COATES, M.M.*; NILSSON, D-E; Hopkins Marine Station, Stanford University; Lund University, Sweden: An eye for each reason: the multiple eye types of a box jellyfish, Tripedalia cystophora

Like most jellyfish, box jellyfish (class Cubozoa) have small pit shaped ocelli. However, they also have camera-type eyes. Why does the box jellyfish have multiple eye types and what sort of information do the eyes pass to the nervous system? We hypothesize that each eye type is specialized to collect different sorts of visual information. Having specialized eyes for each type of information will reduce the amount of downstream processing needed from the rest of the nervous system. This will be advantageous in an animal like a box jellyfish with a relaitvely simple nervous system. Box jellyfish have four distinct eye types: a pigment cup ocelli shaped like a pit (pit eye), a pigment pit ocelli shaped like a slit (slit eye), a small lensed camera-type eye (small lens eye), and a large lensed camera-type eye (large lens eye). Combining optical measurements of lenses with morphological sections we calculated the spatial resolution of all eye types. The lenses of both the small and large lens eyes focus light behind the retina, leading to a low resolution image. Using an extracellular suction electrode technique we performed electroretinogram (ERG) recordings on both the lens eyes to measure temporal resolution and spectral sensitivity. Based on the morphological and electrophysiological resuts we propose functions for each of the different eye types. We propose that the large lens eye detects the motion of low resolution objects, such as mangrove roots, as the medusa drifts with a current. The small lens eye may be involved in the detection of light shafts in the water where prey items are known to congregate. Finally the pit ocelli are most likely involved in gauging depth, with the pit eye detecting the water surface and the slit eye detecting the seafloor.