Spiophanes australis, Meissner & Schwentner & Göưing & Fiege, 2023

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 : 933-936

publication ID	https://doi.org/ 10.1093/zoolinnean/zlad069
publication LSID	lsid:zoobank.org:pub:65B60DD3-64C9-4262-B7B2-74DA4D3D889F
DOI	https://doi.org/10.5281/zenodo.10497566
persistent identifier	https://treatment.plazi.org/id/743EE917-FFED-FF90-FCA1-26721FB4F952
treatment provided by	Plazi
scientific name	Spiophanes australis
status	sp. nov.

Treatment

Spiophanes australis View in CoL sp. nov. Meissner, Göfling and Fiege

( Figs 13 View Figure 13 , 16 View Figure 16 , 17 View Figure 17 ; Table 6 View Table 6 )

Type material: Holotype. South Atlantic Ocean , Argentine Basin, M 79-1 (DIVA 3), stn 533-1 EBS, 4602 m, 15 Jul 2009, one af fragmented into two pieces (21 chaetigers, 3.1 mm long, width 0.6 mm), original fixation formalin, now in 70% EtOH ( SMF 30647 About SMF ).

Paratypes: SW Atlantic Ocean, Argentine Basin , M 79-1 ( DIVA 3 ) , stn 533-1 EBS, 4602 m, 15 Jul 2009, four af original fixation formalin, now in 70% EtOH ( SMF 30634 About SMF incl. one af SEM 1334 ); stn 534-1 EBS, 4608 m, 16 Jul 2009, six af, original fixation formalin, now in 70% EtOH ( SMF 30632 About SMF incl. one af SEM 1335 ); stn 534-1 EBS, 4608 m depth, 16 Jul 2009, one af, fixed in 96% EtOH, tissue sample ( SMF 32277 About SMF ) .

Measurements for largest paratype (SMF 30632) af of about 19 chaetigers, length ~ 3 mm, width ~ 0.6 mm (chaetae omiưed); other paratypes all af max. 21 chaetigers, between 0.9–4.7 mm long, 0.3–0.6 mm wide.

Description: Holotype anterior fragment with 21 chaetigers, 0.6 mm wide and 3.1 mm long. Specimens between 0.3–0.9 mm in width, and up to 4.7 mm long, all anterior fragments of max. 21 chaetigers. Body slender, subcylindrical.

Prostomium bell-shaped with straight anterior margin extending into short rounded anterolateral projections ( Fig. 16A–C View Figure 16 ), short papilliform occipital antenna present ( Fig. 16A View Figure 16 ). Dorsal ciliated organs (suggested to represent nuchal organs) as dorsal ciliated grooves posterior to the prostomium (ciliation detectable with SEM), if viewed with LM appearing as thick straight double lines of ochre or yellow colour reaching the end of 2nd chaetiger ( Fig. 16B, C View Figure 16 ), sometimes outer margins of ciliated grooves demarcated and then appearing U-shaped. Eyes absent. Peristomium moderately developed. First parapodium oriented dorsolaterally, second laterally to almost completely laterally, thereaħer orientation of parapodia lateral ( Fig. 16A– D View Figure 16 ). Postchaetal lamellae of chaetigers 1–4 narrow subulate in notopodia ( Figs 16A, B View Figure 16 , 17A View Figure 17 ), longest in first two to three chaetigers, thereaħer notopodial lamellae decreasing in length; neuropodial postchaetal lamellae in first chaetiger also subulate with broad base and slender tip, slightly shorter than in notopodium and less narrow ( Figs 16A View Figure 16 , 17A View Figure 17 ), from 3rd chaetiger neuropodial lamellae distinctly shorter and more stout than notopodial lamellae, gradually changing into a subtriangular shape ( Figs 16D View Figure 16 , 17B View Figure 17 ); chaetigers 5–8 with short broad subulate notopodial lamella, sometimes distally with minute sharp tip, reduced neuropodial postchaetal lamella ( Figs 16D, G View Figure 16 , 17C View Figure 17 ); from chaetiger 9 notopodial lamella low with short distal tapering, gradually base becoming more voluminous and the tip more slender and longer; from about chaetiger 14 throughout the end of the body with broad base and short cirriform tip, neuropodial lamella reduced ( Fig. 17D View Figure 17 ). Chaetal spreader of the ‘0 + 1 type’ with semicircular glandular opening developed in chaetigers 5–7 ( Fig. 16D, F, G View Figure 16 ), in chaetiger 8 chaetal spreader present but with hole-like opening allowing the passage of only single bacillary chaeta ( Fig. 17C View Figure 17 ); glandular organ of chaetigers 9–14 opens as a lateral vertical slit, without chaetal spreader. Ciliated patches might be observed laterally on neuropodia of chaetigers 4–9, with the highest number of patches in chaetigers 5–8 and up to seven patches arranged in less strict rows in a single neuropodium ( Table 6 View Table 6 ; Figs 13 View Figure 13 , 16D, F, G View Figure 16 ; see discussion regarding this character above for Spiophanes ). Ventrolateral intersegmental genital pouches absent. Dorsal crests not observed but none of the specimens very well preserved.

Chaetiger 1 bearing one or two stout, crook-like chaetae in neuropodium. Other chaetae in chaetigers 1–4 capillaries, in neuropodia arranged in two rows with chaetae in anterior row shorter and appearing slightly granulated when viewed with light microscopy, in second row longer and smooth, in notopodia arranged in a tuħ or forming irregular rows; from chaetiger 4 inferior sabre chaeta present, stout and granulated near the tip, sabre chaeta of considerable length, becoming shorter in middle and posterior chaetigers ( Figs 16A, D View Figure 16 , 17A, B View Figure 17 ). Chaetigers 5–14 with stout granulated, narrow bilimbate neurochaetae, arranged in one (to two) row; notochaetae both granulated and smooth capillaries arranged in two to three irregular rows, longest chaetae in superior position ( Figs 16D, F, G View Figure 16 , 17C View Figure 17 ). Posterior region starting at chaetiger 15 with first presence of neuropodial quadridentate hooks with main fang surmounted by single tooth and two smaller teeth in parallel position in uppermost position, hooks with half-hood from the tip of the main fang to the shaħ, usually four (rarely three) hooks arranged in one row ( Figs 16E View Figure 16 , 17D View Figure 17 ); single accompanying capillary next to sabre chaetae present; notopodia with slightly granulated capillaries arranged in a tuħ, oħen broken but also distinctly longer if intact ( Fig. 17D View Figure 17 ). Bacillary chaetae as thin, hirsute bristles can be exposed on chaetigers 5–8 though more numerous in chaetigers 5–7 compared to chaetiger 8 and here never protruding. Ventral sabre chaetae from chaetiger 4, of conspicuous length in anterior and middle chaetigers, shorter in hook-bearing chaetigers ( Fig. 16D–G View Figure 16 ); appearing granulated near the tip under light microscope. Pygidium unknown since all specimens incomplete.

Pigmentation: Only yellowish pigment associated with nuchal organ discernable ( Fig. 16B, C View Figure 16 ).

Methyl green staining pattern: Chaetigers of the anterior middle body region, and particularly chaetiger 8, most intensely stained.

Biology: None of the studied specimens was observed bearing gametes.

Remarks: The species is morphologically very similar to other congeners from the deep-sea also discussed in this paper: S. pacificus sp. nov. (found at different localities in the Pacific Ocean) and S. cf. longisetus (found at more northerly locations of the Atlantic Ocean and perhaps synonymous with S. abyssalis Maciolek, 2000 from the NE Atlantic, see Remarks below for S. cf. longisetus Meissner, 2005 ). The species are best distinguished by the distribution of lateral neuropodial ciliated patches along the middle body region ( Table 6 View Table 6 ; Fig. 13 View Figure 13 ) and the number of neuropodial hooks (see above introductory paragraph under Spiophanes for details of morphological distinction). The species can also be distinguished based on information from molecular markers (COI).

Etymology: The specific name australis Latin (=southern); refers to the known distribution of the species in soħ boưom habitats of the South Atlantic Ocean and probably also in adjacent Antarctic waters (Weddell Sea).

Distribution: The species has been collected from soħ boưoms of the Argentine Basin in the SW Atlantic Ocean ( Fig.5 View Figure 5 ; Supporting Information, Table S2 View Table 2 ). Water depth was about 4600 m. The species probably also occurs in more southerly waters but this only refers to preliminary identification of specimens collected in the Weddell Sea at 2046 m water depth. Since the acquisition of COI molecular markers failed the specimen is listed as S. cf. australis sp. nov., and gained 18S sequences are deposited in GenBank under this name. Tissue all used in molecular analysis.