No abstract

Major histocompatibility complex (MHC) class II DRB genotypes were examined in two geographically isolated populations of California sea lions (Zalophus californianus) (Gulf of California and California coastal Pacific Ocean). Genomic DNA from 227 California sea lions was examined using eight sequence-specific primer (SSP) pairs flanking the putative peptide-binding site. A total of 40 different Zaca-DRB genotype configurations were identified among the 227 individuals. Using SSP-PCR, significant differences were found between coastal California and Gulf of California Zalophus populations in numbers of DRB sequences per individual and configuration of sequences within individuals. Additionally, unique local patterns of MHC diversity were identified among the Midriff Island animals. These population differences are consistent with either ecologically distinct patterns of selection pressures and/or geographical isolation. The consequences of these partitioned MHC configurations at the population level are as yet unknown; however, the worldwide increase in emerging marine diseases lends urgency to their examination.

One hundred and twenty-five serum samples from California sea lion (Zalophus californianus californianus) pups, and one from an adult female from eight reproductive rookeries located in seven islands in the Gulf of California (Mexico), were collected during the 1994-96 reproductive seasons. These were tested for antibodies to 19 serovars of Leptospira interrogans using a Microscopic Agglutination Test (MAT). Forty-one samples (32%) had antibody levels from 1:20 to 1:320 to one or more serovars. The most frequently detected serotypes were Leptospira interrogans hardjo (n ϭ 13), cynopteri (8), ballum (6), and szwajizak (5). Serovars with the highest prevalence were Leptospira interrogans hardjo and serjoe (1:320), ballum (1:160), and cynopteri, girppotyphosa, and tarassovi (1:80). Based on these results, exposure of sea lions to L. interrogans serovar hardjo seems to be relatively common among colonies located in the islands of the Gulf of California in contrast with those located on the Pacific coast, where the most frequently detected serovar is L. interrogans serovar pomona.