Dorsal fin Piked Dogfish
Species: S. acanthias
The spiny dogfish has a double dorsal fin. The anterior dorsal fin is larger than the posterior dorsal fin. The spiny dogfish has the presence two spines, one immediately in front of each dorsal fin. The spines carry a poison secreted by glands at their base. both of which have a spine which can inject venom causing strong pain lasting for several hours, and very occasionally death in humans. Dorsal fins of these fishes are known to function to varying degrees as stabilizers and as propulsive elements that augment thrust from the caudal fin. However, little is known about the ability to control three-dimensional conformation of the dorsal fins during swimming, which may alter the force balance during locomotion.
About the Animal
The piked dogfish is a compact shark species reaching a maximum of 39 inches in males and 49 inches in females. With a slender body and pointed snout. Their skin is grey to brown on top and becomes increasingly paler, or even white, on the belly with small white spots running down each side of the body. The spiny dogfish is a highly migratory species–one individual tagged in Washington made a 5,000-mile journey to Japan. The spiny dogfish also breaks records when it comes to gestation. These sharks have the longest pregnancy of any vertebrate at 22 to 24 months, or two years! Eggs develop in the female, gaining nutrients from yolk sacs, and live young are born at 20 to 33 centimeters. Even at a young age, newborn spiny dogfish pups may hunt fish two or three times their size.