Dichogaster ( Diplothecodrilus ) alonsoi, James & Divina, 2012

Dichogaster ( Diplothecodrilus) alonsoi sp. nov.

( Figs 2A, B, 3D)

Material. Holotype USNM 1142289 About USNM , 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 GoogleMaps . Other material: USNM 1180244 About USNM , same data as holotype GoogleMaps .

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.