Class II DRB polymorphism and sequence diversity in two vesper bats in the genus Myotis.

Almost no studies have been done with respect to major histocompatibility complex (MHC) polymorphism and sequence diversity in bats, although they account for one in five living mammalian species. We analysed MHC Class II DRB polymorphism and sequence diversity in two Mexican verpertilionid bat species, the widespread continental species Myotis velifer and the narrowly distributed (and endangered) island endemic Myotis vivesi. We find extensive DRB polymorphism in the widespread M. velifer, similar to that commonly reported in other mammals. The geographically restricted M. vivesi by contrast shows only very limited polymorphism. We conclude that M. vivesi has undergone a dramatic loss of MHC polymorphism. The significance of this inference in light of other information on population structure and genetic diversity in this species is discussed.

Flight muscle enzymes and metabolic flux rates during hovering flight of the nectar bat, Glossophaga soricina: further evidence of convergence with hummingbirds.

Given their high metabolic rates, nectarivorous diet, and ability to directly fuel their energetically-expensive flight using recently-ingested sugar, we tested the hypothesis that Pallas long tongued nectar bats (Glossophaga soricina) possess flight muscles similar to those of hummingbirds with respect to enzymatic flux capacities in bioenergetic pathways. In addition, we compared these biochemical capacities with flux rates achieved in vivo during hovering flight. Rates of oxygen consumption (V(O(2))) were measured during hover-feeding and used to estimate rates of ATP turnover, glucose and long-chain fatty acid oxidation per unit mass of flight muscle. Enzyme V(max) values at key steps in glucose and fatty acid oxidation obtained in vitro from pectoralis muscle samples exceed those found in the locomotory muscles of other species of small mammals and resemble data obtained from hummingbird flight muscles. The ability of nectar bats and hummingbirds to hover in fed and fasted states, fueled almost exclusively by carbohydrate or fat, respectively, allowed the estimation of fractional velocities (v/V(max)) at both the hexokinase and carnitine palmitoyltransferase-2 steps in glucose and fatty acid oxidation, respectively. The results further support the hypothesis of convergent evolution in biochemical and physiological traits in nectar bats and hummingbirds.

Diet and the evolution of digestion and renal function in phyllostomid bats.

Bat species in the monophyletic family Phyllostomidae feed on blood, insects, small vertebrates, nectar, fruit and complex omnivorous mixtures. We used nitrogen stable isotope ratios to characterize bat diets and adopted a phylogenetically informed approach to investigate the physiological changes that accompany evolutionary diet changes in phyllostomids. We found that nitrogen stable isotopes separated plant-eating from animal-eating species. The blood of the latter was enriched in (15)N. A recent phylogenetic hypothesis suggests that with the possible exception of carnivory, which may have evolved twice, all diets evolved only once from insectivory. The shift from insectivory to nectarivory and frugivory was accompanied by increased intestinal sucrase and maltase activity, decreased trehalase activity, and reduced relative medullary thickness of kidneys. The shift from insectivory to sanguinivory and carnivory resulted in reduced trehalase activity. Vampire bats are the only known vertebrates that do not exhibit intestinal maltase activity. We argue that these physiological changes are adaptive responses to evolutionary diet shifts.