Hesiolicium gen.n. (Turbellaria Acoela) and Observations on Its Ultrastructure

Abstract

AbstractCrezée, M. (University of Florida Marine Laboratory, Gainesville, FL 32611, USA) and Tyler, S. Hesiolicium gen.n. (Turbellaria Acoela) and observations on its ultrastructure. Zool. Scr. 5 (5): 207–216, 1976. —Hesiolicium inops gen.n., sp.n. is a thin and elongate protandric hermaphrodite from the marine interstitial environment. The male pore, with no accessory organs, lies just posterior to the mouth, with no pharynx. The dorsal ovary, lateral testes, adhesive papillae and a caudal organ are other features. The posterior and midventral adhesive papillae are bundles of haptocilia up to 22 μm long. In a crook near their base these adhesive cilia have three microtubule doublets displaced from the rest of the axoneme, giving the crook region a figure‐eight cross section. The caudal organ is a complex of cilium‐bearing sensory cells, large gland cells and modified muscle and epidermal cells. The rootlets of epidermal cilia and the two axial units of the sperm are as described for other acoels. Principally because of the haptocilia, Hesiolicium is provisionally placed in the Paratomellidae.