What is the morphology of Cephalopoda?
What is the morphology of Cephalopoda?
Cephalopoda is the most morphologically and behaviorally complex class in phylum Mollusca. Cephalopoda means “head foot” and this group has the most complex brain of any invertebrate. Cephalopods are characterized by a completely merged head and foot, with a ring of arms and/or tentacles surrounding the head.
What do cephalopods have in common with molluscs?
The cephalopods agree with the rest of the Mollusca in basic structure, and the ancestors appear to have the closest affinity with the ancestors of the class Gastropoda. The best-known feature of the cephalopods is the possession of arms and tentacles, eight or 10 in most forms but about 90 in Nautilus.
Are there any human fisheries for cephalopods?
Human fisheries for cephalopods have been recorded at least since classical times. Coast dwellers throughout the world still catch octopuses with traditional traps of pots or baskets, while cuttlefish and squid are taken on simple hand lures. The quantities taken by these hand capture fisheries are usually unrecorded.
What type of circulatory system do cephalopods have?
Circulatory system. Cephalopods are the only mollusks with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts) that move blood through the capillaries of the gills. A single systemic heart then pumps the oxygenated blood through the rest of the body.
How do cephalopods change color?
During their evolution cephalopods lost their ancestral external molluscan shells and developed arms and suckers. Their skin can change color instantaneously thanks to direct neural control. They are efficient swimmers and propel themselves using a powerful jet of water from a ventrally situated flexible funnel.
What are the uses of light in cephalopods?
Use of light. The bioluminescence is produced by bacterial symbionts; the host cephalopod is able to detect the light produced by these organisms. Bioluminescence may also be used to entice prey, and some species use colorful displays to impress mates, startle predators, or even communicate with one another.
When did cephalopods first appear?
Cephalopods arose in the Cambrian (approximately 500 Ma), at about the same time of the earliest known vertebrates.
What is the embryological origin of cephalopod appendages?
There has been debate on the embryological origin of cephalopod appendages. Until the mid-twentieth century, the “Arms as Head” hypothesis was widely recognized. In this theory, the arms and tentacles of cephalopods look similar to the head appendages of gastropods, suggesting that they might be homologous structures.
Why are cephalopods important to humans?
Cephalopods are of considerable economic importance to humans. Many species of squid and octopus are eaten. Nautilus shells are often used decoratively, and the internal shell of a cuttlefish, or cuttle bone, is sold in the pet trade as a calcium source for birds.
How many species of cephalopods are there?
There are approximately 650 to 700 extant species of cephalopods in two subclasses and five orders. Cephalopods are strictly marine and are found in all of the world’s oceans.
