Early development of dorsal and pelvic fins and their supports in hatchery-reared red-spotted grouper, Epinephelus akaara (Perciformes: Serranidae)

Early morphogenesis of dorsal and pelvic fins and their supports in the larval and juvenile red-spotted grouper, Epinephelus akaara, was examined using a hatchery-reared series. The dorsal spine anlage first appeared suspended in the middle part of the finfold at ca. 2.5 mm TL. Dorsal and pelvic supports appeared by the time the fish reached ca. 3 mm and started to ossify at ca. 3.5 mm. Elongated spines and their supports developed synchronously in both dorsal and pelvic fins. The formation of dorsal fin supports proceeded from anterior to posterior. The ossification of supports was completed by ca. 33 mm. Spinelets on the second dorsal spine and pelvic spine appeared by ca. 3 mm. In specimens larger than 36 mm, all spinelets on the second dorsal spine and pelvic spine had disappeared. The maximum size of the second dorsal spine and pelvic spine lengths relative to TL were ca. 45% and 44% at 3.3 mm in fish size, respectively. Thereafter, their proportions decreased Gradually. Considering the order of development of the elongated spines and mucous cells in the early life stages, the elongated spines might function as antipredator devices.