Meeting Abstract

27.4  Jan. 5  Taxonomic Significance of Gill Slit Morphology in Extant Sharks DOLCE, J.L.*; WILGA, C.D.; University of Rhode Island jdol6206@postoffice.uri.edu

The number of gill slits that an elasmobranch species possesses is often used for taxonomic classification. However, other characteristics of the gill slits that have been overlooked appear to have taxonomic significance. In this study, the length of each slit, spacing among the slits, and position of the slits relative to the pectoral fin were measured on approximately 45% of extant shark species with each order of sharks represented in the data set. Some factors that may be correlated with gill slit morphology were also investigated, including history, body type, and habitat. Four different gill slit length character states, two spacing character states, and five gill slit position character states exist among the species studied. Characters were mapped on an existing phylogeny to examine phylogenetic relationships. A principal components analysis (PCA) was performed to group the characters into descriptive units and explore relationships between the character states, habitats, and body types. Multiple character states exist among orders but are consistent within an order. This suggests that gill slit morphology is influenced by phylogenetic relationship. Slit length loads low on PC1, and body types one and four also load low on PC1. Slit spacing loads low on PC2 with only orectolobiform species in body type three loading low as well. The number of slits over the pectoral fin loads low on PC3 with only orectolobiform species in body type three loading low on PC3. No relationship among species by habitat was detected, nor was a relationship for body types two and three other than those found for the orectolobiform species in body type three. Some correlations among the three gill slit character states were detected; however, phylogeny is a better indicator of gill slit morphology than body type or habitat.