Spiophanes Grube, 1860

Meissner, Karin, Schwentner, Martin, Göưing, Miriam & Fiege, Thomas Knebelsberger and Dieter, 2023, Polychaetes distributed across oceans-examples of widely recorded species from abyssal depths of the Atlantic and Pacific Oceans, Zoological Journal of the Linnean Society 199, pp. 906-944 : 929

Genus Spiophanes Grube, 1860

Type species: Spiophanes kroyeri Grube, 1860 .

Spiophanes Grube, 1860: 88–89 , pl. 5, fig. 1. Type species: Spiophanes kroyeri Grube, 1860 , by monotypy. – Meissner and Hutchings 2003: 118–120, figs 1, 2. – Meissner 2005: 6. – Meissner and Blank 2009: 6–7.

Morants Chamberlin, 1919: 17 . Type species: Morants duplex Chamberlin, 1919 , by monotypy. Junior synonym.

Diagnosis: (See also Meissner and Blank 2009 for further details.) Prostomium rarely rounded, usually subtriangular or bell-shaped; anterolateral horns of different length present or absent, anterior margin not incised; occipital antenna present or absent. Branchiae absent. Nuchal organs as dorsal ciliated organs of different types present. Body divided into three regions: anterior region extending to chaetiger 4, parapodia with well-developed postchaetal lamellae in both rami; middle region from chaetiger 5 to last chaetiger with capillaries rather than neuropodial hooks in neuropodium, neuropodial postchaetal lamellae reduced; middle chaetigers with parapodial glandular organs, their presence most conspicuous in chaetigers 5–7(8) where they open via chaetal spreaders of different types (see: Meissner and Hutchings 2003) rather than simple vertical slits in the neuropodia; posterior region starts between chaetigers 13–16 with first appearance of neuropodial hooks. Chaetae include one to two conspicuous crook-like spines in neuropodia of chaetiger 1; stout sabre chaetae in inferiormost position usually present from chaetiger 4; bacillary chaetae maybe exposed in chaetigers 5–9; capillaries present in both parapodial rami along the body arranged in one to three distinct or indistinct rows; hooks present in posterior region, usually quadridentate with main fang surmounted by single tooth and two smaller apical teeth in parallel position; with or without secondary hoods. Transverse dorsal ciliated crests usually present. Clusters of cilia herein referred to as ‘lateral ciliated patches’ present or absent in parapodia of the middle body region. Ventrolateral pouches present or absent in posterior region between neuropodia. Pygidium with two or more anal cirri.

Remarks: The generic diagnoses by Meissner and Blank (2009), and more recently by Blake et al. 2019, have not undergone considerable change over the last 20 years. The presence of up to three Spiophanes species in our source material from abyssal depths was suggested based on sequence analysis. Two species are newly described here; the identity of the third species and its potential assignment to a known species is discussed. The three putative species are all morphologically very similar and characters useful for morphological species delimitation are difficult to find. Prostomial characters, nuchal organs, both distribution and details of parapodial glandular organs along the body, as well as many chaetal characters, are in good agreement among the three species (see details in the species descriptions). In all three species sabre chaetae are present from chaetiger 4 throughout the body, but are oħen strikingly long in anterior chaetigers compared to those in more posterior and hook-bearing segments. Neuropodial quadridentate hooks with reduced hoods start on chaetiger 15. All three species possess very long capillaries in notopodia of the posterior part of the median region, and even longer capillaries in posterior notopodia. Morphological differences concern the ciliated patches, a character that has not been formerly described for Spiophanes spp. , and has been discovered in formalin-fixed specimens during our SEM studies. Ciliated patches are clusters of cilia. They are present in parapodia of the middle body region where they are arranged in more or less regular rows along the distal edge of neuropodia. Observed variation in the presence of ciliated patches was intraspecific but also interspecific ( Table 6 ; Fig. 13 ). Intraspecific variation concerned the number of patches found on a neuropodium in a certain chaetiger. Differences between putative species became apparent when comparing median values of the number of patches for each chaetiger for all studied specimens ( Table 6 ; Fig. 13 ). In Spiophanes pacificus sp. nov., the highest number of patches was observed in chaetigers 8–10 with up to seven patches arranged in a regular row, or four to five patches considering the median values for counts in all specimens of this species ( Table 6 ; Figs 13 , 14F, I ). In preceding parapodia the number of patches was reduced to only one and maximally three. In Spiophanes australis sp. nov. the highest number of patches was observed more anteriorly along the body in chaetigers 5–7, with the maximum of seven patches in chaetiger 6 in one specimen, and maximally four to six patches in chaetigers 4–7 for other specimens ( Table 6 ; Figs 13 , 16D, F, G ). In S. australis sp. nov., the arrangement of patches in rows was less strict and rather seemed slightly irregular. In the third species, Spiophanes cf. longisetus Meissner, 2005 , paưerns of ciliated patches could not be securely detected, only single patches randomly on some parapodia of the middle body region were detected. Unfortunately, ciliated patches are not reliably observable in ethanol-fixed specimens and their recognition, in general, also depends on the quality of preservation, and moreover relies on SEM studies. Thus, the number of collected data regarding this character was restricted and, admiưedly, not fully reliable in every detail. But since observed differences between S. pacificus sp. nov. and S. australis sp. nov. were distinct, this newly found character might turn out to be useful, and is here newly added to the diagnosis of Spiophanes . Also, there was slight variation in the number of neuropodial quadridentate hooks in posterior parapodia. In S. pacificus sp. nov., usually three hooks in a row are present (rarely four); in S. australis sp. nov., usually four (rarely three); and in S. cf. longisetus , the number of neuropodial hooks is usually five.

Figures

Figure 13. Distribution of lateral ciliated patches in neuropodia along chaetigers of the middle body region in Spiophanes pacificus sp. nov. and S. australis sp. nov.; trendlines of calculated mean and median values for counted patches also shown; character only reliably observable in formalin fixed specimens examined with SEM.

Figure 14. Spiophanes pacificus sp. nov., LM and SEM studies: A, holotype, complete specimen original preservation in 96% ethanol; note nuchal organ with associated pigment, and anal cirri. B, close-up of anterior region, latero-oblique view. C, anterior region, dorsal view; note short cirriform occipital antenna with rounded tip, also note nuchal organ reaching end of chaetiger 2. Inset C, close-up of antenna of same specimen. D, middle body region with pigment in parapodia of chaetigers 11–14, dorsal view. E, anterior end, lateral view; note stout cirriform occipital antenna and extension of dorsal ciliated nuchal organs to the end of chaetiger 2. F, chaetigers 8–10 in lateral view; note vertical row

Figure 16. Spiophanes australis sp. nov., LM and SEM studies: A, prostomium and anteriormost chaetigers, antero-oblique view; note short papilliform occipital antenna; crook-like chaeta lost on right side in first neuropodium. B, anterior region, dorsal view; note nuchal organ with associated yellow pigment. C, same but different specimen; note well-preserved nuchal organs.D, parapodia of chaetigers 4–7, lateral view; note sabre chaeta at 4th chaetiger, and vertical row of ciliated patches at chaetigers 5–6/7, arrowhead pointing at 2nd patch in line (counted from above) at 5th chaetiger.E, neuropodial quadridentate hooks with half-hood in chaetiger 15; note four hooks arranged in a row. F, chaetiger 7, lateral view; note ciliated patches and opening of glandular organ with bacillary chaetae protruding from inside the gland.G, chaetigers 7–8, lateral view; note reduced number of ciliated patches in chaetiger 8.—A, B, E, paratypes SMF 30634 (SEM stub 1334); C, holotype SMF 30647; D, F, G, SMF 30632; all Argentine Basin.Scale Bars: A–C, 100 µm; D, G, 20 µm; E, F, 10 µm.