Ultrastructure of the eyes of the larva of Neoheterocotyle rhinobatidis (Platyhelminthes, Monopisthocotylea), and phylogenetic implications

The oncomiracidium of Neoheterocotyle rhinobatidis (Monogenea, Monopisthoco tylea, Monocotylidae) has two pairs of eyes, each eye with a lens and pigme nt cup. The anterior eyes have a single rhadomere; the posterior ones, two rhadomeres. Lenses are part of the pigment cup cells, as indicated by cytop lasmic connections between them and the pigment cups, and they are of mitoc hondrial origin because mitochondrial cristae are present in the periphery of the lenses. This is the first time that mitochondrial lenses have been s hown to exist in a neodermatan. Such lenses may be a synapomorphy of a larg e taxon comprising the Neodermata and its turbellarian sister groups, or th ey may have evolved convergently in several not closely related groups as a result of strong selection pressure to find a suitable habitat or host. (C ) 1999 Australian Society for Parasitology. Published by Elsevier Science L td. All rights reserved.