Glossary

• Adaptation
  
  A characteristic of an organism that helps the organism survive and reproduce better in its environment. An example for sharks would be their self-replacing teeth.

  Ampullae of Lorenzini
  

  Tiny spot like organs located on the head and snout of most condricthyes (and some other fish), that are used for the electroreception of the tiny electrical impulses given off by the movement of muscles. Ampullae may also be used by some species to communicate with weak electrical signals.

  Benthic
  

  Describing organisms that inhabit the region of a body of water that includes the bottom of a lake, sea, ocean, river, etc. An example of benthic sharks would be the Houndsharks, including the leopard shark (Family Triakidae).

  Cartilage
  

  The tough tissue that forms the skeleton of all members of Chondrichthyes. It provides a strong yet flexible support for the shark. Cartilage is found in other animals as well but is usually only present in embryos and young. Our nose is made of cartilage and we also have cartilage in our ears, and it forms caps on the ends of our bones.

  Caudal Fin
  

  The tail fin of a fish. In sharks, the upper lobe of the fin is generally larger and longer than the lower lobe and it speculated that the longer upper lobe generates lift for the swimming shark.

  Caudal Peduncle
  

  The part of the body of a fish between the posterior end (rear) of the anal fin base and the base of the caudal fin.

  Chemoreception
  

  The detection of chemicals in an environment. Two types of chemoreceptive organs exist. Olfactory organs (for smell) are generally located in small olfactory pits that are usually found all over the snout of a shark. Gustatory organs (for taste) are o ften located all over fish. Sharks primarily rely on their olfactory organs rather than their Gustatory organs.

  Claspers
  

  The sex organs for male members of Chondrichthyes, used for the passing of sperm to a female's organs. All elasmobranchs have interenal fertilization. The claspers (or lack of) are one of the major physical indications as to the sex of a shark and are found just behind the pelvic fin. Although there ar e two claspers, only one is used at a time.

  Countershading
  

  A form of camouflage in which either the top or bottom of an animal is lighter or darker than the other side. In aquatic environments, most often the top is darker than the bottom so that the animal will blend in with the ocean depths for a nything looking down on it and will blend in with the reflections of the surface waters for anything looking up at it. Most pelagic sharks are countershaded, including great white sharks.

  Dermal Denticle
  

  Sharks have many rows of enamel covered teeth inside their mouths and these rows extend out of the mouth as well to form the tooth-like scales that cover and protect a sharks body. These dermal denticles are similar in function to the scales of bony fish but are different in structure. In fact, it is believed that shark teeth evolved from modified dermal denticles.

  Elasmobranch
  

  A division of the Chondrichthyes that have dermal denticles (tooth-like scales) and no air bladder (they use oil in their large livers to help control their bouyancy). Includes sharks and rays.

  Gill Arch
  

  A paired structure in the throat region that supports the gill tissue. Sharks have from 5 to 7 pairs of gills, with their suporting arches.

  Gill Rakers
  

  Slender, bony or hardened extensions of the inner side of a gill arch.

  Gill Slits
  

  The openings to the gills.

  Gills
  

  The filamentous respiratory organs of fishes. Sharks have from 5 to 7 pairs of gills and most species must swim continuously to enable enough water to pass over the gills for the shark to get sufficient oxygen.

  Pectoral Fins
  

  The paired finds protruding from the "shoulder" region of a fish, just behind the gills slits.

  Pelagic
  

  To do with the open ocean or open water; away from the shore or coastline. Mackerel sharks (Family Lamnidae) such as the mako shark, are found in the open ocean.

  Spiracle
  

  A respiratory opening on the back of the head above and behind each eye. Some species of sharks have them, some don't and their size depends on the species. Most commonly found in benthic sharks.

  Subterminal Mouth
  

  When the mouth is located slightly behind and under the snout