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Embryonic cannibalism has been identified in directly developing calyptraeid species through observation of the ingestion of encapsulated sibling embryos. The object of the present study was to determine the effects of experimentally induced cannibalism on larval development in encapsulated larvae of Crepipatella fecunda (a species having mixed development). The effects studied included the time of intracapsular development, protoconch size and velar characteristics of the larvae. Mortality was induced during intracapsular development through mechanical disruption (‘treatment’) of embryos. A treatment and control group of embryos from the same female were compared. Encapsulated veligers actively fed on their sacrificed congeners. Larvae hatched in less than 10 days from treated capsules and had mean shell lengths and velum areas significantly lower than those from the control, but no significant differences in cilia length. In treated capsules where the embryos underwent a slow development (>20 days), the larvae produced shells, vela and cilia larger than those of the controls. In an intermediate period of intracapsular development, the differences recorded among larval characters were not statistically significant. The results showed that: (1) the encapsulated veligers were capable of feeding on exogenous food before hatching; (2) the consumption of non-living congeners decreased the time of intracapsular development; and (3) the morphometry of the larvae hatching from treated capsules varied depending on the period of intracapsular development and seems to be adaptively stabilised towards homogeneous larval morphometry.

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Crepipatella fecunda is a benthic, primarily suspension-feeding gastropod that occurs in great abundance along the Chilean coast. It is a protandrous species whose reproduction involves brooding of an encapsulated embryonic stage followed by the release of free-living planktotrophic larvae. Because its close sister species, C. dilatata, co-occurs with C. fecunda, understanding the details of reproduction in this species might shed light on differences in reproductive features that correlate with divergences in mode of development. In southern Chile, brooding occurs throughout the year except for May and June, and each female produces 3–7 broods. The smallest brooding female was 28·2 mm in shell length and the largest was 56·3 mm. All full-grown eggs from the ovary are deposited at one time in a single brood, and only smaller oocytes remain in the gonad after the female finishes ovopositing. Those females that host pinnotherid crabs do not deposit eggs. All the eggs develop into embryos whose intracapsular development is similar to Crepidula fornicata and Crepipatella lingulata. Planktotrophic larvae hatch at a mean shell length of 329·5 μm (SD=27·09) after 4–5 weeks. During the pelagic stage the shell and velum of the larvae grow, but little other morphological development is visible externally. The pelagic stage lasts for 15–16 days at 17°C, during which the larvae grow ∼20·7 μm d−1. Observations of cultured larvae and protoconchs of field-collected juveniles show that settlement occurs when the larvae reach a shell-length of 650 μm (SD=28·3 μm).

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Embryos of Crepidula dilatata develop within egg capsules where they feed on nutritive eggs also deposited within the capsules. Nutritive eggs permit the embryos to develop to a juvenile stage at hatching without passing through a pelagic larval phase. The juveniles enter the local population in posession of a well developed radula and gill filaments covered by lateral, ventral, and dorsal cilia. Initial feeding by the juveniles, employing both the radula and the gill, occurs from the first day of release from the capsule. The radular band of recently hatched snails is functional from the first day in the benthos, and is used for grazing the substrate, driving the mucus cord from the neck-canal to the mouth, and also for extracting mucus balls produced in the food pouch. The gill is active in particle collection from the first day of the free living juvenile, and is noted by the presence of well developed dorsal and ventral ciliature, active in moving mucus and particles over the gill lamellae to form the mucus string at the extreme ends of the gill filaments. The food pouch becomes active two to three days after initiation of production of mucus cords. All the functions associated with feeding, such as the numbers of mucus cords, radular strokes, and mucus balls increase in activity with progressive development of the juveniles.