Sphaerodoropsis anae, Aguado, M. Teresa & Rouse, Greg W., 2006

Aguado, M. Teresa & Rouse, Greg W., 2006, First record of Sphaerodoridae (Phyllodocida: Annelida) from hydrothermal vents, Zootaxa 1383, pp. 1-21 : 3-8

Sphaerodoropsis anae n. sp.

( Figures 1–4 )

Material examined. Holotype ( MNCN 16.01/10817); 4 paratypes: MNCN 16.01/10818 (1 spec.), SAM E3634 (2 spec.), E3635 (1 spec.). Holotype MNCN 16.01/10818 and paratype MNCN 16.01/10818 collected by DSV Alvin Dive 4088: 37° 47.563S, 110° 54.963W depth 2216 m. Paratypes SAM E3634 and SAM E3635 collected by DSV Alvin Dive 4092: 31° 51.789S, 112° 02.534W depth 2334 m, and DSV Alvin Dive 4093 31° 51.869S, 112° 02.638W, depth 2235 m, respectively.

Other material examined. Sphaerodoropsis discolis Borowski, 1994 . Holotype SMF 4487 and paratypes SMF 4489–4502.

Sphaerodoropsis biserialis ( Berkeley & Berkeley, 1944) . 1 Paratype USNM 32862.

Diagnosis. Sphaerodoropsis with distinct proventricle; four macrotubercles per transverse row; dorsum covered by papillae; 4 papillae on dorsal edge of parapodia and several on each face; presence of prechaetal lobe; chaetal fascicles divided in two groups and bidentate compound chaetae with long spinulation.

Description. Holotype (MNCN 16.01/10817) complete, 4.5 mm long, 0.5 mm wide, with 22 chaetigers, adult specimen, female. Paratype (MNCN 16.01/10818) complete 5 mm long, 0.7 mm wide, with 24 chaetigers, male. Body shape, excluding parapodia, circular in section, ventrally flattened; body width fairly constant with tapering end ( Figs. 1 A, 2A). Colour white to pale in ethanol preserved specimens, without any distinguishable colour pattern. White to cream in live specimens ( Figs. 1 A–C). Anterior end rounded and broadly conical ( Fig. 4 A, B). Prostomium and first segments fused. Median antenna conical, slender and distally blunt. One pair of lateral antennae, both digitiform and longer than median antenna. Palps ventrally located conical, longer and wider than antennae ( Fig. 4 B). Eyes absent. Long papillae present on anterior margin of prostomium, all digitiform and slightly blunt on distal part, shorter and thinner than median antenna ( Fig. 2 B, 4B). One papilla at base of each lateral antenna slightly longer than those on anterior margin of prostomium. Segment 1 achaetous with one pair of digitiform cirri, similar in length to lateral antennae. Following segments annulated, with 4 rings per segment ( Fig. 3 A). Body papillae rounded, shorter than those on prostomium. Papillae cover dorsal and ventral sides of the body; organized on segmental annulae in four irregular transversal rows per segment, ( Figs. 2 A–C, 4C). Dorsal macrotubercles sessile, first chaetiger with only two macrotubercles, spherical ( Figs. 2 A, B). Three macrotubercles (two on one side) ( Fig. 4 A, B) present on Paratype SAM E3635. Remainder chaetigers with four macrotubercles in a transverse row ( Figs. 1 B, C, 2A, 3B, C, 4A). Lateralmost macrotubercles pear-shaped slightly tapered on distal part, with orange inclusions ( Figs. 3 B, C); distal tip in some invaginated ( Fig. 2 A). Median macrotubercles spherical, smaller than lateral ones, containing granular material ( Figs. 3 B, C).

Parapodia with wrinkled surface, increasing in length posteriorly along body. Last pair directed posteriorly ( Fig. 2 A). Anterior parapodial lobes conical and slender, 1/3 of the parapodia length ( Fig. 4 D). Prechaetal lobes and ventral cirri present; dorsal cirri and postchaetal lobes absent. Ventral cirri digitiform, slightly longer than parapodia, but not exceeding prechaetal lobes ( Figs. 3 B, C). Four papillae over dorsal edge of parapodia, one pair on either side of chaetae ( Fig. 4 D, E). Several papillae on each face of parapodium ( Figs. 3 B, C). Compound chaetae in two groups, one dorsal with 2–4 chaetae; second more ventral with 8–20 chaetae per fascicle in midbody parapodia ( Fig. 4 D, E). One straight acicula per parapodium. Compound chaetae all similar, with dorsoventral gradation in length (38 µm long dorsally, 29 µm long ventrally in midbody parapodia). Blades long and slender, distally unidentate via light microscope ( Fig. 3 D), but bidentate under SEM, with thin and curved distal tooth and small proximal tooth and thin spinulation on blade edge ( Figs. 4 F–H). Pygidium small, rounded with two spherical anal cirri, similar in shape to lateral macrotubercles, and one conical anal cirrus ( Fig. 2 A).

Two pairs of slightly brown pigmented pharyngeal glands extending through first chaetiger ( Figs. 2 A, B). Eversible pharynx, smooth distally (Paratypes MNCN 16.01/ 10818, SAM E3634) ( Figs. 1 C, 2D). Cylindrical proventricle well developed and visible through three segments, about 20, dark and continuous muscle cell-rows; muscle cells all similar in size ( Fig. 2 A). Holotype carrying numerous white ovoid oocytes with obvious nuclei ( Figs. 1 A, B).

Remarks. Borowski (1994) distinguished four different groups of Sphaerodoropsis species. Group 1 was identified by having four longitudinal rows of macrotubercles (except for first chaetiger in some species where there are two), and one transverse row per chaetiger. Group 2 includes species with more than four longitudinal rows of macrotubercles, and one transverse row per segment. In Group 3, species also present more than four longitudinal rows of macrotubercles, but two transverse rows per segment. Finally, Group 4 comprises species with macrotubercles randomly scattered over the dorsum, approximately in three to four transverse rows per segment.

Sphaerodoropsis anae n. sp., clearly matches the features characterizing Group 1, and is compared with all 20 species hitherto assigned to this group in Table 1. Bakken (2002) found two additional species of Sphaerodoropsis belonging to Group 1, but they were not named given the scarcity of specimens available, and these species are not included in Table 1. It is clear that S. anae n. sp., is most similar to S. biserialis ( Berkeley & Berkeley, 1944) . Both species share several characters such as the shape of antennae and macrotubercles and similar distribution of papillae. Additionally, drawings of chaetae made in the original description are very similar to the chaetae of S. anae . After study of one paratype of S. biserialis (see below), we conclude however that each species has different kinds of blades. Those of S. biserialis are unidentate (under light microscope) with thick hooked distal tooth and spinulation. Meanwhile, although blades of S. anae n. sp., appear unidentate (under light microscope), they are clearly bidentate under SEM ( Figs 4 F–H). Also, compared with S. biserialis , the distal tooth is curved but thin and the spinulation is also thin, being quickly distorted when exposed to electron bombardment (see Fig. 4 G). We include the drawings of chaetae of S. anae n. sp., in Fig. 3 as they are seen under light microscope, to facilitate comparison with other Sphaerodoropsis in absence of SEM pictures.

Sphaerodoropsis anae n. sp., differs from S. discolis Borowski, 1994 , another similar species, in having differences in shape and size of median and lateral macrotubercles; having a longer median antenna, several papillae on parapodia and the blades of compound chaetae are distally curved. Sphaerodoropsis vittori Kudenov, 1987 also presents some similarities since it has slender chaetae and several papillae on each face of parapodium, yet this species has four macrotubercles on first chaetiger and the blades of compound chaetae are not distally curved. Sphaerodoropsis triplicata Fauchald, 1974 presents hooked blades and only possesses two or three papillae over dorsal tip of parapodia. Sphaerodoropsis exmouthensis Hartmann-Schröder, 1981 has annulated segments, but there are only two rings per segment while in S. anae n. sp., there are four and the antennae, macrotubercles and chaetal shape are also different. Differences in shape of lateral and median macrotubercles of S. longiparapodium Katzmann, 1973 are similar to those of S. anae n. sp., and both species show several papillae over the parapodia. However, there is only a single large papilla over the dorsal tip of each parapodium of S. longiparapodium and the blades of compound chaetae are not distally curved as they are in S. anae n. sp. Sphaerodoropsis philippi ( Fauvel, 1911) , although having several papillae on each parapodium, has chaetae that are not distally curved. Finally, although body size is not normally considered as a diagnostic character, it is quite remarkable that specimens of S. anae n. sp., are longer than most of the described species of the genus. They are about 4–5 mm long while the average of the holotypes of the species of the genus is approximately 2 mm.

Etymology. This species is dedicated to Ana Navarro, a very good friend of the senior author, whose affection and company were always invaluable.

Figures

FIGURE 1. Sphaerodoropsis anae n. sp. Live specimens. A: Complete specimens, dorsal view, holotype (female) above, and paratype MNCN 16.01 / 10818 (male) below; B: Anterior end, dorsal view, holotype, la: lateral antennae, ma: median antennae, pro: proventricle; C: Anterior end, dorsal view, paratype MNCN 16.01 / 10818. Scale A: 0.5 mm; B: 0.2 mm; C: 1 mm.

FIGURE 2. Sphaerodoropsis anae n. sp. A: Dorsal view, holotype. B: Anterior end, dorsal view, holotype, la: lateral antenna; C: Anterior end, ventral view, holotype; D: Anterior end, lateral view, paratype MNCN 16.01 / 10818. Scale A: 0.5 mm; B: 97.5 µm; C: 0.2 mm; D: 0.4 mm.

FIGURE 3. Sphaerodoropsis anae n. sp. A: Dorsal surface of midbody chaetigers, holotype; B: Midbody parapodium, anterior view, paratype SAM E 3634; C: Midbody parapodium, posterior view, paratype SAM E 3634; D: Chaetae (under light microscope), midbody chaetiger, paratype MNCN 16.01 / 10818. Scales A – C: 0.2 mm; D: 20 µm.

FIGURE 4. Sphaerodoropsis anae n. sp. Scanning electron micrographs (SEM). Paratype SAM E 3635. A: Anterior end, dorsal view; B: Prostomium and anterior segments, dorsal view; C: Dorsum of midbody chaetigers; D: Midbody parapodia, dorsal view; E: Detail of papillae and chaetal arrangement over midbody parapodia, dorsal view; F: Compound chaeta, anterior chaetiger; G: Compound chaetae, midbody chaetiger; H: Compound chaeta, posterior chaetiger.