Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Order: Carcharhiniformes
Family: Sphyrnidae
Gender: Sphyrna
Hammerhead shark is the name given to species belonging to the Sphyrna genus, typical of tropical and temperate seas. Some species are found in deeper regions; others near the coast; and there are also those that can be seen in estuaries.
Their name is due to the fact that these animals have a flat, lateral extension on each side of their head – large and flat, with a mouth and small teeth; the eyes being located at the ends of each of these extensions. Such a shape gives them better swimming ability, including the ability to spin with great dexterity; it also allows them to have greater acuity and field of view (360 degrees), significantly helping to locate and capture prey, even the most agile ones. Other typical features of hammerhead sharks include the pronounced dorsal fin; and the ability to spot a drop of blood about a mile away.
The body size of these sharks varies. There are from those with approximately one meter to five hundred centimeters. As for the mass, it varies between 9 and 360 kilos; and, in terms of coloration, it ranges from grayish-brown to olive-green, with a lighter abdominal region.
Hammer sharks' food includes fish (including other sharks and stingrays), shrimp, crustaceans and even algae. For this, they usually hunt during the day or at dusk.
As for reproduction, they are live-bearing animals, giving rise to individuals who, at birth, become immediately independent.
Hammer sharks are not usually aggressive, and attacks on humans are very rare, most often occurring in situations where they were provoked, even if accidentally. There is no record of deaths, of individuals of our species, caused by them. However, the reverse is not true: hammerhead sharks are targeted for their skin, meat, liver (for making oil) and fins; and they are also hunted for leisure. For these reasons, some of them are threatened with extinction.
In Brazil, there are seven species:
- Sphyrna zygaena (smooth hammerhead shark). Conservation status according to the International Union for Conservation of Nature (IUCN): vulnerable, vulnerable, VU.
- Sphyrna tudes (cacao-rudela). Conservation status according to IUCN: vulnerable, vulnerable, VU.
- Sphyrna shark (short-tailed hammerhead or cambeva-paw dogfish). Conservation status, according to IUCN: minimum risk, least concern, LC.
- Sphyrna mokarran (panan dogfish). Conservation status: Endangered, endangered, EM.
- Sphyrna average (cacao-hammer). Conservation status: data deficient, data deficient, DD.
- sphyrna lewini (notched hammerhead shark). Conservation status: Endangered, endangered, EM.
CURIOSITIES:
The carved hammerhead shark (Sphyrna lewini), unlike the other species of the genus Sphyrna, swims in shoals.
The head of the short-tailed hammerhead shark (Sphyrna tiburo), rounded, looks more like a shovel than a hammer.
The wild shark (Sphyrna mokarran) and the smooth hammerhead shark (Sphyrna zygaena) are the most aggressive species of the Sphyrna genus.
By Mariana Araguaia
Biologist, specialist in Environmental Education
Brazil School Team
Source: Brazil School - https://brasilescola.uol.com.br/animais/tubarao-martelo-genero-sphyrna.htm
