THE EFFECTS OF TEMPERATURE AND SALINITY ON SURVIVAL AND DEVELOPMENT OF EARLY LIFE STAGE FLORIDA STONE CRABS MENIPPE-MERCENARIA (SAY)

The effects of temperature and salinity on survival and growth of early life stage Menippe mercenaria (Say) were tested by rearing larvae and small juveniles (less-than-or-equal-to 10 mm CW) in factorial temperature-salinity arrays (larvae: 20-35-degrees-C [5-degrees-C increments], 10-40 parts per thousand [10 parts per thousand increments]; juveniles: 5-35-degrees-C [5-degrees-C increments], 10-40 parts per thousand [5 parts per thousand increments]). The highest proportion of larvae survived in water of 30-degrees-C, 30 parts per thousand; juvenile survival was 100% in water ranging from 15 to 25-degrees-C and from 25 to 40 parts per thousand. The distribution of this species both latitudinally and seaward may be determined by temperature and salinity tolerance limits of early stages. Both temperature and salinity affected the survival of early zoeal stages (Z1-3). Salinity effects decreased during late zoeal stages (Z4-Z5) and then increased in the megalopal and juvenile stages. The decrease in the effect of salinity on survival at zoeal stage four suggests that osmoregulatory ability begins at this stage. The occurrence of a supernumerary zoeal stage (Z6) was not influenced by temperature or salinity and did not affect survival. Both larval developmental rates and frequency of molting in juveniles accelerated with increasing temperature but were not influenced by salinity. The observed effects of temperature on molting would promote rapid growth when water temperatures are warm, but would delay this physiologically stressful event when temperatures are cool and marginal for survival. The lower optimal temperature for survival of juveniles is probably an adaptation brought about by timing of the major reproductive season.