Genetic differentiation among sympatric migratory and resident life history forms of rainbow trout in British Columbia

Rainbow trout Oncorhynchus mykiss in coastal areas of North America occur as two divergent migratory types: steelhead that migrate to salt water and return to their natal river to spawn and resident rainbow trout that either do not migrate or migrate locally within the freshwater system. We extracted DNA from sympatrically occurring steelhead and rainbow trout collected from five major drainages in British Columbia. We used three types of genetic markers to test for differentiation within the sympatric population: microsatellite DNA markers, gene intron polymorphisms (restriction fragment length polymorphisms [RFLPs] and fragment size polymorphisms), and major histocompatibility complex (MHC) exon polymorphisms (RFLPs). The migratory and resident forms were genetically differentiated in only one sympatric population based on microsatellite data, but no significant differentiation was found using the combined gene locus marker data. Overall, most of the observed allele variation at all marker types was attributable to among-drainage variance, while migratory life history contributed a nonsignificant component based on hierarchical analysis of molecular variance. Interestingly, the migratory and resident forms were genetically differentiated in two different populations based on the gonadotropin and p53 intron polymorphisms, while no significant genetic differentiation was found between the two migratory types at any of the MHC exon or growth hormone intron-length polymorphisms. Furthermore, the neighbor-joining cluster dendrogram based on the microsatellite markers reflected geographic patterns, while the neighborjoining dendrogram using gene intron and MHC markers did not. Our data indicate that the migratory and resident life histories have probably evolved independently in different drainages in British Columbia. The disagreement between the results of the analyses using the microsatellite and gene locus markers probably reflects differences in selection, mutation, or both, acting at these two types of marker loci

Gastrolithiasis in prehensile-tailed porcupines (Coendou prehensilis): Nine cases and pathogenesis of stone formation

Gastrolithiasis was diagnosed in nine prehensile-tailed (PT) porcupines (Coendou prehensilis) housed at six zoologic institutions in the United States and Canada. Affected animals were either asymptomatic or had clinical signs, including weight loss, diarrhea, and depression. Abdominal palpation was adequate for diagnosis in all six antemortem cases, and radiographs confirmed a soft tissue density mass effect produced by the concretion. These gastroliths were all successfully surgically removed. Recurrence of gastrolith formation was common and occurred in four of the cases. Three cases were diagnosed postmortem, with the gastrolith causing gastric perforation in one case. Gastroliths from four cases were identified by mass spectrometry as bile acid precipitates consisting of the insoluble acid form of endogenous glycine-conjugated bile acids

Batrachochytrium salamandrivorans (Bsal) not detected in an intensive survey of wild North American amphibians.

The salamander chytrid fungus (Batrachochytrium salamandrivorans [Bsal]) is causing massive mortality of salamanders in Europe. The potential for spread via international trade into North America and the high diversity of salamanders has catalyzed concern about Bsal in the U.S. Surveillance programs for invading pathogens must initially meet challenges that include low rates of occurrence on the landscape, low prevalence at a site, and imperfect detection of the diagnostic tests. We implemented a large-scale survey to determine if Bsal was present in North America designed to target taxa and localities where Bsal was determined highest risk to be present based on species susceptibility and geography. Our analysis included a Bayesian model to estimate the probability of occurrence of Bsal given our prior knowledge of the occurrence and prevalence of the pathogen. We failed to detect Bsal in any of 11,189 samples from 594 sites in 223 counties within 35 U.S. states and one site in Mexico. Our modeling indicates that Bsal is highly unlikely to occur within wild amphibians in the U.S. and suggests that the best proactive response is to continue mitigation efforts against the introduction and establishment of the disease and to develop plans to reduce impacts should Bsal establish