Honeycomb Cowfish, Acanthostracion polygonius
Honeycomb Cowfish, Acanthostracion polygonius. Underwater photograph taken in coastal waters off Bonaire, December 2019. Photograph and identification courtesy of Bob Hillis, Ivins, Utah.
The Honeycomb Cowfish, Acanthostracion polygonius, is a member of the Boxfish or Ostraciidae Family, that is also known as the Cowfish and the Trunkfish and in Mexico as torito hexagonal. Their common name stems from the honeycomb like pattern and “horns” with sloped face and pronounced forehead. Globally, there are four species in the genus Acanthostracion, of which two are found in Mexican waters, both in the Atlantic Ocean.
The Honeycomb Cowfish is a very colorful subtropical fish that has a deep triangular shaped body that is enclosed is a “carapace” made up of hexagonally-shaped plates fused together to form a shell or true carapace. They vary in color and can be blue, green or yellow with the majority being blue and covered with a bold pattern of hexagons outlined by narrow dark lines with the centers and the areas between the hexagons being pale. Their heads have a reticulated or scrawled pattern. They transition to blue on the sides and ventrally. The pectoral fins are translucent. Younger fish are more highly colored than mature fish being orange and yellow with black spots. Their head has a small protruding mouth with fleshy lips with less than 15 conical teeth on each jaw and the gill opening, lacking covers, are short with slits located in front of the pectoral fin base. They are covered with bony scales and have two spines between the eyes pointing forward commonly referred to as “horns.” Their caudal peduncle is elongated and the caudal fin is short and rounded and their pectoral fins have 11 or 12 rays. They do not have dorsal spines or pelvic fins. They have 11 to 14 gill rakers.
The Honeycomb Cowfish is normally found as a solitary individual residing in warm, clear waters in close proximity to coral reefs, sea grass beds, and in estuaries at depths between 3 m (10 feet) and 80 m (262 feet) in water that are 22oC (72oF) to 27oC (81oF). They will form groups of one male and two females during breeding season. They reach a maximum length of 50 cm (20 inches) and 152 grams (0.33 lbs) in weight. They feed during the day consuming small marine sessile invertebrates including algae, shrimp, sponges and tunicates and on worms. They can also locate food by blowing water into the sand. In turn they are fairly immune to predation by larger fish due to their protective external shell. They can also remain have the ability to change colors to match their backgrounds for camouflage and can also remain motionless for long periods of time. They are slow swimmers and only able to generate propulsion via their anal, dorsal, and pectoral fins. Juveniles are better swimmers as their bodies are more aerodynamic than the adults. They reproduce via pelagic eggs and pelagic larvae. The Honeycomb Cowfish 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.
The Honeycomb Cowfish is reported to be a resident of all Mexican waters of the Atlantic Ocean however they are rarely encountered except in coastal waters off Veracruz.
The Honeycomb Cowfish is easily confused with the Scrawled Cowfish, Acanthostracion quadricornis (2 or 3 dark horizontal stripes on the cheeks; dark spots, blotches and irregular wavy lines on the sides).
From a conservation perspective the Honeycomb Cowfish is currently considered to be of Least Concern with stable, widely distributed populations. They are fished commercially being caught with traps and seines and considered to be an excellent food fish and marketed fresh and frozen. They are believed to contain ciguatoxin however. They are a challenge to underwater divers as they are wary and normally flee. They are also utilized by the aquarium trade and found in public aquariums as they are a very colorful fish.