MEIOFAUNA OF GULF OF MANNAR

Meiofaunal organisms are mobile metazoans, which are smaller than macrofauna and larger than microfauna. Meiofauna can be defined as those animals, which will pass through a sieve with a mesh size of 0.5 mm but be retained by 0.045 mm sieve. Some reach 1 or 2 mm in length but can pass through the larger sieve because they are long and slender. Being small and less conspicuous, they are often ignored altogether. Meiofauna live in both freshwater and Marine habitats. The meiofauna often extremely abundant in fine particle beaches, sometimes exceed the macro fauna in biomass in coarser sands. They also inhabit complex surfaces and the spaces between them such as are found on seaweeds and other structures.

and its equivalent terms Mesopsammon introduced by Remane (1940) are often confused with the term meiofauna.Organism living in the interestitial spaces between particles of all types of sediment are referred to as interestitial if they move through the habitat with a minimum of disturbances of constituent particles.The term meiofauna is derived from Greek Meio meaning "smaller".In this context it refers to the fauna smaller than what has been defined as the lower size limit for macrofauna.
Nematodes populating North American shores (Cobb, 1914(Cobb, , 1920) ) and the Archiannelids of the Northern French coast (Giard, 1904), Remane who is described as the "father of Meiofaunal research" was the first to recognize the rich populations in intertidal beaches, subtidal sands, muds and algal habitats.Remane described Gastrotricha, Rotifera, Archiannelids, Kinorhyncha and other taxa.
The free-living marine nematodes usually constitute the most abundant group of organisms in the meiofauna of littoral sediments.The works of Wieser (1953Wieser ( , 1954Wieser ( , 1956)), Timm (1961) and Gerlach (1962Gerlach ( , 1963Gerlach ( , 1964) ) proved quite useful in the identification of many common genera and species of these marine nematodes.
Total and relative measurements of body are absolutely necessary for identification of marine nematodes.Structure of stoma, cup shaped with minute teeth, structure of tail, types of oesophagus, types of Amphids, are the identification characters.For this the Demanian formula is usually is employed indicating, a = total body length/maximum body diameter, b = total body lengthllength of tail.The position of nerve ring, excretory pore and vulva is expressed in percentage of body or oesophageal length.Brady (1884) has given an exhaustive and excellent account of the Foraminifera from the dredgings of the Challenger' expedition which crossed the Indian Ocean far to the southof the Peninsula.Chapman (1895) reported on the Foraminifera obtained by the Royal Indian Marine survey ship S.S. 'Investigator' from the Arabian Sea near Laccadive Islands.Stubbings (1939) reported on the distribution and biology of nearly 300 species of Foraminifera from the Marine deposits of the Arabian Sea collected during the Johan Murray' expedition.Carter (1888) on the specimens dredged up from the Gulf of Mannar.Dakin (1906) recorded 131 species of Foraminifera from the Gulf of Mannar off Ceylon coast.Gnanamuthu (1943) has listed 47 species of littoral Foraminifera from the Krusadai islands in the Gulf of Mannar.The identification of various families and genera is based on the classification adopted by Cushman (1948) K.M.S. Ameer Hamsa (1971) reported Foraminifera of the Palk Bay and Gulf of Mannar.Ganapati and Satyavati (1958) recorded the Report on the Foraminifera in bottom sediments in the Bay of Bengal off the east coast of India.
Sewell (1919,1924) reported on the copepod fauna of Chilka Lake and more recently Devasundaram and Roy (1954) have discussed briefly the occurrence and seasonal variations of the copepods in the plankton of the Chilka Lake for the period 1950-1951.

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There are brief references to Copepoda in the accounts on the brackishwater fauna of Adyar and other estuarine areas around madras, by Panikkar and Aiyar (1937), Krishnaswamy (1953) and Chako et oZ. (1953).Sewell (1919) described a new copepod from the Cochin backwater.The first attempt of making a systematic study and ecology of the planktonic copepods of the Cochin backwater was made by George (1958).Pillai (1970) while giving a list of the Pseudodiaptomus Herrick.The following authors also have contributed to our knowledge of the copepods on habiting brackish waters of India: Kasturirangan (1963), Sewell (1948, 1956) and Ummerkutty (1960).All the above studies have recoded a total of 62 species of Calanoid copepods from different estuaries in India as follows.

MATERIALS AND METHODS
The meiofauna along the beach are collected and field studies made during low tide when the inter tidal zone is fully exposed.A Perspex corer having 40 cm long and had an internal crosssectional area of 10 cm 2 was used for the collection of the sand samples (Nybakkan, 1997).The corer tube was vertically thrust into the beach sand up to 10-30 cm and the top portion of the corer was tightly closed with a ruber bung.Later the corer was carefully removed from the substratum, without disturbing the entire samples.To each core sample was added 4% solution of formaldehyde as preservative and a few drops of rose Bengal for necessary staining.In the laboratory, the meiofauna was extracted by washing with 10% solution of magnesium chloride.Then the solution was filtered on a 63 /lm dismeter mesh size plankton cloth and the concentrated organisms were carefully collected in petridishes.Later the organisms were sorted into different groups and numerically counted up to species level.

SAMPLE PROCESSING
Sampels were processed in the laboratory using the methods of Higgins & Thiel (1988) to extract the fauna from the sand grains.Each sample in the vial is stirred with filtered sea water.The supernatant was decanted on to a 63 /lm sieve and the fauna were preserved in 4% buffered formalin with rose Bengal stain.The Meiofauna collected on a finer sieve is then washed into a petridsh, examined and counted under the binocular microscope.

Sphaerolaimus pacificus
Totally five species of nematodes were dominated, which occurred in all the 16 stations i.e., Daptonema sp. ( 1

Species Stations
No.