Multi-species and multi-tissue methylation clocks for age estimation in toothed whales and dolphins.

The development of a precise blood or skin tissue DNA Epigenetic Aging Clock for Odontocete (OEAC) would solve current age estimation inaccuracies for wild odontocetes. Therefore, we determined genome-wide DNA methylation profiles using a custom array (HorvathMammalMethyl40) across skin and blood samples (n = 446) from known age animals representing nine odontocete species within 4 phylogenetic families to identify age associated CG dinucleotides (CpGs). The top CpGs were used to create a cross-validated OEAC clock which was highly correlated for individuals (r = 0.94) and for unique species (median r = 0.93). Finally, we applied the OEAC for estimating the age and sex of 22 wild Norwegian killer whales. DNA methylation patterns of age associated CpGs are highly conserved across odontocetes. These similarities allowed us to develop an odontocete epigenetic aging clock (OEAC) which can be used for species conservation efforts by provide a mechanism for estimating the age of free ranging odontocetes from either blood or skin samples.

Environmental Sources of Bacteria Differentially Influence Host-Associated Microbial Dynamics.

Host-associated microbial dynamics are influenced by dietary and immune factors, but how exogenous microbial exposure shapes host-microbe dynamics remains poorly characterized. To investigate this phenomenon, we characterized the skin, rectum, and respiratory tract-associated microbiota in four aquarium-housed dolphins daily over a period of 6 weeks, including administration of a probiotic during weeks 4 to 6. The environmental bacterial sources were also characterized, including the animals' human handlers, the aquarium air and water, and the dolphins' food supply. Continuous microbial exposure occurred between all sites, yet each environment maintained a characteristic microbiota, suggesting that the majority of exposure events do not result in colonization. Small changes in water physicochemistry had a significant but weak correlation with change in dolphin-associated bacterial richness but had no influence on phylogenetic diversity. Food and air microbiota were the richest and had the largest conditional influence on other microbiota in the absence of probiotics, but during probiotic administration, food alone had the largest influence on the stability of the dolphin microbiota. Our results suggest that respiratory tract and gastrointestinal epithelium interactions with air- and food-associated microbes had the biggest influence on host-microbiota dynamics, while other interactions, such as skin transmission, played only a minor role. Finally, direct oral stimulation with a foreign exogenous microbial source can have a profound effect on microbial stability. IMPORTANCE These results provide valuable insights into the ecological influence of exogenous microbial exposure, as well as laying the foundation for improving aquarium management practices. By comparing data for dolphins from aquaria that use natural versus artificial seawater, we demonstrate the potential influence of aquarium water disinfection procedures on dolphin microbial dynamics.

Natural exposure to domoic acid causes behavioral perseveration in Wild Sea lions: Neural underpinnings and diagnostic application.

Domoic acid is a naturally occurring algal toxin that causes neurological symptoms and mortality in exposed marine life. California sea lions (Zalophus californianus) are the most visible victims, and suffer epilepsy and progressive hippocampal atrophy. Despite its reliable neurological effects, little is known about how exposure to domoic acid alters behavior, which is critical for understanding the impact of toxic exposure on long-term survival in sea lions and other exposed animals, including humans. Better understanding of the behavioral effects may also inform veterinary diagnosis and treatment. Anecdotally, exposed sea lions have been reported to show enhanced perseverative behavior. To assess the neurobehavioral effects of domoic acid, we compared veterinary diagnoses, measures of hippocampal volume from in vivo MRI, and behavioral measures of habituation and dishabituation in 27 wild sea lions undergoing rehabilitation. The sample was divided post-hoc between subjects with clear veterinary diagnoses of chronic domoic acid toxicosis and those with no evidence of the disease. In the behavioral task, subjects were exposed repeatedly to sounds from two source locations, and, following a short delay, exposed again. Veterinary diagnosis of domoic acid toxicosis was associated with extent of hippocampal damage, predicted delayed habituation in phase 1, and enhanced dishabituation in phase 2. Receiver operating characteristic analysis indicated that delayed habituation in phase 1 was diagnostically predictive. Enhanced dishabituation in phase 2 was correlated with reduced right ventral hippocampal volume. Together, delayed habituation and enhanced dishabituation following domoic acid exposure indicate a clinically relevant and potentially maladaptive behavioral pattern of perseveration.