Unique sawshark with 6 gill slits
The Sixgill sawshark (Pliotrema warreni), the only member of the genus Pliotrema, is a sawshark of the family Pristiophoridae. Like its name, it has 6 gill slits, and uniquely the only sawshark with 6 gill slits. In general, 6 gill slits are a unique feature among all sharks. Unlike other sawsharks, the barbs on the Sixgill sawshark’s rostrum continue onto the sides of the head. Its barbels are also closer to its mouth than in other species.
Family: Pristiophoridae – Sawsharks
Common Name– Sawsharks
Common Name– Sawsharks
Status: IUCN Red List NEAR THREATENED
Average Size and Length: On average, male Sixgill sawsharks are around 3.6 feet long. At maximum, females can reach over 4.5 feet long, and males can reach over 3.7 feet long.
Teeth and Jaw: The Sixgill sawshark’s barbels are also closer to its mouth than in other species.
Head: Barbs are present on the posterior edges of larger rostral sawteeth. This is absent in other sharks. Unlike other sawsharks, the barbs on the Sixgill sawshark’s rostrum continue onto the sides of the head.
Demographic, Distribution, Habitat, Environment and Range: The Sixgill sawshark is found in the temperate and subtropical waters of the southeast Atlantic in South Africa, and the southwestern Indian Ocean in South Africa, south Mozambique and southeast Madagascar, between latitudes 23° S and 37° S, at depths of between 121 and 1,640 feet. It lives on or near the bottom, offshore continental shelves and upper slopes, in the benthic and benthopelagic zones.
Diet: The known diet of a Sixgill sawshark includes small fish, crustaceans, and squids.
The only observed predator of the Sixgill sawshark is the Tiger shark. It is highly possible that other bigger sharks may predate Sixgill sawsharks.
Aesthetic Identification: The Sixgill sawshark is the only sawshark with 6 gill slits.
Biology and Reproduction: The Sixgill sawshark is ovoviviparous. The Sixgill sawshark is thought to breed annually (7-17 developing eggs per female), giving birth to around 5-7 pups per litter. It is possible that they come to inshore pupping grounds to give birth. Sixgill Sawshark pups are born between 1.1 and 1.2 feet long, and they later mature at around 2.7 feet.
Behavioral Traits, Sensing and Intelligence: Using their sensitive barbels and ampullae of Lorenzini, Sixgill sawsharks are able to find their prey and then incapacitate them with their rostrum.
Adult Sixgill sawsharks are partially segregated from juveniles, as they naturally tend to aggregate at lower depths.
Sixgill Sawshark Future and Conservation: The Sixgill sawshark is restricted in range, they have small litters and are vulnerability to bottom trawling fishing. Though they are not sought after in any market, they are frequently caught as by-catch and disposed. This is why they are listed as near-threatened
Sixgill Sawshark Recorded Attacks on Humans: They are not a threat to humans, mainly because of their deep-water habitats.