Mediomastus biscayensis, Magalhães & Lavesque & Lamarque, 2024
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publication ID |
https://doi.org/ 10.11646/zootaxa.5496.2.8 |
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publication LSID |
lsid:zoobank.org:pub:1BF43637-4B8C-4E1C-B8DD-3BE03E70ADAC |
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DOI |
https://doi.org/10.5281/zenodo.13627225 |
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persistent identifier |
https://treatment.plazi.org/id/262FD17C-FFEB-FFA1-54FF-FE70E9AFF051 |
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treatment provided by |
Plazi |
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scientific name |
Mediomastus biscayensis |
| status |
sp. nov. |
Mediomastus biscayensis sp. nov.
Figures 2A–C View FIGURE 2 , 3A–C View FIGURE 3 & 4A, B View FIGURE 4 .
Material examined. Holotype: MNHN-IA-2000-2086, incomplete, Northern Atlantic , Bay of Biscay, West Gironde Mud Patch M 1-4KC, 45.602°N, 1.813°E, depth 68 m. GoogleMaps Paratype: MZUSP 5654 View Materials , incomplete, Northern Atlantic , Bay of Biscay, West Gironde Mud Patch M 1-4C, 45.615°N, 1.822°E, depth 70 m (2 spms) GoogleMaps .
Description. Holotype 8 mm long, 0.15 mm wide, for 20 segments. Body thin, elongate, first four thoracic segments short, becoming as long as wide to end of thorax; abdominal segments twice as longer as wide, moniliform ( Figs 2A View FIGURE 2 ; 3A View FIGURE 3 ). Dorsal and lateral grooves absent. Colour in alcohol pale yellow.
Prostomium short, conical, with papilliform palpode ( Figs 2A View FIGURE 2 ; 4B View FIGURE 4 ). Eyespots absent; nuchal organs present, postero-lateral to prostomium. Peristomium well-separated from prostomium and chaetiger 1, slightly longer than chaetiger 1 dorsally ( Figs 2A View FIGURE 2 ; 4B View FIGURE 4 ). Proboscis everted in one specimen, bulbous, bilobed with basal lobe covered by numerous short round papillae ( Fig. 2A View FIGURE 2 ).
Thorax with ten chaetigers ( Figs 2A View FIGURE 2 ; 3A View FIGURE 3 ); chaetigers 1–4 biramous with notopodial and neuropodial capillaries ( Fig. 2A View FIGURE 2 ); capillaries bilimbate ( Fig. 3A View FIGURE 3 ) organized in two rows of four capillaries in each fascicle. Chaetigers 5–10 with long-shafted hooded hooks ( Figs 2B View FIGURE 2 ; 3B View FIGURE 3 ). Notopodial and neuropodial long-shafted hooded hook numbering six per fascicle; hooks long, without distinct constriction and with at least four rows of small teeth above main fang ( Fig. 3B View FIGURE 3 ). Lateral organs and genital pores not observed.
Transition between thorax and abdomen marked by changes in shape of segments, slight constriction, and length of hooded hooks ( Fig. 4A View FIGURE 4 ). Abdominal segments longer than wider ( Fig. 4A View FIGURE 4 ) and becoming longer posteriorly. Notopodial and neuropodial tori short and well-separated emerging from posterior end of segments; notopodial tori dorsal and neuropodial tori ventral. Abdominal region with only hooded hooks throughout, slightly shorter than thoracic hooks ( Figs 2C View FIGURE 2 ; 3C View FIGURE 3 ), without distinct constriction and with 3–4 rows of few teeth (about six) above main fang; abdominal hooded hooks few numbering 6–10 per torus.
Pygidium not observed.
Methyl Green Staining Pattern. Chaetigers 5–9 with sparse green speckles ( Fig. 4A View FIGURE 4 ). Chaetigers 10 and 11 with dense green speckles ( Fig. 4A View FIGURE 4 ).
Remarks. There are 17 described species of Mediomastus , the most recent species described from Japan ( Tomioka et al. 2013, 2014) and China ( Lin et al. 2018) from specimens previously identified as Mediomastus californiensis Hartman, 1944 . The most comprehensive review of the genus was provided by Warren et al. (1994) together with a comparative table with diagnostic characters. An updated key to species was provided in Tomioka et al. (2014). Mediomastus biscayensis sp. nov. is distinct from its congeners by a combination of characters: i) bilimbate thoracic capillaries; ii) thoracic and abdominal hooks similar in shape and with slight difference in length; iii) distinct MGSP: chaetigers 5–9 with sparse green speckles and chaetigers 10–11 with dense green speckles (See Table 1 View TABLE 1 ).
Mediomastus capensis Day, 1961 is a similar species with bilimbate capillaries and by having abdominal hooks that are slightly shorter than thoracic ones ( Warren et al. 1994). It differs from M. biscayensis sp. nov. in that the thoracic capillaries that are ‘curved into minute hooks at tip’ ( Warren et al. 1994) whereas capillaries in M. biscayensis sp. nov. are long and bilimbate, without curved hooked tips. The Methyl Green staining pattern is also distinct with a green band around the posterior half of chaetiger 9 in M. capensis and a more intense staining in chaetigers 10–11 than in M. biscayensis sp. nov. The European species Mediomastus fragilis has records in the Mediterranean ( Capaccioni-Azzati 1985) and Bay of Biscay, France ( Bachelet & Dauvin 1993; de Montaudouin & Sauriau 2000) but it is distinct from the new species by the presence of a small and rounded prostomium, chaetigers 10 and 11 transitional, thoracic hooks long and abdominal hooks short, and indistinct MGSP ( Warren et al. 1994).
Etymology. This species is described after its type locality Bay of Biscay.
Type locality. Bay of Biscay , West Gironde Mud Patch .
Habitat. Muddy bottoms, around 70 m depth.
Distribution. Known only from the type locality.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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