Aktedrilus leeuwinensis 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 : 39-42

Aktedrilus leeuwinensis Pinder n. sp. ( Figs 5 and 6a )

Holotype. WAM V 4448 . Specimen whole­mounted, from sand and root mats (gently disturbed and caught in a net) in a pool area of a stream within Budjur Mar Cave , 34º06’00”S 115º02’50”E, 25 m asl, Leeuwin­Naturaliste Ridge, Western Australia ( Fig. 1 ), 29 June 2002, coll. S. Eberhard.

Paratypes. WAM V 4449 and 4450. Two mature whole­mounted, collection data as for holotype .

Description. Length and number of segments 2.4–5.5 mm and 39–42 respectively, width of slide­mounted worms at segment XI 0.11–0.16 mm. Clitellum from posterior 1/3 of X to end of XII, epidermis of genital segments not thicker, but more glandular, than that of somatic segments. Anterior­most somatic segments with a distinct secondary annulation about 1/4 of the distance from anterior to posterior intersegmental furrow. Male pores ventro­lateral, about 1/3 of the distance from 10/11 to 11/12, in the form of crescentshaped slits medial to small papillae. Single spermathecal pore mid­dorsal behind 10/11, often with ectal part of vestibule partially protruding. Female pores not seen.

Prostomium not much longer than tall, length:height at base 1.0–1.1, with loose clusters of cells below the epidermis. Pharynx in II/III. Pharyngeal glands, consisting of groups of large irregular cells, mostly lateral and dorsal to the gut in IV–VI. Digestive tract enlarging substantially between XI and XIV. Chlorogogue tissue present around gut but extent and distribution variable. Coelomocytes not observed. Chaetae 4–5/bundle anteriorly, reduced to 2(3)/bundle in post­clitellar segments, 25–30 µm long x 1.1–1.5 µm wide at nodulus, bifid with sharp teeth, the upper tooth 1/2 to 3/4 as long as lower, the nodulus distinctly distal.

Genitalia paired, except for spermatheca. Male funnels ventro­lateral on 10/11, feeding narrow (4 µm) ciliated vasa deferentia (ciliation not illustrated). Vasa deferentia partially obscured by anterior prostate, presumably joining narrow ental end of atria, but union not seen. Atria narrow entally, expanding abruptly into a broad sac (length 70 µm, width = 34 µm) then tapering ectally to form a short ejaculatory duct which joins penes apically. Atrial muscle layer thin, lining tissue cells particularly large but position of lumen unclear — possibly towards one side of widest part of atria in holotype but more central in some other specimens (apparent position perhaps depending on aspect of view). Penes lying in deep penis sacs and enclosed by narrow, tapering and curved cuticular sheaths ( Fig. 6 ), with the ental ends lateral to the gut and curving inwards (ventro­medially) so full extent of curve not seen from lateral view. Diagonal length of penis sheaths 20–25 µm. Penis sheaths of holotype presumably bent during lateral compression of specimen on slide ( Fig. 5 ). Details of penis sacs difficult to discern ( Fig. 5 is the authors’ interpretation) but each seeming to have a glandular lobe at least partially enclosing the penis but with uncertain attachment to the sac walls and of similar glandular histology to the prostate tissue, especially entally. Anterior prostates voluminous but connection to male ducts uncertain. Posterior prostate glands between the penis sac and septa 11/12, joining the male duct at the atrial/penis sac union. Spermatheca single, with a long ampulla (up to 141 x 37 µm), connected to the mid­dorsal pore by a smaller vestibule (up to 37.5 µm long x 29 µm). Loose sperm present in ampulla. Female funnels not seen. Egg sacs extending to XIII, sperm sacs from VIII–XIII.

Remarks. Details of the male genitalia of this species needs to be confirmed further when new material becomes available. Nevertheless, this species most closely resembles a number of Aktedrilus which share narrow and frequently curved and/or tapering penis sheaths: A. argatxae Giani and Rodriguez 1988 , A. mortoni Erséus 1984b , A. ruffoi Sambugar et al. 1999 , A. svetlovi Finogenova 1976 , A. longitubularis Finogenova and Shurova 1980 , A. oregonensis Strehlow 1982 , A. brevis Erséus 1980 and A. martiniquensis Erséus 1983b . The last four of these also have a glandular pad on the penis sac wall ( longitubularis , brevis , martiniquensis ) and/or a glandular lobe of tissue within the sac ( brevis , oregonensis ) associated with, or even representing the full extent of ( longitubularis , martiniquensis ), the posterior prostate gland. The precise anatomy of the penis sac and its interaction with the posterior prostate is not clear in the new species, but the narrow curved penis sheath and the suggestion of a glandular region within the penis sac indicates that A. leeuwinensis is allied with these marine intertidal species. Numerous features of these other species, however, distinguish them from leeuwinensis : martiniquensis and longitubularis have reduced posterior prostates and the former has simple­pointed chaetae posteriorly; longitubularis , oregonensis and brevis have more tubular atria; only oregonensis has a spermatheca with a well–defined duct/vestibule ectal to an ampulla (but with a much smaller ampulla than is present in leeuwinensis ) and all except brevis have sperm partly embedded within the ampulla walls. In addition, the shape and/or size of the penis sheath differs in all of these species. Aktedrilus longitubularis is widespread and has been recorded from Rottnest Island off the south–west coast of Australia whereas oregonensis , martiniquensis and brevis are known only from the coasts of the north–east Pacific, the West Indies and the south–west Atlantic respectively.

Etymology. Named after the geographical feature close to where the type material was collected: Cape Leeuwin.

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 5. Aktedrilus leeuwinensis. n. sp. A, Genitalia of holotype (scale bar 100µm); B, anterior chaeta.

FIGURE 6. Penis sheaths of A) Aktedrilus leeuwinensis n. sp. and B) Aktedrilus sp. from Turners Spring. Scale bar 25µm.