Riseriopsis santosae, Salazar-Vallejo & Zhadan & Rizzo, 2019

Salazar-Vallejo, Sergio I., Zhadan, Anna E. & Rizzo, Alexandra E., 2019, Revision of Fauveliopsidae Hartman, 1971 (Annelida, Sedentaria), Zootaxa 4637 (1), pp. 1-67 : 60-63

Riseriopsis santosae n. sp.

Figures 37 , 38

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Type material: South Atlantic. Campos Basin, off Rio de Janeiro, Brazil. Holotype ( UERJ 6043 ): R/ V Seward Johnson, AMB11 #B5 (20°35’15.33” S, 39°53’45.22” W), 415 m depth, mud, box corer, 18 Jun. 2013 (8.4 mm long, 0.5 mm wide, 26 chaetigers, complete; GP not seen, 28.5 mm long, 0.5 mm wide; 88 chaetigers, anterior region (first 18 chaetigers) in regeneration) . Paratypes – One complete paratype ( UERJ 6953 ): R/ V Seward Johnson, AMB11 #B5 (20°35’15.33” S, 39°53’45.22” W), 415 m depth, mud, box corer, 18 Jun. 2013 (5.2 mm long, 0.2 mm wide, 35 chaetigers) . Six complete paratypes ( UERJ 6077 – 5 specs.; ECOSUR 211 , 1 SEM): R/ V Seward Johnson, AMB5 #B5 (20°35’16.23” S, 39°53’47.1” W), 410 m depth, mud, box corer, 8 Jan. 2012 (5.3–18.5 mm long, 0.25–0.5 mm wide, 37–69 chaetigers; 1 regenerating the anterior region – first 12 chaetigers, and 1 regenerating the posterior region; one incomplete (4.5 mm long, 0.25 mm wide, 28 chaetigers) . Six paratypes complete ( UERJ 6077 ): 5.3–18.5 mm long, 0.25–0.5 mm wide, 37–69 chaetigers, and one incomplete, 4.5 mm long, 0.25 mm wide, 28 chaetigers. One complete paratype ( UERJ 1380 ): Sta. #Hab8 A6, no field data available (7.0 mm long, 0.25 mm wide, 39 chaetigers, prostomium evaginated) .

Etymology. This species is being named to honor our colleague Cinthya S.G. Santos, from the Universidade Federal Fluminense, Brazil, in recognition of her publications on polychaete taxonomy, and especially for her longlasting friendship with one of us (AER). The epithet is a noun in the genitive case.

Diagnosis. Riseriopsis with up to 88 chaetigers. First 4 chaetigers with one capillary and an acicular chaeta per ramus. Median region (5–44) with one notoacicula and neuropodia with one acicula and one capillary; posterior parapodia (last 20 chaetigers) with one acicular and one capillary per ramus. Chaetal formula: anterior chaetigers (1–4): A/2A, median chaetigers (6–20): 1A/1caA, posterior chaetigers (last 20 chaetigers): 1–3c1–3A/1–3A1–3c. Pygidium with long papillae. GP unknown.

Description. Holotype (UERJ 6043) with body subcylindrical, slightly swollen in median region and mainly posteriorly ( Fig. 37A ). Integument anteriorly and posteriorly opaque, medially transparent, with a few transverse delicate striae, papillae scarce, minute ( Fig. 38B ), more abundant in posterior region, especially close to anus. Ventrally with a pronounced median groove ( Fig. 38C ).

Prostomium invaginated, rounded, smooth, without cilia ( Fig. 37B , 38A ). Prostomium and peristomium fused. Mouth ventral, anchor-shaped, with two dots due to chaetal broken bases when seen frontally ( Fig. 37B ). Nuchal organs not seen.

Body separated into three regions by width of chaetiger and chaetation patterns. Anterior and terminal segments shorter than other segments; anterior and posterior chaetigers twice wider than long, median chaetigers as long as, or up to 1.5x longer than wide ( Fig. 38A, G ). Median segments bi- or tri-annulated, chaetal bundles in longer ring ( Fig. 38B, C ). Chaetae disposed laterally on anterior and posterior chaetigers, dorsolaterally along median ones ( Fig. 38D, E ); all low lobes (two specimens regenerating the anterior region with chaetigers narrower than following ones; i.e. 3x wider than long). Chaetae distributed in three patterns: notopodia with cA/Ac in anterior and posterior regions ( Fig. 38A, G ), and A/Ac in median region ( Fig. 38D, E ).

Chaetigers 1–4 not modified; first 4–5 chaetigers with one capillary and an acicular, both slightly falcate and of similar length; bidentate notoaciculars present in smaller specimens. Median segments with aciculars straight, not sigmoid; notoaciculars more robust than neuroaciculars, slightly curved; capillaries thin, tapered. Parapodia 5–8 to 36(–44) with a single acicular in notopodia and one acicular and one capillary in neuropodia (A/Ac) ( Fig. 38 B–E). Following 20 chaetigers with cA/Ac, and last 20 chaetigers with 1–2 aciculars and 1–2 capillaries on notopodia and 2–3 aciculars and 2–3 capillars on neuropodia (1–3c1–1A/1–3A1–3c). Chaetae slightly spinulose ( Fig. 38F ). Last chaetae surpassing pygidial border ( Fig. 34G ).

Substitute chaetae present, mostly along anterior neuropodia. Interramal papillae pedunculate, rounded, between noto- and neuropodia or slightly closer to notopodia than neuropodia, apparently with a terminal pore ( Fig. 38H ). Genital papillae not seen. Gametes not seen.

Pygidium inconspicuous, with a few minute, digitiform or rounded, sessile papillae, close to anus ( Figure 37D ). Free-living.

Variation. Some larger specimens with posterior region bulbous and robust aciculars surpassing pygidial margin, forming a chaetal cage. It is possible that this species uses the posterior region of body to anchor in the sediment; as suggested by the fact that two specimens were regenerating the anterior region. In a small paratype (39 chaetigers; UERJ 1380), probably a juvenile, chaetae are very long and robust, especially on last chaetigers ( Fig. 37C, E ).

Remarks. Riseriopsis santosae n. sp. resembles R. confusa because they are free living, and their posterior chaetigers have hyaline chaetae. They differ by the number of chaetigers, and by chaetal patterns in medial chaetigers.

In R. santosae n. sp. the body has 37–88 chaetigers, and only one acicular per bundle in medial notopodia, whereas R. confusa has 15–31 chaetigers, and one acicular and one capillary per bundle in medial notopodia. In addition, R. santosae n. sp. is a shelf species whereas R. confusa is abyssal.

Distribution. South Atlantic, Campos Basin, off Rio de Janeiro, Brazil, in shelf depths.

Figures

FIGURE 34. Laubieriopsis hartmanae (Levenstein, 1970), non-type specimens (LACM 7331-61). A. Complete, dorsal view, asterisk indicates enlarged area (inset: chaetiger 6 showing paired genital papillae). B. Another specimen, anterior end, right lateral view. C. Chaetiger 3, neurochaetae, posterior view. D. Left genital papilla. E. Right genital papilla. F. Posterior region. G. Same, neurochaetae. H. Another specimen, longitudinally sliced showing oocytes (80–100 µm). Scale bars: A: 1 mm (inset: 250 µm.), B: 110 µm, C: 13 µm, D: 70 µm, E 50 µm, F: 360 µm, G: 35 µm, H: 220 µm.

FIGURE 37. Riseriopsis santosae n. sp., paratype (ECOSUR 211).A. Complete paratype, dorsolateral view. B. Anterior region, frontal view. C. Anterior region, dorsal view. D–E. Posterior region. Scale bars: A: 0.7 mm, B: 0.3 mm, C, D: 0.2 mm, E: 0.1 mm. (UERJ 6077: A, B, D; UERJ 6953: C, E).

FIGURE 38. Riseriopsis santosae n. sp., paratype (ECOSUR 211). A. Complete, oblique lateral view (smaller letters indicate following objects). B. Anterior region, dorsolateral view. C. Anterior chaetigers, oblique lateral view. D. Median chaetigers, latero ventral view. E. Anterior chaetiger, close-up of notochaetae and interramal papilla. F. Last chaetigers before posterior swollen region. G. Second chaetiger, tip of notochaeta. H. Anterior chaetiger, notochaeta and interramal papilla. I. Posterior region, oblique lateral view. J. Posterior chaetiger interramal papilla. Scale bars: A: 0.7 mm, B, C: 140 µm, D, I: 250 µm, E, H: 30 µm, F: 200 µm, G: 8 µm, J: 10 µm.