Uktena riparia Fend, Rodriguez & Lenat, 2015, n. sp.
Creators: name: Fend, Steven V.
name: Rodriguez, Pilar
name: Lenat, David R.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Lumbriculida
Lumbriculidae
Uktena
Uktena riparia

description: Uktena riparia n. sp.
(Figures 1–4)
Holotype. A dissected specimen, slide-mounted in Canada balsam. USNM 1283509.
Type locality. USA, North Carolina, Hoke Co., Flat Creek at Manchester Rd, in Fort Bragg, N35.183°, W79.177°, 22-Sep-2010, collected by D. Lenat.
Paratypes. All from the type locality. USNM 1283510, 22-Sep-2010, 1 sagittally-sectioned on 7 slides. USNM 1283511, 19-Jul-2010, 1 partially-mature whole mount. CASIZ 197458, 22-Sep-2010, 3 dissected on slides. MNCN 16.03/3095, 8-Oct-2009, 1 dissected. MNCN 16.03/3096, 5-Oct-2010, 1 dissected.
Additional material. USA, North Carolina, Harnett Co.: Anderson Creek at SR 2031, N35.266°, W78.819°, 21-Jan-2014. 1 whole mount (immature). Hoke Co.: Rockfish Creek, N35.006°, W79.236°, 1-May-1994, 2 dissected (1 partially mature, DNA; 1 immature). Flat Creek at Manchester Rd., in Fort Bragg (the type locality). 12-Jan-2009, 2 whole mounts (immature). 8-Oct-2009, 1 dissected (post-mature). 1-Nov-2009, 1 whole mount (post-mature). 19-Jul-2010, 3 whole mounts (immature). 22-Sep-2010, 2 dissected (mature). 28-Sep-2010, 1 dissected (post-mature) and 2 whole mounts (immature). 5-Oct-2010, 4 whole mounts (immature). 1-Sep-2011, 1 sagittally sectioned (mature), 2 dissected (mature). 5-Jun-2014, 3 dissected (partially mature). 9-Jul-2014, 1 dissected (partially mature). 14-Jul-2014, 1 dissected (partially mature). Moore Co., Lower Little River at Morrison Bridge, near SR 2017, in Fort Bragg, N35.1924°, W79.1842°, 25-Aug-2014, 2 dissected (mature). 15- Sep-2014, 5 dissected (mature; 1 for DNA). Unnamed tributary to Deep Creek, 1-Mar-1986, 2 dissected (partially mature). Unnamed tributary to Drowning Creek at Martin Rd., 4-May-2006, 1 whole mount (immature). 15-Mar- 2007, 3 whole mounts (immature). Richmond Co., Joe's Branch, N35.0802°, W79.5995°, 5-Mar-1986, 2 dissected (1 partially mature). Whitecedar Creek, N35.129°, W79.597°, 5-Mar-1986, 1 in alcohol (immature). Unnamed tributary to Naked Creek, N35.082°, W79.608°, 10-Jan-2008, 3 dissected (immature). 27-Mar-2008, 1 dissected (nearly mature).
Etymology. After Uktena, the underwater panther or horned serpent of Native American tradition, and riparia, from Latin ripa, river bank, for the habitat of the species.
Description. Medium-sized to large worms, length (preserved) to 50 mm, maximum diameter 0.8–1.3 mm. Prostomium truncate or somewhat conical, shorter than wide, with ringed proboscis 0.9–1.7 mm long, to 0.1 mm wide at middle (Fig. 1 A,B). Segmentation externally distinct in anterior segments, weak in clitellum and posteriorly; secondary segmentation absent; segment number to 190.
Chaetae two per bundle, simple-pointed, sigmoid; nodulus about 1/3 distance from tip (0.30–0.36); within each pair, the more lateral chaeta may be slightly shorter, with more distal nodulus (Fig. 1 C,D); all chaetae directed posteriad. Dorsal chaetae about same length as ventrals, or slightly shorter; chaetae in II shorter than those in III; maximum chaeta length in anterior to middle segments 210–270 Μm. Chaetae in posterior segments similar to those in anterior segments, maximum length 190–240 Μm. Mature worms with up to about 20 genital chaetae in each ventral bundle in IX and X, in two transverse rows surrounding a shallow, lenticular depression, either retracted within the depression or slightly protruded on a low mound (Figs. 1 B–D, 2A–C, 3F–H); they are slightly longer (240–340 Μm) and straighter than chaetae of adjacent segments and lack a nodulus. Chaetal glands not conspicuously enlarged. Ventral chaetae in VIII (close to genital pores) not modified in mature worms; similar in size and morphology to those in III–VII. In partially mature worms, ventral bundles in IX–X have 2 or more chaetae of normal size plus several much shorter, developing chaetae (Figs. 1 D: segment IX, 2D). Postreproductive worms (with partially resorbed reproductive organs) shed the genital chaetae, but may retain the shallow depressions on IX and X.
Epidermis in anterior segments 14–28 Μm thick; clitellum to 50 Μm. Clitellum from mid-VIII to XIII. Circular muscles of body wall about 10 Μm thick, appearing in narrow bands in anterior segments (Fig. 3 D); longitudinal muscle layer 25–40 Μm thick. Pharynx from II–V or VI, with dorsal and lateral wall ciliated and without a dorsal pad, but forming a pouch with muscular fibers extending to the body wall (Fig. 3 A,B). Pharyngeal glands (IV)V– VII, with dorsolateral, median, and ventrolateral lobes extending forward from a continuous mass at posterior septum in each segment (Fig. 3 C). No abrupt division between esophagus and intestine. Chloragogen cells cover gut beginning in VII–VIII. Brain in peristomium, not deeply lobed.
Dorsal blood vessel separate from gut in anterior segments, then closely attached posterior to about X, densely covered with chloragogen posterior to about XV. One pair commissural blood vessels connects dorsal and ventral blood vessels in posterior part of anterior segments to about XX or XXI; these vessels lack a dense chloragogen layer; in pre-clitellar segments they are long and sinuous, joining the ventral vessel in the next segment. One pair lateral, blind blood vessels joins dorsal vessel in anterior part of segments beginning about XV to XXII; short and unbranched at first, but by XXV reaching ventral part of the body, with few branches; these vessels thick and covered with chloragogen. In more posterior segments, they have several longer branches; posterior to about XL, a second pair of branched lateral blood vessels in the posterior part of each segment (Figs. 1 G, 3K).
Nephridia absent anteriorly, usually paired on 10/11; occurring irregularly in posterior segments, absent from many segments. Small anteseptal funnel is followed by a narrow, granular postseptal mass (Fig. 3 E), which terminates in the efferent duct. Duct forms a closely-appressed loop, which extends backward through multiple segments, and ends in an inconspicuous nephropore in front of the ventral chaetae behind the originating septum.
One pair male pores, usually narrowly transverse on VIII, on chaetal lines, close to 8/9 (Figs. 1 A,B). One pair spermathecae in VIII; spermathecal pores usually prominent, irregular openings in line with and slightly posterior to ventral chaetae, in front of male pores; in contracted specimens they may appear as everted sacs (Fig. 3 H,I). Male and spermathecal pores may be retracted in mature, preserved worms, within a concave midventral area. Testes paired in VIII, ovaries paired in IX, both small in mated individuals. Female funnels intersegmental in 9/10, to 250 Μm high. Sperm sacs extend posteriad to about XX–XXII; no anterior sperm sacs; egg sacs with large eggs may extend to XXIV. Spermatophores may be present in mated individuals, with ends protruding from the spermathecal pores (Figs. 1 A, 2C, 3I); spermatophores are thin, hyaline tubes, 350–800 Μm long; diameter at the narrow end 12–15 Μm, to 30–40 Μm at the wide end; with longitudinally or spirally arranged spermatozoa (Fig. 3 J).
In mature worms, each spermathecal duct opens into a deep (about 500 Μm), folded bursa, lined with cuboidal to slightly columnar epithelium and cuticle, surrounded by circular muscle layer (Fig. 4 D) and diffuse layer of muscle fibers extending between ventral and dorsal body wall. Anterior wall of each spermathecal bursa subtends a truncate-conical, muscular copulatory organ, length 150–290 Μm, width 110–130 Μm at base, narrowed slightly to 80–115 Μm, and usually somewhat expanded apically (Figs. 2 B, 3L). Apical pad of columnar epithelium surrounds a secretory surface on a round papilla (Fig. 3 M), formed by termini of thin cell extensions running from multicellular, petiolate gland at base of copulatory organ (Figs. 2 B, 4C); gland may be simple (Fig. 4 C) or with multiple lobes (Fig. 1 E). When protruded, apex of spermathecal copulatory organ is directed outward from the spermathecal bursa (Figs. 1 B, 2C, 3H), and spermatophores from the concopulant worm may be attached to its base (Fig. 3 I). Retracted copulatory organ usually dorsally directed within the bursa, oriented toward the opening of the spermathecal duct (Figs. 2 A,B, 3L, 4C). One or more spermatophores may be contained within the spermathecal bursa, with wider end entally oriented; free sperm apparently exits spermatophore near opening of spermathecal duct (Figs. 2 A,C).
Ental (postero-dorsal) end of each spermathecal bursa joined by nearly tubular spermathecal duct (width 40–95 Μm), which may extend posteriorly through several segments (Fig. 2 A,C); ectal part of duct lined with cuboidal epithelium, which becomes more columnar as duct gradually widens into the ampulla; transition usually with irregular (folded or incised) epithelium, with sperm lined up along it (Fig. 4 A). Ampulla irregularly sacciform, 130–360 Μm wide; thin walled (5 Μm), filled with amorphous material (Fig. 4 B), or sparse, possibly degenerate sperm. Total spermatheca length to about 1600 Μm, extending posteriorly through multiple segments, to as far back as XV.
Atrial ducts of mature worms open into deep (300–450 Μm) ectal bursae (Fig. 2 B,C), thin-walled, with cuboidal epithelium and cuticular lining, and surrounded by strands of muscular fibers which join sac and area near the pore to dorsal body wall. Two large, globular or multi-lobed glands (70–130 Μm diameter) also join ental part of male bursa, with cell extensions terminating in small, distinct secretory surfaces on short, distinct papillae (Figs. 1 F, 2B, 4F). Numerous smaller glands also present along the wall of the bursa (Fig. 4 E). Ental end of bursa may subtend a broad, indistinct lobe, but atrial duct does not form a penis.
Atria prosoporous, elongate, extending as far back as XI–XIV, within the sperm sac. Atrial duct irregularly cylindrical or slightly expanded in ectal or middle part (length 400–800 Μm, width 70–100 Μm) (Fig. 2 A,C); wall of duct with cuboidal epithelium (10–20 Μm thick), surrounded by thin (1–2 Μm) circular muscle layer and longitudinal layer of muscular fibers to 12 Μm thick. Lumen of duct may contain a developing spermatophore, which first appears as a dense, elongate-coiled bundle of sperm (Fig. 4 H), eventually becoming straight, within a sheath (Fig. 4 G,I). Wall of spermatophore sheath up to 2 Μm thick. Spermatophore morphology in atrial duct similar to that observed in spermathecal bursa, except that the wider end is ectally oriented (Fig. 4 G).
Atrial ampulla (Figs. 2 A,C, 4J) 260–500 Μm long; ectal part of ampulla to 110–180 Μm wide, with columnar, folded epithelium; entally narrower (50–90 Μm), with thinner epithelium (Fig. 4 J,K). Entire ampulla covered with thin (5–12 Μm) muscle layer and densely covered by thick layer of multicellular prostate glands, 70–200 Μm high (Fig. 4 J,L). Prostate glands longest at mid-ampulla; secretions apparent at junction with atrium, or within atrial ampulla (Fig. 4 K,L). Atrium joined subapically (about 1/4 to 1/5 from ental end) by a single vas deferens, short (200–400 Μm) and thick (22–30 Μm diameter), which extends posteriorly one or more segments, gradually widening into a narrow, posteriorly-directed sperm funnel in XIV–XVI (200–400 Μm long) (Fig. 2 A).
In some partially-mature worms, developing spermathecal bursa is duct-like, with columnar epithelium and narrow lumen (Fig. 2 D); spermathecal copulatory organ and gland appear completely absent. Ental part of spermatheca weakly differentiated and tubular. Male pore of a nearly-mature worm (Fig. 2 D) opens into a deep bursa. Ampulla of atrium tubular, without the deeply incised or folded epithelium of mated worms; some prostate cells forming multicellular, petiolate glands. Vas deferens joins atrial ampulla subapically, extending posteriorly to XI. Worms at earlier stage of development with large testes and ovaries (Fig. 2 E); atria elongate-cylindrical, prostate cells not in bundles, sperm funnels on posterior septum. Genital chaetae just beginning to develop in IX and X.
Remarks. As in Kincaidiana and Guestphalinus, Uktena riparia is a relatively large microdrile with a cylindrical body, an elongate, superficially ringed proboscis, spermathecae in the atrial segment, male pores in a segment anterior to X, and elongate or tubular atria and spermathecae. The northwestern Nearctic K. hexatheca is easily distinguished from U. riparia by thickened, bifid chaetae in anterior segments, atria in IX, and spermathecae in post-atrial segments. Semiprosoporous male ducts, with testes in VIII–IX and atria in IX, distinguish all Guestphalinus, including the Palearctic G. w i a rd i and undescribed Nearctic species (Fend & Rodriguez, unpublished). The general habitus (relatively large size, proboscis) of the above three genera, plus elongate atria and branched lateral blood vessels in posterior segments, also characterize Rhynchelmis Hoffmeister, 1843 and Eclipidrilus (Premnodrilus) (Smith, 1900), both of which have southeastern Nearctic representatives. With the exception of Rhynchelmis croatanensis Fend & Lenat, 2010, Rhynchelmis and Eclipidrilus have the male pores in X; both of these genera have spermathecal pores only in pre-atrial segments, in VIII and IX, respectively. Eremidrilus Fend & Rodriguez, 2003 species also have a proboscis, but they are smaller worms, with atria in X and spermathecae only in post-atrial segments, in XI or in both XI and XII. Among the genera having representatives with atria in VIII, none has a proboscis or spermathecae in the atrial segment.
In three mature U. riparia specimens, both spermathecal bursae were partially everted, extending the spermathecal copulatory organs outward. Spermatophores were attached to the bases of either extended (Fig. 3 I) or retracted (Fig. 3 L) copulatory organs, suggesting production of an adhesive substance by the partner. Once within the spermathecal bursa, the sperm appear to exit the broad opening of the spermatophore sheath and enter the spermathecal duct. It is not clear whether the Uktena male bursa is normally eversible, as only one of them was everted in a single highly contorted worm. The large, usually paired glands were difficult to see within the highly folded male bursae. Their location near the atrial pore suggests a function related either to spermatophore formation or transfer (see discussion).
The large bundles of genital chaetae in segments surrounding the female pore may be a unique character within the Oligochaeta. Although they are present only in reproductively mature U. riparia specimens, and appear to be quickly shed after the short reproductive season, the small field surrounding them persists for some time as a shallow depression or low mound. At early stages of development, they appear similar to normal replacements of somatic chaetae, except that several are present in the bundle.
Immature U. riparia specimens could be confused with other large, proboscis-bearing lumbriculids that occur in the southeastern region. The complete lack of secondary segmentation in anterior segments, the longer and superficially-ringed proboscis, and the less-tapered body form can be used to separate well-preserved Uktena specimens from Eclipidrilus (Premnodrilus) or Rhynchelmis species; identification can be confirmed in cleared specimens by the presence of a single pair of variably-branched blood vessels (instead of two) in middle segments (anterior to about XL). Small gonads in VIII–IX will distinguish partially-mature specimens of U. riparia from Rhynchelmis and Eclipidrilus species, which have them in X–XI (IX–X in R. croatanensis). The much smaller Eremidrilus species have a short proboscis, secondary segmentation, and lack branched posterior blood vessels.
description: Published as part of Fend, Steven V., Rodriguez, Pilar & Lenat, David R., 2015, Uktena riparia n. gen., n. sp. (Annelida, Clitellata, Lumbriculidae), a new spermatophore-producing oligochaete, pp. 411-424 in Zootaxa 3994 (3) on pages 413-419, DOI: 10.11646/zootaxa.3994.3.5, http://zenodo.org/record/246106