Branchinotogluma bipapillata, Zhou & Wang & Zhang & Wang, 2018

Zhou, Yadong, Wang, Yueyun, Zhang, Dongsheng & Wang, Chunsheng, 2018, Branchinotogluma bipapillata n. sp., a new branchiate scale worm (Annelida: Polynoidae) from two hydrothermal fields on the Southwest Indian Ridge, Zootaxa 4482 (3), pp. 527-540 : 528-539

publication ID	https://doi.org/ 10.11646/zootaxa.4482.3.5
publication LSID	lsid:zoobank.org:pub:272874A3-F441-458A-ABE8-5DB9E470B992
DOI	https://doi.org/10.5281/zenodo.5954688
persistent identifier	https://treatment.plazi.org/id/BA6687C6-E43E-0127-FF14-F997FEE6E9C4
treatment provided by	Plazi
scientific name	Branchinotogluma bipapillata
status	sp. nov.

Treatment

Branchinotogluma bipapillata View in CoL n. sp.

urn:lsid:zoobank.org:pub:757A9897-4ADC-4C79-9FBB-60CF30722852

( Figs. 1–7 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 )

Material examined. Holotype ( RSIO35275 ), female, Southwest Indian Ocean Ridge, Longqi vent field, 49.6502°E, 37.7839°S, depth 2761 m, Stat. 35II-Dive94, coll. HOV Jiaolong, R / V Xiangyanghong 9, 11 January 2015: 26.6 mm long, 5.0 mm wide (without parapodia), 21 segments. Three paratypes ( RSIO35274 , female; RSIO35277 , male; RSIO35402 , female), same data as RSIO35275 : 23.3 – 32.3 mm long, 4.0 – 6.5 mm wide (without parapodia) GoogleMaps ; 1 paratype (RSIO3530, anterior partial), female, Southwest Indian Ocean Ridge, Duanqiao vent field, 50.47°E, 37.66°S, depth 1732 m, Stat. 34IV-SWIR-S035-TVG08, coll. television grab, R/V Dayang 1, 13 April 2015.

Description. Body short, 21 segments, slightly tapered anteriorly and posteriorly, with flattened ventrum and arched dorsum ( Figs. 1A–D View FIGURE 1 ). 10 pairs of elytra, subreniform or oval, large, thick, smooth ( Figs 1I, J View FIGURE 1 ), overlapping, covering dorsum and present on segments 2, 4, 5, 7, 9, 11, 13, 15, 17 and 19 ( Fig. 1A, C View FIGURE 1 ); elytrophores short ( Figs 2G View FIGURE 2 , 3A, C–F View FIGURE 3 ). Dorsal tubercles present on non-elytra-bearing segments ( Figs 2G View FIGURE 2 , 3B, G View FIGURE 3 ). Branchiae arborescent, with short terminal filaments, present in two groups attached to bases of notopodia and dorsal tubercles or elytrophore respectively ( Figs 2G View FIGURE 2 , 3B–C, E–G View FIGURE 3 ); beginning on segment 3, becoming larger in the middle region of body, and continuing to segment 19, where they are found as single small group.

Prostomium deeply bilobed, triangular anterior lobes with minute frontal filaments; median antenna with cylindrical ceratophore (extending to tips of anterior lobes of prostomium) in anterior notch, style long, significantly surpassing prostomium; without eyes; palps stout, tapering, with slender tips ( Figs 1E–H View FIGURE 1 ). First tentacular segment fused to prostomium, not distinct dorsally, forming lateral lips ( Fig. 1H View FIGURE 1 ); cylindrical tentaculophores lateral to prostomium, achaetous, each with small acicular lobes on medial side and acicula visible through the epidermis ( Figs. 1E–F View FIGURE 1 ), 2 pairs of tentacular cirri slender and as long as palps ( Fig. 1F View FIGURE 1 ). Segment 2 with biramous parapodia bearing prominent notopodial bract and the first pair of elytrophores ( Figs 3A, D View FIGURE 3 ); ventral cirri attached basally to neuropodia, shorter than tentacular cirri but much longer than that on following segments ( Figs 1B, D, H View FIGURE 1 , 3A, D View FIGURE 3 ). Mouth located between segments 1 and 2 ventrally. Thick muscular pharynx (everted) with 5 pairs of dorsal and ventral papillae surrounding the opening ( Fig. 2A View FIGURE 2 ), three medial pairs with small distal cirri ( Fig. 2A View FIGURE 2 lower left); 6 pairs of lateral tapered papillae located at the base of the pharynx ( Fig. 2C, D View FIGURE 2 ); two pairs of prominent jaws, curved, amber colored, minutely denticulate on inner borders ( Fig. 2A, B View FIGURE 2 ).

Parapodia biramous, neuropodia usually larger than notopodia, with a few exceptions on some posterior segments (e.g., parapodia on segments 20 and 21 of holotype ( Fig. 5B–C View FIGURE 5 )). Notopodia with elongate acicular lobes on lower sides ( Figs. 3A–G View FIGURE 3 ), lacking in bracts except on segment 2 ( Fig. 3A, D View FIGURE 3 ). Neuropodia long, with triangular prechaetal lobes and slightly shorter and rounded postchaetal lobes; lobes deeply notched on upper part, with projecting small lobe on dorsal base ( Figs. 3A–G View FIGURE 3 ). Dorsal cirri attached to the posterodorsal sides of notopodia on non-elytrigerous segments, with rather long cylindrical cirrophores and long filiform styles, extending beyond neurochaetae ( Figs 2G View FIGURE 2 , 3B, G View FIGURE 3 ). Ventral cirri on segment 2 long, extending to end of neuropodia ( Figs 1H View FIGURE 1 , 3A, D View FIGURE 3 ); short on segments 3–21, extending to middle part of neuropodia ( Figs 2E–F, H View FIGURE 2 , 3B, C, E–G View FIGURE 3 ).

Notochaetae few (usually less than 20), straight or slightly coiled subdistally, short to long, forming radiating bundles, smooth, much stouter than neurochaetae, acicular, tapering to pointed tips ( Fig. 4A, B, I View FIGURE 4 ). Neurochaetae very numerous, forming fan-shaped bundles, slender ( Fig. 3B–G View FIGURE 3 ). Supraacicular neurochaetae ( Fig. 4C, D, J View FIGURE 4 ) straight, with pointed tips (sometimes very slightly hooked); two rows of widely-spaced spines beginning subdistally and extending to near tips, finely spinous distally. Upper subacicular neurochaetae ( Fig. 4E, F, K–L View FIGURE 4 ) long, decreasing in length ventrally, slightly wider and more numerous than supraacicular neurochaetae; two rows of prominent spines emerging subdistally and extending to near end, spinous region shorter than that on supraacicular neurochaetae; tips bare and hooked. Lower subacicular neurochaetae ( Fig. 4G, H, M, N View FIGURE 4 ) short, delicate, tips flattened, with two rows of feather-like serration. Tips of notochaetae and neurochaetae usually embedded in sulfide ( Figs 3A–G View FIGURE 3 , 5A–F View FIGURE 5 ).

Ventral papillae 5 pairs, short, with blunt tips, present on segments 11–15 ( Fig. 2E View FIGURE 2 ). Pygidium with pair of long and slender anal cirri (one anal cirrus broken off on collected females, Figs 1B View FIGURE 1 , 2H View FIGURE 2 ).

On male (only one specimen collected, paratype RSIO35277), elytra much smaller on segment 19; branchiae present on segments 3–18. Ventral papillae 2 pairs, long, tapering, with slender tips, present on segments 12–13 ( Fig. 2F View FIGURE 2 ); four pairs of rounded ventral lamellae present on segments 14–17 ( Fig. 2F View FIGURE 2 ). Segments 18–19 slightly modified. Parapodia of segment 18 biramous, with notopodia as strong as neuropodia; branchiae present at base of notopodia as single small branch. Segment 19 ( Fig. 5D View FIGURE 5 ) with much smaller elytrophores and smaller elytra, without branchiae; neuropodia reduced, shorter than notopodia; ventral cirri attached at base of ventral sides of neuropodia, extending to tips of postchaetal lobes; neurochaetae similar to that on previous segments ( Fig. 5G–H View FIGURE 5 ), except the presence of some slender capillary neurochaetae, bearing widely-spaced lateral spines (marked with an arrow in Fig. 5G View FIGURE 5 ). Segments 20 and 21 fused slightly, modified more strongly than previous two; parapodia, strongly reduced; notopodial acicular lobes fused to cirrophores of dorsal cirri, with few notochaetae; ventral cirri attached near base of parapodia, long, extending beyond the end of neurochaetae ( Figs 2I View FIGURE 2 , 5E, F View FIGURE 5 ); neurochaetae consisting exclusively of capillary chaetae, with scattered spines ( Fig. 5I View FIGURE 5 ). Pygidium with pair of anal cirri, long, stout, tapered, basally inflated but not fused ( Fig. 2I View FIGURE 2 ).

Characters B. segonzaci B. trifurcus B. burkensis B. marianus B. tunnicliffeae B. hessleri B. sandersi B. japonica B. elytropapillata B. bipapillata Notopodial bract present not mentioned present on without present on present on present on present on starting on present on segment 2 segment 2 elytrigerous segment 19 in segment 19 segment 2 segment 2 segments males, and on segments 2 in both males and females On males 1 pair of long 1 pair of papillae not mentioned 1 pair of long 4 pairs of 1 pair of papillae 4 pairs of 1 pair of long 1 pair of long 2 pairs of long papillae on on segment 12; 5 papillae on papillae on on segment 12 papillae on papillae on papillae on papillae on segment 12; 5 pairs of lamellae segment 12; 6 segments 12-15; and 5 pairs of segments 12-15 segment 12; 5 segment 12 and 5 segments 12-13; pairs of ventral on segments pairs of lamellae 2 pairs of lamellae on and 3 pairs of pairs of pairs of lamellae 4 pairs of lamellae on 13-17 on segments rounded lamellae segments 13-17 lamellae on lamellae on on segments 13-17 lamellae on segments 13-17 13-18. on segments segments 16-18 segments 13-17 segments 14-17 Ventral 16-17 papillae On females without lacking in 7 pairs on not mentioned not mentioned 6 pairs of with or without 5 without 5 pairs of short 5 pairs of short lamellae and segments 11-17 lamellae on pairs of small papillae on papillae on bearing short segments 11-16 squarish papillae segments 11-15 segments 11-15 papillae on on segments segment 11 11-15 Notopodia small modified not mentioned short Small small; with short not modified small; with highly compressed slightly slightly, bearing notochaetae; and smooth short and modified; modified; very long dorsal small notopodial notochaetae; notochaetae with short and notopodia and cirri acicular lobe bearing delicate stout notochaetae; neuropodia fused to rounded small notopodial subequal in size cirrophore of flattened lamella acicular lobe fused dorsal cirrus; to cirrophore of ciliated on lower dorsal cirrus Modified side segment 18 Neuropodia slender not mentioned not mentioned coincal, short; Small achaetous, small not mentioned small, long neuropodia fused ciliated on upper capillary to form a lamina side; with long neurochaetae on ventral side; capillary with long capillary neurochaetae neurochaetae

Remarks. In previous studies, Branchinotogluma bipapillata n. sp. was assigned to Peinaleopolynoe (Copley et al., 2016; Zhou et al., 2018), which is characterized by 9–10 pairs of elytra, branchiae beginning on segment 2, one small acicular lobe on each tentaculophores, the absence of bracts on all parapodia, 7 pairs of border papillae surrounding pharynx and 4 pairs of ventral papillae on segments 12–15 (Pettibone 1993). Branchinotogluma bipapillata n. sp. and Peinaleopolynoe species do share one character, tentaculophores with small acicular lobes ( Figs 1E–F View FIGURE 1 ), and this character has not been reported in other branchiate scale worms, such as Branchinotogluma ( Zhang et al., 2018a) and Branchipolynoe ( Zhou et al., 2017) . However, characters, such as the number and distribution of branchiae, notopodial bracts on segment 2 ( Fig. 3A, D View FIGURE 3 ), modified posterior segments on male ( Fig. 4D–F View FIGURE 4 ), make the new species more like Branchinotogluma species. The COI -based ML tree also shows that it is most strongly affiliated with several other Branchinotogluma species, rather than to the published sequences of an as yet undescribed species of Peinaleopolynoe ( Fig. 6 View FIGURE 6 ). However, COI is insufficient to resolve the phylogenetic relationships among all those branchiate scale worms comprehensively (only a few species can be used) as some nodes on the ML tree are poorly supported. Using the limited dataset available for branchiate worms, a combined analysis ( Fig. 7 View FIGURE 7 ) based on concatenated genes (COI, 16S and 18S) reveals a similar pattern of this group to previous studies ( Zhang et al. 2018a; Zhang et al. 2018b): (1) Branchiate scale worms ( Branchinotogluma and Branchipolynoe species) form a well-supported clade; (2) Branchinotogluma is paraphyletic, while the three Branchipolynoe species tend to be more deeply placed in the branch, forming one monophyletic subclade. The placement of B. bipapillata n. sp. in the clade is also well supported, and it is sister to the Branchinotogluma japonicus + Branchipolynoe branch. Thus, either morphological or molecular evidences suggest that the placement of the new species in Branchinotogluma is more reasonable than in Peinaleopolynoe , although more genetic markers from a wider range of species are needed for further revision of this clade.

Nine recognized species have currently been placed in Branchinotogluma ( Desbruyères et al. 2006; Zhang et al., 2018a). It is easy to distinguish the new species from its congeners by comparison of their characters ( Table 1). Characters, such as the presence of small acicular lobes on tentacular segment ( Fig. 1E–F View FIGURE 1 ), two pairs of long conical ventral papillae on males ( Fig. 2F View FIGURE 2 ), five pairs of dorsal and ventral papillae surrounding the opening of pharynx ( Fig. 2A View FIGURE 2 ) and the presence of long ventral cirri on segments 20 and 21 of male ( Figs 2I View FIGURE 2 , 5E–F View FIGURE 5 ), can each separate B. bipapillata n. sp. from all other members in this genus. Pharynx papillae and ventral papillae show high degree of diversity, as there are six and five different types in the genus regarding their size, shape and distribution pattern ( Table 1), making them useful identification tools at the species level. The smooth and stout notochaetae are also unusual in the genus ( Fig. 4A, B, I View FIGURE 4 ), as it is present in only one species ( B. sandersi ) besides B. bipapillata n. sp. Another unique feature of the new species is the lower subacicular neurochaetae with delicate feather-like spines ( Fig. 4G–H, M–N View FIGURE 4 ). Although it has not been reported from other Branchinotogluma species ( Miura & Hashimoto 1991; Miura & Desbruyères 1995; Pettibone 1985; Pettibone 1988; Pettibone 1989; Zhang et al. 2018a), we are not sure if it is unique to the new species as details of neurochaetae are sometimes insufficient in original description. For example, an SEM image of B. hessleri neurochaetae (Fig. 8 in page 220 of Desbruyères et al. 2006) shows spines with similar outline to the lower subacicular neurochaetae to B. bipapillata n. sp., however the details of the spines are missing in either the original description ( Pettibone 1985) or the later publication ( Desbruyères et al. 2006). This makes the direct comparison of neurochaetae between different species difficult. Other characters used to do pairwise comparison in the genus are also listed in Table 1.