Hammerhead Shark - Sphyrnidae
Sphyrnidae is a family of large cartilaginous marine water fish belonging to the order Carcharhiniformes. They are commonly known as hammerhead sharks. Squalo Martello Sphyrnidae Hammerhead shark intotheblue.it
The scientific name of the family and main genus, Sphyrna, derives from the Greek σφυρί, sphyrí (hammer).
Distribution and habitat
Hammerhead sharks are widespread, depending on the species, in the Atlantic and Indo-Pacific, where they prefer coastal waters.
The 9 species of hammerhead sharks have a protrusion on the sides of the hammerhead. The shark’s eyes are at the end of the extension and therefore allow a 360 degree view. For a long time it was thought that the purpose of the head was to act like a wing, giving the animal greater maneuverability and allowing it to make fast turns without losing stability, although it seems that this ability is ensured rather by the vertebrae.
This hypothesis seems to have been discarded at the moment, while instead it seems that the flattened and wide head improves the electrical localization capacity; the entire structure is in fact full of Lorenzini ampoules, which allow the animal to orient itself by means of the terrestrial magnetic field and to identify electric fields emitted by other living organisms: the hammer muzzle gives the shark a larger surface, increasing by 10 times its reception capacity compared to that of tapered-headed sharks.
The dimensions of the 10 species still known can vary a lot: an adult Eusphyra blochii can measure up to 186 cm in length, while the Sphyrna lewini (the greater hammerhead shark) can exceed 4 meters in length and 350 kg in weight. Hammerhead Shark Sphyrnidae Hammerhead shark intotheblue.it
Mating in hammerhead sharks is a delicate moment, where the male bites and holds the female violently until she is allowed.
Fertilization is internal: in the marine environment this allows less dispersion of sperm and ova and therefore greater reproductive efficiency.
Embryo development is initially supported by the egg yolk. When this runs out, the yolk sac turns into a pseudo-placenta, similar to that of mammals, through which the mother provides nourishment until birth. The gestation of the hammerhead shark takes one year and allows the female to give birth to 12-15 babies.
It is an aggressive predator that feeds on fish, rays, other sharks, cephalopods and crustaceans.
The family includes 10 species, divided into two genera:
- Genera Eusphyra
- Genera Sphyrna