Peyton Jeter

University Honors with Honors in Marine Biology

Major: Marine Biology Minor: Psychology

Supervisor: Ami Wilbur, Biology and Marine Biology

Unusual Morphology in Scallops from Tampa Bay, Florida: Evidence of Possible Hybridization?

The bay and calico scallop, Argopecten irradians and Argopecten gibbus respectively, co-occur in coastal waters off the western coast of Florida near Tampa Bay. Observations of juveniles with anomalous morphology prompted questions regarding the possibility of hybridization. Because the species differ morphologically and genetically, the present study examined 15 shell characteristics (such as length of the anterior auricle, length of hinge, height of the anterior auricle, height of the posterior auricle, width of plicae, interplical distance, right intersinal distance, left intersinal distance, half diameter of the anterior distance, half diameter of the posterior distance, right valve convexity, left valve convexity, shell height, shell length, and shell width), 481 base pairs of the mitochondrial genome (16s ribosomal subunit) and a portion of the nuclear genome (Internal Transcribed Spacer Region) from twenty-four specimens collected from Tampa Bay, FL that were described as morphologically atypical. Samples of typical A. irradians (N=21) and A. gibbus (N=18) were collected from the same area. The morphological data collected were log-transformed and adjusted to a common size (20.36mm shell height) prior to statistical analysis to minimize the effects of size on the analysis of shape. Significant differences in morphology between A. irradians and A. gibbus were observed for 9 of the shell characteristics (Height of the anterior and posterior auricle (FG and HI); Interplical distance (J); Right intersinal distance (RLM); Half diameter of the anterior and posterior (AN and BO); Right and left valve convexity (RCN and LCN); and Length of the shell (AB)). Principle components analysis revealed the variation between species to be modest, but also showed many of the atypical scallops to be distinct from A. irradians and A. gibbus. Genetic analysis suggested that the majority of the atypical scallops were A. gibbus (19/21 specimens), however, attempts to determine if the two remaining specimens, which were A. irradians for mtDNA, were hybrids were inconclusive.