REPRODUCTIVE EFFORT: ITS DEFINITION, MEASUREMENT AND INTERPRETATION IN RELATION TO MOLLUSCAN LIFE-HISTORY STRATEGIES

The concept of reproductive effort, as a construct of life-history theory, is defined and considered especially in relation to the differing larval reproductive strategies displayed by the nudibranch mollusca. Energetic data for four nudibranch species suggest a causal relationship between magnitude of reproductive effort and larval type: long-term pelagic planktotrophy appears to be commensurate with a higher reproductive effort while short-term pelagic lecithotrophy is associated with a lower reproductive effort. The data for nudibranchs are compared with prosobranchs from both marine and freshwater habitats and the resulting overall picture is one of a general lack of correlation between magnitude of reproductive effort and developmental mode. The validity of simple spawn output: adult soma ratios, as a measure of reproductive effort is discussed.