Oligobregma nonatoi Mendes & Paiva & Rizzo 2024, sp. nov.
Creators: name: Mendes, Samuel Lucas Da Silva Delgado
name: Paiva, Paulo Cesar De
name: Rizzo, Alexandra E.
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Scalibregmatidae
Oligobregma
Oligobregma nonatoi

description: Oligobregma nonatoi sp. nov.
https://zoobank.org/NomenclaturalActs/baf39e52-2432-4b35-8a21-a871540b0f47
Figures 1–3
Type material. UERJ 9220 (Holotype: SANSED8; H7 R3; Lat: -23.849900; Long: -41.744800; 29 Mar 2021; 700 meters deep); UERJ 1120 (Paratype: HABITATS; HAB7H7 R2; Lat: -22.684635; Long: -40.000717; 18 Jul 2009; 790 meters deep; Complete specimen); UERJ 8755 (Paratype: AMBES11; A10 R2; Lat: -21.183086; Long: -38.468053; 11 Jun 2013; 2987 meters deep; Complete specimen); UERJ 9227 (Paratype: Ambes4; B10 R1; Lat: -21.077908; Long: -38.437133; 25 Dec 2011; 3007 meters deep; Complete specimen); UERJ9228 (Paratype: SANSED1; A8 R3; Lat: -27.296800; Long: -46.625200; 14 Jun 2019; 1045 meters deep; Complete specimen); UERJ9229 (Paratype: SANSED2; E9 R2; Lat: -25.001100; Long: -44.360900; 04 Jul 2019; 1298 meters deep; Complete specimen).
Additional material. UERJ 8753 (AMBES4; F9 R2; Lat: -20.484253; Long: -38.387639, 22 Dec 2011, 2504 meters deep, 1 specimen mounted to SEM, incomplete, anterior fragment).
Diagnosis. Triangular prostomium, with two short cylindrical horns, both projected upwards. Eyes absent. Acicular spines present from chaetiger 1–4 on notopodia and 1–3 on neuropodia. Acicular spines transitional on chaetiger 4 in notopodia and on chaetiger 3 in neuropodia. Lyrate chaetae present from chaetiger 4 on notopodia and from chaetiger 3 on neuropodia. Spinous chaetae absent. Notopodial lobe two times larger and longer than neuropodial lobe, both of same shape throughout. Dorsal and ventral cirri present from chaetiger 13. Pygidium triannulated, with long crenulated and fusiform terminal margin.
Description. Holotype complete, with 41 chaetigers, measuring 30 mm long, 5 mm wide on its expanded region and 2 mm wide on its narrowest region.
Large specimens, paratypes measuring 5–30 mm long, 1–5 mm wide on its expanded region and 0.5–2 mm wide on its narrowest region for 28–41 chaetigerous segments. Body arenicoliform, expanded on chaetigers 3–12. Colour in alcohol white to yellowish. Body surface covered by secondarily annulated rings. Secondary annuli composed of inconspicuous rounded to quadrangular pads in both anterior and posterior regions. Annuli’s pads on anterior region may be weaker in comparison with posterior region. Pads rarely present small individual blackish to dark blue glands inside, consisting of thin entangled cellular tubules.
Triangular prostomium, with two short cylindrical horns, both projected upwards (Figs 1A; 2A–B; 3A). Eyes absent. Nuchal organs not observed. Peristomium achaetous, uniannulated dorsally and triannulated ventrally (Fig. 1A). Mouth’s lips uniannulated. Proboscis smooth. Ventral groove present from chaetiger 1, with first pad asymmetrical, contributing to mouth’s lower lip formation (Figs 1A; 3A). Quadrangular biannulated pads on chaetigers 2–3, then triannulated on following chaetigers, forming a ventral mid-ridge up to the end of the body (Figs 1A; 3A). Each pad paired to a single chaetiger. Posterior pads smaller and narrower than anterior ones.
Dorsally and ventrally, chaetiger 1 presents two secondary annuli connected to parapodial lobes, plus one superior and one inferior intermediate annulation delimitating segment; from chaetiger 2 throughout, three secondary annuli connected to parapodial lobes, plus one superior and one inferior intermediate annulation delimitating segment (Figs 1A; 3A). Dorsal and ventral cirri present from chaetiger 13 (Figs 1D; 2F). Interramal papillae knob-like when everted, also observed from chaetiger 13 (Fig. 2E, G). Dorsal and ventral cirri with a broad basis transitioning to a rounded tip, reaching their larger size on midbody chaetigers and becoming smaller on posterior chaetigers (Figs 1D; 2F). Densely entangled black tubular glands may be present in all cirriferous chaetigers, filling completely internal space in well-preserved specimens, but sometimes concentrated in apical region (Fig. 2I–J).
Parapodial lobes reduced in anterior chaetigers; changing to asymmetrical projection with a broad basis transitioning abruptly to a pointed tip, from midbody to posterior chaetigers (Figs 1D; 2E‒F); this abrupt transition occurs on ventral side of notopodial lobe and on dorsal side of neuropodial lobe (Figs 1D; 2F). Notopodial lobe two times larger and longer than neuropodial lobe. Posteriorly, parapodial cirri and lobes reduce its size but maintain its shape.
Acicular spines present from chaetigers 1–4 on notopodia and 1–3 on neuropodia (Figs 1A‒B; 2C‒D; 3B). On notopodia, chaetigers 1–2 present two anterior rows of strong curved acicular spines, plus a posterior row of capillary chaetae; numbering nine spines on anterior row and eight spines on posterior row. Chaetigers 3–4 present one anterior row of weaker acicular spines plus two posterior rows of capillaries. Chaetiger 3 with nine curved acicular spines, weaker than chaetigers 1–2. Chaetiger 4 with five acicular spines, weaker and straighter than spines in chaetiger 3. Neuropodia of chaetigers 1–2 with two rows of curved acicular spines plus a posterior row of capillary chaetae; nine spines on anterior row and eight spines on posterior row. Chaetiger 3 with one row of five straight acicular spines, weaker than chaetigers 1–2, plus two rows of capillary chaetae (Fig. 2D). Acicular spines on notopodia on chaetiger 4 and neuropodia on chaetiger 3 transitional between distinct acicular spines and capillaries (Fig. 2C‒D).
Short spinous chaetae absent. Lyrate chaetae present on neuropodia from chaetiger 3, and on notopodia from chaetiger 4 (Figs 1C; 2H; 3C); numbering four in each fascicle on anterior chaetigers, reaching eight in number on midbody chaetigers, then reaching five in number on posterior chaetigers; always with unequal tynes (tyne’s ratio = 1.3). Capillaries organized in one row on chaetigers 1–2, then two rows from chaetiger 3 up to midbody and one row in posterior chaetigers. Pygidium triannulated, with long and fusiform terminal margin (Fig. 2K); terminal margin crenulated with 18 long lobules from which emerges four pygidial cirri projections, a dorso-lateral pair and a ventro-lateral pair. Pygidial cirri short and thin.
Remarks. Oligobregma nonatoi sp. nov. is morphologically similar to O. quadrispinosa Schüller & Hilbig, 2007, O. brasierae Wiklund et al., 2019, O. tani Wiklund et al., 2019 and O. bathyala Blake, 2023 by having acicular spines on chaetigers 1‒4 but they differ in several aspects. Oligobregma quadrispinosa presents acicular spines only on notopodia from chaetigers 1‒4, and lyrate chaetae from chaetiger 5; whereas O. nonatoi sp. nov. presents acicular spines in both rami from chaetiger 1‒3, lacking these spines in chaetiger 3 only on neuropodia, and its lyrate chaetae are present from chaetiger 4 on notopodia and 3 on neuropodia.
Oligobregma brasierae presents acicular spines in both noto and neuropodia from chaetigers 1‒4, parapodial cirri with gold pigmented granular glands within, and lyrate chaetae from chaetiger 5 in both rami; whereas O. nonatoi sp. nov. does not present these acicular spines on neuropodia of chaetiger 3, has strong black tubular glands within parapodial cirri and lyrate chaetae from chaetiger 4 on notopodia and 3 on neuropodia. Oligobregma tani possess acicular spines only in notopodia from chaetiger 1‒4; whereas O. nonatoi sp. nov. has acicular spines in both rami from chaetigers 1‒3 and more numerous lyrate chaetae on midbody chaetigers.
Oligobregma bathyala is the most similar species when compared to O. nonatoi sp. nov.. However, this species presents short spinous chaetae on notopodia of the chaetigers 1‒2, parapodia emerging as long conical lobes from midbody chaetigers, with noto and neuropodial lobes in the same size and shape; whereas O. nonatoi sp. nov. does not present spinous chaetae in any chaetiger and its parapodial lobes are asymmetrical, “knife-like”, with notopodial lobe two times longer and larger than neuropodial lobe. Additionally, in O. bathyala the lyrate chaetae tyne’s ratio is greater than O. nonatoi sp. nov., which are almost subequal.
Finally, the new species O. nonatoi sp. nov. presents an unusual annulation pattern, firstly described by Bakken et al. (2014) on the redescription of Pseudoscalibregma parvum (Hansen, 1879). The pattern consists of several secondary annuli emerging directly from the parapodial lobe plus an intermediate annulation separating the chaetiger from its superior and inferior neighbors (Fig. 3A). This intermediate annulation is not connected to any parapodial lobe and may cause confusion when identifying poorly preserved specimens in secondary annuli counting, which is an important feature to distinguish species within Scalibregmatidae genera.
Distribution. Oligobregma nonatoi sp. nov. was found living in low densities on continental slope of Espírito Santo, Campos and Santos Brazilian oceanographic basins from a bathymetric range of 700 to 3000 meters deep, predominantly among muddy sediments.
Etymology. The specific epithet “ nonatoi ” was chosen to honor Professor Dr. Edmundo Ferraz Nonato from São Paulo State University (USP), for his legacy as the “father” of the Brazilian Polychaete School.
description: Published as part of Mendes, Samuel Lucas Da Silva Delgado, Paiva, Paulo Cesar De & Rizzo, Alexandra E., 2024, First record of Oligobregma Kudenov & Blake, 1975 (Annelida: Polychaeta: Scalibregmatidae Malmgren, 1867) from Brazil with the description of three new species, pp. 80-98 in Zootaxa 5424 (1) on pages 83-87, DOI: 10.11646/zootaxa.5424.1.4, http://zenodo.org/record/10808050