidium, which replaces it in the Americas, have shell pigments containing porphyrin that fluoresce under ultraviolet light (Vafiadis & Burn 2020). Over forty species of Tricolia are currently recognised with the highest diversity in southern Africa (Nangammbi et al. 2016). However, the taxonomy of the genus has historically been confused due to polymorphic species being named multiple times; it is possible that at least some of the apparent African diversity is an artefact of the genus being largely unrevised in that region. An analysis of some of the southern African taxa by Nangammbi et al. (2016) found that some 'species' could not be distinguished genetically. They were, nevertheless, distinct geographically and the authors suggested that they may be variants of a single species responding to different environments.

Variants of Tricolia kochii, copyright Brian du Preez.

Like other members of the Vetigastropoda (the clade containing most of what used to be called the 'archaeogastropods'), Tricolia species have a simple life cycle without an actively feeding planktonic larva. The basic mode of reproduction is by broadcast spawning with separate males and females releasing gametes into the water column. After fertilisation, a brief non-feeding planktonic phase is nourished by yolk from the egg before the larva settles. The brevity of this phase is reflected by the resultant form of the protoconch which accounts for less than an entire whorl. In the Indo-West Pacific species T. variabilis, the male is smaller than the female and sits directly on her, waiting to fertilise her eggs as they are laid as gelatinous capsules rather than freely broadcasted. A temperate Australian species, T. rosea, takes things a step further as the female broods embryos (up to nearly fifty at a time) within the cavity of the last shell whorl (Vafiadis & Burn 2020). How the eggs are actually fertilised remains unknown but all embryos within a brood are about the samesize and stage of development, indicating a single fertilisation event; perhaps males associate with females as in T. variabilis. After the young pheasant shells hatch or settle, they initially feed on diatoms and other microalgae until they eventually grow enough to move onto the seaweed fronds that will comprise their adult diet.

REFERENCES

Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: R. C. Moore (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1. Mollusca—general features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—general features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I171–I351. Geological Society of America: Boulder (Colorado), and University of Kansas Press: Lawrence (Kansas).

Nangammbi, T. C., D. G. Herbert & P. R. Teske. 2016. Molecular insights into species recognition within southern Africa's endemic Tricolia radiation (Vetigastropoda: Phasianellidae). Journal of Molluscan Studies 82: 97–103.

Vafiadis, P., & R. Burn. 2020. Internal embryonic brooding and development in the southern Australian micro-snail Tricolia rosea (Angas, 1867) (Vetigastropoda: Phasianellidae: Tricoliinae). Molluscan Research 40 (1): 60–76.

Key Limpets

On two occasions before, I've presented you with members of the Fissurellidae, the keyhole and slit limpets. It's time for a return visit to the fissurellids, in the form of the diverse keyhole limpet genus Diodora.

Various views of shell of Diodora italica, copyright H. Zell.

Species have been assigned to Diodora from coastal waters pretty much around the world except for the coolest regions. They are small to moderate-size limpets, the largest species growing about three centimetres in length and two centimetres in height. The shell opens through a 'keyhole' at the apex through which the animal ejects waste matter and water that has been passed over the gills. The internal margin of this keyhole is surrounded by a callus on the underside of the shell; a distinguishing feature of Diodora is that this callus is posteriorly truncate. The external ornament of the shell is cancellate (arranged in a criss-cross pattern) and the margin of the shell is internally crenulated (Moore 1960). Moore (1960) listed three subgenera of Diodora distinguished by features of the keyhole shape and position but Herbert (1989) notes that these subgenera are not clearly distinct. A phylogenetic analysis of the fissurellids by Cunha et al. (2019) did recognise a clade including the majority of Diodora species analysed. However, species from the eastern Pacific formed a disjunct clade that may prove to warrant recognition as a separate genus.

As far as is known, Diodora species have a long lifespan, surviving for some ten to twenty years. They do not have a planktonic larva; young Diodora hatch directly from the egg as benthic crawlers. For the most part, they are presumed to graze on algae in the manner of other fissurellids and limpets. However, the northeastern Australian species D. galeata has been found feeding on the soft tissues of coral (Stella 2012), a habit that went unrecognised until fairly recently owing to the animal's cryptic nature, hiding deep among the branches of the host. Whether other Diodora species might exhibit similar lifestyles would require further investigation.

REFERENCES

Cunha, T. J., S. Lemer, P. Bouchet, Y. Kano & G. Giribet. 2019. Putting keyhole limpets on the map: phylogeny and biogeography of the globally distributed marine family Fissurellidae (Vetigastropoda, Mollusca). Molecular Phylogenetics and Evolution 135: 249–269.

Herbert, D. G. 1989. A remarkable new species of Diodora/i> Gray, 1821 from south-east Africa (Mollusca: Gastropoda: Fissurellidae). Annals of the Natal Museum 30: 173–176.

Moore, R. C. (ed.) 1960. Treatise on Invertebrate Paleontology pt I. Mollusca 1. Mollusca—general features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—general features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia. Geological Society of America, Inc. and University of Kansas Press.

Stella, J. S. 2012. Evidence of corallivory by the keyhole limpet Diodora galeata. Coral Reefs 31: 579.

Donaldina: Palaeozoic Turrets

Within the last few decades, we've developed a reasonably good idea of what are the primary subdivisions of gastropods alive today. One such generally accepted lineage is the Heterobranchia (or, depending on the author, the Heterostropha), a group that includes (among others) the air-breathing pulmonates as well as the marine sea slugs and bubble shells. In the fossil record, the roots of this lineage extend well back into the Palaeozoic with early members recognisable by their distinctive mode of shell development. The larval shell, the protoconch, of these forms spirals in the opposite direction from the mature teleoconch, so the animal will start its life sinistral (spiralling left) and end it dextral (spiralling right; if you're having difficulty imagining how this works, the protoconch often ends up sitting upside down relative to the teleoconch). Among the earliest heterobranchs in the fossil record is the genus Donaldina.

Specimen of Donaldina (1.2 mm in height), with close-up of protoconch, from Bandel et al. (2002).

Fossils of Donaldina have been found around the world and the genus persisted for a long time. The earliest potential Donaldina have been described from the Early Devonian but their inclusion in the genus is uncertain (Bandel et al. 2002). The protoconch on these early forms is poorly preserved and it is uncertain whether they truly showed a heterobranch development. The genus was definitely present by the early Carboniferous and persisted into the lower Permian. This is an impressive length of time: the Carboniferous alone last for around sixty million years.

Donaldina was a genus of small, high-spired gastropods, less than a centimetre in height. Many early members of the Caenogastropoda, the likely sister group of the Heterobranchia, also had shells of this kind and it may have represented the ancestral form for the two lineages. The sinistral protoconch of Donaldina was almost planispiral (spiralling in a flat plane) and completed between one and two whorls. The multi-whorled, dextral teleoconch was characterised by an ornament of spiral cords, usually only on the lower half of the whorl.

So what were Donaldina doing with their time when alive? Modern high-spired gastropods occupy a range of lifestyles, including free-living grazers, burrowers, or sedentary forms that live as filter feeders or parasites of other animals (Signor 1982). The morphology of Donaldina suggests that it is unlikely to be a burrower. The whorls are individually rounded whereas those of habitual burrowers tend to be flattened so the shell moves more smoothly through the sediment. The ornamentation on the underside of the whorl would presumably also have presented resistance to burrowing. The shape of the aperture in Donaldina is more suggestive of a free roamer, as a sinus in the upper part of the outer margin would have allowed the animal to pull back into its shell while the plane of the aperture was held as flat as possible against the substrate to protect against predators. Overall, the lifestyle of Donaldina may not have been dissimilar to that of the modern mudsnails of Cerithium and similar genera, crawling about in search of algae and other tasty morsels.

REFERENCES

Bandel, K., A. Nützel & T. E. Yancey. 2002. Larval shells and shell microstructures of exceptionally well-preserved Late Carboniferous gastropods from the Buckhorn Asphalt Deposit (Oklahoma, USA). Senckenbergiana Lethaea 82 (2): 639–689.

Signor, P. W., III. 1982. Resolution of life habits using multiple morphologic criteria: shell form and life-mode in turritelliform gastropods. Paleobiology 8 (4): 378–388.

The Crossostomatinae of the Mesozoic

The hard shell of many molluscs has left them with an excellent fossil record, one with few rivals among other groups of organisms. As a result, we are aware of a great many molluscan lineages that have inhabited this planet in the past, only to fade away long before the present day. One such group is the gastropod subfamily Crossostomatinae.

Crossostoma specimen, from Szabó et al. (1993).

The Crossostomatinae were Mesozoic representatives of the vetigastropods, one of the major subdivisions of gastropods corresponding to what used to be referred to as the archaeogastropods. Vetigastropods are primarily marine (off the top of my head, I can't think of any that are found in freshwater or terrestrial habitats, though I'm happy to be corrected) and crossostomatines were no exception. The classification of vetigastropods has tended to be rather unsettled but crossostomatines were definitely part of the lineage that includes the modern top shells (Trochidae) and cat's-eyes (Turbinidae), recognised as the superfamily Trochoidea in the recent synoptic classification of Bouchet et al. (2017). Within this lineage, the crossostomatines belong to the group of families possessing a calcareous operculum (sometimes treated as a separate superfamily Turbinoidea, but the significance of the calcareous vs horny operculum division in the trochoids seems to be the subject of debate). In recent treatments, the Crossostomatinae have been included within the family Colloniidae, characterised by the lack of a nacreous layer on the inside of the shell (Monari et al. 1996).

In general, crossostomatines were small shells with a smooth outer surface and broadly rounded whorls. They varied in shape from forms resembling modern cat's-eyes to lower-coiling, almost planispiral forms. A notable feature of the group is a tendency for the top of the aperture to be filled by a callus so the aperture appears almost perfectly circular. Other modifications of the mature shell opening are also common: Crossostoma, for instance, has the outer lip strongly thickened (Knight et al. 1960) whereas the final whorl of Adeorbisina turns away slightly from the regular coiling axis so that in top-down view the shell appears to bulge outwards before the terminus (Szabó et al. 1993).

Though they persisted through most of the Mesozoic, the number of known crossostomatine genera does not appear to be large. They seem to be associated with hard-ground deposits (Conti & Szabó 1987) so it is possible the group was more diverse in high-energy environments (organisms living in such environments, for instance along rocky shores, tend not to get preserved in the fossil record because their remains are broken up by wave action). It is possible that their lineage did not truly go extinct in the Mesozoic: Szabó et al. (1993) allude to the possibility of crossostomatines being ancestral to the subfamily Colloniinae, members of which may have survived to the Pliocene. Nevertheless, the Colloniidae as a whole did not survive to the present day, and it seems the line of the crossostomatines may have entirely passed from this Earth.

REFERENCES

Bouchet, P., J.-P. Rocroi, B. Hausdorf, A. Kaim, Y. Kano, A. Nützel, P. Parkhaev, M. Schrödl & E. E. Strong. 2017. Revised classification, nomenclator and typification of gastropod and monoplacophoran families. Malacologia 61 (1–2): 1–526.

Conti, M. A., & J. Szabó. 1987. Comparison of Bajocian gastropod faunas from the Bakony Mts. (Hungary) and Umbria (Italy). Annales Historico-Naturales Musei Nationalis Hungarici 79: 43–59.

Knight, J. B., L. R. Cox, A. M. Keen, R. L. Batten, E. L. Yochelson & R. Robertson. 1960. Gastropoda: systematic descriptions. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt I. Mollusca 1: Mollusca—General Features, Scaphopoda, Amphineura, Monoplacophora, Gastropoda—General Features, Archaeogastropoda and some (mainly Paleozoic) Caenogastropoda and Opisthobranchia pp. I169–I331. Geological Society of America, and University of Kansas Press.

Monari, S., M. A. Conti & J. Szabó. 1996. Evolutionary systematics of Jurassic Trochoidea: the family Colloniidae and the subfamily Proconulidae. In: Taylor, J. D. (ed.) Origin and Evolutionary Radiation of the Mollusca pp. 199–204. Oxford University Press: Oxford.

Szabó, J., M. A. Conti & S. Monari. 1993. Jurassic gastropods from Sicily; new data to the classification of Ataphridae (Trochoidea). Scripta Geologica, Special Issue 2: 407–416.

Aidanosagitta

If you've ever spent time, as I certainly did back in my undergraduate days, thumbing through textbooks of animal diversity, then you may be familiar with the so-called 'minor phyla'. These are those isolated subgroups of the animal kingdom that are phylogenetically remote from other such taxa but which, owing to low diversity and/or low exposure, are commonly not regarded as warranting more than a cursory summary in the end-papers of some other more prominent group. One such group is the arrow worms (Chaetognatha), and for this post I'm focusing on the arrow worm genus Aidanosagitta.

Arrow worms are marine micropredators, slender-bodied animals mostly growing to a bit less than a centimetre in length but generally not seen without the aid of a microscope due to being mostly transparent. The greater number of arrow worm species are planktonic and could be described as superficially fish-like with paired fins running down the side of the body. The front of the head forms a flexible hood within with the mouth is flanked by elongate spines, used for grasping prey.

Two Aidanosagitta species: A. bella (above) and A. venusta (below), from Kasatkina & Selivanova (2003).

A review of the arrow worms by Tokioka (1965) recognised fifteen genera within the phylum. Aidanosagitta is one of the planktonic genera; currently, about thirty species are recognised within this genus. Distinguishing features of the genus include a firm, muscular body, diverticula arising from the gut, and the posterior pair of fins being located on the 'tail' section of the body (behind the anus) (Kasatkina & Selivanova 2003).

The majority of Aidanosagitta species are found in tropical and subtropical waters, most commonly in inlets and lakes. An exception is provided by a number of species found in colders waters adjoining the north-west Pacific, in the Sea of Okhotsk and the Sea of Japan (Kasatkina & Selivanova 2003). Species are distinguished by features such as the sizes of the fins, the size and position of the large subenteric ganglion, and the presence and extent of a layer of spongy tissue that may partially cover the outside of the body. Particular species of arrow worms may be associated with particular bodies of water (such as particular currents) and changes in their distribution may indicate changes in the greater environment.

REFERENCES

Kasatkina, A. P., & E. N. Selivanova. 2003. Composition of the genus Aidanosagitta (Chaetognatha), with descriptions of new species from shallow bays of the northwestern Sea of Japan. Russian Journal of Marine Biology 29 (5): 296–304.

Tokioka, T. 1965. The taxonomical outline of Chaetognatha. Publications of the Seto Marine Biological Laboratory 12 (5): 335–357.

The Origins of a Closed Bolete

Boletes are a distinctive group of mushrooms in which the underside of the fruiting body is covered by tubular pores instead of gills. Though boletes are classified in the fungal order Boletales, not all members of this order produce bolete-type fruiting bodies (as exemplified in an earlier post). Consider, for example, the case of Gastrosuillus.

'Gastrosuillus' sp., copyright Danny Miller.

Gastrosuillus was recognised in 1989 for a small group of species found in North America that closely resembled members of the more typical bolete genus Suillus (the slippery jacks) except for their production of secotioid fruiting bodies, in which the pores are distorted and do not form a flattened plane, and may remain covered by an external membrane (secotioid fruiting bodies may be considered an intermediate form between typical mushrooms and the gastroid fruiting bodies of fungi such as puffballs). All Gastrosuillus species were extremely rare, known only from single locations or even single collections. Gastrosuillus suilloides and G. amaranthii were found in California, G. imbellus in Oregon, and G. laricinus in New York State. All four were found on the ground in conifer forest; fruiting bodies of G. suilloides could be buried (Bessette et al. 2000).

From its inception, a close relationship with and possibly even derivation from members of the genus Suillus seems to have been on the cards for Gastrosuillus. It should be noted that Suillus was not the only bolete genus with a secotioid satellite: as Gastrosuillus was to Suillus, so Gastroboletus was to Boletus, and Gastroleccinum was to Leccinum. So it should have come as little surprise when a molecular analysis of Gastrosuillus species by Kretzer & Bruns (1997) found them to be nested within Suillus, nor forming a single clade within that genus. Instead, the western species were well separated from the New York G. laricinus. As a result, Kretzer & Bruns advocated the synonymisation of the two genera.

Typical form of larch bolete Suillus grevillei, copyright Luridiformis.

But the demotions didn't stop there. Not only was Gastrosuillus laricinus nested molecularly within Suillus, it appeared to be nested within a particular species, S. grevillei (conversely, the California species form a distinct lineage that is, so far as we know, entirely secotioid; the Oregon G. imbellus has not been examined molecularly owing to difficulties in extracting DNA from the single known specimen). The sole known location for G. laricinus lies within the range of S. grevillei, with the two species having been found in close proximity, and the indications were that G. laricinus was a very recent derivative of S. grevillei or possibly even a mere growth variant. Again, this is not entirely without precedent. Secotioid variants have been recorded of other mushroom species, and secotioid-like forms of the agaricoid mushroom Lentinus tigrinus have even been shown to be the result of a recessive allele of a single gene. Kretzer & Bruns (1997) therefore suggested that G. laricinus be synonymised entirely with S. grevillei. This action does not appear to have gained universal acceptance (for instance, the two are provisionally treated as distinct by Bessette et al., 2000) but is certainly worthy of consideration.

REFERENCES

Bessette, A. E., W. C. Roody & A. R. Bessette. 2000. North American Boletes: A color guide to the fleshy pored mushrooms. Syracuse University Press.

Kretzer, A., & T. D. Bruns. 1997. Molecular revisitation of the genus Gastrosuillus. Mycologia 89 (4): 586–589.

Mystery Fungus

For this week's semi-random taxon, I drew the fungal genus Trichangium. Unfortunately, there's not much I can say about this one. The single species of this genus, Trichangium vinosum was described by German mycologist Wilhelm Kirchstein in 1935 in a volume of the journal Annales Mycologici to which I don't have access (there are other volumes of this journal available at archive.org but seemingly not this one). The original collection was found growing on bark of a pear tree. Since then, Kirchstein's species seems to have gone largely unrecognised. I could find no further records under this name and recent synopses of ascomycete genera (e.g. Lumbsch & Huhndorf 2010) list it incertae sedis in the order Helotiales. Helotiales are mostly minute fungi with cup-shaped fruiting bodies that most commonly grow as saprobes on organic substrates such as fallen logs or humus.

Fruiting body of Unguiculella robergei, copyright Abel Flahaut.

However, in 1962 the British mycologist Richard Dennis noted that Kirchstein's description of Trichangium vinosum bore a close resemblance to another bark-living fungus, Unguiculella robergei, and suggested that the two might be the same species. Unguiculella robergei is itself a very rare fungus, otherwise only known from a handful of records in France and Scotland, seemingly all in the month of April (see MycoDB). It has been recorded from bark and dead twigs of mistletoe and roses, producing dark red, disk- or cup-shaped fruiting bodies less than a millimetre in diameter. These fruiting bodies are covered with small glassy hairs; the hooked shape of these hairs was presumably the inspiration for the genus name meaning a small claw or nail. It is possible, of course, that this fungus is more common than realised: with something this small, you need to be looking for it.

REFERENCE

Dennis, R. W. G. 1962. New or interesting British Helotiales. Kew Bulletin 16 (2): 317–327.

Lumbsch, H. T., & S. M. Huhndorf. 2010. Myconet volume 14. Part One. Outline of Ascomycota—2009. Part Two. Notes on ascomycete systematics. Nos 4751–5113. Fieldiana: Life and Earth Sciences, N.S. 1: 1–64.

With Fronds Like These

I'm sure pretty much anyone who's spent time looking into rock pools along the coast will be familiar with sea anemones. These sessile animals with their squidgy bodies and crown of tentacles can be seen almost anywhere there's a rock for them to stand on and a tide to cover them. As a kid, I used to amuse myself by poking them with a finger, noting the slight velcro-ish feel as the harassed anemone would vainly attempt to sting its attaker as it withdrew for protection. In hindsight, I was perhaps just fortunate that New Zealand anemones lacked the strength of venom to affect a human.

Waratah anemones Actinia tenebrosa, copyright John Turnbull.

Many of the anemones I was encountering as a child probably belong to a particular clade known as the Actinioidea. As recognised by Rodríguez et al. (2014), familiar members of this group include the beadlet anemone Actinia equina* from the Atlantic coasts of Europe and Africa, the red sea anemone Actinia tenebrosa of eastern Australia and New Zealand, and the aggregating anemone Anthopleura elegantissima and giant green anemone Anthopleura xanthogrammica of the Pacific coast of North America. Wikipedia informs me that another actinioid, the snakelocks anemone Anemonia viridis, is eaten after being marinated in vinegar and fried in parts of the Mediterranean. Rodríguez et al. recognised their Actinioidea primarily on the basis of molecular phylogenetic analysis but most members of this group had previously been recognised as relatives due to their possession of a sphincter muscle around the edge of the gastric cavity near the top of the column. This muscle allows the body cavity to be pulled tightly closed, providing protection and, for intertidal species, holding water inside the body to protect against desiccation.

*Actinia equina, offhand, was given its species name by Carl Linnaeus who described it under the name Priapus equinus. 'Equinus' means 'of a horse' whereas 'priapus' means... exactly what you think it means. Yes, the name of this species literally means 'hung like a donkey'.

Pompom anemone Liponema brevicornis, copyright Ocean Networks Australia.

Other common features of actinioids include well-developed muscles around the base of the column and an adhesive basal disc for clinging to rocks. However, both the upper sphincter muscle and the basal muscles have been lost in various subgroups of the actinioids, often at the same time. Anemones lacking these muscles, such as the ghost anemones Haloclava, are generally deeper water forms that do not cling to rocks but instead live burrowed into sand with their tentacles extended above the surface. One such anemone, the twelve-tentacled parasitic anemone Peachia qinquecapitata, develops as a larva as a parasite on the hydrozoan medusa Clytia gregaria. The larvae gain entry to their host by being eaten as food particles but proceed to themselves feed on the contents of the host's gastric cavity and eventually on the host itself. Another group of deep-sea actinioids, including such species as the deeplet anemone Bolocera tuediae and the pompom anemone Liponema brevicornis, are able to shed their tentacles as a defence thanks to small sphincter muscles at the base of each tentacle. Bolocera tuediae, found in the North Sea, is a particularly large anemone reaching up to a foot in diameter.

Aggregating anemones Anthopleura elegantissima fighting over space, copyright Brocken Inaglory. The white 'tentacles' the anemones are extending towards each other are inflated acrorhagi (see below).

Many actinioids form symbiotic associations with microscopic algae such as zooxanthellae, containing them within their body and supplementing their own nutrition through the algae's photosynthesis. A number of species reproduce by brooding larvae within the body cavity, only releasing them when they are more developed and better equipped to survive the outside world. Finally, many species of actinioid have the column ornamented by various protuberances such as vesicles or verrucae. These structures may serve environmental protective functions, such as increasing desiccation resistance or functioning in camouflage. Members of Anthopleura and related genera often have specialised bulbous protuberances called acrorhagi around the distal part of the column (Daly et al. 2017). These acrorhagi are packed with stinging cells and are used not so much to protect against predators as against other sea anemones. The acrorhagi-equipped anemone flails its column about, pressing the acrorhagi against any competitor that gets too close and stinging it until it is forced to back off. Its a tough world out there and any anemone worth its salt has got to be willing to defend its position.

REFERENCES

Daly, M., L. M. Crowley, P. Larson, E. Rodríguez, E. H. Saucier & D. G. Fautin. 2017. Anthopleura and the phylogeny of Actinioidea (Cnidaria: Anthozoa: Actiniaria). Organisms, Diversity & Evolution 17: 545–564.

Rodríguez, E., M. S. Barbeitos, M. R. Brugler, L. M. Crowley, A. Grajales, L. Gusmão, V. Häussermann, A. Reft & M. Daly. 2014. Hidden among sea anemones: the first comprehensive phylogenetic reconstruction of the order Actiniaria (Cnidaria, Anthozoa, Hexacorallia) reveals a novel group of hexacorals. PLoS One 9 (5): e96998.

Psoraceae

Psora decipiens, copyright Troy McMullin.

Just a very quick one today. The photo above is of a member of the Psoraceae, a group of lichens sometimes referred to as 'fishscale lichens'. As their vernacular name indicates, Psoraceae are characterised by a scaly appearance, together with a preference for growing on soil or rock crevices (Ekman & Blaalid 2011). The scaly appearance also gives the family its botanical name: Psora comes from the Greek for 'itch'.

Psora vallesiaca, copyright Leif Stridvall.

Molecular phylogenetic analyses have supported the inclusion of three genera in the Psoraceae, Psora, Protoblastenia and Brianaria (Ekman & Svensson 2014). The last genus was only described recently to include a group of species previously included in a different genus Micarea belonging to an entirely different lichen family, the Pilocarpaceae. Micarea lichens closely resemble Brianaria species in overall appearance but differ in some features including the nature of their algal symbiont. Past authors often assumed that symbiont associations provided little guidance to lichen relationships; it was thought that a germinating lichen fungus would pretty much form a connection with whatever algal species was available. However, more recent investigations have found that the tastes of lichen fungi are more discriminating. Micarea species form associations with small algal cells, four to seven microns in diameter, with thin cell walls that are often found in pairs within the lichen thallus. Brianaria species, in contrast, have larger algal symbionts that are always isolated in the thallus (Andersen & Ekman 2005).

REFERENCES

Andersen, H. L., & S. Ekman. 2005. Disintegration of the Micareaceae (lichenized Ascomycota): a molecular phylogeny based on mitochondrial rDNA sequences. Mycological Research 109 (1): 21–30.

Ekman, S., & R. Blaalid. 2011. The devil in the details: interactions between the branch-length prior and likelihood model affect node support and branch lengths in the phylogeny of the Psoraceae. Systematic Biology 60 (4): 541–561.

Ekman, S., & M. Svensson. 2014. Brianaria (Psoraceae), a new genus to accomodate the Micarea sylvicola group. Lichenologist 46 (3): 285–294.

Rust, Anyone?

At certain times of year, when the weather is warm, you may see patches of yellow or orange appear on plant leaves. It is often particularly notable on grass. These patches are known as rust and are the fruiting bodies of parasitic fungi. In some cases, they may be merely a nuisance or an eyesore. In other cases, their effects can be devastating. Rust fungi may cause enormous damage to commercial crops. One particularly nasty strain of the stem rust Puccinia graminis that goes by the label of TTKSK or Ug99 has been spreading through Africa and Asia since its discovery in Uganda in 1999, causing up to 100% losses in wheat crops where it hits. A similar strain of the same species was recently involved in outbreaks in southern Europe. And this rust can't just be covered over with a bit of bog.

Stem rust Puccinia graminis uredia on wheat, from the US Dept of Agriculture.

Puccinia is the largest genus of rusts with around 3000 known species (Liu & Hambleton 2010), infecting a wide range of host plants. Many rusts have complicated life cycles...or perhaps that should be 'insane'. Some of you may be aware that, until recently, mycologists (researchers of fungi) maintained a system of dual nomenclature that classified sexual and asexual forms of fungi separately, due to the difficulty in matching one to the other*. Rust fungi can have a life cycle involving a sexually reproducing stage and two different asexually reproducing stages on two different hosts, all of them distinct in appearance, so many rust fungal species could masquerade under no less than three distinct names! But then, some species might have simpler life cycles dropping one or more of the possible stages, and some might restrict their attentions to a single host. The difficulty of wrapping one's head around rust life cycles may perhaps best be conveyed by reproducing one paragraph from the review by Petersen (1974), which I invite you to look upon below in all its hideous hideousness:

*I believe that the botanical code of nomenclature was recently changed to no longer allow this set-up as a formal system, but I presume that it's going to take a long time to work that one through.

A complex system of nomenclature has been developed to quickly indicate the stages found in any particular life cycle in the rusts. While easily understood by students of the group with some experi- ence, the system at first appears bewildering. Those taxa which exhibit all five stages during their life history are called Euforms. They may be Heter-Eu- (infecting more than one host) or Aut-Eu- (occurring on a single host). In some rusts, the aecial stage is deleted, or the aecia and aeciospores are morphologically identical to uredia and uredospores, these organisms being termed Brachy-forms. All these forms are autoecious, thus enabling the "aut-" prefix to be dropped. For those organisms in which spermogonia and spermatia are missing, Maire used Cata- as a prefix, but this usage is rarely seen nowadays. When the uredial stage has been dropped, the organism is called an Opsis-form. This may be used as a prefix, such as Opsis- Gymnosporangium, or more commonly as a suffix, such as Gymno- sporangiopsis. Again, forms can be Heter-Opsis-, or Aut-Opsis-. If this life cycle also deleted spermogonia, it was dubbed Catopsis- by Maire. In more general terminology, rust fungi exhibiting chiefly teliospores (with or without spermogonia) are known as Micro-forms, but Maire again specified those which exhibited both telia and spermogonia as Hypo-forms. In these forms, the teliospores are normal in that they require a resting period before germination. In some taxa, teliospore-like propagules are produced which are lighter in color, exhibit thinner walls, and more obscure germ pores, and which require no resting period before germination, often germinat- ing in situ. These spores have been called leptospores, and the life cycle, otherwise identical to that of Micro-forms, is known as Lepto- form. Occasionally, only uredospores and teliospores are found (these sometimes are thought of as imperfect rusts in which other stages will hopefully be found), and these are called Hemi-forms. Finally, in some taxa the teliospores are cytologically similar to aeciospores, in which case the life cycle is called Endo-, the species with such structures often segregated in the genus Endophyllum.

Life cycle of stem rust Puccinia graminis, from US Dept of Agriculture.

A typical 'full' rust life cycle is the one gone through by stem rust, shown in the diagram above. Stem rust alternates between two hosts, grasses such as wheat (it also infects related species such as barley or rye) and barberry. Sexual reproduction occurs on barberry near the beginning of the growing season when haploid spores known as spermatia or pycniospores are produced from fruiting bodies called spermatogonia or pycnia. In Puccinia species, these spermatogonia are flask-shaped and tend to be evenly spaced across the host tissue; other rust fungi may produce more irregular and irregularly-spaced spermatogonia. At the sides of the flask's opening are protruding hyphae to which spermatia from other spermatogonia fuse. Now, in animals such as ourselves, fusion of sperm and ovum is usually immediately followed by fusion of their respective haploid nuclei to form the diploid daughter nucleus. In rusts, however, the haploid parent cells fuse but their nuclei do not. Instead, the daughter cell grows and divides as a dikaryotic organism with two nuclear lineages remaining associated but distinct in each cell. The dikaryotic mycelium produced from fusion of spermatium and receptive hypha gives rise to a fruiting body known as an aecium which in Puccinia is cup-shaped. The aecium produces its own spores that are shed to infect the alternate host, the grass, to which they gain access through the host's stomata. Germinating aeciospores grow into a mycelium that penetrates host cells, absorbing nutrients directly from the host cytoplasm. When the time comes for the next reproductive stage, the rust produces a compacted layer called a uredinium that gives rise to yet another spore type, urediniospores. Unlike aeciospores that travel from one host to another, urediniospores are able to re-infect the same host, giving rise to a new uredinial stage of the life cycle. This asexual sub-cycle continues indefinitely for as long as growing conditions remain good for the rust. When conditions deteriorate, the rust stops producing urediniospores and begins producing thick-walled teliospores that are able to persist through the cold winter. It is within the teliospores that the dikaryotic nuclei finally fuse, giving rise to daughter nuclei that then themselves undergo meiosis so the teliospore germinates at the beginning of the next season to release haploid basidiospores, that infect a barberry to begin the cycle anew.

Arum rust Puccinia sessilis aecia on leaf of Arum maculatum, copyright Velella.

Because of the need for two hosts in the life cycle, crop pests such as stem rust may potentially be controlled by eradicating the second host. However, first you have to know what to target. Stripe rust Puccinia striiformis is another significant pest of grass crops whose alternate host was not identified as barberry until 2010 (Jin et al. 2010). And in warmer climates where urediniospores can survive all year round, rusts may be able to persist asexually even without a suitable alternate host.

REFERENCES

Jin, Y., L. J. Szabo & M. Carson. 2010. Century-old mystery of Puccinia striiformis life history solved with the identification of Berberis as an alternative host. Phytopathology 100: 432–435.

Liu, M., & S. Hambleton. 2010. Taxonomic study of stipe rust, Puccinia striiformis sensu lato, based on molecular and morphological evidence. Fungal Biology 114: 881–899.

Petersen, R. H. 1974. The rust fungus life cycle. Botanical Review 40 (4): 453–513.