MORPHOMETRIC AND ECOLOGICAL DISCREPANCIES OF LUCINIDAE (BIVALVIA) IN VARIOUS MARINE ENVIRONMENTS ON SAN SALVADOR ISLAND, THE BAHAMAS

Lucinid bivalves (family Lucinidae) are abundant members of shallow infaunal seagrass communities in the tropical Western Atlantic. Lucinid chemosymbiotic associations with sulfur-oxidizing bacteria contribute to the sulfur cycle of a habitat. In addition to open ocean seagrass environments along the coast of San Salvador, The Bahamas, live lucinid Ctena orbiculata were recovered from two inland lakes with marine salinity. The inland populations have not been investigated previously, but the lakes may serve as promising evolutionary “islands,” wherein chemosymbiotic bivalves have independently evolved since the last glacial minimum and have existed under unique conditions. The goals of this study were to compare the morphology and ecology of the inland lake C. orbiculata to those recovered from open ocean environments. The only live lucinid recovered from the lakes was C. orbiculata, but four open marine localities across San Salvador Island that were sampled from 2015-2016 had live C. orbiculata, Codakia orbicularis, Lucina pensylvanica, and Divalinga quadrisulcata. Morphometric analyses suggest that C. orbiculata dimensions varied across all environments, with the most notable differences occurring among each of the lakes and all open ocean settings. Generally, bivalve size and the presence of predation were correlated. Specifically, lucinids from open ocean sediments were smaller, had relatively thicker shells, and had a high risk of predation, as evidenced by the presence of predatory gastropod boreholes. In contrast, lake sediment specimens were larger, had thinner shells, and lacked evidence of drilling predation. One of the open water settings, at the distal end of a tidal estuary, was similar to the marine lakes because of few signs of predation and having larger shells. Isolated marine habitats, such as tidal estuaries and inland marine lakes, may have ecological, and possibly evolutionary, consequences on C. orbiculata populations. More inland marine lakes on San Salvador need to be investigated for lucinids.