Altmanella idahoensis, Fend, 2009

Fend, En. V., 2009, An evaluation of the genus Kincaidiana Altman, 1936, with the designation of Altmanella n. gen. (Annelida, Clitellata, Lumbriculidae), Zootaxa 2077, pp. 1-30 : 14-20

Altmanella idahoensis n. sp.

Figures 7–10

Holotype. USNM 1122773 A whole mounted worm, stained in borax carmine.

Type locality. Idaho, Oneida Co.: Deep Creek above Stone Canal, 11-Jul-04, collected by D. Gustafson.

Paratypes. USNM 1122774-1122779 . From the type locality, 11-Jul-04, 3 whole mounts, 2 sectioned. Idaho: Bonneville Co: Fisher Bottom lower spring, 27-Jun-00, 1 whole mount .

Other material. California: Tehama Co.: Sacramento River at Bend , coll. S. Fend, 13-May-01, 19 whole mounts, 5 dissected, 2 sectioned. 26-May-02, 2 whole mounts, 1 dissected . Idaho: Bear Lake Co.: Bue Pond Spring, 4-Sep-00, 3 whole mounts. St Charles Spring, 4-Sep-00, 2 dissected, 1 whole mount. Bonneville Co: Fisher Bottom lower spring, 27-Jun-00, 1 dissected, 3 sectioned. 2-Sep-00, 7 whole mounts, 3 dissected. Clearwater Co.: North Fork Clearwater River at Dworshak Ramp, 1-Apr-05, 11 whole mounts, 2 sectioned . Idaho Co.: Meadow Creek at Selway Falls , 1-Jul-02, 1 whole mount. Oneida Co.: Deep Creek above Stone Reservoir, 25-Apr-04, 7 whole mounts. Deep Creek above Stone Canal, 11-Jul-04, 11 whole mounts, 3 sectioned. Power Co. : American Falls Hatchery outlet at Snake River , 27-Mar-00, 5 whole mounts. Batiste Springs, 28-Feb-02, 7 whole mounts, 2 dissected . Nevada: Elko Co.: Marys River, 28-Apr-04, 4 whole mounts. Bruneau River at Cottonwood Creek , 15-Jul-04, 1 whole mount . Oregon: Klamath Co.: Spring Creek at Williamson River , 23-Jun-08, coll. J. Carter, 6 whole mounts,12 dissected. Wasco Co. : Deschutes River at South Junction Road , 26-Oct-95, coll. S. Fend, 10 whole mounts, 3 dissected, 2 sectioned . Utah: Cache Co.: Logan River at Wood Camp , 17-Apr-97, coll. R. D. Kathman, 5 whole mounts. Logan River at Beaver Creek , 29-Aug-03, 1 whole mount . Utah Co.: American Fork , 28-Aug-03, 10 whole mounts. All specimens collected by D. Gustafson, unless otherwise noted .

Etymology. Named for the type locality.

Description. Histological details are based primarily on sectioned worms from Deep Creek, Fisher Bottom spring, Clearwater River, and Sacramento River. Measurements in the text are means and ranges for all sites; measurements by region are given in Table 1.

Length of preserved worms 12 (7–22) mm; segments 62 (36–104); diameter 0.36 (0.25–0.56) mm in X. Prostomium rounded to nearly conical ( Fig. 7). Chaetae paired, in four bundles per segment, beginning in II. All chaetae simple-pointed, moderately sigmoid, with nodulus 0.35 (0.28–0.43) of the total length from the tip ( Fig. 7E). Chaetal length 89 (70–106) µm in clitellar region, 87 (60–110) µm posteriorly. Secondary segmentation begins in III, with a narrow anterior ring; segmentation obscured by clitellum, often weak in posterior segments.

Epidermis in anterior segments 10–14 µm thick; in clitellum 12–22 µm. Clitellum distinctly glandular in mature specimens, surrounding entire segment from VIII to X. Circular muscle of body wall 1–2 µm thick; longitudinal muscles 10–15 µm thick. Septa indistinct at 1/2 and 2/3; prominent elsewhere. Pharynx with ventral wall thin; a thickened dorsal pad in I–II ( Fig. 7C); everted in many preserved specimens ( Fig. 7D). Pharyngeal glands usually IV–VI, may extend into VII ( Fig. 7C).

Nephridia as described above for A. freidris ; postseptal expansion 50–60 µm long, diameter 25–30 µm; terminal vesicle 30–50 µm long by 17–20 µm wide ( Fig. 10D). Blood vessels as described above for A. freidris . Ventral blood vessels separate through III, join in IV; the dorsointestinal blood vessel begins in about VII.

All genital pores paired, on ventral chaetal lines. Male pores in VIII, about midway between chaetae and 8/9. Spermathecal pores paired in IX, near 9/10, often on slight papillae. Female pores intersegmental on 9/10. Testes paired on anterior septa in VIII, ovaries paired in IX. Sperm sacs confluent with egg sacs, extending back to about XII–XIV; anterior sperm sacs usually absent. Egg sacs extend to about XIV–XV (as far as XVII).

Spermathecal ampulla irregularly ovate, length 240 (120–410) µm, width 120 (40–200) µm ( Fig. 8). A very thin muscle layer surrounds the epithelium; histology of ampulla as described (see above) for A. freidris ( Fig. 10B–C). Spermathecal duct distinct, tubular, length 169 (59–310) µm; diameter at middle 20 (14–31) µm. Duct formed of tightly packed, regular epithelium, surrounded by a prominent layer of transverse-circular muscles, about 2– 4 µm thick ( Fig. 10A). The duct terminates in a vestibule, 115 (75–160) µm tall by 43 (24–62) wide; epithelium somewhat columnar, surrounded by a 2–5 µm layer of circular-transverse muscle fibers. Female funnels simple, tubular, about 80 µm high, with thick anterior lip.

Male funnels on 8/9, directed forward into VIII or posterior margin directed back into sperm sacs; occasionally extending back to mid-IX. Funnels about 60–100 µm wide, not very convoluted. Vasa deferentia relatively short and thick; length 460 (300–640) µm; width 22 (15–28) µm at most sites, but to 40 µm in Spring Creek, Oregon; ciliated. Vasa may enter IX slightly, but do not form a distinct loop in IX ( Fig. 8); in most specimens they appear to enter VIII directly, penetrating atrial muscle layer ental to the midpoint of the atrium, and entering atrial lumen subapically (thus usually embedded for a short distance, about 30–70 µm).

Atria usually entirely in VIII, but may pass through septum 8/9 into IX. Total atrium length 230 (97–400) µm at most sites ( Table 1), but to 625 µm in Spring Creek, Oregon. Atria consist of a short duct (mean length 68 µm, mean width 18 µm) and ental, club-shaped ampulla (length 189 [70–500] µm, width 45 [34– 67] µm) ( Figs. 8, 9); ampulla mostly distinguished from indistinct duct by presence of prostate glands ( Fig. 10E–F). Ampullar epithelium of cuboidal to slightly columnar, ciliated cells; lumen variable, often less than 10 µm wide, but mean diameter 22 µm, and up to 57 µm when ampulla is expanded ( Fig. 10G). Muscle layer of atrial ampulla thin, 1.6 (1–3) µm (to 7 µm at Spring Creek) with most fibers arranged more or less longitudinally. Prostate glands, in pyriform bundles of up to about 20 cells, loosely cover the atrial ampullae; prostates about 40–80 µm long; histology as described for A. freidris (see above).

Atrial duct expands abruptly at ectal end, forming a pyriform to cask-shaped penial structure, 130 (60–280) µm tall by 76 (40–125) µm wide (not including the irregular peritoneum); length about 2 times width (varies among populations) when penes are not extended ( Figs. 8, 9, 10H–K). Penial structure surrounded by a muscle layer 2.5 (1–6) µm thick; mostly transverse-circular muscle in specimens from the type locality, but in some other material a distinct longitudinal layer surrounds the circular layer. Epithelium of penial structure produced into irregular lamellae, forming an irregular lumen with thin cuticle ( Fig. 10I–M). Epithelial cells elongate, with basal nuclei and indistinct boundaries. Extruded penes of preserved worms 75 (up to 160) µm long, usually short and blunt ( Figs. 9, 10L–M). Ectal end of penial structure may extend a short distance out of the body, forming base of penis, but penis mostly formed by extrusion of epithelial cell extensions into a narrow tube; nuclei mostly remaining inside the penial structure; internal dimensions of the penial structure may be considerably reduced after extension.

Remarks. Altmanella idahoensis is distinguished from A. freidris by the shorter, thicker penial structures, the short atria with a thin muscle layer, and the more ental junction of the vasa deferentia with the atria. In contrast to A. freidris , in which the penial structures taper gradually, those of A. idahoensis narrow abruptly to form the base of the atrial duct. The penial structure of A. idahoensis has a wide, irregularly convoluted lumen, in contrast to the narrow, indistinct lumen of A. freidris ( Figs. 10I–M vs. 6H–K). The structure appears to partially evert with penis extension, rather than simply extruding cell extensions, as indicated by the deeply folded lumen and by an inverse relationship between length of extruded penis and size of the internal penial structure (cf. Figs. 8A vs. 8B). The atrial ampulla is distinguished from the atrial duct only by the presence of prostates, and does not have a thickened muscle layer ( Figs. 10E–G vs. 6C–F). Unlike A. freidris , the ampulla often is expanded, with thin epithelium and a wide lumen ( Fig. 10G); this is variable among specimens, and is likely related to reproductive state. Other lumbriculids have been described as going through a similar process, i.e. erosion and thinning of atrial epithelium and general loss of structure at a late stage of maturity (e.g. Timm 1998). The vas deferens of A. idahoensis joins the ampulla near the ental end, rather than near the base ( Figs. 8, 9 vs. 4, 5). Although most of these characters appear variable when quantified ( Table 1), examination of over 100 specimens from the sites where both morphotypes occurred (the Sacramento River, California and Spring Creek, Oregon) did not produce any intergrades ( Figs. 4A, 5E–F vs. 8D, 9L–M and 5L vs. 9O).

There appear to be minor morphological differences among regions. Worms from the type locality and nearby sites (central Idaho) generally had relatively small, compact penial structures, somewhat tapered towards the ental end. Specimens from northern Idaho (Clearwater River) and California ( Sacramento River ) tended to have larger, more ovate penial structures with a more distinct lumen, and more abrupt transition to the atrial duct. However , due to differences in fixation protocol, almost all of the specimens from the latter collection were in a much more relaxed state, with penes (and pharynx) retracted. Because the A. idahoensis penes are extruded by eversion of the penial structures, some of this apparent difference may be an artifact .

The atria were highly variable among populations, although there did not appear to be a large-scale clinal trend. The Marys River worms had the shortest atria; these were shorter than the penial structures in the few available specimens ( Fig. 9I). The Spring Creek (Oregon) population was the most anomalous; all representatives in a good series of specimens had exceptionally elongate atria ( Fig. 9O). Other aspects of the male ducts also were enlarged in these specimens; the vasa deferentia were unusually thick (to 40 µm, versus up to 28 µm at other sites), and the atrial muscle layer was as thick as 6 or 7 µm (1–3 µm at most other sites). The Deschutes River (also Oregon) worms also appeared to have a thicker atrial muscle than specimens from other sites, although this appeared to be a general thickening of the entire structure, rather than a distinctly thickened ampulla. Poor histological fixation may have been a factor here, as these specimens were fixed in straight formalin without prior relaxation; consequently the tissues appeared shriveled and distorted. Although inclusion of the Spring Creek population within idahoensis creates overlap in atrial measurements with A. freidris ( Table 1), these specimens had typical idahoensis -like penial structures, and the vasa deferentia entered the atrial ampullae subapically ( Fig. 9O). Additionally, they differed sharply from A. freidris collected at this site ( Fig. 5L).