Nereis saramagoi, Bergamo, Carrerette, Shimabukuro, Santos & Sumida, 2023

Bergamo 1, Gilberto, Carrerette 1, Orlemir, Shimabukuro 1, Mauricio, Santos, Cinthya S. G. & Sumida 1, Paulo Y. G., 2024, Revealing a new eyeless Nereis (Nereididae: Annelida) clade from deep-sea organic falls, Zoological Journal of the Linnean Society 201 (201), pp. 1-31 : 20-24

Nereis saramagoi sp.nov.

( Figs 11–13 )

urn:lsid:zoobank.org:act:EF3806B8-ABB7-4A54-ACE9-094870C12A79

Type series: Holotype and paratypes 1–19 coll. 18 May 2017, continental margin off São Paulo state, Santos basin, Brazil, 26°36ʹ13,44″S, 46°09ʹ9.29″W, 550 m depth; holotype ( MZUSP5334 ), complete, 60 cht, 19.3 mm long, 1.7 mm wide; paratype 1 (ColBIO-DS 00189), incomplete, 33 cht, 28.4 mm long, 3.5 mm wide; paratype 2 (MZUSP5335), incomplete, 29 cht, 14.5 mm long, 2 mm wide; paratype 3 (MZUSP5336), incomplete, 50 cht, 17.8 mm long, 1.8 mm wide; paratype 4 (MZUSP5337), incomplete, 13 cht, 4.6 mm long, 1.4 mm wide; paratype 5 (ColBIO-DS 00190), incomplete, 28 cht, 7.8 mm long, 0.8 mm wide; paratype 6 (ColBIO-DS 00191), incomplete, 30 cht, 9.5 mm long, 0.9 mm wide; paratype 7 (ColBIO-DS 00192), incomplete, 29 cht, 10.1 mm long, 0.8 mm wide; paratype 8 (MZUSP5338), incomplete, 26 cht, 17.7 mm long, 2.6 mm wide; paratype 9 (MZUSP5339), incomplete, 34 cht, 20.7 mm long, 2.6 mm wide; paratype 10 (ColBIO-DS 00193), incomplete, 32 cht, 12 mm long, 1.2 mm wide; paratype 11 (ColBIO-DS 00194), complete, 27 cht, 4.4 mm long, 0.5 mm wide; paratype 12 (ColBIO-DS 00195), incomplete, 8 cht, 8 mm long, 3.8 mm wide; paratype 13 (ColBIO-DS 00196), incomplete, 31 cht, 15.1 mm long, 1.5 mm wide; paratype 14 (MZUSP5340), complete, but fractioned, 53 cht, 23.3 mm long, 1.8 mm wide; paratype 15 (MZUSP5341), incomplete, 35 cht, 26.2 mm long, 3 mm wide; paratype 16 (ColBIO-DS 00197), complete, 67 cht, 29.1 mm long, 2.2 mm wide; paratype 17 (ColBIO-DS 00198), incomplete, 31 cht, 12.1 mm long, 1.3 mm wide; paratype 18 (MZUSP5342), mounted on SEM stub, incomplete, 19 cht, 4.1 mm long, 0.4 mm wide; paratype 19 (MZUSP5343), mounted on SEM stub, complete, 35 cht, 5.1 mm long, 0.5 mm wide .

Description: Holotype atokous, cylindrical body, slightly flattened dorsoventrally from mid-body.

Prostomium slightly wider than long, with one pair of frontal antennae and one pair of biarticulated palps ( Figs 11A–C , 13B, C ). Antennae subulate, slightly longer than palps and curved laterally ( Fig. 11A–C ). Palpostyles sub-conical, palpophores subcylindrical, flattened dorsoventrally ( Fig. 11B, D ). Eyes absent ( Fig. 11A, D, H ). Peristomium about the same size as prostomium and one-quarter longer than chaetiger 1 ( Figs 11A, H , 13A ), with four pairs of tentacular cirri; posterodorsal pair reaching anterior region of chaetiger 1 ( Fig. 11F ).

Jaws dark brownish, pointed, each with five to seven teeth. Pharynx with numerous black, small and easily detachable conical paragnaths ( Fig. 13H, I ) on both rings, with the following arrangement: area I = 5–7 in a vertical line; area II = 20–30 on each side in two or three transversal rows; area III = ~ 47 in three or four rows forming an ellipse; area IV = ~37 on each side, forming a triangle; area V = 0; area VI = 4–7 on each side, forming circles; area VII–VIII = ~200, in several rows, more concentrated in the grooves; some specimens present a superior row with five or six larger paragnaths ( Fig. 11D, E ).

First two parapodia uniramous ( Fig. 12A ) and all subsequent parapodia biramous ( Fig. 12B, C , 13E ). Uniramous parapodia with dorsal cirri slightly longer than dorsal ligule. Ventral ligule slightly longer and stouter than dorsal ligule. Both ligules twice the length of acicular lobe. Ventral cirri one-quarter shorter than ventral ligule.

Biramous parapodia with dorsal cirri slender and longer than notopodial ligule, ~1.5× longer on anterior parapodia and 1.2× longer on posterior parapodia. Notopodial ligule slightly shorter than notopodial lobe on anterior parapodia ( Fig. 12B ) and slightly longer than notopodial lobe on posterior parapodia ( Fig. 12C ); both sub-conical. Notopodial lobes longer and thinner than neuropodial lobes, ~1.2× longer on anterior parapodia and 1.6× longer on posterior parapodia; neuropodial lobes sub-conical, becoming more rounded and shorter towards posterior parapodia ( Fig. 12C ). Neuropodial ligule sub-conical, as long as neuropodial lobe on anterior parapodia ( Fig. 12B ) and gradually longer on posterior parapodia, with a maximum of 1.4× longer than neuropodial lobes ( Fig. 12C ). Neuropodial prechaetal lobes rounded and one-quarter shorter than postchaetal lobes; neuropodial postchaetal lobes tapering in anterior parapodia and bilobed in posterior parapodia ( Figs 12A–C , 13E ). Ventral cirri digitiform and slender, slightly shorter than neuropodial ligule on anterior parapodia ( Fig. 12B ) and one-sixth shorter than neuropodial ligule on posterior parapodia ( Fig. 12C ).

Uniramous parapodia with supra-acicular chaetae ( Fig. 12D ) homogomph spinigers ( Figs 12F , 13F ) and sub-acicular chaetae ( Fig. 12D ) homogomph and heterogomph spinigers ( Figs 12G , 13G ), and heterogomph falcigers. Biramous parapodia with notochaetae ( Fig. 12E ) homogomph spinigers in all parapodia and homogomph falcigers ( Figs 12I , 13J ) in posterior parapodia, maximum of 2 per parapodium. Homogomph falcigers ( Fig. 12I ) with blades easily detached, serrated along all their length, with five to seven teeth, except at the rounded tips, serrations of short size.

Supracicular neurochaetae ( Fig. 12H ) homogomph spinigers and heterogomph falcigers ( Figs 12J , 13D ). Heterogomph falcigers, maximum of five per parapodium. Sub-acicular neurochaetae ( Fig. 12H ) homogomph and heterogomph spinigers, and heterogomph falcigers. Blades of homogomph spinigers with visible serration, equally present along their length and at least twice the length of heterogomph ones. Heterogomph falcigers with tips slightly curved.

Pygidium with one pair of pygidial cirri, as long as the last 15–20 chaetigers ( Fig. 11G ).

Variation: Specimens were found in both whale bones and wood blocks. After fixation, specimens from bones turned light cream in colour, whereas specimens found in wood turned dark brown. This variation is probably related to the transfer of wood pigmentation to the specimens via ethanol, which becomes an opaque dark brown liquid in preserved samples. Antennae of larger specimens are more laterally curved. Paratype 8 presents a translucent cuticle, probably as an effect of fixation, and this artefact allowed the observation of two pairs of small, black, rounded eyes ( Fig. 11C ), totally covered by cuticle; therefore, all specimens might present vestigial eyes covered by a thick cuticle. Specimens present variations in the uniramous parapodia, with dorsal cirri as long as dorsal ligule, and variations in neuropodial ligule length; in general, most of the specimens have the same length of neuropodial ligule and lobe in anterior parapodia, but some individuals have neuropodial ligules, in the anterior region, longer or slightly shorter (up to one-sixth) than the neuropodial lobe. Notwithstanding, the neuropodial ligule always becomes gradually longer towards posterior parapodia.

Remarks: Nereis saramagoi is described from eyeless specimens inhabiting whale bones and wood blocks. Similar to the other species from organic falls described in the present study, Nereis saramagoi differs from most of the shallow-water Nereis species by the absence of eyes and by the presence of small and fragile paragnaths, easily detachable from the pharynx. Nereis saramagoi differs from the other deep-sea Nereis species by a combination of morphological features and by the paragnath formula ( Tables 3 and 4 ).

Nereis saramagoi is more similar to Nereis eugeniae , Nereis tricirrata , Nereis anoculepitoka and Nereis mariellae . However, it differs from the species Nereis eugeniae in the habitat (organic falls for Nereis saramagoi and cobbles and shells for Nereis eugeniae ), the depth (1508 m for Nereis saramagoi and 156 m for Nereis eugeniae ) and the size of specimens (19 mm for Nereis saramagoi and 74 mm for Nereis eugeniae ) ( Table 3 ). The number of paragnaths in each area of the pharynx also differs between both species ( Table 4 ). Nereis saramagoi differs from Nereis tricirrata in the habitat (organic falls for Nereis saramagoi and soft sediment for Nereis tricirrata ), in depth (550 m for Nereis saramagoi and 1766 m for Nereis tricirrata ) and in the blade of the homogomph falcigers, with 8–10 blunt teeth for Nereis saramagoi and several coarse teeth for Nereis tricirrata ; the new species differs especially in paragnath numbers and distribution ( Table 4 ), with Nereis tricirrata , for example, lacking paragnaths in areas I, III and V and presenting two paragnaths in areas VII and VIII, whereas Nereis saramagoi lacks paragnaths only in area V and presents 200 paragnaths in areas VII and VIII ( Table 4 ).

Nereis saramagoi differs from Nereis mariellae by the positioning of palps, more ventrally pointed in the latter; by the length of posterodorsal tentacular cirri, reaching chaetiger 3 in Nereis mariellae , whereas in Nereis saramagoi they reach chaetiger 1; by the presence of dark spots on several body parts, including the parapodia, peristomium and dorsal region of chaetigers in Nereis mariellae , spots not present in Nereis saramagoi ; and mainly by the parapodial characteristics, because Nereis mariellae presents the notopodial ligule pyriform with a globular base and almost subdivided, whereas Nereis saramagoi presents a subconical notopodial ligule without division. Moreover, the neuropodial ligule is always shorter than the neuropodial lobe in Nereis mariellae , whereas it is as long or longer than the neuropodial lobe in Nereis saramagoi . Heterogomph falcigers are thinner and longer in Nereis mariellae compared with Nereis saramagoi , two-fifths longer and three-fifths wider on average. The number and position of paragnaths of both species are very different, as shown in Table 4 .

Nereis saramagoi is morphologically more similar to Nereis anoculepitoka (also following the molecular results), with similar paragnath formula ( Table 4 ). Neverthless, Nereis saramagoi differs from Nereis anoculepitoka in the length of the posterodorsal tentacular cirri, which reaches the anterior region of chaetiger 1 in Nereis saramagoi , whereas in Nereis anoculepitoka it reaches the posterior part of chaetiger 5. The length of the peristomium is twice the length of chaetiger 1 in Nereis anoculepitoka , but only 1.25× longer in Nereis saramagoi . The pygidial cirri are also distinct between both species, reaching last 15–20 chaetigers in Nereis saramagoi and reaching the last eight chaetigers in Nereis anoculepitoka . Moreover, Nereis anoculepitoka has dark spots on the parapodia, which are absent in Nereis saramagoi , and the neuropodial ligules are slightly longer in Nereis saramagoi .

Etymology: The species name is a tribute to the Portuguese writer José Saramago, who wrote the novel ‘Ensaio sobre a cegueira’ (‘Blindness’ in English). The absence of eyes and consequent blindness of the members of the species is likened to the blindness of the characters in the novel.

Occurrence: Reported only from whale bones and wood blocks implanted in the upper continental slope at 550 m depth, in the Santos Basin, Southwest Atlantic.

Figures

Figure 11. Nereis saramagoi. A, B, holotype. C, paratype 8. D, E, G, paratype 14. F, paratype 10. H, paratype 13. A, anterior end, dorsal view. B, anterior end, ventral view.C, anterior end, dorsal view; arrow points to vestigial eyes covered by cuticle. D, pharynx dorsal view.E, pharynx, ventral view. F, anterior end, lateral view; arrow points to posterodorsal tentacular cirri. G, posterior end, pygidial cirri. H, anterior and median region of specimen.Scale bars: 0.5 mm in A, B; 1 mm in C–E, G; 2 mm in F; 5 mm in H.

Figure 12. Nereis saramagoi, paratype 1 parapodia under light microscope. A, parapodium, chaetiger 1, anterior view. B, parapodium, chaetiger 9, anterior view.C, parapodium, chaetiger 34, anterior view.D, neurochaetae supra- and subacicular, chaetiger 1. E, notochaetae, parapodia 34. F, notochaetae homogomph spiniger. G, neurochaeta supracicular heterogomph spiniger. H, neurochaetae, parapodium 16. I, notochaetae homogomph falciger, parapodium 34. J, notochaetae heterogomph falciger, parapodium 28. Scale bars: 250 µm in A; 500 µm in B, C; 100 µm in D, E, H; 50 µm in F, G; 25 µm in I, J.

Figure 13. Nereis saramagoi, under scanning electron microscope.A, B, paratype 18. C, paratype 19. D–J, paratype 2. A, anterior body and midbody, dorsal view. B, anterior end, dorsal view.C, anterior end, ventral view.D, neurochaetae heterogomph falciger, parapodium 18. E, parapodium, chaetiger 18, posterior view. F, notochaeta homogomph spiniger, parapodium 29. G, neurochaetae supracicular heterogomph spinigers, parapodium 18. H, conical paragnaths, area II. I conical paragnath, area II. J, notochaetae homogomph falcigers, parapodium 29. Scale bars:500 µm in A, E; 200 µm in B, C; 25 µm in D, G, I, J; 75 µm in F, H.