Sphaerodoropsis wilsoni, Capa, Maria & Bakken, Torkild, 2015

Capa, Maria & Bakken, Torkild, 2015, Revision of the Australian Sphaerodoridae (Annelida) including the description of four new species, Zootaxa 4000 (2), pp. 227-267 : 259-261

Sphaerodoropsis wilsoni n. sp.

Figs 4 S, T, 5L, 14

Material examined. Holotype: Jervis Bay, New South Wales, Australia. NMV F. 217161, 35° 06' 04" S, 150° 44' 18" E, 22. 4 m, 27 Jun 2008. Paratypes: NMV F.166667 (6 specs), same sample. Additional material. New South Wales: AM W.194299 (1 spec.), Murrays Basin, Jervis Bay, 35° 07' 30" S, 150° 45' 30" E, 17 Oct 1972, sand; AM W.42741 (1 spec.), east of Malabar, 33° 59' 11" S, 151° 17' 54" E, 83.7 m, 18 Jan 1996; AM W.42750 (2 specs), east of Malabar, 33° 58' 46" S, 151° 17' 54" E, 79.6 m, 19 Mar 1996. Victoria: NMV F.131344 (1 spec.), Eastern Bass Strait, 38° 32' 15" S, 146° 29' 24" E, 40 m, 11 May1998. South Australia: ZMH P.18249 (1 spec. for SEM), Denial Bay, Ceduna, South Australia, Australia. 1,2 m, 30. Nov. 1975. Western Australia: AM W.17728 (1 spec.), Horrocks, 28° 23' S, 114° 26' E, 17 Oct 1975, sandy reef platform with calcareous algae; AM W.42676 (1spec.), Two Peoples Bay, 2 km south-east of South Point, 34° 58' S, 118° 12' E, 10 m, 16 Dec 1983, dictyotalean algae.

Comparative material. Sphaerodoropsis laevis Fauchald, 1974 , holotype LACM-AHF POLY 0952; paratype LACM-AHF POLY 0953; Sphaerodoropsis martinae Desbruyères, 1980 , holotype MNHN Type 1285.

Diagnosis. Ellipsoid body with strongly convex dorsum. Four longitudinal rows of sessile and spherical dorsal macrotubercles and four transversal rows (with up to 38) of spherical papillae per segment. Distance between dorsal-most macrotubercles exceeds distance between those and lateral ones. Parapodia with digitiform acicular lobe, shorter ventral cirrus and a single rounded papilla on anterior end (often other two papillae, on anterior and posterior surfaces present). Four or six chaetae per parapodium with short blades (2–3 times longer than wide), serrated, with distal long spines; shaft with conspicuous spinulation.

Description. Measurements and general morphology. Body ellipsoid, measuring 2.3 mm long and 0.5 mm wide, with 20 chaetigers. Tegument with transverse wrinkles, segmentation inconspicuous ( Fig. 14 A). Dorsum convex and ventrum flattened ( Fig. 14 A). Preserved specimen lacking pigmentation.

Head. Anterior end bluntly rounded. Prostomium with five longer appendages, including a pair of digitiform palps, in ventral most position; a pair of lateral antennae similar in size and shape to palps; and a median antenna, about one third longer than lateral antennae ( Fig. 14 A–B). Antenniform papillae not observed. Around 15–20 spherical papillae are confined by prostomial appendages and the mouth ( Fig. 14 B). A pair of tentacular cirri similar in shape and size to lateral antenna and palps ( Fig. 14 B). Nuchal organ pits anterior to tentacular cirri ( Fig. 14 B).

Tubercles. First chaetiger with two macrotubercles spherical and sessile ( Fig. 14 A–B). Rest of chaetigers with four macrotubercles each, arranged in four longitudinal rows along dorsum. Distance between mid-rows is similar or slightly larger than between these and lateral macrotubercles. All macrotubercles similar in size, with distal pores arranged 4–6 groups ( Fig. 14 E). Spherical papillae over dorsum, arranged in four transverse rows per segment, adding 16–20 papillae between mid-macrotubercles, 6–10 between these and the lateral ones in midsegments, and 6–8 papillae between lateral macrotubercles and parapodia ( Figs 4 S, 14A, C). All papillae similar in size and shape. Ventral surface with spherical papillae, arranged in three transverse rows, with around 20 papillae in mid-body segments; numbers decreasing towards posterior end ( Figs 4 T, 14D). Body epithelium with microscopic granules.

Parapodia. Parapodia sub-conical, about 1–2 times longer than wide. First chaetiger with digitiform acicular lobe projecting; ventral cirri similar in shape and size, parapodial papillae absent. Second and following chaetigers similar, with one anterior spherical papillae, and sometimes a dorsal papilla and/or a ventral papilla close to base of parapodia ( Figs 5 L, 14A, C–D, F). Acicular lobe digitiform in middle chaetigers, longer than ventral cirri ( Fig. 14 C, D, F).

Chaetae. Compound chaetae present in all chaetigers, arranged in a curved transverse row around acicular lobe, numbering 7–8 per fascicle ( Figs 5 L, 14C–D, F). Shaft with widened distal end and fine and long spinulation on edge. Blades similar in length along fascicles, wide and short (2–3 times longer than maximum width), with fine and short spinulation along superior edge and a distal recurved tip ( Fig. 14 F–H). One or two long and thin distal spines present behind distal tip ( Fig. 14 G–H). Blades showing a design on their sides with an inverted V ( Fig. 14 G–H).

Pygidium . Pygidium terminal, with mid-ventral anal cirrus and a pair of dorsal anal cirri, all spherical and similar in size.

Internal features. Eyes not observed on holotype, but a pair of eyes has been observed on one specimen. Muscular pharynx rounded, from first to third chaetiger.

Reproductive features. ‘Copulatory organs’ not observed in types or additional material.

Variation. Specimens measure 1.2–3mm long and 0.5–0.8mm wide, body is about 3–4 times longer than wide, with around 20 chaetigers. Macrotubercles are in all specimens spherical. Relative length of head appendages show no variation with holotype and median antenna is longer to rest of prostomial appendages, and with a distal knob. Relative length/width of parapodia and number of parapodial papillae do not vary among specimens. The dorsal papillae observed in some parapodia of the holotype, could be considered as not parapodial in some types and additional material. Methylene blue stains the ventral parapodial gland and ventral cirri of all parapodia, but not the macrotubercles. Most preserved specimens present an opaque tegument and the presence of gonads, eyes or the shape and length of the muscular pharynx could not be assessed.

Remarks. The genus Sphaerodoropsis is very specious but only four species have been described as having four longitudinal rows of macrotubercles (Group 1 according to Borowski 1994) and falcigers with short blades ( Aguado & Rouse 2006). These are S. exmouthensis , re-described above; S. laevis Fauchald, 1974 (from Chile and Peru); S. martinae Desbruyères, 1980 (from the North-East Atlantic); and S. simplex Amoureux, Rullier and Fishelson, 1978 (from the Red Sea). Sphaerodoropsis wilsoni n. sp. differs from these species in the number of epithelial papillae. Sphaerodoropsis simplex was described without tubercles other than the macrotubercles, S. laevis only showed papillae around the head, and S. exmouthensis and S. martinae have only a few (less than 10 per segment), while the new species is densely covered with up to 38 papillae in mid-body segments. The new species shares some superficial morphological attributes with S. exmouthensis Hartmann-Schröder, 1981 (re-described above) and erroneous identifications have been found in collections. Some specimens identified as S. exmouthensis by Hartmann-Schröder (ZMH P.18249) belong in fact to S. wilsoni n. sp. Differences between these two Australian species are: the shape of macrotubercles (pear-shaped in S. exmouthesis and spherical in the new species), number and arrangement of epithelial papillae (scarce and different in size in S. exmouthensis and similar size papillae densely covering the surface in S. wilsoni n. sp.), and the morphology of chaetae (narrow shaft, longer blades and smooth distal end in S. exmouthensis , and wide shaft, short blades and distal spine in new species).

Etymology. This species is dedicated to Robin Wilson, a generous college and good friend, for his contribution to polychaete systematics and continuous efforts of making taxonomic information available for all of us.

Type locality. Jervis Bay, New South Wales ( Fig. 15 ).

Distribution. Along the southern Australian coastline (New South Wales, Victoria, South Australia and Western Australia) ( Fig. 15 ).

Ecology. Sand and algal communities, between 1–40 m depth.

Figures

FIGURE 4. Schematic illustrations of the type and arrangement of tubercles on the dorsal and ventral surface of mid-body chaetigers. The number at the left side of the drawing refer to the chaetiger number. A, C, E, G, I, K, M, O, Q, S: dorsal view. B, D, F, H, J, L, N, P, R, T: ventral view.

FIGURE 5. Schematic illustrations of the type and arrangement of parapodial and nearby structures and papillae. In all cases anterior faces left, posterior right, dorsal the top and ventral the bottom. The red cross centred in the middle of the parapodia divides each of the four hypothetical parapodial surfaces, and the concentric circles (larger at base, samller at tip) indicate the parapodial volume ..

FIGURE 14. Sphaerodoropsis wilsoni n. sp., ZMH P. 18249, scanning electron micrographs. A. Whole specimen, lateral view. B. Detail of anterior end and head appendages, lateral view. C. Mid-body chaetigers, dorsal view. D. Mid-body chaetigers, ventral view. E. Detail of lateral macrotubercle with invaginations and pores. F. Posterior parapodium and chaetal fascicle, anterior view. G. Chaetae mid-body chaetiger, with distal spine on blade (arrow). H. Chaetae posterior parapodia, with distal spine on blade (arrow). Abbreviations: al, acicular lobe; la, lateral antenna; ma, median antenna; mo, mouth; nu nuchal organ; pa, palp; tc, tentacular cirrus; vc, ventral cirrus; 1 st, parapodium first chaetiger.

FIGURE 15. Map of Australia with collecting sites of the different species found in Australian waters (as in Table 3). A. Outline of continental Australia. B. Detail of south eastern coastline and Macquarie Island. Type locality marked by numbers and plotted according to table 3. Abbreviations: NSW, New South Wales; NT, Northern Territory; SA, South Australia; TAS, Tasmania; QLD, Queensland; WA, Western Australia.