MULTIPLE SPAWNING AND MOLT SYNCHRONY IN A FREE SPAWNING SHRIMP (<i>SICYONIA INGENTIS</i>: PENAEOIDEA)

Abstract

Field sampling was conducted to examine patterns of molt and reproductive activity in populations of the free spawning, penaeoid prawn, Sicyonia ingentis; some of these patterns were also verified by laboratory studies. Multiple spawning in the field was inferred from the high frequency of prominent oocyte features which are termed cortical specializations. In a prior laboratory study (Anderson et al., 1984), the time from cortical specialization stage to spawning was determined to be less than one week. Molt studies showed that females began a synchronous molt cycle in June which was not completed until late October or early November, after the spawning season was over. Males exhibited similar synchrony, but the period was shorter, and there was more variability. Data indicate that not only the absolute duration of the molt cycle varied with season, but the relative duration of molt cycle stages also varied. December and January were the only months of the year in which the relative frequency of molt cycle stages approximated literature values. Potential multiple spawning throughout the summer, coupled with almost no molting in the summer, suggest that multiple spawning occurred without intervening molt or mating in field populations. This was substantiated by laboratory studies which directly demonstrated multiple spawning by these prawns within a single, prolonged molt cycle.