Giant squid

The Giant Squid (Architeuthis dux) is a deep ocean squid in family Architeuthidae, represented by as many as eight species. Giant Squid can grow to gigantic sizes. Thought to be the largest mollusk until scientists discovered the Colossal Squid which could be twice the size. Scientists believe that stories of sea monsters and water dragons could have been told when ancient sailors saw Giant Squid. It has been an elusive animal for scientists but finally discovered alive and took pictures of it on September 30, 2004 by researchers from the Natural Science Museum of Japan and the Ogasawara Whale Watching Association. The same team filmed, for the first time, a live adult Giant Squid for the first time on December 4, 2006. 

Anatomy


The anatomy of the Giant Squid is similar to any type of normal squid. The squid's body consists of two fins, a mantle, a head, eight arms and two tentacles with each having one or two rows of suckers and/or hooks and sucker rings. The Giant Squid can reach up to 18 m. in total length. Their two feeding tentacles are even longer than the entire body with a length of 10-12 m. Although they can grow to 18 m. they usually average at about 11-14 m. They can weigh to a maximum of about 900 kg. but average at 455 kg. Giant Squid are very known for having the largest eyes in the animal kingdom which are used to find the small amounts of light in the deep ocean. Their two rows of suckers on each of their eight arms and two tentacles are sub-spherical cups lined, in four vertical rows, with serrated rings of chitin. The tentacular clubs are divided into three regions: carpus, manus, and dactylus. The Giant Squid's manus has suckers along two rows. The suckers are usually never larger than 5-5.5 cm. The carpal region consists of a cluster of suckers in an irregular 6-7 rows. Like many other cephalopods at the base of the Giant Squid's arm is a parrot-like beak. It has two fins used for movement at the rear of the mantle.

It uses two large gills to breathe located within the mantle cavity. Like all other squid the Giant Squid has a closed circulatory system. Scientists have great interest in these animals because of their complex nervous system and very large brain. The Giant Squid is able to maintain neutral buoyancy in seawater because of an ammonium chloride solution which flows through the entire body. Oddly, the Giant Squid, like the tree, has growth rings to show how old it is. 

Reproduction
Not much is known about Giant Squid reproduction in particular. Scientists have used related squids to figure out parts of Giant Squid reproduction. The female will produce large quantities of eggs and sometimes more than 5 kg. The eggs average 0.5-1.4 mm. long and 0.3-0.7 mm. wide. Females have a single ovary in posterior end of mantle cavity. They also have paired oviducts where mature eggs pass leaving through the oviducal glands then through nidamental glands. Like many squid these glands produce a gelatinous material used to keep the eggs all together after being laid.

Giant Squid reach sexual maturity at about three years and males are known to reach maturity at a smaller size. The two ventral arms are modified to transfer spermatophores to the female. The single, posterior testis produces sperm that move into a system of glands that create spermatophores. These are stored in the elongate sac, or Needham's sac, which terminates in the penis where they are expelled during mating. The Giant Squid has never been observed mating but what we know is based very much on other squid species. 

Ecology


Recent studies show that the Giant Squid eat deep sea fishes and other squid species. They use their two feeding tentacles to grip their victims with serrated, saw-like sucker rings. With the prey in their grasp they bring toward their beak where the radula shreds the prey before it gets to the esophagus. Only sperm whales and some sleeper sharks are known predators of the adult Giant Squid while the juveniles are preyed on by deep sea sharks and fish. They are believed to be solitary hunters as when caught they are only individual.

They are very widespread because they are found in all world oceans. They are usually found along continental and island slopes from the North Atlantic Ocean, especially in Newfoundland, Norway, the Northern British Isles, and the oceanic islands of the Azores and Madeira, to the South Atlantic around southern Africa, the North Pacific around Japan, and the southwestern Pacific around New Zealand and Australia. They are rare in tropical and polar regions. 

Size
The Giant Squid was thought to be the largest mollusk and largest invertebrate until scientists discovered the Colossal Squid (M. hamiltoni). The colossal squid may have a mantle twice the size of the Giant Squid. It is also thought that many extinct cephalopods may have grown larger. Despite other creatures being larger the Giant Squid's size can't be overlooked. Thought to be measured at over 20 m. long but never scientifically documented. Steve 0'Shea stated that these lengths could've been found stretching the body intensely. Based on 130 examinations of beaks found inside of Sperm Whales never exceeded 2.25 m. in length. Excluding tentacles the head and arms rarely exceed 5 m. Maximum total length ,which was measured after death, is averaged at 13 m. for females and 10 m. for males from caudal fin to the tip of the long tentacles. Giant Squid show reverse sexual dimorphism. Weight is averaged at 275 kg. for females and 150 kg. for males.