Growth and Maturation of a North-American Fairy Shrimp, Streptocephalus-Seali (Crustacea,Anosttaca): A Laboratory Study
1. We evaluated survival, growth and time to maturation of the fairy shrimp, Streptocephalus seali Ryder, in the laboratory at various combinations of temperature and water hardness. 2. Both independent factors affected survival and growth of S. seali. Multiple regression analysis and response surface modelling predict that after 4 days, over 80% survival is obtained at temperatures from 14 to 28-degrees-C and water hardnesses from 60 to 130 mg CaCO3 1-1. 3. Growth rates of larvae were often maximum at physicochemical conditions other than those which had promoted maximum rates of survival. For example, after 12 days mean total body length was almost 12 mm in larvae which had been maintained at 34-degrees-C (80 mg CaCO3 1-1); the maximum survival rate had been obtained at 19-degrees-C. Total length was directly correlated with temperature at the lowest hardness tested, but not at the other two hardnesses (100 and 120 mg CaCO3 1-1). At the latter water hardnesses, total length was significantly less at 34-degrees-C than at 32-degrees-C on all three sampling occasions (4, 8 and 12 days post-hatch). 4. Similarly, developmental stage of larvae correlated well with temperature but larvae reared at 34-degrees-C did not develop more quickly than those reared at 32-degrees-C. After 12 days, most larvae at the two highest temperature treatments had developed at least to Stage 14 and many were nearly mature; at 17-degrees-C most larvae were still at Stage 10. 5. During our study of maturation rate of females we noted that egg production was initiated after completion of fourteen or fifteen moults. Mean time to maturation at 27-degrees-C (17.3 +/- 2.8 days) exceeded that at 32-degrees-C (12.3 +/- 2.6 days). The minimum time to maturation of a shrimp was 9 days at 32-degrees-C.