The Winghead Shark, also known as the slender hammerhead or Eusphyra Blochii, is a fascinating specie of shark. This shark gets its name from its extraordinary hammer-shaped cephalofoil head, which can be almost as wide as half the length of its body. This article covers an in depth description, habitat, biology and other fun facts.
Winghead Shark | Description & Appearance
The Winghead Shark (Eusphyra Blochii) is a hammerhead shark species that belongs to the family of Sphyrnidae. It reaches a length of up to 1.9m and has a slender body with a high sickle-shaped first dorsal fin. It owes its name to its large hammer-shaped head, which is about as wide as half of its total length.
The function of the structure of a Winghead Shark head is unclear, but could be related to it’s senses. The large distance between the eyes allows for excellent long-range vision, and the long nostrils that lead to the edges of the cephalopod can allow better detection and tracking of smells in the water. The cephalofoil also offers a large surface area for its electroreceptors (ampullae of Lorenzini) and the lateral line organs (a system of sensory organs).
True to its name, its cephalofoil consists of a pair of long, narrow, sweeping blades. The front of the Winghead Shark has a slight indentation in the middle and a slight bump on the side in front of each nostril. The nostrils are about as wide as the mouth and extend almost the entire front edge of the blade. The width of a Winghead Shark is approximately 40-50% of its total length.
The small mouth arch contains 15-16 upper and 14 lower teeth in rows on either side of a single row of tiny teeth on the upper and lower symphysis in the middle of the jaw. The teeth are small, sharp-edged and triangular. The circular eye is located in the outer anterior corner of the cephalofoil and is equipped with a protective, nicking membrane.
The body is slender and streamlined, with a large, narrow, sickle-shaped first dorsal fin that proceeds from the base of a small pectoral fin. The second dorsal fin is smaller and comes from the tail fin, the third anal fin from the base. The anal fin amounts to approximately half of the first and second dorsal fin. The Winghead Shark also has five pairs of gill slits, with the fifth pair coming from the pectoral fin.
The skin is covered by overlapping skin denticles with three horizontal ridges leading to marginal teeth. The upper tail lobe is longer than the lower one and has notches that reach from the edge to the tip. There are longitudinal grooves on the caudal stem and the dorsal origin of the tail fin. The species is brownish-grey to grey-white and has no fin markings. Like most other hammerhead sharks, the Winghead Shark is viviparous.
The Winghead Shark lives in shallow coastal waters of the Central and West Indo-Pacific and feeds on small bony fish, crustaceans and cephalopods.
Reproduction & Life Cycle
The female gives birth annually to between six and 25 puppies, depending on the region. Winghead Sharks give birth to live cubs that are fully developed embryos fed through a placental connection.
In Australia, the females are 10-11 months pregnant and give birth to their young between February and March. In Bombay, where mating takes place from June to August, females can be pregnant for 8-11 months and give birth to their young in April and May. These puppies can be between 32-45 cm long.
The male bites the female in the side at the beginning of the copulation. The Winghead Shark is viviparous and, like the rest of its family, develops young by maintaining a placental connection with its mother. The adult female has a single functional ovary on the right side and two functional uteri. During pregnancy, this compartment forms two uteri, one for each embryo.
The embryo feeds on the yolk and develops similarly to other sharks. At a length of 40 to 45 cm cephalofoil fins begin to form. When the embryo is 12 to 16 cm long, the yolk supply begins to dry up and a deep fold forms between the yolk sac and the uterine wall, which interlocks with the placenta.
At this stage, the embryo has most of the characteristics of an adult, but is rudimentary and colourless. Blades of cephalofoil fold over the body and a long gill thread protrudes from the gill slit. When the embryo is 30 cm long, it resembles a miniature version of the adult shark. At a length of 20 to 29 cm, the placenta, the first teeth, skin types and skin pigmentations form on the embryo, and the outer gills shrink.
The maximum lifespan of Winghead Sharks is 21 years.
Winghead Shark | Conservation
The International Union for Conservation of Nature classified this relatively harmless species as critically endangered in 2016. Parts of its range are thought to be declining as a result of overfishing. It can be fished for meat, fins, liver oil and fishmeal.