Caecilia: Worms Or Vertebrates?
The natural world, despite its diversity, sometimes offers similar solutions to similar problems. This is known as evolutionary convergence, based on the appearance of similar structures between unrelated animals, conditioned by the biomechanical needs of the environment in which they live. This term is very important to understand the existence of caecilians, which we will present below.
How else can a vertebrate animal look so much like a primitive worm? The answer is simple: natural selection chooses the most successful living beings that have the best chances of survival in a given environment, since these will be the ones that will give rise to offspring passing their characteristics to the next generations.
That is why caecilians look like earthworms, since both species inhabit the subterranean kingdom and this elongated, wormy form is very successful in this environment.
Lesser known amphibians
Caecilia are amphibians belonging to the order Gymnophiona. They live mainly in humid tropical regions and exhibit fossorial habits, that is, they live underground. Due to their limited vital range and shy nature, these elongated beings rarely come into contact with humans. Therefore, they are very little known to the general population and it is easy for an inexperienced person to mistake them for a worm of enormous proportions.
Here are some general characteristics of these amphibians:
- The caecilians are of various sizes, from 98 millimeters for the Idiocranium russeli species to 1.5 meters for Caecilia thompsoni .
- They have very small eyes, which in many cases are only capable of detecting light differences in the environment. Some species have the entire ocular apparatus buried under the epidermis, a characteristic that shows that the eyes are vestigial organs underground.
- They have no limbs, but have strong cranial musculature that allows them to cut through the sediment, making them excellent excavators.
- They have two sensory “tentacles” located between the nose and the eyes, which allow them to detect odors.
As we can see, these animals are completely adapted for an underground life. This adaptation goes beyond external morphological modifications, because like snakes, they usually have reduced lungs (or the left one absent) to maintain their thin and wormy shape. The tretochoana eiselti species lacks both lungs, as various studies have found that it breathes only through the skin.
Ecology of caecilians
As we have anticipated previously, these small vertebrates spend most of their lives buried. Some of the species, such as Caecilia pachynema, only come out at night and in episodes of torrential rains.
As in the rest of amphibians, its diet is insectivorous and of small vertebrates. For this reason, despite their slowness and lack of reflexes, they maintain the characteristics of a predatory animal (such as teeth projected backwards that allow them to hold onto food).
A curious reproduction
It is interesting to dedicate its own space to the reproduction of this animal, since it presents strategies not seen in any other type of vertebrate. For example, the species Boulengerula taitanus shows a form of parental care based on matriphagia, that is, the young feed on the mother’s own tissue.
A study in the journal Nature showed revealing results regarding this atypical parental care:
- The females of this species have a skin twice as thick as the juvenile specimens that have not given rise to offspring. That is, they prepare for part of their body to be consumed.
- The cells of this tissue are different from those of other epithelia, as they are prepared to provide proteins and fats to the offspring.
- These young have a series of temporary teeth that allow them to tear off their mother’s skin segments.
This is not a common parental care method for caecilians, as most are limited to protecting the eggs by curling over them. Some species are ovoviviparous, that is, the larvae emerge fully formed from the female’s oviduct after passing through an egg stage within the uterus.
Nature does not leave us indifferent
As we have seen, caecilians are animals with exotic characteristics very little known to humans. Compared to other amphibians, there is very little information regarding their ecology and habits.
The first step to prevent the extinction of any species is to know it thoroughly and therefore studies of fauna, however strange and enigmatic, are essential to preserve the planet’s biodiversity.
