Friday, November 21, 2014

Possible range extension of Rasboroides nigromaginatus(?)


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.

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