Portal de Periódicos da CAPES

The significance of terminal duct structures and the role of neoteny in the evolution of the reproductive system of Pulmonata

1988; Wiley; Volume: 17; Issue: 3 Linguagem: Inglês

10.1111/j.1463-6409.1988.tb00099.x

1463-6409

MATTHYS H. C. VISSER,

Aquatic Invertebrate Ecology and Behavior

A comparison of the adult morphology, in conjunction with the ontogenetical development, of the terminal reproductive system elements of Pulmonata yield the following information. Basom‐matophora and Systellommatophora are, in the retention of embryonic ditremy in adult conditions, completely neotenous (paedogenetic). In Basommatophora a ditrematic semi‐diaulie to ditrematie diaulic lineage is apparent; a sequential monotrematie monaulie (Glacidorbidae) to simultaneous monotrematic monaulic (Siphonariidae) lineage, as a divergent condition, is proposed. The Systellommatophora, in view of similarities in proximal pallial duct development, are considered to be more closely related to Stylommatophora. Embryonic Stylommatophora recapitulate a ditrematic condition, but later ontogenetic stages, as well as adult morphology, indicate the establishment of a (primarily) semi‐diaulic monotrematic system. The posterior ‘female’ position and anterior ‘male’ position of the genital orifice indicate an inherent divergent development in Stylommatophora. A series depicting possible trends in terminal duct development of Stylommatophora with anterior ‘male’ position gonopore is reconstructed from an analysis of the various (gross) features present. The genital systems with female properties resulting from apomixis take a terminal position in this series. Pulmonate. reproductive systems are regarded as having developed from intermediate stages in the life cycle of a sequential protandrous prosobranch ancestor.