The Flathead Slipper Lobster (Thenus Orientalis) is a very unusual looking clawless lobster even by slipper lobster standards. In Australia they are known as the Morton Bay bug. They are only active at night and during the day they are almost never seen, being adept at hiding . Often when one does see them out at night they are still part covered in sand.
Previously there was only one species in the Genus thenus, but it now seems that there are at least three but up to five species. One of the distinctions seems to be habitat and one new species is found on sand in shallow turbid waters and another is found in depths below 30 meters.
The body is collectively covered in a hard carapace with the eyes on the edge of the carapace. The head has two pairs of antennae, one large and flattened pair covering the front of the lobster and the other set are normal. Flathead Slipper lobster are predominantly a light reddish brown color. Dependent on how long the period is since the shell change , there is often growth on the shell. The body is flattened and the upper surface is a light purple brown to brown colour with darker purple and brown dots. The legs are a lighter orange-yellow colour and have purple on the joints. On the rear of the abdomen there is a single spine which points backwards when the tail is folded. This can be seen in the image below.
IN THE WILD
They are nocturnal and are rarely if ever be seen out during the day. With their flattened shape they are able to dig themselves into the sand quite quickly. They can swim backwards to escape predators by flapping their tail but only sem to resort to swimming when desperate. Compared to the other slipper lobsters whom we regularly see on shallow reefs, this species is more often seen out on the sand than on a reef.
Flathead Slipper Lobsters are found on sandy areas and on sand between coral reefs as well across the Indo West Pacific area from depth of 5 meters to 120 meters. Being nocturnal they hide during the day and feed at night.
Slipper lobsters are nocturnal feeders and eat a variety of molluscs, shrimp, crabs worms and sea urchins. They use their powerful legs to pull apart mollusks. Their main predators include triggerfish, groupers and octopuses.
Flathead Slipper lobsters have separate sexes and at maturity which is generally around three years begin breeding. Males deposit a sperm packet on the underside of females and females have between 54000 to 240000 eggs which are carried under their tail.
The eggs start off bright orange and as they develop so they go a dark muddy brown colour. Once the eggs hatch they become planktonic, free floating in the water table for up to six months. Very few of the larvae survive until adult stage.
Slipper lobsters are eaten throughout their range and taste exactly the same as normal lobsters except they do not grow that large. They are trapped in fish traps in Tanzania and Zanzibar.
FLATHEAD SLIPPER LOBSTER CLASSIFICATION