Guaranidrilus cingulatus, Schmelz, Rüdiger M., Collado, Rut & Römbke, Jörg, 2011

Schmelz, Rüdiger M., Collado, Rut & Römbke, Jörg, 2011, Mata Atlântica enchytraeids (Paraná, Brazil): A new genus, Xetadrilus gen. nov., with three new species, and four new species of Guaranidrilus Černosvitov (Enchytraeidae, Oligochaeta), Zootaxa 2838, pp. 1-29 : 8-10

Guaranidrilus cingulatus sp. nov.

( Figs 3 , 8 C)

Holotype. MZUSP 1225, adult specimen, stained whole mount, Antonina, Cachoeira , medium old secondary forest on Cambisol [site 17], Mar 2004, leg. B. Förster, R. M. Schmelz.

Paratypes. MZSUP, 14 specimens, stained whole mounts:

MZUSP 1226, 6 specimens, Antonina, Cachoeira , 25°19'59"S – 48°42'02"W, young secondary forest on Gleysol [site 25], May 2003, leg. J. Römbke, R. M. Schmelz.

MZUSP 1227, 7 specimens, same data as holotype.

MZUSP 1228, 3 specimens, Antonina, Cachoeira , 25°19'04"–41''S, 48°40'36"–41'51"W, 20–120 m a.s.l., young and medium old secondary forests on Gleysol [sites 12, 24, 30], Oct 2004, leg. B. Förster, R. M. Schmelz.

MZUSP 1229, 1 specimen, Curitiba outskirts, 25°19'13''S, 49°06'22''W, 957 m a.s.l., Araucaria forest on Podzol, property of R. Marques, Oct 2004, leg. R. Marques, R. M. Schmelz.

UFPR, 6 specimens, 3 stained whole mounts, 3 ethanol-preserved, Guarequeçaba, Itaqui:

UFPR OL-10, 2 specimens, 25°14'45.3''S, 48°30'19.4''W, 27 m a.s.l., medium old secondary forest on Cambisol [site 38], Sep 2007, leg. P. Heine, R. M. Schmelz.

UFPR OL-11, 1 specimen, 25°18'31.8''S, 48°27'54,4''W, 93 m a.s.l., old-growth forest on Cambisol [site 40], Sep 2007. leg. P. Heine, R. M. Schmelz.

UFPR OL-12: 3 specimens, ethanol-preserved, 25°14'51,1''S, 48°29'31.4''W, 8 m a.s.l., medium old secondary forest on Cambisol [site 39], Jan 2008, leg. J. Römbke, R. M. Schmelz.

Additional material. Eight specimens from Cachoeira and Itaqui sites, examined in vivo, not preserved.

Etymology. 'cingulatus' (lat.) = girded; named in reference to the girdle-shaped clitellum, so far unique in the genus.

Description. Body dimensions. Small species, living adults ca. 3.5–5 mm long and 0.1–0.15 mm wide, whole mounts ca. 2.5–4 mm long and 0.15–0.2 mm wide. Segment number 26–32. Chaetae ( Fig. 3 B) two per bundle throughout, absent at XII, straight distally. In caudal segments chaetae 1.5– 2 x as large as largest anterior chaetae, equally large ventrally and laterally (ca. 60 µm long and 4–5 µm wide); in anterior segments laterals smaller than ventrals (30 µm vs. 40 µm). Epidermal gland cells invisible in vivo; in well-preserved whole mounts two rows distinguishable of inconspicuous, transversely elongate cells in dorsal half of anterior segments. Clitellum ( Fig. 3 E) well-developed, perfectly girdle-shaped, cells in ca. 34 transverse rows ventrally, dorsally rows indefinite when fully developed, here hyalocytes and granulocytes alternating, granulocytes smaller than hyalocytes and more numerous; ventrally only granulocytes; granulocytes almost square-shaped, giving a 'pavement'-like aspect. Head pore on prostomium mid-dorsally, prostomial inner papillae inconspicuous or absent.

Body wall thick in vivo, 5–10 µm thick in whole mounts, longitudinal muscle layer well-developed, especially in adults. Cuticle distinguishable, ca. 1.5 µm thick. Septa slightly thickened in preclitellar segments, from 4/5 to 5/ 6 or 8/9. Brain concave posteriorly, twice as long as wide (length ca. 70 µm, fix), prostomial ganglia very small or absent. Ventral nerve cord with suboesophageal ganglion in II–IV and segmental ganglia from V on. Oesophageal appendages ( Fig. 3 A,C) in anterior of VI, paired, spherical in dorsal view, sessile, side by side dorsally on gut wall, not larger than secondary ventral pharyngeal gland lobes. Pharyngeal glands ( Fig. 3 A,C) dorsally unpaired in IV, V, VI; primary and secondary ventral lobes in V and VI. Primary ventral lobes of VI largest. Intestinal diverticula ( Fig. 3 A,C) paired, lateral to intestine, confined to VII, occupying entire segment length, rarely less ( Fig. 3 A), separate from each other; each with large anterior and small stump-like posterior projection, the latter situated dorso-laterally, extending slightly into VIII in few specimens ( Fig. 3 C); connections of diverticula with intestine in posterior of VII; outer and inner surface often irregularly lobed or wavy; walls ca. 7–10 µm thick, no radial striation. Dorsal blood vessel from X – 1 / 2 XII. Preclitellar nephrida ( Fig. 3 F) 3 pairs, at 6/7 – 8/9, occasionally absent at either 6/7 or 8/9. Anteseptale slightly longer than wide, with ca. 1/3 of entire nephridial body, postseptale slightly bulging dorsad, with dorsal vesicle, gradually merging into short efferent duct, terminal vesicle absent; ante- and postseptale separated by a slight constriction at level of septa. Postclitellar nephridia ( Fig. 3 G) present in less than half of all positions; shape as in preclitellar nephridia, but more elongate. Coelomocytes slightly longer than wide, 17–28 µm long, with very fine wavy or groovy texture, no granula distinguished; cell margins smooth, refractile in oblique position; cells abundant but not obscuring other inner structures.

Seminal vesicle absent, free cysts in XI sparse. Spermatozoa ca. 47 µm long, heads 18 µm long. Sperm funnel ( Fig. 3 E,H) small, length less than 1/4 body diameter, 1.2–1.5x as long as wide, barrel-shaped, flattened. Vas deferens short with few loops, diameter 8 µm proximally, 5 µm distally. Male copulatory organ ( Fig. 3 H,I) minute, as if absent, male glands small, not thicker than clitellum. Male pores on body surface, surrounded by male glands, no bursa. Transverse copulatory body muscles sparse, not seen in vivo. Accessory glands absent. Spermatheca ( Fig. 3 C,D) simple, extending into V or VI, about as long as body diameter or slightly longer. Ectal duct not longer than 15 µm, with cuticle-lined canal only in distal half; distal part of ampulla ca. 15 µm wide, often without sperm; sperm present more proximally.

Habitat. G. cingulatus was found in young to medium secondary forests and old-growth forest. It was absent in pastures and at agroforestry sites, and almost absent at recently abandoned pastures (1 specimen identified).

Remarks. G. cingulatus is conspicuous (1) by the girdle-shaped clitellum, well-developed on all sides and quite prominent in living and preserved specimens. All other reproductive structures are small and inconspicuous. Further species-specific traits, diagnostic in combination: (2) epidermal gland cells appear absent; (3) cuticle conspicuous, longitudinal muscle layer well-developed, body wall often thick; (4) terminal (= caudal) chaetae up to twice as large as anterior chaetae; (5) oesophageal appendages in anterior of VI; (6) intestinal diverticula in VII, with posterior extension and often irregularly lobed; (7) three pairs of preclitellar nephridia, from 6/7 to 8/9. Traits 2–7 suffice to identify the species; they were used in the routine identification of animals, juveniles included.

Most similar to G. cingulatus is the North-American G. oregonensis Coates & Diaz, 1988 , described from fixed material. The species is similar in body length (3–4.5 mm), segment number (26–34), chaetae (enlarged in caudal segments), epidermal gland cells (few rows), origin of dorsal blood vessel (X–XII), position of preclitellar nephridia (3 pairs, 6/7–8/9), and sperm-related structures (small). G. oregonensis may also have a girdle-shaped clitellum, but the trait is described ambiguously and requires reinvestigation: "Clitellum ... in transverse rows ventrolaterally; reduced but complete ventrally between male pores" (ibd.: 775). The species differs in the absence of oesophageal appendages (present in G. cingulatus ) and in the extension over 2 segments of the intestinal diverticula (1 segment in G. cingulatus ). Specimens had been sampled from freshwater marsh soils in the estuary of the Columbia river (Oregon, U.S.A.), see Coates & Diaz (1988) for details.

Further similar species are G. rarus Černosvitov, 1937a emend. Coates & Diaz (1988), and G. s a w a y a i Righi, 1973. Both species, which may be synonymous ( Coates & Diaz 1988), differ from G. cingulatus in having a saddleshaped clitellum. Other differences are inconclusive and require a reinvestigation of the types.

Figures

FIGURE 3. Guaranidrilus cingulatus sp. nov. A. Segments IV – IX, lateral view. B. Anterior (left) and caudal (right) chaeta. C. Segments IV – VIII, dorsal to dorso-lateral view. D. Spermatheca. E. Clitellum dorsally. F. Preclitellar nephridium. G. Postclitellar nephridium. H. Male efferent apparatus. Male pore in ventral view. I. Male pore in lateral view, same specimen as in H. All drawings from whole mounts.

FIGURE 8. Schematic representation of taxonomic differences of species described here. The following traits are shown: Genus level: Chaetal pattern, shape of epidermal gland cells (eg, only shown in a few anterior segments, except in E), presence / absence of prostomial ganglion (g) in front of brain (br), prostomial papillae (p), and frontal recess in prostomial epithelium (r). Species level: Distribution of epidermal gland cells, pattern of secondary ventral pharyngeal gland lobes (pg), presence / absence of oesophageal appendages (oa) and intestinal diverticula (id), extension of the latter, distribution of preclitellar nephridia (ne). A. Guaranidrilus andreolii sp. nov., B. G. m a rq u e s i sp. nov. C. G. cingulatus sp. nov. D. G. h o e f e r i sp. nov. E. Xetadrilus maacki sp. nov. F. X. aphanus sp. nov. G. X. fabryi sp. nov.