Marine Science

Marine Science

Senior Theses 2006

Melissa M. Berrien (2006). The Evolutionary Relationships of Doryteuthis pealeii: a Phylogentic Study of Squid
Faculty Advisor: Peter Meylan


It has been difficult to firmly establish evolutionary relationships among cephalopods using morphological and paleontological characters. Analyzing molecular data has become a useful and important tool for evaluating these relationships. The purpose of this study is to gain a better understanding of genomic organization and phylogeny of Doryteuthis pealeii by isolating, amplifying, and sequencing portions of its mitochondrial genome, and then using the new sequence data to test hypotheses of relationships proposed by previous workers.

Variable genome organizations have been observed in squid, relative to octopus and the polyplacophoran, Katharina tunicata. Heterololigo bleekeri represents a major rearrangement while Watasenia scintillans and Todarodes pacificus represent a genome with duplicated genes. It was hypothesized and supported by my study that Doryteuthis pealeii and D. plei have genome organizations more homologous to the rearranged Heterololigo bleekeri. It has been proposed that Doryteuthis pealeii and Heterololigo bleekeri belong to the subfamily Lolligunculini. My study rejects the inclusion of Doryteuthis pealeii in the subfamily Lolligunculini in all analyses and instead places Doryteuthis pealeii as a sister to Loligo.

Student Research