Dichogaster (Diplothecodrilus) asymmetrica Csuzdi & Sherlock, 2015

Csuzdi, Cs., Sherlock, E., Kouete, M. Talla & Doherty-Bone, T. M., 2015, Four new earthworm species from the highlands of Cameroon with description of a new genus Okudrilus gen. n. (Oligochaeta: Eudrilidae & Acanthodrilidae), African Invertebrates 56 (1), pp. 25-38 : 34-35

Dichogaster (Diplothecodrilus) asymmetrica Csuzdi & Sherlock sp. n.

Figs 11–14

EtymOlOgy:The specific epithet refers tO the asymmetrical pOsitiOn Of the spermathecal duct.

Diagnosis: L: 65–70 mm, D: 2–2.5 mm. Colour slightly reddish on dorsum, pale on Ventrum. First dOrsal pOre in 5/6. Clitellum 13–20. ♀ 14 paired, between a–a. Prostatic pores 17, 19. Spermathecal pores 7/8, 8/9, spermathecae with a subdivided ampulla, and an asymmetrically attached duct. The lower ampulla part bears a unilocular diverticulum. Gizzard large in 5–6, last pair of hearts in 12. Excretory system meroic with 6 meronephridia on each side. Penial setae are of two types, larger L: 2.3 mm D: 0.006 mm, tip slightly undulated, tapering. Ornamentation scattered small teeth. Smaller seta L: 2.1 mm D: 0.006 mm, tip spoon-shaped, ornamentation minute teeth.

Description:

External characters:

Syntypes: L: 65–70 mm, D: 2–2.5 mm, the number of segments was uncountable due to the poor condition of the specimens. Colour: Alive unknown, preserved reddish on dorsum, pale on ventrum. Prostomium: Schizolobous. First dorsal pore: In 5/6. Setae: All ventral, setal arrangement on segment 14 aa:ab:bc:cd:dd=6:1:7:1:30, after clitellum not seen. Clitellum: Circular extends over segments 13–20. Male field: Oblong with prostatic pores paired on 17, 19 in the setal line a. Male pores: On 18, in the seminal groves. Female pores: Paired on 14 in between setae a–a ( Fig. 11 ). Spermathecal pores: Paired in 7/8, 8/ 9 in the setal line a.

Internal characters:

Septa : 9/10–12/13 slightly thickened. Gizzards: Large in 5 and 6. Calciferous glands: Three pairs in segment 15–17, their size slightly increasing backwards. Excretory system: Meroic, with 6 meronephridia on each side. Hearts: Paired in segments 10–12. Typhlosole: Lamellar, but due to the poor preservation of the intestine its beginning can not be determined. Sperm funnels: 10, 11. Seminal vesicles: Small in 11, 12. Prostatic glands: Two pairs in 17 and 19; those in 17 are larger, in 19 smaller. Penial setae: Of two types, the longer about 2.3 mm long and 0.006 mm wide in the middle, ectal third undulated, tip acute, ornamentation consists of small teeth ( Fig. 12 ). The smaller seta 2.1 mm long, diameter 0.006 mm in the middle, ectal third slightly undulated, tip spoonshaped, ornamentation minute teeth ( Fig. 13 ). Spermathecae: Two pairs in segment 8 and 9. The ampulla subdivided with smaller ectal and larger ental part. The duct as long as the ental ampulla part joins asymmetrically at the junction of the two ampulla parts. The ectal ampulla part bears a small unilocular diverticulum ( Fig.14 .).

Syntypes: CAMEROON: North-West Region, summit of Mt. Oku, 2867–2922 m, 15.vi.2012, T. DohertyBone ( NHM 2013.448 - 450 3 ex., HNHM AF/5574 1 ex.) .

Remarks: Dichogaster (Diplothecodrilus) asymmetrica sp. n. belongs to the bolaui species group (Csuzdi 2010) characterized by the presence of dimorph penial setae; however, it differs from all other species in this group by the asymmetric shape of the spermathecae.

Habitat as for Okudrilus monticolus . As this species is smaller and less conspicuous than O. monticolus (hence, it has a lower likelihood of collection), the authors are more uncertain as to its occurrence in other habitats on Mount Oku.

The subfamily Benhamiinae is regarded by some authors (e.g. Blakemore 2013) as belonging to the family Octochaetidae, Michaelsen 1900 . However, both morphological and molecular data show that Octochaetidae in its classical sense is polyphyletic and Benhamiinae is related to the classical Acanthodrilidae species (see Csuzdi 2010; James & Davidson 2012); therefore, we maintain Benhamiinae in Acanthodrilidae .

Figures

Figs 11–14. Dichogaster (Diplothecodrilus) asymmetrica sp. n.: (11) ventral view of the clitellar region; (12) ectal third of the larger penial seta; (13) ectal third of the smaller penial seta; (14) spermatheca. Abbreviations: Fp = female pore, Pr = prostate pore.