The effect of acclimation salinity and age on the salinity tolerance of pink shrimp postlarvae

The pink shrimp Farfantepenaeus duorarum (Burkenroad) lives in south Florida ecosystems in different salinity regimes ranging from brackish to hypersaline. In Florida Bay, the main nursery grounds, juveniles reside in 25–50 salinity; while 20 km northwest of the Bay, juveniles inhabit more estuarine salinities between 5 and 15. In this study we investigated the hypothesis that the disparate salinity regimes in which pink shrimp juveniles reside may be due to a non-genetic resistance adaptation to different acclimation salinities in their respective nursery habitats during postlarval development when the maximum tolerance to salinity occurs. To test this hypothesis and to define salinity tolerances during ontogenetic development, salinity trials were conducted with four postlarval ages (PL 15, PL 25, PL 35 and PL 55) previously acclimated in two salinities (15 and 35) and then exposed to an abrupt salinity change for 96 h at 27.5 ± 0.5 °C. Results indicated that the degree of tolerance to salinity varies with ontogenetic development. Regardless of acclimation salinity, two clearly distinguishable salinity tolerance ages were discernable. Postlarvae of age PL 35 and PL 55 exhibited significantly higher average survival than at an age of PL 15 and PL 25. This result suggests that postlarvae between 25 and 35 d old may complete development of osmoregulatory capabilities to cope with abrupt changes in salinity, which concurs with the age at which planktonic postlarvae settle on the sea-grass banks of Florida Bay. Results regarding salinity tolerances in the two acclimation salinity groups demonstrated that postlarvae acclimated in a salinity of 15 tolerated salinities 20 units lower than those acclimated in regular 35 sea water salinity. The high survival of postlarvae recorded at salinities between 2 and 15 after a long acclimation period at a salinity of 15 suggested that non-genetic resistance adaptation (acclimation) had taken place during development, supporting our hypothesis that a preconditioning salinity during postlarval development may modify the subsequent tolerance limits of juvenile stages.

► We examined the hypothesis of a non-genetic adaptation to acclimation salinities.
► We conducted salinity trials with four postlarval ages acclimated in two salinities.
► A clear shift in salinity tolerances between acclimation salinities was observed.
► Salinity tolerance ranges also vary with ontogenetic development.
► Our data support the euryplasticity hypothesis for pink shrimp early stages.