Dichogaster (Diplothecodrilus) paulclarki, Csuzdi, 2008

Csuzdi, Csaba, 2008, Earthworms from the Kivu Region, D. R. Congo with description of two new Dichogaster Beddard, 1888 (Oligochaeta: Acanthodrilidae, Ocnerodrilidae), Journal of Natural History 42 (33 - 34), pp. 2227-2241 : 2233-2235

Dichogaster (Diplothecodrilus) paulclarki sp. nov.

( Figure 4A–D )

Material examined

Holotype. BMNH 1997.1628 D. R. Congo, Kivu Region , Bugabo, leg. Gasana N’Doli, 25 July 1973.

Paratypes. HNHM AF/3544, one exemplar , BMNH 1997.1629 , one exemplar. Locality same as that of the holotype . HNHM AF/3571, one exemplar, BMNH 1997.1593 , one exemplar. D . R. Congo, Kivu Region , River Mululu, leg. Gasana N’Doli, 15 July 1973 .

Diagnosis

Length 41–50 mm, D. 2–2.3 mm, no. of segments 95–115. Pigmentation lacking. First dorsal pore in 5/6. Clitellum 13–20. ♀ 14 paired before setae a–a. Prostatic pores 17, 19. Spermathecal pores 7/8, 8/9, spermathecae with a subdivided irregular ampoule, and an equally long duct. Gizzard in 5/6, last pair of hearts in 13. Calciferous glands in 15–17 of equal size. Excretory system meroic with four meronephridia per side.

Penial seta L. 1.7–1.8 mm, D. 0.015 mm, tip sharply pointed, ornamentation small thorns.

Derivatio nominis

The specific epithet refers to Dr Paul Clark (The Natural History Museum, London) for always being helpful throughout my stay in London.

External characters

Holotype. Length 46 mm, diameter 2 mm, no. of segments 115.

Paratypes. 41–50 mm in length, 2–2.3 mm in diameter, number of segments 95–115. Colour pale, pigmentation lacking. Prostomium schizolobous. First dorsal pore in 5/ 6. Setae all ventral, setal arrangement after the clitellum aa:ab:bc:cd:dd54:1.1:4:1:34. Clitellum extends over segments 13–20, male field oblong. Prostatic pores paired on 17, 19 in the setal line b. Male pores externally not visible, they are on 18, in the seminal groves. Female pores paired on 14 just before the setae aa. Spermathecal pores paired in 7/8, 8/9 near to the setae b. Porophores absent ( Figure 4A ).

Internal characters

The first visible septum 6/7, thickened septa lacking. Oesophageal gizzards small, in segment 5 and 6. Three pairs of calciferous glands in segment 15–17 of equal size. Excretory system meroic, with four meronephridia on each side. Paired hearts are present in segments 10–13. Typhlosole very small, begins in segment 21, auxiliary typhlosole lacking. Testes in 10 and 11 enclosed in perioesophageal testis sacs. Seminal vesicles in 11, 12, and a pair of large ovaries in segment 13. Seminal duct convoluted, discharging in segment 18. Two pairs of prostatic glands are present in 17 and 19, slightly intruding into the neighbouring segments and each with a penial setal sac containing a mature and several immature penial setae. The mature penial seta is undulated at the ectal third, about 1.7–1.8 mm long and 0.015 mm wide with a sharply pointed tip. Ornamentation consists of scattered thorns ( Figure 4B,C ). There are two pairs of spermathecae in segment 8 and 9. The ampoule is subdivided. The ental part small and turns back to the pear-shaped ectal part which bears a small rounded diverticulum. The duct is narrow and half as long as the ampoule ( Figure 4D ).

Remarks

This species belongs to the affinis species group and, by the penial setae, resembles D. (Dt.) kigogoana Stephenson, 1933 . Nevertheless it differs from the latter in the position of the last pair of hearts, in the shape of the spermathecae and in the absence of a thickened septa.

Figures

Figure 4. Dichogaster (Dt.) paulclarki sp. nov. (A) Ventral part of the clitellar region; (B) penial seta; (C) ornamentation of the penial seta; (D) spermatheca. St, spermathecal pores; Pr, prostate pores.