Scyphoproctus oculatus Reish, 1959 Amended

Silva, Camila Fernanda Da & Amaral, Antonia Cecilia Zacagnini, 2019, Scyphoproctus Gravier, 1904 (Annelida, Capitellidae): description of three new species and relocation of Heteromastides Augener, 1914 in Scyphoproctus, Zootaxa 4560 (1), pp. 95-120 : 101-103

Scyphoproctus oculatus Reish, 1959 Amended

( Figures 2 ̄3)

Scyphoproctus oculatus Reish, 1959: 78 ̅80; figs. 1̅6.

Material examined. Scyphoproctus oculatus Reish, 1959 , holotype LACM-AHF POLY 481—(33°36'59'' N, 117°54'18'' W): 26.3m deep, Orange County, Newport, California, USA, 1 spec.

Description. Holotype 20 mm long, 1.0 mm wide for 97 chaetigers. Body thin; thorax same width as anterior abdomen ( Fig. 3A ). Yellowish color in alcohol.

Prostomium broadly rounded, in demilune shape, base 1.5x wider than long ( Fig. 2A ); nuchal organs not observed; eyespots as a pair of elliptical-shaped areas on each side ( Fig. 2A ). Proboscis globular-shaped, papillae not observed. Peristomium 1.5x longer than achaetous segment ( Figs 2A ; 3A ). Incomplete inter-segmental groove between peristomium and achaetous segment ( Figs 2A ; 3A ).

Thorax with 13 segments, including the peristomium, one additional achaetous segment, and 11 chaetigers. Bilimbate capillaries in notopodia and neuropodia of chaetigers 1–11. Thorax smooth with chaetigers strongly biannulate; moderate depth of inter-segmental grooves between chaetigers. First chaetiger biramous. Parapodial lobes well-separated; notopodia inserted dorso-laterally and neuropodia laterally. Lateral organs present from the achaetous segment. Transition between thorax and abdomen conspicuous, marked mainly by chaetal change and appearance of parapodial lobes ( Fig. 3A ).

Abdominal chaetigers without capillaries. Abdominal notopodia and neuropodia with well-developed tori pads. First notopodial lobes together ( Fig. 3B ), distance between lobes increasing along abdomen; neuropodial lobes separated, with nearly same distance throughout abdomen. Notopodial hooks (light microscopy) with large and triangular main fang, surmounted by approximately 10 teeth arranged in three rows in lateral view.

Four pre-pygidial segments with neuropodial hooks and notopodial spines—3, 3, 2, 2 spines per notopodial lobe, greater number of spines near anal plaque ( Fig. 2C ). Anal plaque well-developed, circle-shaped, with five sets of spines protruding from plaque margin (5,3,2,2,1, each side) ( Fig. 2 B–C). Median-sized anal aperture on inferior third of plaque, beginning as a slit from base of anal cirri ( Fig. 2B ). Two short and robust cirri, 1.5x longer than wide and base 3x wider than distal end; without a median membrane ( Figs 2 B–C; 3C–D).

Remarks. According to drawings and original description, Scyphoproctus oculatus lacks the achaetous segment. All Scyphoproctus species present an achaetous segment, posterior to peristomium, and the intersegmental groove between peristomium and achaetous segment may be complete or incomplete; when it is incomplete, the delimitation between both segments may not be conspicuous. Re-examination of the type material made possible to confirm that S. oculatus presents an achaetous segment with an incomplete inter-segmental groove, unnoticed in the original description.

The original description presents a variation on the number of acicular spines in the anal plaque; however, together with the holotype there were some specimens that were not S. oculatus and some small posterior fragments; in this way the re-description was made based only on the holotype (that it was complete) in order to avoid any possible mistake.

Figures

FIGURE 2. Scyphoproctus oculatus. (A) Anterior end, dorsal view; (B) Anal plaque, frontal view. (C) Posterior end, lateral view. Scale bars: A, B, C, 0.5 mm.

FIGURE 3. Scyphoproctus oculatus. (A) Anterior end, lateral view; (B) Abdominal region, dorsal view; (C) Posterior end; lateral view; (D) Anal plaque, frontal view. Scale bars: A, 1 mm; B, C, D, 0.5 mm.