Aktedrilus podeilema Pinder, 2006

Pinder, Adrian M., Eberhard, Stefan M. & Humphreys, William F., 2006, New phallodrilines (Annelida: Clitellata: Tubificidae) from Western Australian groundwater, Zootaxa 1304 (1), pp. 31-48 : 38-39

Aktedrilus podeilema Pinder n. sp. ( Fig. 4 )

Holotype. WAM V 4447 . Incomplete specimen whole­mounted, from Tombstone Rocks Cave, about 9 km from the ocean, Nambung region , Western Australia ( Fig. 1 ), 30°41'S 115°14'E, 9 June 1998. Collected from sand and fine black silt with organic matter in a deep clear pool of freshwater. Coll. S. Eberhard (collection BES 5984).

Description. Body> 4.9 mm, number of segments> 40, width of slide­mounted worm 0.19 mm at segment XI. Body wall of genital segments not thicker or more glandular than that of somatic segments. Male pores ventro­lateral, each antero­medial to a small papilla, located about 2/3 of the distance between 10/11 and 11/12. Single mid­dorsal spermathecal pore located within lobes of the body wall (which may be partially everted walls of a vestibule). Female funnels not seen.

Prostomium bluntly conical, length:height at base 1.1, with thin lining tissue. Pharynx in II/III. Pharyngeal glands, consisting of irregularly shaped cells, dorsal to gut on posterior of 3/4 and lateral to gut on posterior of 4/5 and 5/6. Rest of ciliated digestive tract narrow with thin walls in III to X, slightly wider with thicker walls in genital region and much wider with even thicker lobed walls from XIV. Circulatory system not discernable. Chlorogogue tissue consisting of a single layer of cells with non­staining cytoplasm unevenly along the gut from VI. Coelomocytes not observed. Chaetae 4–6/bundle anteriorly, reduced to 3–4/bundle posteriorly, 33–48 µm long x 1–1.5 µm wide at nodulus, all bifid with sharp teeth, the upper tooth 1/2 to 3/4 the length of the lower and the nodulus slightly distal. Chaetal bundles of first few segments located 1/2 to 2/3 of the distance between anterior and posterior intersegmental furrows but most segments with bundles closer to the posterior septa. Ventral chaetae present but not modified on X, absent on XI.

Genitalia paired except for spermatheca. Testes antero­ventral in X with sperm sacs from IX to XIII. Ovaries antero­ventral in XI with egg sacs to XIV. Sperm funnels ventrolateral on 9/10. Ciliated, non­glandular vasa deferentia about 340 µm long x 7–11 µm wide with thin muscle layer. Vasa deferentia joining atria subapically. Atria broad (50 x 95 µm) with muscle layer (1.5 µm). Numerous muscle fibres attach atria to dorso­lateral body wall (especially the ectal portion of atria) and with muscle layer of atria binding atrium to penis sac walls. Atria opening apically into stout and asymmetrical penes which are covered by a distinct cuticular sheath with a pointed antero­ventral projection. Penis sacs opening to exterior ventro­laterally. Two prostate glands associated with each set of male ducts. Posterior prostates smaller than anterior ones, lying posterior to penis sacs and communicating with male duct where the atria join the penes. Anterior prostates lying anterior to atria in vicinity of vasa deferentia but connection to male duct not visible. One spermatheca present in X, consisting of a swollen vestibule with a narrow pore ectally and connected entally to an elongate ampulla via a constriction. Loose sperm in ampulla.

Remarks. Numerous other Aktedrilus possess cuticular penis sheaths. In particular, the asymmetrical sheaths of A. podeilema resembles those of two marine intertidal species: A. dentatus Erséus 1983b (from Brazil) and A. paradentatus Erséus 1984c (from Saudi Arabia). These two species, however, have other features (long tubular atria, posterior prostates attached broadly to the penis sacs and spermathecal pores posteriorly in IX or in intersegmental furrow 9/10) absent in the new species. Otherwise, A. podeilema , possessing a combination of asymmetrical penis sheaths, broad bipartite atria, long vasa deferentia and restricted connection between the posterior prostate and penis sacs, does not especially resemble any of its congeners.

Etymology. From the Greek podos (foot) and eilema (sheath) referring to the foot–shaped penis sheath.

Figures

FIGURE 1. Map of Western Australia showing major geological units and localities for 1) Pectinodrilus ningaloo, 2) Aktedrilus parvithecatus, 3) Aktedrilus podeilema, 4) Aktedrilus leeuwinensis and 5) Aktedrilus sp.

FIGURE 4. Aktedrilus podeilema n. sp. A, Genitalia of holotype (scale bar 100µm); B, anterior chaeta..