Hemienchytraeus patricii, 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 : 2973-2976

Hemienchytraeus patricii sp. nov.

(Figure 2)

Type material

Holotype: INPA 123, mature specimen, coll. December 1997. Paratypes: INPA 124, 13 specimens, 11 mature, two submature, coll. December 1997. ZIM OL 14282, 13 specimens, 11 mature, two submature, coll. December 1997 (eight specimens), March 1998 (five specimens). All types stained and whole-mounted.

Further material investigated

Three mature specimens, ZIM OL 14283, stained whole mounts, with abnormal pharyngeal glands, one of them infected by parasites.

Description

Slim and active worms, body transparent, due to thin body wall and sparse coelomocytes. Body length ca 7-8 mm (viv) or 5-7 mm (fix); diameter 0.2-0.23 (-0.25) mm (viv, fix). Segment number (28) –31–34– (35). Two chaetae per bundle throughout, present laterally in XII also in mature specimens. Chaetae sigmoid without nodulus, pointed distally, blunt proximally, proximal bend stronger than distal curve. Chaetae in preclitellar bundles 25- 35 µm long, smallest in II, gradually increasing in length posteriad, diameter ca 3 µm; lateral and ventral chaetae of equal size. Chaetae in postclitellar bundles gradually increasing in size towards rear end, size increase much more pronounced in ventral than in lateral bundles. In terminal segments ventral chaetae 70-80 µm long and 7-8 µm thick, lateral chaetae ca 50 µm long and 5 µm thick. Head pore (Figure 2A, B) on prostomium in form of a small transverse slit. Epidermal gland cells numerous in first four segments including prostomium; cells in up to seven rows per segment, cells transversely elongate except at chaetal level; here cells about as long as wide, larger than in adjacent rows; posteriorly fewer cells, quasi-rectangular. No cells mid-ventrally in II–IV; from V on quasi-rectangular square cells present.

Clitellum (Figure 2C, D) short, covering little more than one segment length: anterior margin behind septum 11/12, immediately before male copulatory organ, posterior margin at some distance before chaetae of XIII. Clitellum saddle-shaped, not developed mid-ventrally. Ventral clitellar margins (i.e. the width of the cell-free ventral area) marked by the bursal slits. Cellular arrangement in two distinct patterns. (1) In dorsal half, down to the longitudinal level of lateral chaetae, hyalocytes and granulocytes present. Hyalocytes 2-3 x as large (diameter) as granulocytes, but not more numerous than the latter; cellular arrangement reticulate, no transverse orientation. Cells about as high as wide, higher than wide when fully developed (12-18 µm, fix). (2) Ventro-laterally, in a field between the longitudinal level of lateral chaetae to that of bursal slits, only granulocytes present, cellular arrangement in transverse rows, cells less elevated than in dorsal body half. Each bursal slit surrounded by a field with stronger staining nuclei; this area not marked in living specimens.

Body wall usually 6-12 µm thick (viv, fix), cuticle thin, often invisible. Body wall thicker laterally and ventrally in anterior seven segments and ventrally in terminal segments with enlarged chaetae, here up to 25-30 µm thick (fix). Preclitellar septa not thickened. Brain (Figure 2A, B) about as long as wide or longer (55-77 µm x 48-64 µm, fix), incised anteriorly, sides parallel or slightly converging anteriad, posteriorly slightly indented or truncate. Post-pharyngeal bulbs inconspicuous. Ventral nerve cord perikarya concentrated in segmental ganglia from V on, i.e. no perikarya in the region of the septa. Oesophageal appendage (Figure 2A, B): unpaired root with large proximal chamber; following section longer than proximal chamber, with thick, meandering canal; first bifurcation into primary branches immediately anteriorly of dorsal pharyngeal glands of IV; primary branches shorter that unpaired root; numerous secondary branches of different length and thickness, difficult to distinguish, often compacted into a thickened cauliflower-like mass. Pharyngeal glands (Figure 2A, B) in IV–VI, with single unpaired dorsal lobe in each segment, and primary ventral lobes in V and VI; small secondary ventral lobes present in V and VI. Dorsal lobe large in IV and V, smaller in VI, connection between dorsal lobe and ventral lobes wide in V, narrow in VI. Primary ventral lobes in VI distinctly projecting anteriad, ventral lobes in V not or only slightly projecting anteriad, compared to dorsal lobe. Chloragocytes flat, beginning in V, absent in XI and XII. Dorsal blood vessel originating in XIII–XIV. Gut widening gradually. Inflated ventral gut epithelium in 1/2 XX– 1/2 XXV, extending over two to four, usually three, segments. Cells filled with vesicles apically, of same colour as intestinal content.

Nephridia (Figure 2A). Preclitellar segments: three pairs, from 6/7 to 8/9; anteseptale globular, ca half as long as postseptale (total length ca 95 µm, fix), adseptal to subterminal rise of efferent duct; terminal vesicle inconspicuous or absent. Postclitellar segments: first nephridium at 14/15, mid-body region with very few nephridia, elongate, terminal rise of efferent duct; in terminal segments nephridia shorter (ca two-thirds as long as preclitellar nephridia), with subterminal rise of efferent duct. Coelomocytes sparse but readily visible and present throughout the body; cells not in aggregations, most of coelom free. Cells flat, ellipsoid, about twice as long as wide, with very fine, regular, pale granulation (viv); granules much smaller than chloragocyte vesicles. Central nucleus visible; cell periphery often framed by a distinct hyaline margin.

No seminal vesicle, stages of developing sperm free in XI, scattered, not numerous, not compacted, not coloured. Mature spermatozoa as dense brush on top of sperm funnel collars, spermatozoa short, exact length not measured. Sperm funnels (Figure 2C) 6-8 x as long as wide, as long as or longer than body diameter (viv), shorter in fixed material; funnel body not wider than collar, usually tapering distad, but often with constrictions or areas with equal diameter; distal end attached to ventral part of septum 11/12. Vas deferens (Figure 2C) of medium length, confined to XII, in large loose coils, or in numerous regular narrow coils of equal diameter. Male copulatory organ (Figure 2C) with bursa, glandular bulb and surrounding musculature. Bursa and gland compact, roughly spherical, diameter ca 50 µm, e.g. 55 µm long, 50 µm wide, 40 µm high (fix). Vas deferens piercing glandular bulb centrally; surrounding gland cells finely granulated centrally, in aster- or modiolus-like arrangement around cuticularized terminus of vas deferens, distinct in living specimens. Bursal slit mainly longitudinal, staple-shaped, bursa not deep, often with central fold in lateral wall. No accessory copulatory glands present.

Spermatheca (Figure 1A, B) free, not attached to oesophagus, extending posteriorly into VII or VIII, consisting of ectal duct and ampulla, the latter subdivided into ectal dilatation, connecting tube and ental reservoir. No ectal gland, but epidermis thickened in a circular field around ectal pore, here occasionally foreign matter adhering to body surface. Ectal pore in intersegmental furrow 4/5, in lateral line slightly ventrally of lateral chaetae; pore ca 3 µm wide in fixed specimens, cuticular lining of ectal duct canal visible for ca 15 µm; later on cuticle absent or very thin. Ectal duct about one segment length long; ampullar ectal dilatation (Figure 2A, B: ed) ca twice as wide as ectal duct, thick-walled, spermatozoa in longitudinal and roughly parallel arrangement, orientated distally, entirely filling out the narrow lumen of the dilatation; connecting tube narrower than ectal duct, widening into thin-walled ental reservoir filled with sperm in irregular arrangement. In living specimens, canal visible throughout, from ectal pore to ental reservoir; in fixed specimens, canal only visible in most distal, cuticularized, stretch of ectal duct. One mature egg at a time.

Remarks

Three specimens of H. patricii have not been included in the type series because of malformed or reduced pharyngeal glands. In one of these specimens the glands are infected by microcystid cysts.