Sylphella puccoon, Rodriguez, Pilar, Fend, Steven V. & Lenat, David R., 2014

Rodriguez, Pilar, Fend, Steven V. & Lenat, David R., 2014, Sylphellapuccoon gen. n., sp. n. and two additional new species of aquatic oligochaetes (Lumbriculidae, Clitellata) from poorly-known lotic habitats in North Carolina (USA), ZooKeys 451, pp. 1-32 : 4

Taxon classification Animalia Lumbriculida Lumbriculidae

Sylphella puccoon sp. n. Figs 1, 2, 3

Holotype.

USNM 1251692: a dissected worm, stained in Harris’ hematoxylin, mounted in Canada balsam (collected 23 Jan 2009).

Paratypes

all from the type locality. USNM 1251693-1251698: 7 Jan 2009, 1 whole mount; 23 Jan 2009, 3 dissected; 30 Jan 2009, 2 sectioned (1 sagittal, 1 transverse). MNCN 16.03/3083: 14 Jan 2009, 2 dissected. CASIZ 197898: 23 Jan 2009, 3 dissected.

Type locality.

An unnamed, very small tributary (seep) to Pokeberry Creek, Chatham Co., North Carolina, USA.

Etymology.

The genus name refers to Sylph, the Latin name of an elemental spirit of the air that suggests the Latin silva, for woodland, followed by the Latin diminutive -ella. The specific name puccoon is the Algonquian Indian word which means pokeberry ( Phylolacca species).

Other material.

7 Jan 2009, 2 whole mounts. 14 Jan 2009, 3 dissected and 3 whole mounts; 11 in alcohol. 23 Jan 2009, 9 dissected and 1 whole mount; 3 in alcohol. 30 Jan 2009, 2 sectioned for histological study. All specimens (including the type series) collected by D.R. Lenat from the type locality.

Description

(based on mated specimens). Number of segments 65-83. Length of fixed worms 15-25 mm. Diameter of the body from 14 unmounted worms in lateral aspect (measured to 0.01 mm): 0.44-0.66 mm in VIII (mean 0.51 mm), 0.45-0.68 mm at clitellum (mean 0.54 mm), and 0.50-0.76 mm (mean 0.61 mm) at mid-body.

Prostomium rounded-conical, 270-400 μm long, width about the same as length. Secondary annulation (narrow ring in anterior part of segment) from segment V; present but weak in post-clitellar segments (Fig. 1A). Epidermis 10-15 μm high in anterior segments. Clitellum annular, from segment X to XIV, with epithelium up to 25-35 μm high, formed by unordered, glandular cells (Fig. 2B). Longitudinal muscles up to 32 μm thick in anterior segments. Chaetae sigmoid, simple-pointed with strongly curved distal tip; ventral chaetae larger than corresponding dorsal chaetae in anterior segments (Table 1). Ventrals largest in II to about XIII (126-204 μm long, up to 7 μm thick), anterior dorsals distinctly smaller and thinner, (60-130 μm long, 4 μm thick) (Fig. 1B); maximum ventral chaeta length about 1.6 that of dorsals in preclitellar segments. Ventral chaetae only slightly larger than dorsals in post-citellar segments. Nodulus at about 0.32-0.46 (mean = 0.40) from the distal end.

Transverse, oval male pores are in line of ventral chaetae of segment X and XI, about midway between chaetae and posterior septum (Fig. 1A). Female pores open just below the lateral line, in intersegment 12/13. Inconspicuous, round spermathecal pores open behind, and in line with the ventral chaetae in XII–XIII.

Pharynx developed mainly dorsally and laterally, in segments II and III. Pharyngeal glands well developed dorsally and ventrally in IV–VI, usually extending ventrally into VII. Chloragogenous tissue well developed from VII backwards. A supra-intestinal vessel may appear differentiated from the perivisceral sinus (Fig. 2E) beginning in XIV; this is not evident after the dorsal vessel joins the gut in about XX. One pair of simple commissural blood vessels join dorsal and ventral vessels in anterior segments to about XV; those in XII may loop into the egg sacs (Fig. 2D). Lateral blood vessels absent from posterior segments except for 1-2 very short lobes on dorsal vessel in about the posterior 1/4 of the body (Fig. 1E). Nephridia usually paired in VII and VIII, and paired, single, or absent in segments posterior to XIII; efferent ducts simple, mostly limited to ventral half of body, without vesicles at nephridiopores. Sperm sacs extend anteriorly to VIII or IX, and backwards as far as XXII. Egg sacs may extend to 2 or 3 segments beyond sperm sac; when eggs have partially completed vitellogenesis, egg sacs shorter, not extending beyond sperm sacs, to XIII or XIV.

Two pairs small testes, in segments X and XI; one pair elongate ovaries in XII, extending through XIII. Female funnels large, attached to the septum and opening in intersegment 12/13. Two pairs spermathecae, the first in the post-atrial segment (typically XII), and the second in the post-ovarian segment (typically XIII) (Figs 1C, 2F).

A single vas deferens per atrium (prosoporous condition), sperm funnels located on the septa of intersegments 10/11 and 11/12 (posterior septa of atrial segments), but folded back into the next segment. Vasa deferentia long (about 700 μm), penetrating the posterior septa, and forming a long, convoluted loop within each post-atrial segment (Fig. 1C). Vasa deferentia narrow (12-16 μm diameter) and transparent, each joining the atrium at the ectal (or basal) part of the ampulla (adjacent to the atrial duct), and running under the atrial musculature to about the middle part of the ampulla, where it opens into the atrial lumen (Fig. 1C, D). Atria petiolate, extending medially from male pore, with nearly spherical ampulla (140-210 μm diameter, slightly longer than wide) and tubular ectal duct (Fig. 1D). Ampullar musculature very thick (40-50 μm), organized in many intercrossing layers (Fig. 2 H–J). Atrial ampulla with very thin epithelium, and covered by a thin (up to 5 μm) layer of cells and prostate glands formed by elongate-petiolate clusters of cells; each gland is pedunculate with a narrow extension penetrating the atrial musculature (Fig. 2I). Atrial duct tubular (17-24 μm diameter, 90-110 μm long), composed of an epithelium surrounded by loose, indistinct musculature, extending into a type-1 penis (Fig. 17, in Rodriguez and Giani 1994) within a deep penial sac (120-230 μm deep) (Figs 1C, D, 2M), and associated with retractor muscles extending dorso-laterally to the body wall. Penis length 90-110 μm; the broad, ental part forms a distinct epithelial tube which disappears ectally; the middle portion is surrounded by a ring of what appears to be circular musculature; and the ectal part is sharply acuminate, covered by a thin (ca.1 μm), cuticular layer.

The spermathecae have a narrow duct and an irregular, sacciform ampulla. Spermathecal duct fusiform, (30-45 μm maximum diameter), formed by columnar epithelium, a thin (about 2 μm) muscle layer, and with a wide lumen except at the pore; ental end of the duct prolonged into a narrow neck (12-20 μm diameter) which joins the ampulla (Figs 1C, 2L). Duct sharply narrowed at the pore, with a short sphincter surrounded by a circular muscle layer (Figs 1C, 2K). Ampulla in two parts, a short ectal section (60-90 μm long by 35-46 μm wide), lined with irregular epithelium, and a much larger ental part (320-480 μm by 130-250 µm), which is lined by columnar, vacuolated epithelium, up to 35 μm thick (Fig. 2G, K). Sperm within the spermathecae loose and unordered; epithelial vacuoles not obviously containing resorbed sperm. All spermathecae similar in size; ampullae of mated worms may extend into adjacent segments.

Anomalies.

Two specimens had the entire sequence of reproductive organs in segments VII–X, with the clitellum in VII–XI instead of the usual X–XIV; apparently an anterior shift of three segments. These aberrant worms appeared normal in other respects, except that nephridia were not present in VII and VIII.

Taxonomic remarks.

The combination of multiple atrial segments, prosopore male ducts in the testicular segments (GI and GII, see Brinkhurst 1991), and postatrial spermathecae in Sylphella puccoon gen. n., sp. n. is shared with the monotypic genera Lamprortus Rodriguez, 1994 (in Brinkhurst et al. 1994) and Wsewolodus Semernoy, 2004 (Fig. 3). Additionally, this arrangement of reproductive organs occurs in some species (or variants) of Lumbriculus Grube, 1844 and Lamprodrilus Michaelsen, 1901 ( Teleuscolex and Agriodrilus included). Lamprortus is well distinguished from other lumbriculids by its hologyny, i.e., by the possession of 2 pairs of testes and 2 pairs of ovaries. Lamprortus and most Lamprodrilus species have only one spermathecal segment, although variants of Lamprodrilus mrazeki Hrabě, 1928 and Lamprodrilus satyriscus Michaelsen, 1901 may have two or more pairs of spermathecae. Almost all lumbriculids with two atrial segments differ from Sylphella gen. n. in having one intervening segment between the last atrial segment and the first spermathecal segment (Fig. 3). Thus, relative to the gonads, the first spermathecal segment is in the first post-ovarian segment (GIV in Lamprodrilus and Wsewolodus , and behind GIV in Lamprortus ). In Sylphella , the first spermathecae are in the ovarian segment (GIII). The genus Lumbriculus is highly variable not only in number but also in the position of the spermathecae, but usually more than two pairs open laterally, either at the dorsal or ventral side of the body. The closest match to Sylphella is Lumbriculus tetraporophorus Popchenko, 1976a, but that species is distinguished from Sylphella by typical Lumbriculus characters, including bifid chaetae, a plexus of anterior commissural blood vessels, and Lumbriculus -type male reproductive organs, with a pyriform atrium and penial sac ending in a porophore (see Table 2).

The tetrathecate condition, with paired spermathecae in the first two postatrial segments, is a feature shared with some species in the semiprosoporous lumbriculid genera Trichodrilus Claparède, 1862 and Eremidrilus Fend & Rodriguez, 2003. However, the presence of two pairs of prosoporous atria in Sylphella suggests that a close phylogenetic relationship with these genera is improbable.

The general form of the atria bears a slight resemblance to some Palearctic species of the genus Trichodrilus having petiolate atria, spherical and very muscular atrial ampullae, and two pairs of spermathecae (e.g., Trichodrilus aporophorus Popchenko, 1976b, Trichodrilus claparedei Hrabě, 1937). Bichaeta sanguinea Bretscher, 1990 also has a spherical and very muscular atrium, but lacks an atrial duct. In contrast, genera resembling Sylphella in the arrangement of reproductive organs ( Lamprodrilus , Lamprortus , Wsewolodus and Lumbriculus ) tend to have elongate atria.

The atrial musculature in Sylphella consists of many small, cross-hatched layers, similar to some other lumbriculids, such as Trichodrilus longipenis Giani & Rodriguez, 1994. Details of atrial musculature are usually not given in lumbriculid diagnoses, but where described, the atrial muscle fibers show a simpler organization (parallel or two opposing layers) in the related genera. The Sylphella arrangement of atrial muscles should be distinguished from the simple crossed musculature in Lumbriculus species, which consists of only two perpendicular layers; however, it bears some resemblance to the many diagonally arranged layers in some Eclipidrilus Eisen species ( Fend 2005).

The penis in Sylphella puccoon is similar to that described for Styloscolex japonicus Yamaguchi, 1937 in its basic structure, as well as in the presence of a smooth, rigid cuticular layer (sheath) on the ectal end (Fig. 2M, N). Styloscolex Michaelsen, 1901 has an intervening segment between the testicular and the ovarian segments, an autapormorphy that separates this genus from other lumbriculids. Several other Styloscolex characters, including pre-atrial spermathecae in most species, elongate atria in a single segment, and a forward shift in reproductive organs ( Brinkhurst 1989) suggest that Styloscolex is probably not closely related to Sylphella .

Lamprortus and most Lamprodrilus species also have a type-1 penis (i.e., an extension of the atrial duct within a fold of the ventral body wall, see Rodriguez and Giani 1994), but these usually have a characteristic structure, being associated with a large mass of glands. Some Lamprodrilus species also have muscular penial bulbs. Lumbriculus species have a type-2 penis (i.e., formed in part by elongation of atrial lining cells) within a penial sac formed by very thick, columnar epithelium (see Hesse 1902 for Lumbriculus variegatus ). Penes are absent in Wsewolodus .

Enlarged ventral chaetae in anterior segments occur to some degree in many lumbriculids, but the difference is well marked in several Trichodrilus species (see Rodriguez and Giani 1994), Lamprodrilus inflatus Michaelsen, 1905, and Stylodrilus mirus (Chekanovskaya, 1956).

Ecological remarks.

Sylphella puccoon gen. n., sp. n. has only been collected during winter months from a single, small seep that is a tributary of Pokeberry Creek, North Carolina. A large number of similar seeps were investigated by one of the authors (D. Lenat) adjacent to Pokeberry Creek, but Sylphella was limited to a 10-m reach of the largest seep (1 meter wide). The small streams in this area go completely dry during summer months, due a combination of clay soils and seasonal rainfall patterns. The dominant macroinvertebrates in these seeps were the isopod Caecidotea forbesi (William), the amphipod Crangonyx sp. Bate, and chironomids. The mayfly genera Callibaetis Eaton and Leptophlebia Westwood can be abundant, but other EPT taxa were sparse. Other oligochaetes at this site include Rhynchelmis bolinensis Fend & Lenat (the type locality), Eclipidrilus cf. fontanus , Rhyacodrilus propiporus Rodriguez & Fend, and an undescribed lumbriculid of unknown generic attribution.