Date of Award
Doctor of Philosophy (PhD)
Ronald J. Siebeling
Two aspects of species identification were addressed; a molecular approach to identify anchovy larval and serological methods for prey detection in predator gut washes. Analysis of the pattern of restriction fragments of mitochondrial DNA (mtDNA) from adult anchovies from the Gulf of Mexico was employed to speciate four anchovy species. MtDNA isolated from white muscle of adult Anchoa mitchilli, A. hepsetus, A. nasuta and Engraulis eurystole produced an amplified 2.4 Kb DNA product when primers for NADH dehydrogenase 5 and 6 genes were used in polymerase chain reactions (PCR). Digestion of the amplified sequence with Dpn II produced a unique pattern for each of the four adult anchovy species examined. MtDNA extracted from ethanol preserved anchovy larvae when tested for PCR amplification yielded 2.4 Kb products in 16 of 30 samples examined. Restriction fragment patterns for eight larvae mtDNA extracts revealed agreement with morphological identification. Three larval digestion samples had new patterns not present in the adult anchovies examined. Four were recognized patterns but differed from morphological identification and one sample had insufficient DNA to distinguish the pattern. The second phase of the research concerned the use of serological techniques to elucidate predator-prey relationships by development of a laboratory model. The harpacticoid copepod, Amphiascoides atopus, was used to prepare a crude, soluble, whole animal extract to immunize rabbits. Anti-A. atopus serum detected A. atopus proteins in the proventricular contents of Grass Shrimp (Palaemonetes pugio) that were fed A. atopus. Slide agar gel immunodiffusion (AGID) and Western Blot techniques (WB) were used to detect prey proteins. Feeding trials show that prey proteins were detected by WB and AGID up to eight hours following feeding. Introduction of an alternate prey following a meal of A. atopus, shortened the residence time for detectable A. atopus protein to four hours. Employment of chemiluminescence in the WB format detected a meal often or more A. atopus in the predator gut one hour post feeding to provide a method for estimation of meal size in the grass shrimp fed A. atopus.
Hoyt, Marilyn J., "Serological and Molecular Biological Studies of Marine Predator-Prey Systems." (1998). LSU Historical Dissertations and Theses. 6739.