Leipsuropus seisuiae, Matsumoto & Kajihara & Kakui, 2023

Matsumoto, Yu, Kajihara, Hiroshi & Kakui, Keiichi, 2023, A new species of Leipsuropus Stebbing, 1899 (Amphipoda: Podoceridae) from Japan, Nauplius (e 2023005) 31, pp. 1-8 : 2-6

publication ID	https://doi.org/ 10.1590/2358-2936e2023005
publication LSID	lsid:zoobank.org:pub:D4641240-C79E-471D-8F7C-8A2DA4AA04A8
DOI	https://doi.org/10.5281/zenodo.10914365
persistent identifier	https://treatment.plazi.org/id/0F13E56C-CDA3-4514-95CC-09F621D1DBA8
taxon LSID	lsid:zoobank.org:act:0F13E56C-CDA3-4514-95CC-09F621D1DBA8
treatment provided by	Felipe
scientific name	Leipsuropus seisuiae
status	sp. nov.

Treatment

Leipsuropus seisuiae View in CoL sp. nov.

( Figs. 2–6 View Figure 2 View Figure 3 View Figure 4 View Figure 5 View Figure 6 )

Zoobank: urn:lsid:zoobank.org:act:0F13E56C-CDA3-4514-95CC-09F621D1DBA8

Type material. Holotype: male, 3.4 mm, ICHUM6353 View Materials ; TR/ V “Seisui-maru”, Stn. 1, Kumano Sea , Northwestern Pacific (34°06.92’N 136°42.73’E to 34°04.98’N 136°42.25’E), 340– 338 m depth, biological dredge, 7 November 2017, Y. Matsumoto and K. Kakui coll. GoogleMaps

Diagnosis (male). Pereonites 2–5 each with five narrow spiniform projections on tergal plate. Pereonites 6 and 7 segmented. Telson with dorsal tubercle. Gnathopod-2 palm with small, proximal, denticulate projection.

Description of holotype. Body( Figs.2 View Figure 2 , 3A–C View Figure 3 , 6D View Figure 6 ) 3.4 mm long, depressed. Head with mid-dorsal spiniform projection, pair of dorsolateral spiniform projections, and pair of ventral projections at insertion of antenna 2. Pereonite 1 with 2 mid-dorsal spiniform projections and pair of lateral spiniform projections.Pereonites2–7 segmented, each with mid-dorsal spiniform projection, pair of dorsolateral spiniform projections, and pair of lateral spiniform projections. Pleonites 1–2 each with mid-dorsal spiniform projection and pair of dorsolateral projections.Pleonite3 without projection. Urosomites 1–3without projection;urosomite1 with posterodorsal simple seta. Telson ( Figs. 3B View Figure 3 , 6D View Figure 6 ) linguiform, with dorsal tubercle bearing dorsal simple seta.

Antenna 1 ( Fig. 4A View Figure 4 ) with peduncular article 1 having ventral setulose setae and dorsal bifurcate setae; other parts lost. Antenna 2 ( Fig. 4B View Figure 4 ) with peduncular articles 1–2 (fused) having distolateral projection and antennal gland cone directed ventrodistally; peduncular article 3 with ventral setulose setae and dorsal bifurcate setae; other parts lost.

Upper lip ( Fig. 4C View Figure 4 ; partly broken) ventrally setulated, with ventral hollow. Epistome ( Fig. 4D View Figure 4 ) produced anteriorly. Mandibles ( Fig. 4E, E View Figure 4 1, F, F1 View Figure 1 ) with incisor bearing 5 cusps; lacinia mobilis with 3 cusps; subdistal region with 3 (left) or 2 (right) accessory blades and 3 (left) or 1 (right) plumose seta; molar with plate-like structure bearing pectinate margin. Palp with naked article 1; article 2 with medial setulose setae; article 3 distally expanded, with setulose setae in distal half. Lower lip ( Fig. 4G View Figure 4 ) with developed inner lobes and mandibular processes; distal region of inner and outer lobes covered with thin setae. Maxilla 1 ( Fig. 4H View Figure 4 ) with vestigial inner plate; outer plate with 8 distal robust setae (6 bifurcate, 2 simple). Palp with naked article 1; article 2 with 7 distal robust setae (1 broken, 3 serrate, 3 simple), ventral simple seta, and 3 dorsal setulose setae.Maxilla 2 ( Fig. 4I View Figure 4 ) with inner and outer plates having distal setulose setae and covered with thin setae. Maxillipeds ( Fig. 4J, J View Figure 4 1 View Figure 1 ) with inner plate bearing 6 distal setulose setae and 3 distal short robust setae; outer plate with 4 distal setulose setae and 5 medial robust setae and several medial simple setae. Palp with4 articles; article 1 naked; article 2with distal and medial setulose setae; articles 3–4 with setulose setae on almost all surfaces.

Gnathopod 1 ( Figs. 3A View Figure 3 , 5A, A View Figure 5 1 View Figure 1 ) subchelate. Coxa with slight lateral projection. Basis with 1 anterior and 1 posterodistal simple setae. Ischium with posterodistal setulose setae. Merus with posterior setulose setae. Carpus with 1 medial and several posterior setulose setae. Propodus with setulose setae on almost all margins; palmar margin slightly concave, with proximomedial 4 robust setulose setae. Dactylus slightly curved posteriorly, with 2 posterosubdistal denticles.

Gnathopod 2 ( Figs. 3C View Figure 3 , 5B, B View Figure 5 1 View Figure 1 ) subchelate. Coxa with lateral projection. Basis with 1 mid-posterior and 3 posterodistal simple setae and lateral anterodistal spiniform projection. Ischium with 2 posterodistal simple setae. Merus with 5 posterodistal simple setae and posterodistal spiniform projection. Carpus short, with simple setae on antero- and posterodistal corners. Propodus ovate, with simple setae on almost all margins; palmar margin with proximal small denticulate projection, proximal bifurcate robust seta, mid-plumose seta, and 11 robust setae. Dactylus curved posteriorly.

Pereopod 3 ( Figs. 3A, C View Figure 3 , 5C View Figure 5 ) 2.33 mm long, with length ratio of basis, ischium, merus, carpus, and propodus 1.00:0.24:0.64:1.01:1.37 (tip of dactylus broken). Coxa pointed laterally. Basis with anterior and posterior simple setae.Ischium with posterodistal simple seta. Merus with posterior simple setae, mid-anterior thick seta and anterodistal bifurcate thick seta. Carpus with anterior, posterior, and distal simple setae and mid-anterior, anterodistal, and posterodistal thick setae. Propodus with anterior simple setae and anterior, posterior, and distal thick setae. Dactylus slightly curved, with 2 anterior simple setae and mid-anterior plumose seta. Pereopod 4 ( Figs. 3A View Figure 3 , 5D View Figure 5 ) 2.32 mm long, with length ratio of articles from basis to propodus 1.00:0.25:0.73:1.16:1.50 (tip of dactylus broken). Similar to pereopod 3 except: basis with lateral anterodistal spiniform projection; dactylus without anterior simple setae. Pereopod 5 ( Figs. 3A View Figure 3 , 5E View Figure 5 ) 2.34 mm long, with length ratio of articles from basis to dactylus 1.00:0.27:0.61:1.30:1.65:1.08. Similar to pereopod 4. Pereopod 6 ( Figs. 3A View Figure 3 , 5F View Figure 5 ) 2.45 mm long, with length ratio of articles from basis to dactylus 1.00:0.27:0.68:1.23:1.63:1.05. Similar to pereopod 5. Pereopod 7 ( Figs. 3A View Figure 3 , 5G View Figure 5 ) 2.57 mm long, with length ratio of articles from basis to dactylus 1.00:0.28:0.68:1.22:1.65:1.13. Similar to pereopod 6.

Pleopods 1–3( Fig. 6A–C View Figure 6 ) 0.66 mm, 0.80 mm, 0.76 mm long, respectively. Peduncle with 4 mediodistal coupling hooks. Each segment of both rami bearing 1–3 plumose setae.

Uropod 1 ( Fig. 6D View Figure 6 ) biramous. Peduncle with 1 distolateral and 2 mediodistal robust setae. Inner ramus with 3 lateral, 3 medial and 4 distal robust setae. Outer ramus with 2 lateral, 1 medial, and 2 distal robust setae. Uropod 3 ( Fig. 6D, E View Figure 6 ) curled, with distal thin setae and 3 dorsal simple setae.

Etymology. The specific name is a noun in the genitive case and derived from TR/ V “Seisui-maru”, the vessel from which the type specimen was collected.

Type locality. Kumano Sea , Japan, Northwestern Pacific (34°06.92’N 136°42.73’E to 34°04.98’N 136°42.25’E), 340– 338 m depth GoogleMaps .

Distribution. So far known only from the type locality.

Remarks. Leipsuropus seisuiae sp. nov. is the fifth named species in Leipsuropus . Pereonites 2–7 of male L. seisuiae sp. nov. each has five projections on the tergal plate: one dorsal, a pair of dorsolateral, and a pair of lateral projections. This condition was also found in male L. hongi , but L. seisuiae sp. nov. is distinguished from L. hongi by: i) dorsal projection on the pereonites is narrow and spiniform (broad, keel-like in L. hongi ), ii) gnathopod-2 palmar margin has one small,proximal, denticulate projection (one wide and two large triangular projections in L. hongi ), and iii) the telson has a dorsal tubercle (no tubercle in L. hongi ) ( Ariyama, 2012).Differences among congeners including L. seisuiae sp. nov. in a combination of five character states are presented in Tab. 1. A View Table 1 key to world Leipsuropus males is given below.