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=Opisthoteuthis=

Description
The Opisthoteuthis genus was based on a single specimen that was found in the southeastern Caribbean off Grenada, West Indies by Verrill in 1883. The reason these species were dedicated as new to the world of zoology was due to the increase of a distal group of enlarged suckers and the appearance of stout, muscular web supports that extend into the web and run along the ventral margins of the distal ends of the arms. The first species to be named to this genus was the Opisthoteuthis agassizii.

The genus Opithoteuthis are the most compressed type of cephalopod. Due to their compressed appearance they get the name flapjack or pancake devilfish. These species are primarily benthic but they have the ability to swim as well. For the majority of these species there is not much information known; and a lot of they are considered to be critically endangered. These species also contain a smooth, gelatinous body with poor developed musculature. It has also been studied that the inside of their webs are a dark brown color with purple hue and light colored suckers.

The Opisthoteuthidae included the majority of cirrates with 22 species belonging to the group. The specimen Opisthoteuthis agassizi has been found in the eastern Atlantic from southwest Irish seas to the warm waters of Spain, they are also found in the western Mediterranean, the Gulf of Guinea and off southwest Africa. The specimen Opisthoteuthis Californiana occurs in Northern California waters and Taki from off of Honshu. Two other species O. depressa and O. japonica have been found in Japanese waters. O. extensa have been stationed in southwest of Sumatra, while O. medusoides have been found off Zanzibar. O. persephone and O. pluto have both been observed in Australian waters. O. philippi is another species and has been seen in southwest India. This genus has also been found in Greenland and the waters of Iceland; this has indicated the first species of the genus in that area. The species found in these northern waters are known to have big suckers found and this could be evidence that this is the specimen O. grimaldii; but since they were frozen when they were found they could be evidence of a new species from this genus.

Thirty-one percent of the species that makeup the genus of Opisthoteuthis is O. californiana. The O. californiana is the species that was given the name flapjack devilfish by Berry in 1949. There has been a lot of new found interest in this genus but since there has not been a lot of comparative morphology there is only little that individuals know about their feeding habits, mode of life, and behavior. The true reason that little is known is due to their benthic location in the ocean which is deep and not easily accessible. The species that have been observed have came from the by-catching of commercial fisheries.

Distribution
These miraculous species live on and just above the bottom of the oceans floor. It has been shown from studies that these creatures have been found in the deepest areas of the oceans. Research done between the years of 1979-1999 led to the findings of cirrate octopods that were found in some of the deeper parts of the ocean floor two species were from the Opisthoteuthis genus. These two species where the O. massyae and the O. grimaldii.

Anatomy
The opisthoteuthis species have fields of enlarged suckers that range from one or two on mature males. They contain kidney shaped optic lopes, and have white bodies penetrated by separate optic nerve bundles. They also contain a U-shaped cell and they do not contain tooth-like structures in their sucker aperture. When it comes to the genus Opisthoteuthis there is one special thing that makes them unique and that is their body shape. As has been seen in the species O. vossi the body is depressed and flattened. The mantle of these specimen is short and rounded, while it is slightly longer than it is wide. They do contain two small fins that are laterally positioned, one on each side posterior to the mantle. In O. vossi they have a single row of suckers that are located deep in the arms.

Arms and Web
The arms of male Opisthoteuthis have modified suckers and are only in one or two fields on their tentacles which are primarily proximal and distal fields. They contain short cirri, that can be retractile into pockets. These species also have web nodules that are used for web support and present as either single, multiple or absent nodules. O. vossi has dorsal arms that are very thick, musclular and robust in males; while the female arms are not enlarged and are coequal. The arms in these species contain between 39-48 suckers form the mouth to the web, and about 40 from the web to the tip of their arms.

Head
The head of these species are large and they contain upper and lower beaks. There are also two or more bundles of optic tracts that can penetrate the body. The optic lobe is also kidney-shaped in the cross-section. On the head of the species O. vossi the eyes are large, somewhat protruding. When it comes to the optic gland is has been seen that the males have four large nerve bundles while the females only contain two.

Shell
The shell is seen to be U-shaped. The outer surface of the saddle can be seen to have grooves and it is rarely flat. The lateral walls in this species is not parallel and the spread between walls increases as it goes up to the tip.

Pigmentation and Viscera
These species have areolar spots on their bodies and it makes them very hard to detect and may make them appear to be absent. The Viscera have gills that are half-orange form and are small, spherical and have three large lamellae on the outer demibranch and three small ones on the inner demibranch; arranged like an orange. The intestine of these species can be 2 times the size of the esophagus in length. The digestive tract bends and loops and is not a simple digestive tract. The digestive gland can be either billowed or unilobed, These species also have no radula.

Behavior
There has not been much information when it comes to the studying of Opisthoteuthis. However, past research of the species O. grimaldii has been observed. When this species was observed they were resting on the bottom of the aquarium with erect mantles and their arms were curved inward toward the side of their mouth. They did have fins that were ventrally curved around the mantle and they were used to stabilize their vertical position.

Feeding & Predators
In 1956 Voss found the remains of numerous crustaceans, amphipod and mysid. In 1970 Cupka found polychaete bristles, crumaceans, amphipods, calanoid copepods, and decapod crustaceans. This information shows that Opisthoteuthis feed off the bottom and top of the ocean floor. Since these species do not have radulae it allowed for the identification of whole prey found in the stomachs of these invertebrates. It has also been shown in both species of O. Agassiz and O. Vossi that capturing and feeding on small prey has been a pattern. There was also no feeding rhythm observed in the species. Males where shown to feed on the same size and type of prey as females. Feeding for Opisthoteuthidae has shown that due to their lack of intermediate web, ballooning is a common response. Ballooning is a defense mechanism that moves the arms into the upper part of the specimen. The predators of these cirrate octopods are sharks, teleost fishes, fur seals and sperm whales.

Lifespan & Reproduction
When it comes to reproduction within these species it varies. It has been seen in some species females egg formation is continuous meaning that they spawn many times over their life. It was also seen in the species O. agassizii and O. vossi after onset of sexual maturity they become mature at a smaller size than the females. A feature or all Opisthoteuthis reproduction is the formation of thin membranous follicles around maturing eggs. Once the egg is mature the follicle splits and releases into the lumen of the ovary. The empty follicles remain attached in the ovary and shrivel once the egg is released. The egg follicles are used in the estimation of fecundity. It has also been observed that there are no non-seasonal reproductive strategy, with mature breeding females found throughout the year, and there is no difference between egg numbers between seasons. When it comes to the species O. vossi the genitalia of a male and female was dissected. The testis of the male were observed to be small and the accessory glands were seen to be the same size. When it came to the female the ovary of one of the female contained 25 ovate eggs of differentiated sizes and they were striated varying in color from red to white. It has been seen in the three species O. agassizii, O. vossi, and O. californiana that they have a reproductive strategy where asynchronous ovulation occurs in a continuous process once spawning begins. Adults spawn many times in their extended life-spans.