Guaranidrilus hoeferi, 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 : 10-13

Guaranidrilus hoeferi sp. nov.

( Figs 4 , 8 D)

Holotype. UFPR OL-13, adult/subadult specimen, stained whole mount, Guarequeçaba, Itaqui, 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.

Paratypes. MZUSP, 6 specimens, Antonina, Cachoeira , stained whole mounts:

MZUSP 1230, 2 specimens, 25°14'38'', 48°40'10'', 140 m a.s.l., old-growth forest on Cambisol [site 13], May 2003, leg. J. Römbke, R. M. Schmelz.

MZUSP 1231, 4 specimens, 25°19'00"S, 48°40'14"W, and 25°19'41"S, 48°40'36"W, 30 and 120 m a.s.l., abandoned pasture and medium old secondary forest on Cambisol [sites 6, 12], Oct 2004. leg. B. Förster, R.M. Schmelz.

UFPR, 44 specimens, Guarequeçaba, Itaqui, stained whole mounts (35) and ethanol-preserved (9):

UFPR OL-14, 5 specimens, same data as holotype.

UFPR OL-15, 13 specimens, 25°15'43.8''S, 48°29'14.8''W, ca. 20 m a.s.l., young forest on Cambisol [site 36], Sep 2007, leg. P.Heine, R. M. Schmelz.

UFPR OL-16, 17 specimens, 25°15'32.7''S, 48°30'31.9''W and 25°16'23.7''S, 48°29'13.7''W, 20 and 31 m a.s.l., respectively, old-growth forest on Cambisol [sites 41, 42], Sep 2007, leg. P.Heine, R. M. Schmelz.

UFPR OL-17, 9 specimens, ethanol-preserved.

Additional material. Fifteen specimens from sites in Itaqui, examined in vivo, not preserved.

Etymology. Named in honour of Hubert Höfer (State Museum of Natural History, Karlsruhe), initiator and German coordinator of the SOLOBIOMA project, in grateful recognition of the tremendous amout of work to launch and to maintain this project, which allowed the discovery and description of so many enchytraeid species.

Description. Slow body movements. Body dimensions. Mature specimens about 12–15 mm long in vivo, live diameter ca. 0.2 mm, submatures often distinctly smaller (<8 mm). Segment number 39–48. Chaetae distally straight, with weak proximal hook, not thickened proximally. Preclitellar chaetae small and stout, ca. 22–28 µm long and and 2.5–3 µm thick. Postclitellar chaetae behind clitellum small and inconspicuous, ca. 20 µm long and 2 µm wide; chaetae increasing gradually in size towards posterior end. In caudal segments chaetae stout again, 40–50 µm long and 6 µm thick. Epidermal gland cells inconspicuous in vivo. In whole mounts all epidermis apparently glandular, cells transversely elongate, hyaline, in about 11 rows per segment, almost continuous except mid-ventrally. Clitellum ( Fig. 4 H) saddle-shaped, not developed ventrally; on dorsal half granulocytes and hyalocytes, granulocytes isolated, hyalocytes large, seen as large free interspaces in living specimens; ventro-laterally only granulocytes. On dorsal half cells in indefinite rows or reticulate; latero-ventrally cells in dense rows. In adults accessory glands present, a glandular thickening of the epidermis mid-ventrally in XIII or in XI and XIII, immediately in front of and behind clitellum ( Fig. 4 A,K); glandular field between the ventral chaetae and the respective posterior septum. Head pore on prostomium mid-dorsally.

Prostomium without inner papillae. Pygidium with strongly developed rectal musculature, filling body cavity. Body wall thin (ca. 10–20 µm), ring muscles in one regular layer. Cuticle mostly thick compared to rest of body wall (up to 9 µm), thicker than epidermis + ring muscle layer. Anterior septa not thickened. Brain posteriorly concave; a few perikarya on prostomial nerves, no ganglionic swelling. Pharyngeal glands ( Fig. 4 A,B) in IV–VI, unpaired and fused dorsally; dorsal lobes of V and VI with ventral anterior projections (primary ventral lobes), large in VI, small in V; secondary ventral lobes present in V and VI, spherical. Oesophageal appendages ( Fig. 4 A,B) paired dorso-laterally in anterior half of VI, elongate, with irregular outline. Intestinal diverticula ( Fig. 4 A,B) in VII, as pouches with wide lumen, directed anteriad, i.e. connection with intestine posteriorly; walls with radial striation, possibly folds of inner wall; chloragocytes present on outer surface. Dorsal blood vessel ( Fig. 4 A,B) from 1/ 2 VIII, pulsating. Preclitellar nephridia ( Fig. 4 A,B,I) two pairs, at 7/8 and 8/9. Anteseptale large, with coils of canal, outline spherical in side view, postseptale elongate and narrower than anteseptale, with dorsal vesicle, gradually merging into short and stout efferent duct, no terminal vesicle. Postclitellar nephridia ( Fig. 4 J) of similar shape but slightly longer, anteseptale longer than wide. Nephridia missing at several positions. Coelomocytes ( Fig. 4 G) numerous, darkened in aggregations. Cells flattened, outline broad-oval, length ca. 20–40 µm. A few dark and refractile granules of irregular outline scattered in a finely and regularly vesicular, pale-brown matrix.

Seminal vesicle ( Fig. 4 A) large, extending over up to 5 segments, caused by forward bulge of septum 10/11 and backward bulge of septum 11/12. Spermatozoa very numerous, heads 33 µm long (measured in vivo). Sperm funnel ( Fig. 4 A) longer than body diameter, ca. 2x as long as wide (or longer), tapering distally; collar conspicuous, with free extensions beyond funnel body, often U-shaped, conspicuous by attached sperm. Each extension may have stump-like sub-lobes. Vas deferens ( Fig. 4 A) very long and irregularly coiled, of equal diameter throughout (8 µm in fixed material. Male copulatory organ ( Fig. 4 A) with male pores on body surface, each withdrawn in a longitudinal eversible furrow; both furrows creating a mid-ventral "penial plate" when withdrawn. In all fixed specimens furrows everted into elongate-conical projections; male pores widely separate, distance wider than distance between ventral chaetal bundles of a segment. No male glands around male pore, but epidermis thickened here and also in a field between the pores, the "penial plate". Copulatory muscles ( Fig. 1 A) conspicuous in preserved specimens as a parasagittal series of fine, dorso-ventral strands, arranged in paralles (side view): ventral insertion of muscles at inner wall of papilla, dorsal insertion at inner body wall surface latero-dorsally, slightly above longitudinal row of lateral chaetae. Spermatheca ( Fig. 4 A,C,D,E,F) very large, extending into IX. Ectal duct short, distal part of ampulla conspicuous, thin-walled, with sperm and surrounding free lumen; ental reservoir extending over 3 segments, into IX, here elongately club-shaped, thick-walled; walls with large, non-staining inclusions of irregular outline ( Fig.4 F, "se"); lumen completely filled with spermatozoa, forming a long, compact and iridescent strand. One egg at a time seen, but no specimen with fully developed egg found.

Habitat. G. hoeferi was found at all stages of forest regeneration. It was absent in pastures and only one specimen was found at the agroforestry sites.

Remarks. Among all species present at the study sites, G. hoeferi was instantly distinguished by (1) the peculiar coelomocytes. Further traits that confirmed the identification were: (2) only 2 pairs of anterior nephridia, at 8/9 and 9/10, (3) dorsal blood vessel from VIII, (4) intestinal diverticula confined to VII, mostly directed forwards. With this character combination, specimens of all age stages, including very small juvenile ones, could be identified. The striking gigantism of sperm-related organs is shared by several other Guaranidrilus species that possess oesophageal appendages ( G. atlanticus Christoffersen, 1977 , G. cernosvitovi Healy, 1979 , G. joanae Christoffersen, 1977 , G. m b o i Righi, 1975), and hence is little help in the identification of the species.

G. hoeferi is most similar to G. joanae Christoffersen, 1977 , another species of the Brazilian Atlantic rain forest, found ca. 250 km up north-east near the city of São Paulo. Both may be indeed be sister species; at least they belong to a common sub-group or clade within the genus. The excellent original description of G. joanae allows a detailed comparison. Both species agree in body size, behaviour, all details of pharyngeal glands, oesophageal appendages, intestinal diverticula, and in size and organization of spermathecae and the entire male reproductive system. They differ in four traits: (1) In G. joanae , chaetae are enlarged not only in caudal segments but also in the most anterior segments, and here (2) the ental bend is thickened in a claviform manner. (3) Preclitellar nephridia are present not only at 7/8 – 8/9 but also at 6/7, resulting in three preclitellar pairs instead of the two in G. hoeferi . (4) Coelomocytes of G. joanae appear to lack the conspicuous double texture present in G. hoeferi (few coarse granules embedded in a densely and finely vesicular pale-brown matrix), they are described as being "rather inconspicuously granulated" ( Christoffersen 1977: 200). Furthermore segment number is slightly higher (49–55) and clitellar gland cells are irregularly arranged in G. joanae , but our specimens were not fully mature. Our specimens were relaxed and Christoffersen's specimens apparently contracted at the time of fixation, which may account for differences in body length (10–11 mm in G. joanae ) and shape of preclitellar nephridia (efferent duct bent forwards in G. joanae ). Epidermal gland cells are said to be slightly developed in G. joanae ( Christoffersen 1977: 198) , but the animals "... were always found enveloped in great amounts of mucus..." (ibid.), which suggests the same situation as in G. h o e f e r i: numerous glands cells, inconspicuous in vivo. In fact even in fixed material the glands are invisible unless interference contrast optics are used. The ectal pore of the spermathecae of G. joanae appears to be located ventrally in a figure ( Christoffersen 1977, Fig. 24), but the description gives the usual and probably correct lateral location.

Figures

FIGURE 1. Guaranidrilus andreolii sp. nov. A. Anterior end, dorsal view. Note three pairs of postpharyngeal ganglia anterior to pharyngeal glands. B. Epidermal gland cells, dorso-lateral view, segments XXXI – XXXIII. C. Nephridia, left: preclitellar segment; right: two nephridia in one segment, seen at different optical angles. D. Sperm funnels, seen at different optical angles. E. Male efferent apparatus and clitellum, latero-ventral view. F. Anterior end, lateral view, with indication of extension of prostomium and segments I – III. Dotted lines: course of transverse lines of epidermis and transverse musculature in I – 1 / 2 II, schematic. Segment I, the peristomium, is longer dorsally than ventrally. The head pore, though seemingly near the tip of the prostomium, is actually located at its posterior end. All drawings from whole mounts. g, prostomial ganglion; ppg, post-pharyngeal ganglia; pvl, primary ventral pharyngeal gland lobe; svl, secondary ventral pharyngeal gland lobe.

FIGURE 4. Guaranidrilus hoeferi sp. nov. A. Anterior 13 segments, lateral view. Shaded grey: Spermatheca (left), spermfilled seminal vesicle (right). Specimen submature with small egg. The seminal vesicle can extend over 2 more segments. B. Segments IV – VIII, dorsal view. C – F and H, K show details of A. C. Spermatheca, ectal duct and ectal dilatation of ampulla. D, E. Spermatheca, connecting tube. In D the epithelium is cylindrical; sperm is present as a central strand in the lumen. In E sperm is embedded in epithelium with undulating inner walls. F. Histological section (optical longitudinal section) from body surface to inner lumen of spermatheca; cl, coelom; ct, cuticle; eg, epidermal gland cells; lm, longitudinal muscles; rm, ring muscles; se, epithelium of spermathecal ental dilatation with inclusions of irregular outline; sp, sperm in lumen of ental dilatation. G. Coelomocytes. H. Detail of clitellum, lateral view. I. Preclitellar nephridium. J. Postclitellar nephridium. K. Detail of copulatory pad in XIII, optical longitudinal section. G from living specimens, rest 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.