Parachilota abebaios, Plisko, 2008

Plisko, J. D., 2008, New South African Acanthodrilinae earthworm species, with new data for some earlier known members of the genus Parachilota (Oligochaeta: Acanthodrilidae), African Invertebrates 49 (2), pp. 21-21 : 23-24

Parachilota abebaios sp. n.

Figs 1–3

Etymology: From Greek abebaios (uncertain); refers to the unusual position of the seminal vesicles.

Diagnosis: Spermathecal pores in intersegmental furrows 7/8 and 8/9. Clitellum saddleshaped, on 13–17. Prostatic pores not approximate towards the mid-ventral line, each pair in 17 and 19. Male pores in 18. Gizzard in 5, well developed. Commencement of intestine in 16. Last pair of lateral hearts in 13. Three pairs of seminal vesicles; in 9, 11, 12. Spermathecae with unilobate diverticulum attached to spermathecal duct at its basal part.

Description:

External features: Body cylindrical. Colour: In life violet dorsally, ventrally brownish grey; in alcohol-preserved specimens dorsal violet pigmentation fading, marking only thin strip on preclitellar segments. Dimensions: holotype 95× 4 mm. Segment number: Holotype 155. Prostomium: Tanylobous with faint sutures. Setae: Distantly paired; on postclitellar segments aa>ab; ab<cd; bc <cd; distance between ab decreasing on 12–17, increasing on 19–26. Dorsal pores: Not observed. Nephridial pores: Not observed. Spermathecal pores: Paired; in intersegmental furrows 7/8 and 8/9, in front of b. Female pores: Paired, in 14 between aa. Clitellum ( Fig. 1 ): Saddle-shaped, whitish grey, on 1/n13–17; clitellar anterior and posterior borders indistinct; ventrally extending slightly below c setal lines. Prostatic pores: Paired in 17 and 19, in swellings encircling b setae. Male pores: Paired, in 18, small vertical openings ventrally to b setae. Seminal grooves: Slightly curved. Papillae: Prominent oval swellings single or paired, at a setae, on 8–10.

Internal characters: Salivary glands: Do not extend backwards beyond septum 4/5. Gizzard: In 5, well developed, cylindrical, muscular. Septa: 5/6 thin but strong; 6/7– 11/12 increasing in thickness, with 10/11 and 11/12 most thickened; 12/13 and following thin. Intestine: Commences abruptly in 16, with oesophagus enlarged in 13, followed by longitudinal ridged valves in 14–15. Lateral hearts: In 9–13 with last pair in 13 much enlarged. Nephridia: Holoic , avesiculate. Ovaries: Not observed. Testes and male funnels: Ventrally in 10; funnels large, free, iridescent. Vasa deferentia: Thick single ducts run from 10 to 18. Seminal vesicles: 3 pairs; in 9, 11 and 12; anterior pair small, commencing at septum 9/10 ventrolaterally; second pair commencing at 10/11, in 11, moderate; posterior pair commencing dorsolaterally at 11/12 largest, lobulated, tufted. Spermathecae ( Fig. 2 ): Paired; in 8 and 9; ampulla oval, small, 2.5 mm long; duct elongated, 4.5 mm long, 1.4 mm wide at its ental part; unilobate, small diverticulum 1.8 mm long, attaching to duct at its basal part, then narrows its width to nearly 0.7 mm. Iridescent sperm observed in diverticulum, and in spermathecal duct at its joint with ampulla. Ectal parts of spermathecal ducts enter body wall near septa 7/8 and 8/9. Prostates: Paired, tubular, multifolded, looped. Prostatic duct commences as muscular straight tube, extending into thin, tubular, looped and slightly coiled prostatic gland. Anterior pair confined to 17; posterior pair extends backwards, conically pushing septa 19/20–22/23 into space of three segments. Ectal parts of prostatic ducts enter body wall in 17 and 19 respectively. Penial setae ( Fig. 3 ): a and b similar, not fully mature. Penial setal retractor muscles: Commence intersegmentally in 17/18 and 19/20.

Holotype: NMSA /Olig.01851, Mpumalanga: 17 km N of Amsterdam (26°37'S: 30°40'E), on bank of small stream, in wet soil between roots of various plants, 5.xii.1992, JDP & BRS.

Distribution: P. abebaios is known only from the type locality in the north-eastern Drakensberg escarpment, Mpumalanga (the area earlier known as the Eastern Transvaal). The species occurs together with P. timothyi sp. n.

Biological notes: The large, mature, well-developed individual was collected in summer, during the rainy season.Iridescence observed in the male funnels and diverticula confirms sexual activity.

Discussion: P. abebaios is a distinct species with 3 well-developed pairs of seminal vesicles in 9, 11 and 12, the character first noted in this genus. It was observed (Pickford 1937) that in proandric Parachilota species, in which a reduction of posterior pair of testes took place, the seminal vesicles became reduced to two, having sometimes only a rudimentary posterior pair in 12 as was noted in P. stephensonianus Pickford, 1937 . P. abebaios is also characterized by a distinctive shape of spermathecae with extended spermathecal duct and unilobate diverticulum.

Figures

Figs 1–3. Parachilota abebaios sp. n., holotype: (1) anterior part of body, laterally; (2) anterior left spermatheca, 180×; (3) penial setae of 17. Abbreviations: A – ampulla, Cl – clitellum, D – spermathecal duct, PP – papillae of 8–10, UDv – unilobate diverculum.