Amphictene catharinensis ( Grube, 1870 )

Nogueira, João Miguel De Matos, Ribeiro, William M. G., Carrerette, Orlemir & Hutchings, Pat, 2019, Pectinariidae (Annelida, Terebelliformia) from off southeastern Brazil, southwestern Atlantic, Zootaxa 4571 (4), pp. 489-509 : 492-495

Amphictene catharinensis ( Grube, 1870)

( Figs 1–2 )

Pectinaria (Amphictene) catharinensis . Nilsson 1928: 43 –46, fig. 13; Nonato 1981: 196 –197, figs 210–213.

Material examined. ColBIO IG–182: 1 spec., in relatively poor state of preservation; coll. Ilha Grande, state of Rio de Janeiro, 23 o 01’56”S 43 o 57’01”W, southeastern Brazil .

Comparative material examined. Amphictene auricoma ( Müller, 1776) , NRM104076: coll. Sweden, Bohuslän, Kristineberg, 1 spec. in excellent state of preservation.

Description. Tube not studied, single specimen examined already extracted from its tube, which was not retained. Conical body, 15 mm long, 2.5 mm wide, pale cream in color. Operculum with low marginal lobe all around, with 11 irregularly spaced triangular cirri ( Fig. 1 B–D); 9 pairs of long golden paleae distally tapering to fine tips, slightly curved dorsalwards ( Figs 1 B–E; 2A, B). Cephalic veil completely free from operculum, with few short, distally blunt buccal tentacles at base; distal margin of cephalic veil with 18 slender cirri of two sizes, alternating long and short cirri ( Fig. 1B, C, E, G ). Tentacular cirri of segments 1 and 2 of similar length, both thin and elongate, distally blunt; tentacular cirri of segment 1 dorsally aligned to those of segment 2 ( Fig. 1 A–D, G). Segments 2–6 distinctly raised ventrally, as ventral crests; first crest on segment 2, with 7 pairs of marginal cirri distributed continuously along crest; crest of segment 4 with large triangular, distally rounded lobe medially, and 2 shorter lobes of similar shape at each side ( Fig. 1 A–C, E, G). Two pairs of small pectinate stalked branchiae on segments 3 and 4, each pair consisting of smooth rectangular lamellae longer than wide, first pair larger, inserted dorso-laterally, second pair inserted laterally ( Fig. 1 A–E, G). Notopodia beginning on segment 5 ( Fig. 1B, C ), extending until segment 20; neuropodia beginning on segment 8, extending until segment 20; single achaetous segment at base of scaphe. Notochaetae of two types, those of anterior row with narrow limbation from base, terminating with finely serrated alimbate blade, indented shortly after base of blade ( Fig. 2 C–E); chaetae of posterior row narrowly-winged from base to tip ( Fig. 2C, D, F ). Neurochaetae as pectinate uncini, with 2 longitudinal rows of ~8 teeth of similar size, stout handle directed posteriorly, about as long as crest, and rounded basal peg ( Fig. 2 G–I). Scaphe clearly separated from abdominal segments by constriction at segment 21; scaphe oval in shape, flattened and arched ventrally, lateral margins with 6 pairs of lamellae, anal flaps broader than long, with numerous papillae along edges, and short anal cirrus in-between ( Fig. 1F, H, I ); 13 pairs of brown, dorsolateral scaphal hooks distally pointed and sigmoid, slightly hooked, progressively stouter and longer along torus dorsalwards ( Fig. 2J ).

Variation. According to Nilsson (1928), who re-described the taxon, this species was originally described from a single specimen in poor condition ( Grube 1870), dredged by Fritz Müller from off Ilha de Santa Catarina (formerly Desterro Island) in southern Brazil. According to Birger Neuhaus (personal communication), that specimen is still available at Museum für Naturkunde, Berlin.

Professor Nonato, however, examined for his thesis ( Nonato 1981) 38 specimens of this species, from off the northern coast of São Paulo and southern coast of Rio de Janeiro, southeastern Brazil, slightly north of the type locality. We went through Prof. Nonato’s material, but could find only one specimen of A. catharinensis , which was used for the description above.

The original description ( Grube 1870) and the redescription of the type specimen by Nilsson (1928) compared to the specimen we examined, allowed us to evaluate some of the intraspecific variation of morphological characters, among members of A. catharinensis .

The specimen studied by Grube (1870) and Nilsson (1928) is larger than the one we examined, 31 mm long and 10 mm wide, and has proportionally more paleae (11 on one side, 12 on the other), more cirri on cephalic veil [40 ( Nilsson 1928) or 50 ( Grube 1870)] and on ventral lobe of segment 2 [10 or 16 ( Grube 1870), or 17–18 pairs ( Nilsson 1928)], and more pairs of scaphal hooks (26).

The specimen we examined is much smaller, 15 mm long and 2.5 mm wide, has 9 pairs of paleae, cephalic veil with 18 cirri on distal edge, 7 pairs of cirri on ventral lobe of segment 2, and 13 pairs of scaphal hooks. Interestingly enough, Nonato (1981) did not observe variation in this latter character, as he stated that all his 38 specimens had 13 pairs of scaphal hooks.

Remarks. The most important diagnostic character for members of A. catharinensis is the presence of a large cushion-like mid-ventral lobe with two additional pairs of smaller lobes on the crest of segment 4 ( Fig. 1E ).

This species was described in the 19 th century and has already been reported from the states of Santa Catarina, Paraná, São Paulo and Sergipe ( Amaral et al. 2013) from southern to northeastern Brazil. As said above, the holotype was re-described by Nilsson (1928).

Type locality. Brazilian Economic Exclusive Zone, off the state of Santa Catarina, southern Brazil ( Grube 1870; Nilsson 1928).

Figures

FIGURE 1. Amphictene catharinensis (spec. IG-182), (A). Anterior end, dorsal view; (B–D). Anterior end, right and left lateral and dorsal views, respectively, arrows in (B) and (C) point to first notopodium; (E, G). Anterior end, ventral views, under different magnifications; (F, H, I). Scaphe, ventral, dorsal and right ventro-lateral views, respectively, arrows in (F) and (H) point to anal cirrus, in (I), to anal flaps. Numbers refer to segments, tc1 and tc2 = tentacular cirri of segments 1 and 2, respectively.

FIGURE 2. Amphictene catharinensis (spec. IG-182), (A–B). Paleae; (C, D). Notochaetae from anterior (a) and posterior (b) rows; (E). Notochaeta from anterior row; (F). Notochaeta from posterior row; (G–I). Uncini; (J). Scaphal hooks.