Fridericia sphaericoides, Dózsa-Farkas, Klára, Nagy, Hajnalka, Felföldi, Tamás & Hong, Yong, 2022

Dózsa-Farkas, Klára, Nagy, Hajnalka, Felföldi, Tamás & Hong, Yong, 2022, Four new enchytraeid species (Enchytraeidae, Annelida) from a Korean mountain (Jeoksangsan), Zootaxa 5094 (2), pp. 234-260 : 241-243

Fridericia sphaericoides sp. n.

( Figures 2B–C , 6 , 7A–C, E–G )

Type material. Holotype: NIBRIV0000886164, slide No. 2937, adult specimen, stained, whole mount. Type locality: Jeoksangsan , Jeoksang-myeon, Muju-gun, Jeollabuk-do, Korea, soil and litter layers of Pinus densiflora and mixed forests, N 35 ˚56′58.63″, E 127 ˚40′26.90″, 387 m asl, 06.11.2019 . Paratypes: NIBRIV0000886165, slide No. 2998 (DNA ID 1399 ), NIBRIV0000886166, slide No. 2936, adult specimens stained whole mount from type locality. P. 139.1–139.11., 11 adult specimens, fixed, stained, whole mount, slides No. 2932–2933, 2938, 2951–2953, 2981–2983, 2991–2992, from type locality .

Further material examined. 3 specimens only in vivo, not preserved.

Etymology. Named after the similarity to F. sphaerica Dózsa-Farkas, Felföldi & Hong, 2015 .

Diagnosis. The new species can be recognized by the following combination of characters: (1) large body size (length up to 20 mm, width up to 0.5 mm, cuticle thin in vivo), segments 47–61; (2) maximum 4 chaetae per bundle; (3) clitellum girdle-shaped, gland cells arranged in transverse rows, in the ventral midline before and about the half part of the male copulatory organs only granulocytes; (4) five preclitellar pairs of nephridia, 6/7–10/11; (5) coelomo-mucocytes type b, lenticytes small and scarce; (6) chylus cells in XIV–XVI (2–3 segments); (7) seminal vesicle large; (8) subneural glands absent; (9) sperm funnel cylindrical, about 2/3 as long as body diameter in vivo, collar slightly narrower as funnel body; (10) spermathecae with very long ectal duct, without ectal glands, the spherical ampulla large (diameter 90–116 µm, in vivo), ectal duct canal straight proximally, separate openings into oesophagus.

Description. Holotype 18.4 mm long, 340 µm wide at VIII and 410 µm at clitellum in vivo (10.3 mm long, 380 µm wide at VIII and 390 µm at clitellum, fixed), segments 52. Body length of paratypes 14–20.5 mm, width 320–420 µm at VIII and 350–480 µm at clitellum, in vivo, length of fixed specimens 7–12 mm, width 370–480 µm at VIII and at clitellum, 350–520 µm, segments 47–61. Chaetal formula: (2)3,4 – 4,2: 4 – 4,3,2. In one case (slide No. 2938) in segment X, 5 chaetae occur in one bundle. As in other Fridericia species , chaetae within a bundle arranged in pairs, outer longer and thicker than inner (45–55 × 4–5 μm vs. 22–32 × 3–4 μm, preclitellar bundles). Lengths of chaetae in postclitellar segments about the same as larger outer chaetae in preclitellar bundles. Two chaetae per bundle from about XXI–XXVII; chaetae gradually increasing in size posteriad from 52 × 5 μm to 62–70 × 5 μm in terminal segments. Head pore at 0/I. Dorsal pores from VII. Brownish epidermal gland cells arranged in 2–3 transverse rows per segments ( Fig. 6F ). Clitellum in XII–1/3XIII, girdle-shaped, hyalocytes and granulocytes arranged in dense rows dorsally ( Figs 6B–C ), in the ventral midline before and about the half part of the male copulatory organs only granulocytes ( Fig. 6D ). After fixation, body diameter of body narrowed at clitellum ( Fig. 6E ). Body wall thick, 40–58 µm, cuticle 1–3 µm, fixed.

Brain egg-shaped ( Fig. 6A ), 110–150 μm long, when fixed, 1.2–2 times longer than wide. Oesophageal appendages ( Fig. 6G ) with few short branches at forepart and at the end. Pharyngeal glands usually united dorsally, in IV widely connected, in V and VI connection may be narrow or absent; all with ventral lobes, small in IV, longest in VI ( Fig. 6H ). Chloragocytes from V. Dorsal vessel from XVIII–XXI, blood colourless. Midgut pars tumida not seen. Five pairs of preclitellar nephridia ( Fig. 6K ) from 6/7 to 10/11; length ratio anteseptale: postseptale 1: 1.7, midventral or subterminal origin of efferent duct. Coelomo-mucocytes elliptical with fine refractile granules at cell periphery, type b, length mostly 32–50 µm ( Fig. 6I–J ), aggregations opaque with dark tint, lenticytes small and scarce (4–10 μm long, in vivo). Chylus cells between XIV–XVI, occupying 2–3 segments. Seminal vesicle large (X–XI). Sperm funnels cylindrical ( Figs 6L–M , 7A ), 250–390 µm long, in vivo and 2–4 times as long as wide (180– 360 µm long and 1.7–2.7 times as long as wide when fixed). Collar slightly narrower than funnel body. Spermatozoa long, length 250–410 µm, heads 90–140 µm, in vivo. Diameter of sperm ducts about 10 µm. Male copulatory organs ( Fig. 7B ) 100–300 µm long, 80–200 µm wide and 50–60 μm high, in vivo (105–150, 78–100 and 30–65 µm fixed, respectively), bursa conspicuous, the laterally bent bursal slits are longitudinal. No subneural glands. Ectal ducts of spermathecae long, length 390–420 µm and width 20–30 µm, in vivo (250–380 µm long, and 18–24 µm wide, fixed), no ectal glands ( Fig. 7C–G ). Ampullae large, onion-shaped, without diverticula, diameter 90–116 µm in vivo (fixed 67–115 µm), ental bulbs (60–80 µm wide, in vivo) projecting into lumina of ampullae, sperm in a circle around the bulb ( Figs 2 , 7D–E ). Ectal duct canal 3–6 µm wide, straight inside the ental bulb, without spiral loops. Distal and proximal parts of ampullae considerably set off by a constriction, the proximal part about 60–90 µm long, fixed, separate openings into oesophagus. 2–4 mature eggs at a time.

Distribution and habitat. Only known from type locality (Site 2): Jeoksangsan, Jeoksang-myeon, Muju-gun, Jeollabuk-do, Korea, soil and litter layers of Pinus densiflora and mixed forests, N 35˚56′58.63″, E 127˚40′26.90″, 387 m asl.

Differential diagnosis. The new species is very similar to F. sphaerica Dózsa-Farkas, Felföldi & Hong, 2015 in number of segments and body size (47–60 segments, 14–20.5 mm long in F. sphaericoides sp. n. vs. 47–64 segments, 12–21.5 mm in vivo; but slightly thinner at the clitellum: 350–480 μm vs. 400–630 μm), in the thickness of the body wall and the cuticle (34–55 μm vs. 40–50 μm, cuticle <1 μm, in vivo), in the number of preclitellar nephridia (5 pairs), the origin of the dorsal vessel (XVIII–XXI vs. XVII–XXIII), the size and form of the sperm funnel is similar, but the sperm duct slightly thicker (7 μm vs. 9–12 μm wide in vivo), in the position of the chylus (XIV–XVI vs. XIII–XVI, 2–3 segments long). The main differences of the new species to F. sphaercia are as follows: the spermathecal ectal duct is shorter (387.1 ± 23.9 μm in the new species vs. 513.2 ± 93.7 μm). The diameters of ampulla and ental bulb are smaller (105.2 ± 11.3 μm vs. 118.8 ± 22.9 μm and 68.4 ± 10.4 μm vs. 90.0 ± 26.3 μm, respectively, in vivo). The canal of the ectal duct is straight inside the ental bulb, not with spiral loops as in F. sphaerica ( Fig. 7D ). The maximum number of chaetae in a bundle is 4 in the case of the new species, but may reach 5 in F. sphaerica . The separation of the two species is supported by the molecular results ( Fig. 9 ). Apart from F. sphaericoides and F. sphaerica , there are 5 more species of Fridericia more than 40 segments, onion-shaped spermathecal ampulla without diverticula and separate openings into the oesophagus: F. parathalassia Schmelz, 2002 , F. peregrinabunda Michaelsen, 1913 , F. seoraksani Christensen & Dózsa-Farkas, 2012 , F. callosa (Eisen, 1878) , and F. tuberosa Rota, 1995 . The main differences are as follows: in F. parathalassia there are only four pairs of preclitellar nephridia and subneural glands are present. F. peregrinabunda has only two chaetae per bundle. F. seoraksani is smaller (7.2–14.4 mm long, in vivo and 37–45 segments), the diameter of the spermathecal ampulla is smaller (50–60 μm), and the sperm funnel is also smaller (160–190 μm long, in vivo). F. callosa has a thick cuticle (3–5 μm vs. 1-3 μm in the new species) and the chaetae are often absent in several bundles. In F. tuberosa , diverticula-like protrusions may appear on the spermathecal ampullae, and spermathecal ectal glands and subneural glands are present. Furthermore, F. dianchiensis Chen & Xie, 2008 and F. jeoksangsaniensis sp. n. (see below) have similar spermathecae but the two spermathecal ampullae are proximally fused.

Figures

FIGURE 2. A. Decimodrilus bulbosus sp. n. Spermathecae. B–C. Fridericia sphaericoides sp. n. B. Spermatheca. C. Coelomocytes. D–E. Fridericia jeoksangsaniensis sp. n. D. Spermathecae. E. Coelomocytes. F. Mesenchytraeus globiferus sp. n. Spermathecae.

FIGURE 6. Micrographs of Fridericia sphaericoides sp. n. A. Brain. B–C. Clitellar glands, dorsal view. D. Clitellar glands, ventral view (male copulatory organs marked with arrows, asterisk=part of ventral midline with only granular gland cells). E. Diameter of body narrowed at clitellum. F. Epidermal glands, dorsal view. G. Oesophageal appendage. H. Pharyngeal glands (spermatheca marked with arrows). I–J. Coelomocytes. K. First nephridium at 6/7. L. Segments X–XI (sf=sperm funnel, sv=seminal vesicle, sperm heads marked with white arrow, tails marked with black arrow). M. Sperm funnels. B, F–G, I–M in vivo, A, D, E, H, I fixed, stained. Holotype D. Scale bars 50 μm, J 20 μm.

FIGURE 7. Micrographs of Fridericia sphaericoides sp. n. (A-C, E-G) and Fridericia sphaerica Dózsa-Farkas et al., 2015 (D). A. Sperm funnels of holotype. B. Male copulatory organ (b=bursa, g=glandular body). C. Spermathecae and pharyngeal glands. D. Spermathecae of F. sphaerica, with canal loops in ental bulb, to contrast with straight canal in F. sphaericoides. E–G. Spermathecae, with straight canal in ental bulbs (E, F). B–E in vivo, A, F–G fixed, stained. Holotype A. Scale bars 50 μm.

FIGURE 9. Fridericia species, maximum likelihood (ML) trees of the ITS region (A), CO1 (B) and H3 genes (C). A. ML tree of the ITS region based on 596 nucleotide positions using the Kimura 2-parameter substitution model. B. ML tree of the CO1 gene based on 459 nucleotide positions using the Tamura-Nei substitution model. C. ML tree of the H3 gene based on 208 nucleotide positions using the Kimura 2-parameter substitution model. Scale bar, 0.05 substitutions per nucleotide (except for CO1, where the scale is 0.1). Bootstrap values greater than 50 are shown at the nodes. Accession codes of sequences with collection information are given in Table 2.