Prosthiostomum siphunculus

Overview & Synopsis

Prosthiostomum siphunculus (Delle Chiaje, 1822)(Figs. 7A and 9F)Material examined. Three mature specimens, 22.10.2013, station M5, 5 m deep. Three mature specimens, 22.10.2013, station M3, 5 m deep. Two mature specimens, 21.01.2014, station M2, 4 m deep. Two specimens, 02.07.2014, station M1, 5 m deep. One specimen, station M4, 4 m deep. The area of the reproductive structures was separated and sagittally sectioned in two specimens (3 slides and 4 slides).Description. Body elongated with rounded anterior and pointed posterior margins. The cerebral eyes in two clusters. The marginal eyes encircle the anterior body margin not exceeding the level of cerebral eyes (Fig. 8F). Preserved specimens ranging 8–13 mm long and 2–3 mm wideDigestive system. Tubular plicate pharynx housed in a pharyngeal pocket extending from behind the cerebral organ to the level of reproductive apparatus. Main intestine extending distally up to the level where the body starts tapering posteriorly.Reproductive system. The paired vasa deferentia lead to the oval-shaped seminal vesicle, which opens to the ejaculatory duct. The latter also receives the sinuous prostatic ducts from two spherical prostatic vesicles (Fig. 6B). The horizontally oriented male antrium houses a penis armed with a tubular stylet. Sucker behind the female gonopore.Female apparatus characterized by a short external vagina followed by a wide cement pouch (Fig. 6B), hence immersed in a dense mass of cement glands. The vagina continues dorsally, and before reaching the median intestine, turns posteriorly, where the internal vagina connects to the paired oviducts. Lang’s vesicle lacking.