The Effect of Starvation on Broodstock during Egg Capsule Incubation and Early Shell Formation in the Common Atlantic Slippersnail Crepidula fornicata L.

Abstract

ABSTRACT In this work, an inadvertent discovery revealed that the prolonged starvation of brooding Crepidula fornicata L. caused the irreversible shell loss of the offspring. This study hypothesized that the shell loss resulted from the hypoxia suffered by the embryos during the incubation period, given that if a brooding snail is starved, the pumping rate is reduced, producing a drop in oxygen diffusion through the egg capsule walls, and thus hypoxic conditions in the intracapsular environment occur. As a result, the embryos trapped within the capsules suffer hypoxia and are forced to shift into anaerobic metabolism to survive, producing CaCO3 destined for the shell to be alternatively used as a pH buffer during metabolic acidosis. Under these sublethal conditions, embryos continue their development until hatching. The resulting shell-less larvae continue their free-swimming period and undergo metamorphosis to give way to crawling radula-feeder juveniles. Several experiments were carried out to test this hypothesis. First, the reduction in the pumping rate of starved snails (13.3±0.3mL h–1) was confirmed compared with fed snails (31.6±0.3mL h–1). The calcium content of larvae from egg capsules from fed and starved snails was 537.4 and 125.4 ngCa µgdtw–1, respectively. To simulate conditions inside the mantle cavity of the mother, groups of detached egg capsules were exposed for 24 days to different water flows in open-flow glass chambers. The results indicated egg capsule survival of 93% and 83% at flow rates of 197 and 103mL h–1, respectively. Total capsule mortality was found on days 12 and 15, at 16 and 811mL h–1, respectively, indicating a flow range for the normal development of the encapsulated embryos and larvae. Morphological features of embryos, larvae, and juveniles from fed and starved brooding snails were compared using a scanning electron microscope. The results supported the original hypothesis that starvation of adult egg-bearing C. fornicata results in irreversible shell loss in offspring.