COMPARATIVE-ANALYSIS OF ESCAPE BEHAVIOR IN MALE, AND GRAVID AND NONGRAVID, FEMALE LOBSTERS

Few studies exist in which the parameters of a single behavior have be en quantitatively compared for male and female lobsters. Here, we have examined the effects of sex and gravidity on the parameters of the es cape behavior of the American lobster, Homarus americanus, elicited by a visual threat. Both non-gravid females and male lobsters readily ta il-flipped in response to the stimulus, but gravid females failed, wit h one exception, to initiate a swim, even when stimulus strength was i ncreased. Although the total distance swum by males and nongravid fema les was not statistically different, males covered more ground in the initial power swim and during the subsequent swims than did non-gravid females. Males swam for a longer time, performing more tailflips, tha n females. Relative to their length and weight, males swam a greater d istance at each stroke during the initial power swim and the subsequen t swims, although, females might have compensated by swimming at a hig her frequency. There were no significant differences in swimming veloc ity or acceleration, nor in the calculated force or work performed by the two sex classes (male and non-gravid females). Therefore, apart fr om egg-bearing, which severely inhibits the escape response, it remain s to be seen whether the subtle physiological and anatomical sexual di morphism that produces longer and more swim strokes in males but highe r frequency tailflips in females results in the same chances of surviv al for the sexes.