Scalloped hammerhead
Sphyrna lewini
— Where the name comes from
Sphyrna is the Greek sphŷra, the hammer. Lewini recalls an early nineteenth-century English naturalist. “Scalloped” refers to the front edge of the head, which in this species is wavy rather than straight: it is the detail that separates it from the other hammerheads.
— Facts
- Group
- Fish · Actinopterygii · Chondrichthyes
- Order
- Ground sharks
- Habitat
- Coastal and oceanic water, from the surface to 500 metres
- Range
- Tropical and warm temperate seas worldwide
- Size
- 2.5–3.5 m, up to 4.3 m; 80–150 kg
- Diet
- Fish, squid, rays, other sharks
- Lifespan
- 30 years
— Characteristics
- 01
It forms schools of hundreds around seamounts.
- 02
The widened head carries an extremely dense network of electrical sensors.
- 03
It often swims rolled onto one side, which costs it less energy.
— What sets it apart
In 2023 it was found to hold its breath. To hunt it descends to eight hundred metres into water at four degrees, and to avoid losing body heat through the gills — which are enormous radiators — it closes the gill slits and stops breathing for the whole dive, some twenty minutes. It is the same principle as a free diver, arrived at by a completely different route, and nobody had supposed a fish could do it.
