Myxicola conjuncta , Bush 1905
Creators: name: Putignano, Matteo
name: Langeneck, Joachim
name: Giangrande, Adriana
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Sabellida
Sabellidae
Myxicola
Myxicola conjuncta

description: Myxicola conjuncta Bush, 1905
(Figures 5, 6)
Myxicola conjuncta Bush, 1905: p. 217 –218; pl. XXVI, figs. 1, 4a; pl. XXXVIII, figs. 1–11
Material examined
Syntype collected by W. R. Coe during the Harriman Alaska Expedition, 1899; Prince William Sound, USA, Alaska, Valdez-Cordova Census Area, Virgin Bay; specimen preserved in 70% ethanol; YPM IZ 002773.AN.
Redescription
Specimen complete, orange-yellowish body, a ‘[…] pale yellow color […] sometimes a tinge of brown on the thorax’ is reported in the original description (Bush 1905: p. 217); cylindrical, slightly flattened dorso-ventrally. Crown same colour as body, while a darker colouration is reported in the original description, due to the presence of pinnulae with ‘[…] decided brown (coloration) […] giving a tinge of color to the whole’ (Bush 1905: p. 217) (Figure 5A). Interestingly, the photograph from the original work shows a distinctly darker peristomium (Figure 13C). Body 7.95 cm long, with 8 thoracic and 94 abdominal chaetigers; maximum width 5 mm; thorax longer than wide (Figure 5A). Crown 1.45 cm long, holding 17 and 18 radioles on left and right lobe, respectively; ratio of body/crown length of 5.48. Peristomium 1.91 mm long (distinctly longer than thoracic segments), peristomial rings separated by distinct groove all around peristomium; mid-ventral lobe of anterior peristomial ring poorly developed, with double-pointed tip and thicker lateral edges, from which a membrane emerging from lateral edges partially covers bases of radiolar lobes; peristomium lower laterally, leaving the junction between crown and body just visible; mid-lateral incision distinct (Figure 5B, C). Dorsal lips with remarkably short radiolar appendages, not extruding from ventral lips and not visible in frontal view (Figure 5D); pinnular appendages and ventral radiolar appendages both absent; ventral lips yellowish, well developed and low, extending dorsoventrally along inner surface of base of radiolar lobes; parallel lamellae and ventral sacs both absent (Figure 5D); outer radiole surface translucent, connected by a high semi-transparent palmate membrane; radiolar tips 1/5 of total radiole length, same colour as radiole, strap-like with rounded tips (Figure 5E); pinnules thick, distally rounded, yellowish in colour, up to 1/4 of total radiole length, in a staggered arrangement along the radiole; longest pinnules in medial position, then abruptly shortening to beginning of radiolar tips. Radiolar skeleton composed by 9 cells, 8 of them arranged around central one, all surrounded by hyaline matrix; graft cells of pinnular skeleton squared and small, undivided, ventrally contiguous to latter (Figure 5G). Radiolar eyes and peristomial eyes not visible. Glandular girdle near posterior margin of chaetiger 2. Lateral eyes present from chaetiger 5; single thoracic eyespots directly posterior to chaetal tufts, shifting to more dorsal position on abdomen, increasing in number of eyespots towards mid abdomen (up to 6 eyespots on each side of chaetiger) then decreasing towards pygidium (2 eyespots on each side of chaetiger). Pygidium slightly damaged and flattened; pygidial eyes not visible (Figure 5F). Numerous narrowly hooded thoracic notochaetae with elongated, tapering tips and distinctly thin, long wing continuing hood along shaft, disposed circularly to form conspicuous tufts; peristomial notochaetae slightly shorter; edge of the hood showing marked serration (Figure 6A, B); chaetigers 2–8 with slightly curved acicular uncini, showing a long main fang surmounted by 2–3 small teeth, less than half of the main fang length (Figures 6D, E, 15E); thoracic neuropodial tori inconspicuous. Numerous abdominal neurochaetae narrowly hooded, similar to peristomial notochaetae, forming conspicuous tufts along most of abdomen, only significantly decreasing in number of chaetae per fascicle on last segments (Figure 6C). Abdominal uncini with apical tooth slightly longer than half of the main fang; larger uncini with secondary, short tooth, apical to latter (Figure 6G, H); breast squared, main fang shorter than breast; handle vestigial; uncini longer than high (Figures 6F, G, 15F).
Remarks
This specimen was examined to check the validity of M. conjuncta Bush, 1905 and the present description is consistent with Bush (1905). Bush (1905: p. 217–218) reported a ‘[…] thin median triangular lobe […]’, which is partially damaged in the examined specimen. The only discrepancy between our observations and the original description concerns the morphology of radiolar tips and pinnules, reported as ‘[…] comparatively long and slender […]’ and ‘[…] very long and slender […]’ respectively, and the presence on ‘[…] the sixth to eighth segments [of] additional, often more slender, spear-shaped or hastate setae […] in the middle of the fascicles […]’. However, photographs of radioles present in the original description show an identical morphology (Figure 13D), while the ‘hastate setae’ (Bush 1905, fig. 14B1–C) can be easily explained as broken chaetae and uncini, as such a typology of chaetae is absent in the whole genus Myxicola.
Thoracic uncini show the same curvature, but in the illustrations no teeth are reported (Bush 1905, fig. 14D1–D3), which, as for M. bushae sp. n., can be explained by the instruments available at the time for taxonomical analysis. Abdominal uncini are almost identical to those in the present description, but no secondary short teeth are reported (Bush 1905, fig. 14E1, E2); however, it should be noted that even with today’s instruments and techniques, such teeth are not always visible. Interestingly, a marked serration on the hood of chaetae seems to be shown in the drawings, similarly to what we observed in the present analysis (Bush 1905, fig. 14A1–A3).
This species was synonymised with M. infundibulum by Hartman (1942), who did not examine the type material. However, this species can be differentiated from M. infundibulum based on the morphology of radiolar appendages, radiolar tips, radiolar skeleton and mid-ventral lobe.
Myxicola conjuncta is a large species of the ‘ infundibulum group’ (8 thoracic chaetigers), with a high number of abdominal chaetigers (Putignano et al. 2023). However, this species can be easily distinguished from other large congeners based on the composition and arrangement of the radiolar skeleton (composed of two rows of big, rounded cells in both Mediterranean and European Atlantic species), on the morphology of radiolar tips (filiform and tapering in Myxicola giuliae Putignano, Gravili and Giangrande, 2023 and Myxicola cosentini Putignano, Gravili and Giangrande, 2023, lanceolate in M. infundibulum and Myxicola cataldoi Putignano, Gravili and Giangrande, 2023, leaving some resemblance with M. polychroma), radiolar appendages (long and tapering in M. cataldoi, club shaped in M. giuliae and M. cosentini, triangular in M. infundibulum and M. polychroma), and shape of abdominal uncini (with bigger and smaller teeth as a row above the main fang).
Distribution and ecology
Known for the type locality. No information concerning its ecology is reported.
description: Published as part of Putignano, Matteo, Langeneck, Joachim & Giangrande, Adriana, 2024, The forgotten diversity of the genus Myxicola (Polychaeta: Sabellidae) in North America: redescription of historical taxa and description of two new species, pp. 1393-1427 in Journal of Natural History 58 (37 - 40) on pages 1404-1408, DOI: 10.1080/00222933.2024.2370664, http://zenodo.org/record/13758466