Xetadrilus maacki, 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 : 16-18

Xetadrilus maacki sp. nov.

( Figs 5 , 8 E, Table 3 )

Holotype. MZUSP 1206, adult specimen, stained and whole-mounted in Canada balsam, Paranaguá, Palmito, 25°35'41.4''S 48°31'13.7''W, 3–11 m a.s.l., young secondary forest on Podzol [site 43], Mar 2004, leg. B. Förster, R. M. Schmelz.

Paratypes. MZUSP, 18 specimens, stained whole mounts:

MZUSP 1207, 6 specimens, same data as holotype.

MZUSP 1208, 12 specimens, Antonina, Cachoeira , 25°14’38“–19'21"S, 48°40’10“–42'08"W, 10–140 m a.s.l., medium old and old-growth forest on Cambisol and Gleysol [sites 10, 13, 28], May 2003, leg. J. Römbke & R. M. Schmelz.

UFPR, 8 specimens, stained whole mounts:

UFPR OL-18, 6 specimens, Guarequeçaba, Itaqui, 25°14'45.3''–15'32,7'S, 48°29'31.4''–30'31.9''W, 8 and 27 m a.s.l., medium old and old-growth forest on Cambisol [sites 38, 39, 41], Sep 2007, leg. P. Heine, R. M. Schmelz.

UFPR OL-19, 2 specimens, Antonina, Rio Pequeno, 25°14'39.3''S, 48°44'48.2''W, 40 m a.s.l., agroforestry system on Gleysol, banana monoculture [site 46], Jan. 2008, leg. J. Römbke, R. M. Schmelz.

Additional material. Three specimens from type locality, examined in vivo, not preserved.

Etymology. Named in honour of Reinhard Maack (1892–1969), German-Brazilian geographer and pioneer of environmental protection in Southern Brazil; seminal contributions to the physical geography of the state of Paraná (e.g., Maack 1968). Maack discovered the Xetá people in 1962. Vita in Fabry (2006).

Description. Individuals somewhat chequered, transparent and milky/opaque body regions; coelom more or less free, inner structures well-distinguished. Body dimensions. Living adult specimens ca. 4 mm long and 0.1– 0.12 mm wide, widest in clitellar region; fixed specimens 3–3.5 mm long and 0.12–0.18 mm wide. Segment number 21–28 in adults and subadults, most often 25–27 (N = 16), holotype 27. Subadults with <20 segments have a posteriorly severed or a regenerated posterior end. Chaetae ( Fig. 5 E,H) two per bundle, formula 2,0–0: 2–2. Lateral chaetae present in II–VII, absent from VIII on. Ventral chaetae from II on, absent in XII. Anterior chaetae faintly sigmoid, with slight proximal bend and almost straight distal tip, ventrally ca. 32–38 μm long and 3 μm wide, laterally smaller, dimensions not measured. Behind clitellum chaetae increasing in size towards posterior end, twice as large as anterior chaetae in ca. 8 hindmost segments, here 64–70 μm long and 6–6.5 μm wide. Chaetae slightly shifted posteriad with respect to septa, ratio of distance to anterior and posterior septum, respectively, about 4:3. Epidermal gland cells ( Fig. 5 A,G) absent except mid-ventrally between chaetal bundles; here 2–3 large, transversely arranged gland cells with finely granular content (fix), present in all segments, XII included; cells 2x as high as epidermis, larger posteriorly than anteriorly. Clitellum ( Fig. 5 C) saddle-shaped, i.e. absent ventrally. Cells in ca. 31 separate (viv) or dense (fix) rows; hyalocytes not in longitudinal rows, present only in dorsal half, extending further ventrally in the middle than at the ends; cells roughly rectangular in living specimens, with hyalocytes larger than granulocytes (diameters ca. 11 µm vs. 8 µm (viv) or 10–12 μm vs. 6 μm (fix)); ventro-laterally only granulocytes. Cells about as high as wide. A few cells present between male copulatory organs, of same type as in other segments between ventral chaetal bundles. Prostomium ( Fig. 5 A) with head pore in mid-dorsal position, slit transverse.

Frontal prostomial epithelium ( Fig. 5 A,B) thickened, with a recess or cleft at the frontal tip. Dorso-laterally six inner prostomial papillae in bilateral-symmetrical order. Prostomial musculature well-developed. Body wall thin, between 3 and 12 μm thick, cuticle <1 μm thick, layer of epidermis plus ring muscles 1–2 μm thick, longitudinal muscle layer well-developed, more so ventrally than dorsally. Septa slightly thickened in preclitellar segments (fix), difference inconspicuous in vivo. Brain incised posteriorly, sides converging anteriad. A pair of bilobed prostomial ganglia present on prostomial nerves. Perikarya of II–IV fused into suboesophageal ganglion, segmental ganglia present from V on, no perikarya at the level of the septa except in hindmost segments; here segmental ganglia interconnected by a thin strand of perikarya at level of septa. Pharyngeal glands ( Fig. 5 A,B) with three unpaired dorsal lobes in IV–VI, thickest in the middle, all alike; two pairs of primary ventral lobes, in V and VI; three pairs of secondary ventral lobes, in V, VI, VII, increasing in size posteriad. Oesophageal appendages and intestinal diverticula absent. Gut widening abruptly in VII ( Fig. 5 A), gradually tapering posteriorly. Epithelium thickened in VII and VIII, cells enlarged, with fine pale vesicular content. Chloragocytes from V, a dense and flat layer (cell height ca. 5 µm) from VII, inconspicuous. Dorsal vessel from XIII or XIV; anterior bifurcation prostomial. Pars tumida of midgut over 1–2 segments, from 1/2 XVII – 1/ 2 X, epithelium strongly proliferated. Preclitellar nephridia ( Fig. 5 G) two pairs in preclitellar segments, at 7/8 and 8/9, not constricted at septum. Anteseptale with parts of nephridial body, longer than wide, funnel attached obliquely. Postseptale larger than anteseptale, length ratio 3:2, with a dorsal bump in mid-section, no vesicle here; nephridial canal apparently with an 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, altogether 8–10 in number. Example, holotype: 13/14 (paired), 18/19 (paired), 20/21 (unpaired left side), 24/25 (unpaired right side), 25/26 (paired). Nephridia elongate, no dorsal bump in mid-section of postseptale, no vesicle, efferent duct short, rising terminally. Coelomocytes ( Fig. 5 F) distinctly brownish in vivo, with small spherical and refractile vesicles; vesicles clearly separate from each other, like dots, conspicuous. Cells slightly longer than wide, almost spherical, ca. 25 µm long. In fixed and dehydrated material cytoplasma pale and homogeneously vesicular, nucleus central, conspicuous.

Seminal vesicle absent. Spermatozoa conspicuous on top of sperm funnel when present, ca. 39 µm long, heads ca. 14 µm long. Sperm funnel ( Fig. 5 H) small, 1/4–1/3 as long as body diameter, 1.5–2 as long as wide; collar distinct, not or only little widened and ca. 15 µm high, contributing to almost 1/3 of total sperm funnel length; funnel body variable, either barrel-shaped, not wider than collar, or almost globular, canal opening funnel-like towards proximal end. Vas deferens in dense coils ventro-laterally, ca. 4 µm thick, wider immediately behind sperm funnel (ca. 6 µm). Male copulatory organ ( Fig. 5 H): male pores on body surface in longitudinal line of ventral chaetae, at half distance between chaetae of XI and XIII; each pore surrounded by a small glandular bulb interspersed with musculature, bulb small, roughly spherical, diameter ca. 20 µm, outline irregular, occasionally with small extra-bulbs anteriorly and posteriorly; bursa apparently absent, transverse copulatory body muscles sparse, three strands in front of male pore, posteriorly inconspicuous or absent. Accessory glands absent. Spermatheca ( Fig. 5 D) a small and proximally blind-ending tube, not attached to oesophagus, confined to V; ectal pore in lateral line, at half-length between chaetae of IV and V; ectal duct and ampulla of about equal length; ectal duct with smooth outline, isodiametric, ampulla not wider than ectal duct but with irregular outline, thin-walled. Small amount of sperm in ampullar distal part. Eggs. One or two mature eggs at a time.

Habitat. X. maacki was found at all successional stages of forest regeneration and also in pastures and at agroforestry sites.

Remarks. Key characters of Xetadrilus maacki are: (1) Brown coelomocytes; (2) gut widening abruptly in VII, no intestinal diverticula; (3) chaetae in terminal segments large, thick, sigmoid; (4) segmental mid-ventral epidermal gland cells. For a comparison with other congeneric species, see Tables 2 and 3 .

Figures

FIGURE 5. Xetadrilus maacki gen. nov. sp. nov. A. Anterior body end, lateral view. B. Anterior body end, dorsal view. C. Segments XI – XIV, latero-ventral view. D. Spermatheca. E. Posterior body end with anus, lateral view. F. Coelomocyte. G. Preclitellar nephridium. H. Sperm funnel and ventral body wall with chaeta (XI), male glandular bulb and transverse copulatory muscles. dp, dorsal pore; fr, frontal recess in prostomial epithelium.

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.