Saddleback syndrome in the firemouth cichlid Thorichthys meeki (Cichliformes: Cichlidae) in Campeche, Mexico

Abstract

There are several external and internal abnormalities that affect development in both wild and farmed fish. One of these abnormalities is known as saddleback syndrome (SBS), characterized by abnormalities in the shape, number, or absence of dorsal pterygiophores, causing a concavity in the dorsal region and absence of fin sections. The causes of this syndrome are not yet clear, but could be caused by fishing or predator damage, nutritional deficiencies, genetic conditions and environmental stress from pollutants that may cause alteration in the ontogenetic development of the fish. This study recorded for the first time the SBS in a wild-caught specimen of Thorichthys meeki Brind, 1918 (Cichlidae). Specimens were collected in the locality of Chekubul, municipality of Carmen, Campeche, México on November 18, 2022. The development of the dorsal fin begins from the first to the ninth dorsal spine where there is a dorsal concavity, which ends with the last three dorsal spines. There is no evidence of scoliosis or lordosis from the X-ray analysis; however, the dorsal pterygiophores show irregularities in their development. The specimen with the syndrome showed no other body abnormalities that would have prevented its development to adulthood, although the causative agent is unclear.