Dichogaster

James, Samuel W. & Gamiette, Franciane, 2016, New species of Dichogaster Beddard, 1888 (Clitellata: Benhamiidae) with additional records of earthworms from Guadeloupe (French West Indies), Zootaxa 4178 (3), pp. 391-408 : 396-397

Dichogaster sp. 1

Material examined. One adult, Savane Mulet, Basse Terre, Guadeloupe, N16°02.348', W61°39.965', 1178 m asl. In organic soil and root mats in low montane vegetation of the western slope of Soufriere volcano.

Description. Dimensions> 45 mm by 2 mm at segment x, 3 mm at xxx, 3 mm at clitellum; body cylindrical throughout, segments>101 (about 20 tail segments removed for use in DNA extractions). Setae all ventral, closely paired throughout; setal formula AA:AB:BC:CD = 3.5:1:5:1 at xxx, DD> ½ circumference, no narrowing of AA near male field. Prostomium prolobous, segments with post-setal secondary annulations in vi–xii, triannulate in xx–xlii, after that with additional post-setal annulet. Dusky gray-green pigmentation present dorsally in preclitellar segments, beige in formalin preservation. First dorsal pore 11/12, spermathecal pores in 7/8, 8/ 9 in A. Ovipores equatorial just median to A in xiv on elevated transverse oval papilla; male pores in xviii; prostatic pores and penial setae at ends of grooves in A in xvii–xix; grooves straight, surrounded by raised field with transverse bar papillae on xvii, xix, extending over BB. Clitellum xiii–xx, saddle-shaped reaching to CD, no other genital markings.

Septa not muscular, large muscle bands from posterior pharynx to body wall at level of 7/8. Alimentary canal with proventriculus in v, two long gizzards in vi, vii; esophagus valvular in xviii, intestinal origin xix; typhlosole a simple low fold originating in region 22/23; continuous lateral typhlosoles xxii–xxx, typhlosole ends beyond amputation point (more than 79 segments length). Calciferous glands reniform, paired in xv–xvii, composed of longitudinally-oriented lamellae opening to medial lumen; each gland with separate duct to esophagus; glands of 15 equal in size to those of xvi, these smaller than glands in xvii. Micronephridia 8 per segment, pre-intestinal nephridia tubular; intestinal segment nephridia closed sac-shaped with oil droplets; median rows of posterior segments with nephrostomes; no nephrostomes seen anteriorly; nephridia distributed AB-dorsum. Vascular system with ventral trunk, single dorsal trunk, latero-esophageal hearts in x–xii.

Fan-shaped ovaries composed of long strings, with funnels in xiii; paired spermathecae in viii, ix, each a pyriform ampulla with four-lobed stalked diverticulum; distal two lobes much larger than the two short bumps comprising the proximal lobes. Spermathecae consisting of short duct sharply demarcated from ovate to cordate ampulla; diverticulum from duct-ampulla junction, main portion Y-shaped but with two very small chambers on the stem of the Y. Male sexual system holandric, testes and funnels free; acinous seminal vesicles in xi, xii; tubular prostates with very short delicate ducts, sharply marked from narrow tubular glandular portion; glands in many zigzag folds within segments of origin; glands of xvii much larger; vas deferens slender, non-muscular and slightly undulating; penial setal follicles and penial setae vestigial, just median to ducts.

Remarks. This worm is sympatric with D. sp. 4 and D. musciphila and is easily distinguished from them by a combination of nephridial count, pigmentation and adult dimensions. With D. musciphila it shares having 8 nephridia per segment but not the strong red pigmentation, nor the more posterior placement of the lateral typhlosoles, and not the prostomium type, either. However the two have similar spermathecal structure, probably within the intra-specific range of variation. After finding the individual reported here we searched long to find others but failed, even as we collected many of the other species on the site.