CRUSTACEAN ZOOPLANKTON OF DAMODAR RIVER

Studies on lotic zooplankton are in many ways less advanced than those on the standing waters. The relatively poor state of knowledge on lotic zooplankton is partly due to economic reasons. The aquaculture industry has been on the whole less interested in the zooplankton of rivers and streams than those of lakes and reservoirs and so fewer scientists have worked on the former. The special features of the lotic habitats are that the changes in environment are often more rapid and less predictable and are influenced by factors such as flood and desication which frequently playa major role. Further, studies of stream plankton need much more effort than those in lentic habitat. Many wetland biologists consider zooplankton to be transients of the river biota, washed from lakes, ponds and backwaters. However, sufficient examples are available in literature indicating that the zooplankton of a river form an integral part of the lotic community and contribute significantly to the biological productivity of this ecosystem (Hutchinson, 1967; Hynes, 1970).


INTRODUCTION
Studies on lotic zooplankton are in many ways less advanced than those on the standing waters. The relatively poor state of knowledge on lotic zooplankton is partly due to economic reasons. The aquaculture industry has been on the whole less interested in the zooplankton of rivers and streams than those of lakes and reservoirs and so fewer scientists have worked on the former. The special features of the lotic habitats are that the changes in environment are often more rapid and less predictable and are influenced by factors such as flood and desication which frequently playa major role. Further, studies of stream plankton need much more effort than those in lentic habitat. Many wetland biologists consider zooplankton to be transients of the river biota, washed from lakes, ponds and backwaters. However, sufficient examples are available in literature indicating that the zooplankton of a river form an integral part of the lotic community and contribute significantly to the biological productivity of this ecosystem (Hutchinson, 1967;Hynes, 1970).
Extensive surveys of river zooplankton have been made in temperate regions, however, in tropical part of world such as in India, it is scanty and scrapy. In view of filling up the gap in the knowledge on this potamofauna, to begin with, Damodar river was taken up for study. The present study on the potamozooplankton of river Damodar includes Cladocera, Conchostraca, Ostracoda and Copepoda.

MATERIAL AND METHODS
Zooplankton samples were collected using the method of Venkataraman (1992) from a total of eight stations, four sites viz. larindi, Telumuchu, lamadoba and Domgarh pumping station, Sindri from Bihar state and four sites viz. Dishergarh, Bumpur, DTPS Site and Rondia from West Bengal (Fig. I).
Description of the study area : I. Bihar State Station 1. Jarindi : Water is clear and slow moving, with less than one foot depth. Aquatic macrophytes and algal mats are seen growing where the water flow is very minimum. Human activities such as buffalow bathing and brick making are observed. Station 2. Telumuchu : Water is fast flowing and highly turbid with fly ash from a thermal power station nearby. The depth is two feet. Macrophytes such as Hydrilla sp. and Lemna sp. are present. Kathra and Dugdha coal washeries are present in this area. Station 3. Jamadoba : Water is fast flowing and turbid with fly ash. The substratum is rocky. Bhowara and lamadoba coke plants are present in this area.
Station 4. Domgarh pumping station, Sindri : Water is clean with sandy substratum. Aquatic macrophytes are seen growing but are clogged with grease and oil. Human activities such as buffalow bathing, brick making and fishing are observed. F.C.I. Sindri Plant, pathardih and Bhojudin coal washeries are present in this area.

II. West Bengal State
Station 5. Dishergarh : Main stream is fast flowing with clean water and sandy substratum. Activities such as buffalow and human bathing are noticed. Vallisneria sp. are seen growing on the banks where the w~ter flow is very less. Station 6. Burnpur : Substratum is sandy and the main stream is fast flowing with more than 1-2 m depth and eroding and depositing type. Macrophytes such as Hydrilla sp. and Vallisneria sp. are observed. Water is clean with algal mats on the shallow regions of the bank.
Staticn 7. DTPS site: Water is black in colour with fly ash and substratum is rocky and deep upto 3m. Industrial waste from Bengal paper mill and D.T.P.S. are discharged in to the river in this area.
Station 8. Rondia : Water is clean with sandy bottom and fast flowing. Macrophytes such as Hydrilla sp., Najas and Vallisneria sp. are observed on the banks of the river.
Female : Size 1.05 mm. Head large and rounded anteriorly. Eye small. Posteroventral comer broadly rounded with 5-9 marginal denticles followed by a series of fme setules. Claw serrated on the distal convex surface; concave surface with three long basal spines.
Distribution: India-Andaman and Nicobar Islands, Rajasthan, Tamil Nadu and Tripura states.
Elsewhere-common in tropical regions.
Remarks : Very common. Occurs in all types of habitat except in marshes. Distribution India-Bihar, Rajasthan, Meghalaya, Tamil Nadu and Tripura.
Remarks : Occur mostly among aquatic macrophytes.
Female: Body size 1.20 mm. Body elongated oval; head short; eye relatively small and situated near to the anteroventral comer. Antennules unsegmented, long and attached to the posteroventral part of the head. Antenna not extending beyond the posterior margin of valves. Ventral margin with a series of long setae followed by a series of spinules on the posteroventral corner. Postabdomen with 10 groups of lateral spines. Claw long with 3 basal spines.
Distribution India-Andaman and Nicobar Islands, Rajasthan, Tripura and Tamil Nadu.
Elsewhere-South East Asia, South Africa and South America.
Remarks Mostly occur among aquatic macrophytes. Female: Body size, 1.70 mm. Head large with antennule on the ventral side. Eye large, situated very near to anterior margin of the head; ocellus conspicuous; setae on antenna: 4-7/0-1-4. Ventral margin ornamented with rows of long hairs at the anterior side, medium hairs at the middle and three long setae at the posteroventral comer. Postabdomen broad with two spines at the base of the claws, anal denticles 10-12.

Latonopsis australis
Distribution India Rajasthan, Tripura and Tamil Nadu.
Remarks : Mostly occur among aquatic macrophytes. Sars, 1903Sars, 1903 Female: Body size 2.2 mm. Shape broadly oval or rhomboid. Dorsal margin moderately to strongly arched; posterior part of dorsal margin with distinct denticles. Head small with large eye and elongated ocellus. Postabdomen with 10 anal spines and a long, curved and denticulated claw.  Female: Body size 0.41 nun. Body rounded oval; dorsal margin serrated. Head rounded, ventral margin slightly concave with slightly pointed anteroventral corner. Antennules short, with a long seta near its base. Eye large, ocellus small and situated much nearer to the base of antennules than to the eye. Postabdomen broadly rounded. Claw short and serrated on the concave surface.
Remarks : Very common. Occurs in all types of habitats. (Brady, 1886)  Female: Size 0.56 mm. Body oval, dorsal margin with a slight cervical depression. Eye large, ocellus small and situated nearer to the apex of rostrum than to the eye. Antennules long with a long lateral seta. Antennae short with a longest seta having two or three longer spines in the middle. Postabdomen bilobed with rows of spines increasing in size proximally. Claw short and serrated without bastal spine. Female: Body size 0.76 mm. Body oval. Head small. Eye large, ocellus small, situated about halfway between eye and base of antennules. Antennules long with a group of sensory setae on distal end. Valves with a series of long feather-like setae on ventral side. Postabdomen with slight depression in the middle. Preanal margin with eight marginal denticles, postanal margin with 12 denticles up to anal groove and with five long and stout spines on the lateral surface. Material examined : Females from Domgarh pumping station, Sindri of Bihar, Dishergarh, Bumpur and Rondia of West Bengal.

Echinisca triserialis
Female: Body size 0.25mm. Shape spherical with a well marked postero-dorsal comer. Valves reticulated with hexagonal pattern and puntations inside the patterns. Posteroventral comer rounded without denticles. Rostrum curved posteriorly. Antennules about ~ the length of rostrum. Ocellus situated closer to the eye than to the apex of rostrum. Labral plate slightly depressed anteroventrally. Postabdomen with distinct preanal comer and indistinct postanal comer. Dorsal margin with 6-7 anal denticles. Claw setulated along the concave surface and with 2 basal spines.
Remarks : Mostly found among aquatic macrophytes. Female: Body size' 0.32 mm. Body elliptical in shape with a spine in the posteroventral comer. Carapace ornamented with striation. Labrum with 3-5 denticles. Postabdomen with 7-9 unequal spines and a long basal spine.
Remarks: Mostly found among aquatic macrophytes. Female: Body size 0.24 mm. Body oval, posterodorsal and posteroventral corners distinct. Valves with faint reticulation. Rostrum slightly curved posteriorly. Ocellus smaller than eye, situated closer to eye, than to apex of rostrum. Postabdomen with 10-12 short denticles. Claw with two basal spines.

ChydoTUS pubescens
Distribution : Elsewhere : South East Aisa, Africa and South America.
Remarks: This species is a synonym of C. pubescens Sars, 1901 however;Michael and Hann (1979)  Female: Body size 0.79 mm. Body spherical, posteroventral comer rounded, without denticles. Valves with polygon marking. Rostrum pointed. Antennules not reaching the apex of rostrum.
Ocellus smaller than eye and situated nearer to eye than to the apex of rostrum. Postabdomen with 20 anal spines decreasing in size proximally. Claw with two basal spines.
Remarks Guerney( 1907) recorded this species from Calcutta and after that it is not found again either by Sharma (1978). Fenlale Body size 0.52 mm. Shape oval, without spines on the posteroventral corners and reticulations on the carapace. Antennules not reaching apex of rostum, Labrum with pointed apex. Postabdomen with straight dorsal margin and 7-9 anal denticles present. Claw with a medium sized basal zpine. Female : Body size 0.31 mm. Shape rectangular, maximum height slightly before middle. Posterodorsal comer with a slight angle, posteroventral corner rounded without denticle. Valves with striations forming a rectangular pattern. Antennules not reaching the apex of rostrum. Postabdomen with 7-8 groups of anal denticles and claw long basal spine.  Elsewhere : Cosmopolitan.

Dunhevedia crassa
Remarks: Very common. Occurs in all marshy habitats of West Bengal. Fernando (1974) and Michael and Sharma (1988)

Material examined: Female from Dishergarh and DTPS site of West Bengal State.
Female: Body size 0.28 mm. Body elongated oval. Posteroventral and posterodorsal comers rounded. Antennules not reaching apex of rostrum. Ocellus small, situated slightly closer to eye than to apex of rostrum. Postabdomen with 5-6 denticles. Claw with a short basal spine.
Distribution : India : Gujarat, Tamil Nadu, Rajasthan and Tripura. Elsewhere South East Asia, Ethiopian and Neotropical regions.
Female: Body size 0.36 mm. Valves with striations. Rostrum short and blunt, antennules not reaching the apex. Ocellus smaller than the eye, situated closer to the eye than to the apex of rostrum. Labrum serrated on anteroventral margin. Postabdomen long with 12 to 13 anal denticles, claw long with short basal spine.
Distribution : India : Andaman and Nicobar Islands, Rajasthan and Tamil Nadu. Elsewhere : South East Asia, Neotropical and Nearctic regions.

Leydigia acanthocercoides
Female: Body size 0.89 mm. Valves with longtitudinal lines. Rostrum blunt, antennules not reaching apex of rostrum. Ocellus smaller than eye, situaed closer to the eye than to the apex of rostrum. Labrum rounded with fine setae. Postabdomen with about 18 groups of small denticles, each group consists of 3 or 4 denticles with the distal-most denticle being the longest of each group. Claw with a short basal spine. Female: Shell thin, transparent and nearly rounded. Umbone close to the anterior extremity. Shell with 6-7 growth lines. The ocellus large equal to the size of as eyes. The antennules or the first antennae unsegmented, clubshaped with sensory hairs at their tips. The second antennae biramous with each flagellum 7 -jointed and each joint bearing setae. The telson large, armed with 7 -8 pairs of strong hooks, the first pair long and serrated on the edge; the second pair near the root anned with about 10 rather stout spines.

Distribution: Common. Occur throughout Indian subcontinent.
Remarks : This is the first record of its occurrence in West Bengal. (Victor and Fernando, 1979) 1979. Stenocypris distincta (Victor and Fernando, 1979)  Female: Length-3.20 mm. Valves elliptical; valves elongate; anterior and posterior margins rounded; left valve slightly larger than the right; radial band of septa prominent, wider anteriorly and narrow posteriorly; valve margins hairy except dorsally; valve surface with puncta and hairs; ventral margin slightly concave in the middle, dorsum with a low arch sloping posteriorly. Natatory setae of the second antenna well developed, not reaching the tips of the tenninal claws and smooth; sensory club three segmented, claws toothed. Second thoracic leg with a long tenninal scythelike claw, second segment with a single seta, hairy; dorsal surface and margin having groups of spines and ventral margin hairy. Furcal rami asymmetrical, tenninal and subtenninal claws of both rami toothed, dorsal setae absent; right ramus curved broader with dorsal margin heavily toothed, terminal seta more than 'l2 the length of the tenninal claw; left ramus straight, dorsal margin with groups of teeth covering 'l4 the length of the ramus, tenninal seta more than two-thirds the length of the tenninal claw.

Distribution: Madurai, India.
Remarks: This is the first record of its occurrence in Bihar and West Bengal.

Material examined Females from Telemuchu of Bihar State.
Female: Valves with irregular, continuous pore canals along the margins; surface with minute hairs. Asymmetrical furca, bent at the proximal end; right ramus with groups of stronger spines for 2/3 the the length of the ramus, on the dorsal margin; left ramus is also armed with spines but they are relatively weak. Length 2.08 mm and height 0.91 mm.
Remarks: This is the first record of its occurrence in West Bengal. Female: Body size 1.45 mm. Metasomal wings asymmetrical; urosome 3-segmented. P5: Coxal process is short and conical claw bears fine hairs along the inner margin; exopodite 3 not distinct and bears 2 unequally long setae; endopod long, cylindrical, tip sloping inwards with 2 spinules and few hairs.
Distribution : Occur throughout Indian sub continent.
Remarks: This is the first record of its occurrence in West Bengal. Gurney, 1906Gurney, 1906 Female: Body size 0.9 mm. A 1 reaching slightly beyond the metasome and consisting of 17 segments; last 2 segments together longer than the previous three; last segment with a smooth hyaline membrane without any notches. Inner spine of P 5 apical or subapical in position on the second segment. Inner terminal spine of P 4 endopod distinctly longer than outer terminal spine and shorter than the terminal segment. Inner margin of the caudal ramus bare. (Daday, 1906) 1906. Mesocyclops aspericornis Daday, Math. Termeszl erte3., 24 : 34-77. 1907. Cyclops leuckarti, Rec. Indian Mus., 1 : 21-33. Material examined: Females from Domgarh pumping Station, Sindri of Bihar State and OTPS site of West Bengal State.

Mesocylops aspericornis
Female: Body size 0.9 to 1.3mm. A 1 reaching slightly beyond the metasome and 17-segmented; last 2 segments together longer than the previous three hyaline plate of the last segment with several indistinct notches or serration), some times with one deep notch as in male. Inner spine of P 5 at middle of second segment and shorter than the terminal seta. Inner margin of caudal ramus bare. A specific diagnostic character of leuckarti is the conspicuously ribbed outer margin of the basis of the maxilla.

DISCUSSION
Twenty eight species of Cladocera, one species of Conchostraca, two species of Ostracoda and four species of Copepoda were collected from eight different sampling stations in Oamodar river (Table 1). Among Cladocera M spinosa and D. crassa and a cyclopoid copepod M. hylinus were found to occur in as many as six collection sites. The species such as Diaphanosoma sarsi, Pseudosida bidentata, Scapholeberis kingi, Bosmina longirostris, Bosminopsis deitersi, Chysorus pubescens, C. eurynotus, Pseudochydoras globosus, A/ona guttata, A. davidi, Notalona g/obu/osa, Leydigia acanthocercoides, Stenocypris distincta, and Paracentrocypris canaliculata are available in only one collection spot ( Table 1).
The eight sampling stations have been compared by means of the Sorensen index of similarity for Cladocera. This was calculated for each combination of stations according to the following equation (Sorensen, 1948) : S =2C/a+bx 1 00, where 'C' is the number of species common to both associations, 'a' the number of species in one association and 'b' the number of species in the other association. The resultant Sorensen indices for 28 pairs of stations are given in Table 2. The indices are generally high, reflecting the smaller number of similar species involved and their wide distribution, but the two groups of stations are easily discernible. Jamadoba, Oamgarh, Burnpur and Rondia have high-interrelated indices. Telemuchu has less indices showing the amount of pollution Load.
Index of biotal dispersity (lBO) of Koch (1957) was used to assess how widely dispersed the cladoceran species are between a number of stations. IBO = T -SIS (n-l)X 1 00 where 'T' is the arithmetica sum of species living in each of 'n' compared associations, and'S' is the total list of species in 'n' compared associations. If each station had a completely different set of species Cladocera, 'S' would equal 'T' and the IBO would be zero. If each station had an identical set of species 'T' would equal n X S and the IBO would be 100.
When the Koch index for all eight stations is calculated the resulting IBO is 17.4, but if separate indices are calculated for the four stations (Jamadoba, Oomgarh, Burnpur and Rondia) there is an increase in the IBD (24) and 14 for rest of the stations. The large increase in IBD when the less polluted stations in West Bengal region (stations 5-8) are considered separately, indicates that these stations resemble each other in their fauna of planktonic Cladocera much more closely than they resemble the polluted stations in Bihar State (Stations 1-4). This is in good agreement with the Sorensen indices. The IBD for Cladocera of Bihar part of Damodar is 15 and the IBD for West Bengal part is 20. The validity of describing members of the zooplankton especially Cladocera as an indicator organism has been questioned by a number of authors because of the lack of basic knowledge of the ecological characteristics and requirements of individual species as well as communities (Bartsch and Ingram, 1966). Sladeck (1973) has extensively reviewed the subject and listed the saprobic indication of over five hundred species of rotifers. Nevertheless, many rotifer species are considered to be indicators of the trophic nature of their habitat (Pejler, 1957; , 1966;Hodgkinson, 1970). The dominance of certain eurytopic Cladocera found in the present study in the polluted regions of the Damodar river such as C. cornuta, M micrura, M spinosa and C. barroisi can be used as an indicator of pollution as found in other studies (Campbell, 1939;Gaufin and Tarzwell, 1952;Hynes, 1959).

SUMMARY
In tropical part of world including India, extensive survey of river zooplankton is scanty and scrapy than the temperate. In view of filling up the gap in the knowledge on this potamofauna, to begin with, Damodar river was taken up for study. A total of eight stations, four in Bihar and four in West Bengal of Damodar river were studied for their crustacean zooplankton. Among the zooplankton collected such as Cladocera, Conchostraca, Ostracoda and Copepoda, Cladocera dominated with 28 species, 18 genera and six families. Ceriodaphnia cornuta, Moina micrara, Macrothrix spinosa and Chydorus barroisi were found to occur in most polluted regions of the river. Jamadoba, Domgarh, Bumpur and Rondia have high interrelated Sorensen indices with high IBD (24) when compared to other polluted stations (14).