0Newswise — Caecilians are a mysterious type of amphibian known for their underground habitat and appearance, resembling a fusion of a worm and a snake. One intriguing aspect of caecilian behavior is their distinctive method of feeding their offspring. Mother caecilians develop a unique layer of fatty skin tissue, which the young ones tear off using specialized baby teeth evolved for this purpose.
Recently, a groundbreaking study has shed light on the significance of this skin-feeding behavior beyond just providing nutrients to the offspring. It appears that this process also serves as a means for the mother to pass on microbes from her skin and gut to her young, essentially inoculating them and initiating a healthy microbiome. This discovery marks the first direct evidence of parental care in an amphibian contributing to the transmission of microbes from one generation to the next.
David Blackburn, the Florida Museum's curator of herpetology, acknowledges the challenges in studying caecilians due to their elusive nature and the limited knowledge we have about these fascinating creatures. Consequently, this study represents a pioneering contribution as the first published exploration of a caecilian microbiome.
In the animal kingdom, various species have developed distinct parental care strategies. For instance, human mothers provide breastmilk to their babies, emperor penguins regurgitate food for their chicks, and female koalas feed their offspring a unique type of feces.
When it comes to amphibians, caecilians stand out due to their remarkable behavior of feeding their young. While previous research on amphibian microbiomes mainly focused on frogs and salamanders, which are more widely recognized orders within the Amphibia class, those studies yielded inconclusive results. This was largely because the majority of frog and salamander species do not care for their young after birth or hatching; they typically lay eggs and leave the offspring to develop independently.
However, the scenario is quite different for caecilians.
Marcel Talla Kouete, the first author of the study and a doctoral candidate in the University of Florida School of Natural Resources and Environment, emphasized that whenever caecilian eggs are found, the mother is always in close attendance. In fact, he has never encountered a juvenile caecilian without its mother present. This exceptional parental care sets caecilians apart within the amphibian world.
Kouete's fascination with caecilians grew as he delved into their study, particularly intrigued by their unique parenting behavior. Since this behavior was first observed in 2006, scientists have noted that even after the skin-feeding phase ends, mother and offspring continue to stay together, with the mother coiling her body around the young ones. This observation led Kouete to ponder whether this behavior served a purpose beyond just providing nutrients. He reasoned that there might be a transfer of microbes from the mother's skin, similar to bacterial transmission observed in other animal species.
In humans, microbes are transmitted to the skin during birth as babies pass through the mother's birth canal, and they further enter the body through breastmilk. These microbes play a crucial role in maintaining the well-being of the human body, forming a microscopic community known as the microbiome. They perform essential functions, such as breaking down complex carbohydrates, training the immune system, and producing vital vitamins. As a result, a growing body of research is dedicated to understanding the intricate relationship between disease and the health of the microbiome.
Kouete and his team dedicated their research to studying Herpele squalostoma, a caecilian species native to central Africa known for its skin-feeding behavior. The researchers collected samples from 14 juveniles, nine female adults, and six male adults, focusing on both the environment and the skin and gut microbiomes of these caecilians. Subsequently, they conducted bacterial colony sequencing for each sample.
The results revealed a remarkable finding: every juvenile shared some portion of their skin and gut microbiome with their attending mother. This transfer of microbes occurred during two key moments - when the mother coiled around the young, enabling skin-to-skin contact, and when the juveniles consumed the mother's skin during the skin-feeding process.
Interestingly, samples obtained from the surrounding soil, water, and leaves demonstrated that the immediate environment played a lesser role in shaping the juvenile microbiomes compared to the significant influence of their mothers' microbiomes.
Kouete's research paper not only sheds light on caecilian biology but also makes a significant contribution to an often overlooked area of study, African microbes. Despite the immense genetic diversity present on the African continent, microbiome research has predominantly centered around the Global North.
Caecilians, being native to tropical regions in the Americas, Africa, and Southeast Asia, have historically received limited attention in scientific research. This is partly due to the lack of significant scientific presence in these regions. However, Kouete, who hails from Cameroon, where the H. squalostoma specimens were sampled for the study, has taken a step towards bridging this gap.
Moving forward, the research team is eager to explore the advantages that microbiomes offer to caecilians and how they contribute to the amphibians' overall health. Kouete raises thought-provoking questions about whether there are evolutionary benefits to these microbial interactions and whether these benefits are absent in cases where parental care is absent.
By identifying some of the microbes present in caecilians, this paper serves as a foundation for future investigations. Blackburn aptly compares the study to exploring the diverse range of frogs inhabiting a forest. Just as understanding various frog species in an ecosystem helps infer their roles, the research aims to achieve a similar understanding of the caecilian microbiome and its ecological significance.
Molly Bletz, Brandon LaBumbard and Douglas Woodhams of the University of Massachusetts Boston are also authors on the paper.
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