Aspects of the biology of Isactinia olivacea (Hutton, 1878)

Abstract

A species of olive green sea anemone, Isactinia olivacea, collected along the mid-tidal sea shore of Island Bay, Houghton Bay and Shelly Bay in Wellington, and also Governor's Bay in Lyttelton Harbour is described. The systematic relationship of the species is reviewed. A description of the internal and external morphology is presented in detail. An account of verruco-cinclides acting as reproductive pores and sustentacular cells of Sertoli in Isactinia olivacea is given. The gland cells not previously recorded from actinians are described. The mode of development of tentacles and mesenteries is reported and shows that the radial symmetry arises from a bilateral symmetry due to a slow growth of tissue. Excretion of unused waste was found to be limited to the band of cells in the mesenteric filaments. Digestion is proved to be partly extracellular and partly intracellular like most actinia. Chemoreception is extensive in Isactinia olivacea due to the presence of numerous receptors on the tentacles as well as in the verruco-cinclides of the body wall. Variation of the body nitrogen content and therefore protein percentage fluctuates seasonally. The chemical factors involved in asexual reproduction are described from histochemical tissue studies. The location of alkaline phosphatase and its probable relation to nematocysts production is recorded.