Earthworm Ecology in the Northern Part of Iran: With an Emphasis on Compost Worm Eisenia fetida

MATERIALS AND METHODS

Environment condition: Being situated by the Caspian Sea, Gilan province has a temperate Khazari (Caspian) climate. Talesh Mountains extending from the north to the south and Alborz Mountains from the west to the east prevent the water vapor of the Caspian Sea and the northwestern humid winds from entering the rest of Iran. Also, the high altitude of these mountains causes enormous amounts of rain in the region. In some parts, relative moisture in warm months reaches 89 percent and this moisture is the same factor that modifies the temperature in the summer and winter. There are hardly any freezing days in this province. In Gilan, the greatest amount of rain falls Chaboksar and varies between 1000 and 2000 mm. Rudbar and Loushan, too, are among the regions having the most precipitation.

In general, Mazandaran has a moderate and humid climate known as the moderate Caspian climate. The effective factors behind such a climate are: Alborz mountain range, direction of the mountains, height of the area, neighborhood to the sea, vegetation surface, local winds and altitude and weather fronts.

As a result of the above factors, three different climates exist in the region:

Plain moderate climate: It covers the central and western plains of Mazandaran. The average annual rainfall amounts to 1200 or 1300 mm and as we proceed to the east the amount decreases.

Mountainous climate: It covers the high mountains and northern parts of the Alborz range. In the heights, the weather is cold mountainous and most of the precipitation is in the form of snow.

Semi-arid climate: This climate prevails some parts of Gorgan valley (north of Gorgan Rud as far as the Turkmenistan border). In this area, the average annual rainfall stands at 500 mm.

In addition to the suitable climatic conditions of the Iranian coastal provinces of Gilan, Mazandaran and Golestan, this region enjoys a very fertile soil excellent for agricultural purposes. Therefore, this region has a special and prominent status in the country. In the plain region of Gilan, due to the wet climate, most of the soil is sedimentary with small grains. Also there are wet grassy and semi-wet soils as well. The sedimentary soils with small grains are the most appropriate kind of soil for agricultural purposes. This type of soil has covered vast areas of the central plains of Mazandaran, which is considered as one of the most fertile parts of this region. In the plains of Gonbad and Gorgan in the Golestan Province, due to the extensive evaporation and presence of semi-arid lands especially in the northern part of the province, there are vast salty and marshy lands without any agricultural value. Never the less, in the southern part of this province, near the Gorgan and Gonbad region, there are arable lands that are considered as the main center for cultivation of grain, cotton and oily seeds. The soil in the mountainous region of this province, due to the sharp slope of the mountains and the shallow depth of the soil is not very suitable for cultivation.

Three collection methods were used to identify the earthworm species in this study.

Hand-sorting: Soil was dug using a quick levering action to collect large worms. Then the collected samples spread on a sheet for hand sorting^[7].

Chemical extortion: The chemical extractants used to sample earthworms were formalin and potassium permanganate. The 0.55% formalin solution was prepared using 15 mL of 40% formalin in 4.56 L water applied to 0.36 m² of surface^[1].

Fig. 1:	Distribution of earthworm in studied areas in Iran

Heat extraction: This method was used to obtain small surface-living species from soils. A container sizing 55x45 cm with a wire sieve of 5 cm from its bottom was used. Soil quadrates are placed on the sieve, immersed in water with fourteen 60 watt light bulbs suspended above and left for 3 h^[1].

This study was conducted from Aug. to Dec. 2003. The information included the place name, the sampling date, the soil properties was recorded during each sampling methods. The studied areas and the species found were shown in Fig. 1. Earthworms for reference collections and morphological studies should be relaxed before killing. In this regard, the earthworms were place in 5 and 10% formaldehyde solution and then stored in 60% ethyl alcohol^[8,9]. Firstly, the adults' specimens were selected and placed in water. Then the specimens were placed in a mixture of formalin and ethyl alcohol (a solution with 2 volumes formalin and 1 volume ethyl alcohol). The data were written on the designed record cards.

Because no investigation was conducted before Omrani^[9], it is possible that the identified species to be the native of this region. However, the region has been affected through environmental changes by residents.

Eisenia fetida rearing: Two wooden boxes sizing 70x50x15 cm (length, width and depth, respectively) were made for rearing E. fetida. The surface area of each box was 0.35 m². The cowdung and horse manure were used as feeding substrates. 100 clitellated E. fetida were added to each box incubated in a room temperature from 18 to 22°C. The moisture content of the substrates kept at 50-70% with regular sprinkling of water during the study.

RESULTS AND DISCUSSION

Families, Genera and species in Mazandarn: All the species were fixed in laboratory and send to Prof. Graff and Zicsi to be identified. Results of investigations revealed the presence of two families: Lumbricidae and Megascolecidae. The following genera and species were identified:

Rearing E. fetida in Cowdung and horse manure: Cocoon production and hatchlings for two substrates over the 130 days are provided in Table 1 and 2. It is observed (Table 1) that the overall hatchlings in horse manure for E. fetida was 9025. In addition, the cocoon production in horse manure increased until day 80 and after that the number of cocoons decreased, so that the maximum overall cocoon production occurred in day 80 was 1143. The overall hatchlings in cowdung by the end of the study (day 130) was 10452 for E. fetida. As with the horse manure, the cocoon production in cowdung increased until day 80 after which a decreased was observed in cocoon production (Table 2).

The objective of the study was to identify the earthworm species with an emphasis on investigation of manure worm E. fetida characteristics. Samples were taken from the places where residents are living and wastes are disposed of throughout the region. Eight species were identified: A. caligniosa, A. kaznakovi, A. jassyensis, A. rosea, D. veneta, D. bublica, E. fetida and Pheretima indica.

The results showed that the abundance of each species is as follows. The results show the overall percent of the collected species throughout the region. A. caliginosa was the dominant species with an abundance of 23.7%.

Table 1:	Cocoon production and number of hatchelings of E. fetida in horse manure

Table 2:	Cocoon production and number of hatchelings of E. fetida in cowdung

This species influences on soil structure, increases soil macroporosity, aerates the soil and improves its water-holding capacity.

The abundance of A. kaznakovi, A. jassyensis and A. rosea were 7.3, 4.5 and 3.2%, respectively. These species were collected and identified from forest soils. In general, A. rosea were found in woods but A. caliginosa were found in farms.

The abundance of E. fetida was 18.1% that shows a wide spread distribution over this area. E. fetida species were collected from rich organic soils, municipal solid waste dumps and manure heaps. With regard to its high distribution and natural presence in organic wastes, E. fetida can be used in waste decomposition and treatment. This will result in waste minimization and decrease cost of waste handling.

The abundance of D. byblica and D. veneta were 17.7 and 7.3%, respectively and that of P. indica was 6.4%. The samples of D. byblica and D. veneta were collected from surface layers of forest soils and P. indica was taken from forest soils with high moisture content. It should be noted that 6.8% of samples was immature that was removed in identification stage and due to no taxonomy investigations on the samples 5% could not be identified by the available keys; thus further studies would be needed. D. veneta and A. jassyensis were generally identified in the samples from the soils of virgin jungles.

Most species are from epigeic species category but because parts of the samples were taken during high temperatures (>23°C) we had to dig the ground up to 30 cm.

On the basis of the results from cocoon production and hatchlings it might be concluded that the largest number of cocoons produced in day 80 that was 1415 and 1143 for cowdung and horse manure, respectively. The number of young earthworms obtained after 130 days were 10452 and 9052 in cowdung and horse manure, respectively. The reason for decrease in cocoon production might be attributed to increase of hatchlings density in rearing wooden boxes. In general, it can be concluded that cowdung is more preferred for rearing E. fetida.

ACKNOWLEDGMENTS

The authors would like to thank Prof. O. Graff and Prof. A. Zicsi for their contributions in earthworms' identification. We would also thank Baboul research Center for providing facilities and equipment during the investigation.