Sawshark

A sawshark or saw shark is a member of a shark order (Pristiophoriformes) bearing a unique long, saw-like rostrum (snout or bill) edged with sharp teeth, which they use to slash and disable their prey. There are eight species within the Pristiophoriformes, including the longnose or common sawshark (Pristiophorus cirratus), shortnose sawshark (Pristiophorus nudipinnis), Japanese sawshark (Pristiophorus japonicas), Bahamas sawshark (Pristiophorus schroederi), sixgill sawshark (Pliotrema warreni), African dwarf sawshark (Pristophorus nancyae), Lana's sawshark (Pristiophorus lanae) and the tropical sawshark (Pristiophorus delicatus). Sawsharks are found in many areas around the world, most commonly in waters from the Indian Ocean to the southern Pacific Ocean. They are normally found at depths around 40–100 m, but can be found much lower in tropical regions. The Bahamas sawshark was discovered in deeper waters (640 m to 915 m) of the northwestern Caribbean. Sawsharks have a pair of long barbels about halfway along the snout. They have two dorsal fins, but lack anal fins. Genus Pliotrema has six gill slits, and Pristiophorus the more usual five. The teeth of the saw typically alternate between large and small. Saw sharks reach a length of up to 5 feet and a weight of 18.7 pounds with females tending to be slightly larger than males. The body of a longnose saw shark is covered in tiny placoid scales: modified teeth covered in hard enamel. The body is a yellow-brown color which is sometimes covered in dark spots or blotches. This coloration allows the saw shark to easily blend with the sandy ocean floor. These sharks typically feed on small fish, squid, and crustaceans, depending on species. They navigate the ocean floor using the barbels on the saw to detect prey in mud or sand, then hit prey with side-to-side swipes of the saw, crippling them. The saw can also be utilized against other predators in defense. The saw is covered with specialized sensory organs (ampullae of Lorenzini) which detect an electric field which is given off by buried prey. Saw sharks have a relatively slow life history. Mating season occurs seasonally in coastal areas. Saw sharks are ovoviviparous meaning eggs hatch inside of the mother. They have litters of 3–22 pups every 2 years. After 12 months of pregnancy, the pups are born at 30 cm long. While in the mother, pups' teeth are inverted into their mouth to prevent harm. The sharks care for their young until they are sexually mature at 2 years of age and at which point can fend for themselves. Saw sharks typically live more than 15 years in the wild They can be found living in solitary or in schools. Among the different species of sawshark, all are listed on the IUCN Red List of 2017 as either data deficient or of least concern Saw sharks do not see much human interaction because of their deep habitats.