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131 THE RAFFLES BULLETIN OF ZOOLOGY 2007 THE RAFFLES BULLETIN OF ZOOLOGY 2007 55(1): 131-140 Date of Publication: 28 Feb.2007 © National University of Singapore THE “CELESTIAL PEARL DANIO”, A NEW GENUS AND SPECIES OF COLOURFUL MINUTE CYPRINID FISH FROM MYANMAR (PISCES: CYPRINIFORMES) Tyson R. Roberts Research Associate, Smithsonian Tropical Research Institute Email: ABSTRACT. – Celestichthys margaritatus, a new genus and species of Danioinae, is described
  131 THE RAFFLES BULLETIN OF ZOOLOGY   2007 THE RAFFLES BULLETIN OF ZOOLOGY   2007 55 (1): 131-140 Date of Publication: 28 Feb.2007© National University of Singapore THE “CELESTIAL PEARL DANIO”, A NEW GENUS AND SPECIESOF COLOURFUL MINUTE CYPRINID FISH FROM MYANMAR(PISCES: CYPRINIFORMES) Tyson R. Roberts  Research Associate, Smithsonian Tropical Research Institute Email:  ABSTRACT. –  Celestichthys margaritatus , a new genus and species of Danioinae, is described from a rapidlydeveloping locality in the Salween basin about 70–80 km northeast of Inle Lake in northern Myanmar. Malesand females are strikingly colouful. It is apparently most closely related to two danioins endemic to Inle,  Microrasbora rubescens  and “  Microrasbora ” erythromicron . The latter species may be congeneric with thenew species. The new genus is identified as a danioin by specializations on its lower jaw and its numerousanal fin rays. The colouration, while highly distinctive, seems also to be characteristically danioin. The danioinnotch (Roberts, 1986; Fang, 2003) is reduced or absent, but the danioin mandibular flap and bony knob(defined herein) are present. The anal fin has iii8 1  /  2 –10 1  /  2  rays. In addition to its distinctive body spots andbarred fins the new fish is distinguished from other species of danioins by the following combination of characters: snout and mouth extremely short; premaxillary with an elongate and very slender ascending process;mandible foreshortened; body deep, with rounded dorsal and anal fins; modal vertebral count 15+16=31;caudal fin moderately rather than deeply forked; principal caudal fin rays 9/8; scales vertically ovoid; andpharyngeal teeth conical, in three rows  KEY WORDS. –   Hopong; principal caudal fin rays; danioin mandibular notch, knob, and pad; captive breeding. INTRODUCTION A tiny cyprinid fish of exquisite beauty discovered inMyanmar in August 2006 is being exported as a tropicalaquarium fish. Photographs of it have appeared in numerouswebsites and Internet forums as “galaxy Rasbora” or “galaxyMicrorasbora” It is here described as a new genus and speciesof the subfamily Danioinae. It appears to be most closelyrelated to “  Microrasbora ” erythromicron  Annandale, 1918,a tiny colourful species endemic to Inle Lake (Salween basin,central Myanmar). The fish lives in small heavily vegetatedponds apparently maintained by seepage in hilly grassland atan elevation of about 1,040 m (about 3,420 feet) near Hopongtown, 30 km east of Taunggyi. This is in the Salween basin,about 70–80 km northeast of Inle Lake but not in the Inledrainage. It is apparently near the watershed or divide betweentwo moderately large Salween tributaries, the northwardflowing Nam Lang and the southward flowing Nam Pawn.The extraordinary worldwide demand for this fish and itsintensive exploitation are cause for concern about the welfareof the species. MATERIAL AND METHODS Most of the specimens of the new fish utilized in this studyare aquarium specimens provided by Bangkok aquaristKamphol Udomritthiruj. The main series of specimens werealready dead, dying, or in poor condition when they werepreserved in ethyl alcohol. These were eventuallysupplemented by a small number of live specimens sent fromBangkok to Singapore and facilitated by Patrick Yap.Comparative material of  Microrasbora rubescens  and“  Microrasbora ” erythromicron  was provided by Kampholand the Zoological Reference Collection of the RafflesMuseum for Biodiversity Research. Observations oncolouration and chromatophores were made from photographsof both sexes taken by Kamphol, including those publishedwith this article, and on specimens immediately afterpreservation in formalin.Variation in colouration in a series of photographs of a highly-colourful fish such as Celestichhys margaritatus  new genus,new species, may have as much to do with differences inlighting and photographic processing as to differences inindividual colour of fish specimens. Individual variation incolouration of course may be recorded photographically, but  132 Roberts: Celestial Pearl Danio from Myanmarthis should be done by photographing samples of severalsamples simultaneously under as near-identical conditions aspossible. Even so it will be difficult to eliminate differencesin colouration due to intensity or angle of the light source(s)and differences in chemical or electronic processing. Thephotographs published here represent the natural life coloursof the species.Observations of the jaws of Celestichthys  and  Microrasbora were made on specimens cleared and stained with alizarin.Vertebral counts were obtained from radiographs. Abdominalvertebrae are defined as all of the vertebrae with their hemalprocesses or spines anterior to the first elongate anal finpterygiophores; this is actually the second anal finpterygiophore (the first pterygiophore is very short). The restof the vertebrae are post-abdominal (with hypural half centrum counted as one). The first elongate anal invariablyextends anteriorly very clearly in front of the hemal processof the first post-abdominal vertebra as thus defined.Abdominal vertebra include the first four vertebra associatedwith the Weberian apparatus. Individual centra of the firstfour vertebrae are sometimes clearly distinguishable in goodradiographs but more often not. Thus the vertebral countgenerally is made beginning with the first centrum bearing anormally formed pleural rib. In Danioninae, as in cyprinoidsgenerally, this is vertebra 4 (Grande & Young, 2004).Observations on the Weberian apparatus and some otherosteological features also were obtained from radiographs.Attempts to counterstain specimens of Celestichthys ,  Microrasbora rubescens and “  Microrasbora ”  erythromicron with alcian blue and alizarin were uneven and otherwiseunsatisfactory and therefore extensive osteologicalcomparisons are not provided here.Four males and two females 15.6–17.1 mm were preparedfor scanning electron microscopy. The specimens were fixedin 10% formalin for several days then dehydrated for threedays by passing them from distilled water through a series of increasing concentrations of ethyl alcohol beginning at 30%and ending with three changes of absolute alcohol over threedays. After dehydration the specimens were dried in a criticalpoint drier, mounted with silver paint on stubs, gold platedwith an ion sputterer and carbon coated with a vacuumevaporator. Viewing was done with a JEOL JSM T22OAscanning electron microscope.The following institutional abbreviations are used: ZRC,Zoological Reference Collection, Raffles Museum forBiodiversity Research, National University of Singapore;USNM, Division of Fishes, Smithsonian Institution,Washington DC; and CAS, California Academy of Sciences,San Francisco. Lengths of specimens are standard lengthsexpressed in millimetres (mm). Celestichthys , new genus Type species. –   Celestichthys margaritatus , new species, bymonotypy.  Diagnosis. –   Celestichthys  differs from all previously-knownAsian Cyprinidae in its distinctive head and body shape, smallupturned mouth with shortened jaws, unique colouration, and9/8 principal caudal fin rays (whereas  Microrasborarubescens , type species of the genus  Microrasbora , has 10/9,the usual count for the family Cyprinidae; and“  Microrasbora ” erythromicron  has 9/9). It is furtherdistinguished by caudal fin moderately rather than deeplyforked; pharyngeal teeth conical, three-rowed; scales in lateralseries 25–26; and body without lateral line canal (no scaleswith lateral line pores).In size and shape of head, jaws, body and fins it is most similarto another diminutive and highly colourful cyprinid,“  Microrasbora ” erythromicron  Annandale, 1918, endemicto Inle Lake. That species, which may represent the same oranother new genus, has entirely different colouration and 9/ 9 principal caudal fin rays. All other Asian cyprinids so faras known, including  Microrasbora rubescens  Annandale,1918 (type species of  Microrasbora Annandale, 1918) have10/9 principal caudal fin rays except for  Danionellatranslucida Roberts, 1986,   and  D. mirifica Britz, 2003, and“  Microrasbora ” erythromicron  with 9/9 and Paedocypris Kottelat, Britz, Tan & Witte, 2005,   with only 8/8. While theyalso are danioins,  Danionella  and Paedocypris  apparently arenot closely related to the new genus and species. They arerelatively slender fish, even smaller than Celestichthys , butwith increased numbers of post-abdominal vertebrae andelongate lower jaw.A 24.8 mm  Microrasbora rubescens  has numerous finetubercles of about equal size in three or four rows extendingthe length of the ventrolateral margin of the mandibles. Themandible in Celestichthys  apparently is non-tuberculate. Theanal fin of  M  . rubescens , with ii11 1  /  2  rays, has a distinctlyconcave posterior margin, giving it almost a falcate shape.This differs from the anal fin of Celestichthys , which has aconvex margin and only ii8 1  /  2 –9 1  /  2  rays. The caudal peduncle,similar in both sexes, is much more elongate than in Celestichthys . In these respects, “  Microrasbora ” erythromicron  is again like Celestichthys . Celestichthys margaritatus  new species (Figs. 1–3)  Material examined. –  Holotype: male, 21.2 mm (ZRC 50706),Myanmar, isolated small, heavily-vegetated pools at the foot of a mountain near Hopong town 30 km east of Taunggyi, elevation1,040 m (about 3,420 feet), coll. Kyaw Toe, Oct.2006.Paratypes: Female, 20.5 mm (ZRC 50707), same collection data asholotype; 303 specimens: 14.0–19.6 mm (ZRC 50708), samecollection data as holotype; 40 specimens: 14.1–19.3 mm (CAS224434), same collection data as holotype; 40 specimens: 13.9–20.5mm (USNM 388753), same collection data as holotype.  Description. – Dorsal fin rays ii7 1  /  2 –8 1  /  2 , anal fin raysiii8 1  /  2 -10 1  /  2 , caudal fin rays v-i9/8v, pectoral fin rays 11–12,pelvic fin rays 7. Trailing edge of second dorsal fin raysmooth, without serrations. Dorsal and anal fins with convex  133 THE RAFFLES BULLETIN OF ZOOLOGY   2007margins. Caudal fin moderately forked; upper and lower lobesnearly equal, broadly rounded. Danioins have branched dorsalfin ray counts of 6–7 and 8–16, with no previously-describedspecies spanning the interval 7–8 (Fang, 2003: 722). Dorsalfin srcin far anterior to a vertical drawn through anal finsrcin and distinctly posterior to a vertical line drawn throughpelvic fin srcin.Scales in lateral series 24–25. No scales with lateral line pores.Dorsum scale count from head to dorsal fin srcin 14–15 (first3–4 scales bilateral, rest dorsomedian). Scale rows betweendorsal and anal fin srcin 7. Circumpeduncular scales 8. Scalysheath of anal fin with a single row of 5–6 scales. The anteriorand posterior circuli and the radii are similar in  M. rubescens ,“  M.” erythromicron  and Celestichthys , but in the latter twothe shape of the scale is vertically more elongate than in  M.rubescens  (Fig. 2).Gill rakers absent. Pharyngeal arches small but stout.Pharyngeal teeth in three rows with 2/3/5 teeth, as in many Fig. 1. Celestichthys margaritatus , new species. Above: holotype, 21.2 mm mature male (ZRC 50706); below: paratype, 20.5 mm maturefemale (ZRC 50707). Images: Kamphol Udomritthiruj. Asian Cyprinidae, including  M. rubescens  and “  M. ” erythromicron . The teeth are conical.Head rounded, its length 3.9–4.1 times in standard length.Snout very short, its length only one-half of eye diameter.Eye large, in anterior half of head. Horizontal eye diameter10 times in standard length. Barbels absent (as in mostDanioinae).Mouth very small, jaws entirely in front of orbit (Fig. 3).When mouth is closed jaws are oriented at an angle of 45ºupward. See discussion for remarks on “danioin notch.”Nostrils normally developed, anterior nostril with lowrounded rim from the posterior margin of which arises thenasal flap (Fig. 2a). Area surrounding posterior nostril andimmediately posterior to it largely covered with exposedelongate cilia (apparently olfactory cilia) (Fig. 2c-d). Suchcilia are usually found only on the lamellae of the olfactoryrosette inside the nasal capsule (largely covered over by thenostrils and nasal flap).  134 Roberts: Celestial Pearl Danio from Myanmar Fig. 2. Celestichthys margaritatus , male, 16.4 mm (scanning electron micrographs): a, head in side view showing nostrils, eye, and jaws(scale bar = 500 μ m); b, left half of lower jaw with mandibular flap; c, row of taste buds on lower jaw (scale bar = 50 μ m) (similar taste budspresent on lips, barbels, and widely scattered on the head); c and d, exposed olfactory cilia in shallow depression posterior to nostrils (scalebars = 20 μ m and 5 μ m). Body deep and strongly compressed, much more so than in  M.   rubescens  but similar to “  M. ” erythromicron . Greatestbody depth (just anterior to dorsal fin) 3.0–3.1 times in SL.Caudal peduncle sexually dimorphic, length 4.8–5.2 timesin SL in both sexes, height 6.5 times in SL in males but 7.3times in SL in females.Total vertebrae 30–32, with a strong mode at 31 (N=40).Frequencies 30(7), 31(26), 32(7). Abdominal and post-abdominal vertebrae often equal or nearly equal in number,with a modal count of 15+16 (n=13). Counts of abdominalvertebrae range from 13 to 16 and of post-abdominal vertebraefrom 15 to 17. Post-abdominal vertebrae more numerous thanabdominal by 2–3; abdominal vertebrae more numerous thanpost-abdominal by 1–2 in several specimens. Tuberculation. –  Multicellular keratinous tubercles occur onthe head, jaws, dorsal surface of the paired fins and elsewhereon many cyprinids (especially bottom dwellers). Tuberclesoccur on the head and especially on the jaws including themandibular flap ventrolateral margin of the mandibles inmany Danioinae. These may occur in both sexes (e.g. in  Daniorerio ), or only in males (e.g. in Sundadanio   axelrodi )(Roberts, 1989: 69-70, Fig. 48). Tubercles have not beenobserved on the head or elsewhere in either sex of  Celestichthys margaritatus.  No tubercles were found on themandibular flap any of the male or female specimensexamined with SEM (Fig. 2b). Taste buds are often presentin the sites occupied by tubercles in larger danioins and othercyprinids (Fig. 2c). Unculi. –  Most Cyprinidae (probably including manyDanioinae) have unicellular keratinous projections or unculion the ventral surfaces of the paired fins and on the lips and/ or horny sheaths of both jaws. Unculi also often project fromthe surfaces of cyprinid multicellular tubercles. No unculiwere found on any of the male or female specimens of C.margaritatus  examined with SEM.  Eggs. –  Dissection of several 18 to 19 mm females revealedeggs of different size classes. The largest eggs are 1.0–1.3mm in diameter, slightly smaller than the pearl spots on the
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