Gonyleptids are Just So Cool

I was recently sent the following photos by Gabriel Whiting asking if I was able to supply an ID:





He had photographed this animal at Itatiaia in the province of Rio de Janeiro in Brazil. The photos don't give a direct indication of its size but Gabriel told me that it was quite big (at least for a bug) and you can see a couple of other insects in the wider photo for comparison.

It's obviously a harvestman of the South American family Gonyleptidae. A photo of a similar individual in Kury & Pinto-da-Rocha (2007) led me to identify Gabriel's mystery opilionid as Acutisoma unicolor (a paper currently in press will apparently shift its genus allocation to Goniosoma). According to Kury (2003), Itatiaia happens to be the type and (so far) only recorded locality for this species and information specifically relating to this species seems to be thin on the ground.

Casting the net wider, Acutisoma unicolor belongs to the subfamily Goniosomatinae which is endemic to the Brazilian coastal region (Kury & Pinto-da-Rocha, 2007). As large, readily visible animals, goniosomatines have been subject to a reasonable amount of study, particularly in regard to reproduction. Males of at least some goniosomatines may maintain territories in which they may guard harems of up to five females. Fights over territory may be long and fierce with the main appendages used being the long filiform legs II and the powerfully armed legs IV (Machado & Macías-Ordóñez, 2007). Most goniosomatines observed to date lay their batches on eggs in gaps between rocks or on the walls of caves. The eggs are generally looked after by the females though males have been recorded watching over eggs laid in their territory whose mother has temporarily gone elsewhere (Buzatto & Machado, 2009). Newly hatched juveniles may also remain clustered around the female.

REFERENCES

Buzatto, B., & G. Machado. 2009. Amphisexual care in Acutisoma proximum (Arachnida, Opiliones), a neotropical harvestman with exclusive maternal care. Insectes Sociaux 56 (1): 106-108.

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachida, Opiliones). Revista Ibérica de Aracnología, special monographic volume 1: 1-337.

Kury, A. B., & R. Pinto-da-Rocha. 2007. Gonyleptidae Sundevall, 1833. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds) pp. 196-203. Harvard University Press: Cambridge (Massachusetts) and London.

Machado, G., & R. Macías-Ordóñez. 2007. Reproduction. In Harvestmen: The Biology of Opiliones (R. Pinto-da-Rocha, G. Machado & G. Giribet, eds) pp. 414-454. Harvard University Press: Cambridge (Massachusetts) and London.

With Plate and Girdle (Taxon of the Week: Ischnochitonidae)

Some chitons are surprisingly colorful. This is Ischnochiton virgatus from southern Australia, as photographed by Leon Altoff.

In the familiarity stakes, chitons occupy the fourth spot among the generally-recognised mollusc classes after gastropods, bivalves and cephalopods (which is a little unfair as there are more living chiton than cephalopod species). All living chitons share a similar general morphology with a central linear series of eight overlapping shell valves, surrounded by a fleshy girdle that (depending on species) may or may not be covered with small spicules. Like limpets, chitons live attached to marine rocks where they graze on algae. Go down to any rocky beach and you'll have no difficulty finding them in large numbers.


A bright blue example of Lepidozona radians, photographed by Ron Wolf.

The classification of chitons has been shifted around a bit in recent years. Earlier systems seem to have been based primarily on the morphology of the shell valves but more recent classifications have also looked at other features such as the soft anatomy (the most commonly cited reference seems to be Sirenko, 2006, but unfortunately I don't have access to it at present). The family Ischnochitonidae as recognised by Kaas & Van Belle (1985, 1987), for instance, has been divided into a number of families; Sirenko's Ischnochitonidae appears to be roughly equivalent to Kaas & Van Belle's subfamily Ischnochitoninae. Phylogenetic studies indicate that Ischnochitonidae in the older sense is para- or polyphyletic (for instance, in the tree of Wilson et al., 2010).


Stenoplax conspicua is a large ischnochitonid, growing up to about ten centimetres long. Photo by J. P. McKenna.

Kaas & Van Belle (1985, 1987) distinguished the Ischnochitoninae from other chitons by the lack of comb-like projections on the insertion plates (lateral extensions of the valves that anchor the valve in the surrounding girdle), slits present on the insertion plates but not corresponding in number or position to the radial ribs of the valve, and with smooth, sharp teeth on the insertion plates that are not thickened at the edges of the slits. The girdle is covered with scales. Ischnochitonids can be found at all depths, from the shoreline to the deep sea - Stenosemus chiversi has been recorded at a depth of over 4500 m (Schwabe, 2008).

REFERENCES

Kaas, P., & R. A. Van Belle. 1985. Monograph of Living Chitons (Mollusca: Polyplacophora) vol. 2. Suborder Ischnochitonina. Ischnochitonidae: Schizoplacinae, Callochitoninae & Lepidochitoninae. E. J. Brill/Dr W. Backhuys.

Kaas, P., & R. A. Van Belle. 1987. Monograph of Living Chitons (Mollusca: Polyplacophora) vol. 3. Suborder Ischnochitonina. Ischnochitonidae: Chaetopleurinae, & Ischnochitoninae (pars). Additions to Vols 1 & 2. E. J. Brill/Dr W. Backhuys.

Schwabe, E. 2008. A summary of reports of abyssal and hadal Monoplacophora and Polyplacophora (Mollusca). Zootaxa 1866: 205-222.

Sirenko, B. I. 2006. New outlook on the system of chitons (Mollusca: Polyplacophora). Venus 65 (1-2): 27–49.

Wilson, N. G., G. W. Rouse & G. Giribet. 2010. Assessing the molluscan hypothesis Serialia (Monoplacophora + Polyplacophora) using novel molecular data. Molecular Phylogenetics and Evolution 54 (1): 187-193.

Name the Bug: Acanthastus luniewskii

Acanthastus luniewskii. Plate from Kozłowski (1948).

The five known species of Acanthastus were all described by Roman Kozłowski in his legendary 1949 monograph Les graptolithes et quelques nouveaux groupes d'animaux du Tremadoc de la Pologne which has done more than any other book to make me wish that I could read French. It was in this book that Kozłowski established the currently accepted relationship between the Palaeozoic graptolites and the recent pterobranchs (see this post here) based on his descriptions of early sessile graptolites from the early Ordovician of Poland. The Acanthastus remains were found in the same deposits, but establishing their affinities was just a little more difficult.

Acanthastus was represented by small flattened circular chitinous fossils (up to a few millimetres across) with a central dorsal opening surrounded by a ring of upwards-pointing spines. This central opening was crossed by tubes connected to the spines with a central cavity underlying this opening. Beneath and around this central cavity were a number of further chambers, divided by internal walls from the central cavity. The dorsal surface surrounding the central opening was roughened by a covering of small projections.


Diagram showing the internal structure of an idealised Acanthastus specimen, from Kozłowski (1949).

Kozłowski interpreted Acanthastus as a colonial animal, with each fossil representing a collection of individuals (presumably one in each chamber). I'm not entirely convinced by this - except for the central cavity, each of the chambers appears to have been entirely sealed off from the outside world, nor were the chambers connected in any way that would have allowed for the ready transfer of nutrients from the outside. But then, I've never been able to understand how on earth blastoids were able to survive either.

Because all the other taxa described by Kozłowski (1949) were graptolites or likely graptolite relatives, Acanthastus has always been associated with graptolites as well (for instance, appearing on a Wikipedia list of graptolite genera). However, Kozłowski himself was much less confident, noting that "Comme nous ne connaissons aucun organisme fossile ou vivant dont la morphologie ressemblerait à celle des Acanthastida il n'est pas possible de préciser actuellement leur position taxonomique" ("As we do not know any fossil or living organism whose morphology resembles that of Acanthastida it is not possible to currently define their taxonomic position"). After ruling out a relationship with coelenterates, bryozoans or tunicates, Kozłowski tentatively suggested that Acanthastus might be related to graptolites and pterobranchs by a vague similarity in skeletal structure, while admitting that its overall morphology was vastly different. His comment about relationships between Acanthastus and graptolites was that "Le plus qu'on pourrait admettre c'est que les Acanthastida appartiennent au même embranchement que ces derniers" ("The most one could admit is that Acanthastida belong to the same embranchement [phylum?] as the latter"), hardly a ringing endorsement. Unfortunately, no further study has been conducted on Acanthastus since Kozłowski (1949). I don't know how much of Kozłowski's original material still remains (see below), nor do any further specimens seem to have been recorded.

As well as being one of the most significant publications in the history of graptolite research, Kozłowski's 1949 monograph has to have one of the most dramatic publication histories. Though Kozłowski seems to have finished composing it in 1938, its publication was delayed for ten years by a small distraction known as World War II* (Kielan-Jaworowska & Urbanek, 1978). The Palaeontology department of the Warsaw University where Kozłowski worked was firebombed by the Germans in 1939 and all the material held in it destroyed. Some of Kozłowski's collection, as well as the monograph manuscript, was saved because it had been hidden in the basement of the Warsaw Seismological Observatory a few days before the destruction of the Palaeontology Department. When Kozłowski was able to return to the Observatory over a month later (German troops had been occupying it over that time), he found the place ransacked and all his material apparently lost. It wasn't until a few months later that he found his specimens and part of the manuscript among the ruins of the University, while a colleague found the remainder of the manuscript buried in a snowdrift.

In 1944, hundreds of thousands of Warsaw's inhabitants, including Kozłowski, were forced to flee the city. Again, the monograph manuscript was hidden, this time in the central heating pipes of Kozłowski's house. Kozłowski returned in 1945 to find the house ruined but the manuscript still safely hidden and waiting to be published. Also surviving the war intact were the negative for the monograph's plates which had been forwarded to Paris shortly before the war's beginning.

Which all kind of puts any problems you might have with reviewer delays into perspective, doesn't it?

*There's a fantastic story about British television and World War II. Television broadcasting was halted in Britain after the declaration of war. Supposedly, the first broadcast after the end of the war was introduced with the words "As we were saying before we were so rudely interrupted..."

REFERENCES

Kielan-Jaworowska, Z., & A. Urbanek. 1978. Dedication: Roman Kozłowski (1889-1977). Acta Palaeontologica Polonica 23 (4): 415-425.

Kozłowski, R. 1949. Les graptolithes et quelques nouveaux groupes d’animaux du Tremadoc de la Pologne. Palaeontologica Polonica 3: 1-235. (The publication itself is dated 1948, but all secondary sources seem to agree that it was actually published in 1949.)

Name the Bug 12

Diameter is 3.5 mm. Attribution to follow.

Update: Identity available here. Figure from Kozłowski (1949).

Caterpillars and their Capers (Taxon of the Week: Belenois)

The brown-veined white, Belenois aurota, of southern Africa. Photo from Bronberg Conservancy.

Belenois is a genus of about thirty species of butterfly of the family Pieridae found in tropical and subtropical regions of the Old World, with the greatest concentration of species in Africa. The caterpillars feed on plants of the caper family Capparaceae, though Moulds (1999) suggested that early records of 'cabbage whites' feeding on Brassica species in Australia prior to the confirmed introduction of any Pieris species might refer to Belenois java (the families Capparaceae and Brassicaceae are very closely related). Like most other pierids, Belenois species are medium-sized butterflies (the sole Australian species, B. java, has a wingspan of 55 mm - Braby 2000) with white or yellow background coloration patterned with black or brown on the wings. Individuals of a single species may vary in coloration patterns. Studies on B. java teutonia, which has distinct dark and pale forms, found that larval food species was one factor potentially affecting variation - caterpillars raised on Capparis umbonata always emerged from their pupae as dark form individuals, caterpillars from C. lasiantha were always pale, while caterpillars from C. spinosa could be either dark or pale (Braby, 2000).


The African veined white, Belenois glidica abyssinica. Photo by Johan van Rensburg.

Migratory habits have been recorded for a number of Belenois species, particularly B. java in Australia and B. aurota in southern Africa. Belenois aurota is one of the most abundant butterfly species within its range - one observer recorded witnessing a migration of about 500,000 individuals in Lesotho (Kopij 2006). A number of females will lay their eggs together in loose clusters on a suitable host plant. Braby (2000) notes that in some seasons a single tree may carry tens of thousands of eggs of B. java and the tree may end up being completely defoliated by the voracious caterpillars. Mortality among the caterpillars is high; only a few will reach adulthood.


The caper white, Belenois java teutonia, of Indonesia, New Guinea and Australia. Other subspecies of this species are found on islands of the Pacific. Photo by Peter Shanks.

REFERENCES

Braby, M. F. 2000. Butterflies of Australia: their identification, biology and distribution vol. 1. CSIRO Publishing: Collingwood (Australia).

Kopij, J. 2006. Lepidoptera fauna of Lesotho. Acta Zoologica Cracoviensia 49B (1-2): 137-180.

Moulds, M. S. 1999. The history of Australian butterfly research and collecting. In Biology of Australian Butterflies (R. L. Kitching et al., eds) pp. 1-24. CSIRO Publishing: Collingwood (Australia).

The Origin of Insect Wings

Photo by Daniel Oakley.

Flight has evolved among animals on four separate occassions - birds, bats, pterosaurs and winged insects - and much speculation has arisen about the circumstances of each. For only one of these clades, the birds, do we have access to a detailed fossil record demonstrating how their wings evolved; for each of the others we are still forced to rely on more indirect evidence. Winged insects are without doubt the most mysterious of the four. Vertebrate wings are instantly recognisable as modications of pre-existing forelimbs, but insect wings (at least at first glance) appear to have arisen de novo, without obvious homologues in any other arthropod group.

A long-popular hypothesis was that insect wings were derived from paranotal lobes - lateral extensions of the thorax, originally not articulated and probably used for gliding. Proposed support for the paranotal hypothesis came from the presence in a number of Palaeozoic insect groups of just such lateral projections, complete with wing-like venation, on the first segment of the thorax in addition to the actual wings on the second and third segments (contrary to many popular accounts, these insects were not 'six-winged', because the anterior lobes were fixed in place and not mobile like wings). Smaller projections in thysanurans (silverfish), the living sister group to winged insects, do allow them limited gliding ability, further supporting the proposal.


Reconstruction of the Permian insect Lemmatophora by F. M. Carpenter, showing the large 'wing-like' prothoracic lobes. Image via Oceans of Kansas.

During the latter part of the last century, however, an alternative hypothesis became prominent. Kukalová-Peck (1987 and other publications) pointed out that a major problem with the paranotal theory is that the insect wing articulation is not a simple structure. Insect wings are articulated by a set of small plates surrounding the junction of the wings and the thorax. In Kukalová-Peck's view, positing the development of this articulation completely de novo strained credulity. Instead, Kukalová-Peck proposed that the wings were derived from exites, lateral branches of the legs found in crustaceans. The fossil record of marine arthropods indicates that branched legs were part of the original arthropod ground-plan and many crustaceans that retain them show modifications of the exites into alternative structures. The gills of crabs and lobsters, for instance, are modified exites. According to Kukalová-Peck's proposal, exites present in the ancestral insects were moved into a dorsal position on the thorax to give rise to the wings. As the exites would have been articulated from the start, this removed the question of how the wing articulation developed. Kukalová-Peck proposed that the exites had originally been developed as gills in aquatic ancestral insects - the two basalmost living orders of winged insects, mayflies and dragonflies, are both aquatic as nymphs (as are the stoneflies, which Kukalová-Peck regarded as the next most basal order), and mayfly nymphs have winglet-like gills on the abdomen. It was suggested that the original gills could have been transformed into wings via their development as sails for skimming across the water surface (many living stoneflies use their wings in this way). To clinch the deal, Kukalová-Peck (1987) described a number of Carboniferous insect fossils retaining exites on their legs. Strong support for an exite origin of wings came from studies of Drosophila development - many of the same genes are expressed in the development of Drosophila wings and crustacean gills, while cells involved in wing development migrate dorsally from the leg primordia (Shubin et al., 1997). By the late 1990s, the exite theory had become generally accepted.


Figure of Gerarus danielsi specimen from Kukalová-Peck & Brauckmann (1992), as reproduced in Béthoux & Briggs (2008), showing exites attached to the legs.

However, the question was far from settled. The exite theory centred around an aquatic origin for winged insects, but this is doubtful. Successive sister-groups to winged insects (silverfish and archaeognathans) are terrestrial, as were the palaeodictyopteroids, one of the earliest groups of winged insects. Living winged insects other than mayflies and dragonflies form a clade called Neoptera that was probably also ancestrally terrestrial (most current researchers no longer regard stoneflies as basal among neopterans - e.g. Terry & Whiting, 2005). Adaptations to aquatic life in mayflies and dragonflies are very distinct, and the fossil and anatomical evidence suggests that these groups may have evolved aquatic nymphs independently. While fossils of winged insects are abundant by the Late Carboniferous, aquatic insects are not well-established in the fossil record until the Triassic nearly 100 million years later (Grimaldi & Engel, 2005), though a small number of aquatic nymphs have been claimed for the Permian - interpretation of these specimens is currently debated (Beckemayer & Hall, 2007). Though all the usual caveats around negative evidence still apply, the near or total absence of aquatic nymphs from Palaeozoic deposits contrasts strongly with their later abundance in Mesozoic and Cenozoic deposits, especially when one considers the presence of Carboniferous stem-dragonflies far larger than any later successor (such as the two-foot-plus-wingspan Meganeuropsis permiana) that might be expected to have had similarly robust nymphs.


Gliding ant Cephalotes atratus, by Alex Wild.

Also problematic is the complete absence of thoracic leg exites in any living insect, including archaeognathans and silverfish (Update: Günter Bechly has corrected me that thoracic exites are present in archaeognathans: see comments below). It is not impossible that winged insects, silverfish and archaeognathans could have each lost their exites independently. Exites have been lost by numerous arthropod groups and their corresponding absence in arachnids and myriapods (centipedes and millipedes) suggests that the loss of exites is somehow closely connected to adoption of a terrestrial lifestyle (I think terrestrial isopods still have them). Besides, any amount of recent absences should be instantly trumped by the fossil presences recorded by Kukalová-Peck (1987). However, not all authors have accepted Kukalová-Peck's interpretations. Béthoux & Briggs (2008) examined some of the specimens from which exites had been reported (including the stem-orthopteran Gerarus) and found that the supposed 'exites' were artefacts created by overenthusiastic specimen preparation. Whether any basal insect possessed exites therefore requires confirmation - it may be difficult to support derivation of wings from exites if no exites were present for them to be derived from. Unfortunately, many of the supposedly exite-bearing specimens described by Kukalová-Peck remain in private collections and are not readily available for re-examination.


Emerging mayflies, from here.

So of the currently contending explanations for the origin of insect wings, the genetic and developmental data seems to be consistent with an exite origin, but fossil and phylogenetic considerations appear more consistent with a paranotal origin. The challenge for researchers will be to reconcile this conflicting data. My personal suspicion is that some degree of genetic co-option is involved. Comparative studies on developmental genetics indicate that the evolution of new structures often involves the redeployment of pre-existing genetic pathways, and that separate lineages will often redeploy the same pathways. For instance, closely related genes are involved in the development of arthropod and vertebrate legs, despite the origins of both from legless ancestors (Shubin et al., 1997). Spider spinnerets appear developmentally homologous to abdominal legs, despite the loss of abdominal legs in arachnids a long time prior to the origin of spider spinnerets. It would be very interesting to see what the roles are in silverfish of the genes uniting insect wings and crustacean gills.

REFERENCES

Beckemeyer, R. J., & J. D. Hall. 2007. The entomofauna of the Lower Permian fossil insect beds of Kansas and Oklahoma, USA. African Invertebrates 48 (1): 23-39.

Béthoux, O., & D. E. G. Briggs. 2008. How Gerarus lost its head: stem-group Orthoptera and Paraneoptera revisited. Systematic Entomology 33 (3): 529-547.

Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.

Kukalová-Peck, J. 1987. New Carboniferous Diplura, Monura, and Thysanura, the hexapod ground plan, and the role of thoracic side lobes in the origin of wings (Insecta). Canadian Journal of Zoology 65: 2327-2345.

Shubin, N., C. Tabin & S. Carroll. 1997. Fossils, genes and the evolution of animal limbs. Nature 388: 639-648.

Name the Bug: Boreus

Boreus sp. Photo by A. Staudt.

Boreus is the main genus in the family Boreidae, a holometabolous insect family found in the northern parts of Eurasia and North America. Boreids are active during winter, when they are found among patches of moss on which they lay their eggs or on snow drifts between mossy rocks. Their apparent affinity for snow (the main source of moisture in the cold but dry habitats they prefer) together with their jumping movement gives them the common name of "snow fleas". Boreids also resemble fleas in effectively lacking wings - females lack them entirely, while males have the wings highly modified into a pair of large stiff hooks over the back (the individual in the photo above is a male). These hooks are, of course, useless for flying, but are used by the male in mating. As described by Cooper (1974): "An ardent male, when within some millimeters range, springs at the female, ensnaring her with his tong-like wings while seizing whatever he can of her extremities with one or both of his genital claspers". After the male's grip on the female has been secured (not always a simple process - see Cooper, 1974, for fuller details) and their genitalia have been conjoined, he may carry her about on his back in the mating position for several hours (the hook-wings are not actually used to hold the female while mating, only in the initial grab).

Most authors have included the Boreidae in the order Mecoptera, the scorpionflies. However, both molecular and morphological data have indicated that the Mecoptera as traditionally recognised are paraphyletic - from a phylogenetic perspective, the Siphonaptera (fleas) definitely and the Diptera (flies) possibly can be regarded as mecopterans. As a result, some authors have proposed restricting Mecoptera to a monophyletic core (the panorpoid families) and removing the families Boreidae and Nannochorista (a Gondwanan genus whose larvae are aquatic predators in streams of chironomid fly larvae) each to a separate monofamilial order. Both molecular and morphological data agree that the boreids are the sister group to the fleas (Grimaldi & Engel, 2005), making the name "snow flea" rather prescient. An alternative suggestion by Novokshonov (2002) that boreids are derived from the Palaeozoic family Permochoristidae is, as pointed out by Grimaldi & Engel (2005), rather weakened by the point that permochoristids are known only from isolated wings, making it somewhat difficult to understand how they could be compared to boreids and a relationship suggested in the first place.

REFERENCES

Cooper, K. W. 1974. Sexual biology, chromosomes, development, life history and parasites of Boreus, especially of B. notoperates, a southern Californian Boreus. II. (Mecoptera, Boreidae). Psyche 81: 84-120.

Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.

Novokshonov, V. G. 2002. Order Panorpida Latreille, 1802. The scorpionflies (=Mecaptera Packard, 1886, =Mecoptera Comstock et Comstock, 1895, +Neomecoptera Hinton, 1958, +Paratrichoptera Tillyard, 1919, +Paramecoptera Tillyard, 1919). In History of Insects (A. P. Rasnitsyn & D. L. J. Quicke, eds.) pp. 194-199. Kluwer Academic Publishers: Dordrecht.

Name the Bug # 11

What's this? Attribution to follow.

Update: Identification now available here. Photo by A. Staudt.

Taxon of the Week: Collonychium

Dorsal view of an unidentified Collonychium species. Photo by Abel & Ana.

Just a brief Taxon of the Week entry today because unfortunately I don't have a lot of info available on this taxon. The name Collonychium was recently revived from taxonomic limbo by Kury (2003) for two species of gonyleptid harvestmen found in south-east Brazil. Collonychium bicuspidatum is found in the provinces of Rio de Janeiro, São Paulo and Paraná while C. perlatum is found in Espírito Santo and Minas Gerais. Collonychium bicuspidatum had previously been included in the genus Paragonyleptes, of which it is the type species, before Kury (2003) recognised the type specimen of Collonychium bicuspidatum as a juvenile female of Paragonyleptes bicuspidatus (despite having the same species names, these two were originally described as separate species). A number of other southern Brazilian harvestman species had been assigned to Paragonyleptes, mostly by the famed creator of artificial classifications Carl-Friedrich Roewer and Cândido Firmino de Mello-Leitão (who, if anything, out-Roewered Roewer). These species were mostly listed by Kury (2003) as Gonyleptinae incertae sedis so they may or may not be Collonychium species.



I'm not entirely sure what's happening in this photo, again by Abel & Ana. Gonyleptids such as Collonychium have very powerful posterior-directed hindlegs, often with large spines pointing inwards on the retrolateral side (they're not as prominent in this individual, but in other species they may be very scary indeed). I think the individual in the photo above may be executing a handstand in order to bring the hindlegs into a better position to scissor with them at its intimidator (in this case, the photographer).

REFERENCE

Kury, A. B. 2003. Annotated catalogue of the Laniatores of the New World (Arachnida, Opiliones). Revista Ibérica de Aracnología, volumen especial monográfico 1: 1-337.

The Parrot of King Charles I

Yesterday, I asked people to identify this:



This specimen was originally illustrated in Frank Buckland's 1875 Log-book of a Fisherman and Zoologist. According to Buckland's account, he was presented with it by his servant while stationed at Windsor as an army surgeon, and told that the specimen had been found behind a chimney of the castle by some construction workers. One of the palace servants had then identified the skeleton as belonging to a favourite parrot of King Charles I.

Buckland confessed that, for a brief moment, the overall appearance of the specimen had him taken in. But it didn't take long for him to recognise it for what it was - the skeleton of a rabbit, cut in half with most of the thoracic skeleton removed, the neck and top part of the spine attached directly to the pelvis, and arranged in a position reminiscent of a bird. The construction workers and palace servants were themselves a complete fabrication. "King Charles I's parrot" became a favourite addition to Buckland's own collection.

Buckland himself was something of a character, a trait inherited from his equally eccentric father William Buckland (known as describer of one of the first known non-avian dinosaurs, Megalosaurus, and for his determination to eat a representative of every species of the animal kingdom). For more Bucklandery, you could start at his Wikipedia entry, while the Log-book is freely available from the Internet Archive at the link above.

Name the Bug: Sticholonche zanclea

Sticholonche zanclea (photo from here).

Sticholonche zanclea is a very unusual marine protist. In the past, it has been classified among the heliozoans, a group of organisms united by their generally radial arrangement of long cytoplasmic extensions called axopodia. However, both molecular and ultrastructural studies have established that the 'heliozoans' are a polyphyletic assemblage of a number of unrelated groups that have converged on a similar morphology. 'Heliozoans', in general, are passive trappers of other micro-organisms and food particles by means of their axopodia; the helizoan morphology provides for significant area coverage without massively increasing the cell cytoplasm. Compare this to the 'radiosa' form adopted by amoebae that become detached from their substrate and which serves a similar purpose (though in that case the aim is increasing the chance of recontacting the substrate). In the case of Sticholonche, molecular analysis has placed it among the also-axopod-bearing radiolarians with which it shares the production of siliceous spicules. Sticholonche differs from other radiolarians in lacking a central capsule dividing the cell into internal and external sectors; however, said molecular analyses place it nested among rather than sister to radiolarians. Indeed, it may be the sister to the spumellarid family Litheliidae (Kunimoto et al., 2006).

Sticholonche differs from other 'heliozoans' in being flattened with the axopodia concentrated laterally. The axopodia are rigid, reinforced by a central core of microtubules, and anchored on small cup-shaped depressions on the nuclear envelope (Cachon et al., 1977). By flexing the nuclear envelope, Sticholonche can move by rowing itself with the axopodia. If your day has so far provided insufficient awesomeness, follow this link, scroll down the page a bit, and you will find a video of a Sticholonche doing just that.

REFERENCES

Cachon, J., M. Cachon, L. G. Tilney & M. S. Tilney. 1977. Movements generated by interactions between the dense material at the ends of microtubules and non-actin-containing microfilaments in Sticholonche zanclea. Journal of Cell Biology 72: 314-338.

Kunimoto, Y., I. Sarashina, M. Iijima, K. Endo & K. Sashida. 2006. Molecular phylogeny of acantharian and polycystine radiolarians based on ribosomal DNA sequences, and some comparisons with data from the fossil record. European Journal of Protistology 42 (2): 143-153.

Name the bug # 10

I wonder if any of you are familiar with this animal:



Attribution to follow.

Update: Identification here. Image from Buckland (1875).

Name the Bug #9

I'm pretty sure you all know the drill by now. Attribution, as always, to follow.

Update: Identification now available here. Photo from here.

The Schizosphere (Taxon of the Week: Schizosphaerella)

Micrographs of Schizosphaerella from Perch-Nielsen (1989).

The dead are all around us. Large parts of the world's surface are made up by the remains of long-gone marine organisms who left their shells and skeletons, initially constructed for protection from predators and the elements, to form gigantic sedimentary graveyards. Over time, as with everything else, the identities of these unwitting benefactors have changed as new groups supplant the old.

During the Jurassic period, the predominant groups of biomineralising plankton were the calcareous coccoliths and Schizosphaerella (radiolarians were present but only important under certain conditions, planktic foraminiferans would not appear until the Cretaceous, while diatoms appeared in the Jurassic but remained marginalised until during the Cenozoic - Erba, 2004). Of these two, Schizosphaerella was particularly significant; at times, it accounted for nearly 100% of plankton-derived carbonate deposition (Mailliot et al., 2007). Schizosphaerella left its remains from the late Triassic to the end of the Jurassic in the form of globular to bell-shaped resting cysts, five to 30 μm in diameter, known as schizospheres. These are composed of two roughly hemispherical plates joined by a simple hinge. The two recognised species, S. punctulata and S. astraea, are distinguished by the presence or absence, respectively, of a subperipheral groove around the hinge and by the lattice arrangement of the elongate radiating elements that make up the wall (Perch-Nielsen, 1989). The nature of the Schizosphaerella organism during the active parts of its life cycle (assuming that the fossils are cysts) are unknown, as are its relationships to other organisms. The most common suggestion is that it represents some form of dinoflagellate - calcareous cysts are definitely produced by dinoflagellates of the subfamily Calciodinelloideae. However, Streng et al. (2004) have pointed out that the two-plated hinge arrangement of Schizosphaerella is unlike that known for any dinoflagellate, whose cysts normally open through an archeopyle at one end. That micropalaeontology is littered with examples of taxa of uncertain relationships (becoming more so the further back one goes in time) should come as no surprise to anyone - after all, it is often difficult enough to work out the relationships of modern unicellular organisms on morphological grounds, and doing so is often dependent on features of cell ultrastructure that are unlikely to be preserved in fossils.

Mention should also be made of the nannofossil Stomiosphaera minutissima which was described as having a calcareous cell wall of two layers - a thin inner layer and an outer layer composed of radiating fibres. 'Stomiosphaera' was shown by Aubry et al. (1988) to be the same as Schizosphaerella, but diagenetically altered (diagenesis is the process by which the nature of a fossil can be altered by geological processes after it gets deposited). The inner layer represented the two plates of the original fossil fused together while the outer layer resulted from crystal formation around the fossil.


Mean Schizosphaerella size over time compared to levels of carbonate production, from Mattioli et al. (2009).

Schizosphaerella seems to have preferred oligotrophic conditions with a deep nutricline (i.e. nutrients in the sea were spread out rather than being concentrated near the surface). An inverse relationship existed between Schizosphaerella and coccolith abundance (Cobianchi & Picotti, 2001) that was also related to the concentration of organic carbon in the water - high organic carbon (i.e. eutrophic conditions) meant more coccoliths and fewer schizospheres, low organic carbon the reverse. Periods of schizosphere abundance also relate to higher sea levels as reduced land level meant reduced organic run-off into the oceans. Both calcareous groups, however, showed reductions during periods of elevated CO₂ levels that punctuated the Mesozoic. The Toarcian anoxic event in the early Jurassic seems to have resulted from extensive vulcanism in southern Africa; the mean size of schizospheres becomes much smaller during this period as calcification became reduced by higher ocean acidity (Mattioli et al., 2009). This reduction in calcification is correlated with the extinction of a number of other organisms. Study of such past events is the best means available to us of understanding the effects that elevated carbon dioxide levels could potentially have in our own time (see, palaeontology can be practical too!).

REFERENCES

Aubry, M.-P., F. Depêche & T. Dufour. 1988. Stomiosphaera minutissima (Colom, 1935) from the Lias of Mallorca (Balearic Islands) and Umbria (Italy), and Schizosphaerella punctulata Deflandre & Dangeard, 1938: taxonomic revision. Geobios 21 (6): 709-727.

Cobianchi, M., & V. Picotti. 2001. Sedimentary and biological response to sea-level and palaeoceanographic changes of a Lower–Middle Jurassic Tethyan platform margin (Southern Alps, Italy). Palaeogeography, Palaeoclimatology, Palaeoecology 169 (3-4): 219-244.

Erba, E. 2004. Calcareous nannofossils and Mesozoic oceanic anoxic events. Marine Micropaleontology 52: 85-106.

Mailliot, S., S. Elmi, E. Mattioli & B. Pittet. 2007. Calcareous nannofossil assemblages across the Pliensbachian/Toarcian boundary at the Peniche section (Ponta do Trovão, Lusitanian Basin). Ciencias da Terra (UNL) 16: 1-13.

Mattioli, E., B. Pittet, L. Petitpierre & S. Mailliot. 2009. Dramatic decrease of pelagic carbonate production by nannoplankton across the Early Toarcian anoxic event (T-OAE). Global and Planetary Change 65 (3-4): 134-145.

Perch-Nielsen, K. 1989. Mesozoic calcareous nannofossils. In Plankton Stratigraphy vol. 1. Planktic foraminifera, calcareous nannofossils and calpionellids (H. M. Bolli, J. B. Saunders & K. Perch-Nielsen, eds) pp. 329-426. Cambridge University Press.

Streng, M., T. Hildebrand-Habel & H. Willems. 2004. A proposed classification of archeopyle types in calcareous dinoflagellate cysts. Journal of Paleontology 78 (3): 456-483.