Rhynchomyzon rostrale, Lee, 2025
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https://doi.org/10.5281/zenodo.16967319 |
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https://treatment.plazi.org/id/382A6976-BA71-7150-FC8B-3D3A2EFD283D |
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treatment provided by |
Felipe |
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scientific name |
Rhynchomyzon rostrale |
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sp. nov. |
Rhynchomyzon rostrale View in CoL n. sp. ( Figs. 10 View Fig , 11 View Fig )
https://zoobank.org/urn:lsid:zoobank.org:act:7465BAE7-
783F-4886-8719-80C0AD6FBBCC
Type material. Holotype (♀, dissected and mounted on a slide; HNIBR IV7756 ) from washings of invertebrates, near Biyang-do, Jeju Island (33°24 ʹ 13.8 ʺ N, 126°12 ʹ 17.3 ʺ E), SCUBA, at a depth of 40 m, on a sandy bottom, collected by Tae Won Jung and Jong Guk Kim, on 23 June 2023. The holotype has been deposited in the Honam National Institute of Biological Resources ( HNIBR), Mokpo. GoogleMaps
Etymology. The specific name refers to the well-developed rostrum of this new species.
Female. Body ( Fig. 10A View Fig ) rather narrow, 920 μm long. Prosome 527 μm long, fusiform, consisting of cephalothorax and second to fourth pedigerous somites. Cephalothorax longer than wide (372× 355 μm). Third pedigerous somite with acutely pointed, projected posterolateral corners. Fourth pedigerous somite with deeply concave posterodorsal margin. Urosome ( Fig. 10B View Fig ) 5-segmented. Fifth pedigerous somite 104 μm wide, with membranous fringe along posterodorsal margin. Genital double-somite 1.2 times longer than wide (143 × 120 μm), consisting of broadened anterior third and narrower posterior two-thirds; broader anterior part with beaklike posterolateral process on each side; genital apertures positioned dorsolaterally at posterior region of broad anterior part near base of beaklike process. Three free abdominal somites 45 × 71, 30 × 67, and 35 × 68 μm, respectively. Anal somite with membranous fringe along posteroventral margin ( Fig. 10C View Fig ). Caudal rami divergent; each ramus ( Fig. 10C View Fig ) nearly rectangular, 2.84 times longer than wide (91 × 32 μm), bearing pointed process at inner and outer distal corners, armed with 6 setae, ornamented with thin setules on inner margin, fringed with membrane of uneven width along posteroventral margin.
Rostrum ( Fig. 10D View Fig ) large, beaklike, longer than wide. Antennule ( Fig. 10E View Fig ) slender, 282 μm long, 20-segmented; first, twelfth to seventeenth segments each with 1 seta; nineth segment with 5 setae; second to eighth segments each with 2 setae; eighteenth segment with 1 seta plus 1 aesthetasc; and terminal segment with 10 setae; setae mostly small and thin. Antenna ( Fig. 10F View Fig ) consisting of coxa, basis, 1-segmented exopod, and 2-segmented endopod; coxa short, unarmed; basis also unarmed, 73 μm long; exopod 22 × 8 μm, gradually broadened distally, with 1 subdistal and 2 distal setae, inner one of latter 2 setae annulated proximally; first endopodal segment 42 μm long, with row of setules on outer margin; second endopodal segment 24 μm long, with 1 proximal seta, 3 unequal distal setae, and slender, spiniform terminal claw of 73 μm long.
Oral cone ( Fig. 10G View Fig ) short, about 100 μm long, as long as wide. Mandible ( Fig. 10H View Fig ) consisting of stylet and palp; stylet 82 μm long, bearing 12 minute teeth at distal region, as arrowed in Fig. 10H View Fig ; palp 1-segmented, 13 μm long, tipped with 1 large pinnate seta (64 μm long) and 1 small naked seta. Maxillule ( Fig. 10I View Fig ) bilobed; outer lobe tipped with 1 rudimentary and 3 large, naked setae; inner lobe bent in middle, tipped with 1 rudimentary and 4 large, naked setae. Maxilla ( Fig. 11A View Fig ) 2-segmented; proximal segment with short excretory tube proximally; distal segment as arched claw bearing 1 small setule at 40% region of concave margin. Maxilliped ( Fig. 11B View Fig ) 6-segmented; armature formula 1, 1, 2, 0, 1, and 1 + claw; inner seta on second segment (basis) large; terminal segment 33 μm long; terminal claw 78 μm long.
Legs 1 ( Fig. 11C View Fig ), 2 ( Fig. 11D View Fig ), 3, and 4 ( Fig. 11F View Fig ) with 2-segmented protopod and 3-segmented rami; inner coxal seta well-developed, pinnate; outer seta on basis small, naked in leg 1 but distinct, pinnate in legs 2-4. Basis of leg 1 and 2 with tubercle on posterior surface. Basis of leg 1 with minute spinules at inner distal corner; inner distal seta thin, straight, spiniform. Basis of leg 2 with angle on subdistal inner margin (as indicated by arrowhead in Fig. 11D View Fig ). Leg 3 similar to leg 2, except bearing 1 spine and 4 setae on third endopodal segment ( Fig. 11E View Fig ). Leg 4 with small, spinulose tubercle on posterior surface of coxa ( Fig. 11F View Fig ). Armature formula for legs 1-4 as follows:
Coxa Basis Exopod Endopod Leg 1 0-1 1-1 I-1; I-1; III, 2, 2 0-1; 0-2; 1, 2, 3 Leg 2 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, 2, 3 Leg 3 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, I, 3 Leg 4 0-1 1-0 I-1; I-1; III, I, 4 0-1; 0-2; 1, I, 2
Leg 5 ( Fig. 10J View Fig ) consisting of protopod and free exopod; left and right protopod fused with each other, without any division between them, bearing 1 seta at outer distal corner and weakly bilobed, spinulose inner distal protrusion; exopodal segment slightly longer than wide, with pointed outer distal process, broad inner distal process, 2 pinnate seta on distal margin, and 1 scar of setal insertion on inner margin at places indicated by arrowheads in Fig. 10J View Fig . Leg 6 ( Fig. 11G View Fig ) represented by 1 pinnate and 1 small, naked setae on genital operculum.
Male. Unknown.
Remarks. The genus Rhynchomyzon comprises six known species. The closest relative of R. rostrale n. sp. is R. rubrovittatum Sars, 1915 , known from Norwegian waters. These two species share the unique feature of a large, point- ed process on the lateral margins of the genital double-somite (absent on the same place in other species) and the armature formula II, I, 4 (three spines plus four setae) on the third exopodal segment of leg 1 (contrasting with formula III, I, 4 in other species). However, they are distinct species: in the Norwegian species, the caudal ramus of the female is about 5.5 times longer than wide when measured the illustration of Sars (1915), the endopod of the antenna is 3-segmented, the inner seta on the basis of the maxilliped is small, and the basis of leg 1 lacks an inner distal seta. These significant differences clearly distinguish R. rostrale n. sp. from its most closely related species, R. rubrovittatum .
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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