Analysis of reproductive energetics of Florida Opisthobranchia (Mollusca: Gastropoda)

Abstract

Egg masses of 31 species of Florida opisthobranch molluscs were analyzed to determine relationships among caloric contents of egg masses and adults, reproductive effort (caloric and gravimetric), and three developmental patterns (type 1—planktotrophic; type 2—pelagic lecithotrophic; and type 3—encapsulated metamorphic). Absolute (total calories per egg mass) and relative (calories per adult calorie) reproductive output were independent of development type, but were higher for small species than for large species. Caloric content per egg (including associated albumen, matrix, and capsular components) significantly differed between types 1 and 3, but not between types 1 and 2 nor types 2 and 3. Calories per egg and number of eggs per mass varied inversely (P < 0.01), but regressions for the three types did not differ significantly in either slopes or intercepts. Egg capsule volume increased as a function of species' body size. Energetics factors seem to have little effect on selection of developmental pattern in opisthobranch reproduction. Instead, other ecological considerations (trophic stability and dispersal requirements) probably control developmental patterns. Opisthobranch eggs show wide variability in caloric content, partially due to egg size, but probably vary as a result of accessory components of the egg mass (capsule walls, jelly matrix, albumen) as well. High caloric content of some planktotrophic eggs may relate to flexibility of development, as noted in other studies, and may increase fitness of planktotrophic larvae.