Echinoderes serratulus, Grzelak & Sørensen, 2022

Grzelak, Katarzyna & Sørensen, Martin V., 2022, Echinoderes galadrielae Grzelak & amp; Sørensen 2022, sp. nov., Zoological studies (Zool. Stud.) 55 (32), pp. 32-32 : 11-17

publication ID	https://doi.org/ 10.5281/zenodo.7225407
persistent identifier	https://treatment.plazi.org/id/7E3687A4-FFA2-D256-FC8A-218CFE54FB58
treatment provided by	Valdenar
scientific name	Echinoderes serratulus
status	sp. nov.

Treatment

Echinoderes serratulus View in CoL sp. nov. Yamasaki urn:lsid:zoobank.org:act:68D196A3-A3D0-48AD-92FC-9406562D8CD0 [New Japanese name: Nokogiri togekawa]

Material examined: All specimens collected 25 November 2014 at 10 m depth near Hon Mieu Island, Nha Trang, Vietnam (12°11.60'N, 109°13.96'E). Holotype: adult female (ZIHU-5053), mounted in Fluoromount G ®. Allotype: adult male (ZIHU-5054), mounted in Fluoromount G ®. Paratypes: one adult female and two adult males (ZIHU-5055-5057), mounted in Fluoromount G ®. Additional material: four specimens for SEM (three adult females and one adult male), mounted on aluminum stubs.

Etymology: The species name serratulus is from Latin, meaning ‘serration’, referring to the species’ conspicuous primary pectinate fringe.

Diagnosis: Echinoderes with short acicular spine middorsally on segment 4 and sublaterally on segments 6 and 7; lateroventral tubules on segments 5 and 8, midlateral tubules on segment 9, and laterodorsal tubules on segment 10; large sieve plates on segment 9; primary pectinate fringes ventrally on segments 1-9 conspicuous, with longer fringe tips; tips of ventromedial primary pectinate fringes on segments 2-5 obliquely orientated, pointing towards midventral line; lateral terminal spines short and plump, length 12-15% of trunk length.

Description: Adult with head, neck and eleven trunk segments ( Figs. 8A, B View Fig , 9A View Fig , 10A View Fig ). See table 3 for measurements, and table 4 for positions of cuticular structures (sensory spots, glandular cell outlets, acicular spines, tubules and sieve plates).

Head consists of retractable mouth cone and introvert ( Figs. 10 View Fig A-C). Mouth cone with inner oral styles and nine outer oral styles. Exact number and arrangement of inner oral styles not observed. Each outer oral style composed of rectangular basal part and triangular distal part ( Fig. 10B View Fig ). Basal parts of outer oral styles alternate in size: five large anterior to odd sectors of introvert, and four slightly smaller ones in even sectors ( Figs. 10B View Fig , 11 View Fig ). Introvert composed of seven rings of spinoscalids and one ring of trichoscalids ( Figs. 10C View Fig , 11 View Fig ). Ring 01 includes ten primary spinoscalids, each with basal sheath and smooth long end-piece ( Fig. 10C View Fig ). Each basal sheath with three overlapping fringes. Proximal fringe extends into three flat projections, like a trident, covering next fringe. Middle fringe with two lateral projections overlapping end-piece. Distal fringe with five threads projecting between two projections of middle fringe. End-piece of primary spinoscalids is longest unit. Rings 02 and 04 with 10 spinoscalids; rings 03 and 05 with 20 spinoscalids. Spinoscalids in rings 02-05 similar in length. Rings 06 and 07 not examined with detail, but ring 06 with at least seven, and ring 07 with at least ten relatively short spinoscalids ( Fig. 11 View Fig ). Six trichoscalids attached with trichoscalid plate in sectors 2, 4, 5, 7, 8, and 10.

Neck with 16 placids ( Figs. 8A, B View Fig , 9A View Fig , 11 View Fig ). Midventral placid broadest (ca. 17 μm wide at base, ca. 12 μm wide at tip); remaining placids with similar size (ca. 10 μm wide at base, ca. 4 μm wide at tip).

Segment 1 consists of complete cuticular ring ( Figs. 8A, B View Fig , 9A View Fig ). Non-bracteate cuticular hairs densely cover entire segment. Paired, rounded subdorsal and laterodorsal sensory spots located close to anterior margin of segment ( Figs. 8A View Fig , 9C View Fig ). Rounded ventromedial sensory spots centered between anterior and posterior margins ( Figs. 8B View Fig , 10D View Fig ). Type-1 glandular cell outlets situated anteriorly in middorsal and lateroventral positions ( Figs. 8A, B View Fig , 9A, C View Fig ). Primary pectinate fringe conspicuous, with longer fringe tips, especially on ventral side ( Figs. 8A, B View Fig , 9 View Fig A-C).

Segment 2 also with complete cuticular ring ( Figs. 8A, B View Fig ), with thick pachycyclus at anterior margin ( Figs. 8A, B View Fig , 9 View Fig A-C). Entire cuticular surface, except anterior area, covered with bracteate cuticular hairs on this and following eight segments. Oval sensory spots in middorsal, laterodorsal, midlateral, and ventromedial positions ( Figs. 8A, B View Fig , 9 View Fig A-C, 10D). Unpaired type- 1 glandular cell outlet present in middorsal position ( Fig. 8A View Fig ). Paired type-1 glandular cell outlets close to anterior margin in ventromedial position on this and following eight segments ( Figs. 8B, D View Fig , 9A, B View Fig ). Type-2 glandular cell outlets in subdorsal, laterodorsal, and ventrolateral positions ( Figs. 8A, B View Fig , 9 View Fig A-C). Type-2 glandular cell outlets show single large pore in LM and SEM ( Figs. 9B, C View Fig ; see also figures 12A, B for type-2 glandular cell outlet on segments 6 and 8). Posterior margin of segment with primary pectinate fringe having long tips, with ventromedial tips obliquely orientated, pointing towards the midventral line ( Figs. 8A, B View Fig , 9 View Fig A-C).

Segment 3 and following eight segments consist of one tergal and two sternal plates ( Figs. 8A, B View Fig , 9A View Fig ). Each plate with thicker pachycycli in anterior area ( Figs. 8A, B View Fig , 9A, B View Fig ). Sensory spots in subdorsal, midlateral, and sublateral positions ( Figs. 8A View Fig , 9A View Fig ). Two unpaired type-1 glandular cell outlets present middorsally ( Fig. 8A View Fig ). Primary pectinate fringes on this and following two segments as on segment 2. Secondary pectinate fringes, consisting of single belt of minute teeth, visible on anterior dorsal plate in SEM observation, at least on this and following five segments ( Fig. 10G View Fig ).

Segment 4 with short middorsal acicular spine ( Figs. 8A View Fig , 10G View Fig ). Paired laterodorsal sensory spots and paired subdorsal type-2 glandular cell outlets present ( Figs. 8A View Fig , 10G View Fig ). Paired type-1 glandular cell outlets present paradorsally on this and following six segments. Fringe tips on dorsal, lateral, and ventral sides similar in length and width.

Segment 5 with lateroventral tubules ( Figs. 8B View Fig , 9D View Fig , 10D, F View Fig , 12A View Fig ). Paired sensory spots in subdorsal, midlateral, and ventromedial positions ( Figs. 8A, B View Fig , 9A View Fig , 10 View Fig D-F). Pair of type-2 glandular cell outlets in midlateral position ( Figs. 8A, B View Fig ).

Segment 6 similar to segment 5 except for absence of lateroventral tubules and presence of short sublateral acicular spines ( Figs. 8A, B View Fig , 9A, D View Fig , 10D, F View Fig , 12A, C View Fig ). Primary pectinate fringes of this and following three segments with long, conspicuous fringe tips.

Position

MD segment PD SD LD ML SL LV VL VM 1 gco1 ss ss gco1 ss 2 ss, gco1 gco2 ss, gco2 ss gco2 ss, gco1 3 gco1, gco1 ss ss ss gco1 4 ac gco1 gco2 ss gco1 5 gco1 ss ss, gco2 tu ss, gco1 6 gco1 ss ss, gco2 ac ss, gco1 7 gco1 ss ss, gco2 ac ss, gco1 8 gco1 ss ss gco2 tu gco1 9 gco1 ss ss tu si ss gco1 10 gco1 ss tu ss gco1 11 ss ltas (f), ps (m) lts

Segment 7 similar to segment 6.

Segment 8 with lateroventral tubules ( Figs. 8B View Fig , 9A, E View Fig , 12B View Fig ). Paired sensory spots in subdorsal and laterodorsal positions ( Fig. 7A View Fig ). Paired type- 2 glandular cell outlets in midlateral position ( Figs. 8A, B View Fig , 12B View Fig ).

Segment 9 with midlateral tubules ( Figs. 8A, C, D View Fig , 9F View Fig , 12B, D View Fig ). Paired subdorsal, laterodorsal, and ventrolateral sensory spots present ( Figs. 8 View Fig A- D, 9A, E). Sieve plates with oval sieve area and single posterior pore in sublateral position ( Figs. 8 View Fig B-D, 9E, 12B, D).

Segment 10 with long laterodorsal tubules in males, short laterodorsal tubules in females ( Figs. 8A, C View Fig , 9F View Fig , 12E, G View Fig ; Table 1). Paired subdorsal and ventrolateral sensory spots present ( Figs. 8 View Fig A-D, 12E, G). Primary pectinate fringe with shorter and thinner tips than preceding segments in middorsal to ventrolateral areas, and with tips similar in length to those of preceding segments in ventromedial area.

Segment 11 with short, plump lateral terminal spines ( Figs. 8 View Fig A-D, 9A, F, G, 10A, 12E-G). Pair of short lateral terminal accessory spines present in females ( Figs. 8B View Fig , 9G View Fig , 12E, G View Fig ), and three pairs of penile spines present in males ( Figs. 8D View Fig , 12F View Fig ). Cuticular hairs absent. Paired sensory spots in subdorsal position ( Figs. 8A, C View Fig , 12E View Fig ). Tergal plate partially divided at middorsal line from central to posterior part. Posterior edge of tergal plate projects laterally and ends in pointed tergal extensions ( Figs. 8 View Fig A-D, 12E).

Remarks: The combination of the arrangement of spines and tubules and the presence of large sieve plates assigns Echinoderes serratulus sp. nov to be a member of the Echinoderes coulli- group (see also DISCUSSION). Within the group, Echinoderes serratulus sp. nov. is similar to E. annae and Echinoderes hwiizaa Yamasaki and Fujimoto (2014) in having paired tubules on segment 9, and plump lateral terminal spines on segment 11 ( Yamasaki and Fujimoto 2014; SØrensen et al. 2016). It is also similar to Echinoderes aspinosus SØrensen et al. (2012) in having paired large sieve plates on segment 9, and the tips of the ventral primary pectinate fringes pointing towards the midventral line on segments 2-5 ( SØrensen et al. 2012).

Echinoderes serratulus sp. nov. differs from E. annae in having minute sublateral acicular spines on segments 6 and 7 ( SØrensen et al. 2016).

Echinoderes serratulus sp. nov. differs from E. hwiizaa in having a middorsal acicular spine on segment 4 and a conspicuous ventral primary pectinate fringe on segments 1 and 2, and in lacking midlateral tubules on segment 8 ( Yamasaki and Fujimoto 2014).

Echinoderes serratulus sp. nov. easily differs from E. aspinosus in having acicular spines and tubules on segments 4-10 ( E. aspinosus lacks any acicular spines and tubules on segments 4-10) ( SØrensen et al. 2012).