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Portraits of amphisbaenians

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Portrait of Amphisbaena alba, by Darren Naish.

There have never been enough amphisbaenians on Tet Zoo. In fact, the only time I’ve written about them at any sort of length is in the 2008 (and 2012) April Fool’s article wherein they were convincingly (cough) shown to be the true ancestors of mammals. In reality, amphisbaenians – popularly called worm lizards – are highly specialized, subterranean squamates; that is, part of the same group of diapsid reptiles as lizards and snakes. The 140 or so living amphisbaenian species inhabit the tropical Americas, western Asia, Spain, Portugal and parts of Africa. Most (but not all) are limbless; they have reduced eyes and ears, a distinctly segmented body, and often a keeled or spade-like snout. The word amphisbaenian is pronounced something like ‘am-fis-bay-nee-an’.

I think I recall saying in one of my pygopodid articles (see links below) that among the earliest of reptile images to inspire a far younger Darren Naish were the remarkable and sometimes exceptional paintings produced by Alan Male for Philip Whitfield’s 1983 book Reptiles and Amphibians, one of my favourite childhood books (Whitfield 1983). Amphisbaenians get just a single page of illustrations therein, but among the six species illustrated we see… this (below): Male’s depiction of a Somali edge snout or Angled worm lizard Agamodon anguliceps. What the hell? If you’re interested in weird, obscure animals, this is an arresting image.

This is a -- reptile? Yes, yes it is. Agamodon anguliceps, illustrated by Alan Male (from Whitfield (1983)).

Agamodon is a trogonophid, or short-headed amphisbaenian, and it really isn’t easy to find good images of it, or indeed information on it. Indeed, there aren’t that many good places to go on amphisbaenians in general: they tend to get brief coverage in herpetology books, and you need to go to more technical sources if you want to know more. I recommend in particular the several reviews produced by the great Carl Gans (Gans 1969, 1974, 2000, 2005).

Bipes biporus, one of the several bipedid amphisbaenians, also called ajalotes. Image by Darren Naish.

Six ‘family-level’ amphisbaenian groups are presently recognized, and a very quick run-through of these groups will serve as a crash course in amphisbaenian diversity. Rhineurids, represented by Rhineura floridana from Florida, possess depressed, spade-shaped snouts and are the sister-group to remaining amphisbaenians in most studies (Conrad 2008, Vidal et al. 2008, Gauthier et al. 2012, Pyron et al. 2013). Several fossil rhineurids are known, the oldest of which (Plesiorhineura) is from the Paleocene. Bipedids – the one group that possesses limbs (and are exclusive to Mexico) – might be very closely related to blanids (Conrad 2008, Vidal et al. 2008), a group currently unique to the fringes of the Mediterranean but with fossil representatives known from the Eocene of England, France and Belgium. Cadea blanoides, a morphologically unexciting amphisbaenian from Cuba, has recently been identified as the sister-taxon to Blanus, raising interesting questions about amphisbaenian biogeography (Vidal et al. 2008). Cadea has been given its own ‘family’: Cadeidae.

Zarudny's worm lizard (Diplometopon zarudnyi) in profile, a trogonophid from the Arabian Peninsula. Image by Darren Naish.

Amphisbaenids (note: the terms ‘amphisbaenid’ and ‘amphisbaenian’ are not interchangeable) are present in both Africa and South America and include the majority of tropical amphisbaenians while trogonophids are the African and Middle Eastern short-headed amphisbaenians, all of which have formidable teeth fused to the edges of their jaws. Gauthier et al. (2012) named the amphisbaenid + trogonophid clade Afrobaenia. For a substantial review of amphisbaenian phylogeny and diversity see Kearney (2003).

Above: the very neat, short-faced, acrodont skull of the trogonophid Agamodon. Below: digging action used by Bipes. Both illustrations from Gans (1974).

The biology, behavior and functional morphology of amphisbaenians are areas of special interest and much has been written about them. All species are predatory, preying on arthropods, worms and small vertebrates. They catch animals in tunnels, often immobilising them by holding them against the side of the tunnel with a curve of the body. Some amphisbaenians, such as the large South American Amphisbaena species, take surprisingly large prey and regularly kill other reptiles as well as rodents. When hunting surface-dwelling prey, an amphisbaenian will lunge forward with its mouth open, grasping the prey with a powerful bite before dragging it underground. Alternatively, it might tear a chunk from the prey animal’s body, sometimes by powerfully twisting after initially grabbing hold. Amphisbaenians return to disabled or deceased prey and it has even been suggested that they may scavenge from dead bodies lying on the surface.

Exactly how amphisbaenians relate to other squamates has long been controversial. Several radically different hypotheses have been published, and so much could be said about this subject that I’m deliberately going to avoid it for now.

If you were hoping for a big and comprehensive review of amphisbaenian evolution, diversity and biology – sorry, this isn’t it. But I’ll come back to them in time, and at least Tet Zoo now has something more than parody about them.

Tet Zoo now features some fairly reasonable coverage of squamate diversity… but there is still so much to do…

Dibamids and amphisbaenians

Gekkotans

Lacertoids

Iguanians

Scincomorphs and cordyliforms

Anguimorphs

Snakes

Refs – -

Conrad, J. L. 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology. Bulletin of the American Museum of Natural History 310, 1-182.

Gans, C. 1969. Amphisbaenians – reptiles specialized for a burrowing existence. Endeavour, 28, 146-151.

- . 1974. Biomechanics: An Approach to Vertebrate Biology. Lippincott (Philadelphia).

- . 2000. Amphisbaenians. In Cogger, H. G., Gould, E., Forshaw, J., McKay, G. & Zweifel, R. G. (consultant eds) Encyclopedia of Animals: Mammals, Birds, Reptiles, Amphibians. Fog City Press (San Francisco), pp. 650-655.

- . 2005. Checklist and bibliography of the Amphisbaenia of the world. Bulletin of the American Museum of Natural History 289, 1-130.

Gauthier, J. A., Kearney, M., Maisano, J. A., Rieppel, O. & Behlke, A. D. B. 2012. Assembling the squamate tree of life: perspectives from the phenotype and the fossil record. Bulletin of the Peabody Museum of Natural History 53, 3-308.

Kearney, M. 2003. Systematics of the Amphisbaenia (Lepidosauria: Squamata) based on morphological evidence from Recent and fossil forms. Herpetological Monographs 17, 1-74.

Pyron, R. A., Burbrink, F. T. & Wiens, J. J. 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Evolutionary Biology 2013, 13:93 doi:10.1186/1471-2148-13-93

Vidal, N., Azvolinsky, A., Cruaud, C. & Hedges, S. B. 2008. Origin of tropical American burrowing reptiles by transatlantic rafting. Biology Letters 4, 115-118.

Whitfield, P. 1983. Reptiles and Amphibians: an Authoritative and Illustrated Guide. Longman, Harlow (UK).

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. DavidMarjanovic 9:19 am 04/26/2014

    Yay!

    I’ll just mention that, as the name Bipes suggests, bipedids lack hindlimbs despite their very well developped forelimbs. Must be an adaptation to forelimb-based digging…?

    Link to this
  2. 2. naishd 9:52 am 04/26/2014

    Yeah, I should have stated that (obvious) fact somewhere. The weird thing is that Bipes is nested within Amphisbaenia in just about all phylogenies: it is not the sister-group to all other amphisbaenians. Yet all other lineages lack forelimbs entirely (incidentally, Rhineura has internal relicts of hindlimbs).

    So — does this mean that the lineages that are equally old as or older than Bipes (rhineurids, Blanus and Cadea, at least) possessed forelimbs ancestrally but lost them independently, or that those of Bipes are ‘reacquired’? Let me check what Kearney said about this…

    Link to this
  3. 3. Cameron McCormick 3:06 pm 04/26/2014

    One of the Google Image results for Agamodon anguliceps is the photograph Alan Male apparently used as a reference. It’s a bit small but… well, the illustration appears to be totally faithful. Clearly we’re living in a strange, speculative universe.

    Link to this
  4. 4. irenedelse 5:20 pm 04/26/2014

    Browsing the list of TetZoo articles at the end, I’m impressed by the number and variety of amphibian and squamate groups that have evolved toward what is essentially a worm-like existence. Amphisbaenians, Caecilians, Slow-worms, Scolecophidian snakes, the Isopachys Skink… It’s happened time and time again.

    Link to this
  5. 5. ectodysplasin 7:29 pm 04/26/2014

    @irenedelse,

    Browsing the list of TetZoo articles at the end, I’m impressed by the number and variety of amphibian and squamate groups that have evolved toward what is essentially a worm-like existence. Amphisbaenians, Caecilians, Slow-worms, Scolecophidian snakes, the Isopachys Skink… It’s happened time and time again.

    A whole bunch of skinks have done this over and over again, actually. There are also dibamids, various alethinophidian snakes (erycines, xenopeltids, uropeltids, anomalochiliids, cylindrophiids, aniliids, etc.), and a bunch of other things, including some gymnophthalmids (e.g. Bachia) and a whole slew of fossil animals as well. This seems to be relatively restricted to reptiles, though, except for caecilians and a few select salamander species. What that means, who knows.

    Link to this
  6. 6. BilBy 10:18 pm 04/26/2014

    @irenedelse & @ectodysplasin: don’t forget Pygopodidae – Aprasia

    Link to this
  7. 7. Tayo Bethel 11:41 pm 04/26/2014

    Perhaps the evolutionary ability to reduce all of the limbs allowed squamates and caecilians to take advantage of the rich soil fauna in optimal habitats, and when those habitats degraded into more arid habitat the now limbless animals adapted. The closest that mammals have come to fully exploiting the soil fauna are probably talpid moles, and relatively few mammals seem to occupy this niche. Perhaps reptiles and some amphibians are more adept at this fossorial niche precisely because they could lose their limbs relatively easily.

    Link to this
  8. 8. vdinets 11:54 pm 04/26/2014

    Tayo: note that mammals have adapted to subterranean life at least nine times (true moles, golden moles, marsupial moles, African mole-rats, Eurasian mole-rats, zokors, mole-voles, tuco-tucos, pocket gophers, not to mention a few vole lineages and bamboo-rats apparently moving in the same direction), but they never even began to evolve worm-like shape. I don’t think it’s just the limbs thing. I would think the necessity to thermoregulate is keeping them compact, but naked mole-rats obviously don’t care much about thermoregulation. Perhaps they have some restrictions on spine length and flexibility, or maybe they need larger lungs due to higher metabolic rate?

    Link to this
  9. 9. DavidMarjanovic 6:26 am 04/27/2014

    This seems to be relatively restricted to reptiles, though

    To squamates even.

    Perhaps they have some restrictions on spine length and flexibility, or maybe they need larger lungs due to higher metabolic rate?

    Homeotic mutations increase the risk for cancer, which is a concern at mammalian metabolic – and therefore mutation – rates. This seems to be why only sloths and manatees get to play with the number of neck vertebrae, and why the total number of dorsal vertebrae shows rather little variation.

    (Birds simply don’t get cancer as easily as any other vertebrates, so suddenly having 23 neck vertebrae doesn’t matter. It’s not known why.)

    Link to this
  10. 10. naishd 7:04 am 04/27/2014

    The ‘number of cervical vertebrae is linked to cancer’ thing has been mentioned a few times here before. The paper concerned is…

    Galis, F. 1999. Why do almost all mammals have seven cervical vertebrae? Developmental constraints, Hox genes, and cancer. Journal of Experimental Zoology (Mol Dev Evol) 285, 19-26.

    Link to this
  11. 11. irenedelse 7:25 am 04/27/2014

    Homeotic mutations increase the risk for cancer, which is a concern at mammalian metabolic – and therefore mutation – rates.
    On that note, aren’t naked mole-rats (and some blind mole-rats) famous for their resistance to cancer? They seem to have various molecular mechanism to prevent it, in addition to their low metabolism. In their current way of life, they use their fore-limbs for digging underground in arid environments, but what’s to prevent them from adapting to a more snake-like or worm-like existence, if for instance some climate change brings more humid conditions?

    Link to this
  12. 12. Jerzy v. 3.0. 4:24 am 04/28/2014

    Bipes is nested within other amphisbaenians? Incredible. There is a potential here for really incredible genetic phenomenon – the evolutionary reversal of the whole limb formation. The only comparable cases I know are anurans re-evolving teeth on the upper mandible and phasmids where different lineages lose and reevolve wings.

    Re: why salamanders and squamates easily evolve leglessness: I think it was answered by Darren indirectly (or directly?) some posts ago. Wriggling mode of walking means that propulsion is geenrated by muscles in the abdomen and tail pressing to the ground. Legs are mostly anchors and stabilizers. Species living in leaf litter or underground have no benefit of legs, which only block the smooth movement. Mammals walk and dig by moving limbs, so the evolution repeatedly produced shovel-like forelimbs.

    Link to this
  13. 13. naishd 4:30 am 04/28/2014

    On amphisbaenians and limbs (follow-up to comments # 2 and 12)– I’m sure I’ve read that Rhineura has hindlimb remnants, but Kearney (2003) says that only Bipes and Blanus have them. Anyway, yes, the majority of cladograms show Bipes to be nested well within an otherwise limbless clade, making limb reacquisition the most parsimonious idea. This might be afforded supported by the unusually far anterior position of the forelimbs and pectoral girdle in Bipes.

    Link to this
  14. 14. John Scanlon FCD 10:08 am 04/28/2014

    …tear a chunk from the prey animal’s body, sometimes by powerfully twisting after initially grabbing hold. Amphisbaenians return to disabled or deceased prey and it has even been suggested that they may scavenge from dead bodies lying on the surface.
    Land-lampreys, anyone? Is there a world in which hordes of amphisbaenians cooperatively ambush large prey along migration routes? Already happens in the Squamozoic?

    Squamate limb reduction is so overwhelmingly prevalent in fossorial groups that proposing re-evolution of functional limbs on the grounds of ‘parsimony’ demands better evidence than we have for this group. I’d consider it far more likely (and really more parsimonious, except in a Wagner sense) that something like the Bipes groundplan was ancestral, with loss of forelimbs three or more times, than that such a state evolved from a head-first burrower with small, draggy forelimbs (or none). This despite the peculiar hand anatomy of Bipes, which iirc has a unique phalangeal formula that puts some doubt on homology with the normal five digits. (Similarly, I don’t think any snakes re-evolved hindlimbs with knees and digits after once losing them.)

    Link to this
  15. 15. naishd 11:06 am 04/28/2014

    Well, there is the suggestion that the Squamozoic should be inhabited by ‘land-candirus’: limbless, subterranean parasites that burrow into the tissues of large animals as they recline against the substrate. The offending comment is here.

    Link to this
  16. 16. Halbred 12:02 pm 04/28/2014

    How big are these animals? If they’re going after rodents, they must be larger than, say, caecilians..?

    Link to this
  17. 17. Yodelling Cyclist 12:07 pm 04/28/2014

    Congrats on finishing off placoderms, btw.

    Link to this
  18. 18. irenedelse 12:14 pm 04/28/2014

    @ John Scanlon FCD:

    The lunging and tearing of flesh, coming back to an injured prey, scavenging, attacking bigger animals: this brings to mind the behaviour of another squamate, the Komodo dragon.

    Link to this
  19. 19. irenedelse 2:20 pm 04/28/2014

    @ Hallbred: Even big species don’t seem to get more ‘than a foot long. But since amphisbaenians don’t need to swallow their prey whole, like snakes, but can bite off chunks, I can see one taking on something like a mice.

    Link to this
  20. 20. ectodysplasin 6:14 pm 04/28/2014

    @Darren,

    ‘land-candirus’

    “Landiru”

    Link to this
  21. 21. naishd 6:23 pm 04/28/2014

    You heard it here first :)

    Link to this
  22. 22. irenedelse 4:35 am 04/29/2014

    Land-candirus, or land screw-worms (Cochliomyia hominivorax)? Maybe in the Squamozoic, there are small amphisbaenians who evolved a parasitic life-cycle: not only do they burrow in the flesh of big animals when they recline on the ground, but they lay eggs (or maybe give birth to live young) in the wounds thus made! The babies grow fast on this diet of warm, juicy flesh, and just drop to the ground when they reach adult size, choosing for doing so a spot of sand or mud or leaf litter. They then lie in wait for another unsuspecting host to come along…

    Hey, as long as we making up scary animals, why stop at vertebrates? ;-)

    Link to this
  23. 23. naishd 5:00 am 04/29/2014

    Another paper has just appeared on the points made above about cervical ribs in some tetrapods…

    Reumer, J. W., ten Broek, C. M., & Galis, F. 2014. Extraordinary incidence of cervical ribs indicates vulnerable condition in Late Pleistocene mammoths. PeerJ 2:e318 http://dx.doi.org/10.7717/peerj.318

    Link to this
  24. 24. DavidMarjanovic 10:05 am 04/29/2014

    Maybe in the Squamozoic, there are small amphisbaenians who evolved a parasitic life-cycle:

    As long as they can breathe…

    Link to this
  25. 25. Jerzy v. 3.0. 10:47 am 04/29/2014

    On the subject of parasitic amphisbaenians, I took time to develop more of these interesting creatures:

    LAND CANDIRUS (CANDIROPHIDAE)

    These may be the most unjustly vilified of all Squamozoic animals. In fact, most of 75 known species of these small, burrowing snakes and are harmless or beneficial. They feed on soil invertebrates around dung or carrion of large animals. They are attracted to the scent of dung and vibrations, which was probably the first adaptation of land-candirus. They have ability to feed on carrion and dung itself, too. When they locate a carcass of large animal, stem candirus make most of this short-living, superabundant food supply. They begin to breed at incredible rate, producing a clutch of eggs every five days, which hatch and reach sequal maturity within the next three weeks. Land-candirus can also reproduce parthenogenetically. Several other candirophidini live in burrows of large animals, and are beneficial, feeding on parasitic insects. When they encounter dead eggs, juveniles, or food remains, they will consume these, too. There are reports, that they will also lick the blood or fluid from open wounds.

    These adaptations peaked in the best known, proper Land Candirus (3 species, common, hairy-legged and white-winged). These small burrowing snakes are highly attracted to vibrations and smell produced by large animals. They not only crawl, but can move inchworm-like over the ground. Upon locating a host, a land-candiru secretes a glue-like fluid from anal glands, allowing it to stick and crawl over a host body. When it locates an area of thin skin, or prefarably a wound, it secretes an anestetic-containing saliva and burrows under the skin. For the next months, the land candiru feeds on the host fat and partially muscle tissues. It periodically sticks abdomen through the wound hole and drops a litter of live babies to the ground. In most cases, host scratching or commensal birds eventually kill the candiru.

    The most developed species, the Common Land-candiru (Candirophis rotundus) can tolerate low oxygen and breed parthogenetically inside a host. In rare cases, this results in a host dying, after which a swarm of young land-candirus emerges from the orifices of the body, leaving behind little more than a skeleton surrounded by a bag of skin. It must be stressed, that this occurs mostly in weak or sick prey, and human casualties are rare, with almost no major outbreaks. Similar convergent family of False Land-Candirus are amphisbaenids, occuring in the Old World tropics…

    Link to this
  26. 26. naishd 11:00 am 04/29/2014

    Nice work, Jerzy… do I have your permission to absorb these creatures into the Squamozoic universe? As for the details discussed here, did you ever read about the non-parasitic pugnose eels that were found living inside the heart of a shark? They got in there… somehow, and survived.

    Caira, J., Benz, G., Borucinska, J. & Kohler, N. 1997. Pugnose eels, Simenchelys parasiticus (Synaphobranchidae) from the heart of a shortfin mako, Isurus oxyrinchus (Lamnidae). Environmental Biology of Fishes 49, 139-144.

    Link to this
  27. 27. Jerzy v. 3.0. 6:00 pm 04/29/2014

    No problem, Darren. Thankf for the pugnose eel ;)

    I am sure you will not forget candiru snakes soon. But I tried to make them sort of complete neat little horror. So don’t read below if easily disturbed, for there is a big yuck-factor:

    A research was made on behaviour of Candirophis inside the host. Candiru snakes, like larvae of some parasitic insects, initially avoid important internal organs, feeding on fat and connective tissue, gonads, eyeballs etc. The cue is apparently low blood flow to the organs. When host body movements cease, this triggers the second phase, where the parasites rapidly consume all other soft tissue besides bones and skin. Observers claim to hear subtle clicking sounds, apparently made by parasites biting into joint sockets. The second phase is competitive, because first parasites to emerge burrow in the soil immediately near the host body, and subsequent ones are forced to migrate further and further away. Most of them are eaten by small predators or die, fortunately for Squamozoic travellers. After about half an hour, there is coordinated mass emergence of candiru snakes from all the host orifices. According to eyewitnesses, especially thick stream of candiru snakes evacuate the braincase through the eye sockets…

    Link to this
  28. 28. irenedelse 7:12 pm 04/29/2014

    Jerzy:
    Squamozoic researchers should be careful when examining carcasses or animals potentially infested by Candirophids. They seem to easily crawl from one host to another. There are reports of hunters unwittingly acquiring one or more of these tiny parasites while skinning an otherwise healthy looking animal. In regions where the parasitic species are endemic, predators and scavenging animals often become themselves hosts to candiru snakes through eating from the carcasses. The snake either crawls on the predator’s head and starts burrowing, or, if it finds itself in the mouth cavity, avoids getting swallowed by sinking its sharp teeth in the jowl or tongue. It then makes a hole the size of in the soft tissue, and feed on meat from the meals of the new host. The candiru snake can live a long time in the mouth of the scavenger or predator, crawling occasionally to the outside to give birth to its young. In the case of the deeply burrowing Candirophis rotundus, though, the parasites tend to colonize the respiratory tract, causing eventually a pneumonia that can seriously debilitate the host. Whether it dies from the illness or becomes prey in it’s turn, the result is the same for the candiru snakes, of course.

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  29. 29. irenedelse 7:15 pm 04/29/2014

    Correction: “It then makes a hole the size of its body in the soft tissue…”

    Link to this
  30. 30. Tayo Bethel 11:23 pm 04/29/2014

    The Squamazoic is turning into a truly scary place …

    Why have vertebrates been more active in the parasitic field? Or should I say terrestrial vertebrates? Might it have to do with the fact that most land tetrapods use their lungs to breathe and have no other ways to efficiently acquire oxygen from fluids lie, say, the oxygenated bloodof host animals?

    Link to this
  31. 31. Tayo Bethel 11:30 pm 04/29/2014

    Sorry, typo. I meant to say why havent vertebrates been more active in the parasitic field.

    Link to this
  32. 32. DavidMarjanovic 4:55 am 04/30/2014

    found living inside the heart of a shark?

    what

    I’ll go look for the paper.

    Might it have to do with the fact that most land tetrapods use their lungs to breathe and have no other ways to efficiently acquire oxygen from fluids lie, say, the oxygenated bloodof host animals?

    That’s what I suspect.

    Link to this
  33. 33. Jerzy v. 3.0. 7:00 am 04/30/2014

    Also, parasites must be small and with low metabolism for host to be able to support them. Tetrapods score badly on both fronts. When hosts are extremely large, there is a possibility – maybe those vampire pterosaurs parasitising dinosaurs in the Mesozoic really existed?

    Link to this
  34. 34. John Scanlon FCD 8:49 am 04/30/2014

    …and have no other ways to efficiently acquire oxygen from fluids like, say, the oxygenated blood of host animals?
    There’s always arse-breathing, or even old-fashioned pharyngeal gills as in neotenous urodeles. Speaking of which, lissamphibians are well qualified to be disgusting parasites because they’re slimy and icky (sorry if that’s amniocentric of me).

    Link to this
  35. 35. John Scanlon FCD 8:54 am 04/30/2014

    Oh, did anybody notice how much the Agamodon skull resembles a cat’s (at least in lateral view)? It doesn’t take much to extrapolate to sabre-tooth land-candiru, so much better adapted for quick entry to those body cavities.

    Link to this
  36. 36. naishd 9:18 am 04/30/2014

    This article has received a surge of hits in the past 24 hours… I wonder if it’s because of the exciting comments you’ve all been providing? And there was I, worrying if an article about amphisbaenians might even bring in the required 23 comments…

    John (comment # 35): the Agamodon-cat similarity was commented upon by Gans in his 1974 book and was one of the key things that inspired the infamous article Amphisbaenians and the origins of mammals.

    Link to this
  37. 37. irenedelse 1:32 pm 04/30/2014

    @ Jerzy #33:
    And they must have be able to keep at bay to the host’s immune system. Via skin secretions for instance…

    @ John Scanlon #34:
    Oh yes, I can see it now: the salamander worm, alias “vampiric olm” (Neoproteus haemophagus)! Beware, the yucks continue…

    A small, limbless, neotenic species of Urodele, N. haemophagus inherited from its ancestor, the European olm (Proteus anguinus), several important traits: reduced limbs, ability to keep branchiae as an adult, plus a highly developed sense of smell as well chemical and electrical receptors. This sophisticated sensory apparatus, which enable today’s olm to live in lightless caves, makes it possible for N. haemophagus to sense potential hosts from long distances in the water or mud where the juveniles are born. They usually enter the body of their host via a natural orifice (mouth, anus, urethra…) and from there burrow inside the soft tissues, but they can take advantage of a wound to access the host’s blood flow. Once there, they migrate toward the bigger veins or even the inside chambers of the heart. They use their sharp, dagger-like teeth to cleave to the inside of the heart or blood vessel, and feed by suction on the flowing blood until they reach the stage of reproduction. The female, which can be partheogenetic, produce several eggs that mature inside her body. She then leaves her fixed life and swims and burrows toward the outside, using her acutely developed senses of smell, sound, pressure and electrical current to navigate. This burrowing causes a painful irritation to the host, which they try to alleviate by immersion in water or mud. This is perfect for the female salamander worm, who drops in and waits for the last stage of her life-cycle. Sadly, her fate is sealed: the young salamander worms leave the eggs while inside their mother’s body and start their life by eating her from the inside out. This first meal gives them enough resources to wait hours or days if needs be for another host to come along. It must be stressed that the horrifying reputation of the vampiric olm, while not entirely undeserved, shouldn’t blind us to the wonder of their sophisticated adaptations. To our knowledge, N. haemophagus is unprecedented in tetrapods as a genuine endoparasite, and for that alone, humanity should not try to eradicate this awe-inspiring creature.

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  38. 38. DavidMarjanovic 12:38 pm 05/1/2014

    As common as it is in squamates, I’m not aware of parthenogenesis being documented in any amphibian.

    Link to this
  39. 39. irenedelse 5:01 pm 05/1/2014

    @David:

    Try entering “parthenogenesis in Amphibians” in Google Scholar… Several species of frogs and at least one genus of salamanders (Ambystoma) have exhibited some form of parthenogenesis, either in captivity or in the wild. Some species of parthenogenetic Amphibians even seem to contradict expectations that unisexual species could only be short-lived: see Lampert and Sharl, BMC Biol. v. 8, 2010.

    Link to this
  40. 40. Jerzy v. 3.0. 4:28 am 05/2/2014

    BTW, what is about the ‘required 23 comments’? You made a bet that Tet Zoo articles always generate more comments than the rest of Scientic American combined? ;)

    Link to this
  41. 41. DavidMarjanovic 8:42 am 05/2/2014

    Lampert and Sharl, BMC Biol. v. 8, 2010.

    Thanks! Looks like they’ve taken this to the next level, quite different from what parthenogenetic squamates do (as the article says).

    what is about the ‘required 23 comments’?

    It’s just an observation that every Tet Zoo post gets at least 23 comments. :-)

    Link to this
  42. 42. Tayo Bethel 10:49 pm 05/2/2014

    I second David’s observation. Of all the scientific blogson the internet, I think Tet zoo gets the highest number of comments. For some strange reason, other blogs which seem just as interesting don’t get the same number of comments as TetZoo regularly does.

    Link to this
  43. 43. DavidMarjanovic 10:40 am 05/5/2014

    …Looks like 42 is a magic number, too.

    Link to this

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