Achaeta florens Schmelz & Chen & Józefowska 2024, sp. nov.
Creators: name: Schmelz, Rüdiger M.
name: Chen, Juanjuan
name: Józefowska, Agnieszka
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Enchytraeida
Enchytraeidae
Achaeta
Achaeta florens

description: Achaeta florens sp. nov.
(Figures 1, 2)
Holotype. CEP-DZ-149401-N, adult specimen, anterior 16 segments, unstained whole-mount, with DNA sequences COI PP079494, ITS PP084616.
Type locality. Poland, Upper Silesia, Szczakowa, reclaimed post-mining sand pit afforested with oak (Quercus rubra L.), 50°14’28.8”N 19°23’36.2”E; soil type Arenosol, sandy loam and loamy sand texture, pH (H 2 O) 4.6– 4.8.
Paratypes. CEP-DZ-149402-N, adult specimen, anterior 21 segments, unstained whole mount, with DNA sequences COI PP079493, ITS PP084615. CEP-DZ-149404-N, adult specimen, anterior 17 segments, unstained whole mount, with DNA sequences COI PP079495, ITS PP084617. CEPU: CEP-DZ-14905-N to CEP-DZ-14913- N, 10 specimens (7 adult, 3 subadult), complete, stained whole mounts. All from type locality.
Further material. 11 specimens (6 adult, 4 subadult, 1 juvenile), stained whole mounts, in the 1st author’s collection. 55 specimens, investigated and identified in vivo, a subset preserved in 100% ethanol. All from type locality.
Diagnosis. Body length 4–6 mm; up to 35 segments; pyriform glands dorsally and ventrally; oesophageal appendage small in V; pharyngeal glands without secondary lobes; two pairs preclitellar nephridia, at 6/7, 7/8; clitellum interrupted dorsally and ventrally, separate transverse rows, hyalocytes in irregular longitudinal rows dorso-laterally; seminal vesicle absent; male glands small and separate; spermatheca length c. 2 segments, ectal pores ventrally, each surrounded by flower-like field of vesicular gland cell apices.
Description. Thin, comparatively active and agile Achaeta -worms, forming irregular coils and curls in water when alive. Body length 4–6 mm (viv); 4.9–6.3 mm (fix). Body diameter 0.13 mm (viv, 1 ind.), up to 0.2 mm at XII (viv); fixed specimens: 0.08–0.13 mm (V) 0.08–0.16 mm (XII) 0.09–0.11 mm (XX). Adults with 31–35 segments (N=13). Body wall thin, diameter 10–12 μm, cuticle thin (<1μm). Pyriform glands (Fig. 1B,C, 2D) dorsally and ventrally, dorsals from II, length 1/3 to 1/2 body diameter, ventrals from III, smaller. Other epidermal gland cells inconspicuous.
Brain (Fig. 1A) rounded posteriorly, 76–90 μm long, 30–40 μm wide (fix), ventral nerve cord (Fig. 1C, 2D,E) ganglionic. One pair of prostomial ganglia in front of brain; three pairs of papillae laterally and anteriorly, as inner thickenings of body wall (Fig. 1A). Pharyngeal glands (Fig. 1C) in IV–VI, all united dorsally, no secondary lobes. Oesophageal appendage (Fig. 1C) unpaired in V, no canal in IV. Dorsal blood vessel from VII. Intestine widening gradually. Chloragocytes (Fig. 2A) conspicuous, large, diameter c. 20 μm, filled with yellow-brown to brown vesicles. Midgut par tumida in 1/2XVIII–XXVI, extending over 6–7 segments. Two pairs preclitellar nephridia (Fig. 1C, 2A), at 6/7, 7/8. Anteseptale with coils of canal, as long as wide, funnel in oblique position, postseptale c. 2x as long as anteseptale, gradually merging into thin and elongate efferent duct; no terminal vesicle. Coelomocytes (Fig. 2F) pale flat discs, with outer circumferal and inner radial lines, finely vesicular, outer margin hyaline.
Clitellum (Fig. 1B, 2E) in XII–1/2XIII, interrupted dorsally and ventrally, dorsal interruption wider than ventral one, wider than distance of dorsal pyriform glands, ventral interruption anteriorly as wide as male pore distance, narrowed posteriorly to one gland cell width; clitellum cells in 18 or 19 conspicuously separate transverse rows; hyalocytes mostly in dorsal half, two irregular longitudinal rows on each side; at dorsal borders of clitellum, more granulocytes than hyalocytes; at ventral border only granulocytes. Hyalocytes 18–24 μm long and 12–13 μm wide, granulocytes ca. 14 μm long and 9 μm wide (fix).
Testis in XI, ovary inXII. Seminal vesicle absent, spermatogonial cysts in XI.Sperm funnels (Fig. 2B) cylindrical, not longer than body diameter, c. 3–4x as long as wide (ca. 120 μm by 30–40 μm) (106–140 μm long and 26–36 μm wide, fix), collar almost as wide as funnel body. Spermatozoa 30–35 μm, heads 11–15 μm. Vas deferens often in dense regular spirals or coils, diameter 7–8 um. Male pores (Fig. 2E) on body surface, no area glareosa. Male glandular bulbs (Fig. 1B, 2E) oval, longer than wide (32–50 um by 20–31um), pierced centrally by vas deferens; glands separate, distance as wide as or slightly wider than width of ventral nerve cord or male glandular bulbs.
Spermathecae (Fig. 1C,D, 2C,D) free, extending into VI (VII), sometimes confined to IV–V or IV, depending on bends or tortions; spermathecal pores ventrally, each surrounded by a blossom-like crown of c. 6 vesicular gland cell apices (Fig. 1D, 2C); ectal part massive, diameter c. 35–40 um,>2x as long as wide, also vesicular but less conspicuously, entally spermatozoa in oblique position; connecting tube narrowed, ental reservoir as wide as ectal part; sperm in ampulla, connecting tube and ental reservoir.
Etymology. Named after the blossom-like arrangement of glandular vesicles around the spermathecal ectal pores (Fig. 1D, 2C).
Remarks, morphology. There are currently 10 nominal species of Achaeta with four segmental pyriform glands, eight from Europe (Schmelz & Collado 2010) and two from India (Prabhoo 1966, Dash & Thambi 1978). In Europe, A. affinis and A. danica are in the size range of the new species. They differ from the new species in the oesophageal appendage, which has a canal in IV, and in the clitellum, with hyalocytes arranged in baguette-like longitudinal packages. Furthermore, the spermathecae in A. danica are usually longer (extending into IX); in A. affinis, they are absent.
Outside Europe, the new species is most similar to A. nurmineni Dash & Thambi, 1978, described from southern Orissa, India, in body length (4–6 mm), segment number [24–30–(34)], clitellum in 18–20 transverse rows, absence of a seminal vesicle and short spermathecae. A species comparison is made difficult by the lack of information on several taxonomically important characters: oesophageal appendage, position of preclitellar nephridia, clitellum dorsally and ventrally. Other characters are doubtfully described or illustrated and need reinvestigation: the large pyriform glands are said to be in lateral position (not in dorsal position as usual) and Figure 12 shows spermathecal ectal pores in lateral position (not in ventral position as in all other Achaeta species with four segmental pyriform glands). The spermathecae are described as sac-like, and the coelomocytes are oval to spindle-shaped and with granular structure; these details may or may not serve as characters to distinguish the species. There is no record after the original description, and whereabouts of the type specimens are unknown. We consider A. nurmineni Dash & Thambi, 1978 as a species inquirenda.
The blossom-like crown of intracellular vesicles around the spermathecal pores was new to us when we first saw it but in the meantime we have also seen it in Achaeta aberrans, Nielsen & Christensen, 1961, a species with 6 segmental pyriform glands and lateral spermathecal ectal pores, and in Achaeta bohemica (Vejdovský, 1879), a species with 2 segmental pyriform glands and secondary pharyngeal gland lobes in V and VI. In fact, this new species of Achaeta lacks any kind of particular feature, and is distinguished only by a combination of characters.
Remarks, molecular comparison. Currently 42 COI sequences of specimens identified as Achaeta are publicly available. Uncorrected p-distances were calculated based on COI sequences, and clear genetic gaps were observed between our new species and the other 23 species records, which represent 16 different species of Achaeta, some of them unnamed (Table 2), with interspecific distances ranging from 16.4% to 26.1%. Intraspecific distances were not observed; the three sequences of COI and ITS, respectively, obtained from the holotype and two paratypes are identical.
description: Published as part of Schmelz, Rüdiger M., Chen, Juanjuan & Józefowska, Agnieszka, 2024, Two new species of Achaeta (Enchytraeidae, Oligochaeta) from afforested post-mining and post-fire sites in Poland, pp. 1-14 in Zootaxa 5437 (1) on pages 3-6, DOI: 10.11646/zootaxa.5437.1.1, http://zenodo.org/record/10959255