A new research led by Dr Alistair Dove of Georgia Aquarium (Atlanta, Georgia) has provided evidence that a suite of techniques called metabolomics can be used to determine the health status of whale sharks.
The Whale shark, Rhincodon typus, is the world’s largest fish species. The largest confirmed specimen had a length of about 42 feet and a weight of more than 21 tons.
The new study, published in the journal PLoS ONE, shows that the major difference between healthy and unhealthy whale sharks is the concentration of a compound called homarine in their serum – indicating that homarine is a useful biomarker of health status for the species.
The study is especially significant to the veterinary science community because it documents the results of a rare opportunity to collect and analyze blood from whale sharks. It also comprises the only work yet carried out on biochemistry of the world’s largest fish.
“This research and its resulting findings are vitally important to ensuring Georgia Aquarium’s and the scientific community’s care, knowledge, and understanding of not only whale sharks, but similar species of sharks and rays,” said Georgia Aquarium’s Dr Greg Bossart, who was not involved in the study. “The publishing of this clinical research provides a greater opportunity for scientists and zoological professionals to understand the animals in our care and can be used to help wild populations, which puts us ahead of the curve in the integrated understanding of animal biology.”
Previous studies showed that traditional veterinary blood chemistry tests were not as useful with whale sharks; most likely because such tests are designed for mammals and comparatively less is known about shark and ray blood.
Dr Dove and his colleagues set out to significantly increase knowledge of whale shark biochemistry by examining the metabolite composition of all six whale sharks, which have been cared for at Georgia Aquarium. By using metabolomics, the scientists were able to determine which chemical compounds were present in the shark blood, without knowing ahead of time what they are.
“It is vitally important for us to continue to learn how to best support the whale sharks in our care,” Dr Dove said. “We began the study by asking ourselves: what should we be looking for in whale shark serum? And, what compounds in serum might best indicate the health status of whale sharks?”
Not only did the study determine that metabolic profiles of unhealthy whale sharks were markedly different than those of healthy sharks in general and particularly the different levels of homarine, but the research team also identified more than 25 other compounds that differed in concentration based on the health of the individual.
The findings will help scientists and veterinarians to better understand the biology of whale sharks in their natural setting, and by homology, the biology of other shark and ray species that may be similar. Further, data compiled in the research will provide a reference library about whale shark biochemistry that can be consulted in future studies and importantly, adds new knowledge that will be useful to those who care for sharks and rays on a daily basis.
“This sort of advanced research is only made possible through collaboration between aquarium scientists and experts at our partner universities,” Dr Dove said.
Bibliographic information: Dove ADM et al. 2012. Biomarkers of Whale Shark Health: A Metabolomic Approach. PLoS ONE 7 (11): e49379; doi: 10.1371/journal.pone.0049379