Hemienchytraeus phytotelmatus Schmelz

Schmelz, Rüdiger M., Jocque, Merlijn & Collado, Rut, 2015, Microdrile Oligochaeta in bromeliad pools of a Honduran cloud forest, Zootaxa 3947 (4), pp. 508-526 : 513-516

Hemienchytraeus phytotelmatus Schmelz , sp. nov.

( Figure 3 )

Material examined. Holotype. IG 327183-05, adult specimen, unstained whole mount. Honduras, Cusuco National Park, Napacu [15.50834 -88.23274], 2057 m asl, bromeliad tank on the ground, M. Jocque 18/08/2006. Paratypes all from same locality, all unstained whole mounts: IG 327183-06 to IG 327183-10, 5 adult specimens, same data and same plant as holotype. IG 327183-11 to IG 327183-15, 4 adult specimens, 1 subadult, [15.50541 - 88.23648], 2025 m asl, bromeliad tank on the ground, M. Jocque 13/08/2006. IG 327183-16 to IG 327183-20, 5 adult specimens [15.50723 -88.23363], 2061 m asl, M. Jocque 11/08/2006. Further non-type material, in the 1st author's collection: 40 specimens, unstained whole mounts, 20 adult, 8 subadult, 2 juvenile, complete or posteriorly incomplete, same location as types series, M. Jocque 06–18/08/2006; 5 specimens, 3 adults, 1 subadult, 1 juvenile, [15.505813 -88.21473], 2061 m asl, M. Jocque 29/06/2013.

Etymology. Named after the habitat where the species was found.

Description. Animals strongly contracted and bent inward, some specimens bent into a circle. Body length 9.5–12 mm, diameter 0.4–0.5 mm. Segment number of adults with complete posterior end 44–66 (n = 17); 12 specimens with 51–57 segments. Chaetae 2 per bundle (occasionally 3, 1, or 0), absent at XII, lateral chaetae smaller than ventral chaetae in a segment. Anterior chaetae straight distally and with proximal hook, posterior chaetae straight proximally and with distal bend. Chaetae in caudal segments almost twice as large as preclitellar chaetae. Ventral preclitellar chaetae c. 50 µm long and 5 µm thick, ventral caudal chaetae 80–90 µm long and 8 µm thick. Chaetae smallest immediately behind clitellum (30: 3 µm laterally, 40: 4 µm ventrally), gradually increasing in size posteriad; from about XXX on distinctly larger than preclitellar chaetae. Head pore on prostomium mid-dorsally. Epidermal gland cells one row per segment, at chaetal level; from VIII on towards anterior end increasingly more glands per segment; peristomium and posterior half of prostomium completely covered with gland cells.

Body wall thickness varying between 12 µm (dorsally, hindmost segments) and 50 µm (ventrally, foremost segments); thickness mostly ca. 20 µm; cuticle very thin, less than 1 µm, longitudinal muscle layer always welldeveloped. Brain deeply incised anteriorly, slightly concave or almost straight posteriorly, about as long as wide (c.

80–100 µm) when tip of anterior incision is taken as reference. Ventral nerve cord apparently medullar. Oesophageal appendage with at least 4–5 terminal branches on each side. Pharyngeal glands with secondary ventral lobes in V and VI, lobes equally large and spherical. Dorsal lobes united in IV–VI, separate in IV or VI in single specimens. Preclitellar nephridia 4 pairs, from 6/7 to 9/10; anteseptale and postseptale rounded, length ratio 3: 4, constriction at septum; subterminal rise of efferent duct, no terminal vesicle seen. First postclitellar nephridium from 13/14. Dorsal blood vessel origin not seen in most specimens; origin in XII in one submature specimen. Pars tumida of midgut (ventrally inflated gut epithelium) in XXVIII–XXXVI, extending over 4 to 5 segments.

Clitellum short, in XII and anterior parts of XIII, not reaching chaetae of XIII; girdle-shaped, mid-ventrally only granulocytes in indefinite rows; hyalocytes and granulocytes alternating dorsally and laterally down to level of bursal slits, pattern reticulate (dense rows in one specimen). Border cells with an outer ring of granular cells and an inner ring of hyaline cells. Seminal vesicle very large, extending over 3 to 7 segments in adults, behind clitellum down to XVI (XVII), in preclitellar segments from IX, X or XI, occupying much coelomic space in these segments. Spermatozoa ca. 200 µm long, heads ca. 15 µm long. Sperm funnel convoluted, about as long as body diameter, tapering distad, proximally c. 80–100 µm wide; collar wider and with flap-like extensions to which spermatozoa are attached. Vas deferens in XII ventrally, coiled into dense isodiametric spirals. Male copulatory organ: Bursal slit longitudinal, outer margin like an elongate E. Male glandular bulb spherical, diameter c. 80 µm. Dorso-ventral copulatory muscles conspicuous, strands present in all of XII, anterior and posterior strands inserting ventrally in body wall, central strands penetrating male glandular bulb. No subneural glands or other epidermal modifications. One to four eggs mature at a time, in various positions, seen from XI to XVIII, in one or two consecutive segments, in same segments as seminal vesicle or behind.

Spermatheca. No ectal gland. Ectal duct c. 120–150 µm long, 10–14 µm wide distally and 16–18 µm wide proximally, canal narrow, diameter c. 1.5 µm; ampullar ectal bulb inconspicuous, c. 25–26 µm wide, thick-walled, with few spermatozoa present. Connecting tube extending into VIII or IX, narrower than ectal bulb, length c. 350– 400 Μm, widening towards ental reservoir, and with meandering, often sperm-filled canal widening entad as well. Ental reservoir thin-walled, very large, extending over 2–4 segments, present in VII to X, mostly VIII–IX, and with diameter up to 2/3 body diameter, sperm arranged in distinct but loose packages with smooth and wavy outline.

Remarks. Hemienchytraeus phytotelmatus sp. nov. is recognized by the following combination of characters: (1) huge spermathecae and seminal vesicles, (2) pharyngeal glands with secondary lobes in V and VI, (3) oesophageal appendages with 4–5 terminal branches, (4) 4 pairs of preclitellar nephridia, from 6/7 to 9/10, (5) clitellum girdle-shaped, (6) male glandular ("penial") bulb present, small. Most conspicuous are the huge masses of sperm accumulated in 10–11 segments of the anterior body region, first allosperm of the spermathecae, followed by mature or developing sperm in the seminal vesicles. Five out of the 23 currently accepted species of Hemienchytraeus ( Schmelz & Collado 2012) share the most conspicuous traits of H. phytotelmatus , the huge spermathecae and seminal vesicles: H. loksai Dózsa-Farkas, 1989 from Ecuador and Peru, the two Brazilian species H. cipoensis Righi, 1973a and H. makusi Righi, 1988 , and the two Central African species H. africanus Černosvitov, 1938 and H. shirensis Bell, 1954 . The differences of these species from H. phytotelmatus are as follows: H. loksai is densely covered with epidermal gland cells, there are 5 preclitellar pairs of nephridia, from 5/ 6 to 9/10, and 3 secondary pharyngeal gland lobes, in V, VI, and VII ( Dózsa-Farkas 1989; Schmelz & Collado 2007). H. cipoensis has short and simple oesophageal appendages without secondary or tertiary tubes, the clitellum is saddle-shaped, and male glandular bulbs are absent ( Righi 1973a). H. makusi is without epidermal gland cells, secondary pharyngeal gland lobes are absent, and sperm in the ental reservoir of the spermathecal ampulla is arranged in numerous discrete and digitiform packages ( Righi 1988). The dorsal blood vessel originates in XV, but this trait was not well-distinguished in our specimens. H. africanus is larger (up to 17 mm in fixed state), with more segments (up to 72), chaetae are smaller posteriorly than anteriorly, and there are two large accessory male glands in front of and behind a small male glandular bulb ( Černosvitov 1938). H. shirensis has a very thick body wall (1/4 worm diameter), a clitellum extending over 2 segments (from the chaetae of XI to the chaetae of XIII), and nephridia with very small anteseptale and large and bilobed postseptale ( Bell 1954).

Knowledge of several characters in the new species is unsatisfactory, due to the fact that only ethanolpreserved material was available. Especially important is form and branching pattern of the oesophageal appendage, one of the main diagnostic characters at the genus and species level. In specimens that have not been anaesthetized prior to fixation, these delicate tubes are usually too much compressed and convoluted to be observed and described properly. In one specimen of the type series the following was distinguished: Unpaired trunk, elongate primary branches, longer than trunk, c. 3x as long as wide (80–90 Μm long, 23–29 Μm wide), and 4–5 terminal branches on each side, narrower than primary branches (14–17 Μm wide). Terminal branches appear to be tertiary, i.e. branching off short bifurcated stump-like secondary branches.

One subadult specimen has a regenerating anterior end. From segment VIII on anteriad, 5 segments are being regenerated. Body diameter is smaller here, and organs are not yet fully developed. The ental reservoir of the spermathecae is present in VIII and IX, but the ectal part is missing, and there is no connection of the organ with the exterior. It seems that the worm's anterior end was bitten off when fully mature, and then regenerated.—In juvenile specimens the size difference between anterior and posterior ventral chaetae is less marked, e.g. 50: 4.5 Μm vs. 60: 5 Μm.—The gut of all specimens is filled with plants remnants in decomposition and small amounts of amorphous humus.

Healy (in litt.) distinguished three unnamed species of Hemienchytraeus collected in bromeliads of Puerto Rico together with Aulophorus superterrenus ( Richardson et al. 2000) . In one of them the described details agree with H. phytotelmatus : "54–56 segments … large spermatheca with simple duct, large, flared, sperm funnel, large seminal vesicle extending back for several segments and smallish penial bulb" (Healy in litt.).

Figures

FIGURE 3. Hemienchytraeus phytotelmatus sp. nov. A. Anterior body region, anterior 16 segments, lateral view, schematic. er, ental reservoir of spermatheca; oo, oocytes; pp, pharyngeal pad; sl, secondary pharyngeal gland lobes in V and VI; sv, seminal vesicle. B. Nephridia at 6 / 7, 7 / 8. C. Ventral chaetae, from a caudal segment (left) and from V (right). D. Male efferent apparatus with sperm funnel, vas deferens and male copulatory organ. E. Ectal part of spermatheca. ct, connecting tube; eb, ectal bulb of ampulla; tr, transition from connecting tube to ental reservoir. All drawings from unstained whole mounts.