Pectinodrilus ningaloo 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 : 34-36

Pectinodrilus ningaloo Pinder n. sp. ( Fig. 2 )

Holotype. WAM V 4442 . Specimen whole­mounted under right coverslip on same slide as paratype WAM V 4443 , from groundwater in Ningaloo Homestead Well, about 500 m from the ocean, Ningaloo Station , Cape Range , Western Australia ( Fig. 1 ), 22º42’S 113º41’E, 11 June 1993. Temperature 22.8°C, conductivity 0.66 mS cm ­1, total dissolved solids 360 mg L ­1. Coll. R. D. Brooks, WAM collection # BES 2230).

Paratypes. WAM V 4443 and 4444. One mature with head and tail missing, wholemounted under left coverslip on same slide as holotype and 1 mature with tail missing, whole­mounted on separate slide, collection details as for holotype .

Other material. WAM V 4445 . Two immature of uncertain identity in alcohol, collection details as for holotype .

Description. Length and number of segments of holotype 8.2 mm and 61 respectively, maximum width of slide­mounted worms 0.14–0.20 mm at segment XI. Clitellum from posterior 1/3 of X to 12/13, more glandular, but not thicker, than epidermis of pre­clitellar segments. Post­clitellar segments with epidermis thinner than anterior segments. Male pores ventro­lateral on XI about 4/5 distance between 10/11 and 11/12. Spermathecal pores ventro­lateral immediately behind 9/10. Female funnels ventro­lateral at 11/12.

Prostomium elongate oval, length:height at base 1.5, with large round clusters of cells with nuclei on the periphery, lying beneath the epidermis and projecting into the coelom. Pharynx in II/III. Pharyngeal glands, consisting of large irregular cells, mostly lateral and dorsal to the gut in IV–VI. Rest of ciliated digestive tract of variable width but not enlarging in pre­genital segments. Large dorsal and smaller ventral blood vessels connected by commissural vessels in II–V and by a plexus of capillaries surrounding the gut from VI. From VI or VII onwards, gut surrounded dorsally and laterally by large chlorogogue cells with non­staining cytoplasm occupying up to half of the coelom in many segments. Coelomocytes not observed. Chaetae 3(4–5)/bundle anteriorly, reduced to 2 posteriorly, 32–40 µm long x 1.5–1.8 µm wide at nodulus, bifid with sharp teeth, the upper tooth about half as long as lower, the nodulus distinctly distal. Straight penial chaetae 10–19/bundle in XI, protruding from body wall on a rounded papilla anterior to the male pores. Penial chaetae 32–36 µm long x ~ 1–1.5 µm wide at the base, tapering slightly towards their tips which appear to be slightly swollen and minutely hooked, but tips difficult to see as chaetae facing outwards.

Genitalia paired. Testes antero­ventral in X with sperm sacs from IX to XIII. Ovaries antero­ventral in XI with egg sacs extending to XIV. Asymmetrical sperm funnels ventrolateral on 9/10. Vasa deferentia ciliated and tripartite: a short, thin (7–8 µm wide) ental section with thin muscle layer, a longer, thicker (maximum width 20–27 µm) middle section with thick (2–3 µm) muscle layer and thicker lining tissue and an ectal section (11–17 µm wide) with thinner muscle layer and lining tissue intermediate in width between the ental and middle sections. Atria short (50–58 µm), upright and moderately muscular, leading to simple male pore in a shallow invagination (at least in preserved specimens) behind penial chaetae. Two small ovoid prostates associated with each set of male ducts, one ventral to the middle part of vasa deferentia and one posterior to atrium, connections with the male ducts not seen. Spermathecae variable in shape, size and expansion of the lumen, but ampullae about 3 times longer than maximum width (about 50 µm in 2 mated specimens), with a short constriction between the ampulla and a small ectal vestibule. Sperm in loose masses in ampullae.

Remarks. Members of the genus Pectinodrilus are united by the presence of small upright atria and the large number of penial chaetae, both characters that are clearly present in the new species. All previously described Pectinodrilus are marine meiobenthic and most have simple male ducts with a thin vasa deferentia leading directly into the atria. The new species, however, resembles a small number of species from the Southern Indian Ocean, Western Australia and south­east Asia ( Hong Kong) that Erséus (1992a; 1997a) considered to constitute a monophyletic group within Pectinodrilus . Members of this group share ‘multiple club­shaped and hooked penial chaetae’ and ‘various modifications and elaborations of the vasa deferentia’. Of these, Pectinodrilus multiplex (Erséus 1990) and Pectinodrilus hoihaensis Erséus 1992 have a tripartite vas like the new species but with the middle muscular section even more developed and forming a broad sperm storage organ and with P. multiplex also possessing another ampulla (atrium sensu Erséus 1992a) between the vas and a copulatory sac. The male ducts of the new species are not this complex but are more differentiated than some other species in the group such as P. marionensis ( Erséus 1979) and P. nervosus (Erséus 1990) , which have a small non­ muscular section of vas followed by a longer extremely muscular section leading directly into a muscular atrium. Other members of this subgroup are P. glomeriductus Erséus 1997 , which has highly coiled vasa and P. vitreus Erséus 1993 which has bi­partite vasa that are not as muscular as those of P. marionensis and P. nervosus ).

Etymology. Named for the type locality: a bore next to the homestead on Ningaloo Station.

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 2. Pectinodrilus ningaloo n. sp. A, Genitalia of holotype (scale bar 100µm); B, anterior chaeta.