Pseudostreblosoma Hutchings and Murray, 1984

Nogueira, João Miguel De Matos & Alves, Tarsila Montrezoro, 2006, Two new terebellid polychaetes (Polychaeta: Terebellidae) from the state of São Paulo, southeastern Brazil, Zootaxa 1205, pp. 31-54 : 33-35

Pseudostreblosoma Hutchings and Murray, 1984 , emended

Type­species: Pseudostreblosoma serratum Hutchings and Murray, 1984 by original designation.

Diagnosis

Upper lip short and rounded, lower lip restricted to oral area. Basal part of prostomium bearing eyespots. Lobes on anterior segments sometimes present. Three pairs of branchiae formed by numerous simple filaments. Notopodia from segment 2, extending for a variable number of segments. Each notopodium with two rows of chaetae; chaetae on posterior row distinctly longer than chaetae on anterior row. On anterior notopodia, chaetae on both rows as smooth, limbate capillaries; on posterior notopodia, chaetae on anterior row of notochaetae as serrated capillaries, with elongated and thin blades, and chaetae on posterior row of notochaetae as smooth, limbate capillaries. Neuropodia from segment 5 until near pygidium, uncini in single rows throughout. Uncini high (considered as the distance from top of crest to bottom of base) and elongated (considered as the distance from end of heel to end of prow), heel and prow conspicuous, dorsal button away from the anterior margin.

Remarks

Hutchings and Murray (1984) erected Pseudostreblosoma to accommodate one species which was otherwise similar to Streblosoma Sars, 1872 , but had serrated chaetae and “Amphitritinae­like” (= Terebellinae­like) uncini, with conspicuous heel and prow, and dorsal button situated subdistally. Later, Hutchings and Glasby (1987) emended the diagnosis of the genus, noticing that smooth (= limbate) capillaries were also present, and included a species from the Arabian Gulf, which had originally been described as Streblosoma , P. longum ( Mohammed, 1973) .

The uncini of Pseudostreblosoma , as confirmed in the present paper, are very unusual for a Thelepodinae . Although still being longer than high, as typical of the uncini of the subfamily, they have a short posterior heel, developed prow and dorsal button away from the anterior margin of uncini, all these characters being characteristic of the uncini of Terebellinae , as commented on by Hutchings and Murray (1984). However, in spite of the atypical position of the dorsal button of the uncini of Pseudostreblosoma , its morphology is similar to that of other species of Thelepodinae , a small circle of low bristles projecting for a short extension above the integument ( Fig. 4 B–F), as shown in several other studies which included SEMs of uncini of species of thelepodines ( Hutchings & Glasby 1987, Nogueira & Amaral 2001, Nogueira et al. 2004) instead of a tuft of longer bristles holding the tip of main fang, as typical of the uncini of Terebellinae ( Figs. 8 A–H).

The diagnosis of the genus is now emended again, to allow for the presence of lobes on anterior segments, a feature of the Brazilian species described below. Lobes on anterior segments have been referred to in the literature as “lateral lobes”, or “lateral lappets”, however we consider these terms misleading because such lobes are often situated ventrolaterally or even mid­ventrally, instead of laterally, as in the case of the mid­ventral lobe on segment 1 of the new species of Pseudostreblosoma described in this paper.

The most important features to characterise this genus are the segments on which the noto­ and neuropodia begin, and the morphology of notochaetae and neurochaetal uncini.

Figures

FIGURE 4. Pseudostreblosoma brevitentaculatum sp. nov .. A: posterior thoracic neuropodium; B: uncini, segment 5; C – F: posterior thoracic uncini; arrows point to dorsal buttons. Scale bars: A: 70 µm; B, C, F: 6 µm; D: 4 µm; E: 5 µm.

FIGURE 8. Phisidia rubra sp. nov. A: uncini, segment 5; B: uncini, segment 10; C – D: uncini, segment 13; E: uncini, segment 21 (first segment after the ending of the uncini arranged in double rows); F: detail of the uncini of segment 21; G: posterior abdominal uncini; H: detail of posterior abdominal uncini. Scale bars: A, E, G – H: 2 µm; B: 3 µm; C – D: 4 µm; F: 1.5 µm.