Dichogaster (Dichogaster) mamillata, 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 : 2558-2561

Dichogaster (Dichogaster) mamillata sp. nov.

( Figure 4A–C )

Material examined

Holotype: Centre-West Ivory Coast, Oumé (6 u 379N, 4 u 409W). Leg. J. Tondoh, August 2004. Degraded forest HNHM AF/5102 . Paratype: HNHM AF/5090, 1 ex. Locality same as that of the holotype .

Derivatio nominis

The specific epithet from the Latin mamillae 5nipples, refers to the special protuberances of the prostatic pores.

Diagnosis

L. 30–32 mm, D. 1.5 mm. No. segments 126. Pigmentation lacking. First dorsal pore in 13/ 14. Clitellum K13–19. R 14 unpaired, ventral-median. Prostatic pores 17. Spermathecal pores 8/9, spermathecae with elongate ampoule and a muscular duct containing several sperm chambers. Gizzard in 5–6, last pair of hearts in 13. Penial setae uniform, L. 1 mm, D. 0.005 mm, tip spatula-form, ornamentation scattered teeth.

External characters

Holotype: L. 30 mm, D. 1.5 mm, No. segments 126. The sole paratype: L. 32 mm, D. 1.5 mm, No. segments 126. Colour pale, pigmentation lacking. Prostomium prolobous retracted. First dorsal pore in 13/14. Setae all ventral, setal arrangement after the clitellum aa:ab:bc:cd:dd510:2:8:1.5:60. Clitellum extends over segments K13–19, with less developed ventral side. Prostatic pores on paired protruding papillae in 17 ( Figure 4A ). Male pores not visible externally, they open near to the prostatic pores. Female pores unpaired on 14 near between setae a-a. Spermathecal pores paired in 8/9 near to the setae b. Porophores absent.

Internal characters

The first septum 4/5, thickened septa lacking. Oesophageal gizzards two, in segments 5 and 6. Three pairs of calciferous glands located in segments 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 strong, begins in segment 21.

Testes are free in 10 and 11. Seminal vesicles small in 11, 12, and ovary in segment 13. Seminal duct apparent highly convoluted, discharging in segment 17. A pair of small prostatic glands are present in 17, confined to their own segment, each with a penial setal sack containing one mature and one juvenile seta. The mature seta is about 1 mm long and 0.005 mm wide with spatula-like tip. The ectal third is undulated and ornamented with scattered teeth ( Figure 4C ). One pair of spermathecae in segment 9. The ampoule is elongated sac-like and as long as the muscular duct. In the wall of the duct there are several somewhat protruding seminal chambers ( Figure 4B ).

Remarks

This species belongs to the penigera group. In this group there are three species with microscolecin reduction of male apparatus; D. (D.) lofaensis Michaelsen, 1914 described from Liberia, D. (D.) hammon Somon, 1995 described from Guinea, and D. (D.) nematochaeta Omodeo, 1958 occurs in Guinea / Ivory Coast. D. (D) mamillata sp. nov. differs from D. (D.) lofaensis in the number of meronephridia, in its size and in the presence of penial setae. It differs from D. (D.) hammon in size (30 mm versus 300 mm) and in the position of the last hearts, and finally it differs from D. (D). nematochaeta in the position of the last hearts and also in the size and structure of penial setae (which are of two types in D. (D.) nematochaeta ).

Dichogaster (Dichogaster) terraenigrae Omodeo and Vaillaud, 1967

Dichogaster terrae-nigrae Omodeo and Vaillaud 1967, p 934 . Benhamia terraenigrae: Csuzdi and Zicsi 1994, p 218 . Dichogaster (Dichogaster) terraenigrae: Csuzdi 1995, p 109 ; Csuzdi 2000, p 56.

Material examined

Centre-West Ivory Coast, Oumé (6 u 379N, 4 u 409W). Leg. J. Tondoh, August 2004. Degraded forest HNHM AF/5078, 1 ex. , Fallow AF/5079, 1 ex., AF/5088, 1 ex., Cocoa Plantation AF/5080, 1 ex., Multispecies wood plantation AF/5081, 1 ex., AF/5084, 2 ex., AF/5087, 1 ex., Teak plantation AF/5083, 1 ex., Mixed crop field AF/5086, 1 ex.

Diagnosis

L. 160–175 mm, D. 4–5 mm. No. segments 305–320. Segments 1–2 simple, 3–12 tri- or multiannulate. Pigmentation lacking. First dorsal pore in 12/13. Clitellum K13–19. R 14 unpaired, ventral-median. Prostatic pores 17, 19. Spermathecal pores 7/8, 8/9, spermathecae with elongated ampoule and longer duct. Diverticulum multilobed berryshaped. Gizzard in 5–6, last pair of hearts in 12. Calciferous glands large in 15, 17 vestigial in 16. Excretory system meroic with ca 10 pairs of meronephridia. Penial setae uniform, L. 2.6– 3 mm, D. 0.0012 mm. Tip rounded, ornamentation lacking. Transverse pad-like genital papillae in segments 9, 10, 15, 19–23.

Remarks

Due to the presence of triannulate segments and pad-like genital papillae, D. (D.) terraenigrae greatly resembles the species of the genus Millsonia externally, but the presence of penial setae and the lack of intestinal caeca obviously place it in Dichogaster . However, the reduction of the calciferous glands in segment 16 requires further consideration regarding its taxonomic status.

Genus Dichogaster (Diplothecodrilus) Csuzdi, 1996

Dichogaster (Diplothecodrilus) Csuzdi 1996, p 355 ; Csuzdi 2000, p 58. Dichogaster (Diplothecodrilus) : Blakemore 2005, p 5.

Dichogaster (Diplothecodrilus) saliens (Beddard, 1893)

Microdrilus saliens Beddard 1893a, p 683 . Dichogaster crawi Eisen 1900, p 228 .

Dichogaster saliens: Michaelsen 1900, p 346 ; Stephenson 1931, p 65; Wasawo and Omodeo 1963, p 211; Gates 1972, p 281; Omodeo 1973, p 25; Blakemore 2002, p 114.

Dichogaster hatomaana Ohfuchi 1957, p 259 .

Dichogaster (Diplothecodrilus) saliens: Csuzdi 1995, p 114 ; Csuzdi 1996, p 358.

Material examined

Centre-West Ivory Coast, Oumé (6 u 379N, 4 u 409W). Leg. J. Tondoh, August 2004. Degraded forest HNHM AF/5091, 2 ex.

Remarks

This is one of the most widely distributed peregrine Dichogaster species occurring in all tropical regions. It is easy to identify by the spectacle-like prostate pores on segment 17 and the presence of two pairs of spermathecae (incomplete microscolecine reduction).

Genus Millsonia Beddard, 1894

Millsonia Beddard 1894, p 380 . Dichogaster: Michaelsen 1900, p 334 (part). Dichogaster: Stephenson 1930, p 851 (part). Millsonia: Omodeo 1955a, p 218 (part); Omodeo 1958, p 59 (part). Millsonia: Sims 1986, p 277 (part). Millsonia: Csuzdi 1996, p 360 (part); Csuzdi 2006, p 36.

Millsonia lamtoiana Omodeo and Vaillaud, 1967

Millsonia lamtoiana Omodeo and Vaillaud 1967, p 932 . Millsonia lamtoiana: Sims 1986, p 297 . Millsonia lamtoiana: Csuzdi 1996, p 361 ; Csuzdi 2000, p 75; Csuzdi 2006, p 39.

Material examined

Centre-West Ivory Coast, Oumé (6 u 379N, 4 u 409W). Leg. J. Tondoh, August 2004. Multispecies wood plantation HNHM AF/5089, 2 ex.

Diagnosis

L. 300–415 mm, D. 7–9 mm. No. segments 300–570. Pigmentation dark brown. First dorsal pore in 5/6. Clitellum 13–20. R 14 paired. Prostatic pores 17, 19. Spermathecal pores 7/8, 8/9, spermathecae turned pear-shaped, duct large, spherical, its wall contains sperm chambers. Gizzards 5–6, last pair of hearts in 12. Calciferous glands in 15–17. Intestinal caeca 19–24 pairs in 28–46, 52. Excretory system meroic, with 15 pairs of meronephridia.

Figures

Figure 4. Dichogaster (D.) mamillata sp. nov. (A) Ventral part of the clitellar region; (B) spermatheca; (C) penial seta.