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Mozambique Diary: Amphisbaenians

Most people would hardly look twice at this small, pink “worm”, but this amphisbaenian (Chirindia swynnertoni) from Gorongosa probably looks like the now extinct ancestor of all snakes.

Most people would hardly look twice at this small, pink “worm”, but this amphisbaenian (Chirindia swynnertoni) from Gorongosa probably looks like the now extinct ancestor of all snakes.

Having drawn the short straw at the phenotypic lottery I have always felt a special kinship with creatures that most people dismiss as too small, too creepy, too unattractive. Because these are (I tell myself) the hallmarks of the truly interesting organisms, ones that have followed the less-trodden paths of unusual specialization, remarkable adaptations, evolutionary ingenuity.

One such organism, about the existence of which I learned as a young child from an old zoology textbook, was Bipes, an amphisbaenian. It was a chimeric, strange creature, with the appearance of a pink snake, but equipped with a pair of shovel-like legs at the front end of its long body. There was a striking resemblance between that creature and a picture of a dragon that I had seen in the illustrated edition of the Old Testament from my Sunday School (which, incidentally, offered its classes on Monday nights), and I was instantly hooked.

Although it looks like a soft and squishy, the amphisbaenian’s head hides a strong skull that allows it to push through even the hardest soil.

Although it looks soft and squishy, the amphisbaenian’s head hides a strong skull that allows it to push through even the hardest soil.

Amphisbaenians are reptiles, but so unusual that for the longest time they were considered a separate order of these animals. For one, they look nothing like a vertebrate – the last couple of times that somebody brought me an amphisbaenian they were under the impression of having collected an earthworm (unlike Bipes, most species are legless.) Their annulated body is usually pink or covered with irregular, white and dark blotches, a clear indication that these animals don’t care about how they are perceived by others. And for a good reason – why bother with the looks if your entire life is spend underground and you yourself are blind. Better to invest the energy that would have been spent on the irrelevant appearance into things such as a thick skull and powerful thoracic muscles that will allow the animal to push effortlessly though the soil in search of prey.

My assistant Ricardo Guta looking for insects and other animals in the habitat of the Gorongosa amphisbaenian.

My assistant Ricardo Guta looking for insects and other animals in the habitat of the Gorongosa amphisbaenian.

Recent phylogenetic studies revealed that amphisbaenians are not a separate, primitive order of reptiles, but rather a highly derived, supremely modified lineage of lacertiform lizards. It is very likely that the next step in this transition to a subterranean lifestyle was the complete loss of limbs and girdles, a dramatic reshaping of the skull, the loss of eyelids and, eventually, the emergence of a brand new group of animals, the snakes. In fact, the most basal (primitive) snakes, the Typhlopidae and other related families, look remarkably like the amphisbaenians.
A few days ago I was in the southern part of Gorongosa, checking out sites for the second biodiversity survey of the park, and there, in a dry, crumbling log, I found a beautiful little amphisbaenian, Chirindia swynnertoni. This species is rarely seen, and thus I promptly followed a recommendation of a field guide to amphibians and reptiles of East Africa: “Anyone finding a worm-lizard [amphisbaenian] should take it to a museum.” I still haven’t had the heart to preserve it for the Gorongosa Synoptic Collection, and instead I have been watching it for days, transfixed by its amazing ability to squeeze into the hardest soil with the body that looks like an overcooked string of pasta, and with a baby-pink face of a newborn. It has been feeding on termites and ant larvae, crushing the insects with its tiny yet powerful jaws. And I find it fascinating (and somewhat rewarding) that from so seemingly unassuming a beginning came a lineage of animals that has terrified the human psyche since the time of Eden.

Gorongosa amphisbaenian (Chirindia swynnertoni)

Gorongosa amphisbaenian (Chirindia swynnertoni)

Mozambique Diary: Blind snakes of Gorongosa

A comparison of the largest blind snake of Gorongosa, the Giant blind snake (Megatyphlops schlegelii), and the smallest one, the Peter's thread snake (Leptotyphlops scutifrons)

A comparison of the largest blind snake of Gorongosa, the Giant blind snake (Megatyphlops schlegelii), and the smallest one, the Peter’s thread snake (Leptotyphlops scutifrons)

Last night’s downpour flushed out a lot of things from under the ground, and one of them was a large blind snake, Megatyphlops schlegelii, which I found as it was swimming in a puddle in front of the Scientific Services’ trailer. Now, large is a relative term – the snake is only a little over a foot long and as thick as a finger, but for blind snakes this is huuuge. Blind snakes, families Typhlopidae and Leptotyphlopidae, comprise some of the smallest reptiles, and definitely the smallest snakes, in the world. In fact, one species, Ramphotyphlops braminus, has spread over the globe with potted plants, mistaken for a small earthworm in the soil.

Both families are considered some of the most basal lineages of snakes, which means that their morphology and behavior gives us some insight into how snakes evolved from their closest relatives, lizards (or, more specifically, clade Toxicofera, which includes monitor lizards, agamas, and a few other groups). They are all subterranean and their morphology reflects this fact in the small but massively calcified skull, hard “beak” made of thick scales that allows them to push through the soil, and incredibly smooth body that minimizes frictions as they tunnel underground. The eyes are vestigial, hidden under semi-translucent scales, and are visible only as darker, light-sensitive spots on the sides of the head. Unlike other snakes they also lack a distinct tail – the body pretty much ends in a cloaca and all that remains of the tail is a tiny, sharp spike, their only defensive weapon.

The morphology of the Giant blind snake (Megatyphlops schlegelii) reveals its perfect adaptation for subterranean life – there is no neck or distinct tail, which means that the animal can move as easily forward as backward in the underground tunnels; notice the sharp defensive spike on the end of the body.

The morphology of the Giant blind snake (Megatyphlops schlegelii) reveals its perfect adaptation for subterranean life – there is no neck or distinct tail, which means that the animal can move as easily forward as backward in the underground tunnels; notice the sharp defensive spike at the end of the body.

Needles to say, blind snakes are completely harmless. They produce no venom and may even lack teeth in either the upper or lower jaw. When caught they try to jab the attacker with the tip of the tail, which is about as effective a defense as being licked by a puppy. Still, the first Megatyphlops I saw in Gorongosa was an animal being hacked to bits by villagers afraid of its (imaginary) venom.

The body of blind snakes is glossy smooth, reducing friction when moving underground. It also makes holding them in your hand rather difficult.

The body of blind snakes is glossy smooth, reducing friction when moving underground. It also makes holding them in your hand rather difficult.

So far I have found three species of blind snakes in the park, usually while flipping rocks when looking for crickets. Interestingly, I have also seen them frequently on the surface at night, moving slowly and deliberately, as if looking for something. These snakes feed mostly on termites and ants, the nests of which are often located under rocks and logs. I imagine that it is easier for the snakes to move on the surface to the next rock, than to plow under the surface, which may explain their behavior. Some blind snakes are known to produce pheromones that mimic those of their prey, thus protecting them from attacks by soldier termites and ants. Their feeding mechanism is different from that of other snakes – more evolutionarily derived snakes swallow the prey by alternatively advancing the left and right upper jaw arches (which can move independently) over the prey. But blind snakes don’t have long, independently movable upper jaw and instead “rake” their insect prey into the mouth by stretching and pulling back their short lower (Leptotyphlopidae) or upper (Typhlopidae) jaw. Apparently, smaller species may not even swallow the prey at all, but instead suck the liquid portion of the insect’s body and discard the exoskeleton.

Peter's thread snake (Leptotyphlops scutifrons), the smallest snake in Mozambique.

Peter’s thread snake (Leptotyphlops scutifrons), the smallest snake in Mozambique.

Mozambique Diary: Poetic justice

The Cape centipede-eater (Aparallactus capensis) from Gorongosa National Park, Mozambique

The Cape centipede-eater (Aparallactus capensis) from Gorongosa National Park, Mozambique

If we lived in an ideal world, right about now I would have been putting on my headlamp to begin stalking katydids in the luxuriantly green savannas of Gorongosa National Park. But, alas, we don’t. For reasons beyond my control I had to postpone a trip to Mozambique, although I hope to be able to get there within the next couple of months or so, and witness the park in its full, rainy season splendor.

When I was in Gorongosa in May, conducting a biodiversity survey of the Cheringoma Plateau, I was introduced by our intrepid herpetologists, MO Roedel and Harith Farooq, to an interesting little snake. The Cape centipede-eater (Aparallactus capensis), feeds, as the name suggests, exclusively on centipedes. These arthropods are not the friendliest of creatures, in fact I have a very healthy dose of respect for these powerful, blindingly fast predators. All centipedes are venomous and those large enough to be able to puncture human skin can deliver nasty, nasty bites. Their body shape, however, seems to make them ideal prey for snakes – they are long and thin, and a single centipede would nicely fill a snake of comparable size.

Aparallactus hunts by grabbing the victim in the middle of the body and slowly working its way towards the head, eventually swallowing the centipede head-first. The scales on this snake’s body are particularly hard, making it difficult for the centipede to sink its fangs (forcipules) into the reptile. At the same time the snake’s venom quickly subdues and kills the prey. Aparallactus belongs to a lineage of snakes known as side-stabbing snakes (Atractaspididae), which includes several deadly venomous species. But despite being powerfully venomous, centipede-eaters are not dangerous to humans as their short fangs are located in the back of the jaw and cannot reach the surface of our skin; one of the members of the genus, Aparallactus modestus, is even entirely fangless and feeds mostly on earthworms.

I have read that Aparallactus are immune to venom of their centipede prey, but the same cannot be said of other snakes found in Gorongosa. One rainy night on Mt. Gorongosa I ran across a scene that reinforced my high opinion of these multi-legged invertebrates: a large centipede was efficiently chomping to bits a House snake (Lamprophis capensis). If this is not the best example of poetic justice then I don’t know what is.

Centipede (Ethmostigmus sp.) devouring a House snake (Lamprophis capensis)

Centipede (Ethmostigmus sp.) devouring a House snake (Lamprophis capensis)