An introductory survey of ecology and sensory receptors of tropical eastern pacific crustaceans

Abstract

A comparative survey of sensory organs (mainly visual) of 35 species of crustaceans (Mysidacea, Stomatopoda and Decapoda) was initiated in the SE Gulf of California, Mexico, an enclosed sea which has been well studied for its physical conditions and the taxonomy of crustacean species. The purpose of this survey was to study how the perceptive capacities are conditioned by the signals arriving from their environment. Studied species were sampled from terrestrial, intertidal, subtidal and deep sea habitats. Our data indicate that down to 200 m there seems to be not much difference of skewing patterns in stomatopods. Eyes are adapted to local conditions. In crabs and stomatopods, ommatidia are aligned in a vertical array along the longer axis of the eye. Visual fields of ommatidia overlap. This could emphasize, for instance, the horizontal motion of vertical edges. Deep‐sea crustaceans still have eyes, but in the same habitat species with apparently functional eyes occur together with species with strongly reduced eyes. When eyes are reduced, nervous structures are still observable but not ommatidia. Almost all species studied have extra‐organs in the eye. These are mechano‐(crabs) or chemo‐ (deep‐sea crustaceans) receptors or else organs which seem to have a specific (e.g. adaptation) visual task (shrimps). All extra‐organs have small ganglia and nerves contacting the visual ganglia on their way towards the brain.

Key words:

• Crustacea
• Ecology
• Taxonomy
• Vision
• Sensory organs
• Deep‐sea