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= Euprymna hyllebergi =

General Overview
Euprymna hyllebergi is a species of bobtail squid belonging to the Sepiolidae family and is native to the eastern Indian Ocean.

Physical Appearance
E. hyllebergi mantles, heads, and arms are covered in chromatophores which are pigmented cells that can expand and contract. The mantle is a thick, dome-shaped pocket of skin that covers the body. Attached to the middle of the mantle are two fins used as stabilizers and as a way to propel the bobtail squid. The head and eyes are located at the bottom of the mantle with the arms and tentacles coming out beneath the head. E. hyllebergi have eight short arms which are tube-like structures used for hunting and eating prey. On the arms, there are small suckers that act as suction cups and are used to better grasp prey. Male and female bobtail squid have two tentacles that are longer than the arms and are used for capturing prey(4). Male bobtail squid have an extra arm called the hectocotylus which holds and transfers spermatophores to females (9).

Life Cycle
E. hyllebergi females deposit single, white pyramid-shaped egg capsules. 2 hours after being laid, the outer layer of the eggs become a brown color and, after 5 days, eggs become transparent with the embryo visible. After an incubation period of 12 to 16 days, E. hyllebergi hatchlings emerge in a planktonic state with a visible internal yolk sac. After 6 to 8 hours, E. hyllebergi leave the planktonic state and become benthic (1).

When mating, males perform courtship displays to attract female mates. Once successful, males hold the female and insert the hectocotylus into the female’s mantle cavity where fertilization occurs(5). After fertilization, females then select an area to lay her egg capsules. Once the area is selected, the egg capsules are laid and the female swims away to select a new area for the remaining capsules. After laying the final capsule, the female swims into the water column where her swimming slows, and her mantle begins to turn yellow and then transparent. The female then soon sinks down to the substrate and dies between one to four hours after depositing her final egg capsule.

Behavior
E. hyllebergi have been observed burrowing into the sand and burying themselves. When burying themselves, E. hyllebergi use a mix of rocking their mantles, fin beating, and water jetting to dig their way into the sand. To completely bury themselves, they sweep their third arm backwards to collect sand grains and place them over their heads. When not in the presence of sand, E. hyllebergi rest near corals and rocks (1). As a form of defense, E. hyllebergi can discharge ink which then confuses and distracts predators, allowing them time to escape. E. hyllebergi are often seen swimming at night rather than during the day. While swimming, E. hyllebergi are able to camouflage through disruptive coloration which occurs when the mantle becomes transparent with visible brown spots.

Feeding
E. hyllebergi typically feed on live prey at night by capturing prey with the tentacles and arms. When hunting for prey, the tentacles are used for capturing the meal while the arms are used to hold it in place. E. hyllebergi have a diet consisting of small shrimp and crustaceans

Distribution
E. hyllebergi are found in the eastern Indian ocean, specifically in the Andaman Sea off Thailand. Nearly all collected specimens were found in the Andaman Sea and off the Gulf of Thailand (4).