Digestive system and gill morphology of the female doublespotted queenfish, Scomberoides lysan (Carangidae: Actinopterygii)

The doublespotted queenfish, Scomberoides lysan (Forsskål, 1775), is an economically important coastal teleost with aquaculture potential. Although aspects of growth and reproduction have been investigated, the digestive physiology of this species remains poorly characterized, representing a critical gap for the development of evidence-based aquaculture protocols. This study provides a morphological and histological characterization of the digestive system of female S. lysan (mean total length = 57.0 ± 0.5 cm) obtained from aquaculture ponds. We examined the entire alimentary canal, from the oral cavity to the hindgut, with special attention to gill structures relevant to feeding mechanics. Distinctive morphological features included heterogeneous gill rakers, with elongated, spine-like structures on the first gill arch contrasting with shorter, blunt rakers on subsequent arches, potentially facilitating opportunistic feeding across different prey types. The intestinal coefficient (0.20-0.36; mean = 0.27 ± 0.05) confirmed carnivorous feeding habits. Histologically, the digestive system exhibited the typical four-layer organization (mucosa, submucosa, muscularis, and serosa) throughout, with region-specific specializations. Notably, gastric glands were significantly more abundant in the cardiac region than in the pyloric stomach (p < 0.01), suggesting functional compartmentalization of digestive processes. Specialized mucus-secreting cells were distributed throughout the digestive system, with variable densities among regions. These findings provide foundational insights into the digestive biology of female S. lysan, establishing an anatomical framework for future studies on digestive morphophysiology in emerging aquaculture species.

KEYWORDS:
Digestive habit; histology; intestinal coefficient