Abstract

Delphinidae represent an extreme and successful readaptation of mammalian physiology to the marine habitat and piscivorous diet. Some physiological aspects of their environmental fitness, such as the gut microbiota composition and its adaptation to their dietary niche, are less defined. Here, we explored the fecal microbiota structure of 65 bottlenose dolphins (Tursiops truncatus) aged between 3 and 57 years old (n=37 females and 28 males), kept under human care in 9 European facilities. According to our previous findings (Soverini et al. 2016), dolphins possess a unique microbiota profile within the Mammalia class, being largely dominated by the bacterial families Clostridiaceae, Vibrionaceae, Staphylococcaceae, Lactobacillaceae, and Peptostreptococcaceae, which highly resembles that of carnivorous marine fishes.

The present project aims to characterize the gut microbial ecosystem of bottlenose dolphins, in an attempt to: 1) validate and further extend, in an international context and in a larger animal cohort, the microbiota data recently published (Soverini et al. 2016); 2) establish correlations between the microbiota profile and animal-related variables, with the ultimate goal to identify possible gender- and/or age-related gut microbial signatures.

To this end, one fecal sample was collected from each animal (not receiving antibiotics for at least 15 days prior to collection) by voluntary behavior as reported by Biancani et al. (2009 and 2017). Samples were stored at -20°C in sterile plastic containers and shipped frozen to Italy. Information about sex, age, pregnancy, diet (fish species), and LSS (life support system) and water used in the pool were collected.

Fecal samples were analyzed for the characterization of the microbiota structure. Specifically, microbial DNA was extracted from feces and subjected to next-generation sequencing of hypervariable regions of the 16S rRNA gene, in an Illumina MiSeq platform, following manufacturer’s instructions (Illumina, San Diego, CA). Appropriate bioinformatics and statistical tools were applied to the sequence reads, in order to assess correlations between the compositional layout of the gut microbiota and all the variables collected, with a particular focus on possible microbial signatures related to the animal age and/or gender.

The characterization of the fecal microbiota of bottlenose dolphins will allow us to: 1) expand our knowledge of the intestinal microbial ecosystem of these aquatic mammalians and their adaptation to diet and the environment; 2) explore the existence of distinctive microbial configurations associated to age and/or gender, and their possible impact on host physiology.

Acknowledgements

The authors wish to thank all the facilities, the veterinarians, curators, and dolphins’ trainers involved in the study that helped with sample collection: Lisbon Zoo (Portugal), Mundomar (Spain), Oceanografic Valencia (Spain), Parc Asterix (France), Nuremberg Zoo (Germany), Mediterraneo Marine Park (Malta), Acquario di Genova (Italy), Zoomarine (Italy), Oltremare (Italy).

* Presenting author

Literature Cited

1.  Biancani B, Da Dalt L, Gallina G, Capolongo F, Gabai G. 2017. Fecal cortisol radioimmunoassay to monitor adrenal gland activity in the bottlenose dolphin (Tursiops truncatus) under human care. Marine Mammal Science. DOI: 10.1111/mms.12424.

2.  Biancani B, Da Dalt L, Lacave G, Romagnoli S, Gabai G. 2009. Measuring fecal progestogens as a tool to monitor reproductive activity in captive female bottlenose dolphins (Tursiops truncatus). Theriogenology. 72(9):1282–1292.

3.  Soverini M, Quercia S, Biancani B, Furlati S, Turroni S, Biagi E, Consolandi C, Peano C, Severgnini M, Rampelli S, Brigidi P, Candela M. 2016. The bottlenose dolphin (Tursiops truncatus) faecal microbiota. FEMS Microbiology Ecology. 92(4):fiw055.