Dichogaster (Diplothecodrilus) gasanai, 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 : 2231-2233

Dichogaster (Diplothecodrilus) gasanai sp. nov.

( Figure 3A–D )

Material examined

Holotype. BMNH 1997.1561 . D. R. Congo, Kivu Region , Butembo, in stems of banana trees, leg. Gasana N’Doli, 15 July 1973.

Paratypes. HNHM AF/3564, one exemplar , BMNH 1997.1562 , one exemplar. Locality same as that of the Holotype. HNHM AF/3561, ten exemplars, BMNH 1997.1618 – 1629 , 12 exemplars D. R. Congo, Kivu Region , Bugabo, leg. Gasana N’Doli, 25 July 1973. HNHM AF/3550, four exemplars, BMNH 1997.1607 – 1616 , ten exemplars D. R. Congo, Kivu Region , between Kagundu and Gitovu, leg. Gasana N’Doli, 17 July 1973. HNHM AF/3551, four exemplars, BMNH 1997.1574 – 1582 , nine exemplars. D. R. Congo, Kivu Region , River Mululu, leg. Gasana N’Doli, 15. July 1973. HNHM AF/3557, two exemplars, BMNH 1997.1479 – 1484 , six exemplars. D. R. Congo, Kivu Region, Mewa, leg. Gasana N’Doli, 17 July 1973 .

Derivatio nominis

The specific epithet is referring to the collector of this interesting material:Gasana N’Doli.

Diagnosis

Length 32–56 mm, D. 1.8–2 mm, no. of segments 75–112. Pigmentation lacking. First dorsal pore in 5/6. Clitellum 12– K 21. ♀ 14 paired between setae a–a. Prostatic pores 17, 19. Spermathecal pores 7/8, 8/9, spermathecae with elongated ampoule, and a shorter duct, half as long as the ampoule. Gizzard in 5/6, last pair of hearts in 13. Calciferous glands in 15–17, with slightly backwards increasing size. Excretory system meroic with four meronephridia per side. Penial seta L. 1.3–1.4 mm, D. 0.006 mm, tip sharply pointed, ornamentation small teeth.

External characters

Holotype. Length 48 mm, D. 2 mm, number of segments 96.

Paratypes. 32–56 mm in length, 1.8–2 mm in diameter, number of segments 75–112. Colour pale, pigmentation lacking. Prostomium schizolobous. First dorsal pore in 5/6. Setae all ventral, setal arrangement after the clitellum aa:ab:bc:cd: dd52.5:1.25:3.75:1:25. Clitellum extends over segments 12– K 21, with a butterfly-shaped male field. Prostatic pores paired on 17, 19 in the setal line b. Male pores externally not visible, they are on 18, in the seminal grooves. Female pores paired on 14 between setae a–a. Spermathecal pores paired in 7/8, 8/9 near to the setae b. Porophores absent ( Figure 3A ).

Internal characters

The first visible septum 6/7, thickened septa lacking. Oesophageal gizzards small, in segment 5 and 6. Three pairs of calciferous glands located in segment 15–17, their size slightly increasing backwards. Excretory system meroic, with four meronephridia on each side. Paired hearts are present in segments 10–13. Typhlosole small, begins in segment 20 and accompanied by a pair of auxiliary typhlosoles between segments 27 and 33. 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 on the neighbouring segments and each with a penial setal sac containing a mature and several immature penial setae. The mature penial seta is somewhat undulated, about 1.4–1.5 mm long and 0.006 mm wide with a slightly hooked tip. Ornamentation consists of scattered small teeth ( Figure 3B,C ). There are two pairs of spermathecae in segment 8 and 9. The ampoule is elongated dumb-bell-shaped and on its basis bears a small rounded diverticulum. The duct is narrow and half as long as the ampoule ( Figure 3D ).

Remarks

This species belongs to the affinis species group and, by the penial setae, resembles D. (Dt.) crateris Michaelsen, 1912 . Nevertheless it differs from the latter (and from all other member of the affinis group) in the more backward location of the last pair of hearts, in the position of the clitellum and in the shape of the spermathecae.

Figures

Figure 3. Dichogaster (Dt.) gasanai 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.