Sharks - Pristiophoriformes2013
By Amelia Meyer
By Amelia Meyer
Pristiophoriformes are characterised by a flattened snout, which rather resembles a saw or blade. The margins are filled with fine teeth, firmly entrenched, earning the group its scientific name, which means "saw carrier". Pristiophoriformes’ teeth alternate between being long and short, creating a distinctive serration that is most effective in the capture of prey. They have long nasal barbels, which extend from about halfway up the "sa" to create the impression of a moustache. Most Pristiophoriformes average a length of about 2.5 metres.
This group of sharks has two dorsal fins, no anal fins and five or six sets of gill arches and gill slits. These gills are located on either side of the head. The spiracles present in Pristiophoriformes are large and noticeable, often confused with ears. They are located behind each eye.
Like most other sharks species, Pristiophoriformes are ovoviviparous. This means that eggs are fertilised and hatched inside the female’s body (or, more specifically, in her oviduct). Once hatched, the young feed off the remaining egg yolk and the nutrients and enzymes secreted via the oviduct wall. They are then born alive, ready to live an independent life in the vast expanses of the ocean, without the care of training of a mother.
Pristiophoriformes live mainly in temperate and tropical ocean waters. They are often found in the waters off Florida, Cuba, the Bahamas, South Africa, southern Australia and Japan. On rare occasions, some sawsharks (as Pristiophoriformes are commonly known) have been found in estuaries, where they likely went in search of food. They tend to prefer skating along the bottom of the ocean in search of food.
When the teeth of the Pristiophoriformes break or fall out, they are replaced immediately. They use these teeth to eat small fish, crustaceans and squid. Once they have located prey (using their particularly acute Ampullae of Lorenzini to sense the electric current emitted by all living creatures), they attack it by swishing their rostral saw from side to side, effectively crippling them and rendering the prey too injured to fight or escape.
Pristiophoriformes comprises two genera;the Pliotrema and the Pristiophorus. The Pliotrema genus is made up of only one species, the Sixgill Sawshark. As its name indicates, this shark has six gill arches and slits. The Pristiophorus genus comprises several species, including the Tropical, Japanese, Dwarf and Shortnose sawsharks. These species have only five gill arches and slits.