Some have a hard external shell, but most do not. The giant nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology; their large diameter (due to lack of myelination) makes them relatively easy to study compared with other animals. By Staff Writer Last Updated Mar 28, 2020 8:11:12 PM ET.  Several cephalopod species are polyandrous- accepting and storing multiple male spermatophores, which has been identified by DNA fingerprinting. As far as their diet is concerned, they eat crabs, crayfish, and small species of mollusks, such … A 121-pound seal can provide 8 days worth of energy - but the bear needs to eat much more in order to store up reserves. In the open ocean octopuses eat mainly prawns, fish and other cephalopods and all octopuses are carnivores that eat meat and all have beaks that tear apart their prey. A limitation of food influences the timing of spawning along with their function and growth.  Once the sun rises, they go down to deeper and darker water. , Growth in juveniles is usually allometric, whilst adult growth is isometric. All cephalopods are carnivores. The size difference between the posterior and anterior ends of this organ control the speed of the jet the organism can produce. The three subclasses are traditional, corresponding to the three orders of cephalopods recognized by Bather. As a result, their blood is colorless when deoxygenated and turns blue when exposed to air. 3. Cephalopods are carnivores and they are active and very proficient hunters. Subsequent revisions include the establishment of three Upper Cambrian orders, the Plectronocerida, Protactinocerida, and Yanhecerida; separation of the pseudorthocerids as the Pseudorthocerida, and elevating orthoceratid as the Subclass Orthoceratoidea.  Cephalopods tend to concentrate ingested heavy metals in their body tissue. Nutrients and waste materials are exchanged between the gut and the digestive gland through a pair of connections linking the gland to the junction of the stomach and caecum.  Nautilus is also capable of creating a jet by undulations of its funnel; this slower flow of water is more suited to the extraction of oxygen from the water. Doctor's office probed in wake of Maradona's death , Some cephalopods are able to fly through the air for distances of up to 50 m. While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion; water continues to be expelled from the funnel while the organism is in the air.  A hypothesis states that females reject males by olfactory cues rather than visual cues. Squids feed on everything they can grab – from plankton to large fish and even their brethren. As cephalopods have to hunt to obtain their food, they are highly mobile, and known for their voracious appetite. This is the older classification that combines those found in parts K and L of the Treatise on Invertebrate Paleontology, which forms the basis for and is retained in large part by classifications that have come later.  Cephalopods can use chromatophores like a muscle, which is why they can change their skin hue as rapidly as they do.  The teeth may be homodont (i.e. , The Kraken are legendary sea monsters of giant proportions said to dwell off the coasts of Norway and Greenland, usually portrayed in art as giant cephalopods attacking ships. Instead of vision, the animal is thought to use olfaction as the primary sense for foraging, as well as locating or identifying potential mates. The ink sac of cephalopods has led to a common name of "inkfish", formerly the pen-and-ink fish.  The Hapalochlaena lunulata, or the blue-ringed octopus, readily mates with both males and females. :225 They too have suckers, on the side closest to the mouth; these help to hold onto the prey. 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