Costs of parental care in the gastropod Conus pennaceus: Age-specific changes and physical constraints

Age-specific changes in the allocation of reproductive energy to protective capsules, ova and intracapsular fluid are documented for the marine gastropod Conus pennaceus. As female snails grow in shell length they produce larger capsules with thicker and stronger walls. Because large capsules contain lower densities of ova than do small ones, growing females must increase the number, as well as the size, of egg capsules they produce. As a result of this pattern of ova packaging, per ovum costs of encapsulation (parental care) increase with increasing female size and age. The data suggest that the number of embryos a capusle can support may be limited by respiratory constraints related to capsule surface area or wall thickness. As capsule size increases, surface/volume ratios decline and capsule wall thickness increases. Either of these processes should result in a reduction in net gas transport per unit of capsule contents.