Sepiadarium austrinum

S. austrinum is very small and round, with kidney-shaped fins on the back third of its body.[6] It has a mantle length of up to three centimeters[3] and a total length of up to four centimeters.[2] It can be transparent, yellow, or orange, with egg-shaped white leucophores.[3] S. austrinum has ten arms and tentacles[6] with nine or ten rows of suckers on each arm.[3]

S. austrinum is found in the southern Indo-Pacific[3] in southern Australia,[6] with a small population in the Spencer Gulf.[2] They are mostly found in sandy habitats in shallow,[6] sheltered waters[2] at depths up to 65 meters.[6]

S. austrinum buries itself in the sand during the day and feeds at night.[6] It is able to produce slime[3] when threatened.[1]

S. austrinum is carnivorous.[7] It feeds in the sand and near seagrass beds.[6] Its diet is mostly composed of small fish and crustaceans, including amphipods[3] and especially benthic isopods.[2]

S. austrinum reproduce from a young age;[3] immature females can also store sperm.[2] Individuals mate with multiple partners. Mating is initiated by males and there is no observed courtship behavior.[8] Males pass sperm packages to the female, who stores them in a pouch below her mouth. Males can also use a special arm to remove the sperm of other males from the pouch.[2] Females can also remove sperm from the pouch,[8] and regularly consume spermatophores.[9] They fertilize eggs by passing them over the pouch.[8] Clumps of eggs[6] are covered in sand and attached to seaweed or seagrass.[3]

S. austrinum is an annual species.[8] Juveniles settle quickly after hatching.[3]

S. austrinum survives well in aquariums, which may make them of commercial interest.[3] They may bite when handled.[7]