Reproductive biology

Most caenogastropods have a penis to copulate or to exchange spermatophores. The caneogastropod reproductive systems are complex. The male system typically consists of the testes, a prostate gland, and a vas deferens that leads to the penis, which is typically located on the right side of the head. The female system typically has two glands following the ovary: the albumen gland and the capsule gland. Also, there is typically a bursa copulatrix that receives sperm during mating and a seminal receptacle where sperm is stored prior to being used to fertilize the eggs. The addition of the albumen gland and the capsule gland is of special significance because nutritional resources can now be encapsulated with the eggs in the capsule. Egg size is reflected in the initial size of the juvenile shell, or protoconch, and this feature has been useful in distinguishing feeding and non-feeding larvae in both recent and fossil taxa—non-feeding larvae tend to have larger eggs than feeding taxa. The first gastropod larval stage is typically a trochophore that transforms into a veliger and then settles and undergoes metamorphosis to form a juvenile snail. In some caenogastropods, the young hatch as tro-chophores, grow into veligers, feed on maternally provided albumen, grow, and ultimately break through the capsule and crawl away. In other taxa, they may be released from the capsule as veliger larvae and feed in the plankton before settling and metamorphosing into juvenile snails. Both simultaneous and protandric hermaphrodites are present in the caenogas-tropods, although the majority of species are dioecious. In freshwater and terrestrial caenogastropods, direct development with crawl-away larvae is the norm.

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