title: Redescription of Syndesmis echinorum François, 1886 (Turbellaria: Neorhabdocoela: Umagillidae), with comments on distinctions between Syndesmis and Syndisyrinx.
abstract: Syndesmis echinorum is redescribed from specimens taken from the intestine of the sea urchin Paracentrotus lividus at the type locality, Banyuls-sur-Mer, France. This umagillid is shown to have a seminal bursa-bursal valve complex comparable to that of Syndisyrinx franciscanus. Thus, it is suggested that the genera Syndesmis and Syndisyrinx be distinguished on the basis of the form and proportions of the ejaculatory duct, male antrum, and penis stylet, rather than on the basis of the presence or absence of a seminal bursa and bursal valve. The sea urchin Sphaerechinus granularis at Banyuls harbors a worm that is, on the average, slightly more robust than S. echinorum from P. lividus; its morphology, however, agrees with that of S. echinorum. In addition to S. echinorum, P. lividus harbors at least 1 undescribed umagillid. Although 2 species found in Echinus esculentus have been referred to S. echinorum by previous workers, neither is conspecific with it.
mesh_terms: D000818:Animals; D005260:Female; D005837:Genitalia, Male / Q000033:anatomy & histology; D007422:Intestines / Q000469:parasitology; D008297:Male; D012617:Sea Urchins / Q000469:parasitology; D014419:Turbellaria / Q000033:anatomy & histology* / Q000145:classification; D014599:Uterus / Q000033:anatomy & histology; D014621:Vagina / Q000033:anatomy & histology