Xetadrilus fabryi, 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 : 20-23

Xetadrilus fabryi sp. nov.

( Figs 7 , 8 G, Table 3 )

Holotype. UFPR OL-23, adult specimen with 22 segments, posterior end regenerated, stained whole mount, Antonina, Rio Pequeno, 25°15'56.8''S, 48°44'23.5''W, 25 m a.s.l., agroforestry system [site 48], Jan 2008, leg. J. Römbke, R. M. Schmelz.

Paratypes. MZUSP, 4 specimens, stained whole mounts, Antonina, Cachoeira :

MZUSP 1215, 3 specimens, 25°15'2''S, 48°40'24'' and 25°15'13''S, 48°40'34''W, 30 and 40 m a.s.l., respectively, pasture, partly abandoned, on Cambisol [sites 1, 4], May 2003, leg. J Römbke, R. M. Schmelz.

MZUSP 1216, 1 specimen, 25°18'25"S, 48°40'24"W, 70 m a.s.l., pasture on Cambisol [site 2], March 2004, leg. B. Förster, R. M. Schmelz.

UFPR, 8 specimens, stained whole mounts:

UFPR OL-24, 5 specimens, Antonina, Rio Pequeno, 25°15'56.8''–16'23.4''S, 48°43'41.1''–44'23.5''W, 15 and 25 m a.s.l., respectively, agroforestry system [sites 47, 48], Jan 2008, leg. J. Römbke, R. M. Schmelz.

UFPR OL-25, 3 specimens, Curitiba, UFPR University Campus, Agrárias, 25°24'37''S, 49°14'56''W, 909 m a.s.l., grassland, Feb 2008, leg. R. M. Schmelz.

Additional material. One specimen from UFPR campus, Agrarias, examined in vivo, not preserved.

Etymology. Named in honour of Rainer Fabry, versatile German on-site coordinator of the SOLOBIOMAproject.

Xetadrilus maacki Xetadrilus aphanus Xetadrilus fabryi

Segment number 21–28 21–28 33

Description. Body dimensions. Living adult specimens ca. 3 mm long and 0.11–0.12 mm wide, whole mounts 2.5–3.5 mm long and 0.1–0.12 mm wide, up to 0.16 at XII. Segment number 30–33 (N=3), holotype 22 segments, with regenerated posterior end. Chaetae 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. Chaetae distally straight, or slightly bent to same side as proximal bend. Terminal chaetae enlarged, almost 2x as large as largest anterior chaetae, not sigmoid. Ventral anterior chaetae ca. 2 µm thick, in II 12 µm long, gradually increasing in size posteriad to about 28 µm in IX. Ventral chaetae in hindmost segments 45–55 µm long and 2.5–3 µm thick. Epidermal gland cells ( Fig. 7 B) variable; entire epidermis glandular to varying degrees, gland cells pale and evenly distributed, or no epidermal gland cells distinguishable in living and preserved material. In specimens with glandular epidermis body surface often covered with foreign particles. Clitellum saddle-shaped, cells in ca. 25 transverse rows, separate (viv) or dense (fix). Hyalocytes on dorsal half, larger than granulocytes, isolated; in ventral half only granulocytes, mid-ventral interruption as wide as distance of male pores. Prostomium with head pore in mid-dorsal position.

Frontal prostomial epithelium ( Fig. 7 A,E) thickened, with a vesicle-like recess or cleft at the frontal tip. Dorso-laterally several inner papillae in bilateral-symmetrical order, inner papillae also on peristomium. Prostomial musculature present. Body wall medium-thick, cuticle thin. Preclitellar septa not thickened. Brain ( Fig. 7 E) in I–III, 2–2.5x as long as wide, incised posteriorly; prostomial ganglia conspicuous but small; ventral nerve cord with suboesophageal ganglion in II–IV and segmental ganglia from V. Oesophageal appendages absent. Pharyngeal glands ( Fig. 7 A,B) as unpaired dorsal lobes in IV–VI, voluminous in IV and V, primary ventral lobes in V and VI, largest in VI; small and spherical secondary ventral lobes in V, VI and VII. Intestinal diverticula ( Fig. 7 A,B) one pair in VII, elongate, oval, thick-walled, with distinct lumen; placed laterally of intestine, arranged in "V"- shape (dorsal view), slightly diverging anteriad; diverticula laterally flattened, higher than wide. Chloragocytes often black-grey in posterior segments. Dorsal blood vessel from 1/2 XIV in the two mature and complete specimens, from 1/4 XIV in holotype; the origin was difficult to see in living specimens. Preclitellar nephridia ( Fig. 7 C) 3 pairs, from 7/8 to 9/10, postseptale without dorsal vesicle. Postclitellar nephridia elongate. Coelomocytes pale, not hyaline, without conspicuous texture.

Seminal vesicle absent. Spermatozoa distinct on top of sperm funnel, length not measured in vivo. Sperm funnel ( Fig. 7 F) barrel-shaped, ca. 1/3 as long as body diameter (40–50 µm long, fix), collar not wider than funnel body. Vas deferens ( Fig. 7 F) quite long, coiled densely in numerous loops in XII, sometimes filling entire dorsal half of segment XII; diameter 4 µm throughout except near sperm funnel, here ca. 5 µm (fix). Male copulatory organ ( Fig. 7 F) small, circular in top view, not more than a body wall thickening in side view; bursa and bursal slit apparently absent; male pore on body surface, sometimes surrounded by folds. Glandular bulb tripartite, an eversible central bulb, diameter ca. 20 µm (fix), pierced centrally by vas deferens, and two smaller bulbs attached anteriorly and posteriorly. Copulatory muscles well-developed, encompassing bulbs and also extending dorsad as transverse copulatory muscles. Accessory glands absent. Spermathecae ( Fig. 7 A) not attached to oesophagus, a simple tube. Ectal duct short (length 20 µm, diameter 10 µm, fix) with wide lumen, often filled with sperm, gradually widening into distal part of ampulla, here sperm arranged in parallel, or no ampulla distinguishable. The following tube narrow (diameter ca. 5 µm, fix), widening into thin-walled ental reservoir in VI or VII; reservoir not always developed. Sperm may be present in any part of the spermatheca. One mature egg at a time.

Habitat. X. fabryi was found in grazed and abandoned pastures and at agroforestry sites. It was not found at forest sites.

Remarks. This is the only species of the new genus with intestinal diverticula. Diverticula are similar in shape to the ones in Guaranidrilus joanae Christoffersen, 1977 and G. hoeferi sp. nov. (see above). The two Guaranidrilus species are much larger and with very large sperm-related sexual organs. X. fabryi has been assigned to Xetadrilus (and not to Guaranidrilus ) by virtue of the following characters: (1) Lateral chaeta absent from VIII, (2) epidermal gland cells oval, not transversely elongate, (3) prostomium with inner papillae and ganglia, (4) nephridia without dorsal vesicle, (5) pharyngeal glands with secondary lobes not only in V, VI, but also in VII, (6) post-clitellar origin of dorsal blood vessel.

Figures

FIGURE 7. Xetadrilus fabryi gen. nov. sp. nov. A. Anterior body end, dorsal view. B. Segments III – X, lateral view. Epidermal gland cells are shown only in III and IV. C. Anterior nephridium. D. Posterior nephridium. E. Head reagion, dorsal view. Shaded grey: body wall, and its papillae. F. Male efferent apparatuses; sperm funnel and vas deferens omitted once.

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.

Tables

TABLE 3. Differences betweeen the three new species of Xetadrilus gen. nov. Idiosyncrasies underlined.

Posterior chaetae	sigmoid, 2x as large as anterior	straight, 1.5–2x as large as anterior	straight, c. 1.8 x as large as anterior
Epidermal gland cells	mid-ventrally only	absent or all epidermis glandular	absent or all epidermis glandular
Prostomial ganglia	large	large	medium
Preclitellar nephridia	2 pairs, 7/8, 8/9	2 pairs, 7/8, 8/9	3 pairs, 7/8 – 9/10
Pharyngeal glands, dorsal lobes in VI	united	separate	united
Pharyngeal glands, ventral secondary lobes	at V–VII, increasing in size posteriad	at V–VII	V–VII, all small and spheri- cal
Intestine in VII	widened	widened	diverticula
Dorsal blood vessel	from XIII – XIV	from 1/2 XII – XIII	from XIV
Coelomocytes	distinctly brown, with refractile vesicles	with pale vesicles, aggre- gations pale or brownish	with pale vesicles, aggregations rarely with brownish tint
Further idiosyncrasies		Pharyngeal glands in VI– VII "Z"-shaped