Cephalopods

1. Corresponding Reading Material ~ Squid section in Lab Manual ~ Levinton: Chapter 8 Cephalopods

2. The Phylum Mollusca General Characteristic: 1. Bilaterally symmetrical 2. Possess a mantle which secretes the shell 3. muscular foot 4. radula (file-like feeding structure); modified in some classes 5. Possess a one way gut 6. Reproduces sexually There are 7 different classes within the mollusk phylum: ~ Class Polyplacophora - Chitons ~ Class Aplacophora - Mollusks without shells ~ Class Monoplascophora - Mollusks with one shell ~ Class Schapoda - Mollusks with a tubular shell ~ Class Gastropoda - Gastropods, snails and their relatives ~ Class Bivalvia - Bivalves ~ Class Cephalopoda - Cephalopods, squids and octopuses

3. The Class Cephalopoda Are the most highly evolved mollusks and invertebrates. General Characteristics: 1. A funnel derived from the molluscan foot 2. Chitinous beaks 3. Complex eyes. 4. Have a head surrounded by a foot divided into arms 5. Are carnivorous 6. Well organized nervous system 7. Have complex behaviors

4. Cephalopod Evolution • The earliest cephalopods were shelled mollusks that were probably similar to limpets. They appeared 500 million years ago during the Upper Cambrian Period. • The ammonite with its coiled shell appears in the Devonian period around 400 mya same time as sharks). This organism shows a great advancement in mobility. Ammonites continued with numerous developmental variations and became the dominant cephalopod until the end of the Cretacious period about 144 mya. • The driving force of the extensive evolutionary change seems to be related to the changes in the continental configuration between 500 and 140 mya. These changes brought about severe alterations in climate, major reconfigurations of continental shelves, reduction in estuaries and wetlands, and changes in oceanic current patterns.

5. The Nautilus The nautilus is different from many of the other cephalopods because it has retained its shell.

6. The Diversity of Cephalopods Today there are approximately 650 different species of cephalopods.

7. Ecology of Cephalopods • Cephalopods are strictly marine. They usually live in the deeper waters of the ocean, but some species are known to live in shallower waters. • They are found from the warm waters of the tropics to the near freezing waters by the poles. • Most species are nektonic (live in the water column far above the sea floor) • All cephalopods are predators. They use tentacles to capture prey, and they have beaks that tear apart the flesh.

8. The Blue Ring Octopus • bdxg It lives in warm, shallow reefs off the coast of Australia, New Guinea, Indonesia, and the Philippines. It has a life span of about 1.5 years. The Blue Ring Octopus is the most venomous octopus. It catches prey with its arms, bites it with its tough beak, and kills it by delivering a poison in the saliva. The poison is a neurotoxin that is strong enough to kill a human.

9. The Giant Pacific Octopus • largest species of octopus in the world. Most individuals weigh less than 100 lbs but an individual captures near Victoria, British Columbia in 1967 weighed 156 lbs. and was almost 23 ft from arm tip to arm tip. • mainly lives on the continental shelf of the north Pacific ocean. • After hatching, the Giant Pacific Octopus swims towards the surface and spends 4-12 weeks drifting in the plankton until it reaches a size of >14mm. • They typically live 3-5 years.

10. The Giant Squid • the largest invertebrate to ever live on Earth. No one has ever seen a giant squid alive in its own habitat. • Scientists know of their existence through the study of specimens found in the stomachs of sperm whales, washed up on beaches, or caught in fishermen’s nets. • can grow up to 21.3m (70ft.) long. Their arms alone can grow to be 10 feet long while their tentacles can extend as far out as 36 feet. • They can weight up to 4 metric tons.

11. The Color Changing Cuttlefish • Cuttlefish, and other cephalopods change colors by using chromatophores. All of this is under the control of the cuttlefish’s advanced nervous system. When the muscles are relaxed, the surface area of the sac is small and the color is not expressed. When the muscles contract the surface area becomes much greater and the color is seen. • Cuttlefish use the change in color for mating purposes and to communicate.

12. Cephalopod Behaviors Navigation and Spatial Maps: • species Octopus vulgais found in Bermuda is a cental place forager- uses a spatial map. • finds and lives in homes of shells, beer bottles, or sheltered niches. environment. • This same species of octopus also seems to cover different parts of its home range one after another on subsequent hunts and days which suggests they also have a working memory.

13. Cephalopod Behaviors “Playing” behavior: A group of Octopus at the Seattle Aquarium were subjected to 10 trials over 5 days. On the first trial each was given a floating bottle. During this trial all the individuals grabbed the bottle and brought it to their mouths. Several of the octopuses jetted water at the bottle during later trials. But two of the octopuses aimed water jets that made it circle the tank and come back to them for further jets. One octopus set it up so that the bottle circled the tank for a round trip time of 2 minutes. The other made it return every 30 seconds.

14. Conservation • Currently cephalopods have no conservation status • Very little known about cephalopod natural history. • The California Department of Fish and Game recommended a management plan for the squid fishing industry. This plan was signed into law on September 20, 2001. • The Australian Giant Cuttlefish’s population was decimated in 1997 and 1998. In 1998 the commercial season was closed early and a complete closure occurred in 1999 and 2000. • concerned local sport divers have rallied to establish permanent refuges and long-term conservation plans.