Galaxy rasbora placed in new genus

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Microrasbora sp 'Galaxy' has been officially described and placed in a new genus.

Tyson Roberts today described the new species as Celestichthys margaritatus in a paper in the Raffles Bulletin of Zoology. He has also given the fish the new common name of Celestial pearl danio.

Roberts says that the new species is a member of the cyprinid subfamily Danioninae and is most closely related to two danionins from Inle Lake in Myanmar, Microrasbora rubescens and "Microrasbora" erythromicron.

Prior to its official description, the fish was only tentatively considered a member of the Microrasbora genus, on account of its similarity to M. erythromicron.

Roberts believes that Celestichthys margaritatus is so different to other Microrasbora that it warrants a genus of their own, possibly along with "Microrasbora" erythromicron.

The fish, which was discovered in August 2006, was first covered by Practical Fishkeeping in September and featured in the Interesting Imports column in the December 2006 issue of the magazine.

HabitatRoberts says that the species is found in a "rapidly developing" locality in the Salween basin, about 70-80km northeast of Inle Lake in northern Myanmar.

The area contains dense growths of Elodea and Anacharis, and the species is found in sympatry with a Microrasbora, possibly M. rubescens, Channa harcourtbutleri and an undescribed Yunnanilus known as the Rosy loach.

Roberts wrote: "The fish lives in small heavily vegetated ponds apparently maintained by seepage in hilly grassland at an elevation of about 1040m/3420ft near Hopong town, 30km east of Taunggyi. This is in the Salween basin, about 70-80km northeast of Inle Lake but not in the Inle drainage.

"The ponds are small and shallow, at most perhaps 30cm deep, and maintained by seepage or springs. The water is clear unless roiled with recorded temperatures of 22-24C in January 2007. The present terrestrial vegetation is open grassland.

Practical Fishkeeping reported earlier this month that the habitat had been decimated by fish exporters who had gone to the area specifically to catch the species to meet massive consumer demand for the species since it was introduced just six months ago. "Such intensive collecting could constitute a serious threat...""The extraordinary worldwide demand for this fish and its intensive exploitation are cause for concern for the welfare of the species", said Roberts.

"The number of ponds and their distribution is not known. Collectively they may be numerous and occupy a wide area, but individually they are apparently quite small and shallow, since fish collectors reportedly fish out one pond after another.

"Depending on the number and extent of the ponds and their accessibility, such intensive collecting and the ecological disturbance accompanying it could constitute a serious threat to Celestichthys margaritatus and Yunnanilus sp. unless they are more widely-distributed than known at this time.

Roberts wrote that it may be that both species have a reproductive biology that allows them to recuperate rapidly when they invade ponds that temporarily dry up and then refill, but believes that they might not cope so well when they are being simultaneously exploited by the aquarium trade.

He added: "Captive breeding of Celestichthys margaritatus could ease the pressure from commercial fish collectors on wild stocks and might be the only way for aquarists to have a continued supply of the species."

Practical Fishkeeping is advising fishkeepers not to purchase the species to reduce global demand.

Breeding

Pete Liptrot and Paul Dixon of the Bolton Museum Aquarium became the world's first fishkeepers to breed the tiny fish, after they successfully spawned the fish in late September 2006.

A number of other fishkeepers have subsequently bred the species successfully.

Liptrot told Roberts that C. margaritatus does not appear to be a true broadcast scatterer, not a depositor, like Trigonostigma or Sawbwa.

"Practical Fishkeeping is advising fishkeepers not to purchase the species...""In our aquaria, they spawn either with natural plants, such as Java moss, or artificial media, such as woollen spawning mops. Ripe females have a spot of dark pigmentation at the vent, and when selecting fish for controlled spawning we have used this characteristic with some success for indicating readiness to breed."

Liptrot says that although a number of males may chase females for long distances, spawning occurs when individual males take up a display posture alongside the female at the spawning site. The female is pushed into the spawning site and eggs and sperm are released.

The species is believed to produce around 30 eggs per spawning. The eggs take three to four days to hatch at 24.4C and are free-swimming after a further four. The fish then take cultured micro-organisms and grow quickly, taking on adult colouration at 12 weeks.

Taxonomy

The generic name Celestichthys, roughly translates from the Latin "caelestis" and "ichthys" as meaning heavenly fish. The species name "margaritatus" is Latin for "adorned with pearls", hence the common name Celestial pearl danio.

Taxonomist sources told Practical Fishkeeping that at least three scientists were simultaneously planning to describe the new species, but Roberts was the first to release his description of the popular new cyprinid.

The type specimens range in size from 14-21mm.

For more information see the paper: Roberts, TR (2007) - The "Celestial pearl danio", a new genus and species of colourful minute cyprinid fish from Myanmar (Pisces: Cypriniformes). The Raffles Bulletin of Zoology, 2007 55(1): 131-140.