A NEW FISH SPECIES OF THE GENUS BRA VANIA (HOMALOPTERIDAE : HOMALOPTERINAE) FROM RIVER NOADHING DRAINAGE, ARUNACHAL PRADESH, INDIA

Bhavania australis is the only species of genus Bhavania so far recorded from the southern states of India (Tal war and Jhingran, 1991). This fish species has a good number of synonymies, Platycara australis (Jerdon, 1849), Homaloptera maculata (Day, 1877), Homaloptera brucei (Day, 1877), Bhavania annandalei, Hora ( 1920). Subsequently, Hora (1920) revised the genus Bhavania (Subfamily : Homalopterinae) on retrieval of the species Bhavania australis from the state of Kerela, Karnataka and other southern states of India. Even thereafter several Authors (Hora, 1941; Jayaram, 1981; Menon, 1987; Talwar & Jhingran, 1991) on redescription of the species Bhavania australis rather kept in the same genus Bhavania. Recently, on reassessment of the faunal wealth of Arunachal Pradesh, India, led to the record of one more species of Bhavania from the River Noadhing drainages, Lohit district. The new species has its own special characteristic features which could be readily differentiated from the species Bhavania australis on various scores: head dotted with pores and arranged in rows along the margin of orbit; thoracic region with a central pit; lateral line at the origin of ventral fin slightly curved; pectoral fin overlapping the ventral fin anteriorly; caudal emarginate, lower lobe longer than upper; longitudinal band from the base to the tip of lower caudal lobe, eight number of saddle-shaped blotches on the back. On the basis of these distinctive characters, the species has been described as a new species Bhavania arunachalensis along with a key to the identification of all the species of genus Bhavania in the text.


INTRODUCTION
Bhavania australis is the only species of genus Bhavania so far recorded from the southern states of India (Tal war and Jhingran, 1991).This fish species has a good number of synonymies, Platycara australis (Jerdon, 1849), Homaloptera maculata (Day, 1877), Homaloptera brucei (Day, 1877), Bhavania annandalei, Hora ( 1920).Subsequently, Hora (1920) revised the genus Bhavania (Subfamily : Homalopterinae) on retrieval of the species Bhavania australis from the state of Kerela, Karnataka and other southern states of India.Even thereafter several Authors (Hora, 1941;Jayaram, 1981;Menon, 1987;Talwar & Jhingran, 1991) on redescription of the species Bhavania australis rather kept in the same genus Bhavania.Recently, on reassessment of the faunal wealth of Arunachal Pradesh, India, led to the record of one more species of Bhavania from the River Noadhing drainages, Lohit district.The new species has its own special characteristic features which could be readily differentiated from the species Bhavania australis on various scores: head dotted with pores and arranged in rows along the margin of orbit; thoracic region with a central pit; lateral line at the origin of ventral fin slightly curved; pectoral fin overlapping the ventral fin anteriorly; caudal emarginate, lower lobe longer than upper; longitudinal band from the base to the tip of lower caudal lobe, eight number of saddle-shaped blotches on the back.On the basis of these distinctive characters, the species has been described as a new species Bhavania arunachalensis along with a key to the identification of all the species of genus Bhavania in the text.
1 Zoological Survey of India, Arunachal Pradesh Field Station, Itanagarr791 113, Arunachal Pradesh 2Present address: P. T. Bhutia,Zoological Survey of India,Northern Regional Station,, Uttarakhand :'Zoology Department, Gauhati University, Guwahati-781 014, Assam .tZoologyDepartment, Rajiv Gandhi University, Rono Hills, Itangar-791 112, Arunachal Pradesh Besides, another interesting features been described in the text is regarding the fish zoogeography confirming that the new fish belongs to genus Bhavania, a south Indian element.And its presence in the fish composition of Arunachal Himalaya appears to he of a rare phenomenon, which supports the 'Indobrahm hypothesis' postulated by Pasco (1919) and Pilgrim (1919)

MATERIALS AND METHODS
Morphometric measurements and counts were made with dial calipers and recorded to the tenth of a millimeter following the method of Jayaram (1991).The measurement of head length and body parts has been presented as proportion of standard length (SL).The subunits of head are presented as -proportion of head length (HL).Counts and measurements were made on the left side of the specimen whenever possible.The system of classification of fish followed is after Nelson (1995).Fin formula: Barbels vi, Dorsal ii. 7, Pectoral viii.11, Ventral iii.8, A.i.6 Body broad and fla~ anteriorly, tapering towards the tail, its depth 9.0-10.2 in S1.Head broad, flat, moderate in size, its length 4.3-4.8 in SL, its maximum width 1.1-1.3times and inter-nostril distance 3.0-3.4time both in HL; gill openings above base of pectoral fins.Eyes fairly small; its diarneter 36.0-43.0 in SL, 8.3-10.0 in HL, inter-orbital distance 2.0-2.6 times in HL.Snout smooth obtusely rounded.Mouth small, ventral, horseshoe shaped, sub equal.Lips thin, upper lip with tubcn:les longer than lower lip.Barbels six, two pairs rostral, one pair maxillary, all of equal length.Paired fins inserted horizontally, winged shaped and with adhesive apparatus.Pectoral fins overlapping the ventral fin at its origin.Dorsal fin smaller than paired fins, inserted almost opposite to ventral and nearer to snout tip than caudal fin base.Lateral line complete slightly curved at the hase of ventral fin.Caudal fin emarginate, lower lobe longer than upper lobe; caudal peduncle 2.8-3.8tilnes longer than deep.Body scales small, cycloid covering the entire body, scale less at head and abdomen; lateral scale 70-75.Body color grayish with yellowish tinge above lateral line with eight saddle-shaped blotches on the back, longitudinal black band from the caudal base to the tip of lower caudal lobe, fins yellowish.Morphometric data as in Table 1.
From the comparative statement (Table 2) also could be stated that the specific characteristic features in respect of Bhavania arunachalensis strongly supports for the establishment as a new species.The comparative chart also revealed that the species Bhavania arunachalensis sp.nov.having closer affinity with Bhavania australis rather than Balitora brucei, commonly available in the hill streams of the North Eastern Regions of India PLATE-II, 6 and to some extent having close affinity with Balitora burmanica.
Interestingly, Bhavania arunachalensis is a south Indian form and its presence in the fish composition of Arunachal Himalaya however; justify the Indobrahm Hypothesis postulated by Pasco (1919) and Pilgrim (1919).According to them it infers that the Arunachal Himalaya was a part of peninsular shield separated by a broad strip of the Ganges-Brahmaputra alluvium (Krishnan, 1953;Sen & Dey, 1984;Nath & Dey, 2000).

DISTRIBUTION
The fish samples were collected from the river Noadhing drainages near Namsai Lohit district.