Durairajan Selvamuthukumaran and Periyasamy Neelanarayanan
Abstract
An attempt has been made to study the diversity, spatial and temporal distribution of earthworms in Southern thorn forest, Kolli hill. The present study was carried out between June 2009 and May 2011. A total of five species of earthworms viz., Drawida gracilis Gates, 1925, Drawidabullata Gates, 1933, Perionyxceylanensis Michaelsen, 1903, Megascolex bidiverticulatus Selvamuthukumaran, 2025 and Hoplochaetella stuarti Bourne, 1886. However, of these, only three earthworm species viz., D. gracilis, H. stuarti and M. bidiverticulatus were found in the study area all through the study period, with a few exceptions, while the other two species namely D. bullata and P. ceylanensis were found only in the sampling site-I (Vasalurpatti). The M. bidiverticulatus were found to be maximum in number in the sampling site-IV (Velikkadu) when compared to other sampling sites, moreover, M. bidiverticulatus was not found in the Vasalurpatti. All the five collected earthworms are ecologically termed as epigeics as they were collected at the depth of 0-10 cm layer during the present study. In general, the results of the present study indicated that all the five species earthworms enumerated during the first year of study (June 2009 to May 2010) were comparatively lower than the second year (June 2010 and May 2011) of study. The change in the earthwormsâ populations might be attributed to comparatively low rainfall (893mm) during the first year than the second year (1865 mm). It is inferred from the results that in general earthworms which belong to all five species were observed only during rainy seasons of both years of study with a few exceptions across the four sampling sites. Further, D. gracilis and H. stuarti (except in Velikkadu) could not be observed in summer season as well. M. bidiverticulatus was recorded during summer season only in Velikkadu but not in Pinnam and Kadambalam. None of these five species of earthworms were observed during winter season in all the four sampling sites and two years of study.