Osmoregulation, growth, and survival during the larval development of bullseye puffer fish Sphoeroides annulatus (Jenyns, 1842, Pisces: Tetraodontidae)

Abstract

We analysed the effects of salinity on survival, growth and the osmoregulatory capacity (OC) of puffer fish larvae (Sphoeroides annulatus). In experiment 1, we compared the growth of larvae maintained at a constant temperature (28 ± 0.5 °C) under seven salinity levels (5, 12, 19, 26, 33, 35 and 40 psu) over a 28-day period. No significant differences were found for larval growth. However, salinity significantly affected survival. The larvae hyper-osmoregulated at low salinities and hypo-osmoregulated at high salinities. The isosmotic point ranged from 338.9 to 355.9 mOsm kg−1, depending on salinity. In experiment 2, survival increased with increasing salinity following direct exposure to the same seven salinity levels over a 72-h period. The isosmotic point ranged from 256.5 to 466.7 mOsm kg−1 depending on the developmental stage. This species hyper-regulated at 5–12 psu, hypo-regulated at 19–40 psu and demonstrated a high euryhalinity at 7 DAH with 95% survival.