Mosses: Not as Simple as You Think (Taxon of the Week: Ectropothecium)

Ectropothecium sandwichense, a moss species with a scattered, mostly tropical distribution on islands in the South Pacific. Photo from here.

I have to admit to becoming increasingly glad that I don't work on mosses. The new Taxon of the Week is a moss, and looking up stuff on it has driven me into a strange world of unfamiliar terminology and fine-scale features. If I mess anything up here, I only hope that the legions of moss fans out there* forgive my transgressions.

*Do not doubt that they're out there. As I've commented before, bryologists are a dedicated bunch.

Ectropothecium is a genus of mostly hydrophytic mosses found worldwide (hydrophytic plants grow either in water or in completely waterlogged soil; some Ectropothecium species do the former, others the latter). It belongs to a clade of mosses known as the pleurocarpous mosses; while other (acrocarpous) mosses branch only rarely and produce terminal archegonia (the female reproductive organs - see the diagram at the posts linked to above) at the end of the stem, pleurocarpous mosses produce lateral archegonia on highly branched and extensively interwoven stems (Shaw & Renzaglia, 2004). Pleurocarpous mosses are divided molecularly into three orders, Ptychomniales, Hookeriales and Hypnales; Ectropothecium belongs to the Hypnales which have a smooth spore capsule with a calyptra (protective cap) that usually opens by splitting along one side (Buck et al., 2004). Within the Hypnales, Ectropothecium is placed in the family Hypnaceae; however, phylogenetic studies of Hypnales (e.g. De Luna et al., 2000) suggest that members of the Hypnaceae may be para- or polyphyletically placed within the order.


Ectropothecium zollingeri, a species with a distribution centred in south-east Asia. Photo from here.

Ectropothecium itself is distinguished by having spore capsules that are very small (usually less than 1 mm long) and almost spherical (Buck & Tan, 2008), non-decurrent leaves (not extending down the stem where they join), short and broad leaf cells and filamentous pseudoparaphyllia that are two or three cells wide at the base (Ireland, 1992). Pseudoparaphyllia are small outgrowths of the stem that cluster around the base of new side-branches (as opposed to paraphyllia which are normally scattered more evenly along the entire stem); they may be thread- or blade-shaped. See Ignatov & Hedenäs (2007) for a review of the distinctions between paraphyllia, pseudoparaphyllia and proximal branch leaves, though to be honest if you understand the difference you're somewhat ahead of me (as far as I can tell, pseudoparaphyllia grow on the stem around the primordium of a new branch and remain on the stem, while proximal branch leaves may start growing around the primordium but end up being transferred to the new branch).

REFERENCES

Buck, W. R., C. J. Cox, A. J. Shaw & B. Goffinet. 2004. Ordinal relationships of pleurocarpous mosses, with special emphasis on the Hookeriales. Systematics and Biodiversity 2 (2): 121-145.

Buck, W. R., & B. C. Tan. 2008. A review of Elmeriobryum (Hypnaceae). Telopea 12 (2): 251-256.

De Luna, E., W. R. Buck, H. Akiyama, T. Arikawa, H. Tsubota, D. González, A. E. Newton & A. J. Shaw. 2000. Ordinal phylogeny within the hypnobryalean pleurocarpous mosses inferred from cladistic analyses of three chloroplast DNA sequence data sets: trnL-F, rps4, and rbcL. Bryologist 103 (2): 242-256.

Ignatov, M. S., & L. Hedenäs. 2007. Homologies of stem structures in pleurocarpous mosses, especially of pseudoparaphyllia and similar structures. In Pleurocarpous Mosses: systematics and evolution (A. E. Newton & R. Tangney, eds) pp. 227-245. The Systematics Association Special Volume Series 71. Taylor& Francis / CRC Press: Boca Raton.

Ireland, R. R. 1992. Studies of the genus Plagiothecium in Australasia. Bryologist 95 (2): 221-224.

Shaw, J., & K. Renzaglia. 2004. Phylogeny and diversification of bryophytes. American Journal of Botany 91 (10): 1557-1581.

Possibly The Coolest Thing I Had Published This Year

Dorsal view of male Australiscutum hunti (missing a few legs, I'll admit). Photo by yours truly.

In 1991, Hunt and Cokendolpher published a paper describing the new harvestman subfamily Ballarrinae and comparing to a selection of long-legged harvestmen from around the globe. In that paper, they referred to an undescribed species of the subfamily Monoscutinae from eastern Australia. For whatever reason, Glenn Hunt never completed a description of this new species before his death but I am happy to say that it has finally been brought into print by Taylor (2009) with the description of three species of the new genus Australiscutum.

Except for the minor detail that Australiscutum is not actually a monoscutine. Monoscutines are small harvestmen from New Zealand; despite belonging to the Phalangioidea, which are known as long-legged harvestmen, monoscutines have relatively short, robust legs. They also have the entire dorsal surface sclerotised (hence the name 'monoscutine' or 'single shield'; in most other phalangioids, only the prosoma or cephalothorax is sclerotised) and ornamented with small nodules. Australiscutum resembles monoscutines in having relatively short legs and while the dorsal surface of the opisthosoma (or abdomen) is not sclerotised, it is covered in small spine-like setae. However, in other features such as genital morphology Australiscutum is quite distinct from monoscutines. Shorter legs and hardened bodies have evolved in a number of different harvestman lineages, such as troguloids and various groups of Laniatores, and are probably an adaptation to a soil-dwelling lifestyle. Though it hadn't been run at the time I submitted this paper, my phylogenetic analysis of Monoscutidae (for which I'll probably be submitting the manuscript in a few days' time) corroborates the lack of a connection between Australiscutum and monoscutines and that the short-legged morphology has arisen twice within the family.

Neat as that is, though, that's not the really cool thing about Australiscutum. This is:



These are the chelicerae (the pincers) of males of the three species of Australiscutum as seen from the front and to roughly the same scale. Except for the appearance of the chelicerae, the differences between each of the species are relatively minor (though A. hunti is the most distinct of the three). Australiscutum hunti has large swollen chelicerae; A. graciliforceps has much smaller slender chelicerae. But when we reach A. triplodaemon, we see that it has one larger, more swollen chelicera and one smaller, more slender chelicera*. This cheliceral asymmetry is unique among monoscutids and, so far as I've been able to find, is unique among harvestmen. In fact, I haven't yet found any previous record of asymmetrical pincers like these for any arachnid.

*The species name of Australiscutum triplodaemon is a reference to the Triple Demons of Compromise in Norton Juster's The Phantom Tollbooth. Of these three, one demon was very tall and thin, the second was very short and fat, and the third one looked exactly like the other two.

So far, I can only make a few vague inferences about why A. triplodaemon has these uneven chelicerae, based on comparisons with asymmetrical pincers in crustaceans (where they are known in a number of different lineages). One thing I can say for sure that it is a true morphological feature and not a pathology. If a crustacean such as a crab or lobster looses a pincer while growing, the new claw that grows back may be smaller, but A. triplodaemon can be inferred to have naturally asymmetrical pincers because (a) it's always the left chelicera that is smaller, and (b) of the other two species in the genus, the one that is closest in appearance to A. triplodaemon (and hence the one that would represent its non-pathological form if it was a developmental accident) is the small-pincered A. graciliforceps and not the large-pincered A. hunti. Many crustaceans develop differently-sized pincers as an adaptation for handling food (for instance, they may use one pincer to hold a prey mollusc and they other to break open its shell) but, again, this seems unlikely to apply to A. triplodaemon as the asymmetrical chelicerae are only found in males. Female Australiscutum have small discrete chelicerae like other monoscutids; unless the females were eating a different diet from the males (not impossible, but unusual), we might expect both sexes to have asymmetrical chelicerae if they were related to food-processing.

The third role that has been recorded for asymmetrical pincers among crustaceans is as part of mating displays (fiddler crabs are the most famous example) and their presence in males only suggests that this is also they role they play for A. triplodaemon*. Determining just how A. triplodaemon uses its odd-shaped pincers will require observation of living specimens.

*Though I say that in the full knowledge that I am largely invoking the old line that "if you don't know what it's for, then it's for display".

I'd like to share one more interesting thing that came out of the review process for this paper. The two most similar species of Australiscutum, A. triplodaemon and A. graciliforceps, are in fact identical except for their chelicerae. Their recorded ranges also overlap, and the possibility occured to me when I was first describing them that they might be different male forms of a single species. Male dimorphism has been recognised in a number of harvestman species, including monoscutids, but because the mode of dimorphism in Australiscutum would differ from modes described previously I decided that the safest approach for now was to treat the two forms as separate species. I hemmed and hawed as to whether I should point out the possibility of their being dimorphs of a single species in the manuscript but eventually decided that it was perhaps too much speculation on my part and left it out (I tend to be fairly cautious in drawing inferrences; I've never been able to decide whether this is a good or bad thing). However, when I received the reviewers' comments, two of the three reviewers had thought of the same possibility without any prompting from me and suggested that I comment on it. So it's there.

REFERENCE

Taylor, C. 2009. Australiscutum, a new genus of Monoscutidae (Arachnida: Opiliones) from eastern Australia, with the first record of asymmetrical chelicerae in Opiliones. Insect Systematics and Evolution 40 (4): 319-332.

Insectivores: Possibility of Puggles (Taxon of the Week: Australosphenida)

A baby echidna or puggle. Normally, the puggle would be contained in a pouch on its mother's underside. Photo from here.

The Australosphenida is a group of mammals that has been studied fairly extensively in recent years, which is not bad going when one considers that, at most, less than twenty species have been assigned to it and some authors are of the opinion that the majority of those should not be regarded as australosphenidans at all.

The undoubted Australosphenida (or, more correctly if dealing with the restricted grouping, Ausktribosphenida) are five small Mesozoic insectivores (Rougier et al., 2007) - Asfaltomylos patagonicus and Henosferus molus from Jurassic South America, Ambondro mahabo from Jurassic Madagascar, and Ausktribosphenos nyktos and Bishops whitmorei from Cretaceous Australia. Despite their probably being fairly unprepossesing animals in life (as far as we can tell - so far, ausktribosphenids are only known from teeth and jaw bones), ausktribosphenids have provoked a fair amount of interest because of the resemblance between their teeth and those of modern marsupials and placentals. All three groups possess an arrangement called the tribosphenic molar, in which the lower molars each have a large posterior depression that contacts with a large cusp in the corresponding position on an upper molar, facilitating the grinding of food ("like a mortar and pestle", is the comparison that has been used in print).


Evolution of the tribosphenic molar as presented in Luo et al. (2001). Steropodon is an early monotreme; Northern Hemisphere tribosphenids are the clade marked "Boreosphenidans".

The discovery of tribosphenid mammals in Gondwana earlier than they had been found in northern continents (where they appear in the early Cretaceous) therefore led to the suggestion that tribosphenid mammals may have evolved in the Southern Hemisphere and only later spread to the North (modern marsupials, despite their current Southern Hemisphere distribution, were derived from Northern Hemisphere Mesozoic ancestors). However, further phylogenetic analyses lead to the alternative suggestion (Luo et al., 2001) that ausktribosphenids evolved the tribosphenic molar independently from Northern Hemisphere tribosphenids. Instead, Luo et al. (2001) placed ausktribosphenids as related to modern monotremes, which lack tribosphenid molars but share with ausktribosphenids a distinct shelf (the cingulum) around the front of the molars. This ausktribosphenid + monotreme grouping is what Luo et al. (2001) dubbed the Australosphenida. Later analyses (e.g. Rougier et al., 2007) make the 'ausktribosphenids' paraphyletic with regard to monotremes. Alternatively, some analyses have continued to support a monophyletic tribosphenid clade uniting ausktribosphenids, marsupials and placentals that excludes monotremes (Rowe et al., 2008). Things are not made easier by the point that, while ausktribosphenids are known from little else than teeth, known monotremes, both living and fossil, mostly have teeth that are vestigial, absent or just plain wierd (Kollikodon, I'm looking at you).


Kollikodon ritchiei. This Cretaceous monotreme had strangely rounded molars (it has been informally referred to as "Hotcrossbunodon") that may have been used for crushing molluscs. Or they may have been used for something else entirely.

Living monotremes are, of course, restricted to Australia, though it wasn't always so - Monotrematum sudamericum is a monotreme known from the Palaeocene of South America. Other known fossil genera are all Australian. I won't bore you with the things everybody already knows about monotremes - the presence of venomous ankle spurs in platypuses, the four-headed penis of echidnas, or the fact that baby echidnas (which are held in a pouch on the mother's underside) are known as puggles. Some things I will mention - if you've never seen a live echidna, they're a lot bigger than you think they are (I don't know how big you think they are, but I can assure you that they're bigger). According to Wikipedia, Tachyglossus aculeatus, the short-beaked echidna (the species found in mainland Australia), reaches about a foot and a half in length, while the New Guinean Zaglossus species are even bigger. The extinct mainland Australian species known as 'Zaglossus' hacketti (probably not a Zaglossus, but unrevised) would have been as large as a sheep. Echidnas when disturbed are able to dig with their fore-feet in such a way that they effectively sink into the ground while remaining horizontal, meaning that they retain full protection from their spines. In some areas (best known on Kangaroo Island in South Australia; see here) echidnas may form trains - shortly before a female becomes sexually receptive, a train of up to ten males will begin to follow her around in single file, waiting for her to give them the go-ahead*. Echidnas mate lying on their sides dug into a trench made by the male.

*If humans were to do this, it would be regarded as creepy. Echidnas don't seem to have this problem.

And in case you were wondering, I have been informed that the best way to deal with the spines when cooking an echidna is to roast it whole with the spines still on; after it's finished cooking, the spines can be pulled out fairly easily.

REFERENCES

Luo, Z.-X., R. L. Cifelli & Z. Kielan-Jaworowska. 2001. Dual origin of tribosphenic mammals. Nature 409: 53-57.

Rougier, G. W., A. G. Martinelli, A. M. Forasiepi & M. J. Novacek. 2007. New Jurassic mammals from Patagonia, Argentina: a reappraisal of australosphenidan morphology and interrelationships. American Museum Novitates 3566: 1-54.

Rowe, T., T. H. Rich, P. Vickers-Rich, M. Springer & M. O. Woodburne. 2008. The oldest platypus and its bearing on divergence timing of the platypus and echidna clades. Proceedings of the National Academy of Sciences of the USA 105 (4): 1238-1242.

Name the Bug #8: Prosobonia cancellata

Prosobonia cancellata - photo by Ron Hoff.

Prosobonia cancellata, the Tuamotu sandpiper, is a small to medium-sized bird found on a small number of coral atolls in French Polynesia. It is currently endangered with probably about 1200-1300 surviving individuals in 2003, mostly on the two islands of Tenararo and Morane (Pierce & Blanvillain, 2004). Zusi & Jehl (1970) included Prosobonia in the subfamily Tringinae, which also includes the Tringa sandpipers, Numenius (curlews) and Limosa (godwits). Prosobonia differs from these genera in living higher up on the shoreline, including the atoll forest, feeding on small invertebrates gleaned among leaf litter and off trees. They also seem to eat a reasonable amount of plant material such as seeds.

Other Prosobonia species were once found on a number of tropical Polynesian islands, while P. cancellata itself was previously more widespread with a range extending to Kiritimati (Christmas Island) in Kiribati. Some authors have regarded the Tuamotu and Kiritimati populations as separate subspecies or species, but Zusi and Jehl (1970) pointed out that the only known specimen from Kiritimati (unfortunately no longer available) probably lay within the known range of variation for Tuamotu specimens. Prosobonia leucoptera was found on Tahiti and Moorea (again, some authors have regarded the two populations as separate species) while undescribed subfossils have been found on Henderson, Marquesas and Cook Islands. Prosobonia cancellata has also been placed in a separate genus, Aechmorhynchus, from P. leucoptera, but again Zusi & Jehl established that significant differences between the two species were few except for coloration pattern (P. cancellata has barred plumage, while P. leucoptera was plainer) so there can be little doubt of their close relationship relative to other taxa.

REFERENCES

Pierce, R. J., & C. Blanvillain. 2004. Current status of the endangered Tuamotu sandpiper or titi Prosobonia cancellata and recommended actions for its recovery. Wader Study Group Bulletin 105: 93-100.

Zusi, R. L., & J. R. Jehl Jr. 1970. The systematic relationships of Aechmorhynchus, Prosobonia, and Phegornis (Charadriiformes; Charadrii). Auk 87: 760-780.

Name the Bug #8

Attribution, as always, to follow.

Update: Identity now available here. Photo by Ron Hoff.

Name the Bug # 7 - Apalopteron familiare hahasima

Apalopteron familiare hahasima - photo by Outsuka Hiroyuki.

Apalopteron familiare, the Bonin honeyeater, is a small bird of the Japanese Ogasawara (or Bonin) island group in the north-west Pacific. Phylogenetically speaking, it's been shuffled around a bit over the years - originally described as a species of bulbul, it seems to have been regarded by many authors as some sort of timaliid (babbler) until Deignan identified it in 1958 as belonging to the Meliphagidae (honeyeaters), mainly on the basis of its branched, brushed tongue. There it stayed until molecular analysis re-identified it as a member of the white-eyes (Driskell & Christidis, 2004). There are two funny things about this - (1) Apalopteron really does look like a white-eye (albeit a large one), so identifying it as one is hardly surprising; (2) further phylogenetic analysis has also placed the white-eyes (previously regarded as a separate family) within the Timaliidae (Gelang et al., 2009), making Apalopteron's older position correct after all.

The Ogasawara islands are arranged in three groups - from north to south, these are the Mukojima, Chichijima and Hahajima groups. Shima (which often becomes voiced to -jima when used in a compound) is Japanese for "island", while chichi is "father" and haha is "mother" (other islands in the group include ani and otōto [elder and younger brother] and ane and imōto [elder and younger sister]). Apalopteron familiare was originally found on all three groups, but currently survives only in the Hahajima group. As on many Pacific islands, the Ogasawara fauna has been pretty heavily hit since the arrival of humans due to habitat disturbal and introduced predators - among the endemic species to have become extinct in the group are a heron (Nycticorax crassirostris), pigeon (Columba versicolor), thrush (Turdus terrestris), finch (Chaunoproctus ferrugineus) and bat (Pipistrellus sturdeei) (Iwahashi, 1992). The type subspecies of Bonin honeyeater (Apalopteron familiare familiare) became extinct on Mukojima by the 1940s (Morioka & Sakane, 1978)*. Kawakami et al. (2008) found that dispersal between populations of Apalopteron on separate islands was very low, which would further increase its vulnerability.

*It is possible that a bit of revision may be required here. Suzuki & Morioka (2005) indicated that the type locality for Apalopteron familiare was probably Chichijima rather than Mukojima. Chichijima is considerably closer to Hahajima than it is to Mukojima, raising the question of whether the correct subspecies has been identified as the type.

REFERENCES

Driskell, A. C., & L. Christidis. 2004. Phylogeny and evolution of the Australo-Papuan honeyeaters (Passeriformes, Meliphagidae). Molecular Phylogenetics and Evolution 31 (3): 943-960.

Gelang, M., A. Cibois, E. Pasquet, U. Olsson, P. Alström & P. G. P. Ericson. 2009. Phylogeny of babblers (Aves, Passeriformes): major lineages, family limits and classification. Zoologica Scripta 38: 225-236.

Iwahashi, J. (ed.) 1992. Reddo Deeta Animaruzu: a pictorial of Japanese fauna facing extinction. JICC: Tokyo.

Kawakami, K., S. Harada, T. Suzuki & H. Higuchi. 2008. Genetic and morphological differences among populations of the Bonin Islands white-eye in Japan. Zoological Science 25 (9): 882-887.

Morioka, H., & T. Sakane. 1978. Observations on the ecology and behavior of Apalopteron familiare (Aves, Meliphagidae). Memoirs of the National Science Museum, Tokyo 11: 169-188, pl. 7-8.

Suzuki, T., & H. Morioka. 2005. Distribution and extinction of the Ogasawara Islands honeyeater Apalopteron familiare on Chichijima, Ogasawara Islands. Journal of the Yamashina Institute for Ornithology 37 (1): 45-49.

Conodonts: They Just Got Scarier

Reconstructed apparatus of Besselodus arcticus, from Dzik (1991).

I've told you before about conodonts, Palaeozoic microcarnivores with impressive tooth arrays. In the earlier post, I referred mostly to ozarkodinids, later conodonts that had grasping teeth in the front of their mouths and crushing plates towards the back. In this post, I'll be referring to panderodontids, an earlier group that lacked the crushing plates of ozarkodinids and had a tooth apparatus made up of simpler fang-like elements, similar to the reconstruction above. Apparatus of panderodontids have been found preserved in association, but we don't yet have preserved examples as good as available for the ozarkodinids.



With such different apparatus, panderodontids were obviously capturing and processing prey differently to ozarkodinids, and a paper just out by Szaniawski (2009) suggests one of those differences. Panderodontids and many other conodonts with coniform teeth had long grooves on the inner surface of some of their teeth (as seen in the photo of a Dapsilodus mutatus element above from Szaniawski, 2009) and Szaniawski points out that these grooves are extremely similar to those seen in the fangs of many venomous fish, lizards and snakes. He therefore infers that panderodontids were similarly venomous. As well as making conodont apparatus even more impressive than they already were, this would make panderodontids the earliest known venomous chordates*.

*Szaniawski refers to them as the "oldest known venomous animals". However, cnidarians had already been around for some time, and while the cnidarian venom delivery system doesn't fossilise, the fact that these were crown-group cnidarians makes it a pretty sure bet that they had it by then.

Earlier suggestions that the groove provided an anchoring point for muscles were couched in the belief that conodont elements were permanently internal, a view that is no longer standard*. Other forms of conodont lacked the venom groove, further evidence of the conodonts' ecological diversity.

*Conodont elements grew as new layers were put down over the outer surface, which is admittedly a little difficult to reconcile with their current interpretation as grasping teeth (which would require the absence of tissue cover). It seems likely that conodont teeth were only exposed when being actively used; at other times they would have been retracted into a covering pocket, in the same manner as the grasping spines of modern chaetognaths.

REFERENCES

Dzik, J. 1991. Evolution of oral apparatuses in the conodont chordates. Acta Palaeontologica Polonica 36 (3): 265-323.

Szaniawski, H. 2009. The earliest known venomous animals recognized among conodonts. Acta Palaeontologica Polonica 54 (4): 669-676.

Re-opening the Door (Taxon of the Week: Clausilioidea)

The latest Name the Bug challenge has been successfully identified as Apalopteron familiare, the Bonin honeyeater. I'll put up a descriptive post for that species in the next few days, but for now it's Taxon of the Week time.


A fantastic shot of the clausiliid Cochlodina laminata by Dietrich Meyer. The shell of this individual was 17 mm long.

The new Taxon of the Week is a repeat performance - Clausilioidea or door snails were featured here earlier this year and I'd recommend reading that post before this one. As mentioned there, one of the characteristic features of Clausiliidae (the family including all living clausilioids) is that they have very narrow, tall shells. Cain (1977) found that the distribution of shell shapes among terrestrial snails tended to be bimodal - shells were usually very long and thin or short and flatter, with very few being only slightly elongate. At least one factor in this difference in shell shapes appears to be choice of feeding territory* - elongate snails prefer grazing on very steep or vertical surfaces while shorter snails prefer more horizontal surfaces (Goodfriend, 1986). Studies on the behaviour of the clausiliid Cristataria genezarethana by Heller & Dolev (1994) found that they spent most of their lives sheltering in crevices - an individual snail would only be active for about six to twelve days of the year. Growth was estimated to be correspondingly slow - it may take eleven years for a Cristataria to reach maturity.

*In discussing possible reasons for the bimodality of shell shapes, Cain (1977) provided a very pithy summary of the problem in studying snail behaviour - "It is of course true that most species of snail when active are nocturnal or at least crepuscular, while conchologists are largely diurnal".


Congregation of aestivating individuals of the clausiliid snail Albinaria caerulea. This is one of the more widespread species of Albinaria, found in coastal western Turkey and the Cyclades islands of Greece, while an isolated population in Attica in Greece may have resulted from human transportation. Photo by Aydin Örstan.

Perhaps the most extensively studied clausiliid group is the Mediterranean genus Albinaria, found in southern Greece and Turkey. Albinaria shows a high level of apparent diversity - over 200 species and subspecies have been described. Many of these taxa occupy highly restricted distributions, and sympatry within the genus is rare. However, narrow hybrid zones exist between many "species", and they can often be interbred readily in the laboratory (Douris et al., 1998), leading to the suggestion that the number of true species involved may be much lower and that many supposed "species" may instead represent ecotypes. Comparable patterns of diversity are known from other land snail genera; one of the most notorious examples is the West Indian genus Cerion, the taxonomy of which was an early research topic of Stephen Jay Gould and a strong influence in the development of his opinions on developmental constraints and evolutionary contingencies. Molecular studies of Albinaria have supported the recognition of certain species, but failed to distinguish between others (Giokas, 2000). In some cases, two morphologically distinct "species" might form a clade together but remain intermixed within the clade, suggesting that they are indeed ecological variants of a single species.

REFERENCES

Cain, A. J. 1977. Variation in the spire index of some coiled gastropod shells, and its evolutionary significance. Philosophical Transactions of the Royal Society of London Series B - Biological Sciences 277 (956): 377-428.

Douris, V., R. A. D. Cameron, G. C. Rodakis & R. Lecanidou. 1998. Mitochondrial phylogeography of the land snail Albinaria in Crete: long-term geological and short-term vicariance effects. Evolution 52 (1): 116-125.

Giokas, S. 2000. Congruence and conflict in Albinaria (Gastropoda, Clausiliidae). A review of morphological and molecular phylogenetic approaches. Belg. J. Zool. 130 (Suppl. 1): 93-100.

Goodfriend, G. A. 1986. Variation in land-snail shell form and size and its causes: a review. Systematic Zoology 35 (2): 204-223.

Heller, J., & A. Dolev. 1994. Biology and population dynamics of a crevice-dwelling landsnail, Cristataria genezarethana (Clausiliidae). Journal of Molluscan Studies 60 (1): 33-46.

Hints for Name the Bug # 7

Yesterday's Name the Bug challenge is still sitting there without a successful identification, so here's some hints:

1. Phylogenetic wanderer, perhaps not so fond of honey after all.

2. Mama's still got it; Papa's lost it.

Name the Bug #7

After the last entry was obviously so difficult, I've decided to go a little easier on you all this time:



Attribution, as always, to follow.

Update: Identity now available here. Photo by Outsuka Hiroyuki.

Voice of the Iron Lady

Margaret Thatcher, bane of an entire generation of British liberals*, recently (Correction: not that recently, but in 1990) spoke at the 2nd World Climate Conference, and you can read a transcript of her speech online. Climate change isn't something I mention often at this site - it's really not my field of expertise. But I thought that I would like to share one excerpt with you:

Many of the precautionary actions that we need to take would be sensible in any event. It is sensible to improve energy efficiency and use energy prudently; it's sensible to develop alternative and sustainable and sensible ... it's sensible to improve energy efficiency and to develop alternative and sustainable sources of supply; it's sensible to replant the forests which we consume; it's sensible to re-examine industrial processes; it's sensible to tackle the problem of waste. I understand that the latest vogue is to call them ‘no regrets’ policies. Certainly we should have none in putting them into effect.

The thing that has always confused me about the climate change 'debate' is that I don't really see why there needs to be a debate in the first place. Ultimately, the best methods being proposed to combat climate change seem to come down to reducing pollution, and reducing waste. Irrespective of whether anthropogenic climate change is happening or not, these are good things in themselves. It strikes me as being a bit like the idea that bathing regularly reduces the likelihood that you will get sick. Maybe there's a chance that you won't become ill even if you don't wash yourself for a fortnight - but you would still feel better if you had, nonetheless.

*Does anyone else here remember The Tin-Pot Foreign General and the Old Iron Woman?

Soft yet Scaly (Taxon of the Week: Coccidae)

The stellate scale Vinsonia stellifera (Coccidae). Scales are insects that have abandoned motility for most of their lives to become sedentary plant suckers. Photo from here.

The truly bizarre insects known as scales have been covered at this site previously, including a brief description of the scale life cycle. In that post I referred to the ensign scales or Ortheziidae; in this post I'll cover the soft scales or Coccidae. The Coccidae include about 1000 species, some of which produce a dorsal covering of wax while others lack a dorsal covering (Williams, 1991). While ortheziids belong to the group of scale families known as archaeococcids, coccids belong to the more derived grouping known as neococcids. Neococcids are distinguished from archaeococcids by the absence of spiracles on the abdomen, and of compound eyes in the adult males (instead, male neococcid eyes have become reduced to dissociated ocelli). Coccids are distinguished from other neococcid families by the presence of a pair of rounded or triangular plates at the base of the anal cleft (Williams, 1991).


While female scales remain immotile for the rest of their lives once they have found a host, males regrow their legs and usually develop wings at maturity to find females. This is the Kuno scale Eulecanium kunoense. Photo by Joyce Gross (and very impressive it is too - photographing something as minute as a male scale would not be an easy call.

Another distinctive feature of neococcids is something referred to as Paternal Genome Loss (PGL - also known as Paternal Genome Elimination). In most neococcid families, males are technically diploid but early in development the chromosomes a male has inherited from its father are all inactivated so that it becomes functionally haploid. When the male produces sperm, these inactivated chromosomes are eliminated from sperm production and only the maternally-inherited chromosomes are passed on to its offspring. The reason for the evolution of PGL remains unknown*, but it appears likely to have evolved among neococcids on a single occasion (Yokogawa & Yahara, 2009). True haplodiploidy as found in Hymenoptera, where males are truly haploid as opposed to functionally haploid, has also evolved in scales of the archaeococcid family Margarodidae but is as yet unknown among neococcids despite suggestions that PGL may be a precursor to the origin of haplodiploidy. It is worth noting that, while an origin of haplodiploidy from PGL may seem reasonably intuitive, there is the small problem that there are more than twice as many known cases of taxa evolving haplodiploidy as PGL.

*Endosymbiotic bacteria such as Wolbachia have been shown to cause PGL in some insects (and the presence or absence of endosymbionts has been shown to affect PGL in at least one neococcid); alternatively, it could result from genetic factors on the animal's own X chromosome promoting the transmission of maternal chromosomes.

REFERENCES

Williams, D. J. 1991. Superfamily Coccoidea. In The Insects of Australia, 2nd ed. vol. I pp. 457-464. Melbourne University Press.

Yokogawa, T., & T. Yahara. 2009. Mitochondrial phylogeny certified PGL (Paternal Genome Loss) is of single origin and haplodiploidy sensu stricto (arrhenotoky) did not evolve from PGL in the scale insects (Hemiptera: Coccoidea). Genes Genet. Syst. 84: 57-66.

Name the Bug: Alaskiella medfraensis

Alaskiella medfraensis (from Frýda & Blodgett, 1998)

No-one successfully identified this one. I guess Palaeozoic gastropods just don't have the same following as other animals.

Alaskiella medfraensis is a member of the Porcellioidea, a superfamily of gastropods containing the Palaeozoic Porcelliidae and the Mesozoic Cirroidea. Porcellioids are distinguishable from other gastropods by virtue of being the only heterostrophic vetigastropods. I'll explain what that means, and I apologise in advance if it's a little hard to follow. I know it confuses the hell out me.

I've previously explained the difference between dextral and sinistral gastropods and how to distinguish the two. The method that I described therein is the correct one for orthostrophic shells. Orthostrophic growth is the standard gastropod growth pattern with the shell growing in a downwards spiral. However, some types of gastropod are hyperstrophic which essentially means that from a developmental perspective they grow upwards rather than downwards. Because the shell's "correct" orientation is therefore rotated 180° from that of an orthostrophic shell, if you hold a hyperstrophic shell with the aperture downwards a dextral shell is going to appear sinistral and vice versa. In life, of course, the aperture will still be held downwards in a hyperstrophic gastropod, but they can still be distinguished because the positions of the organs (gastropods are bilaterally asymmetrical) will be reversed - the stuff that you'd expect to see on the left side will instead be on the right. In the case of fossil gastropods, where you can't look at the organs, distinguishing hyperstrophic shells becomes a lot more difficult and I have to confess that I really don't see how they do it (apparently the shape and orientation of the aperture may offer some indications).

Heterostrophic shells like Alaskiella start off life growing upwards like a hyperstrophic shell but then change the direction of growth to downwards. As a result of this, they also change the direction of spiralling - so Alaskiella starts off spiralling upwards dextrally before it spirals downwards sinistrally. Among living gastropods, heterostrophic coiling is characteristic of the Heterobranchia, the clade that includes opisthobranchs (sea slugs and related animals) and pulmonates (lung-breathing snails). However, porcellioids developed heterostrophy independently of heterobranchs; instead, they belong to the Vetigastropoda, the clade including trochids (top shells) and turbinids (cat's-eye or turban shells). The main characters showing porcellioids to be vetigastropods are the presence of a vetigastropod-type protoconch (the embryonic shell) and nacre (the shiny inner layer of, for instance, a paua shell [Haliotis iris]; Frýda et al., 2008). Neither of these features is really visible in the figure above (nacre has only been identified as preserved in one cirrid genus so far) but you can readily see the large selenizone, the groove running around the outer edge of the whorls, which tends to be a characteristic of vetigastropods*. Porcellioids can also be distinguished from heterobranchs in that while heterobranchs change the direction of coiling at the transition point between the protoconch and the teleoconch (the post-embryonic or post-larval shell), porcellioids change directly during the early part of the teleoconch (Frýda & Blodgett, 2004).

*To be scrupulously correct, not all vetigastropods have a selenizone and not every gastropod with a selenizone (which may be a groove or may be a row of openings) is a vetigastropod. However, in general, non-vetigastropods with selenizones have only small ones.

Alaskiella medfraensis differs from other porcellioids in that other porcellioids have the axis of coiling of the protoconch parallel to that of the teleoconch, but Alaskiella has the axes offset at an angle. The change in the axis of coiling is what gives Alaskiella its characteristic looped look where the shell changes direction, which always puts me in mind of the looped peak that tends to form at the top of a meringue when you spoon it out.

REFERENCES

Frýda, J., & R. B. Blodgett. 1998. Two new cirroidean genera (Vetigastropoda, Archaeogastropoda) from the Emsian (late Early Devonian) of Alaska with notes on the early phylogeny of Cirroidea. Journal of Paleontology 72 (2): 265-273.

Frýda, J., & R. B. Blodgett. 2004. New Emsian (Late Early Devonian) gastropods from Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska (Farewell Terrane), and their paleobiogeographic affinities and evolutionary significance. Journal of Paleontology 78 (1): 111-132.

Frýda, J., R. B. Blodgett, A. C. Lenz & Š. Manda. 2008. New porcellioidean gastropods from Early Devonian of Royal Creek area, Yukon Territory, Canada, with notes on their early phylogeny. Journal of Paleontology 82 (3): 595-603.