Hebefustis vecino, Kaiser, Stefanie, 2014

Kaiser, Stefanie, 2014, New species of Hebefustis Siebenaller & Hessler 1977 (Isopoda, Asellota, Nannoniscidae) from the Clarion Clipperton Fracture Zone (equatorial NE Pacific), Zootaxa 3784 (2), pp. 101-119 : 114-118

Hebefustis vecino sp. n.

( Figs 8–9 )

Type fixation. Holotype, non-ovigerous female, here designated.

Material examined. Holotype: 1 female (non-ovigerous), CCFZ, equatorial NE Pacific, BIONOD expedition, RV L’Atalante, EBS, BIO 12-51 (start: 12°29.50’N, 118°13.47’, 4226 m; 12°31.43’N, 118°13.41’W, 4234 m) date: 11/04/2012, ZMH-K-43954

Type locality. CCFZ, Equatorial NE Pacific, 4226 m.

Distribution. Only known from type locality.

Etymology. The name (nom., masculine) comes from the Spanish word for ‘neighbouring’ and emphasizes both the new species’ morphological resemblance as well as the close vicinity of its type locality to H. juansenii sp. n.

Diagnosis. Maxilliped epipodite reaching mid of palpal article 3. Pereonites anterior margins 1 – 4 frontally directed, rounded; pereonite 2 with few simple setae laterally; pereonite 4 anterior margin slightly concave; pereonites 6 and 7 lateral margins rounded. Pleotelson with two pairs of posterolateral spines; proximal pair inserting 0.7 from anterior margin. Uropods not extending beyond pleotelson posterior margin.

Remarks. All appendages of holotype female were drawn in situ to minimize damage of the specimen.

Description of holotype female. Habitus ( Figs 8 A, D, 9A). Body length 3.7 pereonite 3.0 width. Surface of dorsal cuticle with numerous setules. Pereonites 1–3 increasing in length posteriorly; pereonite 1 width 0.9 pereonite 2 width; pereonites 2–3 with frontally directed rounded antero-lateral margins. Pereonites 2 and 3 of equal width, widest; pereonite 2 width 3.3 length; pereonite 3 longest, width 2.5 length. Pereonites 4 width 0.9 pereonite 2 width, width 3.2 length, with slightly convex anterior margin. Pereonites 5–7 of similar width; pereonites 6 and 7 medially fused, with rounded lateral margins; pereonite 6 with convex anterior margin. Pleotelson 0.23 body length, length 0.9 width; width 0.9 pereonite 2 width, with two pairs of well-developed posterolateral spines; proximal pair inserting 0.7 from anterior margin, distal pair inserting 0.9 from anterior margin; posterior margin strongly convex; anterior margin straight. Anus ( Fig. 2 D) covered by anus valves laterally. Uropods inserting closely to the anus valves, short in relation to pleotelson, not projecting beyond posterior margin. Operculum length 0.7 pleotelson length (ventrally measured).

Cephalothorax ( Figs 8 A, 9A). Length 0.9 width. Anterior margin slightly rounded, posterior and lateral margins straight. Antennae inserting frontolaterally in a deep fold.

Antennula ( Fig. 8 B). Length 0.11 body length; with 5 articles. First article circular and broadest; with 1 simple seta distolaterally; second article length 1.5 article 1 length, width 0.4 length; with 2 broom setae distally. Article 3 and 4 equal in length, length 0.2 article 2 length; article 3 with 2 simple setae distally, article 4 with 1 small broom seta distally. Article 5 length 4.8 article 4 length, length 8.0 width; with 1 long aesthetasc and 2 simple setae terminally.

Antenna ( Fig. 8 B). Broken off, only podomere articles 1–4 present. Podomere articles 1–4 short; article 3 with 1 robust spine tipped with a small setule and 2 simple setae distally.

Maxilliped ( Fig. 9 B). Left and right maxilliped connected by 3 coupling hooks. Epipodite smooth, triangular, slender, length 3.1 width, reaching mid of palpal article 3. Palpal article 1 short, width 2.5 length; with 1 robust sensory seta laterally. Article 2 longest, length 1.8 article 1 length, width 1.5 length; with 3 simple setae laterally, with 5 simple setae distally. Article 3 length 0.8 article 2 length, width 1.5 length, distal margin saw-toothed; with 5 robust sensillae. Article 4 length 1.5 article 3 length, width 0.5 length; with 3 slender setae distally. Article 5 length 0.6 article 1 length, twice as long as wide; with 3 slender setae terminally. Endite distal margin with some robust, dentate setae and several fine setae laterally. Protopod coxa quadrangular; length 3.2 width.

Pereopod I ( Fig. 9 C) more robust than pereopod II. Basis length 5 width. Ischium about half basis length, length 1.9 width. Merus length 0.6 ischium length, length 1.5 width. Carpus length 1.9 merus length, length 2.7 width; with 2 simple setae dorsally, ventral margin with numerous small setae, membranously embedded, and 4 robust unequally bifid setae in between (1 broken off), with 1 long simple seta distoventrally. Propodus length 0.8 carpus length, 2.5 width; with 3 simple setae dorsally, with numerous small setae, membranously embedded and 2 robust unequally bifid setae in between ventrally. Dactylus length 0.4 propodus length, twice as long as wide; with 4 slender setae medially. Dorsal claw about as long as dactylus; with 2 long, slender setae between dorsal and ventral claw.

Pereopod II ( Fig. 9 D). Basis length 5.6 width; with 1 simple seta ventrally. Ischium half basis length, length twice width; with 1 simple seta dorsally. Merus length 0.75 ischium length, length 1.8 width; with 2 robust setae distodorsally, with 2 more slender setae ventrally. Carpus length 2.3 merus length, length 4.6 width; with 1 simple seta dorsally, with 1 broom seta distodorsally, with numerous small setae, membranously embedded and 6 stout unequally bifid setae in between ventrally. Propodus length 0.8 carpus length, length 5.5 width; with 4 simple setae dorsally, with numerous small setae, membranously embedded, and with 4 stout unequally bifid setae ventrally. Dactylus length one-third propodus length, length 3.1 width; with 3 simple setae medially. Dorsal claw length 0.8 dactylus length; with 2 slender setae between dorsal and ventral claw.

Pereopod III ( Fig. 9 E). Basis length 5.4 width. Ischium length 0.6 basis length, length 2.4 width; with 1 simple seta dorsally. Merus length 0.6 ischium length, length 1.8 width. Carpus length 2.4 merus length, length 5.2 width; with 2 simple setae dorsally, with numerous small setae, membranously embedded and 7 stout unequally bifid setae in between ventrally. Propodus length 0.9 carpus length, length 5.8 width; with 3 simple setae dorsally, with 1 broom seta distodorsally, with numerous small setae, membranously embedded, and with 4 stout unequally bifid setae ventrally. Dactylus length one-third of propodus length, length 3 width; with 3 simple setae medially. Dorsal claw about as long as dactylus; with 2 slender setae between dorsal and ventral claw.

Operculum (female pleopod 2; Fig. 8 C, D). About as long as wide. Lateral and posterior margin rounded; with numerous (> 50) simple setae.

Uropods ( Fig. 8 D, E). Biramous. Protopod trapezoid, nearly as long as wide; with 2 simple setae distally. Exopodite about as long as protopod, length 3.2 width; with 1 simple seta terminally. Endopodite length 1.3 exopodite length; with 7 simple setae laterally, with 3 broom setae (one broken off) and 1 long, slender simple seta terminally.

Remarks. Hebefustis vecino sp. n. is only represented by a single female specimen, which highlights a general problem in deep-sea taxonomy. Many deep-sea species are just recorded from a single locality with one or two individuals (e.g., Brandt et al. 2005; Brandt et al. 2007) representing a major impediment for both taxonomic and molecular examinations (e.g., with regard to the assessment of intraspecific variation).

Although Hebefustis vecino sp. n. shares many features with H. juansenii sp. n., it, nevertheless, shows some significant differences: maxilliped epipodite reaching mid of palpal article 3 (vs. upper third of palpal article 2 in H. juansenii ), maxilliped palpal article 2 with a strong sensory seta distally (vs. no such seta present); pereonite 2 lacking a robust spine on anterolateral margin (vs. robust spine present); pereonite 4 anterior margin slightly concave (vs. convex).

Key to the species of Hebefustis (modified from Kaiser 2008)

1a. Pereonite 6 and 7 with acute, distally directed posterolateral margins........................................... 2

1b. Pereonite 6 and 7 with rounded posterolateral margins....................................................... 7

2a. Male pleotelson with rounded posterior margin............................................................. 3

2b. Male pleotelson angularly shaped............................................................... H. cornutus

3a. Pereonite 2 in female and/or male with a robust seta or spine on the anterolateral corner............................. 4

3b. Pereonite 2 in female and/or male without a seta or spine on the anterolateral corner.................... H. hexadentium

4a. Operculum length ≤ 0.2 body length...................................................................... 5

4b. Operculum length> 0.3 body length............................................................... .. H. vitjazi

5b. Antennula article 5 proximally and distally of equal width..................................................... 6

5a. Antennula article 5 increasing in width distally....................................................... H. dispar

6a. Male pleopod 1 distal margin with ≤ 3 setae, male pleopod 2 outer margin with ≥ 11 setae.................... H. hirsutus

6b. Male pleopod 1 distal margin with ≥ 4 setae, male pleopod 2 outer margin with ≤ 5 setae................. H. clareolithis

7a. Pleotelson with one pair of posterolateral spines............................................................ 8

7b. Pleotelson with two pairs of posterolateral spines.......................................................... 12

8a. Pleotelson posterolateral spines ≥ 0.8 from anterior margin, body length <3.8 width................................ 9

8b. Pleotelson posterolateral spines ≤ 0.6 from anterior margin.................................................... 10

9a. Antennula article 5 length approximately article 2 length................................................. H. par

9b. Antennula article 5 length 0.7 article 2 length......................................................... H. alleni

10a. Operculum distal margin softly rounded.................................................................. 11

10b. Operculum distal margin straight................................................................. H. robustus

11a. Antennula article 5 length 4.1 width; pleotelson posterior margin rounded.................................. H. vafer

11b. Antennula article 5 length 3.2 width; pleotelson posterior margin tapering distally........................ H. mollicellus

12a. Pereonites 1–4 anterolateral margins rounded; uropods not visible from dorsal view............................... 13

12b. Pereonites 1–4 anterolateral margins acute; uropods clearly projecting beyond pleotelson posterior margin..... H. primitivus

13a. Pereonite 2 antero-lateral margin with a strong spine in both male and female, maxilliped epipodite reaching upper third of pal- pal article 2............................................................................ H. juansenii sp. n.

13b. Pereonite 2 antero-lateral margin without a strong spine, maxilliped epipodite reaching mid of palpal article 3..................................................................................................... H. vecino sp. n.

Figures

FIGURE 2. Hebefustis juansenii sp. n.; A – D, holotype female (ZMH – K – 43951); A, habitus, dorsal view. B, pleotelson, ventral view. C, uropod. D, operculum. Scale bar: A – B = 500 Μm, C – D = 250 µm.

FIGURE 8. Hebefustis vecino sp. n.; A – E, holotype female (ZMH-K- 43954); A, habitus, dorsal view. B, antennula, antenna podomere articles 1 – 4; C, operculum; D, pleotelson, ventral view. E, uropod. Scale bar: A, D = 500 Μm, B – C, E = 250 µm.

FIGURE 9. Hebefustis vecino sp. n.; A – D, holotype female (ZMH-K- 43954); A, habitus, dorsal view. B, maxilliped. C – E, pereopods I – III, detail: dorsal and ventral claw. Scale bar: A = 500 Μm, B – E = 250 µm.