Title

Population Genetic Structure and Gene Expressions Patterns of the Copepod Calanus finmarchicus in the North Atlantic Ocean

Date of Completion

January 2011

Keywords

Biology, Evolution and Development|Biology, Oceanography

Degree

Ph.D.

Abstract

Calanus finmarchicus (Copepoda, Calanoida) is an ecologically important copepod species that is ubiquitous in coastal and open waters of the North Atlantic Ocean. Basin-scale and small-scale spatial genetic variation in C. finmarchicus was examined among and within geographic population samples obtained from the Northwest, North Central, and Northeast Atlantic gyres during 2005. Allelic variation at 24 Single Nucleotide Polymorphisms (SNPs) at selected nuclear loci (CS, hsp70, and AMPK) suggested large-scale differentiation involving two to four distinct gyre populations, reflecting persistent barriers to gene flow associated with entrainment in ocean gyres. Barents Sea population was found to be distinctive. The analyses also revealed small, but significant, differentiation among 10 areas examined within gyres, potentially reflecting ecologically important, short-term variation driven by variation in life history traits. ^ Temporal variation in Northwest Atlantic populations of C. finmarchicus was examined using time-series collections from within the Gulf of Maine, which is subject to major environmental variation. This study examined interannual variation of selected genetic characteristics for C. finmarchicus associated with a dramatic decline in abundances in 1998 following a negative NAO anomaly in 1996. SNPs in the citrate synthase (CS) encoding gene were analyzed for C. finmarchicus samples collected during 1997, 1998 and 1999, and compared with samples obtained from 2003, 2004 and 2005. The results indicated the presence of significant variation in SNP allele and genotype frequencies among years, and the distinctiveness of 1999 samples, possibly as a result of advective import of genetically divergent copepods from adjacent regions.^ The molecular mechanisms underlying important physiological processes of the species were examined through differential gene expression analysis for copepodite stage 5 (CV) and female C. finmarchicus obtained from surface and deep waters in Gulf of Maine, by using an Expressed Sequence Tag (EST) microarray. Up-regulation of genes involved in cell division, protein synthesis and mating were remarkable in deep females and CVs. Up-regulation of genes related to cellular homeostasis, circadian behavior and nervous system development were pronounced in surface females. Lastly, up-regulation of genes related to muscle development and protein catabolism were indicated for deep CVs compared to deep females.^