Possible range extension of Rasboroides nigromaginatus(?)

Note : - Sudasinghe et al., 2018 based on a phylogenetic study, resolved the issues raised in this post at    the end. Now Rasboroides nigromarginatus is considered as a synonym of Rasboroides vaterifloris

Sudasinghe, H., Herath, J., Pethiyagoda, R. and Meegaskumbura, M. , 2018, ‘Undocumented translocations spawn taxonomic inflation in Sri Lankan fire rasboras (Actinopterygii, Cyprinidae)’. PeerJ [Online journal], (20 December 2018). Link >>

Endemic genus Rasboroides is restricted to the shaded rain forest streams of South-western wet zone from Kalu to Walawe drainages.  A single species of Rasboroides formerly known as Rasbora vaterifloris was divided into four different species recently base on morphological differences. Table 1 summarized some of their morphological features with distribution in the country base on Batuwita S. et al., 2013. 

Rasboroides nigromarginatus (Black Line Golden Rasbora/කලු-ඉරි හල්මල්දන්ඩියා[Kaluiri Halmaldandiya])

Rasboroides nigromarginatus was first described by a German scientist H. Meinken in 1957 as a new species base on a single specimen collected from the ‘Ceylon’ without knowing exact locality. He had found that specimen among some exported ornamental fishes from Sri Lanka and considered it as a synonymy of Rasboroides vaterfloris (Deraniyagala, 1958 & Pethiyagoda, 1991). It has not been collected since then until the rediscovery in 1994 from Athwelthota by R. Pethiyagoda & K. Manamendra Arachchi and independently in 2010 by members of Wildlife Conservation Society, Galle. 

With the recent review of Rasboroides group it is now considered as a valid species occurs only in Athwelthota area of Kalu river basin. Here we record a possible range extension of this species again on Kalu river basin but considerable distance away from the type locality.  We would like to keep exact locality undisclosed, considering past experiences of   extinction of some rare endemic fish species from certain localities without proper protection, due to excess collection for export and local ornamental fish industry (Ex. Extinction of bright color Rasboroides species from Puwakpitiya Dola in Indikada Mookalana and total extinction of them from Madakada Mookalana - Chamikara S., 2012).  

We were able to observe and photograph four live specimens of Rasboroides in a tributary of Kalu River in the Kiriella area of the Rathnapura district.  The stream is bordered to a rubber plantation but with well wooded  banks with several indigenous plants. One specimen we observed was bit bigger than other three and lack black color of un-branched ray of dorsal and other fins on the leading edge (However it is slightly visible on the dorsal fin ray on nearly half of its length – See picture).  But three small specimens had prominent black lines along leading edge of all their fins. Other than that large specimen was more yellowish on its dorsal and upper half of the side and fins while small specimens had more silver in dorsal as well as venter and sides.  However orange red color of dorsal fin and orange of caudal fin was not observed in any specimens. Taking accurate measurements of the specimens was impossible with living fishes due to obvious reason. But approximate size of the large specimen was visually estimated as 30mm and about 20mm of small three.  Body depth of all 4 specimens was around 30% SL.

Three out of four species of Rasboroides have been recorded from Kalu river basin and R. vaterifloris reported from Small shaded streams and rivulets in and around Gilimale is the closet Rasboroides locality recorded so far to the locality of the current specimens. However morphological features of them much resembles to the R. nigromaginatus hitherto only recorded from Athwelthota area.  
     Is this a hybridization of R. nigromaginatus and R. vaterifloris? Why only small individuals have prominent black ray on leading edges of fins? Are they juveniles and would it be faded away in adult specimens?  Or we are here dealing with two different species (We have observed that small individuals are schooling separately during our observation)? More research need to be done before come to a conclusion especially with exact measurements and scale counts with preserved specimens. But which is beyond our scope and for the time being we would like just to report this observation and highlight the need of conducting more research on our ichthyofauna and also most importantly conserving of their habitats with special consideration towards the streams and rivulets outside the protected forest reserves in Southwestern wet zone of the country.  Because those water sources are highly vulnerable to the human activities (We got to known that excessive fishing have been practicing in above area some time even with using explosives which destroy every living inhabitants of the stream from big to small). There are enough possibilities of discovering new species not only of fishes but also other animals as well in these unprotected areas and it is needed to conserve them before those ‘to be discovered’ species would be vanishing from the world before even known to the scientific community.

The Habitat of Rasboroides nigromaginatus(?)

	R. vaterifloris	R. nigromaginatus	R. pallidus	R. rohani
Male –Upper body color	Golden brown lightening on side to silvery, scattered with melanophores	Golden orange, sides and venter silver	Dorsal color varies from pinkish-grey to dark golden yellow, lighter latterly. Silver on venter	Dorsally greyish-yellow, golden yellow on sides and silvery-white on venter.
Male- belly	Silver	Silver	Silver
Dorsal Fin	Hyaline with scattered melanophores	Orange red, Longest un-branched dorsal fin ray black along its entire length.	Golden yellow	Golden yellow
Anal fin	Hyaline with scattered melanophores	Yellow with scattered melanophores. Unbranched rays of leading edge black	Golden yellow	Yellow-orange
Pectoral fin	Hyaline with scattered melanophores	Yellow with scattered melanophores. Unbranched rays of leading edge black	Golden yellow	Golden yellow
Pelvic fin	Hyaline with scattered melanophores	Yellow with scattered melanophores. Unbranched rays of leading edge black	Golden yellow	Golden yellow
Caudal fin	Greenish Yellow	Orange.	Lighter with upper lobe hyaline	Yellow-orange on lower lobe. Upper lobe hyaline.
Sclera		Upper third of sclera deep Orange	Dense melanophores on sclera above and below giving effect of black bar on eye (Bothe M and F)
Opercle			Suffused with dark red (Bothe M and F)
Female	Similar to male but lighter in color, yellowish tan dorsally whitish with scattered melanophores on sides, belly white	Similar but lighter in color. Lacking black dorsal and anal fin margins and yellowish tan dorsally. Whitish with scattered melanophores on sides, , belly white	Overall light whitish orange. Lighter ventrally and on fins, which are partly hyaline	Sexes alike
Fins	Pectoral fin reaching beyond pelvic fin base; pelvic fin reaching beyond anal fin origin. Dorsal fin origin located halfway between snout-tip and hypural notch.	Pectoral fin reaching beyond base of pelvic fin; pelvic fin reaching beyond origin of anal fin; Dorsal fin origin located halfway between snout-tip and hypural notch.	Pectoral fin reaching base of pelvic fin; pelvic fin reaching origin of anal fin. Dorasl fin origin located halfway between snout-tip and hypural notch.	Pectoral fin reaching base of pelvic fin; pelvic fin reaching origin of anal fin. Dorasl fin origin located halfway between snout-tip and hypural notch.
Dorsal fin origin	1 scale width behind the pelvic fin origin	1 scale width behind the pelvic fin origin	3 scale width behind the pelvic fin origin	3 scale width behind the pelvic fin origin
Pelvic fin origin	Midway between pectoral fin base and anal fin origin	Closer to anal fin origin than to pectoral fin base.	Falling midway between pectoral fin base and anal fin origin	Closer to anal fin origin than to pectoral fin base
Dorsal margin of the operculum	More or less straight	Deep indentation
Dorsal profile of the head	Approximately straight behind the level of the eye in the male	Slightly concave	Slightly concave behind level of eye, arched thereafter	Approximately straight posterior to level of eye
Male Interorbital width	29-33 % HL	17-22 % HL
Male Internarial width	19-21 % HL	11-17 % HL
Female anal fin depth	23.5-24.8 % SL	17.4 – 22.7 % SL
Female interorbital width	25-33 % HL	16-21 % HL	33-36%HL	25-28 % HL
Female  Caudal-peduncle depth	12.4 – 13.4 % SL	10.4 – 12.3 % SL
Female  Caudal-peduncle length	18.6-21.2% SL	21.1-25 % SL
Body depth	31-32.8 % SL ( 31.1-32.8 in males and 31 – 31.7 in females)	26.9-33% SL (28.2-33 in males and 26.9-29.1 in females)	34.3-37.5%SL of males and 33-36.7in females	35.6 -40% SL in males and 33.3-36.8 % SL in females
Size	Male – 23.9-29.8mm Female – 22.1 – 25.5mm	Males 26.2 – 30.2 Female – 26.5 – 27.3mm	Up to 24.6 mm SL (males 21.5-24.6 and females 20.2- 20.7)	Up to 35.5mm SL (Males 25.3-35.5 and Females 23-30.8)
Scales on transverse line on the body	½ 8 ½	½ 8 ½	½ 6 ½ or ½ 7 ½  ( ½ 6[3] or 7 ½ [12] )	½ 8 ½
Scales on caudal peduncle	½ 4 ½	½ 4 ½	½ 3 ½	½ 4 ½
Predorsal scales	10[2],11[6],12[2]	11[4] or 12[6]	10[7],11[5],12[3]	11[5],12[6],13[4]
Prevental scales	15[2] or 16[8]	14[2], 15[7], 16[3]	13[7],14[4],15[2]	14[3],15[9],16[3]
Abdominal vertebrae	12[1] or 13[1]	12	11[4], 12[1], 13[1]	12
Caudal vertebrae	16[1] or 17[1]	16	16[2] or 17[4]	17
Total vertebrae	29	28	28-29	29
Scales on lateral series on body	21[2],22[1],23[1],24[5],25[1]	23[1],24[1],25[7],26[2],27[1]	20[1], 21[1], 22[7],23[0],24[6]	25[3],26[8],27[1],28[3]
Perforated scales arterially	4[3],5[2],6[5]	1[1],2[5],3[7]	1[11] or 2[4]	1[6],2[3],3[5]
Lateral processes to the kinethmoid			2	1
Female eye diameter			39 – 40% HL	29-34 % HL
Pharyngeal-teeth formula	5,4,3-3,4,5	5,4,3-3,4,5	5,4,3-3,4,5	5,4,2 -2,4,5
Dorsal fin rays	3 unbranched and 7 ½  bracnched	3 unbranched and 7 ½  bracnched	3 unbranched and 7 ½  bracnched	3 unbranched and 7 ½  bracnched
Anal fin rays	3 unbranched and 5 ½ [2] or 6 ½[8] branched	3 unbranched and 6 ½ branched	3 unbranched and 6 ½ branched	3 unbranched and 6 ½ branched
Caudal fin rays	17 branched rays 9 on upper and 8 on lower lobes	17 branched rays 9 on upper and 8 on lower lobes	17 branched rays 9 on upper and 8 on lower lobes	17 branched rays 9 on upper and 8 on lower lobes
Pectoral fin rays	1 unbranched and 11 ½ [4] or 12 ½ [6] branched	1 unbranched and 11 ½  branched	1 unbranched and 11 ½  branched	1 unbranched and 11 ½  branched
Pelvic fin rays	1 unbranched and 6 ½ [3] or 7 ½ [7] branched	1 unbranched and 6 ½  branched	1 unbranched and 6 ½  branched	1 unbranched and 6 ½  branched
Lateral line	Incomplete	Incomplete	Incomplete	Incomplete
Distribution	Restricted to Kalu basin. Small shaded streams and rivulets in and around Gilimale. Type locality – Ilukwaththa ferry of Kalu river at Gilimale	Restricted to the Athwelthota of Kalu basin	Shallow slow flowing densely shaded low land rain forest streams with sandy silt substrates of Kalu (Mahakalupahana, Yagirala), Benthara(Bambaravana), Gin (Kottawa-Kombala FR)Polathu-Modara (Kottawa-Kombala FR), Nilvala (Dediyagala FR) basins.	Suriyakanda in Walawe river basin. Shallow slow flowing shady streams with a sandy-silt substrates and dense leaf litter in submontane forests.

Literature Cited

Batuwita S., de Silva M. and Edrisinghe U., 2013.        A review of the danionine genera Rasboroides and Horadandia (Pisces: Cyprinidae), with description of a new species from Sri Lanka Ichthyol. Exploe. Freshwaters, Vol. 24, No. 2, 121-140 pp.

Chamikara S., 2012. පාට වර්ණ කොහි ගියාද හල්මල් දන්ඩියනේ? - සදාහරිත වෙළුම 1 කලාපය 9

Deraniyagala, P.E.P.1958. Three new cyprinoids, a new catfish and variation among some cyprinoids and an anabantoid of Ceylon. Spolia Zeylanica, 28: 129-138.

Meinken, H. 1957. Rabora nigromarginata n. spec. die "Rote rasbora". Die Aquarien - und Terrarien Zeitschrift, 10: 65-68.

Pethiyagoda, R. 1991. Freshwater fishes of Sri Lanka. Wildlife Heritage Trust, Colombo, xiii+362pp.