Field of Science

Seriously, What Is This Thing?

So there weren't too many people speculating about the identity of that mysterious figure (hi, Adam!) As it happens, there was a reason I'd put it out there: the reason being, I really don't have any idea what it is either.

Spinita spp., from Kordè in Koren' (2003). 1: S. sanashticgolica, 2: S. cryptosa, 3: S. spinoglobosa.


The figure comes from a Russian book, Атлас ископаемой фауны и флоры палеозоя Республики Бурятия ('Atlas of the Palaeozoic fossil fauna and flora of the Republic of Buryatia'), edited by T. N. Koren' and published in 2003 in Ulan-Udè. Buryatia is a Russian republic in south-eastern Siberia, wrapping around the eastern and southern coasts of Lake Baikal. The fossils shown above come from the Lower Cambrian (the Botomian stage in the Russian system) of the Eastern Sayan Mountains. Going by the appearance of the figures, I presume they're being examined as thin sections, a commonly used method for studying Palaeozoic microfossils. Though as microfossils go, these are definitely on the large side: the specimen figured as 1a is a centimetre long and three millimetres wide. The other specimens are smaller, about half a centimetre in length.

When I saw these figures, I was just mystified. Their describer, K. B. Kordè, regarded them as a new class of 'Nemathelminthes', claiming that 'the first impression that is created from the described material is that they are representatives of the Kinorhyncha or Gastrotricha'. I'm not sure that I would agree with that. I found myself wondering if they were even animals, though I was hard pressed to think what else they might be. Not being familiar with the interpretation of thin sections, the thought did cross my mind to ask how certain can we be that these are even fossils, but I think that may be a bit uncharitable. Kordè also suggested that a break in the apparent cuticle of the S. sanashticgolica specimen about halfway along the flattened side (interpreted as the venter) might be the mouth. If so, that would be very unlike any kinorhynch or gastrotrich I've heard of. Could be a flatworm, I suppose, though Kordè then goes on to read the cluster of spines at one end (as magnified in figure 2b) as marking the anus which would seem to put paid to that! Said spines, or papillae, or whatever, are also supposed to have medial channels that Kordè interprets as nephridia.

All in all, I can't express anything other than confusion about this one. Certainly I haven't been able to find any further commentary on these enigmas; a Google search for Spinita sanashticgolica brings up just one result, an offhand mention in this book which seems to be just referring to it as found in the same formation as another fossil. Confusingly enough, that mention seems to date from 1986, a good seventeen years before Koren' (2003) was even printed: whether that indicates that the latter publication was not actually the first time the description of Spinita saw print, or whether this genus saw time floating around in unpublished communications, I have no idea.

Name the Bug Revived

It's been a very long time since I last did one of these, and I'm not sure if I still have the readership for it, but I'm genuinely interested to know what anyone can make of this (attribution to follow):


Some necessary context: they're fossils, Cambrian in age, I presume being examined in thin section. The specimens numbered 1, 2 and 3 were described as three different species of a single genus. Even if you don't know exactly what it is, let me know what you think it might be...

Edit: Forgot to give an indicator of size. They're about the one-centimetre range in maximum breadth.

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.

Cliff Ferns

Historically, the higher classification of ferns has tended to be a bit wobbly. Compared to flowering plants, ferns often offer fewer readily observable features that may offer clues to relationships. As a result, the position of many fern taxa has long been uncertain. One such group is the cliff ferns of the genus Woodsia.

Woodsia scopulina, copyright Jim Morefield.


Cliff ferns, as their name suggests, are commonly found growing on rocks. There are a few dozen species, mostly found in cooler regions of the Northern Hemisphere. A single species, Woodsia montevidensis, extends into South America and southern Africa (Rothfels et al. 2012). They have short creeping rhizomes with a covering of scales and leaves bearing a mixture of scales and hairs. The most distinctive feature of the cliff ferns can only be seen on fertile fronds: the sori (spore packets) are covered by an indusium that is attached to the leaf basally relative to the sori. These indusia are commonly composed of an array of scales or filamentous sections, in contrast to the solid indusia of other ferns.

Underside of pinnule of Woodsia plummerae, showing the filamentous indusia, from here.


Historically, Woodsia has been placed in a family Woodsia with a number of superficially similar fern genera such as the bladder ferns of the genus Cystopteris. However, molecular phylogenetic analyses have disputed the monophyly of such a group. Rothfels et al. (2012) divided the 'woodsioid' ferns between no less than six different families with Woodsiaceae in the strict sense limited to the cliff ferns alone. Though some authors have divided the cliff ferns between multiple genera, an analysis of the group by Shao et al. (2015) found it difficult to reliably distinguish such subgroups and recommended recognition of only a single genus. They did, however, recognise three major clades within Woodsia identified by molecular phylogenetic analysis as distinct subgenera. The type subgenus Woodsia is distinctive among ferns in possessing articulated stems; species of this subgenus are widespread in the Palaearctic region. The subgenus Physematium is mostly found in the Americas and is characterised by bicolored scales on the rhizome. The third subgenus, Cheilanthopsis, is found in eastern Asia with the centre of diversity in the Himalayan region. The rhizome scales are concolorous, and the indusia are solid and globose rather than being composed of individual segments. In some cases in this subgenus, the sori are covered by 'false indusia', indusium-like structures that are formed from inrolled leaf margins rather than being independent membranes.

REFERENCES

Rothfels, C. J., M. A. Sundue, L.-Y. Kuo, A. Larsson, M. Kato, E. Schuettpelz & K. M. Pryer. 2012. A revised family-level classification for eupolypod II ferns (Polypodiidae: Polypodiales). Taxon 61 (3): 515–533.

Shao, Y., R. Wei, X. Zhang & Q. Xiang. 2015. Molecular phylogeny of the cliff ferns (Woodsiaceae: Polypodiales) with a proposed infrageneric classification. PLoS One 10 (9): e0136318.

The Solemyoida: A Taste for Sulphur

Atlantic awning clam Solemya velum, copyright Guus Roeselers.


The small bivalves that make up the Solemyoida were long a mystery, ecology-wise. Though they have a long history, potentially going back as far as the Ordovician (Cope 2000), they are not known to have ever been diverse, and only just over fifty species are known from the modern fauna. Living solemyoids are divided between two very distinct families that probably diverged near the origin of the group. The Solemyidae, awning clams, have relatively long shells that gape at each end, no teeth in the dorsal hinge, and tend to have an unusually thick periostracum (the overlying layer of horny proteinaceous matter that covers the outside of the mineral shell). They generally live in burrows buried deep in sediment. The Nucinellidae are a group of minute clams with an average length of about half a centimetre that are mostly found in deep waters, generally not buried quite so deep in the mud as the awning clams. They have a less elongate shell than the Solemyidae that does not gape and simple peg-like teeth in the hinge. What the two families do share is a markedly reduced gut and feeding appendages that initially caused much speculation about what exactly they were feeding on.

Nucinella sp. with foot extended, from Taylor & Glover (2010). Scale bar equals 1 mm.


The answer, as it turns out, was that they were not exactly 'feeding' on much, if anything. Solemyoids have relatively large gills that provide a comfortable living place for sulphur-oxidising bacteria, sheltered from the outside world while the host clam keeps up a continuous flow of water through its burrow from above the sediment surface. In return, the bacteria fix hydrogen sulphide rising from the underlying mud to provide both themselves and their host with nutrients. In this way, solemyoids have largely been able to get by without actively eating for close to 450 million years, achieving something the likes of Jasmuheen can only dream of.

REFERENCE

Cope, J. C. W. 2000. A new look at early bivalve phylogeny. In: Harper, E. M., J. D. Taylor & J. A. Crame (eds) The Evolutionary Biology of the Bivalvia pp. 81–95. The Geological Society: London.

The Ageniellini: Nest Evolution in Spider Wasps

The Pompilidae, commonly known as spider wasps or spider hawks, are a distinctive and often conspicuous group of wasps, well known for their practice of capturing spiders and sealing them paralysed into nest cells to serve as food for their developing larvae. Though spider hawks come in a wide range of sizes and colours, I can say from experience that they are often a challenging group of animals to work with taxonomically. Their superficial diversity often masks a certain structural sameness that makes it hard to develop a reliable system for the family. Nevertheless, one subgroup of the pompilids that has long been recognised as distinct is the subject of today's post, the Ageniellini.

Female Ageniella arcuata carrying a lynx spider, copyright Edward Trammel.


Agniellins are generally smaller spider wasps whose distinguishing features include a more or less constricted base to the metasoma, forming a petiole. Females have a collection of relatively long, forward-directed setae on the prementum, a sclerite on the underside of the head that forms the rear margin of the mouthparts (you could think of it as the wasp's 'chin'). As befits their smaller size, they provision their nests with smaller and medium-sized spiders. As well as paralysing the spider with their sting in the usual way, ageniellins will also often remove its legs before sealing it into a cell, though Barthélémy & Pitts (2012) observed that this might not be done with small spiders. The Ageniellini have been further divided between two subtribes, the Ageniellina and Auplopodina. In Ageniellina, the premental setae are relatively fine and the end of the metasomal dorsum (the pygidium) in females is rounded and hairy. In Auplopodina, the premental setae are further modified into strong, thick bristles and the female pygidium is more or less flattened and smooth. However, the aformentioned characters of Ageniellina are primitive and shared with non-ageniellin spider wasps. A phylogenetic analysis of the Ageniellini by Shimizu et al. (2010) reinforced the suggestion that 'Ageniellina' might be paraphyletic with regard to the monophyletic Auplopodina.

Auplopus carbonarius, copyright Fritz Geller-Grimm.


Ageniellini are of particular interest among spider wasps for the variety of nesting behaviours they exhibit, which were reviewed in detail by Evans & Shimizu (1996). The primitive nesting behaviour for pompilids, shared by species of 'Ageniellina', is to dig nest cells in holes in the ground. 'Ageniellina' construct short holes from pre-existing openings in the soil such as caves, crevices or the burrows of animals. The holes are closed by patting down soil using the end of the metasoma. The origin of the Auplopodina, however, saw a seemingly small innovation that was to have significant consequences: the evolution of the ability to carry a small amount of water in the crop. Initially, this allowed the wasps to nest in firmer ground than was previously possible, using water to soften the soil before digging. Many Auplopodina species still nest in this fashion. They could also carry balls of mud under the head using the basket of premental bristles, using the mud to close up holes. Eventually, they started using mud to build barrel-shaped nest cells above ground, bypassing the need to dig, and/or closing up suitable pre-existing cavities such as hollow plant stems or abandoned cells from other wasps. The most basic mud cells are still vulnerable to damage from rain and water so are built in sheltered locations such as attached to plant rootlets protruding from overhanging banks. However, some Auplopodina species have learnt to cover the outside of the cell with a coating of resin to provide water resistance and so are able to build in more exposed places such as underneath plant branches or leaves. Species of one genus, Poecilagenia, are kleptoparasites, breaking into the nests of other pompilids and closing them back up after depositing their own eggs inside.

Macromerella honesta females on a communal nest, from Barthélémy & Pitts (2012).


The greatest advance in nesting behaviour known from a handful of Auplopodina species is the appearance of communal behaviour, potentially derived from multiple factors. The need for suitable sheltered sites for nest-building places a premium on location, increasing the likelihood of intra-specific encounters. The ability to break down and re-purpose pre-existing nest cells rather than building entirely from scratch makes it worthwhile for females to linger around their own place of hatching. In one eastern Asian species, Machaerothrix tsushimensis, dominance behaviour has been observed around nests with one female largely monopolising cell construction and provisioning while other females remain largely inactive, only constructing their own cells when the dominant female is elsewhere. In other communal Auplopodina species, females will share in the construction and guarding of nest cells.

True eusocial behaviour as found in vespid wasps and bees is unknown in pompilids. It has been suggested that their practice of provisioning brood cells only at the time of the construction, without providing subsequent meals, may be a hindrance to sociability as there is little incentive for females to provide for the larvae of other individuals. Nevertheless, the Ageniellini demonstrate that basic communality is not beyond the abilities of spider wasps.

REFERENCES

Barthélémy, C., & J. Pitts. 2012. Observations on the nesting behavior of two agenielline spider wasps (Hymenoptera, Pompilidae) in Hong Kong, China: Macromerella honesta (Smith) and an Auplopus species. Journal of Hymenoptera Research 28: 13–35.

Evans, H. E., & A. Shimizu. 1996. The evolution of nest building and communal nesting in Ageniellini (Insecta: Hymenoptera: Pompilidae). Journal of Natural History 30 (11): 1633–1648.

Shimizu, A., M. Wasbauer & Y. Takami. 2010. Phylogeny and the evolution of nesting behaviour in the tribe Ageniellini (Insecta: Hymenoptera: Pompilidae). Zoological Journal of the Linnean Society 160: 88–117.

Ants in Bright Velvet

A paper that I've been intermittently working on for a while now finally saw publication last week. Authored by myself, Mark Murphy, Yvette Hitchen and Denis Brothers, the paper describes four new species of velvet ant from here in Western Australia.

Female Aglaotilla chalcea, photographed by yours truly.


Velvet ants are not actually ants but a distinct group of typically hairy wasps forming the family Mutillidae. They are strongly sexually dimorphic: females are wingless like ants but males have fully developed wings. They develop as kleptoparasites in the nests of other wasps, with the velvet ant larva feeding on the prey left to provision the host and/or on the host larva itself. Taxonomically, velvet ants are perhaps one of the more difficult wasp groups to work with. The high sexual dimorphism means that it is often impossible to match males with females unless one is lucky enough to catch them in the act of mating, and the mesosoma of females is highly sclerotised and fused with many of the characters useful for identifying other wasp groups no longer visible. The taxonomy of Australian velvet ants is particularly uncertain, almost to comical levels. A large number of species (possibly numbering in the hundreds) remain undescribed, and many of those species that have been described are yet not readily identifiable. No extensive survey of the Australian fauna has appeared since 1898 and most Australian species have been placed in a single genus Ephutomorpha. This genus was established by French entomologist Ernest André in 1902 with a definition that can basically be summarised as "Ugh, I can't even right now": it was explicitly intended as a dumping ground for Australian velvet ants that André was unable to sort more appropriately at the time. A vague promise to get onto it later never eventuated. Even at its time of establishment, Ephutomorpha included taxa that had already been designated as type species for genus names Bothriomutilla and Eurymutilla that should have taken precedence.

A few years ago, I was engaged in identifying wasp specimens collected by Mark Murphy as part of his research into pollinator ecology in the Western Australian wheatbelt. For those of you unfamiliar with the area, the Wheatbelt refers to a band of land inland from Perth. Most of the wheatbelt is rolling, semi-arid terrain that has been cleared for the growth of the eponymous wheat, with the indigenous forest largely reduced to isolated stands and reserves. Mark was studying the diversity of pollinator wasps in these remnant stands, most of which are dominated by wandoo Eucalyptus wandoo. As an example of the difficulties I was referring to above, I was able to recognise over two dozen morphospecies of velvet ants among specimens collected by Mark, only a couple of which I was able to even tentatively connect to known species. The specimens which formed the basis of the new publication came from a particular one of Mark's study methods, nest traps. Mark would leave wooden blocks into which holes had been drilled out in the field for a number of months, over which time they would hopefully be colonised by nesting wasps and bees (Mark was visiting traps once a month to check for nests). The holes were lined with paper tubes and if Mark found one that contained a nest, he would slide out the tube and take it back to the lab to be reared to maturity. Emerging wasps and bees were identified to species both by morphological examination and via the extraction of DNA for fingerprinting. Mark also found that he reared a number of parasitoids and kleptoparasites that were treated in the same way.

The male of Aglaotilla chalcea, also by yours truly.


I realised that this gave us an excellent opportunity regarding the mutillids, of which four identifiable species had emerged from Mark's nest samples. Because of Mark's rearing experiments, we had host data for all four species. Because of the use of DNA fingerprinting, we were able to identify both males and females of three of the four species (the fourth was recorded from a single nest that only provided us with female specimens). And at least two of the species appeared to be completely new to science. It didn't hurt that they were also all very attractive animals with brilliant metallic colours. So I prepared a manuscript describing all four species with myself, Mark and Yvette (who had done the DNA sequencing for the specimens) as authors and submitted it to the journal Zootaxa for consideration.

It was rejected.

That, as it turned out, was a good thing. One of the original reviewers was Denis Brothers of the University of KwaZulu-Natal, one of the world's leading authorities on velvet ants. Denis agreed that, while the paper couldn't stand as originally submitted, there was a definite value in what we were presenting. So he offered to help us with the composition. As well as correcting some misunderstandings I was guilty of regarding mutillid morphology (see my earlier comment on the difficulty of identifying features of the female mesosoma), Denis was able to confirm that all four of our species was actually new. He also informed us that they could be placed in a group of species that he had identified as part of as-yet unpublished research on Australian velvet ants and suggested that we establish a new genus for this group. This new genus was named Aglaotilla by Brothers (2018). Denis also added a new section to our manuscript summarising the recorded host data for Australian mutillids.

Aglaotilla species are mostly metallic in coloration, predominantly blue, green or purple (describing the colours of metallic wasps can be a challenge because the exact shade observed depends a lot on the incident lighting). One of our species, A. micra, has the mesosoma reddish with a purple gloss whereas an earlier described species A. discolor has the mesosoma entirely red. Females often have prominent spots or bands of clustered white hairs on the metasoma. Depending on the species, the colour pattern of the sexes may be similar or distinct. One of our new species, A. lathronymphos, has a species name that means 'secretly married' because without the DNA fingerprinting we would have had no reason to associate the bright blue males with the reddish-purple females. Females lack the rake-like spines on the fore legs and flattened plate at the end of the metasoma found in many other female mutillids. This almost certainly relates to their life cycle. Female velvet ants parasitising ground-nesting hosts use their fore legs to dig into the host nest and the terminal plate to tap down the ground after closing it back up. Aglaotilla females, where known, parasitise hosts that nest above ground in holes in trees and so do not need adaptations for digging. Three of the species we described, A. chalcea, A. lathronymphos and A. micra, were reared from the nests of crabronid wasps belonging to the genus Pison. The fourth species, A. schadophaga, was reared from the nests of resin bees. Aglaotilla species are very unusual among velvet ants in that more than one larva may grow to maturity in a single host nest cell; in all other mutillids for which host data is available, only a single individual will ever emerge from a single host.

A likely live female of Aglaotilla in search of a suitable host nest, copyright Mark A. Newton.


The Australian mutillid fauna includes a number of enticing taxa that deserve further examination: the strikingly patterned Australotilla species and the weird ant-associated Ponerotilla are just a couple of examples. Not to mention the hordes of new species that don't even have names yet. I have been pleased to make some contribution to this much-neglected family.

REFERENCES

André, E. 1902 Hymenoptera. Fam. Mutillidae. Genera Insectorum 11: 1–77, 3 pls.

Brothers, D. J. 2018. Aglaotilla, a new genus of Australian Mutillidae (Hymenoptera) with metallic coloration. Zootaxa 4415 (2): 357–368.

Taylor, C. K., M. V. Murphy, Y. Hitchen & D. J. Brothers. 2019. Four new species of Australian velvet ants (Hymenoptera: Mutillidae, Aglaotilla) reared from bee and wasp nests, with a review of Australian mutillid host records. Zootaxa 4609 (2): 201–224.