Pherusa Oken 1807

Pherusa Oken, 1807, restricted

Pherusa Oken, 1807:1168, 1815:377.— Støp-Bowitz, 1948a:13 (partim).— Day, 1967:658 (partim).— Fauchald, 1977:117 (partim).

Pennaria de Blainville, 1818:81 (non Oken, 1815, nec Goldfuss, 1820).

Flemingia Johnston, 1846:447.

Type species: Amphitrite plumosa Müller, 1776, by original designation.

Diagnosis (emended). Body cylindrical, tapered posteriorly. Cephalic cage well developed. Some species with anterior chaetigers with large papillae over their anterior margins. Body papillae cylindrical, digitate, capitate, sometimes forming sediment tubercles, arranged in alternating transverse bands. Medial chaetigers with falcate anchylosed neurohooks, shorter than body width; tips rarely paler, stiff. Branchiae cirriform, eight filaments, arranged into a continuous posterior row with four filaments, and two lateral groups, each with two filaments.

Remarks. After Fauchald (1977), there are several genera that have been regarded as junior synonyms of Pherusa: Balanochaeta Chamberlin, 1919, Flemingia Johnston, 1846, Lophocephalus Costa, 1841, Stylarioides delle Chiaje, 1841 (sic), and Trophonia Cuvier, 1830 (sic). This synonymy should be restricted. Balanochaeta has Stylarioides eruca Claparède as the type species, but the latter belongs in Piromis Kinberg, 1867, as shown by Day (1973:108–109; Salazar-Vallejo 2011a). Stylarioides was recognized as an independent genus (Salazar-Vallejo 2011b) because it has two pedunculate branchiae, each with filaments spirally arranged, not only eight similar cirriform branchiae as is the case in Pherusa; as such, Stylarioides includes both Lophocephalus and Trophonia.

The restricted synonymy should only include Pennaria de Blainville, 1818, a genus overlooked by Fauchald (1977), and Flemingia Johnston, 1846. De Blainville (1818:81) introduced the former after presenting the original diagnosis by Oken (1815), by indicating that he recognized a distinct genus and thought about using a name for it, before knowing Oken’s diagnosis: “... Pennaria avant de connaitre l’ouvrage de M. Ocken (sic), ne renferme que l’ Amphitrite plumosa de Muller;”, and consequently it is a junior objective or homotypic synonym of Pherusa. On the other hand, Flemingia was proposed (Johnston 1846:447) to host Amphitrite plumosa, type species for Pherusa, and F. muricata Johnston, 1832 (sic, not a publication), which is a nomen nudum since no description was included. It must be noticed that this latter name was introduced by Baird (1834:15), so that the correct name should be Fleminia muricata Johnston in Baird, 1834. However, Flemingia, or Fleminia, was withdrawn by Johnston himself by stating that he had missed the generic definition, and used Trophonia instead (Johnston 1865:223, footnote). However, because the genus was proposed to host the type species of Pherusa, Flemingia also became its junior objective or homotypic synonym (ICZN 1999, Art. 61.3.3).

Hartmann-Schröder (1996:419) proposed the most recent diagnosis for Pherusa. The main difference with the above emended diagnosis is that she included P. flabellata Sars, 1872 and P. falcata Støp-Bowitz, 1948 as provided with pseudocompound neurochaetae. As shown elsewhere (Salazar-Vallejo 2013:239), the former species belongs in Therochaeta Chamberlin, 1919, whereas the latter lacks pseudocompound neurohooks but has lamispines, and consequently is transferred below to Lamispina n. gen. The emended diagnosis restricts the type of neurochaetae present, either falcate, tapered cylindrical hooks or lamispines; this is the main difference between this diagnosis and with previous ones. This is an important and easy observed difference and is used to separate Pherusa and Lamispina n. gen.

As currently restricted, Pherusa contains 13 species, including six newly described: P. plumosa (Müller, 1776), type-species, restricted, from Greenland, P. affinis (Leidy, 1855) from the NW Atlantic, P. andersonorum n. sp. from the NE Pacific (California), P. aspera (Stimpson, 1854) from the NW Atlantic, P. hobsonae n. sp. from the NE Pacific (Washington), P. incrustata Quatrefages, 1866, reinstated from the Mediterranean Sea, P. mikacae n. sp. from the Adriatic Sea, P. moorei n. sp. from the NW Pacific (Japan), P. neopapillata Hartman, 1961 from the NE Pacific (California), P. nipponica n. sp. from the NW Pacific (Japan), P. obscura Quatrefages, 1866 reinstated from the NE Atlantic (France), P. papillata (Johnson, 1901) from the NE Pacific (Washington), P. rullieri n. sp. from the Eastern tropical Atlantic (Benin), and P. sibogae (Caullery, 1944) n. comb. from Western Timor, Indonesia.

Distribution. Pherusa species live mostly in temperate environments, only two species are known from tropical, subtidal depths. Their depth distribution indicates the species are mostly found in shallow water, with nine species present from subtidal depths to about 50 m, two have depth distributions to about 200 m, and two in deeper waters, down to about 600 m.

Key to Pherusa- like genera

1. Medial chaetigers with neurochaetae falcate, shorter than body width, rarely pale distally, always unidentate, rarely aristate.............................................................................. Pherusa Oken, 1807 restricted

- Medial chaetigers with neurochaetae slightly curved, as long as body width, each basally cylindrical, distally flat, pale or hya- line, tips sometimes hooded or bidentate..................................................... Lamispina n. gen.

Key to species of Pherusa Oken, 1807 restricted

1. Body papillae covered by sediment particles, forming a thick layer or ovoid structures on them........................ 2

- Body papillae with few or completely lacking sediment particles, never forming tubercles........................... 8

2(1). Papillae of anterior chaetigers with only fine sediment particles................................................ 3

- Papillae of anterior chaetigers with sand grains.............................................................. 4

3(2). Medial chaetigers with 6–8 transverse series of dorsal papillae; neurohooks brownish, slightly falcate................................................................................. P. plumosa (Müller, 1776) restricted, Greenland

- Median chaetigers with 3–4 transverse series of dorsal papillae; neurohooks yellowish to brown, markedly curved.............................................................................. P. nipponica n. sp. NW Pacific (Japan)

4(2). Sand particles present on entire dorsal surface.............................................................. 5

- Sand particles restricted to dorsal surface of anterior or anterior to medial chaetigers................................ 6

5(4). Medial and posterior parapodia with 5–6 neurohooks (body 2 mm wide)......... P. aspera (Stimpson, 1854) NW Atlantic

- Medial and posterior parapodia with 3–4 neurohooks (body 2.8 mm wide).. P. andersonorum n. sp. NE Pacific (California)

6(4). Medial chaetigers with 5–6 transverse series of papillae; cephalic cage chaetae more than 3x as long as body width.......................................................... P. obscura Quatrefages, 1849 reinstated, NE Atlantic (France)

- Medial chaetigers with 7–10 transverse rows of papillae; cephalic cage chaetae 2–3 x as long as body width............. 7

7(6). Sand particles present dorsally on anterior to medial segments; cephalic cage chaetae abundant (10–14 notochaetae, 6–8 neurochaetae per bundle).................................. P. incrustata Quatrefages, 1866 reinstated, Mediterranean Sea

- Sand particles restricted to anterior segments; cephalic cage chaetae sparse (6–8 chaetae per fascicle)........................................................................... P. neopapillata Hartman, 1961 NE Pacific (California)

8(1). Neurohooks from chaetiger 4............................................................................ 9

- Neurohooks from chaetiger 5, slightly curved, blunt; cephalic cage chaetae more than twice as long as body width; chaetigers 1–3 with a series of large digitate papillae over their anterior margin................ P. affinis (Leidy, 1855) NW Atlantic

9(8). Medial and posterior neurohooks falcate.................................................................. 10

- Medial and posterior neurohooks slightly curved, aristate.................................................... 12

10(9). Medial chaetigers with 2–3 transverse series of dorsal papillae; medial parapodia with 5–6 notochaetae, 2–3 neurochaetae; cephalic cage twice as long as body width............................... P. hobsonae n. sp. NE Pacific (Washington)

- Medial chaetigers with more than 10 transverse series of dorsal papillae per segment............................... 11

11(10). Dorsal papillae globose; integument pale; medial parapodia with 3–4 neurohooks; medial chaetigers with 10–12 transverse series of papillae........................................... P. papillata (Johnson, 1901) NE Pacific (Washington)

- Dorsal papillae depressed; integument brownish; medial parapodia with 5 neurohooks; medial chaetigers with 16–20 transverse series of papillae................................................. P. mikacae n. sp. Adriatic Sea (Croatia)

12(9). Cephalic cage chaetae twice as long as body width.......................................................... 13

- Cephalic cage chaetae 4x longer than body width; medial chaetigers with 25–30 transverse series of dorsal papillae............................................................................... P. moorei n. sp. NW Pacific (Japan)

13(12). Medial chaetigers with 20–26 transverse series of dorsal papillae, without sand grains............................................................................................. P. rullieri n. sp. Eastern tropical Atlantic (Benin)

- Medial chaetigers with one transverse series of three papillae, with sand grains....................................................................................... P. sibogae (Caullery, 1944) n. comb. Western Timor, Indonesia