P1.182 Wednesday, Jan. 4 Orientation Behavior and Possible Visual Statocyst in a Crustacean found in the Sonoran Desert: Triops (Branchiopoda: Notostraca) LESSIOS, N*; RUTOWSKI, R; Arizona State University email@example.com
Triops are branchiopod crustaceans found in ephemeral freshwater pools. As non-malacostracan crustaceans, they are often considered as basal for both crustaceans and hexapods (group including insects). Triops are mainly benthic foragers, but also swim to the air-surface boundary in hypoxic conditions. They have two compound eyes, as well as four median ocelli (naupliar eyes). They lack a corneal focusing lens. This study describes an inverted swimming behavior in response to a change in illumination from the hemisphere above the animal, to below. Responses are compared to animals in which black paint had been applied to the cuticle of their compound eyes and ocelli. Sections of their eyes and ocelli were analyzed using light microscopy to determine refractive index, focal length, and facet diameter of these structures. Orienting behavior is compared to photo-behavior in the horizontal plane using projected light in a rectangular trough. Their visual behavior is discussed in the context of mechanoreceptor statocysts. Many flying insects are known to use their ocelli for rapid body orientation corrections during flight, and their compound eyes for higher acuity vision, while some terrestrial insects use their ocelli for celestial cues. Understanding the adaptive significance of eyes in Triops and other non-malacostracan crustaceans will help to infer transitions in eye evolution, and will illustrate the diversity of extant insect-crustacean sensory systems.