Effect of stress during handling, seawater acclimation, confinement, and induced spawning on plasma ion levels and somatolactin immunoreactivity in mature female thin-lipped gray mullet, Liza ramada

Introduction Understanding the physiological picture of fish during the reproductive cycle, seawater acclimation, and induced spawning is of essential value to know the possible reasons of preoviposition mortality and to develop successful hatchery technology. Aim of the study Determination of the effect of different stress factors on hydro–mineral balance as well as changes in somatolactin (SL) immunoreactive cells in mature Liza ramada females. Material and methods Water chemistry and the different plasma ion levels were measured. Immunocytochemical staining for the sections of the pituitary gland was performed to describe the activity of SL immunoreactive cells. Results The plasma levels of PO_4 ^3–, Na^+, K^+, Ca^2+, and Mg^2+ showed a slight increase during transportation without anesthesia. The concentrations of these minerals returned to the initial levels by using clove oil (5 mg/l) as anesthetic. However, their levels decreased during seawater acclimation and gradually increased with confinement to reach the initial values. Furthermore, the levels of PO_4 ^3–, Na^+, K^+ , Ca^2+, and Mg^2+ were significantly (Pr0.05) elevated during spawning and preoviposition mortality of ovulated females. SL immunoreactive cells in the pars intermedia of the pituitary showed a dramatic increase in their secretory activity during handling, seawater acclimation, preoviposition mortality, and induced spawning. However, the synthetic activity of these cells was enhanced during confinement. The activation of SL-secreting cells was in parallel with changes in hydromineral balance induced by stress, supporting the possible role of this hormone in the adaptive response of fish to stress. Conclusion Clove oil effectively suppresses the response of electrolytes to stress, and may prove to be a useful anesthetic for reducing the adverse effects of stress.