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This study describes the reproductive cycle in the edible marine snail Zidona dufresnei in San Antonio Bay (Patagonia, Argentina), an unusual population that inhabits shallow waters. Histological techniques together with monthly field observations over a two-year period were used to describe the gametogenic cycle, the season of oviposition and the presence of egg capsules. Females were mature from August to April and there was proliferation of the germinal epithelium immediately after evacuation. Growth and resorption of oocytes were observed throughout the study period. Males were reproductively active throughout the year. The histological analysis is consistent with the observations in nature, in which females were recorded depositing egg capsules from late August to late April. The reproductive period seems to be closely related to water temperature and photoperiod. The relatively high seawater temperature in San Antonio Bay may be one of the relevant factors that contributes to the extended period of oviposition and gamete evacuation in Z. dufresnei. [ABSTRACT FROM AUTHOR]

The sperm morphology of Adelomelon beckii is described by optical and transmission electron microscopy. Both euspermatozoa and paraspermatozoa were found in the specimens studied. Euspermatozoa are filiform and have an elongate nucleus capped by an acrosome. A small basal plate lies between the base of the acrosome and the nucleus. The mid-piece consists of U-shaped mitochondria wrapped helically around the central axoneme. A dense annulus at the junction of the mid-piece and glycogen piece is found, ending in a short end-piece, composed of the axoneme surrounded by a plasma membrane. Two types of paraspermatozoa are found, both vermiform but differing internally with respect to the disposition and number of axonemes, as well as to the types of secretory vesicles. We suggest the use of paraspermatozoa as a systematic character to reveal phylogenetic relationships in this family. [ABSTRACT FROM AUTHOR]