Valettietta synchlys, Stewart & Bribiesca-Contreras & Weston & Glover & Horton, 2024

Stewart, Eva C. D., Bribiesca-Contreras, Guadalupe, Weston, Johanna N. J., Glover, Adrian G. & Horton, Tammy, 2024, Biogeography and phylogeny of the scavenging amphipod genus Valettietta (Amphipoda: Alicelloidea), with descriptions of two new species from the abyssal Pacific Ocean, Zoological Journal of the Linnean Society 201 (4), pp. 1-23 : 8-13

publication ID	https://doi.org/ 10.1093/zoolinnean/zlae102
publication LSID	lsid:zoobank.org:pub:64C1409-DD34-4196-ACDB-B72DCE516D4A
DOI	https://doi.org/10.5281/zenodo.13786336
persistent identifier	https://treatment.plazi.org/id/34728786-B47F-FFA0-FC58-FEE6BA70FD99
treatment provided by	Plazi
scientific name	Valettietta synchlys
status	sp. nov.

Treatment

Valettietta synchlys sp. nov.

Figs 4–7 View Figure 4 View Figure 5 View Figure 6 View Figure 7

Valettietta cf. anacantha CCZ _056C— Bribiesca-Contreras et al. 2021: 1–15, figs 1, 4–6, table 1.

Valettietta cf. anacantha View in CoL — Mohrbeck et al., 2021: 1–12, figs 3, 5, 7, tables 2, 3.

ZooBank registration: http://zoobank.org/ F787152D-237B-4C45-A6DA-C7A366D9D62A

Holotype: Immature, 16.1 mm, carcass and 22 slides, ECDS _ AMP33 View Materials , NHMUK 2024.63 About NHMUK , Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), GoogleMaps expedition JC120, Station 039, depth 4230 m, genseq-1 COI ( PP841420 ), genseq- 1 16S ( PP849019 ), genseq-1 H3 ( PP855322 ), genseq- 1 28S ( PP848491 ). GoogleMaps

Paratypes: Immature, 9.23 mm, carcass, NHM_10315, NHMUK 2024.75 About NHMUK , Clarion-Clipperton Zone, Pacific Ocean (10.33 N, 117.17 W), expedition C7B, Station AT-03, depth 4292 m, genseq-2 COI ( PP841434 ), genseq-2 16S ( PP849032 ), genseq-2 H3 ( PP855323 ), genseq-2 28S ( PP848494 ). Mature male, 15.44 mm, carcass and 13 slides, ECDS-AMP32 , GoogleMaps NHMUK 2024.62 About NHMUK GoogleMaps , Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth 4230 m, genseq-2 COI ( PP841419 ), genseq-2 16S ( PP849018 ), genseq-2 H3 ( PP855321 ), genseq-2 28S ( PP848490 ). Immature, 11.33 mm, carcass, ECDS-AMP35 , GoogleMaps NHMUK 2024.65 About NHMUK GoogleMaps , Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth 4230 m, genseq-2 COI ( PP841422 ), genseq-2 16S ( PP849021 ).Mature male, 14.35 mm, carcass, ECDS-AMP38 , GoogleMaps NHMUK 2024.68 About NHMUK GoogleMaps , Clarion-Clipperton Zone, Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth 4230 m, genseq-2 COI ( PP841424 ), genseq-2 16S ( PP849024 ). Immature, 10.96 mm, carcass, ECDS-AMP16 , GoogleMaps NHMUK 2024.38 About NHMUK GoogleMaps , Clarion-Clipperton Zone, Pacific Ocean (16.891 N, 123.004 W), expedition JC120, Station 008, depth 4313 m, genseq-2 COI ( PP841404 ), genseq-2 16S ( PP849005 ) GoogleMaps .

Type locality: The Clarion-Clipperton Zone , central Pacific Ocean (17.321 N, 122.833 W), expedition JC120, Station 039, depth 4230 m GoogleMaps .

Material examined: See Supporting information, Table S2 View Table 2 .

Etymology: Synchlys, Greek, meaning mixed or ‘washed together by the waves’, alluding to the morphological characters of this species resembling a mixture of both Valettietta anacantha and Valettietta gracilis . Used as a noun in apposition.

Diagnosis: Coxa 1 not shorter or slightly shorter than coxa 2 and not strongly tapered distally. Gnathopods 1 and 2 weakly subchelate or simple, tapering distally, palms weakly defined or lacking. Gnathopod 1 propodus slender, tapering distally, carpus and propodus subequal. Gnathopod 2 propodus slender, length less than 5 × width. Basis of pereopod 7 with distinct posterodistal lobe. Maxilliped inner plate reaching halfway along palp article 1, with two short nodular robust setae on sub-apical medial margin. Inner ramus of uropod 1, 2, and 3 shorter than outer. Telson with four lateral spine groups, apices with a single subapical large robust seta and one small setae towards lateral margins.

Description ( Figs 4–7 View Figure 4 View Figure 5 View Figure 6 View Figure 7 ) Based on holotype, immature, 16.1 mm length, NHMUK 2024.63

Head: Head large, rostrum absent. Pale yellow eyes present upon collection but faded in ethanol ( Fig. 4 View Figure 4 ). Lateral lobe triangular, apically rounded. Antennae 1 ( Fig. 5 View Figure 5 ) elongate, 0.37 × as long as body length, flagellum 33-articulate, sparsely setose; accessory flagellum 6-articulate, reaching beyond end of basal conjoint article of flagellum; conjoint article subequal to length of peduncle article 1. Antennae 2 ( Fig. 5 View Figure 5 ) 0.78 × the length of Antennae 1, 0.28 × as long as body, flagellum 31-articulate, proximal flagellar articles with slender setae.

Mouthparts: Upper lip asymmetrically rounded with small apical notch, distal surface minutely setose (not illustrated). Mandible ( Fig. 6 View Figure 6 ) left incisor 8-dentate and closely applied to 8-dentate lacinia mobilis, spine row with 12 large spines interspersed with long plumose setae, left molar damaged (not illustrated), palp robust, article 1 small, article 2 elongate, broadened medially/ centrally, 14 A2 setae present, D2 setae present along distal half, B2 setae present proximally on medial margin. Article 3 oval, tapering distally; three A3 setae, two B3 setae, and five plumose E3 setae present, 19 plumose D3 setae on the posterodistal two-thirds of the margin. Right incisor 9-dentate, closely applied to 5-dentate lacinia, spine row with seven large spines interspersed with long plumose setae, molar strongly triturative; palp robust, article 1 small, article 2 elongate, broadened laterally/centrally, 21 A2 setae present, D2 setae present along distal half, B2 setae present proximally on lateral margin. Article 3 oval, tapering distally; two A3 setae, one central and two lateral B3 setae, and six plumose E3 setae present, 18 plumose D3 setae on the posterodistal two-thirds of the margin. Maxilla 1 ( Fig. 6 View Figure 6 ) inner plate with 20 marginal plumose setae, outer plate with 6/5 setal-tooth crown arrangement; palp large, article 2 lateral margin with two long slender setae, distal margin with 12 robust setae and row of 11 long submarginal setae. Maxilla 2 ( Fig. 6 View Figure 6 ) inner and outer plates subequal, distally setose, inner plate also with oblique row of 17 plumose facial setae. Maxilliped ( Fig. 6 View Figure 6 ) inner plate reaching halfway along palp article 1, with two short nodular robust setae at sub-apical medial margin; outer plate reaching halfway along palp article 2, inner margin with row of 19 short nodular robust setae grading to seven elongate and plumose setae distally; palp 4-articulate, article 4 with three robust setae distally, dactylus well-developed.

Pereon: Gnathopod 1 ( Fig. 5 View Figure 5 ) subchelate; coxa 1 shorter than coxa 2, slightly tapering distally, proximal and distal margins sub-rectangular, setose; carpus and propodus subequal, propodus not strongly elongate or tapering distally, palm acute, palmar margin straight and dentate, delimited by three bifid robust setae, dactylus overlapping palm, inner margin toothed with a few fine setules. Gnathopod 2 ( Fig. 5 View Figure 5 ) subchelate; anterodistal corner of coxa sub-rectangular, distal margin setose, basis curved, ischium extremely elongate (sub-equal to basis); carpus slightly shorter than propodus (1:0.85), both slender, propodus length 5 × width; palm acute, palmar margin straight and dentate, dactylus shorter than palm, not reaching single palmar defining robust seta, inner margin toothed with a few fine setules. Pereopod 3 ( Fig.7 View Figure 7 ) coxa rectangular, distal margin setose; basis curved; merus and propodus longer than carpus; all articles with long slender marginal setae. Pereopod 4 ( Fig. 7 View Figure 7 ) coxa very broad with large posteroventral lobe, posterodistal margin broadly rounded and setose; merus and propodus subequal in length and longer than carpus. Pereopods 5–7 ( Fig. 7 View Figure 7 ) coxa 5 broadly expanded and bilobate with posterodistal lobe largest, coxa 6 smaller than coxa 5 with posterior margin weakly lobate; coxa 7 smaller than coxa 6, not bilobate; basis broadly expanded distally, increasing from P5 to P7.

Pleon and urosome: Epimeron ( Fig. 5 View Figure 5 ) 1 broadly rounded, 2 subquadrate, 3 produced to a subacute tooth. Urosomite 1 with low rounded boss on dorsal margin. Uropods ( Fig. 7 View Figure 7 ) biramous, lanceolate. Uropod 1 inner ramus shorter than outer (1:0.8), with both margins lined by short robust setae, adjacent margins minutely serrate, apex of both rami with inset small setule; peduncle with one apicolateral robust seta, 11 dorsolateral setae, nine dorsomedial setae, and 10 longer ventrolateral setae. Uropod 2 inner ramus shorter than outer (1:0.75), both margins of outer ramus lined by short robust setae, inner margin of inner ramus lined by short robust setae, with one seta present on outer margin, adjacent margins minutely serrate, apex of both rami with inset small setule; peduncle with fewer setae than peduncle of uropod 1, one large robust seta present on peduncle at base of inner and outer ramus. Uropod 3 inner ramus shorter than outer (1:0.9), distal article of outer ramus approximately two-thirds length of proximal article, apex of proximal article with robust setae, inner margin minutely serrate; proximal inner margin of inner rami with four plumose setae, distal inner margin of inner rami minutely serrate; peduncle with long fine setae on inner margin, and three groups of two short setae on outer margin. Telson ( Fig. 7 View Figure 7 ) triangular, 75% cleft, apices with a single subapical large robust seta and one small setae towards lateral margins; lobes with four lateral robust setae.

Habitat and ecology: Valettietta synchlys is a benthopelagic scavenger species, currently known only from the central Pacific Ocean in the Clarion-Clipperton Zone, at abyssal depths of 4230–4313 m.

Remarks: Valettietta synchlys most closely resembles V. anacantha in the shape of coxa 1, gnathopods 1 and 2, and uropod 3, and has been recorded as V. cf. anacantha in recent literature ( Bribiesca-Contreras et al. 2021, Mohrbeck et al. 2021). Valettietta synchlys can be distinguished by characters of gnathopod 1, which more closely resembles that of V. gracilis , with propodus longer and more strongly tapering distally (shorter and broader, weakly tapering distally in V. anacantha ), and a longer carpus (shorter in V. anacantha ). It can be further distinguished by the angle of the anterodistal corner of coxa 2 which is sub-rectangular in V. synchlys (rounded in V. anacantha ). The basis of pereopod 7 is narrower with a distinct posterodistal lobe (in V. anacantha this is significantly more broadly rounded with a shallow, rounded posterodistal lobe). Body size ranged from 9.23–16.10 mm between examined specimens.