Pherusa obscura Quatrefages, 1849

Salazar-Vallejo, Sergio I., 2014, Revision of Pherusa Oken, 1807 (Polychaeta: Flabelligeridae), Zootaxa 3886 (1), pp. 1-61 : 31-33

publication ID

https://doi.org/ 10.11646/zootaxa.3886.1.1

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lsid:zoobank.org:pub:6ADD860C-D60C-448D-BC11-19EDB74013EE

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https://treatment.plazi.org/id/7A4987D3-3258-FFBA-FF37-FF102C1AFDF2

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scientific name

Pherusa obscura Quatrefages, 1849
status

 

Pherusa obscura Quatrefages, 1849 View in CoL , reinstated

Figure 11 View FIGURE 11

Pherusa obscura Quatrefages, 1849:289–290 View in CoL , Pl. 9, Figs 15–17 View FIGURE 15 View FIGURE 16 View FIGURE 17 .

Trophonia borealis Hansen, 1880:230 View in CoL , Pl. 4, Figs 8–12 View FIGURE 8 View FIGURE 9 View FIGURE 10 View FIGURE 11 View FIGURE 12 ; 1882:38, Pl. 7, Figs 13–16 View FIGURE 13 View FIGURE 14 View FIGURE 15 View FIGURE 16 .

Stylarioides plumosus .— Haase 1915: 187–192 (partim, non Müller, 1776).

Stylarioides plumosa View in CoL . — Fauvel 1927:116–117, Fig. 41a–g (partim, non Müller, 1776).

Type material. Northeastern Atlantic Ocean, English Channel. Holotype ( MNHN 627 About MNHN ), Saint-Vaast-la-Hogue, Basse Normandie, France, 1868 (date probably wrong since the species was described in 1849).

Additional material. Norway. One specimen ( SMF 15336), Kroken, 27 Feb. 2005, Udekem & Acoz, coll. (preserved in alcohol; 62 mm long, 5 mm wide, cephalic cage 10 mm long, 66 chaetigers; dorsal papillae in chaetigers 1–3 forming larger sediment particles, 6 rows per segment; neurohooks from chaetiger 4, 3–5 anteriorly, 3–4 posteriorly per fascicle; notochaetae about as long as ½ body width, 5–6 per bundle; parapodia with 2–3 papillae slightly longer than other papillae of the same segment; oocytes black, perhaps by preservative, about 100?m) . Denmark. Four specimens, 3 complete ( LACM 6531 About LACM ), Øresund , RV Thelma, Modiolus community, 1 Jul. 1960 (12.5–51.0 mm long, 3–7 mm wide, cephalic cage 7–12 mm long, 33–65 chaetigers; dorsal papillae in anterior chaetigers long, with sand particles, 4–5 or 5–6 rows per segment; neurohooks from chaetiger 4, 3–5 anteriorly, 3–4 posteriorly per fascicle; notochaetae as long as ½ body width, 4–5 per bundle; parapodia with papillae slightly longer than other papillae of the same segment). One specimen ( MNHN A183 About MNHN ), broken into two pieces, partially dehydrated, Steensund , Hyllekrog , Lolland, Denmark, 26 Aug. 1908, C. Gravier, coll. (28+ 18 mm long, 4 mm wide, cephalic cage 10 mm long, 66 chaetigers; 5 notochaetae per bundle in chaetiger 13). One specimen ( MNHN A183 About MNHN ), Steensund, Hyllekrog (54.36° N, 11.30° E), 26 Aug. 1908, C. Gravier, coll. (48 mm long, 5 mm wide, cephalic cage 10 mm long, 66 chaetigers; dorsal papillae on anterior chaetigers long, sediment mostly eroded, 4–5 rows per segment; neurohooks from chaetiger 4, 3–4 anteriorly, 3 posteriorly per fascicle; notochaetae as long as 1/3 body width, 5–6 per bundle) GoogleMaps .

Description. Holotype (MNHN 627) complete, dried-out, pale, distorted ( Fig. 10A, B View FIGURE 10 ), 30 mm long, 2 mm wide, cephalic cage 7 mm long, 47 chaetigers. Body papillae digitate (collapsed in holotype), with some sand particles on a few anterior chaetigers; 5–6 transverse rows of papillae on medial or posterior segments.

Cephalic hood exposed in a non-type specimen (LACM 6531), smooth, margin papillated ( Fig. 11C View FIGURE 11 ). Prostomium projected cone; eyes brownish, anterior eyes twice as large as posterior ones ( Fig. 11D View FIGURE 11 ). Caruncle short, triangular. Palps and branchiae lost. Lips distorted by eversion of ventral pharyngeal organ.

Branchial scars arranged as two concentric rows; one continuous row with 4 filaments with interbranchial, round, glandular lobes; four other filaments into two lateral groups, each with two filaments per side; size relationship to palps unknown. Nephridial lobes pale, short, digitate, emerging under division of branchial rows.

Cephalic cage chaetae ¼ as long as body, or 3.5x longer than body width. Chaetigers 1–3 forming cephalic cage; chaetae progressively smaller, arranged in short lateral series, about 8 per ramus.

Anterior dorsal margin of first chaetiger without a distinct medial lobe (probably eroded). Anterior chaetigers with longer papillae laterally, not associated with chaetal lobes. Chaetigers 1–3 progressively longer. Chaetal transition from cephalic cage to body chaetae abrupt; anchylosed, falcate, blunt neurohooks start in chaetiger 4. Gonopodial lobes not seen.

Parapodia poorly developed, slightly larger in a few anterior chaetigers, in subsequent chaetigers chaetae emerge from body wall. Parapodia lateral; medial neuropodia ventrolateral. Notopodia and neuropodia with short papillae, close to each other.

Medial notochaetae in transverse to oblique series; all multiarticulated capillaries, articles short in a reduced basal region, then medium-sized medially becoming slightly longer distally ( Fig. 11E View FIGURE 11 , insets), about 8–9 per bundle, as long as 1/3 body width. Neurochaetae multiarticulated capillaries in chaetigers 1–3; brownish, blunt neurohooks from chaetiger 4, mostly 4 per bundle in anterior and medial chaetigers ( Fig. 11F View FIGURE 11 ), 3 in posterior chaetigers ( Fig. 11G View FIGURE 11 ).

Posterior end damaged, truncate conical, anus terminal, without anal cirri. One specimen (SMF 15336) with dark brown oocytes, about 100 µm in diameter.

Variation. The specimens show variations in some morphological features as follows. The number of notochaetae was 5–6 per bundle (chaetiger 10) but some chaetae may be broken and the holotype has 8–9 notochaetae per bundle.

Remarks. Pherusa obscura Quatrefages, 1849 , reinstated, groups with other species with dorsal papillae with sand particles such as P. andersonorum n. sp., P. aspera ( Stimpson, 1854) , P. incrustata Quatrefages, 1866 , reinstated, and P. neopapillata Hartman, 1961 . Sediment particles are present along the body in P. andersonorum and P. aspera , whereas the other species have them restricted to anterior or to anterior to medial segments. However, in P. obscura the cephalic cage is 3x as long as body width, and has 5–6 transverse series of papillae per segment, whereas in P. incrustata and P. neopapillata cephalic cages are smaller (twice as long as body width), and they have more transverse rows of papillae (7–10).

The lumping of the typical P. plumosa with P. obscura stems from the revision by Haase (1915). He studied many specimens including some from Arctic and Baltic Sea localities, whose number of notochaetae was very variable. Likewise, he overlooked the indication by Hansen (1880) that Trophonia borealis , a junior synonym of P. obscura , had sand and mud particles over the dorsal papillae. This was followed by Fauvel (1927:116) and by Støp- Bowitz (1948a:13). However, they were lumping together several different populations, some of which may have been of different species. Since he failed to provide any details about the papillae and the sediment on them, it is difficult to define this issue. The species can be defined by having large, sand particles along few anterior chaetigers and fine particles along the rest of the body. Pherusa incrustata , however, has been redefined above as having large, sand particles along the dorsum of the whole body.

The original description of Pherusa obscura by Quatrefages (1866:479) was based on a very large specimen (80 mm long, 9 mm wide, about 50 chaetigers). For the chaetal features, he stated (p. 480): “Les pieds sont biramés et à rames écartées et peu saillantes. La supérieure porte quatre à cinq soies simples et ordinaires. A la rame inférieure, on trouve trois soies simples aussi, mais renflées et recourbées en crochet à leur extrémité. This translates as: ‘The feet are biramous with distinct little prominent rami. The dorsal carries four to five simple ordinary chaetae. In the ventral, we find three simple chaetae too, but distally swollen and falcate.” Therefore, because the specimen indicated as the holotype differs in size and collecting date, this reinstatement is made with some hesitation because this specimen is not the original one. Better topotype specimens would help clarify if this is the corresponding species although the type material might be lost.

Distribution. Scandinavia to the Mediterranean Sea, in subtidal depths and in mussel beds. This is a wide distribution but with current characters they cannot be separated.

SMF

Forschungsinstitut und Natur-Museum Senckenberg

MNHN

Museum National d'Histoire Naturelle

Kingdom

Animalia

Phylum

Annelida

Class

Polychaeta

Order

Terebellida

Family

Flabelligeridae

Genus

Pherusa

Loc

Pherusa obscura Quatrefages, 1849

Salazar-Vallejo, Sergio I. 2014
2014
Loc

Stylarioides plumosa

Fauvel, P. 1927: 116
1927
Loc

Stylarioides plumosus

Haase, P. 1915: 187
1915
Loc

Trophonia borealis

Hansen, A. 1880: 230
1880
Loc

Pherusa obscura

Quatrefages, A. de 1849: 290
1849
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