A New Species of Geogenia Kinberg, 1867 from the South Coast of KwaZulu-Natal, South Africa (Oligochaeta, Microchaetidae)

ABSTRACT Examining recently collected earthworms from a sugarcane farm in Port Shepstone, South Africa resulted in the discovery of a new species, Geogenia minnehaha sp. n. This species is similar to G. tuberosus (Plisko, 1998) but differs from it by the extended clitellum, the size and position of papillae, and the number and shape of spermathecae. The presence of an indigenous species in a sugarcane field is a new finding in South Africa, where little is known on earthworm communities in agricultural soils.


INTRODUCTION
Earthworms are a major component of macrofauna in the soil community. Earthworms play an important role in soil ecosystems; they modify the soil and regulate resources in the soil, thereby acting as ecosystem engineers that indirectly benefit humans. They also have the most significant effect on soil fertility and structure (Dlamini et al. 2001). By converting large pieces of organic matter into rich humus in the form of casts, thereby improving soil fertility and quality, they influence the regulation of soil formation. Nutrients are released from the decomposition of organic matter, as well as chemicals such as nitrogen and phosphates, and are made available in an accessible form for plants and other organisms, thus contributing to healthy soil ecology (Edwards & Bohlen 1996). The soil structure is kept open by earthworm burrows, which create passageways that allow aeration and drainage to take place. This is important because soil microorganisms and plant roots need air and water.
In South Africa there are currently three indigenous earthworm families: Microchaetidae, Tritogeniidae and Acanthodrilidae (Acanthodrilinae). Species that belong to these families tend to have a restricted distribution and are found in natural, undisturbed biotopes, mostly in primary grasslands and forests. Although earthworms in South Africa have received much more attention than in other African countries, the knowledge of earthworms in this country still needs to be greatly expanded. Previous collections in sugarcane fields in South Africa have produced only introduced earthworm species.
The effects of agriculture on earthworm fauna have not been thoroughly investigated in South Africa (Dlamini et al. 2001;Haynes et al. 2003). Little is known about earthworm assemblages in agricultural soils and their effects, and indigenous earthworm species have not been found in sugarcane fields before. A recent sampling from the KwaZulu-Natal south coast, on no-till sugarcane fields on Minnehaha Farm, revealed the presence of indigenous species belonging to Geogenia Kinberg, 1867. In this paper the new species is described and illustrated. This is the first record of indigenous earthworms in sugarcane fields in South Africa. Abbreviations: cl = clitellate, juv. = juvenile.
large but the one in 12 is highly reduced. Spermathecae in 12/13 and 13/14, one pair per segment, finger-shaped. Genital glands present on 9-13 or 9-14, with large setae. Remarks: This species is closely related to the species that occurs in Oribi Gorge Nature Reserve, which is in the near vicinity of Minnehaha Farm. This species is longer (reaching 325 mm with 551 segments), with an extended clitellum. The papillae are very large and nipple-shaped with setae in the middle; the number of spermathecae is reduced.

DISCUSSION
This species has not been found in the grassland that is adjacent to the sugarcane fields despite recent sampling within the grassland. However, the field where this species was found has not been tilled for over 20 years (Neethling pers. comm.) and this may be the reason for indigenous species occurring there. Studies by Dlamini et al. (2001) and Haynes et al. (2003) show that there are very few earthworm species found in sugarcane fields in South Africa, with all existing records being of introduced species. Most studies that look into earthworm species in agricultural fields have found that peregrine species dominate (Dlamini et al. 2001;Haynes et al. 2003;Simonsen et al. 2010). Tillage is generally known to affect earthworms more negatively than no-tillage, particularly the endogenic and anecic earthworms (Hutcheon et al. 2001;Peigne et al. 2009). In the present study, indigenous species dominated all samples. Further studies should be conducted to determine if the no-till strategy increases the presence of earthworms in sugarcane fields in South Africa or not. Future results may indicate that there may be more species to be discovered from agricultural land, and therefore more research is needed, particularly as earthworms make an important contribution to food security through their role in ecosystem services.