Caecilians, an enigmatic type of amphibian, lead secretive lives underground and bear resemblance to a hybrid between a worm and a snake. One intriguing aspect of caecilian behavior is their unique method of feeding their offspring. Female caecilians produce a special layer of fatty skin tissue, which juvenile caecilians tear off using their baby teeth, evolved specifically for this purpose.
A recent study has shed light on the significance of skin-feeding beyond providing nutrients to the young. It was discovered that this process allows the mother to transfer microbes from her skin and gut to her offspring, essentially inoculating them to establish a healthy microbiome. This marks the first direct evidence of parental care in an amphibian contributing to the transmission of microbes across generations.
Parental care strategies vary widely across the animal kingdom. For instance, human mothers provide breastmilk to their babies, emperor penguins regurgitate food for their chicks, and female koalas feed their young a special form of feces. However, among amphibians, caecilians stand out for their unique feeding behavior.
Previous research on amphibian microbiomes focused mainly on frogs and salamanders, the more well-known orders of amphibians. Yet, those studies often yielded inconclusive results because most frog and salamander species do not care for their young after birth or hatching. In contrast, caecilians exhibit consistent parental care, with the mother always attending to the eggs and juveniles.
Herpele squalostoma, a caecilian species from central Africa that practices skin-feeding, became the focus of the recent research. The scientists collected samples from the environment, skin, and guts of 14 juveniles, nine female adults, and six male adults of this species. By analyzing the bacteria colonies in each sample, they found that every juvenile shared some part of their skin and gut microbiome with their attending mother. The transfer of microbes occurred through both skin-to-skin contact when the mother coiled around the young and when the juveniles consumed the mother’s skin.
Notably, the study also contributes to the relatively neglected field of African microbiome research. While Africa boasts significant genetic diversity, microbiome research has been predominantly centered in the Global North. Additionally, caecilians have historically been under-studied, partly due to their native habitats in the tropical regions of the Americas, Africa, and Southeast Asia, where scientific exploration has been limited.
The researchers hope to delve deeper into how microbiomes benefit caecilians and contribute to their overall health. Understanding the evolutionary advantages and potential absence of benefits when parental care is absent could be a focus of future investigations. This study serves as a foundation for further exploration, helping identify the microbial communities present in caecilian populations.