Dichogaster (Diplothecodrilus)

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 : 398

Dichogaster (Diplothecodrilus) sp. 3

Material examined. One clitellate adult, Montane forest on Mamelle Petit Bourg , in epiphytic bromeliad leaf axils, Petit Bourg, Basse Terre, Guadeloupe N16°10.670', W61°43.824', 582 m asl.

Other material. Several individuals retained in culture experiments, one for DNA.

Description. 97 x 3 mm at xxx (fixed in relaxed state), 114 segments. Setae all ventral, closely paired throughout, setal formula AA:AB:BC:CD = 3:1:3:1 at xxx; DD> ½ circumference. Prostomium epilobous, brown to red-brown dorsal pigmentation. First dorsal pore 5/6, spermathecal pores in 7/8, 8/ 9 in AB. Ovipores equatorial just median to A in xiv on oval papilla; male pores in xviii; prostatic pores and penial setae on papillae at ends of grooves in A in xvii–xix; grooves straight. Clitellum xiii–xx, annular xiii–xix, no other genital markings.

Septa 8/9–12/13 slightly muscular, 9/10/11 /12 closely set together at body wall. Alimentary canal with proventriculus in v, two gizzards in vi, vii; esophagus valvular in xviii, intestinal origin xix; typhlosole xxii–xliii, thick with vertical corrugations xxvi–xxxii, 0.5 lumen diameter; continuous lateral typhlosoles xxvi–xxxi. Calciferous glands reniform, paired in xv–xvii, xv<<xvi<xvii, ducts separate. Micronephridia 10–12 per segment in preintestinal segments, 8 from xxii onwards, pre-intestinal nephridia tubular; intestinal segment nephridia closed sac-shaped heavily mantled and with oil droplets. Vascular system with ventral trunk, single dorsal trunk, lateroesophageal hearts in x–xii.

Fan-shaped ovaries composed of long strings, with funnels in xiii, ovisacs (?) in xiv; paired spermathecae in viii, ix, reduced to undifferentiated main axis with slight bulge for ampulla, sessile spherical diverticulum. Male sexual system reduced, testes and funnels not seen; lacking seminal vesicles; tubular prostates small in xvii, xix; penial setae vestigial.

Remarks. Unusually among Neotropical dichogastrine earthworms this has the first dorsal pore in 5/6 rather than the common location in or near 11/12 or 12/13. This might not be homologous to the African species, but an independent shift forwards. The worm is similar to D. caraibensis with respect to the reduced spermathecal structure but the similarities end there. By pigmentation and number of nephridia in the intestinal segments it appears close to D. musciphila and D. matoubensis but the lack of male function with associated reductions of other sexual characters present large differences. Perhaps the annular clitellum indicates an affinity with D. musciphila , but D. sp. 3 differs from this species by having a larger, later-originating typhlosole which also ends 20 segments more anteriorly, as well as more nephridia in the anterior segments.