Chilota dilatus, Plisko, 2007

Plisko, Jadwiga Danuta, 2007, New species of South African acanthodriline earthworms of the genera Eodriloides and Chilota, with a redescription of Chilota quindecimus (Oligochaeta: Acanthodrilidae), African Invertebrates 48 (2), pp. 33-40 : 36-38

Chilota dilatus sp. n.

Figs 3–5

Etymology: Latin dilatus (extended). Refers to projecting prostatic papillae.

Diagnosis: Clitellum circular, on 13–1/n17. Prostatic pores in 17 and 19 on prominent papillae extending into curved hook. Salivary glands not extending beyond septum 4/5. Gizzard in 5. Commencement of intestine in 15. Last pair of lateral hearts in 12. Spermatheca elongate, with duct narrow, bent in half of its length, with unilobate diverticulum. Prostates confined to segments 17 and 19; each originates as short, thin tube, and extends in recurved tubular prostatic gland.

Description:

External features: Body cylindrical. Colour: violet pigmentation present on alcohol-preserved material. Dorsally violet pigmentation extending to b setal lines; ventrally yellowish grey. Dimensions: holotype 50× 2 mm; other material 49–70 mm long, 2–4 mm wide. Segment number: holotype 88. Prostomium: tanylobic, with wide obvious sutures. Setae: widely paired, postclitellarly aa> ab, aa> bc, ab <cd, bc nearly equal to cd. Dorsal pores: absent. Nephridial pores: externally not observed. Spermathecal pores: ventrolaterally, two pairs, each between b–c, close to intersegmental furrow 7/8 and 8/9, respectively, with obvious swellings. Female pores: paired, in 14 between aa setae. Clitellum : ring-shaped on 13–16,1/n17; anterior and posterior clitellar borders obvious. Prostatic pores: two pairs not approximated towards the mid-ventral line; on 17 and 19, respectively, on prominent papillae stretching out into curved hook ( Figs 3, 4 ); on holotype both papillae large, conical, with hook-like extensions, encircling b; on paratypes anterior pair on large, conical papillae with hook-like extensions; posterior pair on prominent conical papillae. Male pores: paired, in 18, lateral to b setae. Seminal grooves: invaginated curved furrows. Papillae: minute oval disks on some preclitellar segments.

Internal characters: Salivary glands: slightly covering septum 4/5. Gizzard: reduced, narrow. Septa: all septa thin; 12/13 the most thickened. Intestine: commences abruptly in 15; preceded by enlarged, muscular region of oesophagus in segments 12–13, followed by valve in 14. Typhlosole: absent. Lateral hearts: three pairs; last pair slightly enlarged in 12. Nephridia : elongated, with small terminal vesicles. Ovaries: not observed, probably in 13, covered by decomposed tissues. Testes and male funnels: proandric arrangement; funnels large, in segment 10, free, iridescent. Vasa deferentia : not observed, covered by decomposing tissues. Seminal vesicles: two pairs, in 9 and 11; anterior pair commencing from ventral part of septum 9/10, extending dorsally over spermathecae of segment 9. Posterior pair commencing from septum 10/11, much smaller than anterior, extends dorsally into segment 11. Spermathecae: two pairs, in 8 and 9 ( Fig. 5 ). Duct wide, bent at midlength, extending into irregular elongate ampulla; unilobate diverticulum attached to ampulla at duct/ampulla union. Spermathecal ectal ducts enter body wall near septa 7/8 and 8/9, respectively. Iridescent sperm present in diverticula. Prostates: two pairs, each confined to one segment; in 17 and 19. Duct originates as short, thin tube, and extends in once, or twice, strongly recurved tubular prostatic gland. Penial setal retractor muscles: commence at septa 17/18 and 18/19. Penial setae: a and b alike; stem slender, slightly curved, unornamented, smooth; approx. 0.9 mm long.

Holotype: NMSA /Olig.03360. KwaZulu-Natal: Highmoor State Forest (29°18'34''S: 29°35'44''E), small montane Podocarpus forest, ca 20 cm deep under rock, 1.iii.2001, A.J. Armstrong.

Paratypes: NMSA /Olig.03807, 2 cl collected together with holotype .

Other material examined: KwaZulu-Natal: NMSA /Olig.03339, 6 cl, Blinkwater Nature Reserve (29°14'18''S: 30°27'30''E) under decomposing wood, 18.i.2001, A.J.Armstrong . NMSA /Olig.04535, 1 cl, Vernon Crookes Nature Reserve (30°15.976'S: 30°37.187'E), forested area, rocky moist soil, under large casts probably discarded by Microchaetus vernoni , and other microchaetid species, 24.i.2007, J.D. Plisko, S.W. James, G.B.P. Davies .

Discussion: This species being proandric and having nephridia with terminal vesicles agrees with the Chilota generic characters. It is similar to C. quindecimus (redescribed below) by having commencement of the intestine in segment 15 and last pair of hearts in 12, but differs in the shape of the spermathecae, and in prominent prostatic hook-like conical papillae, in which prostatic pores are located. This shape of prostatic papillae is not known in other acanthodrilines. This specific feature was observed in mature individuals, suggesting that the hooked endings of the papillae may develop with age. Biological notes and distribution: This species was collected during summer. It occurs in forest and bushes under decaying litter, in the top layer of soil. Remains of sperm, observed in male funnels and in diverticula, confirm earlier sexual activity. It is known only from KZN. The type locality is situated in the Drakensberg foothills and is a forested area with small patches of indigenous trees and grasses. Other material was collected from Blinkwater Nature Reserve, north-east of the type locality.The Blinkwater locality is a summit area of an elevated section of the escarpment overlooking the Umgeni River. The plateau is at some 1480 m above sea level, has no forest, but well-preserved montane grassland and various woody plants. In the valleys there are several pockets of indigenous bushes, and mistbelt bushes occur on the southern slopes. On the lower slopes extensive commercial plantations are found. During the summer the whole area receives much rain, and is often misty; the banks of streams are overgrown by ferns, lichens and moss. The area is also known as an important breeding site for a number of birds, including South Africa’s most endangered bird, the blue swallow ( Pooley & Player 1995).

The other collecting site is located south-east of the type locality, in the Vernon Crookes Nature Reserve, known for the occurrence of a number of Microchaetus , Geogenia , and Tritogenia species. The reserve, situated at 150–610 m above sea level, comprises diverse grasslands. Forested areas occur in valleys and ravines, embracing patches of riverine bushes. The species was found in forest in black soil overlying red, coarse soil, under large casts discarded by microchaetids Microchaetus vernoni Plisko, 1992 , Geogenia tuberosa, Plisko, 1998 , G. zaloumisi Plisko, 1992 , and G. parva Michaelsen, 1913 .

In one of the dissected specimens from the Blinkwater site, numerous parasitic nematodes were observed in some of the clitellar and postclitellar segments.

Figures

Figs 3–5. Chilota dilatus sp. n.: (3, 4) ventral area of prostatic pores with prostatic pores and papillae, holotype and specimen NMSA/Olig.04525, respectively; (5) anterior right spermatheca, holotype, 400×. Abbreviations: A – ampulla, D – duct, U – unilobate diverticulum.