Myriowenia undetermined

Capa, Maria, Parapar, Julio & Hutchings, Pat, 2012, Phylogeny of Oweniidae (Polychaeta) based on morphological data and taxonomic revision of Australian fauna, Zoological Journal of the Linnean Society 166 (2), pp. 236-278 : 262-265

MYRIOWENIA SP.

FIGURES 9F–H , 12 AND 13 , TABLE 6

Material examined (Appendix 1): New South Wales (128 specs), south of Sydney: Cobblers, Wattamolla , Bass Point , Cape Banks and Marley , in sandy bottoms, 40–70 m.

Description: Largest complete specimen measuring 14 mm long and 0.8 mm wide, with 55 chaetigers. Body cylindrical in cross section ( Fig. 12A–C ), with slightly tapering posterior end. Epithelium wrinkled in head and anterior segments. No longitudinal ciliated grooves present. Nervous system evident as white ventral longitudinal band. Head region rounded, wider than rest of the body in most specimens, distinctly set off from segmented region by constriction ( Figs 9F, G , 12A–F , 13A–D ). Two anterior grooved palps similar in length to uniramous region ( Figs 12A–F , 13A–C ), with rounded anterior lobes on each base (( Figs 12E , 13A, E ). Anteroventral mouth with ventral pharyngeal organ and dorsolateral fold present and exposed in some specimens ( Fig. 13A, E ). Eyespots not observed. First three chaetigers uniramous ( Figs 12A, B , 13B ), similar in length or first one slightly longer ( Figs 12A, B , 13B ); biramous segments also similar in length ( Fig. 12A–C ) to posterior end, becoming progressively shorter and thinner ( Figs 12H, I , 13M ). Notopodia with capillaries ( Fig. 12G ) with proximal end smooth and distal end with scale covering ( Fig. 13F ); diminishing in length ventrally within each fascicle. Acicular chaetae absent. Neuropodial tori narrow, with uncini arranged in two to three irregular rows in anterior and middle segments ( Fig. 13G ) to one short row consisting of one or two uncini in posterior segments ( Fig. 13L ). Uncini with two curved teeth, arranged one above the other, distal tooth smaller than proximal one ( Fig. 13G–I ). Posterior end cylindrical, distally tapered, with compressed segments; pygidium as a rim encircling anus ( Figs 12H, I , 13M ). Tube very thin and flexible only covered by a few fine sand grains, not heavily cemented. Several specimens with posterior ends exhibiting regeneration processes at the broken posterior end of the body (( Figs 9H , 12J–K ). Colour of specimens pale yellow after preservation.

Ecological notes: Specimens found in sandy bottoms and at 40–70 m depths, in localities south of Sydney , New South Wales ( Fig. 14 ) .

Remarks: Three species of Myriowenia have been described so far, Myriow. californiensis Hartman, 1960 , from California ( Fig. 15H ), and two others from the Gulf of Mexico, Myriowenia gosnoldi Hartman, 1965 , ( Fig. 15G ) and Myriowenia sp. A Milligan, 1984 (see Table 6). Differences amongst these species have not been addressed in previous studies because in most cases insufficient material was available or its condition was not optimal to check intraspecific variation. For example, what has been interpreted as a cylindrical head in Myriow. gosnoldi and Myriowenia sp. A ( Hartman, 1965; Milligan, 1984) has also been observed in some of the specimens from New South Wales (e.g. Fig. 12D ) and could be because of the flexibility of this region, but certainly is not a diagnostic character of these species.

The presence of ‘a pair of pygidial cirri’ in Myriow. gosnoldi ( Hartman, 1965; 347: fig. 44b) resembles the regeneration processes that we have also observed in some broken fragments. Some Australian specimens of Myriowenia sp. , like other oweniids herein described, show a certain type of filamentous processes in the fragmented posterior body part. These processes resemble extensions of the body integument ( Fig. 12J, K ), resulting in a different appearance of the posterior end when compared with complete (intact) specimens, with the posterior segments being compressed and slightly thinner towards the low rim pygidium ( Fig. 12H, I ). Moreover, in some Australian specimens other processes appear to originate from the side pores of some midbody segments ( Fig. 13J, K ). The true composition of these processes and their function are unknown and deserve more investigation. The main character that separates Myriowenia sp. and Myriow. gosnoldi or Myriowenia sp. A is the absence of a collar membrane between the cephalic and the segmented region (present in both Myriow. gosnoldi and Myriowenia sp. A ). Myriowenia sp. is therefore more similar to Myriow. californiensis (sensu Hartman, 1960 and Blake, 2000), in sharing *According to Blake (2000).

†The specimen described by Hartman (1965) is probably an anterior fragment undergoing regeneration.

‡Segment 2 according to author’s description, but not from drawings ( Milligan, 1984: fig. 46-4).

nd, no data available.

the presence of short uniramous segments. However, because the pygidium and posterior segments have not been described in Myriow. californiensis , we cannot compare these two, probably disjunct, Myriowenia species in detail.

Figures

Figure 9. A–D, Myriochele heruensis in regeneration. A, anterior end regenerating, including uniramous and biramous segments. B, early stage of anterior end regeneration from a mid-body segment. C, regeneration of posterior end. D, detail of a torus with newly formed uncini at the point of piercing the cuticle (arrows). E, Myriochele australiensis sp. nov. Regeneration of posterior end. F–H, Myriowenia sp. in regeneration. F, anterior end, ventral view. G, head, ventral view. H, regeneration of anterior fragment with tubular projections (arrows). Abbreviations: b1-b4, biramous segment 1 to 4; u1-u3, uniramous segments 1 to 3. Registration numbers: A, D, AM W37182; B, AM W37179; C, AM W37181; E, AM W37201; F, G, AM W37185; H, AM W37186. Scale bars: A–C, E, G, H = 100 Mm; D = 10 Mm; F = 20 Mm.

Figure 12. Myriowenia sp. A, specimen in lateroventral view. B, specimen regenerating posterior end, ventral view. C, specimen regenerating posterior end, lateral view. D, anterior end, lateral view. E, anterior end, ventral view. F, anterior end, lateral view. G, chaetiger 5, lateroventral view. H, posterior end, lateral view. I, posterior end, ventral view. J, regeneration of posterior end, dorsal view. K, regeneration of posterior end, ventral view. Abbreviations: b1-b5: biramous segments 1 to 5; u1-u3: uniramous segments 1 to 3. Scale bars: A–D = 400 Mm; E, F = 200 Mm; G = 50 Mm; H–K = 100 Mm.

Figure 13. Myriowenia sp. A, anterior end, frontal view. B, anterior end, lateral view. C, anterior end, dorsal view. D, detail of cephalic groove (between head and first segment). E, detail of mouth opening and anterior head structures. F, notopodial capillary chaetae, segment 2. G, rows of uncini, segment 6. H, detail of uncini, segment 8, side view. I, detail of uncini, segment 6, top view. J, midbody, with parapodial tubular projection. K, detail of tubular projections. L, uncini in posterior segments. M, posterior end, lateral view. Abbreviations: al, anterior lobes; b1, biramous segment 1; dlf, dorsolateral folds; u1-u3, uniramous segments 1 to 3; vph, ventral pharyngeal organ; asterisk, asymmetrical first segment. Registration numbers: A–C, E, F, AM W37186; D, G, I, AM W37187; H, J, K, AM W37185; L, M, AM W37189. Scale bars: A–C = 200 Mm; D, J = 20 Mm; E, M = 100 Mm; F, G = 2 Mm; H, I = 1 Mm; K = 3 Mm; L = 10 Mm.

Figure 14. Distribution of Australian oweniids except for members of genus Owenia.

Figure 15. Stylized drawings of main morphological features in some representative species of Oweniidae genera (all redrawn from originals with permission). A, Galathowenia oculata. B, Myriochele heeri. C, Owenia fusiformis. D, Galathowenia oculata. E, Myriochele olgae. F, Myriochele danielsseni. G, Myriowenia gosnoldi. H, Myriowenia californiensis. I, Owenia fusiformis. J, Galathowenia oculata. K, Myriochele heeri. L, generalized drawings of disposition of the uncinal teeth in all genera. A, after Milligan (1984: 46–49, fig. 46.6a). B, after Nilsen & Holthe (1985: 20, fig. 3B). C, after Hartmann-Schröder (1996: 477). D, after Imajima & Morita (1987: 95, fig. 6). E, after Blake (2000: 112, fig. 5.5). F, after Imajima & Morita (1987: 93, fig. 5). G, after Hartman (1965: 347, fig. 44a). H, after Hartman (1960: 209, fig. 16.5). I, after Drasche (1885: plate 1, fig. 2). J, after a SEM picture in Purschke & Tzetlin (1996: 4, fig. 10B). K, after Parapar (2006: 530, fig. 7A). L, from diverse sources cited above. Abbreviations: al, anterior lobes; b1-b2, biramous segments 1 to 2; c, collar; dlf, dorsolateral folds; e, eyespots; m, mouth; ml, mouth lips; oec, oesophageal commissure; p, palps; tc, tentacular crown; u1-u3, uniramous chaetiger and position on body; vph, ventral pharyngeal organ; vs, ventral slit.