In all natural systems, some individuals die early on while others survive. Organisms are constantly under environmental, competitive, predatory, and immunological stress. The amount of mortality from each can be difficult to determine, as can the identification of attributes that provide advantage. In this dissertation, I investigate 1) whether misidentification is a source of error in studies of larval ecology and evolution, 2) the role of environmental stress and life-stage in host-vector relationships, and 3) whether genetic variations in blue crab populations may be associated with disease resistance.
There are a number of inconsistencies in studies of genetic structure and factors that impact larval settlement for blue crabs from Atlantic and Gulf of Mexico waters, including whether more than one species is present. We used DNA sequencing of larvae from monthly settlement collections in the northwest Gulf of Mexico to demonstrate the presence of multiple species, that species composition was spatially and temporally variable, and that frequently used morphological characters were not diagnostic. We discerned that factors impacting settlement were species specific. When species are lumped or misidentified, factors that impact settlement of individual species may not be recovered.
Marine parasites and pathogens have negative impacts on adult and juvenile blue crab populations. Less is known about the role of diseases for larval and post-larval life stages. We documented a 6-year pattern of infection by the parasitic dinoflagellate Hematodinium perezi for blue crab megalopae. High thermal stress decreased the prevalence of H. perezi infection in larvae and Vibrio spp. infections for juveniles and adults. To determine whether patterns in larval infection were due to host mortality or pathogen growth we put wild caught megalopae through heat stress trials. Heat stress resulted in rapid mortality for infected larvae, suggesting mortality and not transmission is influencing prevalence. Lastly, we used a single nucleotide polymorphism (SNP) assay to compare infected and uninfected blue crabs, identifying 12 SNPs showing associations with infection. Identification of these loci is the first step in using genetic variation to improve management, aquaculture, and conservation of economically and ecologically significant coastal species.
|Commitee:||Chlan, Caryl, Duke-Sylvester, Scott, Eggleston, Dave, Watson, Glenn|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||DAI-B 79/03(E), Dissertation Abstracts International|
|Subjects:||Biology, Ecology, Biological oceanography|
|Keywords:||Barcoding, Blue crab, Disease, Larvae, Resistance|
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