Acyrtops beryllinus

Common Name

Emerald Clingfish

Year Described

Hildebrand & Ginsburg, 1927


Dorsal Fin: 5-6
Anal Fin: 5-6
Pectoral Fin: 20-22
Caudal Fin: 8 principle rays

Body relatively elongate with a laterally compressed abdomen and a dorso-ventrally flattened head. Snout from above bluntly rounded. Head widest at opercle. Mouth subterminal with folds and lappets along lip margin. Teeth in 2-5 rows in lower jaw. Eye moderate (about 67-77% of interorbital distance). Anterior nostril with a small dermal flap. Posterior nostril simple and behind anterior margin of orbit. Opercle with a small dermal flap. Caudal peduncle relatively deep. Dorsal and anal fins opposite each other. Anus closer to anal fin than it is to pelvic disk. Pectoral fin broad and fan-shaped with lower rays shortened. Pelvic disk small with papillae anteriorly and sparse papillae posteriorly. Lateral line pores restricted to head.


Body and head varies from bright green to red-brown overall peppered with tiny black melanophores. Coloration varies based on substrate. There are scattered larger gray, pale blue, brown, or blackish spots on the upper body that become denser on the head. Green individuals often with green streaks and spots intermixed with red-brown speckles. Several dark lines radiate from the eye. Belly paler green. Fins translucent with green anterior edges.


A small species: maximum size to 2.5cm SL.


Found only on seagrass beds from 1-15m. Adheres to the blades of Thalassia seagrass.


Appears to be widespread in the Caribbean Sea from the Florida Keys to Venezuela and Brazil, including the islands. Limits of range not known.


Gould, W.R. 1965. The biology and morphology of Acyrtops beryllinus, the emerald clingfish. Bulletin of Marine Science, 15 (1), 165-188.

Johnson, R.K. & D.W. Greenfield. 1983. Clingfishes (Gobiesocidae) from Belize and Honduras, central America, with a redescription of Gobiesox barbatulus Starks. Northeast Gulf Science, 6 (1), 33-49.

Other Notes

Rimicola brevis is considered a synonym of Acyrtops from coastal Panama. Central American populations of Acyrtops have higher meristic counts than typical A. beryllinus but morphometrics are typical.

The two described Caribbean Acyrtops species are very similar in appearance the the extent and limits of their ranges is not known. It is not even certain if they are simply one species or a complex of several species. Gould (1965) concluded the two species cannot be distinguished but Johnson & Greenfield (1983) kept them separate. As meristics overlap, it seems like a combination of eye size, interorbital distance, and head length can separate them. More research needs to be done on this genus. The population in the Lesser Antilles is defined as A. amplicirrus at this time.