Thermal imprinting modifies bone homeostasis in cold-challenged sea bream (Sparus aurata)

Fish are ectotherms and temperature plays a determinant role in their physiology, biology and ecology, and is a driver of seasonal responses. The present study assessed how thermal imprinting during embryonic and larval stages modified the response of adult fish to low water temperature. We targeted the gilthead sea bream, which develops a condition known as winter syndrome when it is exposed to low water temperatures. Eggs and larvae of sea bream were exposed to four different thermal regimes and then the response of the resulting adults to a low temperature challenge was assessed. Sea bream exposed to a high-low thermal regime as eggs and larvae (HLT; 22 degrees C until hatch and then 18 degrees C until larvae-juvenile transition) had increased plasma cortisol and lower sodium and potassium in response to a cold challenge compared with the other thermal history groups. Plasma glucose and osmolality were increased in cold-challenged HLT fish relative to the unchallenged HLT fish. Cold challenge modified bone homeostasis/responsiveness in the low-high thermal regime group (LHT) relative to other groups, and ocn, ogn1/2, igf1, gr and tr alpha/beta transcripts were all downregulated. In the low temperature group (LT) and HLT group challenged with a low temperature, alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) activities were decreased relative to unchallenged groups, and bone calcium content also decreased in the LT group. Overall, the results indicate that thermal imprinting during early development of sea bream causes a change in the physiological response of adults to a cold challenge.Seventh Framework Programme project Lifecycle [EU-FP7 222719

Experimental treatments with diflubenzuron and deltamethrin of sea bass, Dicentrarchus labrax L., infected with the isopod, Ceratothoa oestroides

Sea bass with approximate average weights of 5 and 20 g were treated against Ceratothoa oestroides infection with: (i) medicated pellets of diflubenzuron PC90 at a dosage of 3 mg kg(-1) body weight (BW) per day for 14 days. Lice were counted at the beginning of treatment and 19 days after treatment. The drug cleared all lice in the treated group; in the control group, infection remained high 30 days after beginning the experiment. It was concluded that medicated pellets containing 3 mg kg(-1) BW diflubenzuron effectively cleared pre-adult and adult stages of the isopod parasite over a 14-day period. No adverse effects were recorded in treated sea bass during the trials and no reinfection occurred 15 days after end of the treatment. (ii) Deltamethrin by means of bath treatments in infected sea bass kept in experimental tanks at 20degreesC. Before treatment, toxicity on healthy fish was preliminarily assessed by testing five fish from each size group at concentrations of 30 10, 5, 3, 1, 0.1, 0.05 and 0.01 mg L-1 for 30 min. The therapeutic concentrations tested were: 10, 5, 3, 0.15, 0.1, and 0.05 mug L-1 and assessed at 1, 24 and 48 h. Best results were achieved with the 10 mug L-1 (0.01 mg L-1) dose, where prevalence was reduced from 100 to 0% over 24 h in both large and small fish. No parasite recovery was observed at 48 h. The dose of 5 mug L-1 reduced prevalence from 100 to 11.7% and to 0% for small and large fish, respectively. Finally, with the 3 mug L-1 dose, prevalence was reduced from 100 to 37.5% (small fish) and to 13.3% (large fish). Lower doses were ineffective on the parasites at either 24 or 48 h