Grubeosyllis breviarticulata, Nogueira, 2001

Nogueira, J. M. De M., 2001, Description of ® ve new species of Exogoninae Rioja, 1925 (Polychaeta: Syllidae) associated with the stony coral Mussismilia hispida (Verrill, 1868) in SaÄo Paulo State, Brazil, Journal of Natural History 35, pp. 1773-1794 : 1786-1788

Grubeosyllis breviarticulata n. sp.

(®gure 4)

Material examined

Holotype and three paratypes from Ilha dos Alcatrazes . Holotype (MHN-BPO 67-0): complete specimen in good condition, about 1.63 mm long, 0.24 mm wide, with 24 chaetigers. Paratype 1 (MHN-BPO 67-1): complete specimen, 1.01 mm long, 0.18 mm wide, with 19 chaetigers; paratype 2 (MHN-BPO 67-2): complete specimen, 0.93 mm long, 0,12 mm wide, with 15 chaetigers; paratype 3 (MHN-BPO 67-3): complete specimen, 1.9 mm long, 0.2 mm wide, with 26 chaetigers.

Description

Body small, slender, without colour markings. Prostomium oval to rectangular, wider than long, not covered by peristomium (®gure 4A). Four small, lensed eyes in trapezoidal arrangement; anterior pair larger than the posterior pair; two anterior ocular eyespots. Antennae long, with broad bases and acuminate tips; lateral antennae originating between anterior eyes and eyespots, slightly shorter than prostomium and palps together; median antenna originating between posterior pair of eyes, similar in length to prostomium and palps together. Palps long, more than twice the length of the prostomium, broad at their bases, triangular, separated in the distal half and fused in the basal half by a dorsal membrane. Peristomium dorsally reduced, bearing two pairs of tentacular cirri, similar in shape to antennae; dorsal pair somewhat longer than ventral pair, and similar in length to lateral antennae. Dorsal cirri long and slender; dorsal cirri of chaetiger 1 much longer than those of following chaetigers (®gure 4A). Ventral cirri digitiform. Parapodia each with about four compound chaetae, heterogomph, with very short blades, strongly bidentate and without marked gradation in length neither dorsoventrally nor anterior-posteriorly; on parapodia in anterior part of the body, blades of dorsalmost falcigers about 11 m m long, median ones 9.5 m m, and ventralmost 8 m m; from midbody, this diOEerence in size is even less, all blades around 10 m m; all along the body, cutting edges of blades bearing short spines (®gure 4B, E). Single dorsal simple chaeta, long, thin, bidentate, provided with small spines on concave side, present from chaetiger 13, in holotype, and from chaetiger 6 in the paratype 1 (®gure 4D). Solitary ventral simple chaeta seen only on posteriormost three chaetigers of paratype 1, thinner, smaller and more curved than dorsal simple chaeta, slightly bidentate. Anterior parapodia each with two acicula, one very slender with a subdistal expansion and pointed tip, and the other much slender, straight, with a slightly curved tip (®gure 4C); only the curved aciculum persists in the posterior parapodia (®gure 4F), thicker than those of the anterior parapodia. Pygidium small with two long and slender anal cirri, and a short, digitate papilla (®gure 4G). Pharynx extending through about four segments, with a long, rhomboidal tooth on anterior margin. Proventriculum wide, through four segments, with about 23 rows of muscle cells (®gure 4A).

Etymology

The name breviarticulata refers to the small size of the blades of the compound chaetae.

Discussion

The most characteristic features of Grubeosyllis breviarticulata n. sp. are long dorsal cirri and short-bladed falcigers. Only few species of this genus share similar characteristics. Grubeosyllis balani (Hartmann-SchroÈder, 1960) diOEers because: (1) the median antenna is inserted more anteriorly on the prostomium, between the anterior pair of eyes; (2) the dorsal cirri of chaetiger 1 are about the same size as the following cirri and all of them are shorter and have broader bases; and (3) the blades of the compound chaetae have a larger gap between distal and proximal teeth and are even shorter than those of G. breviarticulata n. sp., about 4±5.5 m m long on anterior parapodia, and 3±4 m m on posterior ones (see AloÂs et al., 1983). Grubeosyllis brevipharyngea ( Banse, 1972) is easily distinguished from G. breviarticulata n. sp. because in this species: (1) the palps are totally fused; (2) the peristomium is not dorsally reduced; (3) the dorsal cirri of chaetiger 1 are similar in length to the following cirri; (4) the acicula are distally blunt; (5) each parapodium has seven to nine compound chaetae; (6) there is a strong gradation in size of the chaetae and only the ventralmost are similar to those of G. breviarticulata n. sp.; (7) the dorsal simple chaeta is present from the anterior chaetigers; and (8) the pharynx is shorter, extending only through three chaetigers, against four in G. breviarticulata n. sp. Finally, Grubeosyllis yraidae San MartõÂn, 1984a is separated from G. breviarticulata n. sp. because the former species has: (1) the palps almost completely fused; (2) the peristomium not reduced; (3) the acicula with very short tip; (4) the blades of superior falcigers with long spines; (5) the blades of inferior falcigers with the proximal tooth very reduced, resembling a spine; (6) the pharynx shorter, only extending through two or three segments; and (7) the pharyngeal tooth placed away from the anterior margin of the pharynx.