FIGURE 5 in The Antarctic holothurian genus Echinopsolus Gutt, 1990 (Dendrochirotida, Cucumariidae): brood pouches, spermatozoa, spermatozeugmata and taxonomic implications

FIGURE 5. Schematic reconstruction of sperm ultrastructure of Echinopsolus splendidus. a. Longitudinal section of sperm head with acrosomal complex, diplosome with satellite complex and cylindrical mid-piece with mitochondrial ring and mitochondrial cylinder wraping basis of flagellar sperm-tail. b–g. Cross sections. b. Rim of the anterior nuclear depression with embedded acrosomal vesicle. c. Periacrosomal mass. d. Electron dense nucleus with small electron light "vacuole". e. Distal centriole (9 x 3 + 0 tubular arrangement) with satellite complex and subnuclear mitochondrial ring. f. Jacket-shaped mitochondrial derivative encircling flagellar tail-base. g. Flagellar tail. a—acrosomal vesicle; cf—centriolar fossa; cm—cell membrane; dc—distal centriole; f—flagellum; mc—mitochondrial cylinder; mr—mitochondrial ring; n—nucleus; p—periacrosomal material; pc—proximal centriole with fibrous arm; sc—satellite complex; v—nuclear vacuole; x—extracellular space within the mitochondrial cylinder.