Cyphophthalmids Wait for the Mountain to Come to Them

Carl Zimmer beat me to it. I was planning to announce the recent pettalid work after the paper arrived in the mail last week, but it seems I've been scooped. But because good work always deserves a second look, I'll write on it anyway. Besides, I was at least able to pinch the photo from Carl's site.

Pettalidae are a family of Cyphophthalmi, what are called the mite-like harvestmen. Cyphophthalmids are a fairly small group as far as is known, with probably less than fifty described species, but the number of species has been rapidly increasing in recent years. Though they are divided into about five families, cyphophthalmids are a fairly conservative bunch in appearance - the photo above is of Pettalus cf. cimiciformis*, but it is fairly typical of the group as a whole. They are quite distinct from other harvestmen (in fact, it is generally agreed that they are the sister-group to all others), and rather than having the spindly build of more familiar members of the order, cyphophthalmids are minute, stocky armoured tanks. If you look closely at the picture above, you may see a light spot on either side of the body that looks a bit like an eye, but it is in fact an ozophore - a raised mound bearing the opening of a stink gland. Except for members of the family Stylocellidae, cyphophthalmids have been described in the past as eyeless, but SEM studies of Pettalidae have revealed minute (often lens-less) eyes hidden on the side of the ozophore (Boyer & Giribet, 2007).

*For those who aren't already in the know, the 'cf.' in the name stands for the Latin confer (compare). In this case, it indicates that the animal in question is very similar to Pettalus cimiciformis, but is not definitely a member of that species.

The really interesting thing about cyphophthalmids (beyond their own intrinsic charm, of course) is their distribution patterns. Each of the various families has a definite, disjunct distribution (Boyer et al., 2007). The family Stylocellidae are restricted to south-east Asia. The Sironidae are found in what once was Laurasia - Eurasia and North America. The Neogoveidae are found in Florida, tropical South America and tropical West Africa - the tropical parts of what once was Gondwana. Two genera placed in their own families, Ogovea and Troglosiro, are found in West Africa and New Caledonia, respectively. And Pettalidae has a classic Gondwanan distribution, found in southern South America, southern Africa (including Madagascar), Sri Lanka, Australia and New Zealand (see Carl Zimmer's post for a map).

I think I should say something here about "Gondwanan" distributions. Science has a tendency to go through fads like any other aspect of human culture. For many years, most organisms showing what we would now call a "Gondwanan" distribution were interpreted as relicts of a former world-wide distribution. As acceptance of "continental drift" and recognition of the previous existence of Gondwana increased, more and more researchers considered its potential significance for modern biogeography. Needless to say, the significance was especially apparent to workers in the southern continents, doubtless not without some aspect of asserting the importance of the all-too-often neglected Southern Hemisphere biota relative to the Northern Hemisphere. Gondwanan origins became the next big thing for everything from birds (Cracraft, 2001) to beeches (Linder & Crisp, 1995) to butterflies (de Jong, 2003). In the last few years, the pendulum has begun to sway the other way, probably towards a more reasonable median.

The idea of a Gondwanan distribution for a given group of harvestmen particularly merits a critical look. The fossil record of harvestmen is pretty abysmal relative to the age of the group, but what record there is speaks of a remarkable degree of morphological conservatism. The Carboniferous long-legged harvestman Brigantibunum is almost indistinguishable from modern taxa (Dunlop & Anderson, 2005). The cyphophthalmid Siro platypedibus Dunlop & Giribet, 2003, from Bitterfeld amber (probably Oligocene or Miocene in age) is so similar to modern species that it is included in a modern genus.

In order to test whether the distribution of Pettalidae is an actual Gondwanan distribution as opposed to a relictual one, Boyer et al. (2007) tested the phylogeny of the family with just about every morphological and molecular method imaginable. They demonstrated that most of the cyphophthalmid families were monophyletic, with distribution matching phylogeny (the exception was the Laurasian Sironidae, which came out paraphyletic to the northern Gondwanan Neogoveidae and Stylocellidae).

To add another level of interest to the whole deal, most of the genera within Pettalidae each have separate geographic distributions (Boyer & Giribet, 2007). Chileogovea in South America, Purcellia and Parapurcellia in southern Africa, Pettalus in Sri Lanka, Karripurcellia in Western Australia, Austropurcellia in eastern Australia. The exception is New Zealand. New Zealand has a remarkable diversity of Pettalidae, with more described species than everywhere else combined, in three genera. But let's look a little closer. In the South Island of New Zealand, the genus Rakaia is concentrated in the east, while the genus Aoraki is found in the west from Mount Cook* north. New Zealand actually lies on the boundary between the Indo-Australian and Pacific plates, and if you were to map the distributions of the genera, you would see that Rakaia is mostly found on the Pacific plate, while Aoraki dominates on the Indo-Australian!**

*The Maori name for which just happens to be Aoraki. Not a coincidence - the genus was named after the mountain.

**I know, I said three genera. The third genus is a single species, Neopurcellia salmoni, in the southwest of the South Island.

REFERENCES

Boyer, S. L., R. M. Clouse, L. R. Benavides, P. Sharma, P. J. Schwendinger, I. Karunarathna & G. Giribet. 2007. Biogeography of the world: a case study from cyphophthalmid Opiliones, a globally distributed group of arachnids. Journal of Biogeography, in press.

Boyer, S. L., & G. Giribet. 2007. A new model Gondwanan taxon: systematics and biogeography of the harvestman family Pettalidae (Arachnida, Opiliones, Cyphophthalmi), with a taxonomic revision of genera from Australia and New Zealand. Cladistics 23: 337-361.

Cracraft, J. 2001. Avian evolution, Gondwana biogeography and the Cretaceous-Tertiary mass extinction event. Proceedings of the Royal Society of London Series B – Biological Sciences 268: 459-469.

Dunlop, J. A., & L. I. Anderson. 2005. A fossil harvestman (Arachnida, Opiliones) from the Mississippian of East Kirkton, Scotland. Journal of Arachnology 33: 482-489.

Dunlop, J. A., & G. Giribet. 2003. The first fossil cyphophthalmid (Arachnida, Opiliones) from Bitterfeld amber, Germany. Journal of Arachnology 31: 371-378.

Jong, R. de. 2003. Are there butterflies with Gondwanan ancestry in the Australian region? Invertebrate Systematics 17: 143-156.

Linder, H. P., & M. D. Crisp. 1995. Nothofagus and Pacific biogeography. Cladistics 11: 5-32.

(insert title here)

It seems I've fooled at least one person into thinking I have some sort of intellect - Kevin Z at The Other 95% has passed on the "Thinking Blogger" award to me. Apparently I'm supposed to pass it on to five more people, but this being something that has been going around for a little while, there's a shortage of people to pass it on to. There's no mention of dire things happening to my relatives if I don't pass it on like there normally is with chain letters, but I will highlight five other writers out there that have caught my attention lately (in no particular order). I'd also recommend heading to Kevin's site - it's well worth the trip, even if he is currently sobbing over his lophophorates.

Brian Switek of Laelaps has doubtless already received one of these, but he has a fantastic site for anyone with an interest in study of vertebrate palaeontology, and the study of the study of vertebrate palaeontology.

Also in the palaeontology field is Julia of The Ethical Palaeontologist. I'm not sure why she has tagged herself "ethical" (though as far as I can tell her ethics are impeccable), but she certainly writes some excellent posts.

Rick MacPherson of Malaria, Bedbugs, Sea Lice, and Sunsets writes his posts on the world of tropical marine biodiversity and conservation. Plenty of sea lice and sunsets - not so much malaria and bedbugs. Which is all good, because I know which two I would choose.

Cameron McCormick of The Lord Geekington is yet another fan of vertebrates, particularly cryptozoological specimens, who writes some very worthwhile, detailed posts.

Finally, Susannah of Wanderin' Weeta (with Waterfowl and Weeds) has a delightful site built mostly around her nature photography. Her recent sequence of spider baby posts have been wonderful.

Other things have happened here, too. I now have a face - I've finally gotten up to putting up a picture of myself. Pay no attention to it.

And my department has finally seen fit to change from Macs to PCs. At last, no more phaffing about with a *^&^%$# Mac! I'm free! Free! (I'm so happy.)

Taxon of This Week: Not All Violets are Violet

And in a double whammy for the day, I'll head straight into this week's highlight taxa, meaning the Dactylopodolidae (I can't help it - I love the name!) lose their seat faster than an Italian government. So let's welcome in the plant family Violaceae!

Violaceae are a medium-sized family (about 800 or more species), about half of which belong to the single genus Viola (violets, pansies and small string instruments) (shown in the image above from Wikipedia. Most Violaceae are herbs, but a few are woody shrubs, trees or lianes - for instance, the South American tree Leonia triandra reaches 25m in height (see here). In fact, I get the impression that, taken genus by genus, there are actually more woody genera of Violaceae than herbaceous ones, and it is only the high diversity of the mostly herbaceous Viola that skews the ratio. Phylogenetically Violaceae are members of the rosid order Malpighiales that I've had cause to mention before as containing the gigantic-flowered holoparasite Rafflesia.


Violaceae don't appear to include anything as remarkable as Rafflesia (at least as far as I know), but they are certainly not devoid of interest. Many species of Viola produce cleistogamous flowers, i. e. the flowers never open and fertilise themselves. Often (as in Viola pubescens, shown here in a picture from Wikipedia) both cleistogamous and open flowers are produced (Culley & Wolfe, 2001), thus achieving the best of both options - the greater genetic variability obtained through outcrossing, as opposed to the more guaranteed success in setting seed of cleistogamy.

Also worth a mention are the ten or so species of Viola endemic to Hawaii, which are unique among the genus in their combination of woody stems (present in a few other species) and flowers borne in inflorescences (as opposed to singly in all other Viola). [The picture at left from the Hawaiian Plants website of Gerald Carr shows Viola chamissoniana var. tracheliifolia.] These distinctive features have lead to the suggestion that the Hawaiian species are quite basal in the genus (possibly relicts) and that they are related to basal South American Viola species that also have woody stems. However, a molecular study by Ballard & Sytsma (2000) indicates that, far from being an ancient group, the Hawaiian violets represent a single quite recent colonisation, not from South America, but from the Arctic! The sister taxon of the Hawaiian violets is the herbaceous Viola langsdorffii, found in the American Arctic and Japan. As circumstantial support for this result, Ballard and Sytsma pointed out the large numbers of migratory birds passing Hawaii from their breeding grounds in the Arctic, and that at least two Hawaiian birds appear to have recent Arctic origins - the goose Branta sandvicensis (from B. canadensis and the duck Anas wyvilliana (from A. platyrhynchos).

REFERENCES

Ballard, H. E., Jr & K. J. Sytsma. 2000. Evolution and biogeography of the woody Hawaiian violets (Viola, Violaceae): Arctic origins, ancestry and bird dispersal. Evolution 54 (5): 1521-1532.

Culley, T. M., & A. D. Wolfe. 2001. Population genetic structure of the cleistogamous plant species Viola pubescens Aiton (Violaceae), as indicated by allozyme and ISSR molecular markers. Heredity 86 (5): 545-556.

Taxon of Last Week: I can't think of a clever title involving gastrotrichs

Once again, Taxon of the Week has been delayed. But don't worry, it's here now, and it's a doozie - or it would be, if I was actually able to find much information on it. This week we dive underwater and scrabble in the mud in search of the gatrotrich family Dactylopodolidae. [Just kind of rolls off the tongue, doesn't it?]

Gastrotrichs are minute (usually less than 1 mm) aquatic 'worms' that are one of those horribly obscure animal phyla that usually get allocated half a page in hidden corners of the textbooks, if they're lucky. They are inhabitants of the interstitial - they live among and between the grains of sand and mud, where they hunt down microscopic algae and protozoa by crawling about on their ciliated bellies. There are two distinct orders of gastrotrichs - the illustration above from Hochberg & Litvaitis (2000) shows an idealised representative from each. The animal of the right belongs to Chaetonotida, which have a fairly consistent bowling pin shape, covering of spined scales and two long posterior furcae each bearing a single adhesive tube. The more varied Macrodasyida, on the left, generally have a more elongated body shape and a greater number of adhesive tubes. The Macrodasyida are simultaneous or alternating hermaphrodites, while Chaetonotida have a higher diversity of reproductive strategies, including a number of parthenogenetic species. Macrodasyida are almost exclusively marine, with only a couple of exceptions; Chaetonotida are both marine and freshwater.

The Dactylopodolidae are members of the Macrodasyida. Phylogenetic studies using both morphological and molecular data agree that the Dactylopodolidae are the basalmost family of macrodasyids, which makes them potentially very significant for gastrotrich phylogeny (Hochberg & Litvaitis, 2000, 2001; Todaro et al., 2003). They seem to have a fairly generalised body-plan - no extravagant ornamentation, relatively short body with a deeply lobed posterior, while the adhesive tubes are generally restricted to the posterior part of the body (Hummon, 1974). Their basal position is indicated by a plesiomorphic musculature and monociliated epidermis (Hochberg & Litvaitis, 2001).



The Dactylopodolidae contains three to five genera (depending on whether or not the contentious genera Xenodasys and Chordodasys are included). The largest genus is Dactylopodola - the picture above comes from the Senckenberg Forschungsinstitut und Naturmuseum and shows Dactylopodola typhle - the linked site also has a close-up of its head that I recommend taking a look at. Get a good look - these appear to be the only images of Dactylopodolidae sensu stricto available on the web!

REFERENCES

Hochberg, R., & M. K. Litvaitis. 2000. Phylogeny of Gastrotricha: a morphology-based framework of gastrotrich relationships. Biological Bulletin 198 (2): 299-305.

Hochberg, R., & M. K. Litvaitis. 2001. Macrodasyida (Gastrotricha): a cladistic analysis of morphology. Invertebrate Biology 120 (2): 124-135.

Hummon, W. D. 1974. Some taxonomic revisions and nomenclatural notes concerning marine and brackish-water Gastrotricha. Transactions of the American Microscopical Society 93 (2): 194-205.

Todaro, M. A., D. T. Littlewood, M. Balsamo, E. A. Herniou, S. Cassinelli, G. Manicardi, A. Wirz & P. Tongiorgi. 2003. The interrelationships of the Gastrotricha using nuclear small rRNA subunit sequence data, with an interpretation based on morphology. Zoologischer Anzeiger 242 (2): 145-156.

Palaeos pages

For some time now, I've been contributing to Palaeos.org, the wiki site that was established last year to supplement Palaeos.com, and ideally to eventually supplant it when the original authors of Palaeos.com were no longer able to maintain it. Palaeos.com was originally founded as a site on palaeontology, but since then its mandate has expanded to cover all aspects of biology. It has gone offline on two occassions in the past - both times it has come back after overwhelming demand, and it was the latest disappearance that led to the foundation of Palaeos.org.

Palaeos.org is publicly editable, and I'd invite you all to take a look at it and add to it, correct errors, etc. as you may see fit. In particular, I'm going to start putting up notices on pages that I add to the site, in the hope that someone out there who knows more than I do may improve them. In recent times I've added pages on Combretaceae, Excavata, Eutrochozoa and Eoraptor. Tell me what you think!

More Really Ugly Fish

I've noted some examples before (in posts here and here) from the bizarre world of deep-sea fish, where life gets really ugly (because where there's no light and no-one can see you, you can really let yourself go). I thought I'd put in a mention of what are arguably among the most bizarre of deep-sea fishes, the Saccopharyngiformes. I can't recall when I first came across an illustration of these incredible creatures, but they're not something you readily forget (the image above comes from Animal Diversity Web).

Saccopharyngiformes are deep-sea 'eels'. They're not real eels (i.e. they're not members of the order Anguilliformes), but they are closely related and like true eels are members of the clade Elopomorpha. Elopomorphs are united by a distinct planktonic larval form called a leptocephalus, with a leaf-shaped transparent form shown below in a photo from Wikipedia. Admittedly, this photo shows a true eel rather than a saccopharyngiform eel, but the general idea's the same - except that saccopharyngiform leptocephali have the unique feature that the myomeres (the muscle blocks) are V-shaped instead of W-shaped. Saccopharyngiformes have greatly elongate jaws, attached to the neurocranium by only a single condyle. Most of the other uniting features of the order are absences - no scales, no pelvic fins, no ribs (see Fishbase for a complete list).



There are four families of Saccopharyngiformes. The most distinctive family is the bobtail snipe eels of the Cyematidae (image above of Cyema atrum from Animal Biodiversity Web again). Cyematidae are relatively small creatures with a distinctly cut-off appearance. Only two adult species are known, but apparently the known diversity of leptocephali attributable to this family suggests the existence of more. The long jaws bend away from each other and so can't be closed against each other - a feature shared by the unrelated but superficially similar true snipe eels of Nemichthyidae in the Anguilliformes.

The family Saccopharyngidae is the most familiar in the order (relatively speaking, of course), containing the gulper eels. Gulper eels can be extremely long, up to 2m in length, but the greater part of this (2/3 to 4/5 of the length) is taken up by the exceedingly long and filamentous tail. The remainder is dominated by the head - specifically the jaws - giving the appearance that these creatures are all mouth. How exactly that gigantic mouth is propelled by such a slender tail seems somewhat mysterious to me, and I'd love to know just how gulper eels spend their time. The tip of the tail bears an expanded, usually luminescent caudal organ - is has been suggested that this is used for a lure to attract prey, but without life observations this is mere speculation. Male gulpers have reduced jaws and an enlarged olfactory system relative to females. Eurypharynx pelecanoides, the pelican eel (the subject of the picture at the top of this post) is similar to the gulpers, but is separated as its own monotypic family. Eurypharynx has an even larger mouth than the Saccopharyngidae - over half the preanal length in the former as opposed to less than 40% in the latter.



The most bizarre of all the Saccopharyngiformes (and that's saying something) are undoubtedly the one-jawed eels of Monognathus, shown above in an image stolen from Smith (2002). Monognathus are the deepest-living of all elopomorphs, and have been found at depths of 5400m. The head is greatly reduced, and the common name refers to the complete absence of the upper jaw. A single venomous pronged fang sticks forward from the skull where the upper jaw should be - doubtless this is used to impale prey, but as Smith (2002) notes, " their odd morphology and their near total lack of sense organs make it difficult to imagine how they function and survive in their environment". Like other Saccopharyngiformes, Monognathus have a distensible abdomen, the posterior part of which oftens extends in a pouch that may go past the anus.

Though fourteen species of Monognathus have been described, only a single mature male specimen has ever been recovered. This specimen differed significantly from females. The lower jaw was almost absent, the fang was blunted, the olfactory organs were greatly enlarged, a layer of spongy tissue covered the head and the dorsal and anal fins were enlongated behing the tail into a notched fin. Obviously the males completely stop feeding on reaching maturity, and become totally dedicated to finding a mate. Their short life-span as a result probably explains why specimens are so rare.

REFERENCES

Smith, D. G. 2002. Families Cyematidae, Saccopharyngidae, Eurypharyngidae, Monognathidae. In: FAO Species Identification Guides for Fishery Purposes, The Living Marine Resources of the Western Central Atlantic, Vol. 2.

Sooglossidae: Deja vu all over again

Every couple of weeks or so I go into the Western Australian Museum library to look over the new journals and see if anything interesting has come out that I've missed. I did so this morning, and among the papers I noticed was van der Meijden et al. (2007) in the Biological Journal of the Linnean Society which established a new genus Leptosooglossus for the frog species previously known as Sooglossus gardineri from the Seychelles (shown above in an adorable image from the Nature Protection Trust of the Seychelles). A second species, Sooglossus pipilodryas, was also transferred into the new genus.

This was all well and good, until a few journals later I came across Nussbaum & Wu (2007) in Zoological Studies which established a new genus Sechellophryne for the frog species previously known as - yep, you know what's coming - Sooglossus gardineri (again, So. pipilodryas was also transferred). Oh dear. Two papers, published very close together in time, coining different names for the same thing.

Before anyone madly leaps to any suspicions, I can't find any obvious signs of plagiarism or claim-jumping in either paper. Both recognised the new genus on the basis of paraphyly of the genus Sooglossus, but van der Meijden et al. only used molecular data, while Nussbaum & Wu only used morphological data. It does seem somewhat incredible that there could be two separate groups of people both working on as small a group as Sooglossidae (only four species restricted to the Seychelles, a small group of islands in the Indian Ocean roughly the size of a postage stamp) and unaware of each other, but I can't find any obvious indications otherwise (if there is any sort of scandal, I'm chucking in a vote that it be referred to as 'Bubblegate'). It is good that the two papers using completely different methods agree so much in their results.

So the next question becomes - which is the correct name to use? The van der Meijden et al. paper was in the July issue of the journal it appeared in, while Nussbaum & Wu appeared in a May issue. So the first round would appear to favour Sechellophryne over Leptosooglossus. However, the cover date of a journal issue is not necessarily identical to the actual print release date, which is what is supposed to determine priority. The online release date for van der Meijden et al. (which may not be identical to the print release date, but is usually at least an indication) is given as 5th July at the journal website. Unfortunately, the website for Zoological Studies doesn't appear to list specific release dates, and there doesn't appear to be one on the paper. If anyone out there in the know is able to confirm the release date for me, I would be quite grateful (it suddenly occurs to me that I should have looked inside the cover or on the table of contents or such of the journal itself, but I'm no longer at the museum and can't do that now - d'oh!). Again, at the moment Sechellophryne appears to be the senior name unless proven otherwise.

Oh, and if you're wondering why Bubblegate, it's a reference to one of my partner's current favourite jokes (warning - PG rating):

Three frogs are brought before the court. As the first frog is taken to the stand, the judge asks the bailiff for his name and crime, to which the bailiff replies, "This is Frog, and his crime is blowing bubbles in the pond". The second frog is taken in, and again the judge asks for his name and crime. The bailiff replies, "This is Frog-Frog, and his crime is blowing bubbles in the pond". The third frog is then brought in, and the judge asks, "I suppose this is Frog-Frog-Frog?" "No," replies the bailiff, "this is Bubbles".

REFERENCES

Meijden, A. van der, R. Boistel, J. Gerlach, A. Ohler, M. Vences & A. Meyer. 2007. Molecular phylogenetic evidence for paraphyly of the genus Sooglossus, with the description of a new genus of Seychellean frogs. Biological Journal of the Linnean Society 91: 347-359.

Nussbaum, R. A., & S.-H. Wu. 2007. Morphological assessments and phylogenetic relationships of the Seychellean frogs of the family Sooglossidae (Amphibia: Anura). Zoological Studies 46 (3): 322-335.