Basking Shark
The basking shark is the second-largest shark species, and can reach lengths up to 30-40 feet. Weights for the basking shark have been estimated at 4-7 tons (about 8,000-15,000 pounds). They are filter-feeders who are often seen feeding near the surface with their huge mouths agape.
Basking sharks got their name because they are often seen “basking” on the surface of the water. It may appear the shark is sunning itself, but in fact it is often feeding on tiny plankton and crustaceans.
While it is at the surface, its prominent dorsal fin, and often the tip of its tail, can be seen, which may cause confusion with the Great White or other more threatening shark species when a basking shark is seen from land.
Basking sharks have been reported in all oceans of the world. They are found mainly in temperate waters but have also been seen in tropical areas. During the summer, they feed near on plankton near the surface in more coastal waters. It was once thought that basking sharks hibernated on the ocean bottom in the winter, but some research shows that they migrate to deeper waters offshore and also shed and re-grow their gill rakers, and a study published in 2009 showed that basking sharks traveled from Cape Cod, Massachusetts, all the way to South America in the winter.
Each basking shark has 5 pairs of gill arches, each with thousands of bristle-like gill rakers that are up to 3 inches long. Basking sharks feed by swimming through the water with their mouths wide open. As they swim, water enters their mouth and passes through the gills, where the gill rakers separate out plankton. The shark periodically closes its mouth to swallow. Basking sharks can strain up to 2,000 tons of salt water per hour.
Basking sharks have teeth, but they are tiny (about ¼-inch long). They have 6 rows of teeth on their upper jaw and 9 on their lower jaw, totaling about 1,500 teeth.
Basking sharks are ovoviviparous and give birth to 1-5 live young at a time.
Not much is known about the basking shark's mating behavior, but it is thought that basking sharks exhibit courtship behavior such as swimming parallel to each other and gathering in large groups. During mating, they use their teeth to hold on to their partner. The gestation period for the female is thought to be about 3 ½ years. The basking shark pups are about 4-5 feet long at birth, and they immediately swim away from their mother at birth.
Types of Marine Mammals
Cetaceans differ greatly in their appearance, distribution, and behavior. The word cetacean is used to describe all whales, dolphins and porpoises in the order Cetacea. This word comes from the Latin cetus meaning "a large sea animal," and the Greek word ketos, meaning "sea monster."
There are about 86 species of cetaceans. The term "about" is used because as scientists learn more about these fascinating animals, new species are discovered or populations are re-classified.
Cetaceans range in size from the tiniest dolphin, Hector's dolphin, which is just over 39 inches long, to the largest whale, the blue whale, which can be over 100 feet long. Cetaceans live in all of the oceans and many of the major rivers of the world.
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Sea Turtles
Sea turtles are reptiles that live in a marine or brackish environment. The flippers of sea turtles are long and paddle-like, making them excellent for swimming but poor for walking on land. Another characteristic that helps sea turtles swim easily is their streamlined carapace, or shell.
Kingdom: Animalia Phylum: Chordata Class: Reptilia Subclass: Anapsida Order: Testudines Family: Cheloniidae or DermochelyidaeSea turtles are classified in the Class Reptilia, Subclass Anapsida and Order Chelonii. There are seven recognized species of sea turtles, six of which are in the Family Cheloniidae (the hawksbill, green, flatback, loggerhead, Kemp's ridley and olive ridley turtles), with only one (the leatherback) in the family Dermochelyidae.
Sea turtles start their lives in eggs buried in the sand. After a two-month incubation, the young turtles hatch and run to the sea, facing attack by a variety of predators (e.g., birds, crabs, fish) along the way. They drift at sea until they are about a foot long and then, depending on the species, may move closer to shore to feed.
Sea turtles mature at around age 30. The males then spend their whole lives at sea, while females mate with the males at sea and then go to the beach to dig a hole and lay their eggs. Female sea turtles may lay eggs several times during a single season.
How Do Sharks Sleep
Even though sharks need to keep water moving over their gills to receive oxygen, some sharks need to keep moving to do this, while others don't. Either way, sharks, like other marine animals, don't seem to fall in a deep sleep like we do.
Some sharks have spiracles, a small opening behind their eyes, that force water across the shark’s gills so the shark can be still when it rests.
Other sharks do need to swim constantly to keep water moving over their gills and their bodies. These sharks have active periods, and restful periods, rather than undergoing deep sleep like we do. They seem to be “sleep swimming,” with parts of their brain less active, or "resting," while the shark remains swimming.