The cubomedusae: a review of the literature and the histology of the rhopal ium

Abstract

A review of the literature of the Cubomedusae with special reference to that related to their systematic status is presented in Part I. Part II describes the morphology and histology as seen by light and electron microscopy of the rhopalium and rhopalial niche of Carybdea alata Reynaud 1830, Carybdea rastoni Haacke 1886, Carybdea sivickisi Stiasny 1926, Chironex fleckeri Southcott 1956, and Chiropsalmus quadrigatus Haeckel 1880. Conclusions reached are as follows. The shape of the rhopalium and rhopalial niche differs in each of the species examined and is similar in general terms to the shape of the bell; the basic morphology and histology of the rhopalium is similar in the five species but there are differences in the size of the two median eyes, the lens structure, the vitreous body and vitreous humour and type of retinal cells present. These findings have been compared with those of Conant (1897, 1898) and Berger (1898, 1900). A major difference in interpretation relates to the vitreous body and the type of retinal cells present. The vitreous body is a distinct entity and not part of the retina proper as described by Berger and Conant. Four types of retinal pigment cells are identified in the distal complex eye - long and short pigment cells and Type A and Type B receptor cells and two only (short pigment cell and Type B receptor cell) in the proximal complex eye.