Schistosoma mansoni Infection Inhibits Maturation of Ovotestis Allografts in Biomphalaria glabrata (Mollusca: Pulmonata)

Abstract

The posterior tip of juvenile snails, consisting of immature ovotestis, vesicular connective tissue, and digestive gland acini, all surrounded by body wall, was implanted into the hemocoel of allogeneic adult Biomphalaria glabrata. Recipient snails were either uninfected or had been infected 15 days previously with Schistosoma mansoni. Graft recipients were dissected at 30 or 60 days postimplantation (DPI), and the implants, along with preimplantation controls, were examined histologically. The gonads in preimplantation controls consisted of a partially coiled collecting canal partitioned dorsally by connective tissue septa and contained mainly spermatogonia-like cells and small oocytes. In uninfected recipients, implanted gonads underwent rapid development, i.e., had formed mature acini and were carrying out vigorous gametogenesis, both spermatogenesis and oogenesis, by 30 DPI. At 60 DPI, numbers of spermatozoa had increased substantially in most implants. In infected recipients, relatively little development or gametogenesis occurred at either 30 or 60 DPI, and oogenesis was more strongly inhibited than spermatogenesis. Except for 1 implanted gonad (out of 25) that had undergone necrosis at 60 DPI and a second otherwise healthy 60-day implant partially encapsulated at its cut surface (both in uninfected recipients), no significant hemocytic response occurred against the allografts.