Eremidrilus gilita, Fend & Rodriguez, 2020

Fend, Steven & Rodriguez, Pilar, 2020, New Eremidrilus species (Clitellata: Lumbriculidae) from western North America Part 1, species with two spermathecal segments, Zootaxa 4809 (1), pp. 111-131 : 121-124

Eremidrilus gilita n. sp.

( Figures 7 , 8 , 11E )

Holotype. USNM 1618768 . Dissected worm, incomplete but with sperm in spermathecae and mature egg; slidemounted in Canada balsam, stained with carmine.

Type Locality. USA, New Mexico, Catron Co., Gilita Creek at Willow Creek (Site 14, Table 1), in riffle, 22 Apr 1996, collected by S. Fend.

Paratypes. From the type locality (Site 14), same collection data; all mature: USNM 1618770 , 1 sagittally sectioned worm on 2 slides, stained with hematoxylin and eosin; USNM 1618769 , 1 dissected, incomplete. MNCN 16.3 /3115, 1 whole-mount, complete. All slide-mounted in Canada balsam .

Etymology. Named for the type locality, Gilita Creek. Noun in apposition.

Description. Length of one complete, preserved worm 17 mm, 58 segments. Diameter at clitellum 0.35–0.5 mm. Proboscis 260–480 µm long, about 85–95 µm diameter at middle ( Fig. 7A , 8A ). Secondary annulation from IV to clitellum ( Fig. 7A ). Chaetae with nodulus 0.4 to 0.5 from distal end in mid-body, but may be more distal posteriorly; length 112–133 µm, shorter in II ( Figs. 7B , 8B ). Male pores on the ventral chaetal line, midway between chaetae and posterior septum, on narrow porophores ( Figs. 7A,C , 8C,D ). Simple spermathecal pores ( Fig. 8E,F ), behind ventral chaetae, on the ventral chaetal line, the first at 1/3 the distance from posterior septum to ventral chaetae, second close to intersegment 12/13 ( Figs. 7C , 8E,H ). Female pores intersegmental at 11/12.

Epidermis 5–10 µm thick, up to 12 µm in clitellum. Clitellum X to XIII. Pharynx in II–IV, dorsal pad not prominent; pharyngeal glands in IV–VI (VII). Sperm sacs extend anteriorly to VII, posteriorly to XIII or XIV. Egg sacs to XV. Nephridia in several postclitellar segments, terminating in a round vesicle (30 µm wide), anterior to ventral chaetae ( Figs. 7C , 8G ).

Atria 240–340 µm long, entirely in X, club-shaped, maximum diameter 52–77 µm; muscle layer thin, 2–4 µm; epithelial cells cuboidal, to 6–7 µm high. Atrial ampulla covered with a prostate layer, 20–30 µm thick, prostate cells in densely packed clusters ( Figs. 7C,D , 8D ). Atrium narrows to 20 µm before porophore, and to about 10 µm near the male pore, which opens on a narrowly cylindrical porophore (26–50 µm long, 30–33 µm wide). Atrium length about 9–10 times porophore width, and 0.6–0.7 times body width. Two vasa deferentia per atrium, diameter 19–24 µm, length about 300 µm; posterior vas loops in XI, and both vasa join the atrial muscle layer near the middle, entering the lumen at about one third the distance from tip. ( Fig. 7C,D )

Spermathecae in XI and XII, ampullae may extend into next segment ( Fig. 7C ). Ampullae irregular sac-like, epithelial layer about 8 µm thick ( Fig. 8E ). Ectal ducts of spermathecae 60–90 µm long and up to 50 µm wide, usually tapered to about 20 µm near the pore; muscle layer thin (ca. 1 µm), lining cells somewhat columnar, about 12 µm high; lumen very narrow ( Fig. 8F ). Spermathecal pores without glands or distinct epidermal modifications.

Remarks. The position of the spermathecal pores in line with the ventral chaetae, with the second pair close to intersegment 12/13, is similar to that of other Eremidrilus species having two spermathecal segments. Male pores open on a short porophore, narrower than that of E. humboldti n. sp. and E. allegheniensis (see below), and markedly different in shape from the concave, annular porophore of E. artzaini (a porophore is absent in E. montanensis n. sp.). The small size of the atrium and the thin atrial musculature most closely resemble those of E. humboldti , but in that species the atrium is shorter and the porophore is relatively large (see Table 2). The nephridial vesicles, observed in middle segments, appear more distinctive than those of E. montanensis .

Figures

FIGURE 7. Eremidrilus gilita n. sp., from Gilita Creek. A. Anterior ends, external view of unmounted worms, both with pharynx partially everted. B. Chaetae; left to right: dorsal pair in IV, ventral chaeta in VI. C. Reproductive organs, segments X–XIII. D. Reproductive organs, segments IX–XI (second spermatheca was broken).

FIGURE 8. Eremidrilus gilita n. sp., from Gilita Creek. A. Anterior end of a whole-mounted worm. B. Anterior dorsal chaeta, from a whole-mount. C. Male porophore with ectal end of atrial duct, from a whole-mount. D. Atrium and porophore, from a sagittal section. E. Spermathecae from a sagittal section. F. Spermathecal duct, sagittal section. G. Nephridium; inset shows the ectal vesicle near the pore, from a whole mount. H. Surface of clitellum, with spermathecal pore in segment XI, close to intersegment 11/12. Note: specimens are facing left.

FIGURE 11. Eremidrilus species having two spermathecal segments, schematic illustration comparing position and basic morphology of reproductive organs in X–XIII.