Sexual anatomy of the flounder Citharichthys spilopterus (Paralichthyidae)
The Bay whiff Citharichthys spilopterus is distributed from New York to the south of Brazil. In order to know their reproductive anatomy, several specimens were collected during an annual cycle in the lagoon Tampamachoco, Veracruz, Mexico. This species shows, like other Pleuronectiformes, a reduction in the size of the visceral cavity, due to the forward displacement of the anal fin. This change implies a reversal position of the reproductive system in both sexes, so that oviducts in females and sperm ducts in males are oriented forward and open through the genital papilla and the urogenital papilla, respectively, in a position distinctly anterior to that of most teleosteans. The reduction of the visceral cavity causes the ovaries to develop extra viscerally toward the caudal region into the so-called “secondary body cavities”, between the hypoaxial musculature and the anal fin pterygiophores. In males, the gradual modifications of the spermatic ducts during maturation are especially noticeably, consisting in their multiplication and anastomosis. This anatomical condition of the male reproductive system of C. spilopterus represents the morphological model of the Paralichthyidae family, but not that of the Achiridae and Cynoglossidae families. According to the gonadosomatic index for both sexes, the breeding seasons are from January to April and from September to November.