(®gure 2)
Material examined
Holotype from Ilha dos Alcatrazes, three paratypes from Laje de Santos. Holotype (MHN-BPO 69-0): complete specimen, 1.1 mm long, 0.16 mm wide, with 15 chaetigers. Paratype 1 (MHN-BPO 69-1): complete specimen, 1.7 mm long, 0.17 mm wide, with 20 chaetigers; paratype 2 (MHN-BPO 69-2): complete specimen, 1.4 mm long, 0.19 mm wide, with 15 chaetigers; paratype 3 (MHN-BPO 69-3): incomplete specimen, with 11 chaetigers, 0.23 mm wide.
Description
Body small, short, without colour markings; dorsal and ventral surfaces of body covered by numerous papillae, often hidden by agglutinated debris. Prostomium ovate, partially covered posteriorly by peristomium; four lensed eyes in trapezoidal arrangement. Antennae small with spherical bases and slender, ®liform tips; lateral antennae inserted in front of anterior eyes, median antenna originating between posterior pair of eyes. Palps short, wider than long, fused along their length, leaving a terminal notch, similar in length to prostomium (®gure 2A). Peristomium similar in length to following segments; tentacular cirri small, similar to antennae. Dorsal cirri small, similar to antennae and tentacular cirri, absent on chaetiger 2, becoming somewhat longer on posterior segments (®gure 2A, B). Parapodia conical, provided with several papillae and bearing ®ve to six compound heterogomph chaetae; blades unidentate; in anterior parapodia, blades of compound chaetae with long, very slender spines on the bases of cutting edges (®gure 2C); in posterior parapodia, blades of compound chaetae smooth (®gure 2F); with strong dorsoventral gradation in size, not so marked anteroposteriorly. In anterior parapodia, blades of uppermost chaetae about 22.5 m m long, intermediate, 16 m m, and lower, 12 m m (®gure 2C); in midbody parapodia, upper, 22 m m long, intermediate, 14 m m, and lower, 11 m m; in each posterior parapodia, upper chaetae 20 m m long, median, 12.5 m m, and lower, 9.5 m m (®gure 2F). Solitary dorsal simple chaetae, from chaetiger 1 on holotype, thin, provided with very small spines (®gure 2E); solitary ventral chaetae, on posteriormost parapodia, unidentate, with curved tip, thick and smooth (®gure 2G). Anterior parapodia each with two acicula, one thick, strongly bent at right angle near tip and the other very thin and di cult to see, slightly curved, and with an acuminate tip directed upwards (®gure 2D); each parapodium from midbody with only a solitary strongly bent aciculum (®gure 2H). Pygidium short, semicircular, provided with several papillae and a pair of anal cirri, longer and more elongate than dorsal cirri (®gure 1B). Pharynx extending through about four segments, with a long, triangular tooth located anteriorly; a pair of large pharyngeal glands located at level of chaetiger 1, present in all examined specimens, although sometimes di cult to see. Proventriculum small, short, through about 1.5±2.5 chaetigers, with about 20 rows of muscle cells (®gure 2A).
Etymology This species was named brasiliensis because the type locality is in Brazil.
Discussion
Several species of the genus Sphaerosyllis have a combination of the following characters: densely papillated body, two pairs of eyes, dorsal cirri and antennae small and clavate, and an absence of both: dorsal cirri on second chaetiger and of parapodial glands; however, none of them has such a strong dorsoventral gradation in the size of the blades of the compound chaetae all over the body, as is seen in S. brasiliensis n. sp. The species most similar to S. brasiliensis n. sp. are: S. californiensis Hartman, 1966, S. austriaca Banse, 1959, S. dubiosa Hartmann-SchroÈder, 1962, S. pirifera ClapareÁde, 1868, S. asiatica Buzhinskaja, 1980 and S. piriferopsis Perkins, 1980. In this discussion we do not consider diOEerences such as degree of fusion between prostomium and tentacular segment, and slight diOEerences in pharynx length and number of muscle cell rows of the proventriculum, because we agree with Riser (1991) that these characters depend mostly on how the animals were preserved. Sphaerosyllis californiensis diOEers from S. brasiliensis n. sp. in having: (1) dorsal cirri on chaetiger 2; (2) somewhat longer palps; (3) papillae on the margin of pharynx; (4) proventriculum with only 13±14 rows of muscle cells, against 20 in S. brasiliensis n. sp.; (5) compound chaetae with shorter and proportionally broader blades, especially those of the posteriormost part of the body, with almost no dorsoventral gradation in size, and much more curved; (6) blades of anterior compound chaetae with longer spines along most of the length; and (7) anal cirri similar to dorsal cirri (see Kudenov and Harris, 1995). Sphaerosyllis austriaca is distinguished from S. brasiliensis n. sp. because it has: (1) all three antennae originating on the anterior border of the prostomium; (2) posterior dorsal cirri digitate, with slight diOEerence in thickness between base and tip, and dark pigmented bases; (3) proventriculum with 15 rows of muscle cells; (4) blades of compound chaetae longer (35± 10 m m, on anterior segments, against 22.5± 12 m m in S. brasiliensis n. sp.), with a subterminal spine; and (5) posterior compound chaetae without dorsoventral gradation (see San MartõÂn, 1984a). Sphaerosyllis dubiosa diOEers from S. brasiliensis n. sp. because it has: (1) longer antennae; (2) four yellow transversal rows per segment; and (3) diOEerent morphology of blades of compound chaetae (see Hartmann-SchroÈder, 1962). Sphaerosylli s pirifera is diOEerent because it has: (1) body longer and more robust; (2) antennae, tentacular and dorsal cirri more elongate; (3) posterior dorsal cirri with slight diOEerence of thickness between base and tip; (4) proventriculum extending through more chaetigers (2.5±3 chaetigers, against 1.5±2.5 in S. brasiliensis n. sp.), but with fewer rows of muscle cells (only 14 rows); (5) blades of anterior compound chaetae longer (35± 10 m m), with marked subterminal spine; (6) blades of posterior compound chaetae without dorsoventral gradation in length, shorter, stouter and more curved (see San MartõÂn, 1984a). Sphaerosyllis asiatica has compound chaetae with proportionally shorter blades, provided with longer and coarser spines on the cutting margin (see Buzhinskaja, 1980). Sphaerosylli s piriferopsis is probabl y the most similar species, but it is distinguished by: (1) a pharynx without`yellowish glands’ on chaetiger 1, but with glands surrounding it over its entire length; (2) proventriculum with 13±14 rows of muscle cells; (3) solitary aciculum on every parapodium; (4) blades of anterior compound chaetae slightly shorter (17 m m); (5) blades of posterior compound chaetae about 9.5 m m long, without dorsoventra l gradation, stouter and more strongly hooked than those of S. brasiliensis n. sp., in which length varies from 20 to 10 m m (see Perkins, 1980). Sphaerosyllis hystrix ClapareÁde, 1863 and S. taylori Perkins, 1980 are species similar to S. brasiliensis n. sp., but easily distinguished from it because both have conspicuous parapodial glands containing rods (see San MartõÂn, 1984a).