Sharks can have bellybuttons and other facts
Hyderabad: The first thing that pops into most people’s minds when they think of sharks is of big dumb fish with pointed teeth that are to be greatly feared. But someone, who spends their days studying these creatures, knows just how wrong that image is. For one thing, the diversity of sharks is astounding. The […]
Hyderabad: The first thing that pops into most people’s minds when they think of sharks is of big dumb fish with pointed teeth that are to be greatly feared. But someone, who spends their days studying these creatures, knows just how wrong that image is. For one thing, the diversity of sharks is astounding. The differences between species can even make it seem like some of these animals are barely related.
Sexual segregation
A new research shows that significant differences can even exist between male and female members of the same species. The South African great white sharks revealed that females don’t always make the switch from eating fish as youngsters to eating seals and other marine mammals when they’re older. Instead, some females specialise on fish prey and use different habitats to males. And, if the females are spending more time in coastal areas than males, they may be more likely to be caught in in-shore fisheries and bather safety nets, as well as being exposed to more pollutants.
Differences in the way the sexes use resources are called sexual segregation and are fairly common in sharks. The reasons behind sexual segregation can be complex, sometimes involving different temperature or nutritional requirements or the need for females to give birth in special nursery habitats.
Shapes & Size
The sizes of the more than 400 species, for example, range from a 20-cm dwarf lantern shark to an 18-metre whale shark.
They also come in a surprising variety of shapes, including the flat and ray-like angel shark and the rounded and eel-like frilled shark. Accordingly, their teeth come in a wonderful variety of forms too, from crushing plates used to crunch crabs in smooth-hound sharks, to circular blade-like teeth that give cookie-cutter sharks their name.
Reproduction
Sharks have a variety of reproductive types too. Some lay eggs (that also come in a bunch of different shapes and sizes depending on the species). Some develop eggs that hatch inside them, producing pups that then develop in the uterus and are born later.
Others give birth similarly to mammals, with a placenta and umbilical cord. The umbilical cord attaches between the pectoral fins and when the pups are born, they’re left with an umbilical scar, effectively a belly-button, which is visible for a few weeks until it heals up completely. A few shark species have also been found to have “virgin births”, reproducing without a sexual partner.
Personality
Individual sharks have recently been shown to be just that: individual. Researchers have found that lemon sharks show a preference for hanging out with familiar individuals. However, just like humans, some sharks are more sociable than others. Port Jackson sharks seem to have best friends that they like to spend time with year after year, and several shark species have been found to be made up of individuals with different behavioural types, or personalities.
You can even tell individual sharks apart based on their appearance. NASA developed the algorithm that is now used to identify individual whale sharks by their spot patterns (it was originally used to map stars). Each whale shark has a unique pattern that can be identified like a fingerprint. Several other sharks and rays are now identified by various pattern features. White sharks can be identified by the notches on their dorsal fins, as well as other distinguishing features.
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