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Sand shark

life science Maturity 5-7 Next article →

Sand sharks belong to a group of mackerel sharks called Odontaspididae. These sharks live in temperate and tropical waters across the globe. They inhabit most oceans except for the eastern Pacific. You can often find them in the Mediterranean and Adriatic Seas. They frequently swim near the ocean floor in the surf zone. This tendency to migrate toward shorelines is why they are called sand sharks.

Odontaspis noronhai
Odontaspis noronhai

The physical appearance of a sand shark helps it survive. Their bodies are usually brown with dark markings on the upper half. These markings actually disappear as the sharks mature. They possess a large second dorsal fin on their backs. Their most striking feature is their needle-like teeth. These teeth are long, narrow, and very sharp with smooth edges. Some teeth even have one or two smaller cusplets on the sides. These specialized teeth are perfectly adapted for impaling fish.

Odontaspis ferox-Requin Dents02-Montpellier-4819~2015 10 02
Odontaspis ferox-Requin Dents02-Montpellier-4819~2015 10 02

Sand sharks use a very unique hunting strategy to catch prey. They are able to gulp air from the surface of the water. The shark then collects this air inside its stomach. This air makes the shark buoyant, which means it floats more easily. Because of this buoyancy, they can approach prey while remaining virtually motionless. They are most active at night when they hunt for food. Their main diet consists of small fish. However, they also eat squid and various crustaceans.

Odontaspis noronhai
Odontaspis noronhai

Reproduction in sand sharks is a very intense process. A female sand shark only develops two embryos at a time. Each embryo develops in its own uterus. The largest and strongest embryo will consume its sibling while still in the womb. This process is called intrauterine cannibalism. Because of this, sand sharks have one of the lowest reproduction rates of all sharks. This makes them very vulnerable to population declines. They are currently listed as a vulnerable species in much of their range.

Odontaspis ferox-Requin Dents02-Montpellier-4819~2015 10 02
Odontaspis ferox-Requin Dents02-Montpellier-4819~2015 10 02

History and classification for these sharks have changed due to science. The genus Odontaspis was named by Agassiz in 1838. There are currently two living species in this genus. The first is Odontaspis ferox, known as the smalltooth sand tiger. It was named by A. Risso in 1810. The second is Odontaspis noronhai, the bigeye sand tiger. It was named by Maul in 1955. Scientists once included the genus Carcharias in this family. They did this because the sharks look very similar.

Synodontaspis gracilis
Synodontaspis gracilis

Modern technology has changed how we group these animals. Scientists used mitochondrial DNA analysis to study their genetics. This analysis showed that Carcharias is significantly basal to Odontaspis. This means they are not as closely related as they look. In fact, Odontaspis is more closely related to the rest of the Lamniformes group. Because they do not form a single group, the family was called polyphyletic. Consequently, Carcharias was moved into its own family called Carchariidae.

Synodontaspis gracilis
Synodontaspis gracilis

Humans and sand sharks rarely have dangerous encounters. Sand sharks are not known to attack people. They are generally not aggressive animals. They may only harass divers who are actively spearfishing. In North America, some divers even visit World War II shipwrecks to see them. These sharks often make the wrecks their home.

Odontaspis noronhai
Odontaspis noronhai

Protecting these sharks is a major challenge for conservationists. Conventional fisheries management might not be enough to help them. This is because of their specific life-history characteristics. A report from the PEW Charitable Trusts suggests new management ideas. They suggest using approaches used for large mammals that have declined. This could include prohibiting the retention of vulnerable species. It could also involve regulating international trade to help rebuild their populations.

Odontaspis ferox-Requin Dents02-Montpellier-4819~2015 10 02
Odontaspis ferox-Requin Dents02-Montpellier-4819~2015 10 02
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File:Odontaspis noronhai.jpg
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File:Synodontaspis gracilis.jpg
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