Family HeterdontidaeHorn and Bullhead Sharks

Tiffany Adams

September 25, 2007

Elasmobiology

Taxonomy• Order: Heterodontiformes

– Family: Heterodontidae- 1 Genus, 8 species• Heterodontus francisci- Horn shark• Heterodontus galeatus- Crested bullhead shark• Heterodontus japonicus- Japanese bullhead shark• Heterodontus mexicanus- Mexican hornshark• Heterodontus portusjacksoni- Port Jackson Shark• Heterodontus quoyi- Galapagos bullhead shark• Heterodontus ramalheira- Whitespotted bullhead shark• Heterodontus zebra- Zebra bullhead shark

• Origin of scientific name– Hetero = other or different– Dont = teeth

Distinctive Characteristics• Relatively small <165cm

• Five gill slits

• Anal fin present

• No nictating eyelid

• Small spiracle present

• Two dorsal fins, both with stout spines

• Large pectoral fins

• Crest/ridge above each eye

• Short, blunt snout

• Nostrils connected to mouth with deep nasal groove

• Differentiated anterior and posterior teeth

Crested bullhead shark

Habitat and Global Distribution

• Found in warm-temperate and tropical continental waters of the western Indian Ocean and western and eastern Pacific; absent from the Atlantic and Mediterranean.

• Benthic, prefer to live near rocks, reefs, caves, and kelp beds in shallow coastal waters.

• Nocturnal hunters, prey mostly on benthic invertebrates

• Diet includes sea urchins and anemones, mollusks, crustaceans, worms, and small fish.

• Regurgitate shells and hard parts.

Prey

Horn shark eating squid eggs

Galapagos bullhead shark

Horn shark

Japanese bullhead shark Zebra shark

Port Jackson sharkMexican hornshark

Camouflage- Heterodontidae are prey too!

Prominent supra-orbital crest/ridge above each eye• Helps protect eye while searching for food in hard substrates?

Crested bullhead

shark

Horn shark Japanese bullhead shark

Heterodontidae have short, blunt, pig-like snouts. Nostrils are connected to mouth through a deep nasal groove.

• Able to protrude lower labial cartilage (jaw) and employ inertial suction coupled with rapid mandible depression to capture food. (Edmonds 2004)

Crested bullhead shark Port Jackson shark

Differentiated anterior and posterior teeth • anterior teeth small and

multicuspid, used for

grasping prey

• posterior teeth are enlarged, elongated and molariform, used for crushing shells

Galapagos bullhead shark

Jaws of a Horn shark

The mean mass-specific bite of H. francisci (horn shark) was greater than that of many other vertebrates and second highest of the cartilaginous fishes that have been studied.(Huber 2005)

Horn shark

Mexican hornshark

Port Jackson

shark

Both dorsal fins have stout spines

• Rare feature among sharks (Heterodontidae & Squalidae)

• Hypothesized to act as an anti-predator device (dead asphyxiated wobbegong)

• Used to as an aid in age determination (Carrier 2004)

• Spines have been used to make jewelry

Skeletal structure of Horn shark dorsal spine

Reproduction

• Age of maturity estimated between 8-10 years, but not known

• Oviparous, egg cases contain yolk sac• Two eggs can simultaneously mature within

each female, they may lay up to 24 eggs total in a breeding season.

• Spiral-flanged egg cases, conical, some with tendrils. Up to 15cm in length.

• Expulsion can take up to 2 hours. Soft egg case is carried by mother in her mouth and secured in rocky substrate. Communal nests may contain over 16 egg cases.

• Young will emerge in 6-10 months, depending on species.

• Some species, such at the Port Jackson shark, undergo a yearly migration for spawning.

Egg Cases

Port Jackson shark

Mexican hornshark

Horn shark

Newly emerged Japanese bullhead

shark

Population Status• Not targeted by fisheries, bycatch only. May be used for fishmeal.• IUCN lists all at data deficient or least concern.

• Docile, non-aggressive(even when harassed by divers), moving slowly along bottom or resting in groups

• Horn shark off Laguna Beach- walking with pectoral fins? http://www.youtube.com/watch?v=uW4Ha1qTtjo

• Embryo action inside a Port Jackson egg case http://www.youtube.com/watch?v=M5Ml1-q_xGY

Videos

Bibliography• Allen, T. 1999. Shark Almanac. Lyons Press, New York. Pp. 62-3.• Carrier, J,, Musick, J., and Heithaus, M. 2004. Biology of Sharks and Their Relatives. CRC Press, Boca Raton.

Pp. 42-3, 66-7, 401.• Compagno, L.J.V., 1984. FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated

catalogue of shark species known to date. Part 1 - Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1):1-249.

• Edmonds, M. et al. 2001 Food capture kinematics of the suction feeding horn shark, Heterodontus francisci. Journal Environmental Biology of Fishes. 62(4):415-427

• Huber, D. et al. 2005. Analysis of the bite force and mechanical design of the feeding mechanism of the durophagous horn shark Heterodontus francisci. The Journal of Experimental Biology. 208(18):3553-71

• IUCN 2006. 2006 IUCN Red List of Threatened Species. <http://www.iucnredlist.org>. Downloaded on 20 September 2007.

• Jones,W.T. 2005. A hermaphroditic Port Jackson shark, Heterodontus portusjacksoni, with complete and separate female and male reproductive tracts. Journal of the Marine Biological Association of the UK. 85:1171-1172

• Nelson, J. 1984. Fishes of the World. 2nd Ed. John Wiley & Sons, Inc., New York. P. 50.• O'Gower, A.K. 1995. Speculations on a spatial memory for the Port Jackson shark (Heterodontus portusjacksoni).

Marine & Freshwater Research. 46(5):861-871.• Parker, S. 1999. The Encyclopedia of Sharks. Firefly Books, Buffalo. Pp. 50, 130, 174-5.• Perrine, D. 1999. Sharks and Rays of the World. Voyageur Press, Hong Kong. Pp. 82-5.• Steel, R. 1985. Sharks of the World. Facts on File, Inc., New York. Pp. 42-43, 77-81.