Microchaetus idechoritus, Plisko, 2003

Plisko, Jadwiga Danuta, 2003, Eleven new South African earthworms (Oligochaeta: Microchaetidae) with new information on some known species, and an inventory of the microchaetids of KwaZulu-Natal, African Invertebrates 44 (2), pp. 279-325 : 284-286

Microchaetus idechoritus sp. n.

( Figs 4–5 )

Etymology: G. ide = forest, G. chorites = indigenous. Refers to the species habitat.

Material examined: KwaZulu­Natal: Holotype NMSA /Olig.02188 Ngele Forest (30º35'S: 29º41'E) indigenous forest, from first 20 cm of black, moist soil, 24 November 1995, JDP, BRS. Paratype NMSA /Olig.03716 one not fully mature, abscised postclitellarly, collected with holotype .

Description based on holotype and paratype.

External characters:

General: body cylindrical, contracted during preservation. Colour: holotype and paratype preserved in alcohol dorsally violet, ventrally yellowish­grey. Dimensions: holotype preserved, slightly contracted 115 mm long, 5 mm wide at 10, 7 mm wide at tubercula pubertatis; paratype abscised 94+ mm long, 5 mm wide at 10, 7 mm at tubercula pubertatis. Segment number: holotype 198. Prostomium: prolobous, moderate. Segmentation: secondary annulation present on preclitellar segments; 1 and 2 short, with clear intersegmental furrow 1/2, both segments with irregular longitudinal grooves; 3 simple, long as 1+2; 4–8 with two ringlets similar in size and appearance; 9 with two ringlets, second shorter than first; 10 and following simple. Setae: closely paired; ab = cd, aa> bc. Nephridial pores: obvious, in c or little below c setae. Female pores: paired in 14, above b setae. Male pores: obvious, in 18 above b setae, with elongated small swellings. Spermathecal pores: externally not observed; locations of spermathecae indicate intersegmental furrows 13/14 and 14/15 respectively.

Clitellar region ( Figs 4–5 ): Clitellum: saddle­shaped, white, elongated, clearly segmented, on 12–21 with anterior and posterior borders clearly marked; on 12–15 ventral borders extend to ab setae; on 16–18 bordering tubercula pubertatis; on 19–21 covering only dorsal parts of segments. Tubercula pubertatis: on holotype elongated glandular, segmented, yellowish tissues on 16–18; ventrally extending to b setae, dorsally below nephridial pores. Papillae: paired, small, glandular swellings on 10 and 12, encircling ab setae.

Internal characters:

Septa: 4/5 5/6 and 6/7 thin; 7/8 and 8/9 thickened moderately, muscular, both similar in size and appearance; 9/10 and other septa thin. Gizzard: cylindrical, large, muscular, in 7. Calciferous glands: in 9, dorso­ventral, separated dorsally and ventrally. Intestine: commences in 13. Typhlosole: in holotype commences in 13 as large U­shaped tube, enlarging backwards, and terminates in 136. Dorsal blood vessel: 6–7 partly double, partly separated; 8 double, separated, 9 close, cordiform. Paired dorsoventral vessels: 5–8 thin; 9–11 moniliform. Nephridia: meganephridia ; coiled loops with extended Vshaped caeca. Spermiductal funnels: holandric arrangement; two pairs of large funnels in 10 and 11 respectively, both closely connected at their posterior parts with seminal vesicles; anterior pair iridescent, posterior not iridescent. Vasa deferentia : two obvious ducts closely connected, commencing at lateral side of posterior pair of spermiductal funnels, run backwards to anterior part of segment 18. Seminal vesicles: one large pair of sacs commencing at septum 10/11, closely attached to spermiductal funnels, extends into segment 11 and terminates at 11/12. Spermathecae: in holotype, elongated clubshaped thecae in 14 and 15; anteriorly paired; posteriorly much smaller, 3 at left side, 2 at right side. In aclitellate paratype developing tubercula pubertatis, spermathecae were not observed. Ovaries: not observed. Genital glands: flat, small glands in 9–12; in 14– 17 finger­shaped composite of 2–3 parts; in 18 composite of 4 long finger­shaped glands. Biological notes: Ngele Forest, part of the much larger forest complex of Weza State Forest, incorporates natural vegetation of Podocarpus trees, thick bush and shrubs characteristic of afromontane forests. Although this complex was surrounded by plantations of pine, cypress and poplar trees, these were absent at the collecting site. Thick layers of decomposing litter and black moist soil were abundantly inhabited by microchaetid Tritogenia ngelensis Plisko, 1997 , indigenous acanthodrilid of the genus Parachilota , and by introduced Dendrodrilus rubidus (Savigny, 1826) of Lumbricidae . However, only two idechoritus specimens were collected.

Distribution: Known only from the indigenous part of the Weza State Forest ( Fig. 1 Ngele Forest), in southern KZN.

Discussion:A distinct species with spermathecal pores in intersegmental furrows 13/14 and 14/15, and male pores in segment 18. Only three other species of this genus, herberti , natalensis and parvus , have their spermathecal pores in these furrows. However, all four species differ in general appearance, size, position of clitellum, and shape of tubercula pubertatis.

Figures

Figs 4–5. Microchaetus idechoritus sp. n., holotype. 4. Dorsal view of clitellar region. 5. Lateral view, with enlarged area of tuberculum pubertatis. [C = clitellum, T = tuberculum pubertatis].

Fig. 1. The distribution of species of Microchaetus and Michalakus in KZN. Microchaetus: 1 = ambitus; 2 = caementerii; 3 = distasmosus; 4 = griphus; 5 = herberti; 6 = idechoritus; 7 = mkuzi; 8 = natalensis; 9 = papillatus; 10 = parvus; 11 = pondoanus; 12 = quaerus; 13 = tuberosus; 14 = vernoni; 15 = zaloumisi; 16 = Michalakus initus.