Cephalopod Lab Report : Bsc 117 Essay Example

a larger internal shell called a cuttlebone, and fins for propulsion. Octopuses are the most evolved of cephalopods and through evolutionary adaptation have lost their shell, indicating successful adaptations to their environment.

Nautiloids are characterized by having an external shell, and are among the earliest cephalopods discovered. They have a planispiral shell shape with interconnected internal chambers, allowing the animal to withstand great pressure but resulting in the loss of buoyancy control. One prominent feature first noticed by many about the cephalopods is the size of their head compared to the rest of their body. Surprisingly, these heads do in fact hold large brains, and cephalopods are widely regarded as the most intelligent invertebrates.With highly developed eyes and other sensory organs, cephalopods are able to retain information and learn by example or through trial and error. Possessing the most complex nervous system of any invertebrate, giant nerve fibers found in the mantle have been a favorite experimental specimen of neurophysiologists for many years.

Cephalopods have good vision, and all but one species see in black and white. This is strange because cephalopods have the ability to change color in the presence of a predator or when they feel threatened.When changing color they use their chromatophores to change brightness and pattern in accordance with their surroundings. Their ability to blend with their surroundings comes from cells such as iridophores and leucophores that reflect light from the environment. In addition to the highly developed nervous system, cephalopods are the only molluscs with a closed circulatory system.

Their vascular system that has two gill hearts that move blood through the capillaries of the gills, and a single systemic heart that pumps

oxygenated blood through the rest of the body.Compared to the tail propulsion used by common fish, the jet propulsion that cephalopods use is a very energy consuming way to travel. In the larger species the efficiency of propulsion diminishes so they usually use their fins or arms for locomotion. Some octopuses are even able to “walk” along the seabed using only the tips of its arms. Reproduction and sex in cephalopods is very different than that of other molluscs.

Sexes are separate and mating usually includes a color changing courtship.From there the spermatophore is transferred from the male to the female via a penis or modified arm called a hectocotylus. The spermatophore enters the female mantle cavity and fertilizes the eggs. Development of the eggs is different in the fact that they divide unequally instead of in the spiral pattern like that of other molluscs. The female lays her eggs in a large yolky cluster of eggs on the ocean floor or any other suitable substrate. After hatching, cephalopods skip the larval stage that most molluscs undergo.Many males and females die shortly after spawning. Most coloidea live short lives with rapid growth and tend to use a semelparous reproduction strategy; they lay many small eggs in one batch and die afterwards. Nautiloideas, however, tend to live for a long time and like to lay a few very large eggs in each batch.

Importance in Ecosystem:Cephalopods play a mutualistic part in their ecosystem and are both predator and prey for many animals, including humans. Most species of squid are less than 75 cm long, but many can grow to much larger lengths.One of the largest is the giant

squid and was thought to be extinct until one was recently captured off the coast Antarctica. Its mantle was 2.

5 meters and scientists speculate that this was just a juvenile, indicating that adults can grow up to nearly two times that size. The only know predators of these gigantic cephalopods would be large whales, such as sperm whales. Although the importance of cephalopods as predators is still hazy, cephalopods are usually active predators that use their tentacles to catch and trap their prey.They then use their sharp beak to tear apart their food and ingest it.

Hard parts of the prey, which are needed for identification of prey, are usually discarded resulting in biased diet estimations. They usually feed around dusk and the most important prey for the cephalopods is crustaceans along the ocean floor. Many of the mid to small size cephalopods stick to eating crustaceans and small fish, while cannibalism is noted in some of the larger species. Cephalopods are also hunted as prey and serve to many as a source of food.The role of small fish as predators to the cephalopods is not as well understood as that of sharks, swordfish, birds and mammals.

Cephalopods remains can be found in fish, but recent studies have shown that they are not a predominant portion of the common fish diet. These cephalopod species are identified as having no commercial value, and are usually small adults. Birds, such as the King Penguins in the Falkland Islands, readily eat the cephalopods, the ommastrephid squid, being the most important in terms of biomass.In addition, commercial fisheries are now targeting this squid as well as seals and large species of

halibut.

Anthropogenic Importance:Cephalopods occur in large numbers and form one of the greatest potential food resources of the oceans. They are eaten in most parts of the world and have been widely accepted in North America and northern Europe. Cephalopods also are indirectly important to humans since they are a large part of whales, seals, fish, and seabirds diet. In 2000, about 3. 6 million metric tons of cephalopods were harvested.

This is a huge number and totals 4. % of the world’s total marine catch. Many of these squid, cuttlefish, and octopus will go on to be served as food around the world. Fishermen also use cephalopods as bait to catch other desirable marine life. The cephalopods represent one of the most highly developed of all animals that are not related to fish, mammals, or other animals with backbones. The nerve tissues of giant squids have helped scientists understand the basic functioning of the human nervous system.

On rare occasions, cephalopods have been known to be harmful to humans.Being bitten by an octopus can be very painful and sometimes can even contain deadly toxins. It has even been seen that schools of the large Humboldt squid will attack people who have fallen into the water.

Conclusion:

Cephalopods are regarded as the most intelligent invertebrates possessing amazing traits contributing to their evolutionary success. Scientists have been studying these animals for quite some time, resulting in a greater more thorough understanding of the human nervous tissue.Cephalopods can be either predator or prey, and species range in all sizes.

The largest cephalopod, Mesonychoteuthis hamiltoni, can reach sizes longer than a city bus and the smallest, Idiosepius notoides, are small enough to fit on

your fingernail. Many use a propulsion system to move but the larger species use their arms or tentacles. The “walktopus” can even use the tips of its arms to “walk” along the sea floor. Today cephalopods have become an important food source for many animals accounting for nearly 5 % of the world’s total marine catch and being eaten as a delicacy is catching on fast.

They have withstood the test of time and through natural selection have become perfectly adapted to their environment. It is easy to tell that humans and the world will benefit from the great diversity and quantity of these “one of a kind” animals. Works Cited "Cephalopods. " Biology. By Neil A. Campbell, Jane B.

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