Dichogaster (Diplothecodrilus) coeruleoviridis, Csuzdi, 2005

Csuzdi, Csaba, 2005, Earthworms (Annelida: Oligochaeta) of Sao Tomé, Journal of Natural History 39 (33), pp. 3039-3058 : 3048-3051

Dichogaster (Diplothecodrilus) coeruleoviridis sp. nov.

( Figures 12–14 )

Material examined

Holotype: AF/5004 Sao Tome´, on the volcano around Lago Amélia, 1450 m asl in fallen logs, leg. Cs. Csuzdi, 30 August 2000. Paratypes: AF/5005 six preadult ex. Locality same as that of the holotype. AF/5039 two preadult ex. Sao Tome´, Monte Cafe´, near to the waterfall, 860 m asl in fallen logs, leg. Cs. Csuzdi, 26 August 2000.

Derivatio nominis

The name of this species refers to its characteristic bluish green colour.

Diagnosis

L. 20–30 mm, D. 2–2.5 mm, number of segments 106–108. Colour dark with bluish green bands. First dorsal pore in 5/6. Clitellum 13, 14–19, 20. Prostatic pores paired on 17, 19 spermathecal pores 7/8, 8/9. Spermathecae with long duct and a subdivided ampulla. The ental part narrow, slightly bent, provided with a unilocular diverticulum, the ectal part roofshaped. Penial setae all similar, about 1.4 mm long and 0.02 mm wide, tip hooked and smooth, and under the tip the setae have a characteristic ornamentation of scattered thorns and a series of protruding dents.

External characters

Holotype: broken, its tail is missing. L. 25 mm, D. 2.5 mm. Paratypes: L. 20–30 mm, D. 2 mm, number of segments 88–103. Colour alive dark brown, with bluish green bands, preserved yellowish. Prostomium pro-epilobous. The first dorsal pore occurs in the intersegmental furrow 5/6. Setae are closely paired, all ventral, setal formula after the clitellum aa:ab:bc:cd:dd512:1.5:6.5:2:40. The clitellum extends over segments (13), 14–19 (20), provided with an almost rectangular male field. Prostatic pores paired on 17, 19 in the setal line b. Male pores externally not visible, they are on segment 18, in the seminal groves. Female pores paired on 14 anterior to setae a-a ( Figure 12 ). Two pairs of spermathecal pores are present in furrows 7/8, 8/9 near to the setae b. Porophores absent.

Internal characters

There are no septa notably strengthened. Oesophageal gizzards two, in segments 5 and 6. Three pairs of calciferous glands of about equal size, situated in segments 15–17. Excretory system meronephridial, with five meronephridia on each side of the intestine. Paired lateral hearts are present in segments 10, 11, and 12. Testes are paired in 10 and 11 enclosed into perioesophageal sperm sacs. Two pairs of small seminal vesicles present in 11 and 12, and a pair of large racemose ovaries pendent from the posterior face of the septum 12/13. Seminal duct convoluted forming a big bow in segment 15, discharging through a small thickened ectal part, as wide as the prostatic duct, in segment 18. The two pairs of prostatic glands are moderately large occupying two to three segments. Each prostate accompanied by a penial setal sac containing three to four setae of the same type. The penial setae are about 1.4 mm long and 0.02 mm wide with a somewhat hooked tip. The bent part is smooth without any sculpture, below the elbow it has a characteristic ornamentation of scattered thorns and five protruding denticles ( Figure 13 ). Two pairs of spermathecae present in segments 8 and 9. Each consists of a long duct and subdivided ampulla. The lower part of the ampulla is narrow, slightly curved and at the junction with the duct bears a small, sometimes bifurcating diverticulum ( Figure 14 ).

Remarks

The new species, regarding the shape of spermatecae, shows affinities with D. (Dt.) oxtobyae Csuzdi, 2000 but differs in the length and shape of the penial setae. It appears to be close to D. (Dt.) mundamensis ( Michaelsen, 1897) also, but differs in several characters, for example in the length, shape, and ornamentation of penial setae, and shape of the spermathecae.

The characteristic colour and the looping of the vasa defferentia in segment 15 are unique features of this species.

Figures

Figure 12. D. (Dt.) coeruleoviridis sp. nov., ventral side of the clitellum.

Figure 13. D. (Dt.) coeruleoviridis sp. nov., penial seta: (a) whole seta; (b) tip of the seta; (c) middle part of the seta with the characteristic ornamentation.

Figure 14. D. (Dt.) coeruleoviridis sp. nov., spermatheca.