ROLE OF MICROBIAL FLORA ON DISTRIBUTION OF COLLEMBOLA AT WASTE DISPOSAL SITE, DHAPA, KOLKATA

The ecology of collembolan fauna as well as microbial communities in soil was studied earlier in India by several workers like Mitra et al., (1977), Alfred et al., (1991), Hazra and Choudhuri (1981, '83) and Hazra et al., (1976, '99, 2003). But studies on the distribution of soil fauna in general and Collembola with association of microbial flora in particular in tropical countries have not been undertaken seriously, especially in India. The present study deals with the association of the predominant species of microbial flora and their role on distribution of Collembola at waste disposal site, Dhapa, Kolkata.


INTRODUCTION
The ecology of collembolan fauna as well as microbial communities in soil was studied earlier in India by several workers like Mitra et al., (1977), Alfred et al., (1991), Hazra and Choudhuri (1981, '83) and Hazra et al., (1976Hazra et al., ( , '99, 2003)).But studies on the distribution of soil fauna in general and Collembola with association of microbial flora in particular in tropical countries have not been undertaken seriously, especially in India.The present study deals with the association of the predominant species of microbial flora and their role on distribution of Collembola at waste disposal site, Dhapa, Kolkata.

Location and Characteristic of sampling site
The site is a dumping ground of city wastes, located by the side of Eastern Metropolitan by pass, Kolkata.The area is demarcated by 'Organic Fertilizer Pvt.Ltd.' The main constituents of the dumped materials were household wastes, industrial effluents and the residues of vegetables.
In this sampling site cultivation of different vegetables (Seasonal salad leaves, cauliflower maize etc.) is practiced mixing the decomposing materials in the soil.

MA TERIALS AND METHODS
Methods of sampling: Soil samples were collected at random, at the rate of 3 samples every month during June, 2002to November, 2003.Therefore, 54 soil samples were drawn by using a stainless steel corer (inner cross sectional diameter 8.5 sq.cm) from a depth of 5 cm.Separate sample units were taken for the soil microbes.The soil samples thus collected were kept immediately in sterile polythene packet and stored in 4°C in the laboratory.
Extraction of Collembola : Collembola were extracted from the soil using Tullgren 'funnels as modified by McFadden (1953).A 40 watt bulb was used for heat and light source.Soil samples were placed on wire screen (2 mm mesh) in the funnels approximately 15 em below the bulbs.
Collection jars (200 ml) with approximately 50 ml 700/0 ethanol plus 50/0 glycerin were attached below the funnels and the extraction period was 3 days.Specimens collected were identified as far as possible to species level and quantified to estimate the col1embolan densities of the sites.
Isolation of soil microbes: (Bacteria, Actinomycetes and Fungi) : Considering the variety of microorganisms harbored in soil, it is apparent that no single method can reveal the total microbial population.The techniques available to study the soil microorganisms the dilution plate method is most widely used.With wide acceptance and popularity three are money variation of this technique Johnson et al., (1959) gave a good description of the detail procedure.Through the viable colony count from a plating of diluted soil suspension however, it must be recognized that a single medium and a prescribed condition of incubation with not support the growth of all species in any group of these microorganisms.In this present investigation, sterile de-ionized double distil1ed water was used to prepare the soil suspension for dilution series.

OBSERVATION
A total number of 1,078 microbes and collembolan were obtained from this site.The specimens which were found to occur in all the sampling months were identified up to generic/specific level and those showing irregular distribution were kept as unidentified and mentioned here as others.
Microbes were the dominant group obtained from all the samples and comprised of 53.70% of the total population.Among the microbes, the Penicillum was most dominant and comprised of 10.66% of the total population and occupied second position among the total fauna.Rhizopus and Bacillus (both 6.02%) Mucor (5.470/0) and E. coli (4.35) occupied second third and fourth position respectively in order of dominance.Other unidentified microbes comprised of 21.150/0 of the total population.Among the collembolan population, Lepidocyrtus cyaneus was most dominant species among all the fauna obtained and comprised of 12.330/0 of the total population.Xenylla obscura (6.700/0) Cyphoderus javanus (6.500/0), Seira indica (5.10%), and Cryptopygus thermophilus (4.900/0) occupied second, third, fourth and fifth position respectively in order of dominance and other collembolan comprised of 10.900/0 of the total population.
Percentage of total number of microbes and collembolan collected in each month showed maximum in the month of October and mininlum in the month of June (Table 1 and Figs. 1-3).

DISCUSSION
Altogether five genera of soil microbial flora (Penicillunl, Rhizopus, Bacillus, Mucor and E. coli) and five genera of collembolan fauna (Lepidocyrtus, Xenylla, Cyphoderus, Seira and CryptopygllS) were obtained during the present study.In order to find out as to whether there was any significant correlation between soil microbes and collembolan population, correlation coefficient (r) were worked out (Table 2).The population of collembolan throughout the period of sampling exhibited positive correlation with soil microbes.
microbes and collembolan showed and irregular trend of fluctuation during the salllpling period.The population of different species of the groups showed peaks in different months but in general they showed maxima in post monsoon and minima in monsoon.
It is interesting to note that the microbial population showed an almost parallel pattern of fluctuation with that of Collembola.This coincided with the observations ofKnight (1961),Mitchell and Parkinson (1976),Hazra and Choudhuri (1990), P~l et al.,(1992)  andHazra (1984).