INVESTIGATIONS OF PIGMENT GRANULE TRANSPORT-SYSTEMS IN GONODACTYLUS-OERSTEDII (CRUSTACEA, HOPLOCARIDA, STOMATOPODA) .1. EFFECTS OF LOW-TEMPERATURE ON THE PUPILLARY RESPONSE

Compound eyes of the stomatopod, Gonodactylus oerstedii, exhibit pupil lary reflection responses which arise from migration of retinular cell pigment granules. In the light, reflectance from the eye increases as pigment granules accumulate around light-sensitive rhabdoms and scatt er incoming light back out of the eye (pupillary closure). At dark ons et, reflectance diminishes as pigment granules disperse centrifugally, enhancing photon capture by the rhabdom. We investigated the mechanis ms of the pupillary response in intact animals by measuring reflectanc e from the eye under different temperature conditions. Lowering the te mperature from 27 degrees to 7 degrees C caused an increase in reflect ance of infrared light in the absence of visible-light stimuli, indica ting pupillary closure. When given light stimuli as temperature decrea sed, the eye continued to produce reflection increases which decreased in amplitude as the between-stimulus reflectance level increased. All low-temperature effects were reversed when temperature was increased to normal. The rate of pupillary closure was insensitive to temperatur e, with a temperature quotient (Q(10)) of 0.8 +/- 0.1 s.e.m, while pup illary opening was extremely temperature sensitive (Q(10) Of 5.4 +/- 0 .4). Different temperature sensitivities for pupillary opening and clo sing suggest that these processes involve different mechanisms.