Project description:Walking catfish (Clarias macrocephalus) and channel catfish (Ictalurus punctatus) are freshwater fish species of the Siluriformes order. C. macrocephalus has both gills and modified gill structures serving as an air breathing organ (ABO) which allows them aerial breathing (AB), while I. punctatus does not possess an air-breathing organ (ABO), and thus cannot breathe in air. These two species provide an excellent model for studying the molecular basis of accessory air-breathing organ development in teleost fish. In this study, seven development stages in C. macrocephalus were selected for RNA-seq analysis to compare with channel catfish as the time when air breathing organ developed and became functional. Through comparative genetic contents analysis, 1,458 genes were identified to be present in C. macrocephalus, but absent from I. punctatus. Gene expression analysis and protein-protein intersection (PPI) analysis were performed, 26 genes were selected in C. macrocephalus, including mb, ngb, hbae genes, which are mainly associated with oxygen carrier activity, oxygen binding and heme binding activities. Our work provides a large data resource for exploring the genomic basis of air breathing function in C. macrocephalus and offers an insight into the adaption of aquatic organisms to hypoxia and high ammonia environment.
Project description:Little is known about the social structure of male sperm whales (Physeter macrocephalus) after they leave their natal units. While previous studies found no evidence for preferred associations among males, the observation of mass-strandings consisting exclusively of males, suggest that they have strong social bonds. To investigate the social associations among male sperm whales, we used half weight index of association, permutation tests and standardized lagged association rate models on a large photo-identification database collected between 2006 and 2017 in Nemuro Strait, Japan. Our results suggest that while male sperm whales are not as social as females, they do form long term associations, have preferred companionship, and forage in social proximity to each other. The best-fitting model to the standardized lagged association rate showed that associations among males last for at least 2.7 years and as most males leave the area after 2 years, associations may last for longer. Twenty dyads were observed associating over more than 2 years, for a maximum 5 years. One dyad was observed associating on 19 different days and clustered on 7 different days. Male associations may function to enhance foraging or to fend off predators. Such relationships seem to be adapted to a pelagic habitat with uncertain resource availability and predation pressure.
