Sepioteuthis lessoniana, also known as the big fin reef squid, glitter squid or oval squid, is a species of loliginid squid.  This squid can be identified by its large oval fins. These squids are small to medium size averaging 35 cm (14 inches).  From the moment they hatch they have the ability to change their colors. These squids however only have a life expectancy of less than a year and they grow very quickly.  They can usually be found around coral reefs or near the shore line. 

These squids have large eyes that are covered entirely by a secondary transparent cornea and they have strong short beaks with 7 rows of teeth. Their bodies are almost completely covered by their fins and they have a narrow blue or white line at the point where their bodies and fins meet. They have an ink sack that is small and pear- shaped. 

The squid has large chromatophores on the upper surfaces of its head, mantle and arms. These allow the squid to change color, however naturally squid are white or transparent. They also have another form of coloration called iridophores in their heads; this lets them change their colors between green and red. They are also 1 of only 2 species of squid that have Leucophores. Leucophores are a reflector-type structural coloration that reflects ambient light, such that they are white in white light, green in green light, and so on.

It is difficult to determine the gender of these squids however some researchers believe the females are slightly smaller. These squids usually feed on marine organisms like prawns. They themselves are usually preyed on by tuna, swordfish and other fish. They usually found within 100m of the surface. They typically stay close to the shoreline near rocks and reefs. They are more active at night and move to deeper waters during the daylight.  They are not solo animals, these means they swim, nest and hunt in groups. However they don’t swim parallel to each other like other marine species.  

These squid have strong positive behavior towards light. They are even attracted to divers’ lights! Although they have a hearing range of about 400Hz to 1500Hz they can also detect vibrations. 

Squids produce more eggs in warmer waters. When these eggs hatch they become cannibalistic. Stronger hatchlings eat the weaker ones.  Their life spans may also reduce in warmer waters because they develop faster in these environments.