Xetadrilus prolixglandus Chen & Schmelz & Zhang & Xie 2022, sp. nov.
Creators: name: Chen, Juanjuan
name: Schmelz, Rüdiger M.
name: Zhang, Zuxu
name: Xie, Zhicai
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Enchytraeida
Enchytraeidae
Xetadrilus
Xetadrilus prolixglandus

description: Xetadrilus prolixglandus sp. nov.
(Figures 2–5)
Holotype
Fully mature, whole-mounted specimen, stained, GZO202007003.
Type locality
Site I. Soil and moss layer of Cyclobalanopsis glauca, Pinus taiwanensis and Eurya japonica mixed forest (108°39′ 24.79°E, 27°54′ 43.15°N), 1970 m asl, Fanjing Mountain, Guizhou, China, coll. Z.X. Zhang, X.K. Jiang and J.J. Chen, 25 July 2019.
Paratypes
GZO202007001, GZO202007002, stained and whole-mounted, two mature specimens from the type locality, same data as holotype. GZO202008001, GZO202008002, stained and whole-mounted, two mature specimens from site F. CJJ91, one mature specimen from site 1, whole worm used for DNA extraction, preserved as total DNA.
Further material investigated
One mature specimen from site C, nine mature specimens from site F, one mature specimen from site G, two specimens from site H, four specimens from site I; three mature specimens from site 1, three mature specimens from site 2, one mature specimen from site 3, one specimen from site 4, one specimen from site 5, one specimen from site 9, two specimens from site 10: 29 specimens in total, preserved in 75% ethanol.
Etymology
The Latin prefix ‘prolix-’ means extended and elongate; ‘prolixglandus’ refers to the elongation of the third pair of pharyngeal glands, consisting of an anterior dorsal part in VI and a posterior ventral part in VI–VII.
Diagnosis
This new species can be diagnosed by the following combination of traits: (1) ventral chaetae in posterior segments enlarged, ca. 1.5× as large as anterior; (2) the third pair of pharyngeal glands elongate, with separate dorsal lobes in VI; (3) two pairs of secondary pharyngeal gland lobes in V–VI; (4) brown coelomocytes with refractile vesicles completely filled; (5) spermathecae free, confined to V; (6) epidermal gland cells distributed evenly; (7) gut widening gradually in VII, no intestinal diverticula; (8) two pairs of preclitellar nephridia in 7/8–8/9; (9) dorsal vessel originating from XII–XIII, blood colourless.
Description
Small-sized worms. Length 2.4–3.5 mm, diameter 0.07–0.17 mm in segment VII and 0.08– 0.22 mm in segment XII. Number of segments 23–28. Chaetae two per bundle, formula 2, 0–0: 2–2. Chaetae straight, with proximal bend. Lateral chaetae present in II–VII, absent from VIII on, ventral chaetae absent in XII in mature worms (Figure 2a). Ventral chaetae in preclitellar segments ca. 25–30 μm long and 2.5 μm thick (Figure 3d), increasing in size behind clitellum towards posterior end, ca. 32.5–45 μm long and 2.5–4 μm thick (ca. 1.5× as large as anterior). Prostomium with head pore in mid-dorsal position, slit transverse (Figure 2a). Epidermal gland cells grey, inconspicuous, cells almost round (diameter ca. 2.7–4 μm, in vivo) and evenly distributed in 7–8 separate transverse rows per segment (Figure 4d). Clitellum in XII–1/2XIII, conspicuous thickening, saddle-shaped, clitellum-free mid-ventral field as wide as distance between male pores. Cells in dense transverse rows, roughly rectangular, with hyalocytes (ca. 19–25 μm high and 11–13 μm wide, in vivo) larger than granulocytes (ca. 11–25 μm high and 7.5–10 μm wide, in vivo); with larger proportion of hyalocytes dorsally, and larger proportion of granulocytes laterally (Figures 2a, 4e, f). Body wall thin, 7–12 μm thick, cuticle <1 μm thick (in vivo).
Brain about 2 × as long as wide (ca. 50 μm wide and 100 μm long, in vivo), incised posteriorly, sides converging anteriad (Figures 2a, b, 3a). A pair of prostomial ganglia present on prostomial nerves (Figures 2a, b, 3a). Pharyngeal glands with two unpaired dorsal lobes in IV and V, of almost the same size; primary ventral lobes in V, elongate; secondary ventral lobes in V and VI, spherical, smaller than primary ventral lobes. In VI–VII a pair of separate elongate lobes, consisting of an anterior dorsal part in VI and a posterior ventral part in VI–VII (Figures 2a, 3c). Oesophageal appendage and intestinal diverticula absent. Gut widening gradually in VII (Figure 2a). Chloragocytes inconspicuous, from V, and dense from VII. Dorsal vessel originating from XII–XIII, blood colourless. Nephridia two pairs in preclitellar segments, at 7/8 and 8/9 (Figures 2a, 3e). Anteseptale with funnel and parts of nephridial body, funnel attached obliquely, anteseptale about 26 μm long and 22 μm wide (in vivo); postseptale larger than anteseptale (ca. 40 μm long and 26 μm wide, in vivo), with a dorsal bump in mid-section; nephridial canal apparently with up and down zig-zag course; efferent duct rising subterminally, nephroporus inconspicuous, situated anteriorly of ventral chaetal bundles, no terminal vesicle. Nephridia in postclitellar segments in varying positions. Coelomocytes one type, nucleate mucocytes slightly longer than wide ca. 17–24 μm long (in vivo); cells brownish in vivo, with small spherical and refractile vesicles (Figure 3f).
Seminal vesicle absent. Spermatozoa conspicuous at the opening of sperm funnel, ca. 40 μm long, head ca. 14 μm long (in vivo) (Figure 2a, c). Sperm funnel pear-shaped, with distinct collar, not or only a little wider than funnel body; sperm funnel small, ca. 40 μm long and 26 μm (at collar) wide (in vivo) (Figures 2a, c, 4a). Vas deferens in loose or dense coils ventro-laterally, diameter ca. 5 µm (in vivo) (Figures 2a, 4c). Male copulatory organ inconspicuous, glandular bulb with musculature (Figures 2a, 4f), roughly spherical, ca. 32 μm in diameter (in vivo). No accessory copulatory glands. Spermathecae free, not attached to oesophagus, like a proximally blind-ending tube, confined to V; ectal pores lateral at 4/5, without ectal glands, ectal ducts short (64 µm long, 10 µm wide, in vivo), ampullae wider than ectal ducts (28 µm long, 16 µm wide, in vivo) with thin wall, empty or with spermatozoa (Figures 2a, 3b). Two mature eggs at a time, occupying 3–4 segments (Figures 2a, 4b). Remarks
The new species is most similar to Xetadrilus maacki Schmelz, 2011, which also has two pairs of preclitellar nephridia, brown coelomocytes, spermathecae confined to V and intestine widened in VII. However, in X. maacki the pharyngeal glands are dorsally united in VI and there are three pairs of secondary ventral lobes in V–VII. Further conspicuous differences of X. maacki from the new species include sigmoid chaetae in posterior segments and epidermal gland cells only mid-ventrally. A comparison of X. prolixglandus sp. nov. with similar species is presented in Table 4.
Molecular analyses confirm that X. prolixglandus sp. nov. is a species distinct from other Xetadrilus species for which sequences are currently available, since its sequences form distinct lineages on the phylogenetic trees based on the COI region (Figure 5). However, our analysis is limited by the lack of sequence data for other species of Xetadrilus.
description: Published as part of Chen, Juanjuan, Schmelz, Rüdiger M., Zhang, Zuxu & Xie, Zhicai, 2022, The enchytraeid fauna (Enchytraeidae: Clitellata) of the Fanjing Mountain National Nature Reserve (China) with description of two new species, pp. 1957-1996 in Journal of Natural History 56 on pages 1962-1967, DOI: 10.1080/00222933.2022.2140085, http://zenodo.org/record/7426634