Reproductive biology of Pomacea bridgesii (Revee, 1857) (Gastropoda, Ampullariidae). I. Histology of the extraductal segment or vagina during the reproductive period

Abstract

Pomacea bridgesii (Revee, 1857) is a dioecious species with internal fertilization that spawns ovigerous whitish masses attached to aquatic emergent elements. In the paleal portion of the prosobranch gastropod oviduct, processes occur such as fertilization, oviposition and contribution to egg envelopes. The vagina is the last segment of the paleal region of the oviduct. The aim of this paper is to describe the histology of the vagina of P. bridgesii. The samples were processed for photon microscopy using routine histological techniques and his- tochemical stainings for carbohydrates. The wall of the vagina has three tunics: inner, middle and outer. The first or mucosae tunic presents folds constituted by a ciliated epithelium and glandular corium. Glandular contents are periodate reactive and alcianophilic at pH 2.5. The middle or muscular tunic is organized in two layers of smooth muscle separated with a lax connective tissue. The outer coat is a simple ciliated epithelial lining with intraepithelial multicellular glands and goblet cells. The former cells are negative to the tests used to detect mucosubstances whereas the latter reveal periodate-reactive contents and are acidophilic at pH 2.5 and 0.5 contents. The contraction of the wall muscle fibers and vaginal secretions contribute to the intraductal displacement of eggs and subsequent spawning