Directional orientation in blue crabs, Callinectes sapidusRathbun: Escape responses and influence of wave direction

Blue crabs invade the upper intertidal at high tide and exhibit rapid, directed locomotory movements (i.e., escape response) which are significantly oriented offshore. The direction of wave surge and beach slope are conservative features of the intertidal, indicating offshore direction and can be used by blue crabs as orientation cues. Temporarily blinded crabs in the intertidal zone oriented down-slope (2–3°) and into the wave approach (up-wave) in experimental field test arenas. Up-wave orientation acuity increased in the presence of larger waves. Experiments in a wave test tank showed that orientation occurred over a wide range of surge velocities dependent upon threshold levels of surge displacement. We believe that the oriented response to wave surge serves as an important adaptation for movements by blue crabs in the nearshore zone.