Question

1.

a) What are some unique (derived) characteristics of the Goblin Shark?

b) Does the Goblin Shark lose any characteristics that other similar animals have?

Answer 1

Goblin shark is a rare species of deep-sea shark. It gets its name because of its goblin-like appearance. It is the only extant representative of family Mitsukurinidae, a lineage which is about 125 million years old. Hence, they are sometimes referred to as a living fossil.

They inhabit upper continental slopes, submarine canyons, and seamounts. It is sluggish in nature. They feed on teleost fishes, cephalopods and crustaceans.

Unique (derived) characteristics of the Goblin Shark

(1) The coloration of the skin is unique. Their bodies range from pinkish grey to pink color. The color deepens with age and young sharks will be almost white. The color is rare in sharks. The species derived this color due to visible blood vessels beneath the skin.

(2) Jaws are unique and they use ram feeding (a type of prey capture that is unique to many mackerel sharks). The velocity of movement of lower jaw is two times higher than upper jaw and has a unique pattern of opening and closing the mouth during the strike. This behavior is absent in other sharks. It is believed to be an adaptation to compensate the poor swimming ability.

(3) They are inactive and sluggish in their movement. Its skeleton is found to be reduced and poorly calcified. Muscles too are poorly developed, and its fins are soft and small. Hence, they tend to be ambush predators.

(4) The teeth is the main part of the jaw, and are long, slender and narrow.

(5)They have a well-developed basihyal (similar to a tongue) on the floor of the mouth drops which expands the oral cavity and helps in sucking the water and prey.

(6) Another feature unique to goblin shark is the presence of flattened snouts that protrude from top of its head.

(7) Presence of ampullae of Lorenzini is yet another unique feature of Goblin sharks. Its long snout is covered with specialized sensing organs called ampullae of Lorenzini. These structures help them to sense even minute electric fields produced by the adjacent prey. Sensing this, it is able to catch the prey quickly. These snouts tend to get smaller with increasing age.

Characteristics absent is goblin sharks found in other sharks

(1) Modern sharks have cartilaginous skeleton which is absent in goblin sharks.

(2) Teeth of goblin sharks were slender and narrow unlike the razor-sharp teeth of other sharks.

(3) Normally, sharks rely on eyesight for seeking food. But in goblin sharks, vision seems to be less important than other senses, since it uses these senses to move and catch prey. Hence, vision is not well developed in goblin sharks.