Larval Fishes from Carrie Bow Cay, Belize - National Museum of Natural History - Division of FishesLarval Fishes Home

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Larval Fish: Family Pleuronectiformes

Although adult flatfishes (order Pleuronectiformes) have both eyes on the same side of the head, their larvae have one eye on each side, like any other fish. When the larva transforms into a juvenile, one of the eyes migrates to the other side. Usually, the eye migration takes place somewhat before the fish settles out on the bottom. Three families of flatfishes occur in the waters around Carrie Bow Cay: the Achiridae (soles), Bothidae (left-eyed flounders), and Cynoglossidae (tongue fishes).

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Bothus ocellatus

Bothus ocellatus (Bothidae), 18 mm SL. The ocellated flounder is a common shallow-water species in the tropical western Atlantic. Larvae have a series of irregular reddish spots around the bases of the dorsal, anal, and caudal fins, and around the gill area and the pelvic-fin base. Two of the reddish spots extend proximally to the edge of the myomeres.

Bothus ocellatus

Bothus ocellatus (Bothidae). This sequence shows three stages in the process of eye migration. In the specimen on the left, the right eye is still on the right side of the head. In the center photo, the eye is passing across the top of the head. What appears to be a hole in the head is actually a gap between the top of the head and the dorsal fin, which in these fishes extends forward onto the snout. In the specimen on the right, the eye has arrived on the left side, and the gap between the dorsal fin and the head is closing.

Bothus ocellatus, USNM 354556

Bothus ocellatus (Bothidae), 23 mm SL, reared, USNM 354556. This specimen has completed the transformation from larva to juvenile. The eye migration is complete, and the definitive color pattern has appeared. The fish will now take up life on the bottom, where it will be well camouflaged against the sandy substratum.

Bothidae, USNM 353522

Unidentified Bothidae, 9.5 mm SL, USNM 353522. A few faint erythrophores along the anal-fin base and the posterior part of the dorsal-fin base are the only color present in this larva. Melanophores are present along the ventral midline and the base of the anal fin.

Syacium, USNM 363537

Syacium sp.(Bothidae), 13 mm SL, USNM 363537. The pelvic fins and several anterior dorsal-fin rays are elongated with pigmented tips. Elsewhere, conspicuous black pigment is present along the bases of the dorsal and anal fins, the lateral midline, behind the head and on the throat, and over the gut. A few erythrophores are present over the gut and on the posterior part of the head. The three Caribbean species of Syacium are distinguished by their color pattern and lateral-line scale counts, characters which are not present in larvae.

Symphurus, USNM 353967

Symphurus sp. (Cynoglossidae), 12 mm SL, USNM 353967. In this specimen, the eyes have migrated and the scales have appeared, but the form and color pattern are still largely those of the larva. Some red-yellow pigment is present on the head and along the dorsal- and anal-fin bases, but most of the pigment consists of melanophores.

Symphurus, USNM 353966

Symphurus sp. (Cynoglossidae), 12 mm SL, USNM 353966. This specimen is about the same size as the preceding, but it is somewhat further along in development. Note the dark black stripe that has developed along the length of the vertebral column.

Achirus, USNM 353970

Achirus sp. (Achiridae), 5 mm SL, USNM 353970. Achirid larvae are heavily pigmented. The pigment is arranged in three lobes on the dorsal fin and two lobes on the anal fin, with the rest of the fins clear. The caudal fin is also unpigmented. One of the anterior dorsal-fin rays is markedly elongate with an expanded tip.

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