Arana, MarieliseSulkin, Stephen2008-06-182008-06-181993-07Arana M, Sulkin S. 1993. Behavioral basis of depth regulation in the first zoeal stage of the Pacific shore crab, Hemigrapsus oregonensis (Brachyura: Grapsidae). Pac Sci 47(3): 256-262.0030-8870http://hdl.handle.net/10125/1766The behavioral basis of depth regulation is determined for the first pelagic larval stage of the shore crab Hemigrapsus oregonensis Dana. Larvae are negatively buoyant, passively sinking at 0.79 em/sec in 25 parts per thousand (ppt) salinity (S) seawater and at 0.67 em/sec in 30 ppt S. At 30 ppt S, larvae are negatively geotactic and move upward. At 25 ppt S, larvae remain negatively geotactic, but a low level of locomotor activity results in net downward movement. Swimming speed is higher at 30 ppt S than at 25 ppt S; however, there is no response to incremental increases in hydrostatic pressure up to 0.8 atm at either salinity. Behavioral responses should promote upward migration of the hatching stage similar to the case with other intertidal crab species; however, low precision in depth regulation contrasts with results from other species.en-USArticle