Monday, 27 September 2010

Crabs That Made It Out Of Water - Osong; Mud Lobster

This weird inhabitant of our mangroves and creeksides is an Osong or Mud Lobster; Thalassina anomala.

It builds large mounds of mud around its burrows, and this is all I've ever seen of it, so I've stolen the rest of the information from Wikipedia.

T. anomala is a lobster-like animal which grows up to 30 centimetres (12 in) long, but is more typically 6–20 cm (2.4–7.9 in) long. Its colour ranges from pale to dark brown and brownish green. The carapace is tall and ovoid, extends over less than one third of the animal's length, and projects forward into a short rostrum. The tail is long and thin, and, like many burrowing decapods, the uropods are reduced in form, and do not form a functional tail fan with the telson.[4] Various rows of setae on the legs and gills are used to prevent sediment from reaching the gills and for expelling any which does reach them. T. anomala also makes use of "respiratory reversal" to keep the gills free of dirt.

T. anomala lives in burrows up to 2 m (6.6 ft) deep, and is active at night. Its burrowing fulfils an important rôle in the mangrove ecosystem bringing organic matter up from deep sediments. The animal's output forms large volcano-like mounds which can reach heights of 3 m (10 ft) and are vital to many other species such as Odontomachus malignus (an ant), Episesarma singaporense (a crab), Wolffogebia phuketensis (another mud shrimp), Idioctis littoralis (a spider), Acrochordus granulatus (a snake), Excoecaria agallocha (a mangrove) and termites. The burrowing activity can cause T. anomala to be seen as a pest where it weakens the bunding that surrounds prawn farms or fish farms. - please refer to for links.

This is obviously a fascinating creature, supporting a cast of other animals and plants, so it deserves study. I suffer from insomnia (but I'm not sure I could rouse myself after waking at 4am to set off tramping through mangroves). Still, I always wanted to be a nature observer like Fabre so maybe this is my chance, and I should accept the challenge.

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