Moon wrasse

Moon wrasse
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Labridae
Genus:	Thalassoma
Species:	T. lunare
Binomial name
Thalassoma lunare (Linnaeus, 1758)

The moon wrasse, Thalassoma lunare, is a wrasse of the Labridae family found in the Indo-Pacific oceans at depths of between 1 and 20 m. It has a tendency to stay at the coral reef and surrounding areas. [Eyewitness Handbooks, Aquarium Fish, Dick Mills]. Moon wrasses are carnivorous and tend to prey on fish eggs and small invertebrates. These include various bristle worms, shrimp, young crabs, brittle stars, and even the occasional urchin.

Its length is up to 30 centimeters, although they tend to average about 25.

Juveniles are blue on the lower half of the body. They have a black spot in the middle of the dorsal fin and a black blotch on the caudal fin base. As they mature, the spot turns into a yellow crescent, hence the name. The body is green, with prominently marked scales. Coloration of the head ranges from blue to magenta, with a broken checkerboard pattern.

Moon wrasses are active fish, said to be moving all day long. They are also territorial, nipping, chasing, and otherwise harassing fish that get in their way.

Being diurnal, wrasses have strong vision, although they also have a decent sense of smell. At night, they rest in niches often under rocks or other such structures. If needed, a moon wrasse may dig out a space under a rock by repeatedly swimming through it until it fits without struggle.

They are protogynous hermaphrodites, all starting off as female and changing to male, a process which, for the moon wrasse, takes only ten days. Some, but not all moon wrasses live in groups consisted of a dominant male, and a "harem" of about a dozen other wrasses, some female and some male. The alpha male is brighter colored, and at every low tide hour, he changes from green to blue, and goes into a show of attacking and nipping all the other wrasses. This is his way of showing his dominance to the rest of the males and keeping the females in check. During breeding season and before high tide, the alpha male turns completely blue, gathers up every single female, and the spawning frenzy begins. Sometimes, non-alpha males will have extra large testes, and they will ejaculate from a greater distance. [Australia, an Ecotravellers Guide, Hannah Robinson, 2004]

Moon wrasses may live up to a decade in captivity, although this is shorter in the wild. They are popular fish in the aquarium trade, due to their hardiness, bright colors, and engaging behavior. They are renounced for their ability to tolerate spikes in nitrite, and eat bristle worms, a fish keeper's pest. Aside from this, though, moon wrasses have no commercial value. This species is a common sight in tropical waters, and is not considered to be endangered.

References

• Froese, Rainer, and Daniel Pauly, eds. (2006). "Thalassoma lunare" in FishBase. May 2006 version.

http://www.petco.com/product/104902/Lunare-Wrasse.aspx The New Encyclopedia of the Saltwater Aquarium, Greg Jennings, 2007

The Inspired Aquarium: Ideas and Instructions for Living with Aquariums, Senske, 2006

Under the seas, the Ecology of Australia's Rocky Reefs, Neil Andrew, 2000