Anatomy of the visceral cavity of Eugerres mexicanus (Teleostei: Gerreidae)

Abstract

Introduction. The visceral cavity of teleostean fishes contains the kidneys, digestive tube and annexed glands, gas bladder, gonads, and spleen. Objective: To analyze and describe the anatomic relationships of the organs of the visceral cavity of the Mexican mojarra, Eugerres mexicanus. Methods: By means of dissections, we analyzed, described and illustrated the splanchnology of the visceral cavity of 10 adult specimens from the State of Chiapas, Mexico. Results: The visceral cavity is delimited by the precaudal vertebrae, the scapular and pelvic girdles, the pleural ribs, the first anal pterygiophore and several myotomes. Both kidneys, with extraperitoneal character are partially fused each other, and contact the neurocranium, the precaudal vertebrae, and the gas bladder. The digestive tube does not present a stomach nor pyloric caeca, and it is 1.3 the standard length of the fish. The liver has two short right lobes. Both ovaries and testes are wide and reach the liver. The spleen is ovoid and is located on the left side of the duodenum. The gas bladder has two anterior lobes, its posterior end is in direct contact with the floor of the visceral cavity, and contain the urinary bladder. Discussion: The organization of the organs in the visceral cavity is in the anatomical pattern of the teleostean fishes, however, the organ that shows the highest number of special characters is the gas bladder, which as in other species of Eugerres is large and shows two notable anterior lobes, reinforced by epipleural ribs. Compared with other species of Eugerres, the Mexican mojarra shows, as exclusive characters: a) the union of the posterior end of the gas bladder with the floor of the visceral cavity, and, b) the location of the urinary bladder within the gas bladder.

Character variation in separate body regions of Gerreidae (Osteichthyes: Teleostei) fishes inferred from geometric morphometrics

“…Gerres have depressed and elongated bodies in cephalic and trunk regions with a narrower peduncle, giving them a less robust body but perhaps greater swimming speed. These patterns of shapes are consistent with a previous osteological study by Kobelkowsky (2004).…”

“…Also, shape convergence is observed in the peduncle within Gerres, Eucinostomus, and Diapterus-Eugerres species (Figures 2, 4 and 5). These morphological shape variations concur with previous studies that documented body shape utility to discriminate taxonomic groups within Gerreidae (e.g., Andreata & Barbieri, 1981;Andreata, 1988Andreata, , 2011Bussing, 1995;Castro-Aguirre et al, 1999;De La Cruz-Agüero & Galvan-Magaña, 1993;García-Rodríguez et al, 2019;Kobelkowsky, 2004;Vergara-Solana et al, 2014). Under this geometric morphometric approach, we documented that cephalic shape variation should be evaluated as a helpful character for future systematic studies of Gerreidae species and sister groups within infraclass Teleostei.…”

“…Similarly, a highly developed supraoccipital crest in D. rhombeus and E. lineatus has been reported to influence the body shape, making it tall and triangular, characteristic of littoral and demersal environments (Andreata, 1988). Furthermore, a more prominent supraoccipital crest allows a greater insertion of epaxial muscles, which affects lateral head movements (Kobelkowsky, 2004). In addition, morphological changes in the trunk and caudal shape could be related to undulatory swimming employed by many fishes for routine swimming and extended sprints (Müller & Van Leeuwen, 2006).…”

Trophic morphology and diet of the endangered fish Tlaloc hildebrandi (Cyprinodontiformes: Profundulidae).

“…The organography of the visceral cavity of T. hildebrandi is the typical of that of teleost fishes, as illustrated in Chirostoma estor (Kobelkowsky & Figueroa, 2018) and Eugerres mexicanus (Kobelkowsky & Terán-Martínez, 2020).…”