Dichogaster (Dichogaster) gambaensis, 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 : 140-141

Dichogaster (Dichogaster) gambaensis sp. nov.

( Figs 2C–E, 3E)

Material. Holotype USNM 1142290 , clitellate, Ivinga , Gamba Complex, Gabon in forested flat on coastal plain at 2.78957°S, 10.04805°E, 15 m asl., 17 May 2008; S. James, G. Divina, G. Moussavou and L. Tchignoumba, colls . Paratypes USNM 1142291 , 5 clitellates, same data as holotype . Other material: USNM 1180242 , clitellate, interior coastal plain forest near Vembo , Gamba Complex, Gabon, 2.74693°S, 10.00476°E, 5 m asl., 18 May 2008 ; S. James, G. Divina, G. Moussavou and L. Tchignoumba, colls. USNM 1180243 , clitellate, interior coastal plain forest near Vembo , Gamba Complex, Gabon, 2.73829°S, 10.00643°E, 14 m asl., 18 May 2008 ; S. James, G. Divina, G. Moussavou and L. Tchignoumba, colls.

Etymology. The species is named after the area in southwest Gabon called Gamba. This species seems to be rather widespread in the Gamba area, particularly in forest patches on sandy soils.

Diagnosis. Dichogaster (Dichogaster) with male pores medial to, not in, the seminal grooves, spermathecae in VI and VII with pores in 7/8/9, microscolecine reduction, complex typhlosole with paired vertical flaps, and the undulating ectal section of the penial setae, terminating in a 90° bend.

Description. Dimensions 150–165 mm by 5.0–6.0 mm at segment X, 5.5–6.5 mm at clitellum, 4.8–6.0 mm at XXX; body cylindrical throughout, segments 230–275. Setae closely paired throughout; setal formula AA:AB:BC:CD = 2.5:1:4:1.2 at X, 4:1:4.5:1 at XXX, DD> 1/2 circumference throughout. Prostomium proepilobous, peristomium with many furrows. Secondary annulations post-setal VII-X; pre-, post-setal XI, XII, and from XXIV. Dusky gray-brown pigmentation denser dorsally. First dorsal pore 12/13, spermathecal pores near mid-ventral paired 7/8/ 9 in A lines. Single mid-ventral ovipore equatorial on oval papilla spanning BB in XIV; male pores in XVIII near mid-ventral just median to A, median to seminal grooves; prostatic pores and penial setae on elevated papillae at anterior end of seminal grooves in AB in XVII–1/2 XVIII; grooves run downhill posteriorly to terminate near equator of XVIII, meeting transverse furrow. Clitellum XIII–XXIII, saddle-shaped reaching to B. Large midventral crescentic genital marking concave posteriorly in XVI, broad genital midventral marking with elevated transverse ridge bearing prostatic pores in XVII, genital marking midventral trapezoidal or crescentic concave anteriorly in XIX; indistinct midventral epidermal thickenings in BB of XV, XX, XXI ( Fig. 2C).

Septa 5/6–8/9 very thin, membranous, offset back two segments; 9/10 slightly thickened, 10/11–13/14 muscular; 9/10/11/12 meet close together on body wall; 9/10 reduced to covering of hearts, testes of X. Alimentary canal with two gizzards in V, VI; separated by thin annulus; paired calciferous glands in XV–XVII, reniform, outer margins indented to make 6–8 lobes per gland; gland of XV smaller than roughly equal-sized glands of XVI, XVII; with internal lamellar structure; glands with separate ducts to esophagus wall, but very close together; esophagus valvular in XVIII, intestinal origin XIX; typhlosole originating in XXIII with densely packed paired vertical flaps about 3 or 4 pairs per segment ( Fig. 2E), height less than one third lumen diameter, vertical flaps less dense by L, fade out entirely by LXX, thereafter typhlosole a simple fold ending near CXXX. Lateral typhlosoles large, convoluted XXIII–XXXIX, XL. Nephridia small plectonephridia to XIV, 20–22 per segment; in intestinal segments stomate megameronephridia 1 per side near AB, 10 sac-like meronephridia per side from B to above D. In intestinal segments separate from nephridia are 12–14 small sub-peritoneal, post-septal bodies of fine tubules connected to small pre-septal knobs; each body of tubules connected to the others of a side by small tubule.

Vascular system with ventral trunk, single dorsal trunk, these connected by lateral trunks in VIII–IX, laterals of V–VII to gizzards; latero-esophageal hearts in X–XII. Extra-esophageal vessels to dorsal esophageal wall at 8/9; supra-esophageal vessel X–XII; clitellar vessel from esophageal wall in XIII to body wall of XIV–XX.

Ovaries, funnels free in XIII; paired spermathecae in VI, VII by septa but with ducts to 7/8/9, ampulla globular to cordate, duct narrow, diverticulum sessile or shortly stalked at center of duct, chamber multilocular; anterior spermathecal pair smaller than posterior ( Fig. 2D).

Male sexual system holandric, testes, funnels topologically free in X,XI but in peri-esophageal sacs formed by near-fusion of septa 9/10/11/12 at body wall and/or in subesophageal pockets of 9/10, 10/11; very small acinous seminal vesicles in XI, XII; vasa deferentia superficial, united from XII, muscular from XIV, enter body wall in XVIII; very long tightly coiled/kinked tubular prostates confined to XVII with septum 17/18 making a pouch holding much of the prostate gland; long slender muscular ducts rising vertically to near dorsum; penial setal follicles joined to body wall by long dorsal muscle band reaching to halfway between mid-lateral and mid-dorsal. Penial setae 1.0– 1.3 mm by 13 µm in basal two thirds, tapering to 5 µm in distal third, in which the unornamented seta has 8 complete undulations of low amplitude, finally tapering to a very fine point bent 90° from main axis ( Fig. 3E).

Remarks. This species with first dorsal pore in 12/13 and simple spermathecal ampullae clearly falls in D. ( Dichogaster ) according to Csuzdi (1996b), and further has a spermathecal morphology placing it in the damonis - group of that subgenus. Within that species-group it is the only one with male pores medial to, not in, the seminal grooves, spermathecae in VI and VII with pores in 7/8/9, incomplete microscolecine reduction, complex typhlosole with paired vertical flaps, and the undulating ectal section of the penial setae, terminating in a 90° bend. Penial setal ornamentation is confined to a few small scars along the tapering portion of the shaft, as in D. alonsoi .