ON SOME RARE AND INTERESTING CLADOCERANS ( CRUSTACEA : BRANCHIOPODA ) FROM MEGHALAYA

The systematic studies on Freshwater Cladocera of India were initiated by Baird (1860). Since then these micro-crustaceans have been recorded from various localities in different states of the country (Sharma and Michael, 1987; Michael and Sharma, 1988; Sharma, 1991). Investigations on Cladoceran fauna of Meghalaya began in the last quarter of twentieth century and the related contributions are those of Patil (1976), Biswas (1980), Michael and Sharma (1988) and Sharma and Sharma (1999).


INTRODUCTION
The systematic studies on Freshwater Cladocera of India were initiated by Baird (1860).Since then these micro-crustaceans have been recorded from various localities in different states of the country (Sharma and Michael, 1987;Michael and Sharma, 1988;Sharma, 1991).Investigations on Cladoceran fauna of Meghalaya began in the last quarter of twentieth century and the related contributions are those of Patil (1976), Biswas (1980), Michael and Sharma (1988) and Sharma and Sharma (1999).
While working on zooplankton samples collected from the state of Megha1aya, the author came across seven interesting species of Cladocera including two new records from India, four new records from North-Eastern region and one new record from Meghalaya.The present report provides descriptions and illustrations of the recorded cladocerans and remarks are made on their distribution.

METE RIALS AND METHODS
The present observations are based on plankton samples collected during [2003][2004][2005], and also those collected earlier (during 1988-1990) for the "State Fauna of Meghalaya : Zooplankton Survey", from localities in different districts of Meghalaya state.The examined material include samples deposited in Freshwater Biology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong and those in the holdings of the Eastern Regional Station, Zoological Survey of India, Shillong.
Elsewhere : Tropical and subtropical parts of Australasia and in Africa (Sudan).
Postabdomen elongated and with small irregular anal teeth.Claw with two basal spines, the proximal spine smallest.

Differential diagnosis:
This species can be differentiated from the closely related A. excisa in having more elongated body; valves with polygons and longitudinal striations; posterior margin of valves almost straight and at right angle with the ventral margin.
Elsewhere: Australian, Ethiopian and Neotropical regions, and Java Characters : Body oblong, maximum height in the middle; dorsal margin of body convex, ventral margin nearly straight and with setae decreasing in size.Postero-ventral corner of values with variable number of teeth.Head shield and valves with tetragonal, pentagonal or hexagonal cells.Rostrum broad and its ventral margin almost at level of ventral margin of valves.Labral plate with rounded apex.Ocellus situated nearer to eye than to apex of rostrum.Postabdomen tapering distally and with distinct preanal corner.Anal margin with row of anal spines increasing in size distally and groups of lateral setae.Claw with small basal spine and seta on concave margin.Distribution: N. E. India-new record.India-Kashmir, Uttaranchal and Andhra Pradesh.

REMARKS
Seven species of Cladocera belonging to two families and five genera are recorded from Meghalaya.Camptocercus uncinatus and Alona guttata tuberculata are new records from India; the former even represents a new record from the Oriental region.Four species namely Diaphanosoma volzi, Alonella clathratula, Alona macronyx and Graptoleberis testudinaria are new to Northeastern India while Alona monacantha tridentata is a new record from Meghalaya.
All the stated taxa, except C. uncinatus, are rare elements in this study.The present report raises the known species richness of Cladocera from Meghalaya to 58 species which, in turn, nearly equals the highest Indian report of 59 species from the state of Jammu and Kashmir (Prof.B. K. Sharma, personal communication).Smirnov (1971) described Calnptocercus uncinatus from Lake Nikolaevskoe (Russia) and it has since been reported from Romania, S.W. Siberia, Israel, Iraq, Ethiopia, Egypt and Guatemala.Smirnov (1998) again provided a detailed description of this species to resolve taxonomic anomalies, anticipated its wider occurrence and remarked on need for re-examination of the reports supposed to be that of C. australis in particular.The present record is apparently the first confirmed record of C. uncinatus from the Indian subcontinent as well as the Oriental region.C. latikae described by Rane (1985) from Madhya Pradesh and subsequently treated as C. rectirostris s. lato by Sharma and Sharma (1999) are presently confirmed as cases of mistaken identity of C. uncinatus and is, therefore, proposed as its synonyms.This chydorid is relatively widely distributed in the examined samples and has been observed from several localities in East Khasi Hills, West Khasi Hills, Rhi Bhoi, South and West Garo Hills districts of Meghalaya state.
Alona guttata tuberculata is yet another new record from India.This chydorid, treated as a subspecies of A. guttata by Smirnov (1971), is distinctly characterized by rounded pits or tubercles on its head shield and valves.It is a rare element in the examined material and has been observed only in one locality each in West Khasi Hills and South Garo Hills districts.It is recorded so far only from Europe, Columbia and USSR as against the nominate Alona guttata guttata which apparently shows cosmopolitan distribution.
Diaphanosolna volzi was originally described from Thailand as D. sarsi var.volzi and was subsequently reported from Indonesia.No further records were published for a long time, until substantiation of its specific status and its conspecificity with D. aspinosum described by Chiang (1956) from China.On the other hand, it was treated as a distinct species by Korovchinsky (1981).Korovchinsky (1995), however, re-described D. volzi in view of its confusion with D. sarsi Richard and D. celebensis Stingelin based on populations from Thailand, Southern India, Philippines, Indonesia, Malaysia, Australia and Sudan.In spite of its increasing distributional reports, it is still considered as a rare species (Korovchinsky, 1995).It is known to inhabit shallow vegetated habitats and often co-occurs with D. sarsi.The remarks relating to rare nature are also true as only four parthenogenetic females of D. volzi are examined presently from a shallow wetland in East Garo Hills district which, in turn, incidentally also occurred with D. sarsi.Further, this second report of -D.volzi from India significantly extends its distributional range to Northeastern region.
Alonella clathratula was described (Sars, 1896) from its type locality in neighborhood of Sydney.It was considered as a subspecies of A. excisa by Smirnov (1971) while he later (Smirnov, 1996) resurrected its specific status.A. clathratula clearly differs from the closely related A. excisa in distinct morphological attributes as well as in distributional ranges.The former species occurs in Australia, the Ethiopian and Neotropical regions and, Java while the later is a cosmopolitan species.
A. clathratula is so far reported from India only from Bihar (Sharma and Sharma, 2001) and the present report, therefore, extends its distributional range to N. E. region.Smirnov and Timms (1983) reported its occurrence in acidic waters in Australia.This species is also presently collected from an acidic wetland (pH: 6.0) from South Garo Hills district of Meghalaya.Petkovski (1966) described the monotypic genus Indialona including I. ganapati from Baroda (Gujarat).Smirnov (1971), however, included Alona lnacronyx Daday and A. globulosa Daday.A recent redescription of Indialona, however, transfers the remaining two species to Alona.Among these, A. Inacronyx is so far recorded in India from Madhya Pradesh only; it was described as a new species Indialona jabalpurensis by Rane (1983) which was treated as a synonym of A. macronyx by Sharma and Sharma (1990).The material examined presently from only one locality of Rhi Bhoi district of Meghalaya, therefore, extends its occurrence to Northeastern India.
The cosmopolitan Graptoleberis testudinaria is examined from a shallow wetland in Rhi Bhoi district and located near Meghalaya-Assam border.This species shows disjunct occurrence in India, with earlier records from Kashmir, Uttaranchal and Andhra Pradesh.The present study extends its distributional range t~ Northeastern region.Alona monacantha tridentata, a new record from Meghalaya, has been reported from this region from Tripura (Venkataraman and Das, 2000).The stated species apparently identified as A. monacantha in fact actually refers to A. monacantha tridentata as per the details given by Michael and Sharma (1988).

SUMMARY
The coIlections examined from Meghalaya reveal seven species of rare and interesting Cladocera belonging to two families under five genera.Among these, Camptocercus uncinatus and Alona guttata tuberculata are new records from India; the former in fact represents a new record from the Oriental region.Four other species namely Diaphanosoma volzi, Alonella cia th ratu la, Alona macronyx and Graptoleberis testudinaria are new records to N. E. India while Alona monacantha tridentata is the sole new record from Meghalaya.This report raises the species richness of Cladocera known from Meghalaya to 58 species.All the recorded taxa, except C uncinatus, exhibit rare occurrence in the examined coIlections.