Meeting Abstract

P1.26  Monday, Jan. 4  Eye development in the box jellyfish Carybdea marsupialis VALLEY, Jenna R.*; MARTIN, Vicki J.; Appalachian State University; Appalachian State University valleyjr@appstate.edu

Cnidarians (including hydras, jellyfish, sea anemones and corals) are the most primitive invertebrates alive today to possess eyes. Referred to as ocelli, the eyes of the cubozoan Carybdea marsupialis are arranged in 4 groups of 6 on club-shaped structures called rophalia found suspended from each of the four sides of the bell. The ocelli consist of 2 sets of simple eyes, referred to as the slit and pit ocelli, and 1 set of complex camera-type eyes which exhibit many similarities to the camera-type eyes of higher metazoans. The development of the eyes can be followed as an adult polyp transforms to the medusa (jellyfish), the eye-bearing form. This transformation can be stimulated by an increase in water temperature in combination with a cessation of feeding. In following the transformative process, 8 morphological stages were identified using light microscopy and accompanying scanning electron microscopy. Starting with a steady-state polyp (stage 0), the main features of transformation include recession of polyp tentacles, a change of symmetry from radial to tetraradial, eye development, emergence of medusa tentacles, and detachment (stage 7). The first eye spot can be seen by 4 days after beginning the process and by day 14, the polyp has formed a free-swimming medusa with miniature versions of adult ocelli. The first ocelli to appear are the large complex eyes, followed by the small lensed eyes and lastly, the simple ocelli. In addition, it was observed that transforming polyps with late-forming eyes were able to regress back to the original polyp state, which lacks eyes, under varying conditions.