Freshwater Cladoceran (Cladocera: Branchiopoda) Diversity of Lateritic Rarh Belt of West Bengal, India: A Review

Zooplankton are microscopic, non-motile, aquatic animals having multifaceted functionalities in aquatic system including trophic dynamics, pollution surveillance, amelioration etc. Systematic enumeration of plankton is of great biological relevance. Geographically, south-western part of West Bengal, including the districts of Murshidabad, Birbhum, Bankura, Puruliya, Purba Bardhaman and Paschim Bardhaman, Purba Medinipur and Paschim Medinipur, is characterised by a red, lateritic soil form and is frequently referred to as the “Rarh belt” or “Rarh Bengal”. Due to this unique edaphic factor the biodiversity herein is of special significance. Despite this fact, study on the diversity, abundance and distribution of zooplankton, emphasizing “Cladocera” as a group, in the water bodies of this area, is much unorganized, fragmentary and meagre till date. This review is an attempt to highlight the relevance of Cladocera as an important zooplankton group and provide a systematic catalogue of the Cladocera species recorded in this area till date. As many as 63 species of Cladocera, belonging to 6 families and 24 genera have been recorded from this lateritic red soil Rarh belt. However, it is suspected, the actual species richness of Cladocera in recent times may vary from the number recorded. Thus, there is a need of updation, revalidation and exploration of Cladoceran taxa in this region using modern techniques and current literature.


Introduction
Zooplankton are microscopic, floating, aquatic organisms that exhibit active swimming movements, can maintain vertical position in water but are unable to navigate and move against appreciable current (Odum 1996). They are one of the most significant biotic components of an aquatic ecosystem affecting most of the functional aspects including food chains, food webs, energy flow and cycling of matter (Murugan et al. 1998). Zooplankton are not only useful as bio indicators, helping in surveillance of environmental quality, but also in ameliorating polluted waters (Dadhick et al. 1999). Comparing number, diversity, size, structure, fecundity, and reproductive strategies of zooplankton in various water bodies help enumerate the nature and extent of pollutant in them (Sarma 1996;Mukhopadhyay et al. 2000). Systematic enumeration of plankton is also of great biological relevance to understand the community dynamics of aquatic ecosystem. Spatial and temporal heterogeneity of zooplankton is a common feature in different aquatic ecosystems and is the result of different interacting physical and biological processes. A number of mutually interacting factors such as change of climatic conditions, physical, chemical parameters affect distribution and diversity of zooplankton communities (Neves et al. 2003). Freshwater zooplankton mainly consists of four major groups, i.e. Protozoa, Rotifera, Cladocera, and Copepoda (Forró et al. 2008).
Geographically, south-western part of West Bengal, comprising the districts of Murshidabad, Birbhum, Bankura, Puruliya, Purba Bardhaman and Paschim Bardhaman, Purba Medinipur and Paschim Medinipur, is characterised by a red lateritic soil form and thus called the Rarh belt or Rarh Bengal (Bagchi and Mukherjee 1983). Due to this unique edaphic feature, the wetlands herein have some inherent distinctive features which make them unique, in terms of physical, chemical parameters and bio-diversity components. Despite this fact, study on the diversity, abundance and distribution of zooplankton, emphasizing Cladocera as a group, in the lentic water bodies of this area, is much unorganized, fragmentary and meagre till date.
Such a dearth of systematic information on this natural, nutritive fish feed micro-crustacean fauna is a big obstacle in popularizing their role in fish productivity and wetland conservation in this region. Thus, the aims of this review are: i). to reveal the role of Cladoceran zooplankton, in fresh-water ecosystems, fish productivity and other biological purposes, ii). to enlist the recorded diversity of Cladocerans in southern-western Rarh belt of West Bengal, and iii). to give recommendations on proper exploration, management and exploitation of this specific group of plankton in future.
This information will summarize the updated information regarding Cladoceran biology in the region for future study. Bagchi and Mukherjee (1983), first, geographically recognised the north-southern lateritic belt of West Bengal as Rarh Bengal. In West Bengal, the distribution of laterites and lateritic soils is limited to parts of western fringe, extending in the west-central part of Birbhum, eastern part of Bankura, middle Barddhaman, part of Murshidabad, Paschim Medinipur and eastern parts of Purulia districts, altogether covering an area of approximately 7,700 km 2 and lie within the latitudes 22°00' N to 24°30' N and longitudes 86°45' E to 87°50' E (Ghosh and Guchhait 2015) (Figure 1). The reddish-brown soil or laterite found here is created as a result of intense weathering of rocks and is made up of mineral assemblages that include iron or aluminum oxides, oxy-hydroxides or hydroxides, kaolinite and quartz. The soil is typically infertile, gravelly and coarse textured, with low humus level and well-drained with low water holding capacity (Ghosh and Guchhait 2015). These typical geomorphic features of the Rarh belt make it an interesting area of study even in context of biological features.

Wetland Profile of Rarh Belt of West Bengal
Owing to differences in geographical, physical and topographical features, different districts of South Bengal are characterized by a variety of wetlands, both lotic and lentic. In the south-western part, Brahmani, Dwarka, Mayurakshi, Kopai, Ajay, Damodar, Dwarkeswar, Silai, Kansai and Subarnarekha dissect the lateritic Rarh region into patches of forests and habitable areas (Ghosh and Guchhait 2015). In addition, diverse forms of lentic water bodies in the form of dams, bandh, jheel, doba, pukur, dighi, beel, and baor are also spread throughout the area. District wise impounded fresh water habitats of Rarh belt of West Bengal (Handbook of fisheries statistics, W.B.,  are depicted in the Table 1. Among different districts, Burdwan (including both newly formed Purba Bardhaman and Paschim Bardhaman) has the highest impounded fresh water area, followed by Murshidabad. Puruliya has the least amount of freshwater impounded wetlands.

Cladocera -A Unique Zooplankton Group
The term Cladocera was coined by Latreille (1829) and is derived from two Greek words, 'klados' meaning branch and 'keras' meaning horn, thus, referring to the two branched second antennae which are the chief locomotory structure of these animals. Most of the Cladocerans move through water with a series of hops and jumps and hence called water fleas (Smirnov 1971).
Cladocera is a super-order belonging to the class Branchiopoda of super class Crustacea and are subdivided into four orders-Anomopoda, Ctenopoda, Onychopoda, and Haplopoda (Fryer 1987). Smirnov (1971)  Cladocerans (Crustacea: Branchiopoda), are primarily a monophyletic freshwater zooplankton and form the most useful and nutritive group of crustaceans. (Dumont and Negrea 2002) They are an ancient group of Palaeozoic origin (Forró et al. 2008) and consists mainly micro zooplankton (Dodson and Frey 1991) of size range of 0.2-6 mm, and up to 18 mm in a single case of Leptodora kindtii (Focke 1844). These branchiopod crustaceans, inhabit pelagic, littoral, and benthic zones of all lotic and lentic aquatic habitats, viz., lakes, reservoirs, ponds, puddles, swamps, paddy fields, streams and rivers. They are known to be the inhabitants of both the permanent and temporary water bodies (Forró et al. 2008). They are known to be more abundant in temporary water bodies than in permanent freshwater habitats (Hutchinson 1967). Nevertheless, some species can tolerate considerable salinities (eg., some species of the family Ctenopoda, Anomopoda and Onychopoda) (Potts and Durning 1980;Negrea 1983). Cyclical parthenogenesis is the predominant form of reproduction, while, asexual reproduction is occasionally supplemented by sexual reproduction allowing the species to survive tough ambient conditions and allowing far and wide dispersal (Hebert 1997). Most species are filter-feeders and herbivorous while Onychopods and Haplopods are predatory (Fryer 1968). Cladocera have always been considered as an important food item of plankton feeding fishes (Scourfield and Harding 1941). Murugan (1989) has reported presence of high levels of protein, free amino acids, fats and carbohydrates in Cladocerans like Daphnia carinata, D. longispina, D. magna and D. pulex, making them highly nutritious and valuable live feed.
2 Trophic dynamics As live feed Cladocerans make organic material available to higher trophic levels, in a larger pellet, thus, saving the foraging energy of their predators (Alikunhi et al. 1955). 3 Larviculture and ornamental fish culture feed Indulkar and Belsare (2003) mentioned that live Moina sp. is superior to other foods for post-larval stage of Macrobrachium rosenbergii. Pandey and Yeragi (2000) have also pointed out the importance of Cladocerans like Moina and Daphnia as live-food organisms in freshwater larviculture and ornamental fish culture.

Bio indicator
Cladocerans have also been identified as best indicator organisms for assessment of water pollution levels particularly nutrient enriched eutrophication, resulting from pollution by untreated domestic sewage and toxicity associated with pesticides (Makrushim, 1976;Gannon and Stemberger, 1978). Cladocera species are especially responsive to changes in pH, reflecting their sensitivity to acidification and can even react to very low concentration of contaminants (Zawisza et al. 2016).

Test model
Cladocerans have been used as experimental animals by several biologists in various studies pertaining to aquatic toxicology (Gannon and Stemberger 1978;and Shiny et al. 2005). Yogendra et al. (2005) suggested that Daphnia can serve as an ideal test model for bio-monitoring of industrial effluents.

6
Population control of mosquito Cladocerans are also been found to be an efficient agent for mosquito control. They help in reducing larval mosquito population through suppressing both mosquito oviposition and larval development (Chase et al. 2003).

7
Population control of micro-organisms As Cladocerans feed on smaller zooplankton, bacterio-plankton and other phyto plankton (Murugan et al. 1998) they also regulate the population growth of bacteria, heterotrophic protozoans, microalgae, and even some rotifer species through trophic relationships and competition (Arnold 1971).

Relevance of Cladocera as a Group in Aquatic Biology
Cladocera are a multifaceted group of zooplankton and play substantial role in trophic dynamics, productivity, energy flow, bio monitoring etc. (Forró et al. 2008). Different authors have reported significance of Cladocerans in ecosystem which is listed in Table 2.

Status of Cladoceran Diversity in India
The currently accepted species richness of Cladocera based on existing descriptions is around 620, however, it is projected that the actual number of species may be 2-4 times higher (Forró et al. 2008). The highest numbers of valid species are reported from Australia, Europe, North America, South America, and the smallest number from Africa and Southern Asia (Korovchinsky 1996). The systematic study on Indian freshwater Cladocera was first initiated by Baird (1860) who published a paper on the Cladocera (Crustacea: Branchiopoda) from India, describing Daphnia newporti (Baird 1860) (Anomopoda: Daphniidae). In a subsequent study, Fernando (1980 a, b) identified the presence of 61 species of Cladocera from India, however, could not find the presence of large Cladocera. Sharma and Michael (1987) noted the presence of 87 species and Michael and Sharma (1988) recorded 93 species in India. Raghunathan (1989), later, recorded 106 species and Sharma (1991) Sinha, 2018). Among Indian states, Tamil Nadu has the highest documented Cladocera species followed by Assam (Table 3). Subhash Babu and Nayar (2004)  According to the report, Cladocerans are included in 4 orders, 11 families and 48 genera (Table 4). Chydoridae has been found to be the dominant family followed by Daphniidae (Table 4). Thus, a comprehensive report on cladoceran diversity, encompassing all Indian states, is still unexplored and wanting.

Cladoceran Diversity in Rarh Belt of West Bengal
The occurrences and distributions of these natural fish-food organisms in the lateritic belt of West Bengal are so far partially documented and too fragmentary. The following studies on cladoceran diversity have been recorded in this area till date: Nandi et al. (2007) in a survey of wetland resources of Puruliya and Bankura district reported the presence of 27 Cladocera from diverse wetland types. In a similar study, Ganesan and Khan (2008) recorded 25 species included in 5 families from Purbasthali, Burdwan. Dutta and Patra (2013) recorded 4 genera of Cladoceran from Jamunabandh at Bishnupur, Bankura. Majumder et al. (2014) identified 4 genera of Cladoceran in six sampling sites spread around south-western Bankura district. In a similar study, Chatterjee et al. (2014) documented 5 Cladocera species including 3 families from Shahebbandh, a perennial lentic water body from Purulia. Bera et al. (2014) recorded 22 species belonging to 12 genera in Kangsabati reservoir in Bankura district. Mallick and Chakraborty (2015) recorded 7 families including 30 species from few selected wetlands of Paschim Medinipur district. Midya et al. (2018) recorded 10 species from some selected wetlands (in Panskura, Gokulpur, Jakpur) of Purba and Paschim Medinipur districts. The Cladoceran diversity, recorded so far from this region, is listed in Table 5:   (Sharma and Sharma 2017) Advances in Zoology and Botany 8(3): 188-198, 2020 195

Discussion
The present review revealed the updated record of 63 species of Cladocera, belonging to 6 families and 24 genera, from the red soil lateritic Rarh belt of West Bengal. This record clearly supersedes the previously documented total 56 Cladoceran (Venkataraman 1999) species from entire West Bengal. This data depicts a moderately high diversity of the taxon in this belt. The record indicates Chydoridae to be the dominant Cladoceran family followed by Daphniidae, while Bosminidae and Moinidae being the least abundant ones. (Table 6). Interestingly, 21 species out of 63, recorded in Rarh belt, do not feature in the most recent annotated checklist of "Cladoceran fauna of India", published by Zoological survey of India (Sharma and Sharma 2017). Thus, this raises the ambiguity regarding the validity of the recorded species from this area. This possibility was also remarked by Sharma and Sharma (2017), clearly stating the presence of identification lapses in Indian taxonomic literature including errors such as: 'species inquirendae' (i.e., synonymized new taxa), 'Reports inquirendae' (i.e., dubious reports), 'misidentifications and lapsi' (i.e., misidentifications and lapses). In Cladoceran taxonomy, Alona costata (G.O. Sars 1862), Simocephalus vetulus (O.F. Muller 1776) recorded in various Indian literatures are 'misidentification and lapsi' and should be rechecked with Alona cheni (Sinev 1999) and Simocephalus mixtus (Sars 1903) respectively (Sharma and Sharma, 2017). Same is for Pseudosida bidentata (Herrick, 1884), which has to be rechecked with Pseudosida bidentata (Herrick 1884). Chydorus herrmanni (Brehm 1933), Ceriodaphnia lacustris (Birge 1893), Daphnia ambigua (Scourfield 1947), Daphnia retrocurva (Forbes 1882) have been referred to as 'reports inquirendae', meaning deficiency of proper voucher specimen, illustration, description or specific location (Sharma and Sharma 2017). Chaterjee et al. (2013) mentioned Alona affinis as 'senso lato' referring it to a doubtful species and a part of a species complex. Chaterjee et al. (2013), also suggested that many Oriental species viz., Alona affinis, Leptodora  Thus, there is requirement of updation, revalidation and exploration of Cladoceran taxa in this area using modern literatures and techniques. This can unveil the unexplored Cladoceran diversity from this unique lateritic soil belt and also revalidate and justify the recorded diversity.

Recommendations
Cladocera species recorded in India so far are dubious and need further examination and reconsideration (Chatterjee et al. 2013). Thus, in order to get clear, unambiguous and holistic details of Cladoceran taxa the following recommendations need to be followed: a. More elaborate sampling should be undergone in this unique habitat type and also in other localities of ecological significance. b. Voucher or type specimens should be preserved for future reference from each unique habitat. c. Latest, updated and modern taxonomic keys should be used for unambiguous identification (Chaterjee et al. 2013;Sharma and Sharma 2017). d. If possible, molecular techniques (including bar coding) system should be applied for verification. e. Species identified from one area should be compared with similar species identified from other parts of the world for determining phylogenetic relationships.

Conclusions
Thorough study of available literatures reveals that there is scarcity of any report based exclusively on Cladoceran diversity in Lateritic Rarh Belt of West Bengal, and most information collected here is an ancillary to zooplankton study en masse. Hence, there is a dearth of comprehensive and exclusive studies on Cladoceran fauna of Lateritic Rarh Belt of West Bengal. This inadequacy of information is a handicap in comparing their diversity profile with other regions of the country and the world. Moreover, some recorded data are ambiguous, erroneous and remote, and thus, requires updation, revalidation and exploration using modern literatures and techniques.
Hence, an intensive survey, documentation and monitoring of different Cladocera species in this area is extremely essential to preserve these species and also ecosystem as a whole.