Schisturella hansgeorgi, Larsen, 2007

Larsen, Kim, 2007, Amphipoda (Crustacea; Peracarida) from the Hydrothermal vent system of the Juan De Fuca Ridge, Escabana trough and Gorda ridge, Northeast Pacific. Part I. Lysianassidae and Sebidae, Zootaxa 1445 (1), pp. 1-26 : 7-12

publication ID	https://doi.org/ 10.11646/zootaxa.1445.1.1
publication LSID	lsid:zoobank.org:pub:7F76D8A3-51D1-4C24-B044-A8723CBBF05E
persistent identifier	https://treatment.plazi.org/id/935CDD7C-075D-FFB1-749F-AC1DFC1CF8BD
treatment provided by	Felipe
scientific name	Schisturella hansgeorgi
status	sp. nov.

Treatment

Schisturella hansgeorgi n. sp.

( Figs. 4–7 View FIGURE 4 View FIGURE 5 View FIGURE 6 View FIGURE 7 ).

Material examined. Holotype, male, 7.4 mm. ( FMNH # 13757 About FMNH ), Station code VOIJALV4045A, Dive 4045, Juan de Fuca Ridge , Endeavour Segment, 2 September 2004, 47°56.793’ N 129°05.838’ E. Depth 2213 m GoogleMaps . – Paratypes: 1 male (KMNH IvR 700249) 3 males 5.1-6.3 mm, 2 males 5.4 & 5.2 mm (dissected), 2 sex? 4.2 & 6.2 mm, (in very bad condition) ( FMNH # 12862 About FMNH ) .

Diagnosis. Eyes lacking. Epimeral plate 1 with small anteroventral tooth; epimeron 3 with posteroventral tooth. Urosome 1 with ventrodistal spine. Antenna 1 accessory flagellum first article as long as antenna1 article 4. Coxa 1 hidden under coxa 2. Coxa 1–2 with small tooth at the posteroventral corner. Gnathopod bases with long setae. Gnathopod 2 carpus longer than propodus and rectangular. Epimeral plate 1 without anteroventral tooth. Uropod 2 inner ramus with long spiniform seta before the point of constriction. Telson cleft 0.65 x length; lobes rectangular, with processes at corners and medial spine.

Etymology. Named in honor of the Lysianassidae expert Dr. Hans Georg Andres.

Description. Holotype, male 7.4 mm (habitus only); paratype male, 6.4 mm, (all appendages).

Body ( Fig. 4A View FIGURE 4 ). Laterally compressed. Eyes absent. Lateral cephalic lobe prominent, subacute. Body smooth. Epimeral plates 1-2 subrectangular, corners rounded, anterior margin concave, posterior margin convex. Epimeron 1 with small anteroventral tooth. Epimeron 3 larger, with posteroventral tooth. Urosomite 1 with small anterodorsal depression and ventrodistal spine.

Coxae ( Figs. 4A View FIGURE 4 , 7A–D View FIGURE 7 ). Coxa 1 ( Figs. 4A View FIGURE 4 , 7A View FIGURE 7 ) hidden under coxa 2, almost square, with small anteriodistal notch, w/h ratio 1.1. Coxae 2–4 increasing in size and protruding in anterior direction. Coxa 2 ( Fig. 7B View FIGURE 7 ) elongated, with small anteriodistal notch, w/h ratio 0.6. Coxa 3 ( Fig. 4 View FIGURE 4 AQ) slightly longer than C2, w/h ratio 0.5. Coxa 4 ( Fig. 6D View FIGURE 6 ), posteroventral lobe broad, blunt, posterior margin with strong excavation, w/h ratio 0.8. Coxa 5 ( Fig. 4A View FIGURE 4 , 7C View FIGURE 7 ) weakly equilobate, w/h ratio 1.1. Coxa 6 ( Figs. 4A View FIGURE 4 , 7D View FIGURE 7 ) square. Coxa 7 (Fig.) w/h ratio 1.2.

Antenna 1 ( Fig. 4B View FIGURE 4 ). Longer than head and pereonites 1–3 combined. Peduncular article 1 shorter than first article of accessory flagellum. Peduncular article 2 and 3 subequal. Flagellum longer than peduncle, with 13–15 articles, without calceoli. Callynophore well developed. First article of accessory flagellum as long as flagellum article 1. Accessory flagellum 4-articulate, marginally longer than peduncle.

Antenna 2 ( Fig. 4C View FIGURE 4 ). 1.5 times as long as antenna 1. Peduncular article 1 fused to the head. Peduncular article 2 gland cone with blunt apex. Peduncular article 3 longer than article 2, with acute processes on both margins. Peduncular article 4 subequal to article 5, both lined anteromedially with brush setae. Flagellum with more than 40 articles without calceoli.

Mouthparts. Epistome-labral complex ( Fig. 5A View FIGURE 5 ): upper lip with complicated lobation, pointed with large blunt process near separation with epistome, separated from the epistome by deep sinus, setose. Mandibles ( Fig. 5 View FIGURE 5 B-C) incisor well developed, triangular smooth; spine row with 3 spiniform setae. Molar fairly broad, triturative. Palp attached level with molar, 3-articulate, article 1 short and naked, article 2 about 4 times as long as article 1, with 11 submarginal posteroventral D2 setae. Article 3 half as long as article 2 but wider, with 14 D3 setae, without E3 and A3-seta. Left mandible lacinia mobilis triangular and partly fused with incisor. Lower lip ( Fig. 4D View FIGURE 4 ) outer lobes with prominent anterior setulation and very weak posterior setulation. Maxilla 1 ( Fig 5D View FIGURE 5 ) inner plate slender, with 2 bipinnate apical setae, outer plate ( Fig. 5D View FIGURE 5 1 View FIGURE 1 ) with spiniform setae in 6/5 crown arrangement, STA–STD distally cuspidate, ST1–4 medially cuspidate, ST5–6 almost smooth, ST7 marginally cuspidate, widening distally. Palp ( Fig. 5D View FIGURE 5 2 View FIGURE 2 ) biarticulate, distal article about 4 times as long as proximal article, with 11 stout spiniform and 1 simple distal setae. Maxilla 2 ( Fig. 5E View FIGURE 5 ) plates subequal, with apical and subapical simple and bipinnate setae, inner plate also with proximal inner setules Maxilliped ( Fig. 5F View FIGURE 5 ) inner plates reaching end of palp article 1, rectangular with many bipinnate setae along inner margin transversing across to the outer corners, apical margin with 3 short denticles. Outer plates subovate, reaching end of palp article 2, apically with denticles, fully lined medially with denticles, outer margin setulated, with transverse row of small setulated setae. Palp articles not elongated; article 1 with 2 lateral and medial setae article 2 with 2 distal setae; article 3, with several medial and apical inner setae and isolated lateral apical setae; article 4 with 1 proximal and 3 distal setae.

Gnathopod 1 ( Fig. 6A, A View FIGURE 6 1 View FIGURE 1 ). Subchelate. Basis slender, as long as merus, carpus and propodus combined, anterior margin strongly setose with tuft of ventrodistal setae. Ischium and merus of subequal size and with sparse ventrodistal setation. Carpus longer than propodus, ventrally lobate, with ventral setulation and isolated dorsodistal setae. Propodus rectangular, longer than ischium with row of ventral setae, tuft of dorsal setae at dactylus insertion and transverse row of setae. Palm transverse with small setae, palmar corner defined by one lateral and one medial strong distal spiniform setae. Dactylus with 1 outer seta.

Gnathopod 2 ( Fig. 6B, B View FIGURE 6 1 View FIGURE 1 ). Minutely subchelate. Basis weakly setose, twice as long as ischium. Ischium longer than merus, with sparse ventrodistal setation. Merus widening distally, shorter than carpus, with dorsodistal setation. Carpus twisted in illustration, longer than merus, with small ventral lobe, with pineapple cushion, with turf of dorsodistal setae. Propodus ( Fig. 6B View FIGURE 6 1 View FIGURE 1 ) mitten shaped, with pineapple cushion and scale-like

setae on both distal margins, with ventral and dorsodistal turf of pinnate setae. Palm shape is obtuse Dactylus minute with 1 dorsal seta and on ventral tooth.

Pereopods ( Fig. 6C–F View FIGURE 6 ). Pereopod 3 ( Fig. 6C View FIGURE 6 ) basis slightly shorter than ischium, merus and carpus combined, naked except for ventrodistal tuft of setae. Ischium half as long as carpus, with ventral setae. Merus nearly half as long as basis, with ventral setae. Carpus narrower than merus and ischium, with ventral setae. Propodus subequal to carpus, with shorter ventral spine-like setae and dorsodistal setae. Dactylus less than half as long as propodus, with 1 small bipinnate dorsal seta. Pereopod 4 ( Fig. 6D View FIGURE 6 ) as pereopod 3. Pereopod 5 ( Fig. 6E View FIGURE 6 ) basis expanded and weakly setose, posteroventral lobe of prominent. Ischium half as long as merus sparsely setose and almost exclusively on anterior margin. Merus wider than carpus, with slight dorsal extension, anterior margin setose. Carpus rectangular, anterior margin with sparse setation. Dactylus less than half as long as propodus, without setae. Pereopod 6 ( Fig. 6F View FIGURE 6 ) merus-propodus more elongated than pereopod 5. Dactylus with 1 seta. Pereopod 7 missing or damaged on all specimens.

Brood plates. No females found.

Gills ( Fig. 7G View FIGURE 7 ). Present on pereopods 2-7, large, pleated.

Pleopods ( Fig. 4E View FIGURE 4 ). Peduncle with 2 retinaculae. First article of inner rami with bluntly bifurcated setae; first article of outer ramus 1.4 times as long as inner ramus, both rami with 14–16 articles.

Uropods ( Fig. 5G–J View FIGURE 5 ). Uropod 1 ( Fig. 5G View FIGURE 5 ) with spiniform setae on both peduncle and rami. Rami clearly shorter than peduncle, inner ramus marginally (about 10%) shorter than outer. Uropod 2 ( Fig. 5H View FIGURE 5 ) shorter but stouter than uropod 1, peduncle and rami with spiniform setae. Outer ramus longer than peduncle and inner ramus. Inner ramus as long as peduncle, with deep constriction beyond insertion position of long spiniform seta. Uropod 3 ( Fig. 5I View FIGURE 5 ) biramous. Peduncle shorter than rami, with several robust distal spiniform setae. Outer ramus biarticulate, proximal article 1.5 times as long as distal article, with spiniform setae and small spiniform setae on inner apical margin, with 1 large spiniform seta on both margins at articulation; distal article with small spiniform setae on inner margin. Inner ramus shorter than outer, with spiniform setae and small spiniform setae on inner apical margin,

Telson ( Fig. 4A View FIGURE 4 , 5J View FIGURE 5 ). Deeply cleft, 0.65 x length, extending beyond peduncle of uropod 3. Lobes truncate apically, with tiny process laterally and medially; apical margin line sloping medially, bearing one spiniform and two simple setae laterally.

Remarks. Schisturella is currently comprised of 12 recognized species (excluding the new one described below) plus 2 subspecies. This species can be separated from: S. cocula J.L. Barnard, 1966 by lack of eyes. From S. dorotheae ( Hurley, 1963) by the long first article of the antennule accessory flagellum. From S. pulchra ( Hansen, 1888) by the lack of eyes and presence of a long spiniform seta before the point of constriction on uropod 2 inner ramus. From S. adversicola (K.H. Barnard, 1925) by the lack of eyes and by the rectangular telson lobes. From S. tracalero (J.L. Barnard, 1966) by the square coxa 1. From S. spinirama Hendrycks & Conland, 2003 by the presence of an acute tooth on the posteroventral corner of epimeron 3. From S. abyssi ( Chevreux, 1926) + subspecies S. abyssi tasmanensis J.L. Barnard, 1961 and S. rotundata (K.H. Barnard, 1925) by the acute tooth on the posteroventral corner of epimeral plate 3 and the large upper lip lobe extending from below the epistome. From S. zopa J.L. Barnard, 1966 by the gnathopod bases anterior margin with row of long setae and by the many spiniform setae on the uropods. From S. robusta (J.L. Barnard, 1961) + subspecies S. robusta cedrosiana J.L. Barnard, 1967 by the epimeron 3 tooth; and a more deeply cleft telson with apical armament of telson lobes. From S. totorami J.L Barnard, 1967 by the pointy upper lip; the smooth anteriodistal process on epimeron 1 and pointy tooth posteroventral on epimeron 3. From S. grabensis J.L. Barnard, 1967 by the small coxa 1 hidden under coxa 2; the pointy shape of the upper lip; the presence of anteriodistal process of epimeron 1; also the shape of the gnathopod 1 propodus is different, rectangular and with a straight distal edge in the new species, not transverse as in S. grabensis . Unfortunately none of the specimens of S. hansgeorgi display a full complement of appendages.