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Taita African Caecilian

TAITA AFRICAN CAECILIAN (Boulengerula taitana)

Image modified from Wikipedia. Original image
by Milvus
    When I was a kid, my family was friends with this other family, and one of the older sons had a tank of caecilians. These animals were very confusing to me, because "caecilian" and "Sicilian" are pronounced approximately the same way, and I couldn't figure out what limbless tropical amphibians had to do with Sicily. Nevertheless, I thought they were really cool and always asked if I could go look at them when we were visiting over there. And then I didn't think about them for like 15 years, until I was at university and learning about amphibians for my animal taxonomy course and saw the word written down and was like "ohhhhhhhhhh"

Appearance

Caecilians look like the love child of a snake and a slug. In the grand scheme of things, this is not that weird: right now the internet is all freaked out about carcinization, but only because it hasn't yet learned how prevalent the vermiform body shape is. However, given that caecilians are amphibians, it's a little bizarre. They're almost like salamanders with no legs. They have really tiny eyes, which doesn't help, and this particular species of caecilian has ring-like lines along its body, emphasizing its worm-like appearance. They're quite a bit bigger than I would like a worm to be, but a lot smaller than the largest earthworms.

Points: 0/1, just commit to being a worm ya weirdo

Behaviour

Caecilians are dirt creatures, and that means they have to be really good at digging. But how can you be good at digging when you have no arms or legs? They have really strong skulls and muscular... torsos I guess... and they dig face first. That's right, they just shove their noggins right into the dirt to make a hole. Interestingly, they will test the soil before diving in to see how compacted it is, and go out of their way to make tunnels and burrows in looser dirt. Furthermore, they'll go hang out in pre-existing holes when possible, because even though they are good at digging, they are also lazy.

Females tend to build nests close together and there have been a few observations suggesting they might help take care of each others' kids. We usually don't think of complex social behaviour happening outside of large-brained vertebrates, or swarming things, so it's pretty cool that there is some at least not-anti-social behaviour going on with amphibians.

Points: 0.5/1 if weird-ass worm-salamanders are out there lifting each other up, why can't humans get their shit together for two fucking seconds

Distribution

The Taita African caecilian lives, as far as we know, only in one area - the Taita Hills of Kenya, and specifically in the forested part. Also as far as we know, they live exclusively in the dirt rather than, say, climbing in the trees or otherwise utilizing more of the landscape. This is not a great strategy because, y'know, the planet on which we live is not static. However, they're found sometimes in agricultural gardens, which suggests they might be getting along okay in a human modified environment.

Points: 0.5/1

Ecology

Long has a war raged between ecologists about the diet of the Taita caecilian. Some believe that they specialize in eating termites, while others assert that they eat a whole bunch of stuff, including dirt. The most thorough study I read examined the gut contents of 40 animals and found earthworms, ants, termites, and fly larvae in various stages of digestion, but almost no dirt. So everybody's wrong but at least there is a definitive answer, right? WRONG! Biologists will always find something to argue with one another about! This study was conducted during masika (the rainy season), so maybe caecilian diet is different during vuli (the dry season)? Somebody has to be right, by god.

Points: 1/1 I guess why not

Evolution

Amphibians were invented a while ago when a bunch of lobe-finned fish decided to grow legs and start walking around on land. 170 million years later, caecilians said "no thanks" to legs and turned into worms. Yep, that's pretty much how evolution works and I should not by any means be required to surrender my one-and-a-half degrees in biology for phrasing it like that.

Anywho, caecilians tapped an underexploited niche and obviously did pretty well for themselves because they've been around since the Triassic period (for my readers who aren't dorks, the Cretaceous period was the one with all the cool dinosaurs, and the Triassic was the one two periods before that). Early Triassic caecilians had pretty big eye-holes and more frog shaped heads, but by the end of the Triassic their eye-holes were tiny, and they had narrow skulls and gross nubbly teeth. Since then, they haven't changed a whole lot, so what they're doing works real well for them.

Points: 1/1 for consistency 

Life History

If I walked down Spring Garden Road in Halifax, Nova Scotia, and asked every person I encountered what they know about amphibians, I would likely get answers ranging from "licking toads can get you high" to "what are you, a fucking cop?" However, I would wager a trivial amount of money that a large fraction of the answers would have something to do with metamorphosis. One of the most iconic things about amphibians is that a lot of them have indirect development - that is, most frogs and newts go through a floppy tadpole stage before turning into something with legs. But caecilians (and lots of other amphibians not appearing in this review) don't do that. Freshly hatched caecilians look like floppy little worms and then they just turn into floppy big worms.

Another thing that amphibians are know for is being kind of shitty parents relative to like birds and mammals. This is extremely unfair, because a lot of them are really good at taking care of their babies - Suriname toads (bane of people with trypophobia) carry their kids around on their backs, and red-backed salamanders aggressively defend their eggs from... uh... cannibalistic members of their own species. Taita African caecilians take parental care to a level that's about as extreme as the Suriname toad so... be ready for that.

After a Taita caecilian lays her eggs, her skin cells swell up with lots of delicious fats and proteins, and her outer layer of skin gets thick and dull. The babies hatch with those nubbly little teeth I mentioned earlier, and until they are big enough to go forage for food on their own, they're sustained by EATING THEIR MOTHER'S FUCKING SKIN. That's right, they use their horrible teeth to literally rasp off the nutrient-rich skin layers their mothers grow just for them. Just goes to show that motherhood is universally a nightmare.

Points: 0.5/1 for being good moms but also really gross

Interaction with Humans

Despite being fairly abundant in the area where it lives, the Taita African caecilian is nevertheless listed as endangered by the IUCN because it only lives in this one very small area, and because its population are decreasing. Habitat destruction is a major threat all species face, and the more specific the habitat, the more threatening that is.

On the plus side, the Kenyan government is very proactive about habitat conservation and sustainable resource use, and the forested part of the Taita Hills is one of the areas under the protection of the Kenya Forest Service. This gives me some hope for the persistence of these weird little amphibians.

Points: 1/1

Final Score: 4.5/7
Verdict: They're great

Further Reading

  • Ducey PK, Formanowicz Jr. DR, Boyet L, Mailloux J, Nussbaum RA. Experimental examination of burrowing behaviour in caecilians (Amphibia: Gymnophiona): effects of soil compaction on burrowing ability of four species. Herpetologica. 49(4): 450-457

  • Fox H. 1985. The tentacles of Ichthyophis (Amphibia: Caecilia) with special reference to the skin. Journal of Zoology, London. 205: 223-234

  • Gaborieau O, Measey GJ. 2004. Termitivore or detritivore? A quantitative investigation into the diet of the East African caecilian Boulengerula taitanus (Amphibia: Gymnophiona: Caeciliidae). Animal Biology. 54(1): 45-56

  • IUCN SSC Amphibian Specialist Group. 2013. Boulengerula taitana. The IUCN Red List of Threatened Species. Link

  • Kenya Forest Service. Link

  • Kupfer A, Muller H, Antoniazzi M, Jared C, Greven H, Nussbaum RA, Wilkinson M. 2006. Parental investment by skin feeding in a caecilian amphibian. Nature. 440: 926-929

  • Pardo JD, Small BJ, Huttenlocker AK. 2017. Stem caecilian from the Triassic of Colorado sheds light on the origins of Lissamphibia. PNAS. 114(27). Open Access 

  • Whittaker K. 2009. Boulengerula taitana. AmphibiaWeb. Link 

  • Wilkinson M. 2012. Caecilians. Current Biology. 22(17)


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