Raja Radula (Rough Skate)

Classified under the term Skates and Rays.

Genus:

The Raja belongs to the Rajidae family, which contains 16 species. Over a period of time many species were placed into this category, but have since been removed to other genera in the family. Skates are a very ancient species, with records and fossil recordings dating way back to the Upper Cretaceous period.

Description:

Raja radula is a cartilaginous fish which has a rhombic shape. The body shape is due to the large pectoral fins which extend from or nearly from the snout to their tail base. The sharp featured snout is a cranial projection made of cartilage, the gills and mouth can be located on the underside of the body. Eye spots can be found on either side of the mid-line of the body,  with concentric rings of yellow bound by brown. The belly or underside of the Raja is white. The colouration can vary from being patterned to a solid colour with thorn-like or spiny structures on the top surface. Some Raja can produce a weak electrical current caused through electrical organs found in their tails.

Reproduction:

The Raja radula commonly mate in the spring, reproduction is oviparous. The female Raja can produce anywhere in the region of 80 – 154 paired eggs per year. Female Raja radula produces numerous eggs in one clutch, these are encased in leathery casing, often referred to as “mermaids purses”. The egg case measures 5.1 to 5.7 cm, oblong in shape with stiff horns protruding at each corner. Mermaids purses are deposited on the sand or flat muddy areas, taking the embryos around four months to hatch. Males mature at 30 cm in length, females at 34 cm. The maximum recorded length is 70 cm.

Habitat:

Raja radula are found in the Mediterranean Sea, western Indian Ocean and East Atlantic. They are bottom dwellers, active during day and night time, feeding mainly on molluscs, crustaceans and small fish.

Photo by Janet Bulmer @ Dive Smart Gozo

Divesite: Mgarr ix-Xini