FUNCTION OF CHEMORECEPTOR ORGANS IN SPATIAL ORIENTATION OF THE LOBSTER,HOMARUS AMERICANUS:DIFFERENCES AND OVERLAP

Abstract

Three of the lobster's main chemoreceptor organs, the lateral and medial antennules (representing smell) and the dactylus-propodus segments of the walking legs (representing taste), are physiologically quite similar. We examined their role in spatial orientation in a food-odor stimulus field. Control animals almost always oriented correctly and immediately to an odor plume. Lobsters with unilateral ablations of lateral antennules lost this ability, but did not show preferential turning toward the intact side. Unilateral medial antennule ablation did not affect orientation. Removal of all aesthetasc hairs from one lateral antennule caused loss of orientation ability less severe than unilateral ablation of the entire lateral antennule. Lobsters with unilaterally ablated lateral antennules and blocked walking leg receptors turned preferentially toward the side of the intact antennule. Thus, it appears that intact lobsters orient in odor space by tropotaxis principally using aesthetasc receptor input. The first two pairs of walking legs and non-aesthetasc receptors on the lateral antennule have additional roles in spatial chemical orientation. The medial flagellum does not contribute to orientation. Since loss of appendages is relatively common in lobsters, this partial overlap of organ function may serve the animal well in nature.