Altmanella freidris ( Cook, 1966 ) Fend, En. V., 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 : 7-13

Altmanella freidris ( Cook, 1966) n. comb.

Figures 2A–B, 3–6

Kincaidiana freidris Cook, 1966 p. 10 , Figures 2B, 5C, 5E–H

Material examined: Paratype. California: Lake Tahoe , USNM 32999 (accession no. 260570), 2 slides of whole mounts and 1 transversely sectioned worm

Other material. California: Mariposa Co.: Merced River at Pohono Bridge, Yosemite, 5-Oct-04, coll. S. Fend, 1 dissected. Mendocino Co.: Inglenook Fen at MacKerricher State Park near Fort Bragg, 2-Jul-05, coll. S. Fend, 3 whole mounts. Nevada Co.: Mason Fen, Sagehen Creek, 15-Jul-05, coll. S. Fend, 4 whole mounts. Placer Co.: Lake Tahoe, coll. S. Fend, 2 whole mounts. Shasta Co.: Sacramento River at Balls Ferry 21-Oct- 96, coll. S. Fend, 2 whole mounts. Tehama Co.: Sacramento River at Bend 13-May-01, coll. S. Fend, 19 whole mounts, 4 dissected, 1 sectioned. 26-May-02, 9 whole mounts, 4 dissected. Oregon: Douglas Co.: lower Cow Creek, 29-Oct-04, coll. R. Wisseman, 2 whole mounts. Jackson Co.: Rogue River at Gold Hill, 28-Apr- 04, coll. S. Fend, 1 whole mount. Klamath Co.: Mountain Lion Spring, 13-Jan-92, coll. R. Wisseman, 1 whole mount. Klamath River above Malone Dam, 2-Sep-99, coll. R. Wisseman, 1 whole mount. Spring Creek at Williamson River, 23-Jun-08, coll. J. Carter, 4 whole mounts. Upper Klamath Lake, 18-Apr-06, coll. J. Kuwabara, 7 whole mounts, 1 dissected. 31-May-06, 2 dissected, 6 whole mounts. 2-May-07, 4 dissected. Upper Klamath Lake, 1-May-08, coll. S. Fend, 21 whole mounts, 4 dissected. Lake Co.: Coyote Spring, Sycan Marsh, 22-Jun-01, coll. S. Fend, 7 whole mounts. Malheur Co.: Malheur River at Bohna, 24-Mar-03, coll. D. Gustafson, 1 whole mount, 1 dissected. Owyhee River at Birch Creek, 25-Mar-03, coll. D. Gustafson, 4 whole mounts, 2 dissected. Owyhee River at Rome, 26-Mar-03, coll. D. Gustafson, 4 whole mounts, 5 dissected, 2 sectioned. Owyhee River at Snively Hot Spring, 23-Mar-03, coll. D. Gustafson, 1 whole mount, 2 dissected. Succor Creek at State Park, 25-Mar-03, coll. D. Gustafson, 1 whole mount.

Supplemental description. Length of preserved worms 12 (5–22) mm; segments 55 (22–102); diameter 0.39 (0.19–0.56) mm in X, maximum diameter to 0.64 mm ( Figs. 2A–B, 3A–B). Low values for length and segment number are from the Upper Klamath Lake population; regional summaries of these and other selected measurements are given in Table 1. Chaetae simple-pointed, sigmoid; length 98 (74–122) µm in clitellar region, 94 (67–116) µm posteriorly; nodulus approximately 1/3 the distance from tip (0.25–0.54). Pharynx with ventral wall thin; dorsally thickened in I– II. Pharyngeal glands usually in IV – VI, sometimes to VII.

First nephridia usually paired on 6/7; second pair usually on 11/12; nephridia occur irregularly (approximately every third to fourth segment) in posterior segments. Each nephridium with small anteseptal funnel, an ovate postseptal expansion (length about 60 µm, diameter 30–40 µm), and a long, convoluted duct (10–16 µm wide) that may pass through anterior or posterior segments ventral to the gut, terminating in a short duct to a nephropore anterior to the ventral chaetae. Ectal ducts widen slightly at the nephropore, forming a small vesicle 26–70 µm long by 17–38 µm wide; vesicle differs from tubule in having regular, densely packed lining cells and a distinct lumen ( Fig. 3C–D).

One pair of thick, convoluted commissural blood vessels in II – IX; those in VIII and IX usually thinner, and may form short posterior loops into sperm and egg sacs; lateral blood vessels absent posteriorly. Perivisceral sinus and chloragogen begin in about VII; a variably-developed dorsointestinal blood vessel usually present underneath the more prominent dorsal vessel.

Spermathecae usually extend back into X, but may terminate in any segment from IX –XI. Spermathecal ampulla usually elongate-ovate, mean length 285 µm, mean width 150 µm ( Fig. 4). A very thin muscle layer surrounds the ampulla; the epithelium is usually very thick (20–50 µm) and vacuolated except at the ectal end, where it is thin (about 10 µm) and cuboidal ( Fig. 6A–B). Sperm loosely distributed throughout or concentrated in the ectal half; vacuoles of epithelium usually appear to contain sperm cells ( Figs. 4B, 6B). Spermathecal duct distinct, tubular, length 250 (105–360) µm; diameter at middle 20 (15–32) µm. Duct formed of tightly packed, regular epithelium, surrounded by a distinct layer of transverse-circular muscles, about 2–4 µm thick. The duct terminates in a narrow, cylindrical vestibule, length 156 (60–230) µm, width 45 (22–70) µm; histology of the vestibule similar to that of the duct. Spermathecal pore may be on a slight papilla.

Male funnels on 8/9, directed forward into VIII or back into sperm sacs; occasionally extending back to mid-IX. Funnels about 100 µm wide, not very convoluted. Vasa deferentia relatively short and thick (about as thick as the atrial duct); length about 500 µm; width 21 (15–28) µm; ciliated. Vasa do not penetrate the posterior septum; they penetrate the atrial muscle layer near the ectal end of the ampulla, run under the muscle, and enter the atrial lumen subapically ( Figs. 4, 6G).

Atria usually pass through septum 8/9 into IX, but may extend forward to VII or back as far as X. Atria have a long duct (length 350 [140–750] µm, width 29 [18–38] µm) and elongate- cylindrical ampulla (length 370 [180–700] µm, width 64 [41– 86] µm) ( Figs. 4, 5). Atrial epithelium of cuboidal to slightly columnar, ciliated cells; at maturity the epithelial cells appear granular and weakly defined; lumen usually narrow, diameter 11 (5–25) µm. Atrial muscle layer distinct, 7 (4–12) µm thick in ampulla, with fibers arranged in a longitudinal outer layer, surrounding a thin (1 µm), circular layer ( Fig. 6C–F). Prostate glands loosely cover the ampullar portion in distinct, pyriform bundles of up to about 20 cells, 40–80 µm long. Ampulla gradually narrows to form the duct, which (in addition to being about half the diameter) is distinguished from the ampulla by the thin (1–2 µm) muscle layer and absence of prostates.

Atrial duct gradually expands at its ectal end, forming a slightly tapered, elongate penial structure, 260 (130–530) µm tall by 65 (48–89) µm wide (length about 4 times width) when penes are not extended ( Figs. 4, 5); dimensions of the internal penial structure highly variable within populations, appearing slightly reduced after extension. Penial structure surrounded by a thick 7 (4–10 µm) outer layer of longitudinal muscle fibers and a thin (1–2 µm) inner layer of circular-transverse fibers ( Fig. 6H–K). Epithelial cells elongate, with basal nuclei and indistinct boundaries, surrounding a narrow (about 10 µm) lumen, which may be indistinct and irregular ( Fig. 6I). Penes of preserved worms usually at least partially extended; external portion to over 200 µm (mean 125 µm) long, cylindrical with slightly expanded tip, usually curved or bent forward. Penes apparently formed by extrusion of epithelial cell extensions into a narrow tube (which appears to have a thin cuticular lining) ( Fig. 6J); nuclei mostly remaining inside the penial structure; lumen of penis narrow (2–3 µm).

Remarks. Altmanella species are small, delicate worms, and morphological details can vary with minor differences in fixation. This likely accounted for some of the differences in measurements within and among collections ( Table 1). Rapid fixation using FAA or Bouin’s solution may cause contraction of the atria and eversion of penial structures, but material collected in straight formalin or strong alcohol generally appears shriveled and tissues are distorted. Histological details in the text descriptions were based on worms that were relaxed before fixation in FAA, and appeared to be in good condition.

Despite preservation artifacts and real population differences, worms determined here as A. freidris are distinguishable from their congeners (see below) by the elongate penial structures, which gradually taper to form the atrial duct, and the narrow, elongate atrium. Histological details of the male structures are also distinctive; both the penial structure and atrial ampulla have a relatively thick longitudinal muscle layer and a narrow lumen. Penes appear to be formed by elongation and extrusion of epithelial cells of the penial structures; there did not appear to be a strong relationship between length of the internal penial structure and the extended penis.

Material from the type locality was limited, as the description was based on few specimens, and only two new specimens were available. Although the whole mounts from the type series lacked histological detail, the general form of the male structures was similar to other material described here ( Figs. 5A–B). Additionally, histological details of the single sectioned worm ( Fig. 6C, H) from the type series match the present redescription. Specimens from a nearby Sierra Nevada locality (Mason Fen) are also of this type ( Fig. 5C–D). Cook (1966) described the A. freidris atrium as having a “thin muscular wall”, although Figures 5G and 5H of that publication illustrated the atrium with a substantial muscle layer, thick epithelium, and narrow lumen, similar to the present material attributed to A. freidris . Figure 5E in Cook (1966) illustrated atrial proportions and a junction of the vasa deferentia with the atrial ampulla in accordance with the new material and in contrast to Altmanella idahoensis n. sp. (see below).

There appears to be some regional variation in A. freidris populations, as Sierra Nevada (California) and Upper Klamath Lake (Oregon) specimens generally had shorter atria than worms from most other populations ( Table 1). Most Upper Klamath Lake worms had relatively short atrial ampullae ( Fig. 5J–K), but a few had longer atria ( Fig. 5I), similar to worms from river and spring habitats in the region ( Figs. 4B–C, 5G–H). Additionally, the Upper Klamath Lake specimens were markedly shorter than those from other populations, with only about half the number of segments ( Table 1). Whether this variation reflects responses to lake conditions or genetic differences is unknown; certainly, other lake-dwelling lumbriculid populations have been described as differing in somatic characters from related populations in other habitats (e.g., deep-water Rhynchelmis komareki Hrabĕ lacks a proboscis [ Hrabĕ 1931]; and a Lake Tahoe form of Rhynchelmis rostrata Eisen has modified chaetae [ Fend & Brinkhurst 2000]).

Two characters related to the nephridia are noteworthy, and may be useful in separating immature specimens of the western Altmanella from other small lumbriculids. First, the ectal vesicles are uncommon within the family, although similar structures occur in a few species within other genera. Second, the occurrence of the first post-genital nephridia on 11/12 appears to be a forward shift from the more usual position of 12/13. This is likely related to the apparent forward shift of reproductive organs.