Microchaetus griphus, Plisko, 2002

Plisko, Jadwiga Danuta, 2002, Three new earthworm species of Microchaetus Rapp, 1849, and new data on two earlier known species of this genus (Oligochaeta: Microchaetidae), African Invertebrates 43, pp. 205-214 : 205-208

Microchaetus griphus sp. n.

( Fig. 1 )

Etymology: L. griphus = riddle, puzzle. Refers to the unusual conjunction of internal characters noted in this species.

Material examined: SOUTH AFRICA: KwaZulu-Natal: Richards Bay (28º50'S: 32º08'E), from garden soil, 3 May 1998, B. R. Stuckenberg leg: Holotype NMSA / Olig. 02752 clitellate, well developed. Paratypes: NMSA / Olig. 03545 one clitellate and 5 juveniles collected together with holotype .

Description based on holotype and paratypes.

External characters:

General: Body cylindrical. Colour: In life anteriorly violet, postclitellarly only dorsally violet, ventrally grey; preserved in alcohol for over three years, holotype and clitellate paratype manifest violet colouring around their three anterior segments; segments 4– 12 violet only dorsally; ventrally yellowish-grey; postclitellarly yellowish-white; juveniles grey, with trace of violet colouring dorsally on first four segments. Dimensions: Holotype preserved, contracted, abscised postclitellarly 42 mm long, 5 mm wide at segment 10, 8 mm wide at tubercula pubertatis; clitellate paratype abscised at segment sixty, 43 mm long, 7 mm wide at clitellum; juvenile paratypes 32–72 mm long, 2–4 mm wide. Segment number: Holotype 76+, clitellate paratype 60+, juveniles 285–390. Prostomium: Prolobous, moderate; clearly separated from first segment. Segmentation: Secondary annulation present on preclitellar segments; 1 and 2 short, simple, with clear intersegmental furrow 1/2, both with irregular longitudinal grooves; 3 simple, longer than 2; 4–5 with two ringlets similar in size and appearance; 6–9 with two ringlets, first longer than second; 10–12 and postclitellar segments simple with transversal annulation incomplete. Setae: Minute, closely paired; in front of clitellum aa <bc, ab = cd. Postclitellarly aa> bc. Nephridial pores: First pair in intersegmental furrow 2/3; near cd setae; conspicuous in clitellar intersegmental furrows. Female pores: On 14, posteriorly to cd setae, below ventral borders of clitellum. Male pores: Probably in intersegmental furrow 17/18 where there are small depressions, or in posterior part of segment 18 marked by tiny indents. Spermathecal pores: In intersegmental furrows 11/ 12 and 12/13.

Clitellar region ( Fig. 1 ): Clitellum: Saddle-shaped, elongated, clearly segmented, white; extends over segments 13–25; ventral borders nearly in cd setal lines; on segments 17–20 separated from tubercula pubertatis by deep longitudinal furrows. Tubercula pubertatis: On holotype nearly square glandular bands, rounded at corners, on segments 17–19, extending partly on 20; rimmed all around, separated from clitellum by elongated, deep depressions. On one incompletely mature paratype the tubercula differ slightly in shape, being rather elongated bands, much narrower than these observed on holotype; separated from clitellum by deep furrows on segments 17–20, and rimmed ventrally. Papillae: On holotype one pair of large glandular swellings on segment 13; on paratype paired on 13 and 14. In both cases associated with genital glands.

Internal characters:

Septa: 4/5 and 6/7 thickened moderately, partly muscular, firm; 5/6 thickened the most, muscular and much thicker than both neighboring septa; 7/8 and 8/9 thickened less than 4/ 5 or 6/7, however firm. Gizzard: Cylindrical, muscular, in 7. Calciferous glands: In 9 large hemispherical glands, clearly separated dorsally and ventrally. Intestine: Commences in 13. Typhlosole: Commences in 19 as very thin,V-shaped tube, slightly enlarging posteriorly; termination could not be established because both mature specimens were abscised close to clitellum. Dorsal blood vessel: In 4–5 very thin, simple; 6–7 double in posterior part of segments, thin, close; in 8 double, thin, widely separated; in 9 enlarged, double, cordiform. Paired dorsoventral vessels: 4–8 simple, thin tubes; 9–11 enlarged, moniliform. Nephridia: Meganephridia ; coiled loops with clear V-shaped caeca.

Reproductive organs: Spermiductal funnels: Holandric arrangement (two pairs); in segment 10 and 11; anterior pair located ventro-laterally, closely connected with seminal vesicles at septum 10/11; posterior pair very much ventrally, connected and enclosed with seminal vesicles at their ventro-lateral sides. Detection of the second pair is only possible by bending laterally the dorsal sides of seminal vesicles and investigating their ventral position. Vasa deferentia: Commencing on lateral sides of spermiductal funnels in segments 10 and 11 respectively, extending transversely before curving posteriorly to run to anterior parts of segment 12 where they become very close, and run backward to posterior parts of segment 17; penetrations into body wall occur at intersegmental furrow 17/18, where both ducts enter into anterior parts of segment 18. Seminal vesicles: In holotype a pair of large sacs commencing at septum 10/11, extending into segment 11 as nearly square vesicles with elongated, curved extensions situated dorsally in segment 12; both vesicles at their ventral bases enclose spermiductal funnels of segments 10 and 11 respectively. In paratype anterior parts of vesicles extend into segment 11 as irregularly shaped elongated sacs with narrow extensions protruding into segment 12. Spermathecae: Small, bent or coiled, elongated thecae in segments 11 and 12; two per segment, distant, close to septa 11/12 and 12/13. Ovaries: In posterior part of segment 13 in shape of ribbon-folded rosette. Genital glands: In holotype one pair of oval, flat glands in segment 13, associated with papillae. In paratype paired, flat, rosette-shaped, in segments 13 and 14, also associated with papillae.

Distribution: Known only from the type locality in KwaZulu-Natal.

Biological notes: Found in a garden containing indigenous trees and shrubs, in the Meer-en-See section of Richards Bay. This locality is immediately inland of the coastal dunes, where many vestiges of sand forest and bush still occur among the houses; originally the area must have been densely wooded. Although the soil is loose, very sandy, and lacking in humus, it supports luxuriant vegetation with many trees, probably because the water table is not far below the surface, as is shown by the many small bodies of open water occuring permanently in depressions in the area. Two mature specimens collected together with five juveniles suggest an ability of the species living in cultivated soil; however, its extended adaptation cannot be confirmed.

Discussion: This species is considerably distinctive from other known holandric species. The occurrence of spermiductal pores in intersegmental furrows 11/12 and 12/13 is known in caementerii Michaelsen, 1913 b, the only other species of this genus with this characteristic. No other similarity between these two species was noted. They differ in body size, shapes and positions of clitellum, tubercula pubertatis and seminal vesicles, and in the number of thickened septa.

Figures

Fig. 1. Microchaetus griphus sp. n. Clitellar region, ventral view with clitellum and tubercula pubertatis. C = clitellum. T = tubercula pubertatis; P = papilla of segment 13.