Studies on The Biology of The Entocommensal Rhynchocoelan Malacobdella Grossa

Abstract

IntroductionDespite the amount of literature published concerning the entocommensal rhynchocoelan, Malacobdella grossa (O. F. Müller), few references have been made about its ecology and life-history, and these for the most part consist of little more than isolated observations. The ecological knowledge available is composed almost exclusively of details pertaining to geographic distribution, hosts from which the worm has been recorded, and reports of the infection incidences found. Apart from suggestions by von Kennel (1878) and Gering (1911) that a relationship exists between host size and both worm incidence and size, the only detailed analysis of the host-commensal associations is that of Gibson (1967), who established a statistical correlation between host size and both incidence of infection and nemertean length, recorded the disposition frequency of the worm within its host, and examined both the occurrence of multiple infections and the Malacobdella population size composition.Von Kennel (1878) further suggested that host-commensal size relationships would depand on the age (i.e. size) at which infection by the pelagic larvae occurred, and Ropes (1963) speculated on the role played by surface currents upon larval distribution.