Facultative planktotrophy in the tropical echinoid Clypeaster rosaceus (Linnaeus) and a comparison with obligate planktotrophy in Clypeaster subdepressus (Gray) (Clypeasteroida: Echinoidea)

Abstract

Larval development to metamorphosis and early juvenile growth and survivorship were examined in Clypeaster subdepressus (Gray) and C. rosaceus (Linnaeus). C. subdepressus has an obligatorily planktotrophic larva that metamorphoses after 16 to 28 days at 27°C. The larva of C. rosaceus can, but need not feed prior to metamorphosis, which occurs after 5 to 7 days at 27°C. Feeding by larvae of C. rosaceus does not change the time to metamorphosis but does increase size at metamorphosis, early juvenile growth and may increase juvenile survivorship relative to unfed larvae. Size at metamorphosis increases in larvae of C. rosaceus that feed for several days after they are competent to metamorphose, but there may be a limit to this increase because the condition of the rudiment degenerates after a period of time. The development of C. rosaceus may represent a transition between planktotrophy and lecithotrophy. This intermediate state has advantages for the juvenile stage that are not included in the trade of fecundity against risk to offspring usually considered in life history discussions of developmental mode of marine invertebrates.