Studies on the anatomy, life history and behaviour of Marsupiobdella Africana (Hirudinea: Glossiphoniidae)



All glossiphoniids afford some degree of protection to both eggs and young but Marsupiobdella africana is unique in that it develops a permanent brood pouch on the ventral surface. Developmental and histological studies show that the marsupium is epidermal in origin. The pouch rudiment forms as a shallow groove before the eggs leave the ovisac and, when functional, the pouch becomes enormously distended reaching from oesophagus to anus and considerably compressing the internal organs. Its opening is a narrow sphinctered pore which apparently permits some degree of parental control over the release of the brood.

The course of the life history has been established from natural and experimental infestations of M. africana on the Clawed toad, Xenopus laevis laevis, from the Cape, South Africa. The leeches develop to maturity over a period of two to three weeks (at 22°C) whilst attached to the host, but copulate only after detachment. Present evidence suggests that the embryos are transferred externally from female gonopore to the pouch within which up to 50 young are brooded for about four weeks. The juveniles are relatively well developed at the time of their release; they can be carried in the pouch at an infective stage for up to two months and when contact with X. laevis is made they are discharged explosively. Each leech reproduces once, dying after a maximum life span of about four months. Other Xenopus toads (X. laevis victorianus and X. vestitus), were successful hosts in specificity tests, but Rana and Bufo species were not infected, nor were tadpoles of Xenopus.

Marsupiobdella has a number of unusual anatomical features in addition to the brood pouch. The oesophageal organ is described in some detail; its cells are either glands or mycetocytes. The forward displacement of the anus cannot be explained on either functional or phylogenetic grounds. The presence of the velum is unique amongst glossiphoniids and probably the most significant peculiarity in that it affords evidence for the phylogeny of the group.