Myxicola bushae Putignano, Langeneck & Giangrande, 2024, sp. n.
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 bushae

description: Myxicola bushae sp. n. Putignano, Langeneck & Giangrande, 2024
(Figures 1, 2)
Holotype
YPM IZ 030017; Atlantic Ocean, Gulf of Maine, Eastern Bay, USA, Maine, Hancock County, Lamoine, Lamoine State Park; collected 17 August 1970 at 0.6 m depth on rocky intertidal with gravel, mud bottom and Zostera ssp. Fixed and preserved in 70% ethanol; identified and labelled as Myxicola infundibulum by Johanna M. Reinhart.
Description
Holotype complete; body yellowish, square in cross section (Figure 1A). Crown same colour as body. No information concerning live colouration. Body 1.6 cm long; 8 thoracic and 61 abdominal chaetigers; maximum width 2.5 mm. Thorax longer than wide. Crown 0.65 cm long, holding 13 pairs of radioles; ratio body/crown length of 2.46. Peristomium 1.37 mm long (distinctly longer than thoracic segments), divided in anterior and posterior peristomial ring by a notch all around; mid-ventral lobe of anterior peristomial ring triangular, of thick membranous appearance, with medial groove; anterior peristomial margin high ventrally and dorsally, slightly lower laterally, leaving the junction between crown and body partially visible laterally (Figure 1A–C); mid-lateral incision narrow. Shallow ventral groove along the anterior peristomial ring, with a deep dorsal rut (Figure 1B–D). Dorsal lips with very short radiolar appendages, not extruding from lips and not visible in lateral view (Figure 1D); dorsal pinnular appendages and ventral radiolar appendages both absent. Ventral lips yellowish, high and tubular, distally enlarged, extending dorsoventrally along inner surface of base of radiolar lobes and connecting ventrally to the radiolar lobes; parallel lamellae and ventral sacs both absent (Figure 1D). Outer radioles with translucent surface, connected by a high semi-transparent palmate membrane. Radiolar tips>1/5 of total radiole length, same colour as radiole, strap-like with tapering blunt ends (Figure 1E). Thick and blunt pinnules, up to>1/4 as long as the entire radiole, same colour as radioles, arranged in pairs; longest pinnules subdistal on radioles, abruptly shortening to radiolar tips. Radiolar skeleton like four similarly sized square cells in cross section, in squared arrangement and surrounded by hyaline matrix; graft cells for pinnules skeleton squared and small, undivided, ventrally contiguous to the latter (Figure 1G). Radiolar and peristomial eyes not visible. Glandular girdle on the posterior margin of chaetiger 2 (Figure 1B, C). Eyes present from fourth thoracic chaetiger, single, rarely double; thoracic eyes inserted ventrally to the parapodium, posterior to chaetal tufts and anterior to neuropodial tori, shifting slightly dorsally in the abdomen. Pygidium papilliform, with mid-ventral cleft on which abdomen terminates; at least one pair of pygidial eyes each side (Figure 1F). Thoracic notochaetae numerous, narrowly hooded, with long and tapering tips, arranged in circle to form dense tufts; peristomial notochaetae with slightly shorter and narrower hood (Figure 2A, B). Chaetigers 2–8 with extremely curved neuropodial acicular uncini, bearing 2 small teeth (anterior biggest) above a short main fang, not reaching half of its length (Figures 2D, E, 15A); a series of 2 parallel teeth visible when uncini are viewed frontally (Figure 2F). Thoracic neuropodial tori discrete, postero-ventral to chaetal tufts. Abdominal neurochaetae narrowly hooded, shorter than peristomial notochaetae; forming less conspicuous and dense tufts than on thorax, number of chaetae per fascicle decreasing through abdomen (Figure 2C). Abdominal uncini with 2 parallel teeth above main fang, more noticeable in frontal view (Figure 2I, J), at least one reaching or exceeding half of main fang length; only longest tooth is visible in lateral view (Figure 2G, H); breast rounded, main fang always shorter or slightly shorter than breast, uncini as high as long (Figure 15B).
Remarks
The material was examined to verify the presence of M. steenstrupi in the Bay of Fundy. Bush (1905) did not describe the specimen she found, just referring to the original description by KrØyer (1856). However, Bush (1905) illustrated thoracic notochaetae, thoracic and abdominal uncini of the specimen she identified as M. steenstrupi, allowing us to check the identity of this taxon.
Our findings are consistent with drawings by Bush (1905). Thoracic uncini have similar bending and main fang length (Figure 14L 1–L 4), showing a single tooth almost reaching half of main fang length (Figure 14L 4), while abdominal uncini show a similar main fang (always shorter than breast) and a single apical tooth slightly exceeding half of main fang length (Figure 14M 1, M 2), lacking basal posterior prolongation. Differences are mainly in the level of detail reported in our analysis, due to divergence in instruments and technology used, since Bush’s work was conducted more than a century ago. Thus, we recognise M. bushae sp. n. as the same species reported by Bush (1905), considering the taxon a different species from M. steenstrupi.
Important morphological similarities between M. bushae sp. n. and M. steenstrupi s.s. can be noticed in body/crown ratio, number of segments, pinnule length and morphology, which are all also very similar, between members of these species. Differences are related to the number of radioles (17–21 pairs for M. steenstrupi as opposed to 13 for M. bushae sp. n.), lengths of radiolar tips (>1/3 compared to>1/5), morphology of thoracic tori (inconspicuous in M. steenstrupi s.s.) and shape of dorsal radiolar appendages (sublaminar elongated-triangular appendages for M. steenstrupi s.s.). Furthermore, individuals of M. steenstrupi are longer, up to 6 cm for 52 abdominal segments. Size, body/crown ratio and number of segments suggest that M. steenstrupi is a small species belonging to the ‘infundibulum group’ (Putignano et al. 2023), characterised by a relatively longer crown, 8 thoracic chaetigers, and a low number of abdominal chaetigers.
In a recent work, Darbyshire (2023) enstablished a neotype for M. infundibulum and described a new species for the genus, Myxicola polychroma Darbyshire, 2023. Myxicola bushae sp. n. does not show similarities to either of those forms, diverging from both in the morphology of lips and associated structures, radiolar skeleton arrangement, shape of peristomium, morphology of thoracic and abdominal uncini. Furthermore, Darbyshire (2023) underlines the endurance of the dark pigmentation typical of M. infundibulum after fixation, while this character is absent in M. bushae sp. n. and in M. polychroma, which also shares the presence of discrete thoracic neuropodial tori. Lastly, analysis of syntypes of M. steenstrupi from Faroe Islands and Greenland reveals the presence of small, digitiform (Faroe Island specimens) and slender, digitiform (Greenland specimens) radiolar appendages and enlarged, lobate ventral lips, which further differentiate the members of M. steenstrupi and M. bushae sp. n.
Within the ‘infundibulum group’, M. bushae sp. n. exhibits several similarities to M. mikacae Putignano, Gravili and Giangrande, 2023, M. violacea Langerhans, 1884, M. sulcata Ehlers, 1912 and M. fauveli Potts, 1928. However, important differences separate members of this group: specimens of M. mikacae show distinct, club-like radiolar appendages and radiolar skeleton composed of a single row of cells; members of M. fauveli are characterised by peculiar radiolar tips, where the palmate membrane end terminates with a pair of complex hyaline structures, resembling the compound eyes of members of Acromegalomma Gil and Nishi, 2017. Members of M. sulcata differ from specimens of M. bushae sp. n. in the shape of thoracic uncini (with longer main fang and single apical tooth in members of the former species), in having abdominal uncini with a ‘minute handle’ (Tovar-Hernández et al. 2017), in the presence of short, tongue-like radiolar appendages; mid-ventral lobes and radiolar tips also slightly differ between those animals. Finally, specimens of M. violacea differ from members of M. bushae sp. n. mainly in the presence of peristomial eyes and in having radiolar skeleton organised in a single row of cells, in lateral view.
Etymology
The species is named after Katharine Jeannette Bush (1855–1937), who identified specimens from the same locality as M. steenstrupi, in honour of her valuable contribution to the taxonomy of sabellid and serpulid polychaetes.
Distribution and ecology
Eastern Bay; potentially present along the North American Atlantic Coast and misidentified as either M. infundibulum or M. steenstrupi. The only information concerning the ecology of these animals is reported in the locality label of the sample: ‘Rocky intertidal in some areas gravel & mud in others, Zostera, 2–2 ft’.
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 1395-1400, DOI: 10.1080/00222933.2024.2370664, http://zenodo.org/record/13758466