Aulodrilus paucichaeta Brinkhurst & Barbour 1985
Creators: name: Ohtaka, Akifumi
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Enchytraeida
Randiellidae
Aulodrilus
Aulodrilus paucichaeta

description: Aulodrilus paucichaeta Brinkhurst & Barbour, 1985
(Figure 16)
Aulodrilus paucichaeta Brinkhurst & Barbour, 1985: 931, fig 1.
Material examined. USNM 98228 (holotype), a whole-mounted mature specimen, Piscataway Creek, Maryland, U.S.A. 3 Oct. 1979, coll. M. T. Barbour. USNM 98229, 98230, 98232, 98234, 98236 (paratypes), five whole-mount- ed mature specimens, locality, date and collector the same as for the holotype. USNM 98235 (paratype), a mature specimen sagittally sectioned and mounted on two slides, locality, date and collector the same as for the holotype.
Brief description of the type series. Anterior-most six segments distinctly biannulate, each with a short anteri- or and a long posterior annulus, the latter with chaetae (Fig. 16A). Posterior end of 0.3 mm in length without chaetae and unsegmented. Dorsal and ventral chaetae alike, each with distal nodulus and bifid, with the upper tooth shorter and thinner than the lower tooth (Fig. 16B–D). Chaetal bundles consist of 2–3 chaetae in preclitellar segments and single chaeta in postclitellar segments. In the paratype specimen (USNM 98232), ventral chaetae 105 µm long in II, becoming larger in posterior segments, up to 190 µm. A single ventral chaeta in X, no chaetae in XI in mature specimen (USNM 98232). No modified genital chaetae. Spermathecae and male ducts paired in X and XI, respectively. Male funnels large, 200–300 µm in diameter (Fig. 16E). Vasa deferentia (Fig. 16F) more than 2 mm long, uniformly 38 µm wide, winding and connected with atria apically. Atria (Fig. 16G) tubular, 250 µm long, 50–80 µm wide with a tall (up to 50 µm) and glandular inner epithelium and muscular coverings. Prostate glands divided into several distinct lobes, connected with atria entally through a single short stalk (Fig. 16G arrow). Ejaculatory duct not detected, atrium leading directly to a large spherical penis in a large penial sac (Fig. 16E). Male pores located ventrally on chaetal line of XI. Spermathecal ampullae large (Fig. 16E), spherical or ovoid in shape and 500 µm in maximum diameter, opening laterally to ventral chaeta in X without spermathecal duct (Fig. 16H). Within spermathecal ampullae, sperm arranged in ovoid to spindle-shaped spermatozeugmata with hyaline outer layer (Fig. 16I).
Remarks. The present examination of the type series of Aulodrilus paucichaeta confirms the original description (Brinkhurst & Barbour 1985) in the following characters: few and robust, bifid chaetae with thick lower tooth, absence of modified genital chaetae and spermathecal ducts, lobed prostate glands and spherical penes in large and muscular penial sacs. On the other hand, the present examination found several differences from the original description. The original description noted the absence of ventral chaetae in IX in mature specimen, whereas a single ordinary chaeta was found in IX in one paratype specimen. The original description depicted a small and fusiform atrium and described prostate glands as attached to atria at one point, but not obviously stalked (Brinkhurst & Barbour 1985). However, the present reexamination confirmed that the atrium is tubular and the prostate gland is connected to the atrium by a short stalk (Fig. 15G). The original description stated that spermathecae are filled with sperm in bundles in mated specimens. However, the present examination suggests that sperms cells are arranged in ovoid to spindle-shaped capsules with a hyaline outer layer, similar to spermatozeugmata in many other tubificines. The very low number of chaetae and the extremely long and winding vas deferens are unique for Aulodrilus paucichaeta among species of the genus, suggesting that A. paucichaeta is not related closely to other congeners; this was also suggested by Finogenova & Arkhipova (1994), who highlighted the absence in this species of two characters which they considered diagnostic for the genus: the forward shift of genital organs and the lateral expansions of some chaetae, both absent in A. paucichaeta.
description: Published as part of Ohtaka, Akifumi, 2021, Taxonomical study of Japanese Aulodrilus Bretscher (Annelida, Clitellata Tubificinae) with descriptions of two new species, pp. 1-32 in Zootaxa 4952 (1) on pages 23-24, DOI: 10.11646/zootaxa.4952.1.1, http://zenodo.org/record/4671489