Hemienchytraeus siljae, Schmelz, R. M. & Römbke, J., 2005

Schmelz, R. M. & Römbke, J., 2005, Three new species of Hemienchytraeus (Enchytraeidae, Oligochaeta) from Amazonian forest soil, Journal of Natural History 39, pp. 2967-2986 : 2971-2973

Hemienchytraeus siljae sp. nov.

(Figure 1)

Type material

Holotype: INPA 121, fully mature specimen, stained and whole-mounted. Paratypes: INPA 122, one specimen, submature, with severed posterior end; ZIM OL 14281, one specimen, fully mature. All types from a sample collected in December 1997.

Further material investigated

Three mature specimens, examined alive, not conserved.

Description

Length 10-12 mm (viv) or 8-11 mm (fix), diameter (fix) ca 0.3 mm, up to 0.35 mm in XII. Segment number 43-45. Two chaetae per bundle throughout, present laterally in XII also in mature specimens. Chaetae (Figure 1B, I) slightly sigmoid, without nodulus, pointed distally, blunt proximally; ventral chaetae distinctly larger (longer and thicker) than lateral chaetae; chaetae in posterior segments much larger than chaetae in anterior segments; lateral preclitellar chaetae 37-47 µm long, 3-4 µm thick, increasing in posterior segments from 40 x 3 µm (XIII) up to 85 x 7 µm in terminal segments; ventral preclitellar chaetae 40-65 µm long and 4-4.7 µm thick; gradually increasing in posterior segments up to 90 x 9 µm in terminal segments. Head pore (Figure 1A) on prostomium in form of a small transverse slit. Epidermal gland cells (Figure 1A): in preclitellar segments, four to five segmental rows of transversely elongate, quasi-rectangular cells; most cells situated laterally, few cells mid-dorsally and mid-ventrally. First segment and part of prostomium densely covered with cells; in postclitellar segments one to three rows per segment, with fewer cells than in preclitellar segments.

Clitellum (Figure 1C) in XII– 1/2 XIII, posterior end of clitellum immediately before chaetae of XIII dorsally and at level of chaetae of XIII latero-ventrally; clitellum present on all sides except in posterior half of mid-ventral part; cellular arrangement in indistinct rows to reticulate; mid-ventrally (anterior half) in dense rows, irregularly warty between bursal slits. On dorsal body half, hyalocytes and granulocytes present, hyalocytes (diameter 10- 19 µm, height 16 µm, fix) larger than granulocytes (diameter 5-8 µm), the latter inconspicuous, occupying interspaces between hyalocytes. Ventro-laterally only granulocytes, here clitellum thinner.

Body wall 15-25 µm thick (fix), cuticle 1-1.5 µm thick (fix), always distinct at x 250 magnification, longitudinal muscle layer well developed, 10-20 µm thick. Preclitellar septa not thickened. Brain (Figure 1A) about as long as wide, or shorter (measured dimensions: 66 x 66 µm and 70 x 82 µm, fix), deeply incised anteriorly, slightly indented posteriorly, sides parallel. Post-pharyngeal bulbs (Figure 1A, pb) conspicuous. Ventral nerve cord perikarya concentrated in segmental ganglia from V on, i.e. no perikarya in the region of the septa. Oesophageal appendage (Figure 1A) with long unpaired root, reaching pharyngeal glands of IV, short primary branches and about four to five elongate secondary branches on each side. Large proximal chamber present. Primary branches thinner than unpaired trunk and thicker than secondary branches. Pharyngeal glands (Figure 1A) widely connected dorsally in IV, with narrow dorsal connection or separate in V, glands dorsally separate in VI. Three pairs of secondary ventral lobes, in V, VI, and VII, smallest in VII. Afferent fascicles (Figure 1A, af) comparatively thick. Chloragocytes from V. Dorsal vessel from XIV to XV. Inflated ventral gut epithelium from XXIII to XXX, extending over six or seven segments.

Nephridia (Figure 1A, G-I). Preclitellar segments: four pairs, in 6/7-9/10, anteseptale globular, with minute and numerous brownish granules at periphery; funnel orientated obliquely ventrad, with small and narrow anterior projection; postseptale twice as long as anteseptale (total lengths measured 85-116 µm, fix), adseptal to medial origin of efferent duct. Postclitellar segments: first pair at 14/15; number of nephridia reduced in mid-body region, slightly larger than preclitellar nephridia (length ca 140 µm, fix); nephridia in terminal segments more numerous, small, about half as long (ca 50-55 µm, fix) as preclitellar nephridia; postseptale compressed, bulged dorsad, rise of efferent duct terminal. Coelomocytes flat and broadly oval, with central nucleus and finely granular matrix (viv), 15-30 µm long (fix), large cells 1.5 x as long as wide, small cells with circular outline.

Seminal vesicle very small or absent; a small, dense, conspicuous aggregation of developing sperm present around the sperm funnel collars. Sperm funnel (Figure 1E, F) about as long as body diameter, 4-6 x as long as wide (viv); funnel body cone-shaped, gradually and regularly tapering distad (e.g. from 65 to 20 µm, fix), broadly oval in crosssection, not circular; collar flared, wider than funnel body in mature specimens (up to 1.5 x as wide), outline wavy, irregular, like a brim, conspicuous by dense masses of attached spermatozoa. Spermatozoa at least 125 µm long (viv), head lengths not measured. Vasa deferentia in XII, in loose or tight irregular coils, diameter tapering from 13 proximally to 8 µm distally, entering male copulatory organ dorsally. Male copulatory organs with strongly developed musculature. Male glandular body globular, diameter ca 55 µm (fix). Bursa laterally flattened, short, extending halfway dorsad into glandular body; bursal slit (Figure 1C, D) longitudinal, slightly bent, tips curved outward. Musculature strongly developed (Figure 1D), surrounding glandular body and obscuring its outline in living specimens; muscle system complicated, extending over entire segment of XII; dense aggregations of strands anteriorly, posteriorly, laterally and dorso-laterally of glandular bulb; orientation of strands mainly from dorso-lateral to mid-ventral; some strands connecting glandular body and body wall, some strands connecting dorso-lateral and mid-ventral side of body wall in a regular pattern. In two specimens, aggregations of hyaline bodies of varying size and with smooth outline interspersed between the muscular strand concentrations. No accessory copulatory glands present.

Spermathecae (Figure 1A) not attached to oesophagus, extending into VI, VII or VIII, each consisting of ectal duct and ampulla, the latter subdivided into ectal dilatation, connecting tube and ental reservoir. No ectal gland, epidermis thickened in a small circular field (diameter twice the ectal duct diameter) around ectal pore; thickening projecting inside. Ectal pore 3 µm wide (fix), distalmost stretch of ectal duct canal 4-5 µm wide (fix), lined with cuticle for about 25 µm; further proximally, cuticle light-microscopically not distinguishable; canal often inconspicuous here; ectal duct about one segment length long; ectal dilatation of ampulla 16-30 µm wide (fix), ca twice as wide as ectal duct; connecting tube about as wide as ectal duct; ental reservoir thin-walled, usually bent dorsad, of varying length (one or two segments) and width (35-80 µm). Sperm present in ectal dilatation and ental reservoir; in ectal dilatation, sperm arranged side-by-side in a wisp with nuclei orientated distad and flagella extending straight into proximal tube; in ental reservoir, spermatozoa arranged in a dense and irregular coil. One mature egg at a time.

Remarks

One paratype specimen has slightly reduced pharyngeal glands in VI.