Rostrum (anatomy)

Invertebrates

• In crustaceans, the rostrum is the forward extension of the carapace in front of the eyes. It is generally a rigid structure, but can be connected by a hinged joint, as seen in Leptostraca.
• Among insects, the rostrum is the name for the piercing mouthparts of the order Hemiptera as well as those of the snow scorpionflies, among many others. The long snout of weevils is also called a rostrum.
• Gastropod molluscs have a rostrum or proboscis.
• Cephalopod molluscs have hard beak-like mouthparts referred to as the rostrum.

  Vertebrates

• Some cetaceans, including toothed whales such as dolphins and beaked whales, have rostrums which evolved from their jawbones. The narwhal possesses a large rostrum which evolved from a protruding canine tooth.
• Some fish have permanently protruding rostrums which evolved from their upper jawbones. Billfish use rostrums to slash and stun prey. Paddlefish, goblin sharks and hammerhead sharks have rostrums packed with electroreceptors which signal the presence of prey by detecting weak electrical fields. Sawsharks and the critically endangered sawfish have rostrums which are both electro-sensitive and used for slashing. The rostrums extend ventrally in front of the fish. In the case of hammerheads the rostrum extends both ventrally and laterally.