Sphaerodoropsis exmouthensis Hartmann-Schröder, 1981

Capa, Maria & Bakken, Torkild, 2015, Revision of the Australian Sphaerodoridae (Annelida) including the description of four new species, Zootaxa 4000 (2), pp. 227-267 : 245-247

Sphaerodoropsis exmouthensis Hartmann-Schröder, 1981

Figs 1 D–I, 4G–H, 5G, 8

Sphaerodoropsis exmouthensis Hartmann-Schröder, 1981: 44 , Figs 94–99; 1984: 31; 1986: 51.

Material examined. Holotype ZMH P.16493: Western Australia, Exmouth, Tantabiggy Creek, in sand on the reef plateau, 11 Oct. 1975. Paratype MZH P.16494 (1 spec.) same sample. Additional material. ZMH P.16995 (1 spec. for SEM), Drummonds core, Geraldton, Western Australia, Australia; in fine sand with seagrass, 22 Oct 1975.

Diagnosis. Ellipsoid body with strongly convex dorsum. Four longitudinal rows of sessile and spherical (sometimes pear-shaped) dorsal macrotubercles and three transversal rows (total up to 11) of dorsal spherical papillae per segment. Distance between dorsal-most macrotubercles exceeding distance between those and lateral ones. Parapodia with long digitiform acicular lobe, shorter ventral cirrus and a single rounded papilla on anterior distal end. Four or five chaetae per parapodium, with thin shafts slightly enlarged distally and lacking spinulation, and short blades (5–7 times longer than wide), serrated and with smooth distal end. Males with ‘copulatory organ’ as conical papillae ventral to ventral cirri between chaetiger 6 and 7.

Re-description. Measurements and general morphology. Male, body ellipsoid, measuring 1.3 mm long and 0.42 mm wide, with 19 chaetigers. Tegument with transverse wrinkles, segmentation inconspicuous. Dorsum convex and ventrum flattened. 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, ellipsoid, about one half of the size of lateral antennae ( Figs 1 D–E, 8A–B). Antenniform papillae absent ( Figs 1 D– E, 8A–B). Up to 10 spherical papillae confined by prostomial appendages and the mouth ( Figs 1 D–E, 8A–B). A pair of tentacular cirri similar in shape and size to median antenna and palps and several scattered papillae similar to prostomial ( Fig. 8 A–B).

Tubercles. First chaetiger with two macrotubercles, slightly smaller than following, spherical and sessile ( Figs 1 D, 8A). Rest of chaetigers with four macrotubercles each, arranged in four longitudinal rows along dorsum ( Figs 1 F, 4G, 8A). Distance between mid-dorsal rows is similar or slightly larger than between these and lateral macrotubercles ( Figs 1 A, 4G). Lateral macrotubercles are slightly smaller than dorsal ( Figs 1 F, 8A). Spherical papillae are present over dorsum, arranged in three transversal rows per segment ( Figs 4 G, 8A). Around 6–8 papillae between mid-macrotubercles and around 2–3 between these and the lateral ones in mid-segments, papillae closer to macrotubercles slightly larger than the rest ( Figs 4 G, 8A, D). None to two papillae between lateral macrotubercles and parapodia ( Fig. 8 D). Ventral surface with spherical papillae, arranged in 2–3 transversal rows, with a total of 9–13 papillae in mid-body segments; numbers decreasing towards posterior end ( Figs 1 G, 4H), with a group of three near the base of parapodia and a midline group of 5–7 papillae, being the anterior larger. Body epithelium with ellipsoid granules.

Parapodia. Parapodia sub-conical, about 1–2 times longer than wide. First chaetiger with a long (as long as parapodia), digitiform acicular lobe projecting distally; ventral cirri shorter and wider ( Fig. 8 D), parapodial papillae absent. Second and following chaetigers similar or with longer acicular lobes, and one dorso-anterior spherical papillae ( Figs 5 G, 8C).

Chaetae. Compound chaetae present in all chaetigers, arranged in a curved transverse row around acicular lobe, numbering 3–5 per fascicle ( Figs 5 G, 8C–D). Shaft with slightly widened distal end and delicate, almost inconspicuous, spinulation. Blades similar in length along fascicles (5–7 times longer than maximum width), with fine and short spinulation along superior edge and a distal recurved tip ( Figs 1 H, 8E–G).

Pygidium . Pygidium terminal, with distal dorsal spherical papillae, a mid-ventral digitiform anal cirrus and a pair of pear-shaped dorsal anal cirri, slightly larger than macrotubercles ( Figs 1 I, 8H).

Internal features. Eyes not observed, muscular pharynx inconspicuous.

Reproductive features. Holotype, male, with ‘copulatory organs’ as conical papillae ventral to ventral cirri between chaetiger 6 and 7 ( Figs 1 G, 5H). Females have not been examined herein but there is a record of a gravid female with 13 chaetigers ( Hartmann-Schröder 1981).

Variation. Specimens measure 0.5–1.3 mm long and 0.25–0.42 mm width, in all cases body is about 4–5 times longer than wide. Paratype with eight chaetigers. Median antenna is in the three specimens examined shorter than lateral and no antenniform papillae have been observed in specimens examined. Prostomial papillae confined by antennae and mouth are less than 10. Macrotubercles are, in the specimen studied under SEM, not completely rounded and somehow pear-shaped ( Fig. 8 C–D). Number of epithelial papillae, including parapodial with a single papilla in all except first chaetiger, and arrangement seem to be constant. Parapodia do not exceed twice the length of the width. Number of chaetae range between 4–5 per parapodium. Length of blades shows a slight variation in number of chaetae and the relative length of blades. Examined specimens are not transparent and muscular pharynx was not conspicuous. Eyes have not been observed. ‘Copulatory organs’ only observed in holotype.

Remarks. In the original description there were some details lacking and others that have been interpreted differently herein. The palps and lateral antennae (referred to as outer and inner antennae respectively in original description) were described as being shorter and oval and digitiform to filiform but are considered here to be similar in shape and size. The arrangement of epithelial papillae both on dorsal and ventral body surface seems not random ( Fig. 8 A). Parapodia were described with a rounded papilla on superior margin that has here interpreted as anterior; chaetae were considered as smooth but fine dentation is observed under SEM. Pygidial macrotubercles as pear shaped (as drawn in original description, Hartmann-Schröder 1981).

Type loc al ity. Tantabiddy Creek, Exmouth, Western Australia ( Fig. 15 ).

Distribution. Western Australia (Exmouth and Geraldton; Fig. 15 ),?South Australia (Ceduna and Kangaroo Island) ( Hartmann-Schröder 1981, 1984, 1986). South Australian material needs confirmation; they could belong to Sphaerodoropsis wilsoni n. sp. described below.

Habitat. Sand near reef plateau or sea-grasses, shallow depths.

Figures

FIGURE 1. Light micrographs. A – C. Ephesiella australiensis, holotype ZMH P. 16773. A. Anterior end, frontal view, showing head appendages and papillae. B. Mid-body macrotubercle, side view. C. Mid-body microtubercle, side view. D – I. Sphaerodoropsis exmouthensis, D, F – H, holotype ZMH P. 16493, E, I, paratypes ZMH P. 16494. D. Anterior end, lateral view, showing head appendages and papillae. E. Same, frontal view. F. Anterior chaetigers, side view, showing dorsal tubercles and parapodia. G. Chaetigers 6 and 7, side view, with digitiform copulatory organ ventral to ventral cirrus chaetiger 6. H. Chaetal fascicle, mid-chaetiger. I. Posterior chaetigers and pygidium, ventral view. Abbreviations: al, acicular lobe; co, copulatory organ; la, lateral antenna; ma, median antenna; mc, macrotubercle; pa, palp; tc, tentacular cirrus; vc, ventral cirrus; 1 st, parapodium first chaetiger.

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 8. Sphaerodoropsis exmouthensis, ZMH P. 16995, scanning electron micrographs. A. Whole specimen, dorsal view; anterior end on top. B. Detail of anterior end and head appendages. C. Mid-body parapodia and row of lateral macrotubercles, anterior view. D. Parapodium first chaetigers, anterior view. E. Chaeta mid-body chaetigers. F. Same. G. Chaeta posterior chaetiger. H. Posterior chaetiger and pygidium. Abbreviations: al, acicular lobe; la, lateral antenna; ma, median antenna; pa, palp; tc, tentacular cirrus; vc, ventral cirrus.

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.