32 Sharks: The Animal Answer Guide
in the uterus (see “Do sharks lay eggs or do they give birth to live young?”
in chapter 6). Sand Tiger embryos develop sharp, recurved teeth early in
their development that should be superior to blunt teeth when munching
on fellow pups. Researchers dissecting recently dead, pregnant female Sand
Tigers have actually been bitten while probing around inside the mother.
Some sharks and rays use teeth for purposes other than feeding. In the
few that have been observed mating (see “How do sharks reproduce?” in
chapter 6), the male holds onto the female with his mouth by seizing her
body or fins. Male Blue Sharks, Prionace glaucus, have longer teeth than fe-
males, presumably as an aid in holding onto females. In some rays, tooth
type differs seasonally between males and females. Male Atlantic Stingrays
(Dasyatis sabina) have the same characteristically blunt teeth as the females
outside of the breeding season, a type useful for crushing clams. During the
breeding season, however, the males grow pointed cusps on their teeth that
they use for courtship. These teeth are shed after the reproductive season.
A particular tooth type does not necessarily limit a shark’s diet. The
loose attachment of teeth to jaw can be turned to advantage. Whitespotted
Bamboo Sharks (Chiloscyllium plagiosum) have sharp, spiky teeth appropri-
ate for feeding on soft-bodied prey such as fish and squid. However, these
sharks also eat crabs that have hard shells. When biting down on a crab, a
Whitespotted Bamboo Shark allows its functional teeth to hinge backward,
overlapping the replacement tooth immediately behind it. The shark now
has multiple rows of depressed teeth that form a flat surface more appro-
priate for crushing hard prey. The teeth spring back up after a bite is taken.
What is the skeleton of a shark made of?
Sharks don’t have any real bone in their bodies. Most of their skeleton is
made of cartilage, some of which is hardened or has fibers running through
it for strengthening. Cartilage (the stuff that stiffens our nose and ears) has
a number of advantages over bone. It is lighter than bone and more flex-
ible. Hardened cartilage, as found in a shark’s vertebral column, skull, and
spines, gets its stiffness from deposits of calcium phosphate crystals. Shark
fins are stiff, but the stiffness comes from a horny substance and not from
calcification. Shark teeth aren’t bony either but are instead evolutionarily
modified scales covered in hard enamel.
Does a shark have senses like ours?
Yes and no. Read further.http://www.ebook3000.com