NEW RECORDS OF FREE-LIVING MARINE NEMATODES FROM INDIA

Free-living marine nematodes are usually the most abundant metazoans inhabiting marine benthic ecosystems, often representing more than 90% of the benthic meiofauna. Their significance in terms of habitat energy fluxes in the food chain and degradation and mineralization of organic matter are high. An important feature of nematode populations is the large number of species present in any one habitat, often an order of magnitude higher than for any other taxon (Platt & Warwick, 1980).


INTRODUCTION
Free-living marine nematodes are usually the most abundant metazoans inhabiting marine benthic ecosystems, often representing more than 90% of the benthic meiofauna.Their significance in terms of habitat energy fluxes in the food chain and degradation and mineralization of organic matter are high.An important feature of nematode populations is the large number of species present in any one habitat, often an order of magnitude higher than for any other taxon (Platt & Warwick, 1980).
Although the nematodes comprise a large fraction of marine benthic communities, only little information is available on its assemblage in India waters.Studies on marine meiofaunal taxonomy and ecology have increased considerably in the last 20 years and progress has been made in facilitating meiofaunal work by non-specialists.Significant contributions on nematode assemblage structure at the generic or specific level of the mangrove sediments from the world has been made (Hopper et al., 1973, Vanhove et al., 1992, Olafson, 1995, Olafsson et aI., 2000, Decraemer & Coomans, 1978, Hodda & Nicholas, 1985& 1986, Alongi, 1987a& 1987b, 1990, Nicholas et al., 1991, Nicholas & Stewart, 1993, Somerfield et al., 1998), while there are only three such studies from India (Krishnamurthy et al., 1984, Rao, 1986, Sinha et aI., 1987).
Pichavaram mangrove situated along the southeast coast of India (Lat.11 °27' N; Long.79°47' E), lies about 200 km.south of Chennai, the capital of Tamilnadu state and about 10 km.south of Parangipettai (Portonovo).It is one of the typical mangrove swamps of India, with a cover of about 1,100 hectares.tenuispiculum, Camacolaimus barbatus, Haliplectus dorsalis and Thalassomonhystera parva) and one genus (Pseudolella sp) were recorded for the first time from Indian waters from intertidal sediments.This paper deals with the systematic account of each species, materials collected (number of specimens and date of collection), brief description and its geographical distribution.

MATERIALS AND METHODS
The sediment samples were collected using a hand corer (3 cm.dia.) up to a depth of 10 cm.Sampling was made during low tide, mostly near the mid tide level.The sediment samples were anaesthetized with a solution of magnesium chloride isotonic with seawater and meiofauna were extracted by the standard decanting-sieving method, and were stored in 50/0 formalin.Nematodes were picked out and mounted on a drop of water free glycerin on a microscopic slide from a subsample.The cover slip was sealed using paraffin wax.Identification to species level was done under a high power microscope using the pictorial keys of Platt andWarwick (1983 &1988) and Warwick et al. (1998).Drawings were made using a Camera Lucida.The measurements of species presented in this study are based on De Man's formula, as adopted by Jensen (1978Jensen ( & 1979)).Remarks: The specimens agree well with the earlier description (Platt & Warwick, 1988).This is the first record of the species from the Indian waters.
Elsewhere: South West England: Tamar estuary, Island of Scilly and British Isles.

Remarks:
The material examined conforms well with earlier description, except for the smaller body size.The total body length described was 2.8 mm and tail length varied between 4.8-5.0a.b.d.(Platt & Warwick, 1988).The body length of the specimen studied at present is lesser being 1.3-1.4mm and tail 2.6-2.8a.b.d.This is the first record of the species from the Indian waters.Elsewhere: Northumberland coast, North East England and British Isles.

Remarks:
The material examined conforms well with the earlier description, except for larger body size.The total body length described varied between 0.7-0.8mm and tail 2.4-2.5 a.b.d.(Platt & Warwick, 1988).The body length of the present specimen is more being 0.8-0.9mm, but tail was shorter 1.1-1.6 a.b.d.This is the first record of the species from the Indian waters.Elsewhere: Exe estuary, South West England and British Isles.

Remarks:
The specimens examined agree well with the earlier description, except for the smaller body size.The total body length described varied between 1.8-2.0mm and tail 3 a.b.d.(Platt & Warwick, 1988).The body length of the present specimen is very much lesser (0.4-0.58 mm), but tail was longer 3.1-3.3a.b.d.This is the first record of the species from the Indian waters.Elsewhere: Skippers Island; Essex and British Isles.

Remarks:
The specimens examined agree well with the earlier description, except for the larger body size.The total body length described was 0.7 mm and tail 1.8 a.b.d.(Platt & Warwick, 1988).
The body length of the present specimen is 0.75-0.86mm and tail 2.1-2.3 a.b.d.This is the first record of the species from the Indian waters.Remarks: The present specimens had a larger body size.The body length being 0.9-1.3mm and tail 8.1-8.4 a.b.d.The total body length described earlier varied between 0.6-0.7 mm and tail 7.7 a.b.d.(Warwick et al., 1998).This is the first record of the species from the Indian waters.
Faunastic surveys of Pichavaram mangrove was conducted during 2002.During this study, six species (Ptycholaimellus ponticus, Paracomesoma dubium, Desmodora (Desmodorella) Material examined: 7 females, Pichavaram mangrove, 28.01.02.Description (Female) : Body slender and attenuating towards ends, 0.8-0.95mm In length.Maximum diameter of body 25-30 J..lm.Cuticle annulated; lateral files raised with longitudinal rows of coarse dots; four longer cephalic setae 7-10 J..lm in length; four files of short setae down body length, each situated slightly median to the longitudinal files of cuticle dots.Amphids transverse slits immediately posterior to cephalic setae.Buccal cavity with large strongly cuticularised S-shaped dorsal tooth and a dorsal apophysis.Oesophagus swollen dorsally at anterior end around dorsal tooth with an elongate double posterior bulb.Tail tapering, 3.5-3.7 a.b.d., with distinct spinneret.Ovaries opposite, reflexed, anterior ovary to the right of intestine and posterior ovary to the left.Male: Not found.Distribution: India (Tamil Nadu) : Pichavaram mangrove.Elsewhere: North East England: Blyth estuary, South West England: Exe estuary, South West England : Tamar estuary, Essex : Skippers Island, North East coast of England, British Isles and North Wales.