CephalopodsPhlyum Mollusca

Cephalopods are any mollusk of the class cephalopoda, having tentacles attached to the head including cuttle fish, squid, and octopusRespiratory system- Cephalopods exchange gasses with seawater by forcing water through their gills, which are attached to the roof of the organism. Water enters the mantle cavity on the outside of the gills, and the entrance of the mantle closes. When the mantle contracts, water is forced through the gills.Circulatory system- Cephalopods have two gill hearts that move blood through the capillaries of the gill. A single systemic heart then pumps blood throughout the rest of the body. Blood is colorless and when deoxygenated, and exposed to air, turns blue.Digestive System- All cephalopods are active predators, feeding mainly on crustaceans, fish, and gastropod mollusks. Cephalopods use suckers to pull food to its two strong horny jaws with its tentacles, biting out large pieces that are swallowed so rapidly that radula is seldom used.Reproduction- Sex and reproduction in cephalopods is different than other mollusks. Sexes are separate and mating sexes are separate mating usually includes a courtship that often involves elaborate color changes. This is followed by the transfer of a spermatophore (sperm packet) by the male using either a penis or a modified arm called a hectocotylus. Most females lay large yolky eggs in clusters on the ocean floor or on any other hard substrate. Eggs develop by dividing unequally instead of in the spiral pattern of other mollusks. After a period of development within the egg, juveniles hatch out directly without the swimming larval stage. Most males and females die shortly after spawning.Nervous system- Cephalopods have the most complex nervous system out of the invertebrates. They have well developed senses and large brains. the giant nerve fibers of the cephalopod mantle have been widely used as experimental material in neurophysiology for many years.Excretory system- Most cephalopods posses a single pair of large nephridia filtered in nitrogenous waste is produced in the

pericardial cavity of the branchial hearts, each of which is connected to a nephridium by a narrow canal. The canal delivers the excretal to a bladder- like renal sac. The excrete gets pumped into sacs, to be released into the mantle cavity through a pore.Symmetry/ body plan- most cephalopods are made up of eight arms/legs, and others are made up of eight arms/legs and two tentacles. The body is normally just the arms attached to the head and they surround the mouthLife cycle- Cephalopods have very short lives. Many of the smaller species will complete a full life cycle in less than 1 year. Even the largest of the pelagic squids have a life cycle of about 7 years. In most cases, cephalopods reproduce only once. Many of the cephalopods are not well studied because they live at great depths and in the open ocean where research is very difficult and very expensive. Symbiotic relationship(s)- There is always competition for food and territory in the animal world. To avoid competing with other species it is expedient for an animal to find a ‘specific’ niche within their environment. Another way to avoid direct competition is to form a stable relationship with another species, one other than a ‘predator-prey’ relationship. This allows two species to ‘harmoniously’ share the same space and/or a food supply. Often a fish can be involved in two symbiotic relationships at once; suffering from parasitism on the one hand, and benefiting from mutualistic cleaning attention on the other. Symbiosis is always inter-specific that is it occurs only between different species; intra-specific relationships (relationships within a single species) cannot be described as symbiosis. Other important characteristics- A hectocotylus is a cephalopodic arm of a male, modified to deliver a spermatophore (sperm-containing sac) to a female. In some taxa, part of this arm can detach from the male and remain inside the female. In 1829, the famous naturalist George Cuvier first identified and described a hectocotylus in the paper nautilus but, at the time he thought that this detached arm was a parasitic worm! He named it Hectocotylus octopodis. When it was discovered that the "worm" was really a cephalopod arm, the name "hectocotylus" was kept but its meaning changed to refer to the spermatophore-transferring arm of any male cephalopod.

Work cited- Ucmp.burkeley.eduMsstarship.comThecephalopodpage.orgTolweb.orgNationalzoo.si.edu

Jimena Santillano, Lauren Nevels, Montana Grogan, Shianna Fowler

Cephalopods have a Closed circulatory system

Octopus nervous system

Overall body structure

Body plan/symmetry: Cephalopods have bilateral symmetry. Their left and right sides are mirror images of the other side since they only have one way their body can be divided into equal halves.