Eclipidrilus breviatriatus Fend & Lenat, 2012, n. sp.
Creators: name: Fend, Steven V.
name: Lenat, David R.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Oligochaeta
Lumbriculida
Lumbriculidae
Eclipidrilus
Eclipidrilus breviatriatus

description: Eclipidrilus breviatriatus n. sp.
(Figures 1–2)
Holotype: USNM 1156956. A whole, slide-mounted worm in Canada balsam.
Type locality: North Carolina, Richmond Co., unnamed tributary to Naked Creek, at Forest Service road upstream of SR 1003, 28 January 2009. Collected by D.R. Lenat.
Paratypes: From the type locality. USNM 1156957-59: 18 March 2010, 1 whole mount. 25 March 2010, 1 sagittally sectioned, 1 dissected and slide mounted. Collected by D.R. Lenat.
Etymology: named for the very short atrial ducts (brevis, L.—short), compared to other Eclipidrilus species.
Other material: North Carolina, Carteret Co., Pettiford Creek at Millis Road, 1 March 2004, 1 dissected. 22 April 2008, 2 whole mounts. 29 September 2009, 2 whole mounts. Hoke Co., Flat Creek at Manchester Road, 25 January 2010, 3 whole mounts. 18 February 2010, 1 whole mount. 25 March 2010, 1 whole mount. Richmond Co., unnamed tributary to Naked Creek at Forest Service road upstream of SR 1003, 10 March 2010, 1 whole mount. 25 March 2010, 1 whole mount, 1 sagittally sectioned. All collected by D.R. Lenat.
Description. Small worms, length (preserved) 9–15 mm, 65–74 segments; width 0.42–0.55 mm in X, maximum width to 0.55 mm. Segmentation distinct in external view, but usually obscured in clitellum; secondary segmentation weak, usually visible as a narrow anterior ring in X or IX–X, then in a few post-clitellar segments (Fig. 1 A–B). Clitellum prominent in X–XII. Chaetae sigmoid, simple-pointed, with nodulus 29–40 % of chaeta length from tip (Fig. 1 C–D). Chaeta length 86–127 μm; length and proportions similar in anterior and posterior segments. Dorsal and ventral chaetae approximately equal in length; within each bundle, the outer (more lateral) chaeta may be slightly shorter than the inner. Prostomium rounded or conical, usually shorter than wide, length about 0.18– 0.22 mm; prolobous.
Brain in the peristomium, strongly lobed. Pharynx in II–IV; dorsal wall with columnar, ciliated cells; ventral wall very thin, with cuboidal, non-ciliated cells. Pharyngeal glands extensive in V–VII or VIII. Longitudinal muscle layer 20–36 μm thick in preclitellar segments; circular muscle layer 5–7 μm. Septum 1/2 inconspicuous; 2/3 and 3/4 thin; septa thick (about 5 μm) and distinct in other segments. Epidermis 10–15 μm thick anterior to clitellum; to about 25–36 μm in clitellum; to 30 μm in prostomium. No lateral blood vessels in middle or posterior segments. Chloragogen cells begin in VII or VIII. First nephridia usually paired on 6/7, the next usually on 12/13; nephridia in few posterior segments, paired or on one side only. Each nephridium has a small anteseptal funnel and a granular, ovate postseptal thickening 50–90 μm long; the posterior duct forms a loop that extends ventrally, entering one or more posterior segments, and terminating in a short ectal duct in the originating segment. Nephropores anterior to ventral chaetae simple, inconspicuous; ectal ducts may be slightly expanded near pores, but without distinct vesicles.
Spermathecae paired in IX; pores inconspicuous, on ventral chaetal lines, just behind the ventral chaetae (1/3– 1/2 the distance to posterior septum); pores may be surrounded by a 50–60 μm ring of slightly thickened epidermis; distinct accessory glands absent (Fig. 2 B, D). Spermathecae have a cylindrical ectal duct, usually slightly inflated at the ectal end; ental end well differentiated from the ovate ampulla (Fig. 1 E–F, 2A–B). Ectal duct 80–110 μm long, 22–30 μm wide, with columnar epithelium, and a narrow (about 5 μm) lumen; may be surrounded by a thin (12–15 μm) layer of glandular cells near the pore. Ectal end of duct rounded, or terminating in a small, conical papilla within a shallow sac (Fig. 2 B, D). Spermathecal ampullae entirely in IX; ovate and compact, 90–200 μm long by 60–140 μm wide, sometimes with the ental end narrowed (Fig. 1 F). Ampullar epithelium thin (2–4 μm) in the ectal 1/3, but entally becomes thicker (to 36 μm) with large, irregular cells (Figs. 1 E, 2C). In mated specimens the sperm is in a loose bundle (Fig. 2 A–C).
Testes small in IX and X, extending at most to mid-segment. Ovaries paired in XI; usually extending through XI, often into XII. Sperm sacs extend back as far as XIV; egg sacs may extend to XVI. Female funnels up to 90– 140 μm tall, with the posterior side longer than the anterior; female pores intersegmental, on 11/12.
Male funnels paired on 9/10 and 10/11; anterior and posterior similar in size (height 40–70 μm), directed anteriad within IX and X, or the posterior may be directed back within the sperm sac. Both anterior and posterior male funnels simple, conical; functional, with associated sperm. Both anterior and posterior vasa deferentia up to 10 μm wide near the funnels, narrowing to 7–8 μm near the atria. Vasa deferentia join the atria near the base (ectal end) of the ampulla, then travel diagonally through the atrial muscle layers to join the lumen near the ental end (Fig. 2 H–I). Posterior vasa deferentia enter X directly, without penetrating 10/11.
Male pores paired, in X, on the ventral chaetal line near 10/11 (Fig. 1 B, E); may be visible as shallow pits 30– 50 μm across, but in contracted worms the pores appear as transverse grooves. The short (15–20 μm), broadly conical penis is formed by the narrowed tip of the ectal duct, and may be retracted within the 20–40 μm deep sac (Fig. 2 K–L). Pyriform accessory glands surround male pores; cells granular, single or in clumps to 60–120 μm high, the entire mass to 150 μm wide (Fig. 1 G). Additional clusters of large (diameter to 25 μm), apparently vacuolated cells appear to be associated with the atria or the male pores, but are not joined by distinct ducts; these large cell clusters extend to near the apex of the atrium, adjacent to the atrium within X, or in XI if the atrium penetrates the posterior septum (Fig. 1 E, G: 2I –J).
Atrium may extend into XI. Ectal duct indistinct and short (length 40–84 μm, width 25–38 μm), gradually widening at the ampulla (Figs. 1 E, G; 2E); musculature more or less transverse-circular; a continuation of ampulla muscle, but not in distinct layers. Atrial duct expands slightly to about 30–40 μm in diameter at the base of the penis (Fig. 2 K). Atrial ampulla elongate-ovate to club-shaped; length 215–355 μm, width at middle 94–182 μm. Ampulla with a very thick outer muscle layer, to 45–88 μm, composed of about 12–16 thin layers of fibers in alternating spirals, oriented at about 50–60˚ from the longitudinal axis (Fig. 2 F, G). Epithelium thin and indistinct, as little as 2 μm (at most 7–8 μm) thick (Fig. 2 F–H); lumen very narrow, usually less than 5 μm, but may be expanded slightly at ental end (Fig. 1 G, 2H). No multicellular prostate glands; ampulla covered with a thin (4–6 μm) cell layer (Fig. 2 H–I).
Remarks. Eclipidrilus breviatriatus differs from all other Eclipidrilus in having very short atrial ducts; the absence of multicellular prostates is also unusual. However, the very thick, multilayered, spiral musculature of the atrium associates it with the E. (Leptodrilus) subgenus, and distinguishes it from other genera in the family. The very small spermathecal ampullae also distinguish it from other congeners, except for Eclipidrilus microthecus n. sp. (see below). Unmounted worms could usually be distinguished from other small lumbriculids in the region by the short prostomium, prominent septal grooves, and limited secondary segmentation in anterior segments.
Of the 17 specimens of this taxon available for study, 14 were fully mature, with sperm in the spermathecae. Most specimens appeared strongly contracted. Because of the small size of these worms, it was difficult to see details of vasa deferentia, nephridia, and blood vessels. Distinct prostate glands were never seen; although a diffuse mass of transparent, apparently vacuolated cells was often visible adjacent to the atrial ampullae, they did not appear to be attached to the atria. One of the atria was missing in two specimens, but the remaining atrium retained its normal lateral position.
description: Published as part of Fend, Steven V. & Lenat, David R., 2012, New Eclipidrilus species (Annelida, Clitellata, Lumbriculidae) from southeastern North America, pp. 51-67 in Zootaxa 3194 on pages 53-56, DOI: 10.5281/zenodo.210008