Spiny dogfish

Description

The spiny dogfish has dorsal spines,no anal fin,and white spots along its back.The caudal fin has asymmetrical lobes,forming a heterocercal tail.The species name acanthias refers to the shark's two spines.These are used defensively.If captured,the shark can arch its back to pierce its captor.Glands at the base of the spines secrete a mild venom. Males mature at around 11 years of age,growing to 80–100 cm (2.6–3.3 ft) in length;females mature in 18–21 years and are slightly larger than males,reaching 98.5–159 cm (3.23–5.22 ft).Both sexes are greyish brown in color and are countershaded.Males are identified by a pair of pelvic fins modified as sperm-transfer organs,or "claspers".The male inserts one clasper into the female cloaca during copulation.