Dichogaster (Dichogaster) eburnea, Csuzdi & Tondoh, 2007

Csuzdi, Csaba & Tondoh, Jerôme Ebagnerin, 2007, New and little-known earthworm species from the Ivory Coast (Oligochaeta: Acanthodrilidae: Benhamiinae and Eudrilidae), Journal of Natural History 41 (41 - 44), pp. 2551-2567 : 2555-2558

Dichogaster (Dichogaster) eburnea sp. nov.

( Figure 2A–D )

Material examined

Holotype: Centre-West Ivory Coast, Oumé (6 u 379N, 4 u 409W). Leg. J. Tondoh, August 2004. Teak plantation HNHM AF/5101 . Paratype: HNHM AF/5130, 1 ex. Locality same as that of the holotype .

Derivatio nominis

The specific epithet is from the Latin eburneus 5 ivory, referring to the country.

Diagnosis

L. 22–25 mm, D. 0.7 mm. No. segments 82–114. Pigmentation lacking. First dorsal pore in 13/14. Clitellum K13–K20. R 14 unpaired, ventral-median. Prostatic pores 17, 19. Spermathecal pores 7/8, 8/9, spermathecae with T-shaped ampoule, with a short duct. The pseudo-diverticulum slim, half as long as the ampoule. Gizzard in 5–6, last pair of hearts in 13. Penial setae are of two types, larger L. 0.35 mm, D. 0.005 mm, tip sharply pointed, ornamentation strong teeth. Smaller L. 0.3 mm, D. 0.005 mm, tip rounded, ornamentation almost lacking.

External characters

Holotype: L. 25 mm, D. 0.7 mm, No. segments 114. The sole paratype: L. 22 mm, D. 0.7 mm, No. segments 82. Colour pale, pigmentation lacking. Prostomium pro-epilobous retracted. First dorsal pore in 13/14. Setae all ventral, setal arrangement after the clitellum aa:ab:bc:cd:dd59:1.5:7:1:50. Clitellum extends over segments K13–K20, with a barrelshaped 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 groves. Female pores unpaired on 14 near between setae a-a ( Figure 2A ). Spermathecal pores paired in 7/8, 8/9 near to the setae b. Porophores absent.

Internal characters

The first septum 6/7, thickened septa lacking. Oesophageal gizzards two, in segments 5 and 6. Three pairs of calciferous glands located in segments 15–17, their size increasing backwards. Excretory system meroic, with three meronephridia on each side. Paired hearts are present in segments 10–13. Typhlosole strong, begins in segment 20.

Testes are free in 10 and 11. Seminal vesicles small in 11, 12, and ovary in segment 13. Seminal duct convoluted, discharging in segment 18. Two pairs of small prostatic glands are present in 17 and 19, confined into their own segment and each provided with a penial setal sack containing two different types of penial setae. The larger one is about 0.35 mm long and 0.005 mm wide with a sharply pointed tip ( Figure 2C ). Ornamentation consists of strong scattered teeth. The smaller one is almost smooth, about 0.3 mm long and 0.005 mm wide with rounded tip ( Figure 2D ). There are two pairs of T-shaped spermathecae in segment 8 and 9. The ampoule is folded back and bears a small finger-like pseudodiverticulum. The duct is small and joins to the ampoule at right-angles ( Figure 2B ).

Remarks

This species belongs to the cyrtochaeta species group and resembles D. (D.) sexdecim and D. (D.) septemdecim which also have two types of penial setae. Nevertheless it differs from both in the ornamentation of the penial setae as well as in the more backward location of the last pair of hearts.

Dichogaster (Dichogaster) ehrhardti ( Michaelsen, 1898)

( Figure 3A–C )

Balanta ehrhardti Michaelsen 1898, p 165 . Dichogaster ehrhardti: Michaelsen 1900, p 356 ; Sims 1967, p 25. Dichogaster ehrhardti var. linnelli Michaelsen 1910, p 113 . Dichogaster linnelli: Omodeo and Vaillaud 1967, p 938 .

Dichogaster pascuali Somon 1995 syn. nov.

Dichogaster (Dichogaster) ehrhardti: Csuzdi 1995, p 111 ; Csuzdi 1996, p 355; Csuzdi 2000, p 55.

Material examined

Centre-West Ivory Coast, Oumé (6 u 379N, 4 u 409W). Leg. J. Tondoh, August 2004. Mixed crop field HNHM AF/5092, 1 ex. , AF/5097, 1 ex.

Diagnosis

L. 35–110 mm, D. 2–4 mm. No. segments 78–160. Pigmentation lacking. First dorsal pore in 13/14. Clitellum 13–20. R 14 unpaired, ventral-median. Prostatic pores 19. Spermathecal pores 7/8, spermathecae with egg-shaped ampoule and a racemose diverticulum. Gizzard in 5–6, last pair of hearts in 12. Penial setae uniform, L. 2 mm, D. 0.02 mm, tip spatula-like, ornamentation serrulate.

Remarks

This is the most widely distributed West African Dichogaster species. The description of D. pascuali Somon, 1995 completely fits with D. (D.) ehrhardti . It is especially obvious if we look at the figures of penial setae ( Somon 1995, p 51, Figure 2e ). Therefore D. pascuali must be regarded as a synonym of D. (D.) ehrhardti .

Figures

Figure 2. Dichogaster (D.) eburnea sp. nov. (A) Ventral part of the clitellar region (f, female pore; p, prostate pores); (B) spermatheca; (C) larger penial seta; (D) smaller penial seta.

Figure 3. Dichogaster (D.) ehrhardti. (A) Ventral part of the clitellar region (f, female pore; p, prostate pores); (B) spermatheca; (C) penial seta.