Effect of dendritic organ ligation on striped eel catfish Plotosus lineatus osmoregulation

Abstract

Unique amongst the teleost, Plotosidae catfish possess a dendritic organ (DO) as a purported salt secreting organ, whereas other marine teleosts rely on their gill ionocytes for active NaCl excretion. To address the role of the DO in ionregulation, ligation experiments were conducted in brackish water (BW) 3‰ and seawater (SW) 34‰ acclimated Plotosus lineatus and compared to sham operated fish. Ligation in SW resulted in an osmoregulatory impairment in blood (elevated ions and hematocrit) and muscle (dehydration). However, SW ligation did not elicit compensatory changes in gill or kidney Na+/K+-ATPase (NKA) activity and/or protein expression while a decrease in anterior intestine and increased in posterior intestine were observed but this was not reflected at the protein level. Following ligation in SW, protein levels of carbonic anhydrase (CA) and V-ATPase B subunit (VHAB) were higher in kidney but either lower (CA) or unchanged (VHAB) in other tissues. Taken together, the osmotic disturbance in ligated SW fish indicates the central role of the DO in salt secretion and the absence of a compensatory response from the gill.

Effect of Short-term Elevation Temperature and Salinity Stress on Caspian Roach, Rutilus caspicus

“…In general changes in hematology can be explained by changes in ionoregulatory status [40] and it is one of the secondary stress responses in fish [51,52]. Hematocrit showed a positive correlation with salinity in both stages, as has been reported by (Platichthy flesus: [53]; Gymnocypris przewalskii: [10,20,54,55] and in most anadromous teleosts studied to date (Oncorhynchus mykis: [56]; O. tshawytscha: [57]; S. salar: [58]) or sturgeon (Acipenser oxyrinchus, A. brevirostrum: Baker et al, 2005). By attention to previous finding which indicating to the important role of effective hormones such as cortisol, prolactin, in acclimation phase to osmotic and environmental challenges (several hours to several days after stress) [8], this result might be interpreted by measuring hormonal changes but not done in the present study thus measuring hormones which are involving in response to environmental challenges could be helpful in future study.…”

“…According the management point of view, it seems that HS and salinity changes have some physiological effects concern ion regulation in this fish. Although for more confidence, study various salinities, different time of sampling and other environmental tolerances such as temperature, culture density, diet and also focus on the expression patterns of ion transporters such as NKA, Na + /K + /2Cl − (NKCC), cystic fibrosis transmembrane conductance regulator (CFTR, chloride channel), V-ATPase proton pump in the gills, kidney and digestive tract [24,55] are needed.…”