Scyphoproctus robustus, Silva & Amaral, 2019

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 : 114-118

Scyphoproctus robustus sp. nov.

( Figures 11 ̄13)

Type series. Holotype ( ZUEC POL 20522): state of São Paulo, São Sebastião, São Sebastião Channel (23°44'54"S, 45°24'34"W): coll. 0 4 Oct 1995; soft-bottom; intertidal; Stn. 445A; 1 spec . Paratypes: state of São Paulo, São Sebastião, São Francisco Beach (23°44'54"S, 45°24'34"W): paratypes 1̄3 ( ZUEC POL 20510): coll. 26 Jun 2013; sandy beach; intertidal; Stn. 45; 3 specs . Paratypes 4̄10 ( ZUEC POL 20513): coll. 23 Jun 2013; sandy beach; intertidal; Stn. 47; 7 specs. State of São Paulo, São Sebastião, Araçá Bay (23°48'S, 45°24'W): paratype 11 ( ZUEC POL 20506): coll. 15 Jun 2011; soft-bottom; intertidal; Stn. 22(1)A; 1 spec. State of Paraíba, Cabo Branco Beach (7°08'S, 34°47'W): paratypes 12 and 13 ( ZUEC POL 20519): coll. 0 1 Feb 2010; in rhodoliths; intertidal; 2 specs .

Additional material examined. State of São Paulo, São Sebastião, Engenho D’Água Beach (23°47'49"S, 45°21'56"W). (ZUEC POL 1779 ): coll. 25 Nov 1996; soft-bottom; intertidal; Stn. 2807B; 1 spec. (ZUEC POL 1854 ): coll. 20 May 1996; soft-bottom; intertidal; Stn. 1883B; 1 spec. (ZUEC POL 1855 ): coll. 20 May 1996; softbottom; intertidal; Stn. 1881A; 2 specs. (ZUEC POL 1935 ): coll. 0 8 Apr 1997; soft-bottom; intertidal; Stn. 3199B; 2 specs. (ZUEC POL 1936 ): coll. 0 8 Apr 1996; soft-bottom; intertidal; Stn. 3196A; 6 specs. (ZUEC POL 1954 ): coll. 0 2 Jul 1996; soft-bottom; intertidal; Stn. 3199B; 1 spec. State of São Paulo, São Sebastião, São Francisco Beach (23°44'54"S, 45°24'34"W). (ZUEC POL 20511): coll. 26 Jun 2013; sandy beach; intertidal; Stn. 72; 1 spec. (ZUEC POL 20512): coll. 26 Jun 2013; sandy beach; intertidal; Stn. 71; 9 specs. (ZUEC POL 20514): coll. 11 Apr 2013; sandy beach; intertidal; Stn. 20P; 15 specs. (ZUEC POL 20515): coll. 11 Apr 2013; Stn. 5G; 2 specs. (ZUEC POL 20516): coll. 26 Jun 2013; sandy beach; intertidal; Stn. 43; 7 specs. (ZUEC POL 20521): coll. 0 4 Dec 1995; sandy beach; intertidal; Stn. 445A; 3 specs. State of São Paulo, São Sebastião, Araçá Bay (23°48'S, 45°24'W). (ZUEC POL 20504): coll. 14 Jun 2011; soft-bottom; intertidal; Stn. 10(3)B; 1 spec. (ZUEC POL 20505): coll. 10 Oct 2013; shallow sublittoral; 8.6 m deep; Stn. 29(1)Mc; 1 spec. State of São Paulo, Caraguatatuba, Camaroeiro Beach (23°37'38"S, 45°23'50"W). (ZUEC POL 20520): coll. 25 May 2006; in mussel bed; intertidal; Stn. 16A; 1 spec. State of São Paulo, Caraguatatuba, Enseada Beach (23°43'40"S, 45°25'10"W). (ZUEC POL 20517): coll. 11 Apr 2013; soft-bottom; intertidal; Stn. 47P; 6 specs. State of Espírito Santo, Espírito Santo Basin—continental shelf . (ZUEC POL 20507): (18°40'55,3''S, 38°55'41,48"W); coll. 17 Jan 2012; sublittoral; 44m deep; Stn. AMB 7/G03; 2 specs. (ZUEC POL 20508): (21°2'45,81''S, 40°32'29,21"W); coll. 22 Jan 2012; sublittoral; 20m deep; Stn. AMB 7/A01; 1 spec. (ZUEC POL 20509): (18°40'55,3''S, 38°55'41,48"W); coll. 0 2 Dec 2011; sublittoral; 34m deep; Stn. AMB 7/E02; 1 spec. State of Paraíba, Cabo Branco Beach (7°08'S, 34°47'W). (ZUEC POL 20518): coll. 0 8 Feb 2009; in rhodoliths; intertidal; 5 specs.

Description. Complete holotype 9.5 mm long, 0.8 mm wide for 53 chaetigers. Incomplete specimens 0.30–1.5 mm wide for 32–66 chaetigers. Body robust; similar width between thorax and abdomen; slightly narrowing toward pygidium. Whitish color in alcohol.

Prostomium robust, 2x longer than wide, rounded on anterior end, usually withdrawn into peristomium ( Figs 11A ; 12A ; 13A ); nuchal organs not observed; eyespots as a pair of oval postero-lateral densely pigmented areas. Proboscis globular-shaped, with several large papillae ( Figs 11B ; 12C ). Peristomium 1.5x longer than thoracic segments ( Figs 11A ; 12A ; 13A ). Complete inter-segmental groove between peristomium and achaetous segment ( Figs 11A ; 12A ). Peristomium and achaetous segment weakly rugose ( Fig. 11A ).

Thorax with 12 segments, including peristomium, one additional achaetous segment and 10 chaetigers ( Figs 11A ; 12A ; 13A ). Bilimbate capillaries in notopodia and neuropodia of chaetigers 1–10. Thorax with chaetigers distinctly biannulate, more evident after chaetigers 5–6 ( Figs 12A ; 13A ); moderate depth of inter-segmental grooves between chaetigers. First chaetiger biramous. Notopodial lobes inserted dorso-laterally and neuropodial lobes laterally. Lateral organs present since the achaetous segment and throughout thorax, between noto- and neuropodia, closer to notopodia ( Figs 11A ; 12D ; 13A ). Transition between thorax and abdomen inconspicuous, marked only by change of chaetae and methyl green staining pattern ( Figs 11A ; 12A ̄B).

Abdominal chaetigers without capillaries. Abdominal noto- and neuropodia with moderately developed tori pads separated by same distance throughout ( Fig. 12E, H ). First notopodial chaetigers with 9 hooks per fascicle, reducing in number toward posterior end; first neuropodial chaetigers with 15 hooks per fascicle, increasing in number toward mid-abdomen, and then reducing in number toward posterior end. Notopodial hooks (with SEM) with a narrow main fang, finger-shaped, right angle with shaft, surmounted by 12 teeth arranged in four rows (3–3–

3–3); large, thin and smooth hood ( Fig. 13B ). Neuropodial hooks (with SEM) with a large and robust main fang, triangular, right angle with shaft, surmounted by 22 teeth arranged in three rows (4–6–12); large and thin hood with a serrate margin ( Fig. 13C ).

Modified pre-pygidial segments absent, all preceding segments with noto- and neuropodial hooks. Anal plaque flat, oval shaped, nine sets of acicular spines protruding from plaque margin (8,5,3,3,2,2,2,2,1, each side); small anus near the inferior margin, not reaching plaque margin; two short thin fused cirri (one-third plaque length), without median membrane ( Figs 11C ̄D; 12F̄G).

Variation. Paratypes with 12–14 segments, including the peristomium, one additional achaetous segment and 10–12 chaetigers. Adult specimens with bilimbate capillaries in noto- and neuropodia of chaetigers 1–10/12. Number of hooks of the first abdominal lobe size dependent, notopodium ranging from 3 to 20 and neuropodium from 6 to 20 hooks. set of Acicular spines from the plaque margin size dependent, smaller specimens with 3,3,2,2,1,1,1,1,1 spines each side.

Methyl green staining pattern. Thoracic segments staining uniformly darker than the abdomen; final thoracic chaetigers with a fine dark band on the inter- and intra-segmental grooves; abdominal chaetigers staining uniformly light green ( Fig. 12B ).

Remarks. Scyphoproctus robustus sp. nov. belongs to a group of species with the set of acicular spines positioned marginally on the plaque, either protruding from the edge or embedded, which includes Scyphoproctus djiboutiensis , S. fasciculatus , S. glabrus , S. guadalupensis , S. lumenalis , S. oculatus , S. ornatus , S. platyproctus and S. variabilis .

Scyphoproctus glabrus and S. guadalupensis are different from S. robustus sp. nov. in having two pre-pygidial segments with notopodia bearing acicular spines, while Scyphoproctus robustus sp. nov. has hooded hooks on both noto- and neuropodia, therefore lacking modified pre-pygidial segments. The differences between Scyphoproctus robustus sp. nov. and S. glabrus are also related to the number of sets of acicular spines of the anal plaque, which is nine in the former and fourteen in the latter, and the features of the abdominal hooded hooks. Scyphoproctus glabrus has similar noto- and neuropodial hooded hooks, with 10–15 teeth above main fang arranged in three rows, while Scyphoproctus robustus sp. nov. has notopodial hooded hooks with 12 teeth arranged in four rows and neuropodial hooded hooks with 22 teeth arranged in three rows.

Scyphoproctus fasciculatus and S. ornatus differ from Scyphoproctus robustus sp. nov. by the number of sets of acicular spines of the anal plaque, number of acicular spines, length of anus and features of the cirri. Scyphoproctus fasciculatus presents an anal plaque with three sets of acicular spines with two spines each, anus with moderate length and cirri longer than the plaque with a median membrane. Scyphoproctus ornatus presents an anal plaque with 10 sets of acicular spines with several spines each (16,11,6,4,3,4,3,1,1,1) and large anus.

Scyphoproctus oculatus , S. platyproctus and S. variabilis differ from Scyphoproctus robustus sp. nov. by the presence of pre-pygidial segments with acicular spines, different from the latter species, which has none. Scyphoproctus oculatus has 2–6, S. platyproctus has 4–7 and S. variabilis has two. Although S. lumenalis also lacks pre-pygidial segments with acicular spines, it differs from Scyphoproctus robustus sp. nov. because the spines of the plaque are embedded and by the presence of two long cirri (longer than plaque length) with a median membrane, in contrast to Scyphoproctus robustus sp. nov., which has protruding spines, and short cirri without a median membrane.

Although Scyphoproctus djiboutiensis also has a thoracic region with 14 segments (12 chaetigers) and short cirri without a median membrane, the species differs from Scyphoproctus robustus sp. nov. by the number of sets of acicular spines, which is 11, lack of eyespots, proboscis without papillae, smooth thorax, absence of lateral organs and similar noto- and neuropodial hooded hooks.

Etymology. Latin word that means “strong”. This species was named after its width, since it is one of the largest species of the genus.

Habitat. From intertidal to sublittoral regions (0–44m); in soft-bottom, mussel beds and rhodoliths.

Type locality. São Francisco Beach , São Paulo , Brazil, 23°44'54"S, 45°24'34"W (South Atlantic Ocean). Distribution. South Atlantic Ocean : Brazil (states of Espírito Santo, Paraíba and São Paulo) .

Figures

FIGURE 11. Scyphoproctus robustus sp. nov. (A) Thoracic region, lateral view; (B) Anterior end, lateral view; (C) Anal plaque, frontal view; (D) Anal plaque, lateral view. Scale bars: A, 1 mm; B, 0.5 mm; C, D, 0.1 mm.

FIGURE 12. Scyphoproctus robustus sp. nov. (A) Thoracic region, lateral view; (B) methyl green staining pattern; (C) Anterior end, lateral view; (D) lateral organs; Anal plaque, frontal view; (E) Abdominal region; dorsal view; (F) Abdominal region; ventral view; (G) Neuropodial hooded hooks, lateral view; (H) Anal plaque, frontal view; (I) Anal plaque, lateral view. A: abdomen. Scale bars: A, B, E, 0.2 mm; F, 0.5 mm; C, D, H, I, 0.1 mm; G, 10 µm.

FIGURE 13. Scyphoproctus robustus sp. nov., SEM. (A) Thoracic region, lateral view; (B) Notopodial hooded hooks, frontal view; (C) Neuropodial hooded hooks, frontal view. Scale bars: A, 0.5 mm; B, 5 µm; C, 2 µm.