Pearl Blenny, Entomacrodus nigricans
Pearl Blenny, Entomacrodus nigricans. Fish caught from coastal waters off Noord, Aruba, February 2023. Length: 4.8 cm (1.9 inches). Catch, photograph and identification courtesy of James Lafontaine, Long Island, New York.
The Pearl Blenny, Entomacrodus nigricans, is a member of the Combtooth Blenny or Blennidae Family, and is known in Mexico as blenio perlado and borracho perlado. Globally, there are twenty-four species in the genus Entomacrodus, of which two are found in Mexican waters, one in the Atlantic, this species, and one in the Pacific Ocean.
The Pearl Blenny has a very elongated body. They are pale brown or tan in color with dark brown double bands on the sides with bright white spots along the length of their body, small dark spots on the upper half of the head, and thin dark bars on the lips. They have a blunt head with a high forehead with two moderately sized-eyes. Their cirri are simple. When breeding the male’s cirri and dorsal fins become enlarged. Their head is short and blunt with a rounded overhanging snout with simple cirri. Their mouth has slender, sharp comb-like teeth on both jaws. Their anal fin has 2 spines and 15 to 17 rays; their caudal is broadly rounded; their first dorsal fin has 13 spines; their second dorsal fin has 13 to 16 rays. Their lateral line has a short arch over the pectoral fins. They do not have scales.
The Pearl Blenny is a non-migratory coastal species that is found close to the surface and in tidal pools, rocky pools and over boulders with juveniles being found at greater depths. They are known to shuttle back and forth between rocky pools. They have developed amphibious adaptations that allow them to maintain positions in high energy environments and have the to survive in the shade out of water for up to 2.5 hours during the day and 3.5 hours at night but only for 7 minutes in direct sunlight. They are of scientific interest having flattened eyes that are thought to be an adaptation that allows them to see in air. They feed diurnally on algae. They are found at depths up to 8 m (20 feet). They reach a maximum length of 10.0 cm (3.9 inches). They are diurnal omnivores that primarily consume algae. In turn they are preyed upon by large crustaceans including crabs and lobsters and larger demersal fish. Reproduction is oviparous in distinct pairs with adhesive demersal eggs and attach to empty bivalve shells, holes and crevices in rocks, sponges, and inside discarded marine debris the substrate via filamentous, adhesive pads that are guarded by the males and then turn into planktonic larvae. The Pearl Blenny is a small shallow-water species that is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.
In Mexican waters the Pearl Blenny are found in the southern Gulf of Mexico around the Yucatán Peninsula from Campeche south to Belize in the Caribbean.
The Pearl Blenny is most likely confused with the Molly Miller, Scartella cristata (two rows of red and white barred cirri; green in color; blotched and barred).
From a conservation perspective the Pearl Blenny is currently considered to be of Least Concern with stable, widely distributed populations. They are known to be an invasive species. They are too small in stature to be of interest to most. They are utilized by the aquarium trade on at a nominal level.