Morphofunctional remodelling of the osmoregulatory system in starred sturgeon Acipenser stellatus (Acipenseridae) during transition from hyperosmotic to hypoosmotic regulation

Abstract

Morphological changes in the complex of functionally linked organs responsible for maintaining the osmotic homeostasis in immature euryhaline acipenserid species-starred sturgeon Acipenser stellatusin the process of adaptation to hyperosmotic environmental salinity of 12.5-14.6‰ (403-472 mOsm/L) have been studied with the following characteristics: dynamics of blood serum osmolarity, morphofunctional changes in the neuroendocrine structures (preoptic and tuberal nuclei in the hypothalamus, adrenocortico tropic cells of hypophysis), peripheral endocrine glands (thyroid and interrenal), effector organs (chloride cells of gills and kidney), dynamics of concentrations of cortisol and thyroid hormones (T 3 and T 4 ) in the blood serum, activity of Na + /K + ATPase in homogenates of gills, kidney, and directly in chloride cells. Tran sition from hyperosmotic (in fresh water) to hypoosmotic (in hyperosmotic environment) regulation is deter mined by the essential morphofunctional remodelling of the osmoregulatory organs under study. During this period (72 h) serum osmolarity increases. The neuroendocrine and endocrine systems respond to changes in the environmental salinity in a short time interval (1-24 h) thus stimulating morphofunctional changes in the effector organs and their transition to hypoosmotic regulation, which restores serum osmolarity close to the initial level.

Characterization of the peripheral thyroid system of gilthead seabream acclimated to different ambient salinities

“…Our findings indicate that gilthead seabream maintains thyroidal homeostasis (viz. stable fT3 concentrations in plasma) in a wide range of environmental salinities (from 15 to 55 ppt) by changing plasma fT4 levels (higher levels at hypo-and isosmotic environments), in common with what occurs in Solea senegalensis (Arjona et al, 2008) and Acipenser stellatus (Krayushkina et al, 2015). The differences in plasma fT4 levels in our study are probably due to changes in T4 production/secretion by the thyroid gland, and/or changes in peripheral thyroid hormone metabolism.…”

Reaction of osmoregulatory system of sterlet Acipenser ruthenus Linnaeus, 1758 (Acipenseridae) on influence of hyperosmotic medium

“…У анадромного вида осетровых (севрюги), напротив, в течение 6-72 ч адаптации к гиперосмотической среды происходит уменьшение концентрации Т 4 в сыворотке крови, что, вероятно, связано с потреблением гормона органами-мишенями и включением его в осморегуляторной процесс. В дальнейшие часы адаптации у этого вида происходит восстановление уровня Т 4 до исходного значения (Krayushkina et al 2015). В нашем опыте динамика концентрации тироксина в сыворотке крови не сопряжена с динамикой осмолярности сыворотки крови у стерляди.…”

“…Cмена типа осморегуляции у осетровых происходит в результате существенной функциональной перестройки системы органов, ответственной за поддержание осмотического гомеостаза (Krayushkina et al 2015;Krayushkina et al 2016;Semenova et al 2018). Основную функциональную нагрузку в осуществлении осмотической регуляции несёт комплекс органов гипоталамо -гипофизарной -интерреналовой оси, который контролирует и стимулирует работу эффекторных органов -хлоридных клеток жаберного эпителия, почек, кишечника.…”

A metabolic approach to understanding adaptation to sea water by endangered Persian sturgeon,Acipenser persicusfingerlings

“…Until now, fish osmoregulation has been studied in various physiological levels including hormones, enzymes, electrolytes and histology. Cortisol as a major corticosteroid hormone secreted by the interrenal gland and has been proven to be most important in seawater (SW) adaptation in teleost fish (Reviewed by McCormick, ) and also in sturgeons (Farabi et al., ; Krayushkina, Semenova, Vyushina & Gerasimov, ; Martinez‐Alvarez et al., ). This corticosteroid is responsible for increasing the tolerance to salinity during the transfer of fish from freshwater to sea water.…”

“…Cortisol exerts its role through effects on cellular membrane permeability, increasing the number and size of gill chloride cells, mitochondrial contents, gill Na + /K + ‐ATPase activity and finally activating ionic exchange mechanisms to maintain body homostasis (Reviewed by McCormick, ). The thyroid hormones, thyroxine (T 4 ) and triidothyronine (T 3 ) have a supportive and synergic role with cortisol during osmoregulation of some species including sturgeons in sea water through enhancing the gill Na + /K + ‐ATPase activity (Allen et al., ; Arjona et al., ; Krayushkina et al., ; McCormick, ).…”