TRUE: One of the rarest sharks is called a megamouth shark. TRUE: Some sharks can increase their size by swallowing large amounts of water. FALSE: Like dolphins, sharks do not have scales.
Sharks are covered with small, tooth-like scales called dermal denticles. Sharks feel smooth to the touch because their scales are designed to reduce drag. Megamouth sharks and swell sharks are both real animals! Megamouths sound scary, but they’re filter feeders and prefer plankton. Swell sharks, as their name implies, can swell up to twice their normal body size just by swallowing water. What’s your favorite shark?
TRUE: Both male and female walruses have extended tusks. TRUE: Walruses can slow their heartbeat while diving underwater to keep warm. FALSE: To maximize the ratio of insulating blubber to body size, walruses have a lower blood volume than most land animals their size.
Because walruses spend so much time underwater, they store oxygen in their blood and muscles. They actually have an enormous blood volume–two to three times as much as other land animals their size. Do you know any interesting ways other animals have adapted to their surroundings?
TRUE: Sea stars have an eye on the end of each arm. (Called an ocellus, it’s one of the simplest eyes in the animal kingdom and has no cornea or lens.) TRUE: Sea stars have two stomachs. (Food begins in the cardiac stomach and moves to the pyloric stomach.) FALSE: Sea stars have a water vascular system that filters toxins from the water.
While sea stars do have a water vascular system for movement, it does not filter water. The system consists of tons of tiny tube feet on their underside that suck up and force out water, creating enough hydraulic pressure for sea stars to move across the ground. Since there is no way to filter the water, they are extra vulnerable to water pollution; Think of sea stars next time you are choosing whether to use eco-friendly detergent for your laundry. For more tube feet awesomeness, watch the above video from the Seattle Aquarium.
Seahorses are not vegetarians; they eat by hooking their tail around objects on the seafloor and use their snouts to snack on tiny, live crustaceans that float by. A tail that grasps objects is called a prehensile tail. You can see how the seahorse may have evolved into its unusual shape in the video above (courtesy of Nature). Even cooler: Did you know males seahorses carry and birth the young?
Many people don’t realize seahorses face many threats in the wild. You can help conserve these animals by refusing to buy them–either live, for your aquarium, or dried as souvenirs.