Renal histometrical alterations in juvenile Orange spotted Grouper, Epinephelus coioides, in response to different environmental salinities



To investigate histometrical changes in renal tubules of Orange spotted
Grouper, Epinephelus coioides, 640 juvenile individuals (4±0.7g, 4±0.5mm)
were exposed to different environmental salinities (5, 20, 40 and 60 ppt) for a
period of 56 days. At each sampling time (day 1, 14, 28 and 56) 3 fish from
each tank (9 fish per treatment) were sampled. Samples were fixed in Bouin's
solution and following routine histological procedure, 5μm sections were
stained using Hematoxylin and Eosin. Histomorphometrical indices in kidneys
were evaluated in microscopic sections. Wall thickness of renal tubules showed
no changes in different salinities up to the end of the experimental period.
Lumen diameter in proximal tubule was increased in 10 and 20 ppt 24 hours
after changing in salinity, but it returned to the control size at the next sampling
times. Lumen diameter in distal tubule in 10 ppt decreased at day 1 but it
increased in 60ppt at day 14. Orange spotted Grouper successfully adapted to
lower and higher salinities than sea water and alterations in renal tubules
returned to the normal conditions during the first week from the beginning of
salinity stress.