Paracheilinus is an Indo-Pacific genus of labrid fish, known as flasher or fairy wrasses. The small fish, hardly exceeding 7 cm of length, are found at depths of 10-65 metres. The genus has been described in 1955; but only since the 1970's, when ichthylogists started to use scuba equipment, these beauties became really known. Nevertheless the first review (Allen, Erdmann & Astria Yusmalinda) was not made until 2016. A great publication to read. Not only because of the information on these fabulous fish, but also to enjoy the beautiful colors of these amazing animals.
Courting males have a spectacular neon-like flasher display. Some species, including the P. filamentosus pictured hereby, have wonderful filamentous dorsal fins. These gorgeous colors and fins are seen in terminal phase (TP) males only. Like most other labrid fishes, the fairies become sexually mature as females known as Initial Phase (IP) fish. The transformed females become TP males which grow larger and more colorful. Paracheilinus are know to form aggregations of tens to hundreds of individuals. The larger TP males defend a harem of females. The color patterns associated with their nuptial display, are used as diagnostic feature for the species. The approximately 20 species which are nowadays known, are divided into two categories. The filamentosus-group is characterized by the elongated dorsal finrays.
Allen, Gerald R.; Mark V. Erdmann & Niluh Astria Yusmalinda (2016): Review of the Indo-Pacific Flasherwrasses of the genus Paracheilinus (Perciformes: Labridae), with descriptions of three new species. - Journal of the Ocean Science Foundation, 2016, Volume 19: 18-90.
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