Myrianida Milne Edwards 1845
Creators: name: Nygren, Arne
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Phyllodocida
Syllidae
Myrianida

description: Myrianida Milne Edwards, 1845
Scolopendra Slabber, 1781: 44 –46, pl 10, fig. 4–5. Nomen oblitum according to Article 23.9.1 (ICZN 1999).
Podonereis Blainville, 1818: 83. Nomen oblitum according to Article 23.9.1 (ICZN 1999).
Myrianida Milne Edwards, 1845: 180, figs 65–68. Nomen protectum according to Article 23.9.1 (ICZN 1999).
Autolytus Grube, 1850: 310, table facing 281.
Diploceraea Grube, 1850: 312, table facing 281.
Sacconereis J. Müller, 1853: 31.
Crithida Gosse, 1855: 309 –310, pl. 8, fig. 5.
Sylline Grube, 1860: 87 –88, pl. 3, fig. 8.
Autolytides Malaquin, 1893: 76.
Nomenclatural remarks. Scolopendra was described for a female stolon. Podonereis was erected for Nereis punctata (Hesionidae: Nereimyra) and Nereis corniculata, the latter a male stolon. Neither names have been in use since they were introduced, the conditions in Article 23.9.1.1 (ICZN 1999) are hence fulfilled. The taxon Myrianida has been used by the following authors Day (1960; 1967), Cognetti (1958; 1961), Clark (1961), Hartman (1966a, b), Rullier (1964), Hartmann­Schröder (1965a), Imajima (1966; 1967; 1982), Gidholm (1967), Bellan (1969), Uebelacker (1984), San Martín & Alós (1989), Hartmann­ Schröder & Rosenfeldt (1990; 1992), Garwood (1991), San Martín (1994; 2003), Parapar, San Martín, Besteiro & Urgorri (1996), López & San Martín (1997), Franke (1999), Nygren & Gidholm (2001), Nygren & Sundberg (2003), thus the conditions in Article 23.9.1.2 (ICZN 1999) is met with.
Linnean name definition. Type species Myrianida fasciata Milne Edwards, 1845, by monotypy. Note that M. fasciata is considered to be a junior synonym to M. pinnigera (Montagu, 1808).
Stem­based name definition. Myrianida refers to the most inclusive clade comprising M. fasciata Milne Edwards, 1845, M. prolifera (Müller, 1788), and M. irregularis (Imajima & Hartman, 1964), but not Epigamia noroi (Imajima & Hartman, 1964), or Proceraea picta Ehlers, 1864.
Apomorphies. Clade supported by two morphological apomorphies (Fig. 4): 1) number of teeth equals 26–30 (character 40), other most parsimonious reconstructions (MPRs) possible, character state change is a parallelism, later reversed and further changed within clade; 2) number of different sizes of teeth in trepan equals 3 (character 41), other MPRs possible, character state change is a parallelism, later reversed and further changed within clade, character state unknown in some taxa.
General description.
Atokous form. Length 1.2–21 mm for 16–109 chaetigers; width, measured at level of proventricle excluding parapodial lobes, 0.2–1.4 mm. Body shape, excluding parapodial lobes, cylindrical to rounded rectangular in transection, venter flattened; body width fairly constant with tapering end. Ciliation as 1 or 2 trochs per segment (unknown in some taxa). Prostomium rounded rectangular. Four eyes, with lenses, in trapezoid arrangement, anterior pair larger. Eyes confluent or separated; eye spots absent or present. Palps fused at base or completely fused; in dorsal view not projecting in front of prostomium, or projecting 1/5–2/3 of prostomial length. Extension of nuchal epaulettes to between end of tentacular segment and end of chaetiger 12.
Prostomium with 3 antennae; median antenna inserted medially on prostomium, lateral antenna on anterior margin. Tentacular cirri 2 pairs. Cirri, cirrophores, cirrostyles may be equal in length or alternating (reported length compared to body width excluding parapodial lobes). Appendages may be cylindrical, thick and swollen, slightly flattened or flattened.
Parapodial lobes medium to large in size, rounded, in some taxa with dorsal part prolonged. All chaetae, except bayonet chaetae, compound with bidentate blades; blade serration present. Compounds with small or large distal tooth. Single thin bayonet chaetae, subdistally denticulated.
Pharynx with single to multiple sinuations anterior and lateral to proventricle. Trepan with various types of denticulation, arranged in 1 ring. Basal ring absent, or present, variously developed; infradental spines absent or present. Proventricle with varying number of rows of square shaped muscle cells. Pygidium with 2 cirri (reported length compared to body width, excluding parapodial lobes, at level of proventricle, if not otherwise stated), median papilla absent.
Epitokes.
Male. Body divided into 3 regions, anterior with 2–4 (usually 3) uniramous chaetigers (region a), median with 14–24 biramous chaetigers (region b), and posterior with 0–8 uniramous chaetigers (region c). Body widest in anteromedian half of region b; body width measured in region a, as body width excluding parapodial lobes, and in region b, at the widest part, as body width including parapodial lobes. Ciliation as in stock, 1 or 2 trochs per segment.
Prostomium rounded rectangular, wider than long, with straight or concave anterior margin. Eyes large, 2 pairs, with lenses; eyes situated on dorsal and ventral side of prostomium, ventral pair larger. Palps absent. Nuchal epaulettes extending maximally to anterior part of chaetiger 1.
Large median antenna inserted on posterior part of prostomium, lateral antennae inserted on anterior margin. Lateral antennae bifid, basal part 1/6–1/2 of total length; outer ventral rami equal to or up to 5 times longer than inner dorsal rami. Basal part and inner dorsal rami segmented with abundant cilia. Pair of small frontal processes inserted anterolaterally to dorsal pair of eyes. Pair of small processes may be present ventral to lateral antennae, proximal to ventral pair of eyes. Tentacular cirri 1 or 2 pairs. First dorsal cirri (corresponding to "tentacular cirri" (e.g. Gidholm 1967) or "lateral horns" (Hamond 1974) in earlier literature, equal in shape and size to median antenna; achaetous knobs absent. Second dorsal cirri situated above first chaetigerous lobes (referred to as cirri on chaetiger 1 to avoid confusion). Cirri length measured as body width excluding parapodial lobes in region a and c; as body width including parapodial lobes in region b. Median antenna with large ceratophore, small cirrophores absent or present on tentacular cirri, mostly too small to be adequately assessed, cirrophores absent or present on dorsal cirri. Appendages may be cylindrical, fusiform, thick, slightly flattened, flattened, or club shaped.
Parapodia in region a and c as in stock but generally smaller; in region b large, flattened and equipped with well­developed notopodia. Single neuropodial acicula; notopodia in region b supported by 2 anterodorsal aciculae, and 2–3 thick and 3 thin posteroventral aciculae. Neuropodial chaetae as in stock. Notopodial lobes with 15–30 swimming chaetae, in length equal to c. body width in region b including parapodial lobes. Pygidium with 2 cirri (reported length compared to body width in region a, excluding parapodial lobes, if not otherwise stated).
Female. Body divided into 3 regions, anterior with 2–6 uniramous chaetigers (region a), median with 14–23 biramous chaetigers (region b), and posterior with 2–15 uniramous chaetigers (region c). Body width fairly constant, slightly wider in region b; body width measured in region a, as body width excluding parapodial lobes, and in region b as body width including parapodial lobes. Ciliation as in stock, 1 or 2 trochs per segment.
Prostomium rounded rectangular, wider than long, anterior margin straight or concave. Eyes large, 2 pairs, with lenses; eyes situated on dorsal and ventral side of prostomium, ventral pair larger. Palps absent. Nuchal epaulettes maximally extending to anterior part of chaetiger 1.
Median antenna inserted medially on prostomium, lateral antennae inserted on anterior margin. Tentacular cirri 1 or 2 pairs. First dorsal cirri situated above first chaetigerous lobes; achaetous knobs absent. Cirri length measured as body width excluding parapodial lobes in region a, and c; as body width including parapodial lobes in region b. Small cirrophores absent or present on tentacular cirri, mostly too small to be adequately assessed, cirrophores absent or present on dorsal cirri. Appendages may be cylindrical, fusiform, thick, slightly flattened, flattened, or club shaped.
Parapodia in region a and c as in stock but generally smaller; in region b with notopodia, not as developed as in male. Single neuropodial acicula; notopodia in region b supported by 2 anterodorsal aciculae, and 2 thick and 2–3 thin posteroventral aciculae. Neuropodial chaetae as in stock. Notopodial lobes with 15–20 swimming chaetae, in length equal to c. 1.5 times body width in region b, including parapodial lobes. Pygidium with 2 cirri (reported length compared to body width in region a, excluding parapodial lobes, if not otherwise stated).
Myrianida arborea (Westheide, 1974) comb. n. (Fig. 55A–C)
Autolytus arboreus Westheide, 1974: 319 –320, figure 59A–F.
Material examined. Galápagos: holotype ZMH P­ 13620 and 1 paratype SMF 10664, Santa Cruz, Bahía Academy, northern side, intertidal, under stones, Jul 1972.
Diagnosis. Myrianida with c. 18 equal teeth, equal cirri with equal cirrostyles and cirrophores.
Description. Holotype is a rear fragment, description is based on the paratype. Paratype incomplete, length 1.5 mm for 22 chaetigers, width 0.1 mm. Preserved material without colour markings. Ciliation not possible to assess.
Eyes separated; eye spots absent. Palps in dorsal view projecting 1/5 of prostomial length, fused. Extension of nuchal epaulettes to half of chaetiger 1.
Median antenna reaching c. chaetiger 8. Lateral antennae and dorsal tentacular cirri, length 1/2 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 following dorsal cirri. Alternation in direction of cirri not assessed. Dorsal cirri from chaetiger 3, of equal length, 1/3 of body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores and cirrostyles equal; cirrophores much shorter than parapodial lobes; cirrophores shorter than cirrostyles. All appendages cylindrical.
Parapodial lobes rounded, of medium size. Single acicula in all chaetigers. Chaetal fascicle with 5–6 compounds in all chaetigers. Compound chaetae with small distal tooth; serration present. Single thin bayonet chaetae present in all chaetigers.
Pharynx with 1 sinuation anterior to proventricle. Trepan in chaetiger 3–4, with c. 18 equal teeth, arranged in 1 ring (Fig. 55A). Basal ring moderately to well developed; infradental spines present (Fig. 55B). Proventricle equal in length to 1.5 segments (Fig. 55C) in chaetiger 7–8 with c. 20 rows of muscle cells. Pygidium (holotype) has lost its cirri.
Reproduction. Unknown
Habitat. Intertidal, under stones.
Distribution. Central East Pacific. Galápagos. Only known from type locality.
Remarks. Myrianida arborea is poorly known, it is similar if not identical to M. brevipes described from Salvador. Myrianida arborea is also very similar to M. edwarsi (Saint­ Joseph, 1887) but differs in that it lacks the orange colour along the sides in the pharyngeal region found in M. edwarsi; the trepan has generally more teeth in M. edwarsi (24–34), compared to c. 18 but variation is not adequately known in M. arborea.
Myrianida australiensis (Hartmann­Schröder, 1982) comb. n. (Fig. 56A–E)
Autolytus prolifer australiensis Hartmann­Schröder, 1982: 75 –76, figs 73–75; 1983: 136; 1989: 33; 1990: 57; 1991: 43.
Autolytus devaneyi Hartmann­Schröder, 1992b: 62, figs 26–29.
Material examined. Australia: holotype ZMH P­ 16779, 1 paratype ZMH P­ 16780, Cape Naturaliste, Eagle bay, tidal flats, algae with sand, 7 Nov 1975; French Polynesia: holotype of Autolytus devaneyi ZMH P­ 20703, Rangiroa, lagoon, calcareous algae with sand, 7 Sep 1982.
Diagnosis. Myrianida with extension of nuchal epaulettes to end of chaetiger 3; 16–18 equal teeth in trepan, thin distinct basal ring; short equal cirrophores and alternating cirrostyles.
Description. Length 1.7–2 mm for 31–45 chaetigers, width 0.2 mm. Preserved material whitish, no colour markings. Ciliation not possible to assess.
Eyes separated (Fig. 56B); eye spots present. Palps in dorsal view projecting 1/4–1/3 of prostomial length (Fig. 56A), fused. Extension of nuchal epaulettes to end of chaetiger 3 (Fig. 56B).
Median antenna lost. Lateral antennae reaching chaetiger 7–9. Tentacular cirri and first dorsal cirri lost. Cirri on chaetiger 2 equal in length to body width. From chaetiger 1– 27 cirri with usual alternation in direction, more posterior difficult to assess. Dorsal cirri from chaetiger 3 alternate in length; short cirri equals 1/2 of body width, long cirri equals 3/4 of body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores equal, cirrostyles unequal; short cirrostyles c. 2/ 3 in length of long cirrostyles; cirrophores shorter than parapodial lobes; cirrophores shorter than cirrostyles. Appendages cylindrical, including lost median antenna (Hartmann­Schröder 1982).
Parapodial lobes rounded, of medium size. Single acicula in all chaetigers. Chaetal fascicle with 5–7 compounds in all chaetigers. Compound chaetae with small distal tooth; serration present (Fig. 56E). Single thin bayonet chaetae (Fig. 56D), beginning at chaetiger 4.
Pharynx with from one to several sinuations anterior and lateral to anterior half of proventricle (Fig. 56A). Trepan in chaetiger 1 (Fig. 56B), with 16–18 equal teeth (Fig. 56C), arranged in 1 ring. Thin distinct basal ring; infradental spines present (Fig. 56C). Proventricle equal in length to 3–5 segments in chaetiger 8–13 (Fig. 56A) with 25–27 rows of muscle cells. Anal cirri lost.
Reproduction and morphology of epitokous stage. Schizogamy. The holotype of Autolytus devaneyi has 4 regenerating posterior chaetigers (Fig. 56A) that possibly represent a developing stolon. Hartmann­Schröder briefly describes stolons that she refers to Myrianida australiensis. Male stolons with (2–3)+(13–15)+0 chaetigers, for 1.13 mm, female stolons with 25 chaetigers, swimming chaetae in posterior chaetigers only (possibly immature).
Habitat. Amongst algae, in intertidal zone.
Distribution. East Indian Ocean, South Pacific. West and east Australia, French Polynesia.
Remarks. Myrianida australiensis was originally described as a subspecies of Autolytus prolifer, and was later re­described as A. devaneyi by the same author. The reason for this was probably due to that Myrianida australiensis wrongly was interpreted as having 10 teeth, and nuchal epaulettes reaching end of chaetiger 1. Myrianida australiensis is most similar to M. brevicirrata (Winternitz, 1936) with which it shares the thin basal ring, and combination of equal cirrophores and unequal cirrostyles. However M. australiensis has longer nuchal epaulettes reaching end of chaetiger 3 compared with end of chaetiger 1 in M. brevicirrata, and has only 16–18 teeth compared with 26–30 in M. brevicirrata; in addition M. australiensis has shorter cirrophores than M. brevicirrata.
Myrianida brachycephala (Marenzeller, 1874) comb. n. (Fig. 57A–E)
Proceraea brachycephala Marenzeller, 1874: 54 –56, pl. 6, fig. 2, 2A–, pl. 7, fig. 2, 2A–B.
Proceraea luxurians Marenzeller, 1874: 50 –54, pl. 6, fig. 1, 1A–D, pl. 7, fig. 1.
Autolytus mirabilis Verrill, 1882: 367 –368; 1884: 662; Hartman 1944: pl. 13, fig. 8–10.
Autolytus punctatus Saint­Joseph, 1887: 233 –234, pl. 11 fig. 108–109; Fauvel 1923: 318, fig. 122L–M.
Autolytus ehbiensis in part Saint­Joseph, 1887: 228 –233.
Autolytus brachycephalus Fauvel 1923 (in part): 316–317, fig 121G–H; Gidholm 1963; 1965; 1967: 182, 188–191, figs 7B, 13A–B, 14B, 15, 19A, 20; Hamond 1967: 1 –4, fig. 5A–B; 1969a; 1969c; Hartmann– Schröder 1971: 175 –176; Hamond 1974; Schiedges 1979a; 1979b; 1980; San Martín & Alvarado 1981: 223 –224, fig. 2; Kirkegaard 1992: 224 –225, fig 108A–B; Hartmann­Schröder 1996: 181; San Martín 2003: 500 –502: fig. 277A–D; Nygren & Sundberg 2003: GenBank sequences, 16S rDNA partial sequence AF474250, and 18S rDNA partial sequence AF474296.
Autolytus aurantiacus Korringa 1951: 79 –84, figs 8A(a–d), 8B(e–f).
Autolytus benazzi Cognetti, 1953b: 89, fig. 1; 1957: 70–71, fig. 14A–B.
Material examined. Italy: 2 syntypes of Proceraea brachycephala on 1 slide, NHMW 2501, Adriatic Sea, 1872; 2 syntypes of P. luxurians on slides, NHMW 2504, Adriatic Sea, 1875. USA: 19 syntypes of A. mirabilis, USNM 10012. Vineyard Sound, 4.75–6 fmns, 18 Aug 1882; 32 female stolons, 1 male stolon YPM 2719, Woods Hole, Massachusetts, surface, 5 Aug 1882. Faroes: 18 spms (13 spms in formalin, 5 spms on slides (2 rear ends in author's collection for DNA analyses)), East of Bordøy, 62°04.6'N 06°26.3'W, triangle dredge, 65–68 m, shellgravel with hydroids, 4 Jul 1997; 6 spms (1 spm in formalin, 4 spms on slide (rear ends in author's collection for DNA analyses), 1 spm in author's collection for DNA analyses), East of Nolsøy, 62°01.5'N 06°31.9'W, triangle dredge, 41 m, bedrock, 27 Jul 1997; 1 spm on slide (rear end preserved for DNA), East of Bordøy, 62°08.4'N 06°23.4'W, triangle dredge, 77 m, shellgravel with hydroids, 4 Jul 1997. Wales: 2 spms on slides (rear ends in author's collection for DNA analyses), Black Point, 53°18.8'N 04°2.4'W, intertidal, algae with epifauna, May 2000. France: 5 syntypes of Autolytus ehbiensis MNHN 1043, 1046, 1050, 1051, 1052, 1054, Dinard, Jul–Aug 1877– 1882; 2 spms on slides (rear ends in author's collection for DNA analyses), Banyuls­sur­ Mer, 42°29.6'N 03°10.2'E, epibenthic sledge, 59–62 m, tunicates and shells with epifauna, 26 Apr 2001. Norway: 3 spms (2 spms in formalin, 1 spm on slide (rear ends in author's collection for DNA analyses)), 63°28.4'N 10°00.0'E, 280– 230 m, gravel, 28 Jan 2002. Sweden: 11 spms (5 spms in formalin, 6 spms on slide (rear ends in author's collection for DNA analyses)), Gullmarsfjorden, Lökarna, 58°13.6'N 11° 24.8E, dredge, 32–36 m, shells and stone with hydroids, 19 Nov 1997.
Diagnosis. Myrianida with characteristic trepan with 22–29 unequal teeth, 1 large alternating with 1–3 smaller; thick basal ring; long alternating dorsal cirri with unequal cirrophores and cirrostyles.
Description. Length 3.8–8.9 mm for 30–70 chaetigers, width 0.25–0.44 mm. Live specimens uncoloured to faintly yellowish­orange (Fig. 57A–B), intestinal region often with scattered white specks from intestinal granular accumulations; tips of anterior appendages often reddish; eyes orange­red. Ciliation as 1 troch per segment.
Eyes separated (Fig. 57A); eye spots present. Palps in dorsal view projecting 1/3–1/2 of prostomial length (Fig. 57A), fused. Extension of nuchal epaulettes to between end of chaetiger 1 and end of chaetiger 2 (Fig. 57A).
Median antenna reaching chaetiger 9–16 (n=19). 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 (Fig. 57A, B), followed by 2–6 DDUU­groups, and a varying number of DDU­, DUU­, and DMU­groups (n=17). Dorsal cirri from chaetiger 3 alternate in length; short cirri equals 2/3–3/4 of body width, long cirri equal to or slightly longer than body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores and cirrostyles unequal; cirrophores and cirrostyles on short cirri 2/ 3 in length of its counterpart in long cirri; cirrophores on short cirri equal to or slightly longer than parapodial lobes, cirrophores on long cirri longer than parapodial lobes; cirrophores shorter than cirrostyles. All appendages cylindrical (Fig. 57B).
Parapodial lobes rounded, medium to large in size. Anterior chaetigers with 2–3 aciculae, 1 in median and posterior. Chaetal fascicle with 10–15 compounds in anterior chaetigers, 4–9 in median and posterior. Compound chaetae with small distal tooth; serration present (Fig. 57D). Single thin bayonet chaetae (Fig. 57E), beginning at chaetiger 6–20.
Pharynx with sinuation anterior to proventricle (Fig. 57A). Trepan in chaetiger 2–4, with 22–29 unequal teeth; 8 (n=1), 9 (n=11) or 10 (n=2) large and 14–21 smaller; 1 large alternating with 1–3 smaller, arranged in 1 ring (Fig. 57C). Basal ring present; infradental spines present (Fig. 57C). Proventricle equal in length to 3–4.5 segments in chaetiger 8–14 with 30–39 rows of muscle cells (n=21). Anal cirri equal in length to 1–1.5 times body width.
Reproduction. Schizogamous reproduction by gemmiparity behind chaetiger 34–88.
Stolon­bearing specimens observed from June to October, but not in January and May, in Scandinavian waters (Gidholm 1967). Free­swimming stolons occur in plankton from April to November in the Atlantic (Hamond 1974).
Morphology of epitokous stages.
Male. Length in preserved specimens 3.4–3.7 mm for 3+(23–24)+0 chaetigers (n=3), width in region a 0.2 mm, width in region b 0.6 mm. Live specimens faintly greenish, without colour markings. Ciliation as in stock.
Prostomium with concave anterior margin. Nuchal epaulettes rounded, extending to beginning of chaetiger 1.
Median antenna reaching middle of region b (chaetiger 10–12). Lateral bifid antennae, 2–3 times as long as prostomial width; basal part 1/2 of total length, rami of about equal size. Frontal processes, equal to 1/3 of prostomial width. Tentacular cirri 1 pair, as long as prostomial width. First dorsal cirri, equal in length to median antenna; achaetous knobs absent. Cirri on chaetiger 1 equal to body width, cirri on chaetiger 2 and 3 shorter, equal to 3/4 of body width. Cirri in region b shorter than in a, reciprocally equal, measuring c. 1/4 of body width. Median ceratophore, small cirrophores on tentacular cirri, large cirrophores on first dorsal cirri, and short cirrophores in region a, present; cirrophores otherwise absent. Cirri in region a cylindrical to fusiform, cirri in region b fusiform, frontal processes slightly club shaped, other appendages cylindrical.
Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 2 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 3–8 compounds; single thin bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with 15–20 swimming chaetae. Anal cirri equal in length to 1–2 times body width.
Female. Based on female stolons of Autolytus mirabilis. Length in preserved specimen c. 3 mm for 2+(15–18)+(0–2) chaetigers (n=18), width in region a 0.3 mm, width in region b 0.7 mm.
Prostomium with concave anterior margin. Nuchal epaulettes rounded–triangular, reaching beginning of chaetiger 1.
Median antenna reaching chaetiger 3. Lateral antennae, 2/ 3 in length of median antenna. Tentacular cirri 1 or 2 pairs. First dorsal cirri, about equal in length to following dorsal cirri, situated above first chaetigerous lobe. Achaetous knobs absent. Cirri in region a equal to body width; cirri in region b slightly longer than in a; cirri in region c tapering towards the posterior end. Cirrophores present on all dorsal cirri, equal in length to parapodial lobes in region a; tentacular cirrophores not possible to detect. All appendages cylindrical.
Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 3 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 4–5 compounds; single bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with c. 15 swimming chaetae. Anal cirri lost.
Habitat. From low intertidal, but mostly subtidal. Amongst hydroids, bryozans, and tunicates. Fed successfully in laboratory experiments with Laomedea dichotoma var. plana, L. gelatinosa, and L. loveni (Hamond 1969c).
Distribution. North Atlantic, Mediterranean.
Remarks. Myrianida brachycephala differs from other similar species in the denticulation of the trepan. Other diagnostic characters are the length of the cirrophores relative to the cirrostyles; cirrophores on long cirri are shorter than corresponding cirrostyles, contrasting with M. langerhansi (Gidholm, 1967) whose long cirri have longer cirrophores than cirrostyles. Hamond (1969a) and Schiedges (1979a, 1979b, 1980) discussed the possibility that Myrianida brachycephala, M. prolifera, and M. edwarsi hybridize in Norfolk waters, east of Great Britain, and in Oosterschelde estuary on the coast of the Netherlands. No indication of this has been noted, from molecular or morphological data in the sampled areas, but specimens from Norfolk and Oosterschelde have not been sampled and the matter needs further investigation. At present the species are regarded as different lineages. The suggested synonymies of Proceraea luxurians, and A. mirabilis are based on examination of the type material, whereas the synonymy of Autolytus punctatus and Autolytus benazzi are based on the descriptions, for the latter this is concluded mainly from the figure. In his description Cognetti states that there are 24 equal teeth, but in the figure the teeth are of different sizes; otherwise the description fits well with M. brachycephala. The fact that M. brachycephala is common in the Mediterranean, and that Cognetti did not record it, reinforces the synonymy. Saint­Joseph's description of Autolytus ehbiensis refers to M. prolifera at least what regards the trepan structure, but several of the syntypes marked with A. ehbiensis are in fact M. brachycephala. Fauvel's (1923) description seems to be based on a mixture of specimens of A. langerhansi and A. brachycephalus.
Myrianida brevicirrata (Winternitz, 1936) comb. n. (Fig. 58A–F)
Autolytus brevicirrata Winternitz, 1936: 1, figs 1, 2; Hartman 1951: 42.
Material examined. USA: holotype AMNH 2271, Florida, Appalachicola, 17 Sep 1935.
Diagnosis. Myrianida with long equal cirrophores, and alternating cirrostyles; trepan with 26–30 equal teeth, and a thin basal ring.
Description. Holotype is a budding specimen with two developing stolons (Fig. 58A), incomplete, length of stock 2.2 mm for 23 chaetigers, width 0.2 mm. Preserved material yellowish brown, no colour markings. Ciliation not possible to assess.
Eyes separated; eye spots present. Palps in dorsal view projecting c. 1/3 of prostomial length (Fig. 58A). Extension of nuchal epaulettes to end of chaetiger 1.
Anterior appendages and most dorsal cirri lost. Alternation in direction of cirri not assessed. Dorsal cirri from chaetiger 3, alternate in length; short cirri slightly shorter than 1/2 body width, long cirri slightly longer than 1/2 body width. Cirrophores on tentacular segment and all dorsal cirri present. Cirrophores equal, cirrostyles unequal (Fig. 58B, C); short cirrostyles 2/ 3 in length of long cirrostyles; cirrophores longer than parapodial lobes; cirrophores on short cirri longer than cirrostyles (Fig. 58B), cirrophores on long cirri equal in size to cirrostyles (Fig. 58C). Appendages cylindrical, including lost lateral antennae and tentacular cirri (Winternitz 1936).
Parapodial lobes rounded, of medium size. Anterior chaetigers with 2–3 aciculae, 1 in median and posterior. Chaetal fascicle with 10–12 compounds in anterior chaetigers, 5–8 in median and posterior. Compound chaetae with small distal tooth; serration present (Fig. 58E). Single thin bayonet chaetae (Fig. 58F), beginning at chaetiger 1.
Pharynx with sinuation anterior and lateral to anterior half of proventricle. Trepan in chaetiger 2 with 26–30 equal teeth (Fig. 58D). Basal ring thin, distinct; small infradental spines present (Fig. 58D). Proventricle equal in length to 3 segments in chaetiger 5–8, with 28–30 rows of muscle cells.
Reproduction. Schizogamous reproduction by gemmiparity behind chaetiger 23.
Habitat. Unknown.
Distribution. North West Atlantic. Florida, Appalachicola.
Remarks. Myrianida brevicirrata is unique in its long equal cirrophores; it is perhaps most similar to M. australiensis (see remarks for M. australiensis). Winternitz described the compound chaetae as unidentate; this is not correct, all compounds are bidentate.
Myrianida brevipes (Hartmann­Schröder, 1959) comb. n. (Fig. 59A–C)
Odontosyllis brevipes Hartmann­Schröder, 1959: 123 –125, figs 70–74.
Material examined. Salvador: holotype ZMH P­ 14751, La Herradura (Estero Jaltepeque).
Diagnosis. Myrianida with short equal cirri, with equal cirrophores and equal cirrostyles; trepan with 20–25 equal teeth.
Description. Holotype incomplete, length 0.6 mm for 9 segments, width 0.15 mm. Preserved material brownish, no colour markings. Body ciliation as 1 intrasegmental band per segment.
Eyes separated; eye spots absent. Palps in dorsal view projecting 1/4–1/3 of prostomium length, fused. Extension of nuchal epaulettes to end of tentacular segment.
Median antenna reaching chaetiger 5. Lateral antennae and first dorsal cirri, length 1/2 of median antenna. Dorsal tentacular cirri, length 2/3 of lateral antennae. Ventral tentacular cirri 1/2 as long as dorsal pair. Alternation in direction of cirri not assessed. Cirri from chaetiger 2 of equal length (Fig. 59A), 1/2 of body width. Cirrophores present on tentacular cirri and all dorsal cirri. Cirrophores and cirrostyles equal; cirrophores shorter than parapodial lobes, cirrophores shorter than cirrostyles. All appendages cylindrical.
Parapodial lobes rounded, of medium size. All chaetigers with 1–2 aciculae. Chaetal fascicle with c. 10 compound chaetae. Compound chaetae with small distal tooth; serration present (Fig. 59B). Single thin bayonet chaetae (Fig. 59C), beginning at chaetiger 3.
Pharynx with short sinuation anterior to the proventricle. Trepan in chaetiger 1, with 20–25 equal teeth, difficult to assess. Basal ring present (uncertain observation), infradental spines may be present, difficult to assess. Proventricle equal in length to 2 segments in chaetiger 4–5 with c. 23 rows of muscle cells. Posterior part lost.
Reproduction. Unknown.
Habitat. Algae with sand.
Distribution. Central East Pacific, Salvador. Only known from type specimen.
Remarks. See remarks for Myrianida arborea.
Myrianida convoluta (Cognetti, 1953) comb. n. (Fig. 60A–D)
Autolytus convolutus Cognetti, 1953a: 323 –332, figs 1–12; 1957: 71–72, fig. 15A–B; Ben­Eliahu 1972: 217 –218, fig. 14A–D; Amaral & Nonato 1975: 235 –236; Ben­Eliahu 1977: 85 –86, fig. 12; San Martín 1994: 271; 2003: 483–486, figs 265A–E, 266A–D; Nygren & Sundberg 2003: GenBank sequences, 16S rDNA partial sequence AF474257, and 18S rDNA partial sequence AF474303.
Autolytus (Regulatus) convolutus Imajima 1966: 47 –49, fig. 12A–H.
Material examined. Spain: 1 spm on slide (rear end in author's collection for DNA analyses), El Cabo de Trafalgar, 36°11'N 6°01'W, dive, 5 m, algae with epifauna, sponges, hydroids, Nov 2000. USA: 6 spms (4 spms in formalin, 2 spms on slides (rear ends in author's collection for DNA analyses)), California, Santa Catalina Island, Bird Rock, 33°26' N 118°29'W, 20m, dive, Laminaria with hydroids, 17 Jan 2001.
Diagnosis. Myrianida with much convoluted pharynx; trepan with 9 or 15–16 equal triangular teeth, and a thin basal ring.
Description. Length 1.7–2.6 mm for 22 stock chaetigers, length including stolons 3.2– 5.9 mm; width 0.15–0.20 mm. Live specimens uncoloured to faintly yellowish, intestinal region yellowish with white specks from intestinal granular accumulations (Fig. 60A), small orange glands present across each segment, especially in cirrophores; eyes red. Ciliation as 1 troch per segment.
Eyes separated; eye spots present. Palps do not project in front of prostomium (Fig. 60B), fused. Extension of nuchal epaulettes to between end of chaetiger 1 and end of chaetiger 2 (Fig. 60B).
Median antenna reaching chaetiger 6–8 (n=2). Lateral antennae and dorsal tentacular cirri, length 1/2–2/3 of median antenna. Ventral tentacular cirri 1/3–1/2 as long as dorsal pair. First dorsal cirri as long as median antenna, second dorsal cirri as long as following dorsal cirri (Fig. 60B). Alternation in direction of cirri not assessed. Dorsal cirri from chaetiger 3, of equal length (Fig. 60B), c. 1/2 of body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores and cirrostyles equal; cirrophores shorter than parapodial lobes; cirrophores shorter than cirrostyles. All appendages cylindrical (Fig. 60A, B).
Parapodial lobes rounded, of medium size. Single acicula in all chaetigers. Chaetal fascicle with 5–7 compounds in anterior chaetigers, 2–6 in median and posterior. Compound chaetae with small distal tooth; serration present. Single thin bayonet chaetae, beginning between chaetiger 1–15.
Pharynx with many sinuations anterior to proventricle (Fig. 60B). Trepan in chaetiger 1–2, with 9 or 15–16 equal teeth, in 1 ring (Fig. 60C). Thin basal ring present; infradental spines present (Fig. 60C). Proventricle equal in length to 1.5–2.5 segments (Fig. 60B) in chaetiger 7–12 with 19–21 rows of muscle cells (n=4). Anal cirri equal in length to body width.
Reproduction. Schizogamous reproduction by gemmiparity behind chaetiger 22. Stolon­bearing specimens occur all year round but mostly in May to January (Cognetti 1957).
Morphology of epitokous stages.
Male. Length in preserved specimen 1.8 mm for 3+14+0 chaetigers (n=1), width in region a 0.15 mm, width in region b 0.3 mm. Live specimens faintly greenish, without colour markings (Fig. 60D). Ciliation as in stock.
Prostomium without straight anterior margin. Nuchal epaulettes rounded, extending to beginning of chaetiger 1.
Median antenna reaching middle of region b, c. chaetiger 8. Lateral bifid antennae, 3 times as long as prostomial width; basal part 1/5 of total length, outer ventral rami 4–5 times longer than inner dorsal rami (Fig. 60D). Frontal processes, equal to 1/5 of prostomial width. Tentacular cirri 1 pair (Fig. 60D), as long as 1–1.5 times prostomial width. First dorsal cirri, 2/3 as long as median antenna. Achaetous knobs absent. Cirri in region a slightly longer or equal in length to body width, cirri on chaetiger 1 slightly longer than cirri on chaetiger 2 and 3; cirri in region b shorter than in a, reciprocally equal, measuring 1/4 of body width. Median ceratophore, small tentacular cirrophores, large cirrophores on first long cirri, short cirrophores on cirri in region a, present; cirrophores otherwise absent. All appendages cylindrical (Fig. 60D).
Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 3 thin, posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 5–10 compounds; single thin bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with c. 15 swimming chaetae. Anal cirri equal in length to 2 times body width.
Female. No fully developed stolons examined.
Habitat. Intertidal and subtidal, amongst hydroids, bryozans, and tunicates.
Distribution. North Atlantic, Mediterranean, North Pacific.
Remarks. Myrianida convoluta is characterized by its convoluted pharynx, equal cirri with small equal cirrophores, and trepan with 9 or 15–16 equal teeth on a thin basal ring. Molecular analyses as well as morphological data suggest a close relationship with M. hesperidium (Claparède, 1868) and M. quindecimdentata (Langerhans, 1884). The pharynx is not as convoluted in either of these species as in M. convoluta.
Myrianida dentalia (Imajima 1966) comb. n. (Fig. 61A–E) Autolytus (Autolytus) dentalius Imajima, 1966: 36 –37, fig. 7:I–L.
Autolytus dentalius Gardiner 1976: 127, fig. 10A– D. Uebelacker 1984: 30 –12, fig. 30–4:A–D;? San Martín 2003: 505 –507, figs 280A–E, 281A–D; Nygren & Sundberg 2003: GenBank sequences, 16S rDNA partial sequence AF474255 and 18S rDNA partial sequence AF474301.
Material examined. Japan: holotype NSMT­Pol H­ 55, Urago Strait, 7 Jan 1959. USA: 8 spms, North Carolina, Beaufort, 35°43'N 35°42'W, various localities, 5–30 m, gravel with epifauna, Sept–Nov, 1970; 15 spms (5 spms in formalin, 10 spms on slides (9 rear ends in author's collection for DNA analyses)), Washington, between Rock point and López Island, 48°29.61'N 122°02.53'W, dredge, 70 m, Polycarpa, sponges, with rich hydroid fauna, 24 Jan 2001.
Diagnosis. Myrianida with characteristic trepan shared only with M. rangiroaensis (Hartmann­Schröder, 1992); 2 large teeth laterally positioned with 9–11 dorsal teeth, and 16–19 ventral teeth; dorsal teeth smaller than ventral; large teeth fused with adjacent teeth; unequal cirri with unequal cirrophores and equal cirrostyles.
Description. Length in preserved specimens 5.2–9 mm for 42–80 chaetigers, width 0.35–0,45 mm. Live specimens weekly pink anteriorly, proventricle pinkish, intestinal region yellowish (Fig. 61A, B); eyes red. Ciliation as 1 troch per segment.
Eyes confluent (Fig. 61A); eye spots present. Palps in dorsal view projecting 1/3–1/2 of prostomial length (Fig. 61A), fused. Extension of nuchal epaulettes to between end of chaetiger 3 and end of chaetiger 4 (beginning of chaetiger 5 in holotype).
Median antenna reaching chaetiger 9–13 (n=4) in preserved specimens. Lateral antennae and dorsal tentacular cirri, length 1/2 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 4 DDUU­groups, and 7–15 DDU­groups (n=8). Dorsal cirri from chaetiger 3 alternate in length; short cirri equals 2/3–3/4 of body width, long cirri equal to or slightly longer than body width. Cirrophores present on tentacular cirri, and all dorsal cirri. Cirrophores unequal, cirrostyles equal (Fig. 61A); cirrophores on short cirri 1/ 2 in length of cirrophores on long cirri (Fig. 61A); cirrophores on short cirri equal to parapodial lobes, cirrophores on long cirri longer than parapodial lobes; cirrophores on short cirri equal in length to cirrostyles, cirrophores on long cirri longer than cirrostyles (Fig. 61A). All appendages cylindrical.
Parapodial lobes rounded, of medium–large size. Anterior chaetigers with 2–3 aciculae, 1 in median and posterior. Chaetal fascicle with 10–13 compounds in anterior chaetigers, 4–9 in median and posterior. Compound chaetae with small distal tooth; serration present. Single thin bayonet chaetae, beginning between chaetiger 40–70.
Pharynx with 1 long sinuation anterior and lateral to anterior half of proventricle (Fig. 61A). Trepan in chaetiger 3–7, with 2 large teeth and 25–38 smaller; large teeth laterally positioned with 9–11 dorsal teeth, and 16–19 ventral (n=8); dorsal teeth smaller than ventral; large teeth mostly fused with adjacent teeth; teeth arranged in 1 ring (Fig. 61C). Basal ring present; infradental spines present. Proventricle equal in length to 4–5.5 segments (Fig. 61A, B) in chaetiger 12–18 with 33–42 rows of muscle cells (n=12). Anal cirri equal in length to 1–1.5 times body width.
Reproduction. Probably with schizogamy, 2 individuals were found with pink eggs from about chaetiger 29–55; one of these had a regenerating posterior end behind chaetiger 55 (Fig. 61B).
Habitat. Subtidal, amongst hydroids, bryozans, and tunicates.
Distribution. North West Atlantic, North Pacific.
Remarks. Myrianida dentalia was originally described from one anterior end in poor condition. Thus the identity of the newly collected material as Myrianida dentalia may be problematic. It was not possible to determine the status of the cirri in the holotype, but in all other respects the new material agree well with the type. The nuchal epaulettes are slightly longer in the holotype, extending to anterior part of chaetiger 5 instead of maximally anterior part of chaetiger 4. Collecting of topotype material is necessary to solve the question. Another taxon with the same type of trepan is M. rangiroaensis from South Pacific Ocean; it differs from M. dentalia in shorter nuchal epaulettes, extending only to half of chaetiger 2, and in having relatively large eye spots in front of anterior pair of eyes. The specimens described and figured by San Martín (2003) from the Mediterranean Sea differ from the M. dentalia herein described in the length of the cirrophores. His specimens have cirrophores that do not alternate in length, and are shorter than the parapodial lobes.
Myrianida edwarsi (Saint­Joseph, 1887) comb. n. (Fig. 62A–E)
Autolytus edwarsi Saint­Joseph, 1887: 235 –237, pl. 11, fig. 110; Malaquin 1893; Southern 1914: 43; Allen 1915: 605; Fauvel 1923: 317 –318, fig. 122 A; Okada 1929a; 1929c; 1937; Gidholm 1963; 1965; 1967: 181 –186, figs 1A–C, 5B, 9, 15–17; Allen 1967; Gidholm 1969; Mattisson 1969; Rasmussen 1973: 74 –75;; Nygren & Sundberg 2003: GenBank sequences, 16S rDNA partial sequence AF474248, and 18S rDNA partial sequence AF474294.
Autolytus edwardsi Potts 1911: 31 –35, fig.11; Hamond 1967, 1–4, fig. 4; 1969a; Hartmann­ Schröder 1971: 180 –182, fig. 58A–C; Kirkegaard 1992: 226 –227, fig. 109A–C; Hartmann­ Schröder 1996: 181 –182, fig. 78A–C;? Parapar et al. 1996, 143, fig. 1C, pl. 2, fig. A–B.
Autolytus prolifer Thorson 1946: 38 –39, fig. 10.
? Autolytus edwardsii Cognetti 1957: 69 –70.
Material examined. France: 4 syntypes of Autolytus edwarsi NMNH 1057–1060, Dinard, Jul–Aug 1881–1885. Faroes: 19 spms (5 spms in formalin, 11 spms on slides (7 rear ends in author's collection for DNA analyses), 3 spms in author's collection for DNA analyses), outside Kaldbak marine laboratory, 62°'N 06°W, dive, 1–4 m, Laminaria spp. with epifauna, 21 Jun 1997. Wales: 12 spms (11 spms on slides (rear ends in author's collection for DNA analyses), 1 spm in author's collection for DNA analyses), Black Point, 53°18.8'N 04°2.4'W, intertidal, algae with epifauna, May 2000. Sweden: 8 spms in author's collection for DNA analyses, Gullmarsfjorden, Lökarna, 58°13.6'N 11° 24.8E, dredge, 32–36 m, shells and stone with hydroids, 19 Nov 1997; 30 spms in formalin, Tjärnö archipelago, Inre Vattenholmen, 58°52'N 11°06'E, intertidal, algae with epifauna, Apr 2002.
Diagnosis. Myrianida with reddish orange sides in pharyngeal region; trepan with 24– 34 equal teeth, basal ring well­developed.
Description. Length in live specimens 3.0– 8.2 mm for 22–43 stock chaetigers, length including stolons up to 13 mm, width 0.28–0.45 mm. Body sides, particularly in pharyngeal region, reddish, otherwise uncoloured to faintly yellowish­orange (Fig. 62A, B), intestinal with a more or less intense white middorsal line from intestinal granular accumulations (Fig. 62A); tips of anterior appendages often reddish; eyes red. Ciliation as 1 troch per segment.
Eyes separated; eye spots present (Fig. 62B). Palps in dorsal view projecting 1/3 of prostomial length (Fig. 62B), fused. Extension of nuchal epaulettes to between beginning of chaetiger 1 and beginning of chaetiger 2 (Fig. 62B).
Median antenna reaching chaetiger 7–11 (n=12) in live specimens. Lateral antennae and dorsal tentacular cirri, length 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 1–1.5 times the ventral tentacular cirri. From chaetiger 1–27 cirri with usual alternation in direction followed by 1–3 DDUU­groups, and 1–4 DDU­groups (n=10). Dorsal cirri from chaetiger 3, of subequal length (Fig. 62A), 1/2–2/3 of body width. Cirrophores present on tentacular cirri and all dorsal cirri. Cirrophores and cirrostyles equal; cirrophores slightly shorter, or equal to parapodial lobes; cirrophores shorter than cirrostyles. All appendages cylindrical (Fig. 62A).
Parapodial lobes rounded, of medium–large size. Anterior chaetigers with 2–3 aciculae, 1–2 in median and posterior. Chaetal fascicle with 10–19 compounds in anterior chaetigers, 4–12 in median and posterior. Compound chaetae with small distal tooth; serration present. Single thin bayonet chaetae, beginning between chaetiger 1–22.
Pharynx with sinuation anterior to proventricle. Trepan in chaetiger 1–3, with 24–34 equal teeth, arranged in 1 ring (Fig. 62E). Basal ring present; infradental spines present (Fig. 62E). Proventricle equal in length to 2–2.5 segments in chaetiger 6–10 with 23–31 rows of muscle cells (n=16). Anal cirri equal in length to 1–2 times body width.
Reproduction. Schizogamous reproduction by gemmiparity (Fig. 62A, C, D) behind chaetiger 24–45. Individuals producing stolons found from April to December (Gidholm 1967).
Morphology of epitokous stages.
Male. Length in preserved specimens 2.8–3.6 mm for 3+(18–25)+0 chaetigers (n=5), width in region a 0.3 mm, width in region b 0.5–0.6 mm. Live specimens faintly greenish with a white middorsal line from intestinal granular accumulations as in stock, without colour markings. Ciliation as in stock.
Prostomium with small anterior incision. Nuchal epaulettes rounded, extending to beginning of chaetiger 1.
Median antenna reaching middle of region b, chaetiger 10–15. Lateral bifid antenna, 2–3 times as long as prostomial width; basal part 1/2 of total length, rami of about equal size. Frontal processes, equal to 1/4–1/3 of prostomial width. Tentacular cirri 1 pair, 2/3 or as long as prostomial width. First dorsal cirri, equal in length to median antenna. Achaetous knobs absent. Cirri on chaetiger 1 equals body width, cirri on chaetiger 2 and 3 shorter, equal to 3/4 of body width; cirri in region b shorter than in a, reciprocally equal, measuring c. 1/4 of body width. Median ceratophore, small tentacular cirrophores, large cirrophores on first dorsal cirri, short cirrophores in region a, present; cirrophores otherwise absent. Cirri in region a and b fusiform, frontal processes club shaped, other appendages cylindrical.
Single neuropodial acicula in all chaetigers; 2 anterodorsal, and 2 thick and 3 thin posteroventral notopodial aciculae in region b. Neuropodial chaetal fascicle with 3–8 compounds; single thin bayonet chaetae beginning at chaetiger 1. Notopodial chaetal fascicle with c. 20 swimming chaetae. Anal cirri equal in length to 2–3 times body width.
Female. No mature females examined. According to Gidholm (1967) c. 3 mm for 2+(15–18) chaetigers. Tentacular cirri 2 pairs, one egg sac.
Habitat. Mostly intertidal, amongst algae, hydroids, and bryozans. Observed to feed on Laomedea geniculata, L. flabbelata, and L. longissima (Okada 1929c; Gidholm 1967).
Distribution. North East Atlantic, Mediterranean.
Remarks. Myrianida edwarsi is close to M. prolifera, and may be very difficult to separate in preserved condition. Live specimens with orange sides in pharyngeal region and a distinct middorsal band of intestinal granular accumulations, while M. prolifera is only very faintly orange anteriorly, and the granular accumulations are scattered. Furthermore M. edwarsi has equal cirri, unequal in M. prolifera, and nuchal epaulettes reach only beginning of chaetiger 2, while they reach end of chaetiger 2 in M. prolifera. But at least for the latter character, there is overlap in variation. See also remarks for M. brachycephala.
description: Published as part of Nygren, Arne, 2004, Revision of Autolytinae (Syllidae: Polychaeta)., pp. 1-314 in Zootaxa 680 on pages 115-130, DOI: 10.5281/zenodo.157809