Sawback angelshark

The sawback angelshark (Squatina aculeata) is an angelshark of the family Squatinidae It is one of rarest species of sharks known to date, and one of the three species of angelsharks that inhabits the Mediterranean. The Sawback angelshark lives in sandy and muddy bottoms of the ocean at depths of 30–500m.

Their size at birth ranges from 30 to 35 cm. As adults, female measurements range from 137 to 143 cm, while males range from 120 to 122 cm. Their relative weight based on the size of the shark for males is between 12.7 kg and 24.0 kg. In females, they weigh anywhere from 22 to 32 kg. The females grow to be larger than the males because they need to be able to carry and support their young.

The development of the males was measured in three stages, juvenile, subadult and adult. The juvenile males had short and flexible claspers and the testes were membranous and barely developed. The subadult males showed changes in the claspers involving slight calcification and elongation in the sharks. It is in the adult stage that the claspers are fully elongated and calcified, and are rigid. The spermatozoa had developed and sperm production became possible in these adult sharks.

The three development stages for females are the same for males: juvenile, subadult and adult. The juvenile females have whitish ovaries, and extremely small ovaries, which need to be seen under a microscope. In the subadult females, they have primarily white, translucent follicles, differentiated genital areas, and developed ovarian glands. In adult females, the fully functional ovaries exhibits developing and fully developed follicles.

Their eyes are larger than their spiracle. The frontal cephalic membranes are lobed; external nasal flap fringed; spiracle with 13–14 pseudo branchial lamellae. Has concave between eye, eye spiracle distance <1.5 x eye length. They have between 19 and 24 teeth, the average of the species being 21 total teeth. Their pectoral fin base at is least half of their fin length. They have denticles on their back which are large-based, almost pyramidal, with a line of median spines. The lower belly of the shark has denticles only on outer edges of pectoral and pelvic fins Obtains large thorns atop its head in a row down its back. The colour of the angelshark is light brown mottled with dark brown, with white sports arranged on the head and some of the body. Obtains dark blotches on head, back, the fin bases and tail. The species contains no ocelli.

The range of the sawback angelshark continues to decrease as their population declines. They range along the Eastern Atlantic in Senegal, Gambia, and Sierra Leone. They also inhabit the Southern Mediterranean coastline in Algeria to the eastern basin, and along the northern coast from Turkey possibly to Albania, although their presence is unknown further east. Its presence is unknown in Algeria, Sardinia, Malta, Libya, Egypt, Israel, Lebanon, Syria, southern Cyprus, Crete, and Western Mainland Greece.

Subtropical; offshore species, outer continental shelf and upper slope, demersal, marine. Usually found on muddy bottoms. 30–500 m (98–1,640 ft) down.

As with other angelsharks, the sawback angelshark is a bottom-dweller that tries to camouflage at the bottom of the ocean in order to ambush and capture its prey.