LE3 .A278 2018

2018

Easy, Russell

Acadia University

Bachelor of Science

Honours

Biology

Biology

The Scotian shelf, located in the Northwest Atlantic, has approximately forty different species of cephalopods. These include sympatric populations of the Atlantic longfin squid (Doryteuthis pealeii) and the Atlantic shortfin squid (Illex illecebrosus). Due to the various developmental changes that take place during the lifecycle of a squid, these common inshore species cannot always be accurately differentiated based on their morphology alone. DNA barcoding techniques have broadened taxonomic studies to allow for detailed species identification when morphological classification can be unreliable on its own. This study incorporates molecular data to identify a phylogeny of longfin squid caught off the Nova Scotian coast. Total DNA was extracted from tissue of D. pealeii collected from both Bramber and Chester, Nova Scotia. End-point PCR was performed using primers targeting cytochrome c oxidase subunit I (Cox1), cytochrome b(cytb) and 18S rDNA genes. Following sequencing, phylogenetic trees of various topologies were constructed. Results supported the efficiency of these genes as genetic markers to differentiate between closely related squid species, as well as contributed valuable sequence information to be submitted to NCBI GenBank. Phylogenetic tree analysis supported previous studies which questioned the validity of many cephalopod sequences deposited in open access databases. Findings stress the importance of utilizing external references with caution and the need for further molecular studies to be conducted with regards to squid. DNA barcoding analysis can be extremely valuable in order to reduce species misidentification and produce more accurate squid stock assessments for the development of conservation policies. These results may also provide valuable information for prospective commercial squid fisheries in Nova Scotia.

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https://scholar.acadiau.ca/islandora/object/theses:2670