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Comprehensive Description

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 The description is based on the holotype (adult, 445 µm long; Fig. 2A), with ranges provided from specimens measured in vivo. Body strap-shaped with two notable constrictions at mid-pharynx (U06-07) and caudal end (~U82); first constriction demarcates the approximate mid-length of the pharynx and the second constriction demarcates the region of the accessory copulatory organs (Figs 1, 2A). Pharynx 90 mm long with no pharyngeal pores observed. Few sensory hairs to 8 µm long line the mouth. Stiff sensory hairs 8–15 µm are present along the ventrolateral, lateral and dorsolateral margins of the body. Ventral locomotory cilia present as two columns, each approximately 8 µm wide, that extend from ca. U05 to the posterior end (Fig. 1). Numerous small (2–5 µm) epidermal glands along the margins of the body.  Cuticular armature. A crossed-helical pattern of up to eight columns of elliptical scales extend across the dorsal body wall; the number of scales per column varies from 8-10 in the pharyngeal region to up to 12 in the trunk. At least three columns of elliptical scales extend around the lateral body margins and reach the ventral locomotory cilia (Fig. 1). All scales are similar in shape, lack a keel, and are approximately 7–8 µm long. None of the scales are imbricated. Two columns of ventral scales are present at the midline between the ciliary fields (Figs 1, 2C). The scales are relatively small, ca. 4–5 µm long, and oriented in a herringbone pattern in most specimens, with the anterior end of both scales farther apart from each other (ca. 5 µm) relative to their posterior ends (ca. 2–3 µm). While the herringbone pattern is evident in all specimens, some specimens had individual scales (not an entire column) oriented in a more parallel fashion (e.g., see Fig 2C); this may be evidence of individual variation in scale orientation. There was approximately 4–5 µm of space between each column and its adjacent ciliary field.  Adhesive tubes.Anterior adhesive tubes (TbA) distributed as a posteriorly curving arc of seven to eight tubes, 3–4 µm long, from the midline to the lateral body wall (Fig. 2C). Lateral adhesive tubes (TbL) absent from the pharyngeal region (Fig. 1). Fourteen to seventeen TbL present in the trunk region, 8–10 µm long, beginning at U28 and extending to the second body constriction. Tubes are spaced evenly down most of the trunk. A single tube is present in the demarcated region of the caudal organ, around U92. Approximately eleven evenly spaced dorsal adhesive tubes (TbD), 8–10 µm long, beginng at U28 and extending to ~U90. Eight posterior adhesive tubes (TbP), 9–10 µm long, distributed as four adhesive tubes per side on rounded caudum.  Digestive tract.Small terminal mouth to 5 µm wide (Fig. 2B). Pharynx to 20 µm wide and 90 µm long. Pharnygeo-intestinal junction at U20. No pharyngeal pores observed. Intestine narrow and tapering toward posterior end. Diatoms present in a single specimen. Anus at U78.  Reproductive system.Neither testes or ovaries observed. A single large egg, approximately 62 µm diameter, was present in one adult (holotype). A clear, sac-like organ interepreted as the frontal organ was present at U81–83; the organ was approximately 22 µm x 16 µm in diameter and in a single specimen appeared to contain filiform sperm. A caudal organ was present at the posterior end (U83–95), approximately 63 µm long x 30 µm wide (range: 50 µm–63 µm long, 24 µm–30 µm wide), hyaline in appearance with a straight central canal that extends along the organ’s anterior-posterior axis; the canal appears sclerotic (coc, Fig. 3D). The caudal organ is muscular. The muscle cells interdigitate to form spindle-shaped, incomplete circular fibers(Fig. 3B). A single gland, ca. 10 µm in diameter, is present posterior of the caudal organ (Fig. 3A, D).  Muscular system. Musculature present as circular, helicoidal and longitudinal bands. Pharynx strongly invested with splanchnic circular muscles and overlain by helicoidal bands and longitudinal muscles (Fig. 3E). The number of individual circular muscles and helicoidal bands could not be determined. In the trunk region, the helicoidal muscles extend to ca. U40 (Fig. 3E). Longitudinal muscles extend from the pharyngeal region to the caudum as three pairs of dorsal (dlm)/dorsolateral (dllm) bands (Fig. 3E). The ventrolateral longitudinal muscles (vllm) are the thickest muscles in the body and extend from ca. U03 to the caudal end (Fig. 3E). Three pairs of ventral longitudinal bands extend from the pharynx to the posterior end. All longitudinal muscles in the trunk region are surrounded by somatic circular muscles (scm) that form numerous, distinct rings down the length of the body (Fig. 3E). Beginning ca. U80-81, there is a large number (>30) of closely spaced somatic circular muscles that extend posteriorly for approximately 40 µm; the circular muscles demarcate the posterior region of the body (cm-pc) with the accessory sexual organs (Figs 1, 3B,C).


Creative Commons Attribution 3.0 (CC BY 3.0)

© Rick Hochberg, Sarah Atherton, Vladimir Gross

Source: ZooKeys

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