DEVELOPMENTAL VARIABILITY IN THE POECILOGONOUS OPISTHOBRANCH HAMINAEA-CALLIDEGENITA - LIFE-HISTORY TRAITS AND EFFECTS OF ENVIRONMENTAL PARAMETERS

The opisthobranch Haminaea callidegenita has poecilogonous development (i.e. produces more than 1 type of offspring) based on swimming abili ty, and therefore dispersal potential, of offspring. Both swimming vel igers (non-feeding) and crawling juveniles were simultaneously release d from almost every egg mass (EM) (97%) indicating that development mo de varied among the offspring of single individuals as well as through out the population. Development of all offspring per EM appeared to be identical until just prior to hatching when approximately half of the siblings metamorphosed and hatched as juveniles. The remaining siblin gs hatched as veligers and metamorphosed after a planktonic period ran ging from 1 to 30 d. Variable hatching appears to be typical in this s pecies because it occurs in almost every EM, is independent of some en vironmental variables, and many hatched veligers have a relatively lon g planktonic period before becoming competent. The percentage of juven ile hatchlings was highly variable among EM (ranging from 4 to 100%). Variability in hatchling type occurred among clutches, populations, an d years. Also, hatchling type was influenced by a 'poor' parental envi ronment in that food deprived females initially produced more swimming larvae than did control females. The percentage of juveniles released per EM was otherwise conservative in that it was not influenced by ma ny of the other factors tested including: physical EM characteristics, female reproductive traits (fecundity, female size, egg size), time o f year, source of metamorphic inducer and culture conditions.