Caecilians: Diet

Summary: What do these secretive amphibians eat? Join Kiersten as she takes you on a culinary journey in this episode on caecilian diet.

 

For my hearing impaired listeners, a complete transcript of this podcast follows the show notes on Podbean.

 

Show Notes: 

“Caecilian jaw-closing mechanics: integrating two muscle systems” by Thomas Kleinteich, Alexander Haas, and Adam P. Summers. J R Soc Interface, 2008 Dec 6: 5(29): 1491-1504. doi: 10.1098/rsif.2008.0155

 

“Diet of the Banana Caecilian Ichthyophis bannanicus in Mekong Delta, Vietnam” by Binh V. Ngo, Nghiep T. Hoang, and Chung D Ego. Journal of Herpetology, 48(4):506-513 (2014). doi.org/10.1670/13-113.

 

“Rotational feeding in caecilians: putting a spin on the evolution of cranial design” by G. John Easy and Anthony Herrel. Biology Letters (2006) 2, 485-487. doi: 10.1098/rsbl.2006.0516

 

“Dietary Partitioning in Two Co-occurring Caecilian Species (Geotrypetes seraphim and Herepele squalostoma) in Central Africa” by M. T. Kouete and D. C. Blackburn, Integr Org Bill, 2020; 2(1). doi:10.1093/iob/obz035 

 

Music written and performed by Katherine Camp

 

Transcript

(Piano music plays)

Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

(Piano music stops)

Welcome to Ten Things I Like About… I’m Kiersten, your host, and this is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating. 

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

This episode continues caecilians and the sixth thing I like about these awesome amphibians is their diet.

Our understanding of what and how caecilians eat is still evolving but we know enough to know that it is fascinating!

First, let’s talk about what they eat. Caecilians are carnivores. That means they eat meat. There have been enough studies into various species of caecilians that we have a decent idea of what prey items they tend to eat. In general they focus on invertebrates that are commonly found where they live, underground, in the leaf litter of tropical forests, and underwater. Some examples include ants, termites, earthworms, snails, and some caecilians have been recorded eating crabs, lizards, frogs, and blind snakes. Aquatic caecilians eat fish and aquatic invertebrates. You probably get the drift, if it’s an insect or small animal that lives where caecilians live and it fits in their mouth, they’ll eat it.

Since caecilians have no limbs to help them catch or stabilize prey items their jaw muscles and skulls have evolved to produce a high bite force to help prevent prey items from squiggling away. Caecilians have developed a double jaw muscle mechanism that is special to these amphibians. These muscles are different from other vertebrates because they are actually located above and below the jaw as opposed to the side of the jaw. Take a moment here and place your hands on the side of your jaw. Now open and close your mouth. What you feel moving is your jaw muscles. 

If we were able to place our hands on the sides of a caecilian’s jaw, we would not feel those muscles. Scientists think that the placement of the  muscles on the top and bottom of the skull may be due to the close confines of burrows in which the caecilians live and hunt. Whatever the reason it’s one more cool adaptations these amphibians have developed.

In the last episode we talked about the two different skull formations found in caecilians. At first thought, these differences might be due to the burrowing needs of the caecilian, but upon studying bite force and diet the different skull formations may actually be related to bite force. Caecilians who have the perforated, or zygokrotaphic, skull structure utilize the leverage from the two jaw muscles more efficiently than caecilians with the completely roofed, or stegokrotaphic, skull. What exactly does this information indicate? We’re not quite sure yet. We need more research to determine what these results may mean. For now, we’ll just have to settle for the knowledge itself.

Scientists, being the inquisitive people that they are, asked if caecilians might specialize in specific diet items. Two pieces of evidence leans us towards yes as the answer. One piece of evidence supporting this is tooth shape. Caecilains that eat mostly soft-bodied invertebrates, like earthworms, tend to have sharp curved teeth. This allows the teeth to hook into soft tissue and hold tight. Caecilians that tend to eat prey items that have a harder shell, such as snails, have flatter, pedestal style teeth. This allows them to crush and grind the hard shell. 

While we’re talking about teeth, let me toss this cool fact out there. Caecilians have two rows of teeth in their top jaw and may have one to two rows in the bottom jaw! Forgive my side trip, I just couldn’t resist telling you this fascinating fact.

The second form of evidence supporting diet specialization comes from a study done with two species of caecilians that live in the same area but in different layers of soil. Researchers analyzed the diet of Geotrypetes seraphini and Herpele squalostoma two terrestrial caecilians from Central Africa. G. seraphini lives lower in the soil and eats mostly earthworms, while mole crickets which are found higher in the soil or in leaf litter above ground dominated H. squalostoma’s diet. Now, we don’t know if the diet is dependent on where they live or if they live where their preferred diet can be found. That is a study for the future.

Caecilians just can’t stop surprising us! In another study looking at feeding  behavior of caecilians scientists discovered that these amphibians utilize  rotational feeding. What exactly is rotational feeding? Think about those nature programs you’ve seen about African animals being snatched up by a crocodile. The crocodile often catches something larger than it can swallow in one gulp and spins length wise. This behavior is used to reduce the size of a prey item so it can be easily consumed.

In this study, two species of terrestrial caecilians were observed and recorded eating. They caught both species using rotational feeding to successfully maneuver large prey items into their mouths, just like crocodiles. Unexpectedly, the researchers also observed the caecilians using rotational feeding even when they caught smaller prey items that easily fit into their mouths. So the question is why do they spin when the prey item fits easily into their mouth? We don’t have a solid answer to that question yet, but the researchers postulated that because caecilians are blind maybe they are using the rotational feeding to feel the prey item to help them determine what it is. 

The last behavior we’re going to talk about concerning caecilians’ diet is the most fascinating and slightly disturbing food item I’ve come across in all my years as an animal caretaker. Boulengerula taitanus is an African caecilian that begins life by eating its mother’s skin. You heard me correctly, they eat their mother’s skin! What?! 

So, while mom incubates her eggs that she laid in her subterranean tunnel the outer layer of her skin thickens with nutritious fatty lipids. When the young hatch they have special baby teeth that help them shave off the mother’s outer skin layer. This is the only vertebrate known to use this type of parental feeding strategy! I am thankful everyday I wasn’t born bird so my mother didn’t have to puke into my mouth to feed and now I’m thankful I wasn’t born a caecilian so I didn’t have to eat my mother’s skin.

That’s all for this episode and I know you loved this episode on caecilian diets because it’s the most fascinating episode I’ve researched so far and it’s my sixth favorite thing about this amphibian.

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change. 

 

Join me next week for another thing I like about caecilians!

 

(Piano Music plays) 

This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.