Myrianida pinnigera ( Montagu, 1808 )

Nygren, Arne, 2004, Revision of Autolytinae (Syllidae: Polychaeta)., Zootaxa 680, pp. 1-314 : 149-150

Myrianida pinnigera ( Montagu, 1808) (Fig. 74A–E)

Nereis pinnigera Montagu, 1808: 111 , pl. 6, fig. 3.

Myrianida fasciata Milne Edwards, 1845: 180 , figs 65–68; Grube 1850: 310; Vaillant 1865; Quatrefages 1866: 63; Langerhans1879: 581; Malaquin 1890; 1893.

Myrianida maculata Claparède, 1868: 532 –533, pl. 13, fig. 1; Langerhans 1879: 582; Saint­Joseph 1887: 241 –246, pl. 13, fig. 119–129; Malaquin 1890; San Martín 2003: 466 –468, fig. 255A–H.

Myrianida pinnigera Allen 1915: 606 ; Dehorne 1917: 431 –439, figs 1–4; McIntosh 1908: 229 –232, pl. 71, fig. 5, 6, pl. 79, fig. 24, 24A; Potts 1911: 37 –39, fig. 12; Fauvel 1923: 322 –324, fig. 124A–H; Gravier & Dantan 1928: 98 –100, fig. 54; Okada 1929a; 1935; 1937; Cognetti 1961: 305; Parapar et al. 1996: 148; Nygren & Sundberg 2003: GenBank sequences, 16S rDNA partial sequence AF474252 , and 18S rDNA partial sequence AF474298 .

Mirianida pinnigera Cognetti 1958: 173 .

Material examined. France: 1 spm (rear end in author's collection for DNA analyses), Banyuls­sur­Mer, 42°29'N 03°10'E, dive, 30 m, "coralligene", May 1997. Spain: 4 spms (3 rear ends in author's collection for DNA analyses), Sancti Petri, Chiclana, 36°23'N 6°13'W, floating docks, 1 m, sponges, hydroids, Nov 1999.

Diagnosis. Myrianida with distinctly flattened dorsal cirrostyles; colour of live specimens white with orange to red dorsal patches.

Description. Length of stock 9.6–12.6 mm for 46–55 chaetigers, width 0.6–0.8 mm. Stolon chain, with numerous stolons, often exceeds length of stock. Live specimens white with orange to red patches dorsally on every third or fourth segment (Fig. 74A); eyes red. Ciliation as 2 trochs per segment.

Eyes confluent; eye spots absent. Palps in dorsal view projecting c. 1/5 of prostomial length, fused. Extension of nuchal epaulettes from end of chaetiger 6 to end of chaetiger 12 (n=4).

Median antenna reaching chaetiger 10–13 (n=3) in live specimens. Lateral antennae and dorsal tentacular cirri, length 1/2–2/3 of median antenna. Ventral tentacular cirri 1/2 as long as dorsal pair. First dorsal cirri as long as median antenna, second dorsal cirri as long as ventral tentacular cirri. From chaetiger 1–27 cirri with usual alternation in direction, followed by DUU + DDUU + DUU + DDUU + DDU (n=1), or UDUU + 3x (DUU) + DDUUU + DDU (n=1). Dorsal cirri from chaetiger 3, alternate in length; short cirri 2/ 3 in length of, or equal to, body width; long cirri equal to 1.5 times body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores and cirrostyles unequal (Fig. 74B); cirrophores and cirrostyles on short cirri 1/2–2/ 3 in length of its counterpart in long cirri; cirrophores on short cirri slightly shorter or equal to parapodial lobes, cirrophores on long cirri longer than parapodial lobes; cirrophores slightly shorter or equal to cirrostyles. Lateral antennae, tentacular cirri, and second dorsal cirri cylindrical; median antenna and first dorsal cirri cylindrical (n=2) or thick (n=1), cirri on chaetiger 2–4 with slightly flattened cirrostyles, cirri from chaetiger 5 with distinctly flattened cirrostyles (Fig. 74A).

Parapodial lobes of large size, with anterodorsal part prolonged (Fig. 74B). Anterior chaetigers with 3 aciculae, one in posterior part of stock. Chaetal fascicle with 15–20 compounds in anterior chaetigers, 10 in posterior part of stock. Compound chaetae with small distal tooth (Fig. 74C); serration present. Single thin bayonet chaetae (Fig. 74D), beginning at chaetiger 35.

Pharynx with sinuation anterior and lateral to proventricle. Trepan in chaetiger 5–6, with c. 40 unequal teeth in 3 sizes, arranged in groups with between 4–5 unequal teeth in each (Fig. 74E); large teeth may be fused with 1 or 2 adjacent teeth; trepan teeth arranged in 1 ring. Basal ring present; infradental spines present (Fig. 74E). Proventricle equal in length to 4 segments in chaetiger 11–17 with c. 34 rows of muscle cells (n=4). Pygidium with developing stolons.

Reproduction. Schizogamous reproduction by gemmiparity behind chaetiger 47–56. At the Plymouth region stolons seem to be produced only from April to October ( Okada 1935), but Gravier & Dantan (1928) found stolons of M. pinnigera in plankton for most part of the year in the Mediterranean.

Morphology of epitokous stages. Saint­Joseph (1887), Malaquin (1893), Dehorne (1917), and Gidholm (1967) provide information about stolon morphology. Male with 3 chaetigers in region a, tentacular cirri 1 pair, female with 2 ( Malaquin 1893) or 5 ( Dehorne 1917) or 6 ( Gidholm 1967) chaetigers in region a, tentacular cirri 1 pair. Cirri flattened as in stock.

Habitat. From low intertidal, to 10 m, among algae, sponges, hydroids, and tunicates. According to Okada (1935) always associated with the tunicates Ascidiella apersa and Phallusia mammilata .

Distribution. North East Atlantic, Mediterranean.

Remarks. See remarks for M. phyllocera .