Sharks feature in blockbuster movies as blood-seeking villains however in reality they’re far more fascinating – as well as complicated – than they’re frequently depicted in popular culture.
Based on fossilised teeth and scales, scientists are of the belief that sharks have been around for more than 400 million years — this is long before the dinosaurs. The ocean’s main predators have evolved into almost 500 species which come in all different sizes and colours and also have varying behaviour.
The Anatomy Of A Shark
Sharks are members of a collective of almost only marine and predaceous fishes. There are around 250 species of sharks, from the 2 feet pygmy shark right up to 50 feet giants. They are found in all seas, however, are most abundant in warm waters.
Some sharks may enter large rivers, and one fierce freshwater species lives in Lake Nicaragua. Most are predatory, however the largest species, the whale shark and the basking shark, are quite harmless plankton eaters. Dogfish is the name for members of various families of small sharks; these should not be mixed up with the bony dogfishes of the mud minnow as well as the bowfin families.
Sharks Are Heavy Fishes
This means that they possess neither lungs nor swim bladders. Sharks’ skeletons are made of cartilage as opposed to bone. This, along with large deposits of fat, partly solves their weight problem. Nonetheless, most sharks need to keep moving to breathe and to stay afloat.
These are good swimmers. The extensive spread of the pectoral fins and the upward curvature of the tail fin provide lift. The widespread movements of the tail give drive. Their tough skins are studded with minute, toothlike structures which are called denticles.
Sharks Have Pointed Snouts
Sharks’ crescent-shaped mouths are set on the underside of their bodies and contain a number of rows of sharp, triangular teeth. They have respiratory organs called gills, normally five on each side, with individual gill slits that open on the body surface. These slits form a prominent row and lack the covering that are found over the gills of bony fishes.
How Do Sharks Breathe?
As with most fish, sharks breathe via taking water in through the mouth and then passing it out over the gills. Normally there are two extra respiratory openings on the head which are called spiracles. A shark’s intestine has a bespoke spiral valve, which boosts the area of absorption.
Fertilisation is internal in sharks. The male has paired organs that are called claspers for introducing sperm into the cloaca of the female shark. Members of most species bear live young, however a few of the smaller sharks lay eggs that contain much yolk and are enclosed in horny shells. Compared to bony fishes, sharks often tend to mature later and reproduce quite slowly.
You don’t need to be afraid of these gracious beasts, like New Zealand pokies online they are majestic and exciting to watch. However, you need to be afraid for them. There are more confusions and untruths about sharks as opposed to almost any other group of animals on the planet. While many individuals fear sharks, it is the sharks who should be fearing us.
