Vertebrates :)

Well, I next started in on Vertibrates (marine ones that is). Subphylum Vertebrata is a subphylum in the phylum Chordata, which is the one I talked about last. They have a backbone, or vertebral column. The first class studied was Class Agnatha. This class is characterized by what it does not have. It does not have a jaw, paired fins, and scales. Their skeletons are made of flexible cartilage. They feed by suction, using their mouth and multiple rows of teeth. Only two orders of fish exist: hagfishes and lampreys. Hagfishes are bottom-feeding scavengers that live in tunnels; they dig in the muddy bottoms of cold waters. They bore into their prey ad eat them from the inside out. They also can secrete a thick slime onto their skin that detects predators. They can tie their bodies into a sliding knot in order to clean the excess slime from their bodies and give them leverage when eating food. Lampreys are hatched in fresh water, but migrate to marine water for their adult lives and return to fresh water, often the exact location as where they were born, for reproduction. They use multiple hook-shaped teeth within their round mouth to attach themselves to their hosts and suck their blood. Greg F. aptly called them “vampire fishes.” :)

Class Condricthyes contains sharks, rays, and skates. This group mostly contains cartilaginous fish. They have a caudal fin, or tail fin, the dorsal fins on the back side of the body, pectoral fins, which give them steering ability, and pelvic and anal fins, which are used for stabilization. Sharks have an acute sense of smell; the olfactory organs are blind sacs that have external openings called nares that allow water to flow into the sacs, and the receptors sense the water, and the brain interprets it. Sharks often swim their entire lives; when sharks swim, water is forced into their mouths and passes over their gills. If a shark stops swimming, the water moving past the gills is greatly reduced, diminishing the available oxygen. However, they can get oxygen when not moving, but it’s hard for them. Sharks have teeth specific for the type of food they eat. Their teeth re-grows quickly; an entire row of teeth in a shark can be replaced in 10 days. Sharks do not feed on humans as their natural prey. This is one of my pet peeves. Only several species of sharks have actually attacked sharks. If a shark does attack a person, it is often because the human is swimming over the shark on a surfing board etc, and the shark mistakes it for its prey and attacks it. Humans do not have enough fat on them to be of any use to sharks as food. Or at least some humans. :) I dissected a shark, and I got some pictures too. Here are the pictures:

Lamprey pictures:

Here’s a website with lots of shark and ray pictures:

http://www.elasmodiver.com/sharkive%20index.htm