Xyrichthys pentadactylus is one of many species of razor fish, or more commonly known as razor wrasse. Razor wrasses are adapted to life on open sandy reefs, and all possess highly compressed bodies which look paper thin from the front, enabling them to slice through the sandbed with ease as they dig around hunting for food and to hide in when threatened.
Razor wrasses are not commonly found in the aquarium trade, and are virtually unknown to many aquarists. Although some are beautifully colored, a great deal are drab and grow to large sizes which makes them unsuitable for captivity. X. pentadactylus is a moderately sized species with amazing coloration, perfect for the home aquarist. Another characteristic shared by almost all razor wrasse, sans a few species, is the discontinuation of the dorsal fin.
When the dorsal finnage is opened up and displayed, you will realize that the first few rays are separated from the others. The “double-dorsal” characteristic gives the fish a rather unique appearance, akin to wearing a hat. Earlier this year, we introduced two razor wrasses, Xyrichthys novacula and the closely related, Novaculops halsteadi. The fish above, X. pentadactylus, is a close relative to X. novacula, but share a different range. X. pentadactylus is an Indo-pacific species but not often found in the hobby as well. Coloured dark green with a bright pink crosshatched belly and an almost cartoon like blunt head, the fish adds diversity and character to my home aquarium. It’s lucky that I chanced upon this specimen, but it isn’t the first time that i’ve seen them for sale.
Here is a video that i’ve managed to take just before it dove into the sand to sleep. The video quality is not very good as the tank lights are turned off and only ambient lighting is used, but it shows that the razor wrasse can travel and move around even under the sand, and is really, quite interesting to watch as the sandbed churns in a ghost-like eeriness and all that is left behind is dust.