Microchaetus tegwanus, Plisko, 2005

Plisko, Jadwiga Danuta, 2005, Five new South African earthworm species of the family Microchaetidae (Oligochaeta) with exceptional anatomical features, African Invertebrates 46, pp. 103-113 : 105-107

Microchaetus tegwanus sp. n.

Figs 1, 2 Etymology: Named after the type locality.

Description:

External features: Body cylindrical. In life pigmented dorsally, with pale violet tint; grey when preserved in alcohol. Holotype 260 mm long, 7 mm wide at 10 and 11 mm at tubercula pubertatis. Paratype 115 mm long. Segment number: holotype 420. Prostomium: prolobous, small. Segmentation: secondary annulation present on preclitellar segments; 1 and 2 simple, short, with irregular longitudinal grooves; 3 simple, longer than first or second segment; 4–8 with two simple ringlets; 9 with two annulated ringlets; 10, 11 and postclitellar segments irregularly annulated. Setae: closely paired in regular rows; aa> bc, ab = cd. Nephridial pores: conspicuous, anterior to c setae; first pair in intersegmental furrow 2/3. Female pores: in 14 between b–c setae. Male pores: in 17/18 or 18, in region of tubercula pubertatis. Spermathecal pores: obvious, in intersegmental furrows 11/12 and 12/13. Papillae: on 20, paired, moderate swellings, linked with genital glands.

Clitellar region ( Fig. 1 ): Clitellum: saddle-shaped, segmented, white, on 12,13–23; on 12 dorsally with poorly defined border; posteriorly clearly marked; laterally clitellar tissues extending to cd setal lines. Tubercula pubertatis: rectangular pads with rounded corners, irregularly creased, segmented; on 17–20, covering only partially intersegmental furrow 16/17; clearly separated from clitellar tissues by narrow rims; dorsal borders below c setae, ventral above b setae, rimmed.

Internal characters: Septa: 4/5–6/7 not thickened; 7/8 and 8/9 strongly thickened, muscular; other septa thin. Gizzard: in 7, spherical, muscular, posteriorly softened. Calciferous glands: in 9, attached closely to oesophagus, separated dorsally and ventrally. Intestine: commences in 13. Typhlosole: commences in 13 as thin tube, gradually enlarging and becoming U-shaped; in holotype terminates in 260. Dorsal blood vessel: 4–7 thin, double; 8 double, widely separated; 9 enlarged, double, cordiform; simple when crossing septa; in 10 and following segments enlarged, simple. Paired dorsoventral vessels: 5–8 thin, 9–11 enlarged, moniliform. Nephridia : holonephridia; large, bushy coiled loops, with extended V-shaped, much elongated caeca. Male funnels: holandric arrangement; two pairs, different in size and appearance. Anterior pair large, iridescent, enclosed in sacs, occupying large part of segment 10; posterior pair in 11, small, enclosed in seminal sacs closely connected at septum of 10/11. Vasa deferentia ( Fig. 2 ): commencing on lateral sides of male funnels in 10 and 11 respectively, extending to 12 where becoming close, extend as fused tubes, proceeding to intersegmental furrow 17/18, where entering body wall.It was not established if male pores are in intersegmental furrow 17/18, or proceed to 18. Seminal vesicles: one pair, large sacs, commencing at septum 10/11 extending to 11. Spermathecae: in 12 and 13; two pairs per segment; each spermatheca on enlarged base; ampulla extended and slightly bent or curved posteriorly; ectal parts entering into intersegmental furrows 11/12 and 12/13; iridescence observed in posterior parts of elongated ampullae. Ovaries: large, folded funnels in 13, adjacent to septum 13/14; oviduct simple, extending in 14 to area of c setae. Genital glands: one pair in 20; each gland composed of two finger-shaped, twisted and folded parts; in holotype anterior parts proceed to 16, posterior to 21–22, partly proceeding under intestine; both glands linked with external papillae.

Comparison and comments: This species is distinctive in having spermathecal pores in intersegmental furrows 11/12 and 12/13. Previously this character has been noted only in two other species of this genus: M. caementerii Michaelsen, 1913 and M. griphus Plisko, 2002 . However, these three species differ vastly in their body sizes, pigmentation, position and shape of their clitella and tubercula pubertatis, and thickness of septa. They are geographically widely separated narrow-range-endemics. It is noteworthy that in the majority of species of holandric Microchaetus , the spermathecal pores are present in the intersegmental furrows 12/13 and 13/14, whereas in the species of the proandric genus Proandricus the spermathecal pores occur most frequently in intersegmental furrows 11/12 and 12/13 (Table 1). M. tegwanus has two male funnels, a holandric character, although the second pair is much smaller than the anterior one. Two pairs of vasa deferentia starting in segments 10 and 11 on each side of the body, run to segment 12, where they become close and fused.

Holotype: clitellate, NMSA /Olig.03784: KwaZulu-Natal: Underberg area, Tegwan Farm (29º46'S: 29º32'E), in moist soil of grassland with rye-grass, 25.iv.2003, A. Sanders.

Paratypes: NMSA / Olig. 03782, 1 cl, and NMSA /Olig.03785, 3 juvenile, near type locality, 25.iv.2003, A. Sanders .

Other material examined: NMSA / Olig. 03776, 1 cl, and NMSA /Olig.03783, 3 juvenile, near type locality, in marshy area, 25.iv.2003, A. Sanders .

Biological notes and distribution: The species was found in grassland soil, under roots of various plants, in moderately moist and also marshy sites. The presence of sperm in male funnels and spermathecae indicates maturity and readiness for reproduction, suggesting sexual activity of this species in summer, extending into early autumn.

The type locality and other collection sites are in the foothills of the Drakensberg range in KwaZulu-Natal.

Figures

Figs 1, 2. Microchaetus tegwanus sp. n., holotype: (1) ventral view with clitellum and tuberculum pubertatis, 60 X; (2) dorsal dissection of preclitellar part of body, showing anterior parts of vas deferens, and spermathecae, 90 X. Abbreviations: C–clitellum, T–tuberculum pubertatis, Sp–spermatheca, V–vas deferens commencing in segments 10 and 11.