Marionina orbifera, Felföldi & Nagy & Dózsa-Farkas, 2024

Felföldi, Tamás, Nagy, Hajnalka & Dózsa-Farkas, Klára, 2024, New data on the polyphyletic Marionina genus (Annelida, Enchytraeidae): description of three new species from European shore habitats, Zoosystematics and Evolution 100 (4), pp. 1269-1286 : 1269-1286

Marionina orbifera sp. nov.

Fig. 2

Type material.

Holotype: Ma. 6, slide No. 3081. Type locality: (Loc. 3.) Italy, Punta Ala Grosseto, Castiglione della Pescaia , decaying seagrass detritus, 42 ° 46 ' 00.0 " N, 10 ° 51 ' 31.0 " E, Leg. András Dózsa-Farkas and Kinga Dózsa-Farkas, 24 Sep 2020.

Paratypes: in total, 15 specimens: P.147.1 slide No. 3027, P.147.2 slide No. 3049 (two specimens), P.147.3 slide No. 3050 (two specimens), P.147.4 slide No. 3053 (two specimens), P.147.5 slide No. 3058, P.147.6 slide No. 3060, P.147.7 slide No. 3071, P.147.8 slide No. 3072, P.147.9 slide No. 3074, P. 147.10 slide No. 3075, P. 147.11 slide No. 3079, P. 147.12 slide No. 3080. Same data as for holotype .

Further material examined.

20 specimens (10 only in vivo).

Diagnosis.

(1) Small size (body length 2.3–3.3 mm, 130–220 µm wide at clitellum, in vivo, segment number 17–22); (2) chaetae straight with ental hook, two chaetae per bundle, slightly longer at the posterior end of the body; (3) clitellum saddle-shaped; (4) brain truncate posteriorly; (5) first and secondary pharyngeal glands united dorsally with small ventral lobes; the third pair elongate, free dorsally; (6) dorsal vessel from clitellar region, blood colorless. The dorsal anterior blood vessel bifurcation anteriorly behind the pharynx; (7) two pairs of preclitellar nephridia; (8) coelomocytes oval or disc-shaped with granules, 14–22 μm long in vivo; (9) seminal vesicle well developed; (10) sperm funnel 1.5–3 times longer than wide in vivo, collar high and narrower than funnel body, spermatozoa 44–60 µm long, heads 20–25 µm in vivo; (11) male copulatory organ small and compact, 30–40 µm long in vivo; (12) small subneural glands are in XIII – XIV; (13) ectal duct of spermatheca short, surrounded by glands. Ampulla spherical, diameter 40–55 µm in vivo, the lumen characteristically full of many spherical sperm rolls. Ampulla attached to the oesophagus; (14) 1–3 mature eggs at a time.

Description.

Small species, holotype 2.1 mm long, 134 µm wide at VIII and 150 µm at clitellum (fixed), segment number 21. Body length 2.3–3.4 mm, width 110–188 µm at VIII and 130–220 µm at clitellum, in vivo, length of fixed specimens 1.1–2.1 mm, width 118–160 µm at VIII and 125–180 µm at clitellum, segment number 17–24. Chaetae straight with ental hook. Chaetal formula: 2 - 2: 2 - 2 (in one case, three chaetae were in one ventral bundle of the segment III). The chaetae are equal in size within the bundles, a little longer in the ventral bundles than in the lateral ones. Chaetae are 20–30 × 2.2 μm in preclitellar segments and 28–35 × 2.8–3 μm at the posterior end of the body (Fig. 2 D ). Clitellum saddle shaped in XII- 1 / 2 XIII, gland cells squarish, arranged in about 16–17 transverse rows (Fig. 2 C ), midventrally absent (Fig. 2 B ). Head pore at 0 / I, no dorsal pores. Epidermal gland cells inconspicuous in vivo. Thickness of body wall about 15–16 µm, and cuticle thin (1 µm).

Brain (Fig. 2 A ) ca. 80 μm long (fix.) slightly longer than wide, truncate posteriorly. Pharynx well developed. Prostomial glanglia absent. In the ventral nerve cord, perikarya continuous. First and secondary pharyngeal glands compact and united dorsally, with small ventral lobes; the third pair elongate and free dorsally (Fig. 2 F ). Chloragocytes from IV forming a denser layer from VI, about 17–30 μm long in vivo, filled with refractive globules. Transition between oesophagus and intestine gradual; oesophageal appendage and intestinal diverticula absent. Midgut pars tumida not seen. Dorsal vessel origin from clitellar region; blood colorless. The dorsal anterior blood vessel bifurcation in III (Fig. 2 E ). All coelomocytes nucleated oval or disc-shaped with granules, 14–22 μm long in vivo (Fig. 2 G ) and 8–10 μm fixed. Two pairs of preclitellar nephridia in 7 / 8 and 8 / 9, preseptal part consisting of funnel and coils of canal, postseptal part elongate, about four times as long as preseptal part, efferent duct terminal. The first postclitellar pair of nephridia at 13 / 14. Seminal vesicle well developed, paired, extending anteriorly to X or IX and posteriorly to XII – XIII (Fig. 2 H ). Sperm funnels cylindrical, 85–140 μm long in vivo, 60–100 μm, fixed, and about 1.2–3 times longer than wide, collar high, and narrower than funnel body (Fig. 2 C, I ). Spermatozoa 44–60 µm long (in two specimens they were 80–87 μm long), heads 20–25 µm in vivo (Fig. 2 I ), (23–28 µm and 10–15 µm, respectively, when fixed). Sperm ducts short, coiled into a loose spiral, diameter 5–7 µm, in vivo. Male copulatory organs small and compact (Fig. 2 B ), 30–40 µm long, 20–35 µm wide, and 15–30 μm high, in vivo (25–38 µm long, 18–25 µm wide, and 20–30 µm high, when fixed). Small subneural glands in XIII – XIV (Fig. 2 J ). The ectal duct of spermatheca short, 20–35 µm long, surrounded along the length by glands, somewhat larger entally, no distinct rosette around the orifice (Fig. 2 M ). Ampulla spherical, diameter 40–55 µm in vivo (33–40 µm, fixed), the lumen filled with many spherical sperm rolls (Fig. 2 K – M ). Ampulla attached with a short ental duct to the oesophagus. 1–3 mature eggs at a time.

Etymology.

The species is named after the characteristic sperm rolls („ orb ”) in the spermatheca [ orbifera = orb-bearing (Latin)].

Distribution and habitat.

Known from the type locality, decaying seagrass detritus.

Differential diagnosis.

Among the intertidal small Marionina species, nine species ( M. sjaelandica Nielsen & Christensen, 1961 , M. levitheca Erséus, 1990 , M. coatesae Erséus, 1990 , M. swedmarki Lasserre & Erséus, 1976 , M. vancouverensis Coates, 1980 , M. limpida Shurova, 1979 , M. cana Marcus, 1965 , M. transunita Coates, 1990 , M. southerni ( Černosvitov, 1937) and the new species are characterized by spherical sperm rolls in the spermathecal ampulla. The main differences are as follows: The spermathecae of M. sjaelandica and M. coatesae are similar to the new species; more sperm rolls are in the spermathecae, but not in the cavity, but embedded in the walls of the ampulla. Both species have more segments (segment number 24–27 in M. sjaelandica , 27–31 in M. coatesae , vs. 18–24 segments in the new species). M. levitheca is larger (segment number 38–41), the sperm rolls are arranged in distinct globular cavities scattered in the wall, and there are no glands at the ectal duct of the spermatheca. In M. swedmarki , the spermathecal orifice has a conspicuous gland-rosette. M. vancouverensis has a maximum of six chaetae per bundle (vs. only two in the new species). M. limpida is larger (6–8 mm long, vs. 2.3–3.3 mm), the subneural glands are only in XIII (vs. XIV – XV), the sperm funnel and sperm duct are longer, and the brain is incised posteriorly. In M. cana , the sperm rolls are in the walls of the ampulla, the ectal duct is not glandular, and the dorsal vessel origin is in IX, not in the clitellar region; moreover, the brain is incised posteriorly. M. transunita is also larger (with segment numbers 26–40), and the two spermathecae are connected entally. M. southerni is 8–10 mm long with 28–36 segments; the coelomocytes are black in transmitted light; and the spermatheca has many sessile diverticula.

Figures

Figure 2. Micrograph of Marionina orbifera sp. nov. A. Brain; B. Clitellar glands absent ventrally (the male copulatory glands = m); C. Clitellum (sperm funnels = sf); D. Chaetae at the body end; E. Anterior bifurcation of the dorsal vessel in III; F. Pharyngeal glands, lateral view (primer pharyngeal gland pairs marked with white arrows, ventral lobes marked with black arrows); G. Coelomocytes; H. Large seminal vesicle; I. Sperm funnels (sperm funnels = sf, seminal vesicle = sv); J. Subneural gland in XIV; K – M. Spermathecae (the sperm rolls in the ampullae marked with black arrows, the glands at the ectal duct marked with white arrows). A – E, G – I, K – M. In vivo; F, J. Fixed, stained. Scale bars: 50 μm (A, C, E, F, I, J, K); 20 μm (B, D, G, H, L, M).