Sphaerodoropsis longofalcigera, 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 : 254-256

Sphaerodoropsis longofalcigera n. sp.

Fig. 4 O–P, 5J, 12

Material examined. Holotype: NMV F.162479 off Pelsart Island, Geraldton, Western Australia, 29° 00' 06'' S, 113° 46' 15'' E, 409 m, 0 1 Aug 2005. Paratypes: NMV F.162484 (1 spec.), Abrolhos region, 28° 59' 15'' S, 113° 45' 34'' E, 388 m, 30 Jul 2005; NMV F.162483 (1 spec.), Two Rocks region, north of Perth, Western Australia, 31° 39' 25'' S, 114° 58' 31'' E, 403 m, 0 4 Aug 2005.

Comparative material. S. anae Aguado & Rouse, 2006 , holotype, MNCN 16.01/10817; S. artabrensis Moreira & Parapar, 2007 , holotype, MNCN 16.01/11043; Sphaerodorum biserialis Berkeley & Berkeley, 1944 , holotype, NMNH 32867; S phaerodoropsis corrugata Hartmann & Fauchald, 1971, holotype, LACM-AHF POLY 950; S. discolis Borowski, 1994 , paratypes, ZMH P.21951, ZMH P.21952; S. elegans Hartmann & Fauchald, 1971 , holotype, LACM-AHF POLY 954, paratypes, LACM-AHF POLY 955; S. furca Fauchald, 1974 , holotype, LACM- AHF POLY 951; S. laureci Desbruyères, 1980 , holotype, MNHN TYPE 1286; S. longianalpapilla Böggemann, 2009 , paratypes, ZMH P.25538; S. longipalpa Hartmann & Fauchald, 1971 , holotype, LACM-AHF POLY 948; S. longisetis Fauchald, 1972 , holotype, LACM-AHF POLY 964; S. longopapillata Desbruyères, 1980 , holotype, MNHN TYPE 1283; S. protuberanca Böggemann, 2009 , holotype, ZMH P. 25557, paratypes, ZMH P.25556; S. sibuetae Desbruyères, 1980 , holotype, MNHN TYPE 1284; S. triplicata Fauchald, 1974 , holotype, LACM-AHF POLY 958, paratypes, LACM-AHF POLY 958; S. vittori Kudenov, 1987a , holotype, NMNH 102792; Sphaerephesia longiseta Fauchald, 1972 , holotype, LACM-AHF POLY 964.

Diagnosis. Body cylindrical, slightly tapering posteriorly. Four longitudinal rows of sessile and hemispherical dorsal macrotubercles and four transversal rows of small spherical papillae per segment. Distance between dorsalmost macrotubercles exceeding distance between those and lateral ones. Parapodia with short and wide acicular lobe, thinner ventral cirrus and a single rounded papillae on anterior surface. Around 10 chaetae per parapodium, with thin shafts slightly enlarged distally and lacking spinulation, and blades ranging in length within fascicles (8– 25 times longer than wide), finely serrated.

Description. Measurements and general morphology. Body cylindrical, measuring 1.2 mm long and 0.3 mm wide, with 14 chaetigers. Tegument with some transverse wrinkles, segmentation inconspicuous ( Fig. 12 A). Preserved specimen lacking pigmentation.

Head. Anterior end bluntly rounded ( Fig. 12 A–B). Prostomium with seven 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 rounded median antennae, about one half of the size of lateral antennae ( Fig. 12 B). Antenniform papillae as long as median antenna but thinner ( Fig. 12 B). A pair of tentacular cirri similar in shape and size to median antenna and palps ( Fig. 12 B). Several small and hemispherical scattered papillae cover the head.

Tubercles. First chaetiger with two macrotubercles, slightly smaller than following, hemispherical. Rest of chaetigers with four macrotubercles each, similar in shape and size, arranged in four longitudinal rows along dorsum; distance between mid-dorsal rows slightly larger than between these and lateral macrotubercles ( Fig. 4 O). Spherical papillae are present over dorsum, arranged in four transversal rows per segment, total number difficult to assess. Ventral surface with spherical papillae, at least one ventral to each parapodium, but total number not possible to ascertain ( Fig. 4 P).

Parapodia. Parapodia sub-conical, about 2–3 times longer than wide ( Fig. 12 C–E), with a wide and short acicular lobe and ventral cirri similar in length, but thinner; ventral cirri decrease length towards posterior chaetigers. One spherical parapodial papilla on anterior surface of parapodia ( Figs 5 J, 12D).

Chaetae. Compound chaetae present in all chaetigers, arranged in a curved transverse row around acicular lobe, numbering around 10 per fascicle ( Figs 5 J, 12B–E). Shaft narrow with slightly widened distal end and inconspicuous spinulation (under compound microscope). Blades, thin and straight, of a wide range of lengths within same fascicle, ranging from eight to more than 25 times longer than wide ( Fig. 12 C–E). Longer blades in mid fascicle, and shorter in dorsal and ventral positions.

Pygidium . Pygidium terminal, with distal dorsal pear-shaped papillae and mid-ventral digitiform anal cirrus, slightly larger than posterior macrotubercles.

Internal features. Eyes not observed. Muscular pharynx occupying chaetigers 2–7 ( Fig. 12 A).

Reproductive features. Holotype, female with about 10 eggs measuring 150 µm, occupying the coelom, behind the muscular pharynx. Enlarged ventral cirri on chaetigers 4 and 5, may indicate the presence of ‘copulatory organs’, but this should be confirmed.

Variation. The three examined specimens are small, measuring between 0.8 and 1.2 mm long, 0.1 and 0.3 mm wide, and having around 14 chaetigers, gametes have only been observed in the holotype. Shape and relative size of head appendages similar in all specimens, but in one paratype antenniform papillae not conspicuous. No specimens were observed under SEM therefore the number and arrangement of the small epithelial papillae has not been possible to ascertain, but all specimens seem to bear dorsal papillae arranged in four transversal rows and at least one ventral papilla, near the base of parapodia, as described for holotype. The most obvious feature in this species is the maximum length of blades, reaching in all specimens up to 25 times its width.

Remarks. Sphaerodoropsis longofalcigera n. sp. bears dorsal macrotubercles arranged in four longitudinal rows, in a single transversal row per segment, and therefore resembles other species in the artificial Group 1, proposed by Borowski (1994). Most of these species have falcigers with long blades (e.g. Aguado & Rouse 2006). But they are particularly long and thin in S. corrugata Hartman & Fauchald, 1971 , S. discolis Borowski, 1994 , S. elegans Hartman & Fauchald, 1971 , S. longianalpapilla Böggemann, 2009 , S. longipalpa Hartman & Fauchald, 1971 , S. triplicata Fauchald, 1974 , together with the new species since they are up to 15 times longer than wide or longer (Table 1). The new species is the one with longest blades reaching in some chaetigers up to 25 times the length of the maximum width. The new species resembles Sphaerephesia longiseta Fauchald, 1972 in this attribute, the sphaerodorid with longest falcigers described to date measuring 20–30 times their maximum width. Nevertheless S. longiseta is characterised, as its congeners, by the presence of terminal papilla on macrotubercles (conspicuous in lateral rows in the holotype of this species). Sphaerodoropsis longofalcigera n. sp. shares with S. laureci Desbruyères, 1980 , S. protuberanca , S. sibuetae Desbruyères, 1980 and S. triplicata the shape of dorsal macrotubercles, being hemispherical (not always described as such in original descriptions), while they are spherical or pear-shaped in the other species. Of these species, only S. protuberanca has similarly low number of parapodial papilla, more numerous in the other species ( Fauchald 1974; Desbruyères 1980).

After the revision of type material some attributes not referred to in original descriptions have been compared here (Table 1). Several inconsistencies in the interpretation of some morphological traits with respect to the original descriptions have also been encountered, including shape of macrotubercles and number of parapodial papillae (Table 1), and other characters that will be dealt with in a further study (e.g. none of the specimens examined presented postchaetal lobes, unlike indicated in some descriptions ( Fauchald 1974; Böggemann 2009).

Etymology. The name of the species is attributed to the long blade falcigers.

Distribution. Central Western Australia.

Habitat. Sediments around 400 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 12. Sphaerodoropsis longofalcigera n. sp., holotype, NMV F. 162479, light micrographs. A. Anterior end, dorsal view. B. Detail of head and first chaetiger, dorsal view. C. Parapodia chaetigers 7 and 8, dorsal view. D. Parapodial chaetigers 8 and 9, dorsal view. E. Parapodium posterior chaetiger. Abbreviations: al, acicular lobe; ap, antenniform papilla; eg, egg; la, lateral antenna; ma, median antenna; pa, palp; ph, pharyx; 1 st, parapodium first chaetiger.