The Mexican Hornshark (Heterodontus Mexicanus)

The Mexican Hornshark (Heterodontus Mexicanus)

Other Combinations: None.

Names

  • English: Mexican hornshark
  • French: Requin dormeur buffle
  • Spanish: Dormilón búfalo
  • Mexico: Mexican horn shark; Gata
  • Local Name: Buffalo hornshark
The Mexican Hornshark (Heterodontus Mexicanus)
The Mexican Hornshark (Heterodontus Mexicanus)

Diagnostic Features Of The Mexican Hornshark

Diagnostic features are a supraorbital ridge at the bottom of the interorbital space, flat concave in depth and a ridge less than a quarter of the length of the eye. The lateral torso density is a large rough area on the first dorsal fin, with 70-130 densities per cm2 in adults. The anterior tip of the retaining tooth is a pair of canines in adults, while the posterior molariform tooth is carcinogenic and does not expand or round. The field marks on the dorsal fin spine and anal fin show a colour pattern of large dark spots, about half the eye diameter or more, against a light background, with a light bar in the space between the supraorbital back and the origin of the first fins and the bases of the pectoral fins. The penultimate dorsal fin has a length of 24-29 in the caudal anal space and amounts to 6-9% of the total length.

The total number of vertebrae is unknown, but the precautionary count is 60-70%, the monospondyllic precautionary count is 30-34%, the diplospondoylous precautionary count is 30-38%, the first dorsal spine count is 14-16% and the diplospondoylous transition count on the second dorsal spine is 9-14%. The anal fin is subeckig, rounded and wrinkled at the apex, reaches to the origin of the lower tail fin, then falls back to its origin and lies about 1 / 2 of the time at its base in the anal caudal space. The first dorsal fin (spine) is directed from the young to the adult, with its origin at the front flipper (pectoral fin introduction) and its free rear tip opposite the origin of the pelvic fins; it is lower and more false with adults, with a height of 8-18% of the total length; it has a somewhat larger pelvic fin than the second, and the second fin has its origin at the front of the pelvic fin, with what the rear tip is faltering and somewhat larger than the first. Egg shells are thick, T-shaped, with spiral flanges transverse to the housing axis and a pair of long, slender tendrils between the housing tip flange and the five coils.

Colour Of The Mexican Hornshark

The background color of the dorsal fin is light gray-brown with large black spots on the body and fins. These spots are approximately half the eye diameter and more than half body size, dark harness pattern on the head, light bars on the interorbital surface of the head (1-2) and dark or indistinct spots on the eyes and fins, abrupt dark tip of the white dorsal fin at the tip of the hatching and vanes of the fins on the body.

Distribution Of The Mexican Hornshark

Eastern Pacific, Mexico, Southern Baja California, Gulf of California, Southern Pacific Coast, Southern Guatemala and Panama Gulf of Panama, Panama, Colombia, Ecuador and Peru. Warm temperate to tropical bullhead sharks in coastal continental waters, which occur on rocky soils, including reefs, seamounts, coral reefs and sandy areas near the coast in 20-50 m depth. Biology is most widespread in the Gulf of Mexico.

Distribution Of The Mexican Hornshark

Biology Of The Mexican Hornshark

The rigid T-shaped spiral flange of the egg shell of this shark serves to protect the egg from the impact of its predators. The long tendrils on the flange indicate that wedging the eggs into the splitting effect of the flexible flange is replaced by anchoring the egg with the tendrils in the substrate, as other bull sharks do with flexible flanged eggs.

Size Of Mexican Hornsharks

Maximum size up to 70 cm. The eggs are 8-9 cm long when young and hatch up to 14 cm, while the males can grow up to 40-50 cm and reach up to 55 cm. It feeds primarily on crustaceans and ground fish, including midshipmen, porichthys and batrachoididae. Interest in fisheries has been influenced by humans, but interest in the species is minimal.

Human Impact On Mexican Hornsharks

Observed by divers in the Gulf of California, but not with a particular focus on ecotourism diving. A small number are taken as bycatch in the shrimp fishery in Mexico and processed into fishmeal for other sharks. It is also caught in Gili nets intended for smaller sharks.

Literature

  • 1972: Taylor
  • 1972: Taylor and Castro-Aguirre
  • 1979: Applegate et al.
  • 1980: Chirichigno
  • 1984: Compagno
  • 1991: Franke and Acero
  • 1993: Michael
  • 1995: Compagno, Krupp and Schneider