Myrianida Milne Edwards, 1845

Nygren, Arne, Sundkvist, Tobias, Mikac, Barbara & Pleijel, Fredrik, 2010, Two new and two poorly known autolytines (Polychaeta: Syllidae) from Madeira and the Mediterranean Sea, Zootaxa 2640, pp. 35-52 : 49-50

Myrianida Milne Edwards, 1845

Myrianida longoprimicirrata ( López, San Martín & Jiménez, 1997) ( Figs 4 A–C, 5F–H)

Autolytus longoprimicirrata López, San Martín & Jiménez, 1997: 296 –298, fig. 2A–G; San Martín 2003: 492 –494, fig. 271A–F.

Myrianida longoprimicirrata Nygren 2004: 141 –142, fig. 69A–B.

Material examined. Holotype. Chafarinas Islands, 15 m, in Cladocora caespitosa blocks, 15 Sept 1992, MNCN 16–01/2122. Paratypes. Same locality as holotype, two specimens ( MNCN 16–01/2122b). Other material. Croatia, Istria, Sv. Ivan, 45°02.755'N 13°37.422'E, 5–15 m, Padina and other algae, SCUBA, 19 Sept 2008, two specimens preserved on slides ( GNM Polychaeta 13214a, 13215), rear ends preserved in alcohol, of which one is used up for DNA extraction ( GNM Polychaeta 13214b); Croatia, Istria, Banjol, 45°04.442'N 13°36.664'E, 15–27 m, precoralligene, SCUBA, 23 Sept, 2008, two specimens preserved on slides ( GNM Polychaeta 13216a, 13217a), rear ends preserved in alcohol (Polychaeta GNM 13216b, 13217b); Croatia, Istria, 2 km west of Rovinj, 45°05.220'N 13°36.517'E, 27 m, sponges, hydroids, and Holothuria sp., Agassiz trawl, 25 Sept 2008, two specimens preserved in alcohol ( GNM Polychaeta 13218, 13219); Croatia, Istria, St Andrew’s Island, 45°02.561'N 13°36.792'E, 10–16 m, precoralligene, SCUBA, 24 Sept 2008, one specimens preserved in formalin ( GNM Polychaeta 13220); France, Banyuls-sur-mer, 42°29.94’N 03°08.46’E, 25 m, corraligene, SCUBA, 7 April 2009, two specimens preserved in alcohol of which one is used up for DNA extraction ( GNM Polychaeta 13221), two specimens preserved on slides ( GNM Polychaeta 13222a, 13223a), posterior ends preserved in alcohol ( GNM Polychaeta 13222b, 13223b).

Diagnosis. Myrianida with long cirrophores on the long cirri from anterior chaetigers, and a trepan with 33–45 equal, or nearly equal, teeth.

Description. Length 4–14 mm for 43–124 chaetigers, width at level of proventricle, excluding parapodial lobes, c. 0.3 mm. Live specimens yellowish to orange, with more or less distinct bands of orange glands across each segment, giving an orange-banded impression ( Fig. 4 A). Body shape, excluding parapodial lobes, cylindrical in transection, ventrally flattened. Body fairly constant in width, with tapering posterior end. Ciliation on nuchal epaulettes and as a single ciliary troch per segment. Prostomium rounded rectangular. Four eyes with lenses, anterior pair larger, confluent in dorsal view ( Fig. 4 B); eye spots absent. Palps in dorsal view projecting c. half the prostomial length ( Fig. 4 B), fused. Nuchal epaulettes extending to between beginning of chaetiger 3 and end of chaetiger 5 ( Fig. 4 B). Prostomium with three antennae; median antenna inserted medially on prostomium, lateral antennae on anterior margin. Tentacular cirri two pairs. Median antenna reaching c. chaetiger 20. Lateral antennae, and dorsal tentacular cirri 1/3–1/2 as long as median antenna; first dorsal cirri as long as median antenna; ventral tentacular cirri and second dorsal cirri c. half as long as dorsal tentacular cirri. Dorsal cirri from chaetiger 1 with following alternation in direction, where D=cirri pointing down and U=cirri pointing up: U DDU DU DDU followed by eight DU-groups, 4 DDUUgroups, and up to 28 DDU-groups. From chaetiger 3 dorsal cirri alternating in length; short cirri as long as c. 4/5 of body width, long cirri as long as c. 1.2 times body width. Cirrophores on tentacular cirri and all dorsal cirri. Cirrophores alternating in length along the body; cirrophores on short cirri c. half as long as cirrophores on long cirri. Cirrostyles alternating in length in anterior and posterior chaetigers, but not in median chaetigers; cirrostyles on short cirri c. 1.5 times as long as cirrostyles on long cirri in anterior chaetigers, equally long in median chaetigers, and 2/3 as long in posterior chaetigers. Cirrophores on short cirri equal or slightly longer than parapodial lobes, cirrophores on long cirri longer than parapodial lobes. Cirrophores shorter than cirrostyles on short cirri, cirrophores longer than cirrostyles on anterior long cirri, equal in length in mid-body long cirri, and shorter in posterior long cirri ( Fig. 4 A). Parapodial lobes of medium size, rounded. Aciculae 2–3 in anterior chaetigers, 1or 2 in median and posterior chaetigers. Chaetal fascicle with 10–12 compounds in anterior chaetigers, 6–9 in median and posterior. Compound chaetae with small distal tooth ( Fig. 5 F) and serrated blade. Single thin bayonet chaetae ( Fig. 5 G), beginning on chaetiger 20–31. Pharynx with sinuation mostly anterior to proventricle ( Fig. 4 A). Trepan in chaetiger 2–4, with 33–45 equal, or nearly equal, teeth ( Fig. 5 H). Basal ring present, infradental spines present. Proventricle as long as 4–6 segments, in chaetiger 10–20 ( Fig. 4 A) with 30–37 rows of muscle cells. Anal cirri as long as 1.5–3 times body width.

Reproduction. Probably with schizogamy. Three specimens have pink eggs from about chaetiger 40, one of them with a newly regenerating posterior end behind chaetiger 63 ( Fig. 4 C).

Habitat. Among Cladocera caespitosa blocks, Padina and other algae, and in coralligene, 15– 30 m.

Distribution. Mediterranean, from Chafarinas Islands in Morocco, Istria in Croatia, and Banyuls-sur-Mer in France.

Intraspecific genetic variation. A single haplotype in the four specimens from Banyuls-sur-mer, and four haplotypes in the four specimens from Croatia were found in COI. The haplotypes from Croatia cluster together but are separated from each other with 1–4 mutational steps (uncorrected p = 0.41±0.16%). This group is in turn separated from the single Banyuls-sur-Mer haplotype with a minimum of six mutational steps (uncorrected p=1.11±0.18%). As for 16SrDNA, we found two haplotypes in the two Banyuls-sur-Mer specimens, and a single haplotype in the four Croatian specimens. The two Banyuls-sur-Mer haplotypes are separated from each other by a single mutational step, and the Croatian haplotype is separated by a single mutational step from the closest Banyuls-sur-Mer haplotype.

Remarks. Myrianida longoprimicirrata is a poorly known member of the genus, never recorded after the original description. The relationship between cirrophores and cirrostyles was not possible to assess in the original description or from the types. In the present material, the cirrophores are longer than cirrostyles on long anterior dorsal cirri and, then gradually become shorter towards the posterior end where they are shorter than cirrostyles. The only Myrianida which have cirrophores longer than cirrostyles on the long cirri are M. dentalia ( Imajima, 1966) , M. langerhansi , M. pentadentata ( Imajima, 1966) , M. multidenticulata ( Westheide, 1974) , M. pulchella ( Day, 1953) , and M. rangiroaensis ( Imajima, 1966) . We lack molecular data for the latter three species, but among the sequenced species M. longoprimicirrata is most closely related to M. pentadentata . Morphologically M. longoprimicirrata may be separated from all the aforementioned species by the 33–45 equal, or nearly equal, teeth, on the trepan, compared to a varied number and arrangement of distinctly unequal teeth in all species except M. pentadentata which has five equal teeth.

Figures

FIGURE 4. Myrianida longoprimicirrata. A. Dorsal view, compl. ete specimen (spm 5). B. Dorsal view, anterior end (spm 7). C. Ventral view, posterior end with regenerating segments (GNM Polychaeta 13219). Scale lines A 1 mm, and B, C 0.1 mm.

FIGURE 5. Proceraea albocephala, new species. A. Holotype, compound chaetae and bayonet chaeta, chaetiger 10. B. Trepan, dorsal view (spm 5). Proceraea madeirensis. C. Compound chaetae and bayonet chaeta, chaetiger 12 (spm 2). D. Compound chaetae, chaetiger 30 (spm 2). E. Trepan, dorsal view (spm 1). Myrianida longoprimicirrata. F. Compound chaetae, chaetiger 20 (spm 5). G. Bayonet chaeta, chaetiger 25 (spm 5). H. Trepan, dorsal view (spm 3). Scale lines A – H 0.1 mm.