Histological characterization of a marine fish (Siganus canaliculatus): insights from an extreme environment fish species

IntroductionSafi, Siganus canaliculatus, is an important species in the Arabian Gulf with high ecological and commercial value. Adaptable to various environmental conditions, safi presents remarkable tolerance for high salinity and temperature and it is now an aquaculture emergent species in the Arabian Gulf. This study presents the first in-depth histological characterization of safi’s tissue structure in the Arabian Gulf.MethodsHistological analysis was conducted on nine organs including the skin and muscle, gill, liver, intestine, male and female gonads, heart, kidney, and spleen. Histomorphometric analyses were also conducted to quantify secondary lamellar length and width, hepatocyte diameter, intestinal goblet cell density and glomerular diameter.ResultsThe mean secondary lamellar length and width were 153.00 ± 29.91 µm and 10.99 ± 3.06 µm, respectively, while the mean hepatocyte diameter was 12.29 ± 5.09 µm. The mean intestinal goblet cell density was 0.000605 ± 0.000312 cells/µm2, and the mean glomerular diameter was 36.08 ± 5.99 µm.DiscussionOverall, the examined organs showed tissue structures comparable to those reported to other marine teleost species, while also displaying structural characteristics consistent with physiological adaptation to the hyper-saline environment of the Arabian Gulf, particularly in organs associated with osmoregulation. These included gill, liver intestine and kidney. This study provides the first comprehensive histological baseline for S. canaliculatus from the Arabian Gulf, establishing a valuable reference for future studies in fish biology, conservation, management, and aquaculture research.