Paravortex scrobiculariae (Graff) in Great Britain

Abstract

THE genus Paravortex was established by Wahl¹ for a vorticid Rhabdocoele living in the intestine of the lamellibranch Scrobicularia plana. Three species are now recognized with some certainty, all associated with bivalve molluscs. Paravortex (= Graffilla) gemellipara (Linton) lives as a commensal in the mantle cavity of the American ribbed mussel, Modiolus demissus ^2,3; P. cardii Hallez in the stomach of the common cockle Cardium edule ⁴ and P. scrobiculariae (Graff) in the intestine, and occasionally also in the stomach, of Scrobicularia plana. All three species are viviparous, the eggs developing in thin-walled capsules embedded in the mesenchyme of the mother. The embryos escape by passing across the maternal tissues, and, after a short free-living period, reinfect another, or perhaps the same, host.