A DICHOTOMOUS KEY TO IDENTIFY OSTRACODES FROM THE BAHAMAS

Ostracodes as a class of crustacean that provide an excellent way to indicate past climates and study evolutionary biology. Differentiating between the twenty-nine species sampled in the lakes from three Bahamian islands: Rum Cay, San Salvador, and New Providence, for more inexperienced individuals proves to be difficult and presents a need for a dichotomous key to quickly decipher between them. The first step in drafting this key was to create an updated trait by species matrix using the specimen from all twenty-nine species. Kesling (1951) was used in order to standardize the terminology of traits we identified on the ostracodes carapace. It became apparent that the easiest traits to identify were the parts of the carapace that extended outwardly, including denticulation, tubercules, caudal process, ala, nodes, and spines. Many of the traits, like margin and overall shape, were difficult to set objective standards for so were assessed relative to other species. Of the twenty-nine sampled species available, we were able to include twenty-four (eighty-three percent) in the initial draft of the species key. Other undergraduate students were able to identify unknown specimen to species using the dichotomous key created using these twenty-four species. A knowledge of species’ traits enables us to test hypotheses about evolutionary history and relationships of traits to environment. For example, Propontocypris multiporifera, sampled in brackish waters, and Paracypria inopinata, a euryhaline species, are nearly identical except for the shapes of their dorsal and posterior margins. Perhaps the curved ventral margin of Pa. inopinata is an adaptation for living in a broader range of salinity, while the straight ventral margin of Pr. multiporifera could be an adaptation for brackish water. This dichotomous key will be used to identify species sampled from modern samples and sedimentary archives (“cores”) sampled from Rum Cay, San Salvador, and New Providence in order to generate paleoclimate records from the Bahamas.

Kesling, R.V., 1951. Terminology of Ostracod Carapaces. Contributions from the Museum of Paleontology of the University of Michigan IX: 93-171.