Morphological characteristics and functional adaptation of gills in the Meagre, Argyrosomus regius (Asso, 1801).

A comprehensive morphological description of Argyrosomus regius (Asso, 1801) gills was conducted through the gross and scanning electron microscopic examinations in addition to the morphometric analysis of the number, length of the gill rakers and the space between them. The medial surface of the 1st gill arch was differed than that of the other three gill arches. Four gill arche's lateral surfaces contained pear-shaped, circular, and oval-shaped spine groups with varying sizes. The medial surface of the 1st gill arch only had different sizes of pear-shaped and oval groups of spines, while the other gill arches had the same-shaped groups of spines beside the presence of small circular groups. The lateral rakers of the 1st gill arch were long, and only one border carried pointed spines, while its medial rakers were triangular. The rakers of the 2nd, 3rd, and 4th gill arches appeared flask like medially and laterally. There were few folds and tubercles appearing on the primary gill filament surfaces; some folds appeared like the helix on the surface of their parts near the gill arch convex border. This is the first anatomical study on Argyrosomus regius gills and we aimed to reveal the unique structural specifications for gill rakers that related to its feeding behavior and we will contribute to a better understanding of its ecological niche and feeding strategies in its natural environment.