Dichogaster (Diplothecodrilus) alonsoi, 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 : 138-140

Dichogaster (Diplothecodrilus) alonsoi sp. nov.

( Figs 2A, B, 3D)

Material. Holotype USNM 1142289 , clitellate, Falaise de Véra , Gamba Complex, Gabon on forested hillside at 2.84873°S, 10.23569°E, 22 m asl., 16 May 2008; S. James, G. Divina, G. Moussavou and L. Tchignoumba, colls . Other material: USNM 1180244 , same data as holotype .

Etymology. The species is named after Dr. Alfonso Alonso of the Smithsonian Institution’s Center for Conservation Education and Sustainability, who coordinated the collecting expedition to Gamba.

Diagnosis. Dichogaster (Diplothecodrilus) with penial setae of one type, the distal third of which has 2 complete undulations of low amplitude, finally tapering to a very fine point bent 90° from main axis; lacking lateral typhlosoles, free testes, simple spermathecal ampulla, and 8 nephridia per segment.

Description. Dimensions 32, 33 mm by 1.8–2.0 mm at segment X, 2.3–2.4 at clitellum, 1.7–2.2 mm at XXX; body cylindrical throughout, segments 111, 116. Setae closely paired throughout; setal formula AA:AB:BC:CD = 4:1:4:1 at X, 5:1:5:1 at XXX, DD> 1/2 circumference throughout. Prostomium proepilobous with faint single middorsal furrow not quite reaching 1/2, no secondary annulation. Pale red-brown pigmentation denser dorsally; most obvious on peritoneum; scattered dark rose pigment dots concentrated near segmental equators. First dorsal pore 5/ 6, spermathecal pores paired 7/8/ 9 in AB. Ovipores nearly 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 convex laterally, ends bent 90° medially to prostatic pores; lateral walls of grooves elevated. Clitellum XIII–XIX, saddleshaped reaching to B in XVII–XIX, annular in XIII–XVI; no genital markings ( Fig. 2A).

Septa 5/6–8/9 very thin, membranous; 9/10–12/13 slightly muscular. Alimentary canal with two gizzards in V, VI; separated by thin annulus; paired calciferous glands in XV–XVII, reniform with internal lamellar structure; gland sizes XV<XVI<XVII; glands with separate ducts to esophagus wall, but close together; esophagus valvular in XVIII, intestinal origin XIX; typhlosole a thick undulating fold originating in XXIII, height less than one fourth lumen diameter, ending in neighborhood of LXXX. No lateral typhlosoles. Nephridia of anterior segments small plectonephridia, 8 per segment; in intestinal segments stomate megameronephridia 1 per side near AB, 3 sac-like meronephridia per side from B to above D.

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

Ovaries, funnels free in XIII; paired spermathecae in VIII, IX, each a tongue-shaped ampulla, bilobed shortly stalked iridescent diverticulum attached near ampulla-duct junction; short muscular duct ( Fig. 2B).

Male sexual system holandric, testes, funnels free in X, XI; seminal vesicles in XII (one specimen) or lacking; vasa deferentia superficial, muscular, enter body wall in XVIII; tubular prostates XVII, XIX in one or two short kinks, confined to segments of origin; long slender muscular ducts; penial setal follicles joined to body wall by long dorsal muscle band reaching to halfway between mid-lateral and mid-dorsal. Penial setae 0.95 mm by 8 µm in basal two thirds, tapering to 3 µm in distal third, in which the seta has 2 complete undulations of low amplitude, finally tapering to a very fine point bent 90° from main axis, ornamentation lacking ( Fig. 3D) .

Remarks. By the location of the first dorsal pore, this species belongs to subgenus Dichogaster (Diplothecodrilus) . However the spermathecae do not have the characteristic two-chambered ampulla, but rather a simple ampulla with a short muscular duct. The penial setae are almost entirely smooth, having only a few slight scales or scars along the shafts, in the manner found in most penial setae in the genus and in Acanthodrilidae , regardless of the presence of distinctive ornamentation. We consider this type of scales to be a result of the tapering of the setae, where constituent fibers terminate leaving a small zig-zag scar on the surface. The penial setae of D. alonsoi do not correspond to any of the D. (Diplothecodrilus) species groups, but instead has penial setae very much like four other morphotypes collected at Gamba, including the next new species, D. (Diplothecodrilus) gambaensis and three taxa for which material was insufficient for new species description. The penial setal morphology, consisting of a long smooth main shaft with an undulating ectal section and a fine tip bent sharply to make a hook, is present in several other species spread over two subgenera, and is probably not a reliable indicator of phylogeny. This will be discussed in detail after the partial descriptions of additional Dichogaster morphotypes. Dichogaster (Diplothecodrilus) alonsoi is diagnosed by the combination of the penial setal morphology, absence of lateral typhlosoles, free testes, and 8 nephridia per segment.