Meeting Abstract
P3.81 Saturday, Jan. 5 Osmoregulation by Fiddler Crabs (genus Uca) from the Northern Caribbean THURMAN, Carl L. *; HANNA , Joshua M. ; BENNETT, Chad R.; University of Northern Iowa, Cedar Falls thurman@uni.edu
The ability to regulate the osmolarity of internal body fluids has not been examined in many species of Caribbean fiddler crabs. Nine species of Uca were collected from 17 locations in Belize, the Bahamas, Jamaica, and the U.S. Virgin Islands in the Greater Antilles. Habitat osmolality ranged from 18 to 2760 mOsm (0.6 to ~87 o/oo). Each species was associated with a distinct mOsm range: mordax 18-386, burgersi 34-1149, vocator 122-386, rapax 386-2760, thayeri 924-1088, cumulanta 1037, major 1129, speciosa 1149, leptodactyla 99-1149. Crabs were flown to a laboratory in Iowa to study their osmoregulating ability in 30 to 3550 mOsm (~1 to ~113 o/oo) over 5 days. Osmolality was measured using vapor pressure osmometry. For each population and species, survivorship, lower and upper median lethal concentrations (LC50), and hemolymph isotonic concentration ([ISO]) were estimated. Since some survived 5 days in deionized water, a lower LC50 could not be calculated (-) in every case. The lower and upper LD50s are estimated in mOsm as: mordax: – & 1619; burgersi: – & 2566; vocator: – & 1993; rapax: – & 3373; thayeri: 85 & 2090; leptodactyla: 58 & 2857; cumulanta: 58 & 2194, speciosa: – & 2958; major: 91 & 2672. Considering the Uca by subgenus, average [ISO] for Minuca ranges from 587 to 768 mOsm while for Leptuca it ranges from 805 to 881 mOsm. The [ISO] for thayeri and major is 805 and 930 mOsm, respectively. Furthermore, the mean [ISO] for each species reflects a preference for either an oligo-, meso-, or euhaline habitat. This study broadens our understanding of ecological physiology in Caribbean Uca and demonstrates intra- and interspecific differences among their tropical populations.
