Dichogaster (Diplothecodrilus) tobii, James & Divina, 2012

James, Samuel W. & Divina, Gildas Brice, 2012, Earthworms (Clitellata: Acanthodrilidae, Almidae, Eudrilidae, Glossoscolecidae, Ocnerodrilidae) of the coastal region of Gamba, Ogooué-Maritime Province, southwestern Gabon, Zootaxa 3458, pp. 133-148 : 136

Dichogaster (Diplothecodrilus) tobii sp. nov.

( Figs 1E, F, 3C)

Material. Holotype USNM 1142296 , clitellate, Gamba Complex , Gabon in leaf axils of Pandanus plants in swamp between low forested dune ridges of coastal plain at 2.80055°S, 10.04411°E, 13 m asl., 17, 18 May 2008; S. James, G. Divina, G. Moussavou and L. Tchignoumba, colls . Paratypes USNM 1142297 : two clitellates; same data as holotype . Other material: USNM 1180250 , 1180252 , same data as holotype .

Etymology. The species is named in honor of Mr. Elie Tobi, one of the research technicians at the Gabon Biodiversity Program in Vembo, Gamba.

Diagnosis. Dichogaster (Diplothecodrilus) with penial setae of one type, no ornamentation or bends until the tip, which has a half-spiral tight curve with setal tip bent back to and under the shaft, peri-esophageal testes sacs, and ten nephridia per segment.

Description. Dimensions 29–32 mm by 2.1–2.2 mm at segment X, 2.2–2.4 at clitellum, 2.1–2.2 mm at XXX; body cylindrical throughout, segments 110–118. Setae closely paired throughout; setal formula AA:AB:BC:CD = 2.5:1:3:1.5 at X, 4:1:5:1.5 at XXX, DD> 1/2 circumference throughout; AA narrower at XX, gradually widens over several segments. Prostomium epilobous closed, furrow 1/2 very faint. Pale brown pigmentation denser dorsally; darker mid-dorsal stripe along muscle band of dorsal pores. First dorsal pore 5/6, spermathecal pores minute, not seen. Ovipores paired equatorial just median to A in XIV; male pores in XVIII; prostatic pores and penial setae at ends of seminal grooves in AB in XVII–XIX. Seminal grooves slightly concave laterally. Clitellum XIII–XX, annular; no genital markings ( Fig. 1E).

Septa 4/5 slightly muscular, 5/6 not seen, 6/7–9/10 very thin, membranous; 10/11–12/13 slightly thicker. Alimentary canal with two gizzards in V, VI; separated by thin annulus; paired calciferous glands in XV–XVII, reniform with internal lamellar structure; gland of XV smaller than the equal-sized glands of XVI, XVII; glands with separate ducts to esophagus wall, but close together; esophagus valvular in XVIII, intestinal origin XIX; typhlosole originating in XXIII, height less than one fourth lumen diameter; a thick fold almost oval in cross-section XXIII–XXIX; thereafter a thin fold; lateral typhlosoles small XXV–XXX. Nephridia of anterior segments small plectonephridia, 10 per segment; in intestinal segments stomate megameronephridia 1 per side near AB, 4 sac-like meronephridia per side.

Vascular system with ventral trunk, single dorsal trunk, these connected by lateral trunks in VIII–IX, lateroesophageal hearts in X–XII. Extra-esophageal vessel not seen; supra-esophageal vessel not seen.

Ovaries, funnels free in XIII; paired spermathecae in VII, VIII, long sausage-shaped ampulla sometimes passing through septum to next segment posterior, ampulla and duct not well-differentiated, diverticulum shortly stalked, 1–3 lobed, attached near ampulla-duct junction; short muscular duct ( Fig. 1F).

Male sexual system holandric, testes, funnels topologically free in x, xi; septa 9/10/11/12 meet body wall very close together to form peri-esophageal testes sacs; seminal vesicles vestigial or undeveloped; vasa deferentia superficial, enter body wall in XVIII; tubular prostates XVII, XIX in one or two short kinks, confined to segments of origin; short slender ducts; penial setal follicles in XVII, XIX. Penial setae 0.7 mm by 10 µm in basal two thirds, tapering to 5 µm in distal third, no ornamentation or bends until the tip, which has a half-spiral tight curve with setal tip bent back to and under (or over, depending on point of view) the shaft ( Fig. 3C).

Remarks. By the location of the first dorsal pore and the spermathecal ampulla’s slight constriction into two sections, this species belongs to the subgenus Dichogaster (Diplothecodrilus) . The penial setae of D. tobii possibly correspond to those of the East African austeni species group (Czuzdi 2010), but the new species’ penial setae are much smaller than any of the afore-mentioned species group members. There are penial setal similarities to the smaller setae of D. modigliani (Rosa, 1896), but in the present case there is only one penial setal type. The new species is diagnosed by the combination of the penial setal morphology, peri-esophageal testes sacs, thick main typholosole, lateral typhlosoles present, and ten nephridia per segment.