Venomous Snakes Reveal Ecological and Phylogenetic Factors Influencing Variation in Gut and Oral Microbiomes

The gastrointestinal tract (GIT) of vertebrates contains a series of organs beginning with the mouth and ending with the anus or cloacal opening. Each organ represents a unique environment for resident microorganisms. Due to their simple digestive anatomy, snakes are good models for studying microbiome variation along the GIT. Cloacal sampling captures the majority of the microbial diversity found in the GIT of snakes—yet little is known about the oral microbiota of snakes. Most research on the snake mouth and gut microbiota are limited to studies of a single species or captive-bred individuals. It therefore remains unclear how a host’s life history, diet, or evolutionary history correlate with differences in the microbial composition within the mouths and guts of wild snakes. We sampled the mouth and gut microbial communities from three species of Asian venomous snakes and utilized 16S rRNA microbial inventories to test if host phylogenetic and ecological differences correlate with distinct microbial compositions within the two body sites. These species occupy three disparate habitat types: marine, semi-arboreal, and arboreal, our results suggest that the diversity of snake mouth and gut microbial communities correlate with differences in both host ecology and phylogeny.

Macroscopic digestive anatomy of ring-tailed lemurs (Lemur catta), including a comparison of frozen and formalin-stored specimens

Digestive tract measurements are often considered species-specific, but little information exists on the degree to which they change during ontogeny within species. Additionally, access to anatomical material from nondomestic species is often limited, with fixed tissues possibly representing the only available source, though the degree at which this material is representative in terms of dimensions and weight is debatable. In the present study, the macroscopic digestive tract anatomy (length of intestinal portions, and tissue weights of stomach and intestines) of n=58 Lemur catta (from neonates to 25 years of age) was quantified, of which 27 had been stored frozen and 31 fixed in formalin. Particular attention was paid to the caecum and the possible presence of an appendix. The intraspecific allometric scaling of body mass (BM)0.46[0.40;0.51] for total intestine length and BM0.48[0.41;0.54] for small intestine length was higher than the expected geometric scaling of BM0.33, similar to literature results on interspecific scaling. This difference in scaling is usually explained by the hypothesis that the diameter of the intestinal tube cannot increase geometrically, to maintain optimal absorption. Therefore, geometric volume gain of increasing body mass is accommodated by more-than-geometric length scaling. Literature describes L. catta as being variable with respect to the presence of an appendix. No appendix was found in specimens of the present study. The proportions of length measurements did not change markedly during ontogeny, indicating that proportions developed in the foetus are already representative for the adult animal. By contrast, width and tissue-mass scaling of the caecum indicated a disproportionate growth of this organ during ontogeny that was not reflected in its length. Compared to overall intraspecific variation, the method of storage (frozen vs. formalin) had no relevant impact on length or weight measurements.

Animal Nutrition

Nutrition is the key driver of animal health, welfare and production. In agriculture, nutrition is crucial to meet increasing global demands for animal protein and consumer demands for cheaper meat, milk and eggs and higher standards of animal welfare. For companion animals, good nutrition is essential for quality and length of life. Animal Nutrition examines the science behind the nutrition and feeding of the major domesticated animal species: sheep, beef cattle, dairy cattle, deer, goats, pigs, poultry, camelids, horses, dogs and cats. It includes introductory chapters on digestion and feeding standards, followed by chapters on each animal, containing information on digestive anatomy and physiology, evidence-based nutrition and feeding requirements, and common nutritional and metabolic diseases. Clear diagrams, tables and breakout boxes make this text readily understandable and it will be of value to tertiary students and to practising veterinarians, livestock consultants, producers and nutritionists.