Notomastus hutchingsae Magalhães, Lavesque & Lamarque, 2024, sp. nov.
Creators: name: Magalhães, Wagner F.
name: Lavesque, Nicolas
name: Lamarque, Bastien
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Capitellidae
Notomastus
Notomastus hutchingsae

description: Notomastus hutchingsae sp. nov.
Figures 2D–F, 3D, E & 4C, D.
Material examined. Holotype: MNHN-IA-2000-2087, incomplete, Northern Atlantic, Bay of Biscay, Arcachon Bay, Pyla channel CH 4, 44.613°N, 1.208°E, depth 11m. Paratypes: MZUSP 5655, Northern Atlantic, Bay of Biscay, Arcachon Bay, Pyla channel CH 1, 44.605°N, 1.211°E, depth 11m (2 incomplete spms).
Description. Holotype lacking posterior segments, about 14 mm long, 0.4 mm wide (largest width of thorax) for 23 chaetigers; largest paratype with 18 mm long, 0.4 mm wide for 32 chaetigers. Body elongate, thread-like, anterior thoracic segments (to segments 7–8) inflated without clear segmental grooves, constriction between segments 6– 7 present; segments faintly tessellated; last five thoracic segments clearly biannulated; last four segments with parapodia from second annulus (Figs 2D; 4B). Lateral or ventral grooves not observed. Colour in alcohol pale yellow.
Prostomium triangular with short palpode (Figs 2D; 4C, D). Eyespots absent; nuchal organs large, postero-lateral to prostomium. Peristomium not separated from prostomium or anterior thoracic segments forming indistinct anterior region (Figs 2D; 4C, D). Presumably, based on MGSP and present of lateral organs, peristomium followed by two achaetous segments (Fig. 2D).
Thorax with eleven segments; segments 1 and 2 achaetous; thoracic segment 3 uniramous. Thoracic segments 4–11 biramous with only capillaries in both rami (Fig. 2D). Lateral organs present in all thoracic segments, segments 1 and 2 with discreet ciliation and from segment 3 as a deep pit with protruding cilia; lateral organs in between notopodial and neuropodial chaetae (when present). Genital pores not observed. Thoracic capillaries bilimbate in two rows of four capillaries each. Thoracic chaetae emerging from body wall both noto- and neuropodia lateral.
Transition between thorax and abdomen marked by changes in shape of segments, constriction, chaetae and MGSP (Figs 2D, E; 4C). Anterior abdominal segments as long as wide becoming up to 5x longer than wider on posterior region of fragment (Fig. 4C). Notopodial tori glandular, positioned dorsally and forming a single dorsal glandular region with elongated lateral flaps; neuropodial tori also glandular, covering laterally segments and terminating dorsally on elongated projection, not fused ventrally (Figs 2D, E; 4C). Abdominal notopodia with 8–10 hooded hooks, separated by mid-dorsal gap. Anterior abdominal neuropodia with about 60 hooded hooks not increasing in number in following segments. Notopodial and neuropodial hooks similar in shape and length. Hooded hooks with short shaft, lacking distinct constriction, with apparently three rows of few teeth above main fang (Figs 2F; 3D, E).
Pygidium not observed.
Methyl Green Staining Pattern. Thoracic region clearly distinct from abdominal region by staining pattern (Fig. 4C). Thoracic segments staining light green throughout. Prostomium taking very light stain. A discrete line of green speckles present on each segment, passing by chaetae, indicating presence of achaetous segments 1 and 2. Abdominal region with distinct staining pattern with dark green speckles on dorsal region of segments leaving notopodial and neuropodial tori unstained (Fig. 4C).
Remarks. By the absence of hooded hooks on the eleven thoracic segments presumably having only capillaries, this species is best placed within Notomastus but does not fully agree with its generic definition. All three examined individuals presented the same thoracic configuration with two ‘achaetous’ segments prior to a uniramous thoracic segment 3 (chaetiger 1). The presence of lateral organs highlighted with Methyl Green staining confirmed the existence of two achaetous segments. It is not uncommon that capillaries may be broken off especially if they are in few numbers such as on anterior thoracic segments so we do not want to erect a new capitellid genus at this stage and molecular data is also required.
In addition to the distinct presence of two achaetous segments, this species is also distinct from its congeners by a combination of characters. The shape of the thoracic segments is very distinct with a constriction after segment 4 and after segment 6 segments becoming distinctly separated and biannulated. The abdominal notopodial lobes are fused and placed dorsally and abdominal neuropodial lobes forming a lateral glandular torus. Both notopodial and neuropodial abdominal tori have dorsal extensions. The species N. magnus Hartman, 1947, N. chilensis Hartmann-Schröder, 1965, N. fauveli Day, 1955, N. ceylonicus Pillai, 1961 and N. lobulatus García-Garza & de León-González, 2015 have fused notopodial lobes and neuropodial lobes that are well-developed and projected dorsally. The digitate dorsal projection of the neuropodial lobes in N. hutchingsae sp. nov. is distinct from the poorly or well-developed rounded endings in N. magnus, N. chilensis, N. fauveli and N. lobulatus. Notomastus ceylonicus has a similar shape of abdominal neuropodial lobes of N. hutchingsae sp. nov. but differs in relation to the MGSP and thoracic configuration (García-Garza & de León-González, 2015).
Notomastus exertilis Saint-Joseph,1906, was described from France but its generic placement was questioned by García-Garza & de León-González (2015) because it has 10 thoracic chaetigers with capillaries and two abdominal segments also with capillaries. This species was described as being a very long capitellid up to 1 m long and 800 segments with branchiae starting from abdominal segment 27 (Saint-Joseph, 1906). Notomastus latericeus Sars, 1851 is a commonly identified capitellid in French waters (e.g. Bachelet & Dauvin 1993; de Montaudouin & Sauriau 2000) and considered to have a broad distribution but many records need to be re-evaluated (García-Garza et al. 2019). The original description does not include any current relevant morphological characters to allow for distinction among other congenerics (see Sars 1851: p. 199–200) and the syntype needs to be redescribed. The French material identified as N. latericeus and described in Fauvel (1927: fig. 49a–f) includes dorso-lateral eyespots (absent in N. hutchinsae sp. nov.) and lacks dorsal extensions on the fused notopodial tori (present in N. hutchinsae sp. nov.).
Etymology. This species is dedicated to our friend and “the worms Lady” Dr. Pat Hutchings for her amazing contribution to polychaete taxonomy. She has always been a source of inspiration for WFM and acts as a mentor to NL.
Type locality. Bay of Biscay, Arcachon Bay.
Habitat. Medium sands with high hydrodynamic conditions, 11 m depth.
Distribution. Only known from the type locality.
description: Published as part of Magalhães, Wagner F., Lavesque, Nicolas & Lamarque, Bastien, 2024, Three new species of Capitellidae (Annelida) from France, pp. 273-289 in Zootaxa 5496 (2) on pages 282-284, DOI: 10.11646/zootaxa.5496.2.8, http://zenodo.org/record/13346707