Hebefustis juansenii, 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 : 104-110

Hebefustis juansenii sp. n.

( Figs 2–7 )

Type fixation. Holotype, ovigerous female, 3.4 mm, designated here.

Material examined. Holotype: 1 female holotype (ovigerous), 3.4 mm, CCFZ, equatorial NE Pacific, BIONOD expedition, RV L’Atalante, EBS, station BIO 12-33 (start: 11°49.17’N, 117°03.73’W, 4133 m; end: 11°51.91’N, 117°03.13’W, 4127 m), date: 07/04/2012, ZMH-K-43951. Paratypes: 1 adult male, 2.2 mm, CCFZ, equatorial NE Pacific, BIONOD expedition, RV L’Atalante, EBS, from the same station as holotype, ZMH-K- 43952; 1 Manca 1, CCFZ, equatorial NE Pacific, BIONOD expedition, RV L’Atalante, EBS, BIO 12 – 43 (start: 11°45.52’N, 117°34.33’, 4358 m; 11°48.34’N, 117°31.95’W, 4360 m), date: 09/04/2012, ZMH-K-43953.

Type locality. CCFZ, equatorial NE Pacific, 4127 – 4360 m.

Distribution. Only known from type locality.

Etymology. The name is masculine and dedicated to a friend.

Diagnosis. Maxilliped epipodite reaching upper third of palpal article 2. Pereonites anterior margins 1–4 frontally directed, rounded; pereonite 2 anterolateral margin bearing a robust spine both in male and female; pereonites 6 and 7 lateral margins rounded; pereonite 6 anterior margin strongly convex. Pleotelson with two pairs of posterolateral spines; proximal pair inserting 0.6 from anterior margin. Uropods not extending beyond pleotelson posterior margin. Male pleopod 1 lateral lobes rounded, distal margin straight.

Remarks. Due to the low number of individuals in the new species, all appendages of holotype female were drawn in situ to minimize damage of the specimen.

Description of holotype female. Habitus ( Figs 2 A, D, 3A). Body length 3.3 pereonite 3 width. Dorsal cuticle surface with numerous setules. Pereonites 1–3 of similar length; pereonite 1 width 0.8 pereonite 2 width; pereonites anterior margins 1–4 frontally directed, rounded. Pereonite 2 with a robust spine tipped with a small setule laterally. Pereonites 2 and 3 of equal width, widest; pereonite 2 width 3.5 length; pereonite 3 width 5.3 length. Pereonite 4 longest, width 2.6 length. Pereonites 5–7 of similar width; pereonites 6 and 7 medially fused, with rounded lateral margins; pereonite 6 with strongly convex anterior margin. Pleotelson length 0.23 body length, nearly as long as wide; width 0.8 pereonite 2 width, with two pairs of well-developed posterolateral spines; proximal pair inserting 0.6 from anterior margin, distal pair inserting 0.9 from anterior margin; posterior margin strongly convex; anterior margin slightly concave. 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 approximately 0.7 pleotelson length (ventrally measured).

Cephalothorax ( Figs 2 A, 3A). Length 0.8 width. Anterior and posterior margin slightly rounded; lateral margins straight. Antennae inserting frontolaterally in a deep fold.

Antennula ( Fig. 3 C). Length 0.12 body length; with 5 articles. First article circular and broadest; with 1 simple seta distolaterally; second article length 1.75 article 1 length, width 0.3 length; with 2 broom setae distally (one broken off). Article 3 and 4 equal in length, length 0.3 article 2 length; article 4 with 2 simple setae. Article 5 length 4 article 4 length, length 8 width; with 1 long aesthetasc and 1 simple seta terminally.

Antenna ( Fig. 3 F). Length one-third body length; with 6 podomere and 11 flagellar articles. Podomere articles 1–4 short; article 2 with 2 simple setae distally; article 3 with 1 robust spine tipped with a small setule and 1 simple seta distally. Article 5 longest, length 1.4 articles 1–4 length, length approximately 5.1 width; with 4 simple setae laterally, with 1 broom seta and 2 simple setae distally. Article 6 length 0.8 article 5 length, length approximately 4.0 width; with 3 short simple setae laterally, with 1 broom seta and 1 simple seta distally. Flagellar article 1 longest, about 0.6 podomere article 6 length, length approximately 3.0 width; with 2 simple setae laterally. Flagellar articles 2–10 of similar length, width decreasing distally; each article with 1–2 short simple setae distally. Article 11 somewhat shorter; with 6 long slender setae terminally.

Maxilliped ( Fig. 3 B). Left and right maxilliped connected by 2 coupling hooks. Epipodite smooth, triangular, slender, length 3.1 width, reaching upper third of palpal article 2. Palpal article 1 short, width 2.7 length; with 1 simple seta distally. Article 2 and 3 of equal length, about twice article 1 length. Article 2 width 1.3 length; with 3 simple setae laterally, with 5 simple setae distally. Article 3 almost as long as wide, distal margin saw-toothed; with 6 robust sensillae. Article 4 as long as article 1, length 2.5 width, with a distal projection reaching to mid of article 5; with 2 long, slender setae distally. Article 5 length 0.6 article 1 length, twice as long as wide; with 2 slender setae of varying size terminally. Endite distal margin with some robust, dentate setae and several fine setae laterally. Protopod coxa quadrangular; length 2.5 width.

Pereopod I ( Fig. 3 D) more robust than pereopod 2. Basis not drawn. Ischium length 2.2 width. Merus length about half ischium length, as long as wide; with 2 long robust setae distodorsally, with 2 simple setae of varying size ventrally. Carpus length 1.9 merus length, length 2.5 width; ventral margin with numerous small setae, membranously embedded, and 3 robust unequally bifid setae in between, with 1 long simple seta distoventrally. Propodus length 0.9 carpus length, 2.9 width; with 2 slender simple setae distodorsally, with numerous small setae, membranously embedded, and 3 robust unequally bifid setae in between ventrally. Dactylus length 0.3 propodus length, length twice width; with 3 slender setae medially. Dorsal claw about as long as dactylus; with 2 long, slender setae between dorsal and ventral claw.

Pereopod II ( Fig. 3 E). Basis length 3.8 width; with 2 simple setae dorsally, with 2 simple setae ventrally and 1 long simple seta distally. Ischium about half basis length, length 2.4 width; with 1 simple seta ventrally. Merus length 0.6 ischium length, length 1.4 width; with 2 simple setae distodorsally, with 3 more slender setae ventrally. Carpus length twice merus length, length 3.5 width; with 2 slender simple setae dorsally, with 6 stout unequally bifid setae ventrally. Propodus about as long as carpus, length 6 width; with 2 simple setae dorsally, with numerous small setae, membranously embedded, and with 4 stout unequally bifid setae ventrally. Dactylus length one-third propodus length, length 2.6 width; with 3 simple setae medially. Dorsal claw length 0.6 dactylus length; with 1 slender seta (broken off) between dorsal and ventral claw.

Operculum (female pleopod 2; Fig. 2 B, D). Length 1.1 width. Lateral and posterior margin rounded; with numerous (> 40) simple setae.

Uropods ( Fig. 2 B, C). Biramous. Protopod trapezoid, length 1.2 width; with 3 simple setae distally. Exopodite about as long as protopod, length 2.8 width; with 1 simple seta terminally. Endopodite length 1.3 exopodite length; with 4 simple setae laterally, with 3 broom setae and 1 long, slender simple seta terminally.

Description paratype male.

Remarks. Details of the habitus, antenna, antennula , maxilliped, pereopods I–II and uropods are only described when different to female.

Habitus ( Figs 4 A, D, 5A) similar to holotype female. Body length 4.1 pereonite 2 width. Pereonites 1–4 of similar width; pereonite 4 anterior margin slightly concave. Pleotelson length 0.25 body length. Pleopod 1 length 0.6 pleotelson length (ventrally measured).

Cephalothorax ( Figs 4 A, 5A). Similar to holotype female.

Antennula ( Fig. 4 B). Length 0.16 body length. Article 1 with 1 broom seta distally; article 2 with 3 broom setae and 1 simple seta distally; article 3 with 1 simple seta; article 4 with 1 broom seta distally; article 5 with 1 long aesthetasc and 2 simple setae terminally.

Antenna ( Fig. 4 C). Length 0.4 body length; with 6 podomere and 8 flagellar articles. Articles 5–7 stouter than in female. Podomere articles 1–4 short; article 2 with 2 simple setae distally; article 3 with 1 robust spine tipped with a small setule and 2 simple setae distally. Article 5 length about 3 width; with 3 simple setae and 1 broom seta laterally, with 3 simple setae distally. Article 6 length about as long as article 5 length, length 2.7 width; with 2 simple setae laterally, with 2 broom setae and 4 small simple setae distally. Unidentified ecto-parasites attached to article 6 dorsal cuticle. Flagellar article 1 longest, length 0.8 podomere article 6 length, length 3.1 width; with 2 simple setae laterally and 3 simple setae distally. Flagellar articles 2–7 of similar length, width decreasing distally; each article with 1–4 simple setae distally. Article 8 somewhat shorter; with 4 long, slender setae terminally.

Mandibles ( Fig.5 B–C). Left and right mandibular palps well developed, consisting of 3 articles and almost reaching incisor. Right mandible palpal article 1 length 0.8 article 2 length. Article 2 with 2 simple setae laterally. Terminal article length about half article 2 length, tapering distally; with a fringe of small setules ventrally and 3 robust setae terminally. Left mandible palpus similar to right mandible; article 2 with fringe of fine setules and 2 simple setae distally. Right mandible incisor process with 7 teeth, left mandible incisor with 7 teeth and a subdistal tooth proximally. Left mandible lacinia mobilis broken off. Right mandible spine row with 10 robust spines and several slender spines in between; dentation decreasing, seta size increasing proximally. Left mandible spine row with 10 robust spines and several slender spines in between, dentation decreasing, seta size increasing proximally. Molar of right and left mandible triangular; right mandible molar with 8, left mandible molar with 7 long, serrate spines distally.

Maxillula ( Fig. 5 E). Left and right maxillula inner endites lost during dissection. Outer endite length 4 width; with 11 strong spine-like setae distally, with few simple setae laterally.

Maxilla ( Fig. 5 F). Inner endite longest and broadest; outer margin with several slender setae, with numerous short, simple setae medially, with 5 somewhat more robust setae distally. Medial and outer endite each with 3 robust, long setae. Outer endite with several slender setae laterally.

Maxilliped ( Fig. 5 D). Similar to female maxilliped. One coupling hook broken off, Palpal article 2 with 2 simple setae laterally. Article 3 with 5 robust sensillae distally. Article 5 with 3 long, slender setae distally.

Pereopod I ( Fig. 6 A). Similar to pereopod II. Basis length 2.9 width; with 1 slender simple seta dorsally, with 2 simple setae ventrally and 1 long slender seta distoventrally. Ischium 0.6 basis length; with 1 simple seta dorsally. Carpus with 4 robust unequally bifid setae ventrally. Propodus with 1 slender seta dorsally and 2 slender simple setae distodorsally, with 2 robust unequally bifid setae ventrally and 2 slender setae of varying size distoventrally.

Pereopod II ( Fig. 6 B). Basis with 1 simple seta dorsally, with 3 simple setae ventrally and 1 long simple seta distally. Ischium with 1 simple seta dorsally, with 2 simple setae ventrally. Carpus 2 slender simple setae and 1 broom seta dorsally, with 5 stout unequally bifid setae ventrally. Propodus length 0.7 carpus length, length 6.5 width; with 2 simple setae and 1 broom seta dorsally, with 3 stout unequally bifid setae ventrally. Dactylus with 2 slender setae between dorsal and ventral claw.

Pereopod III ( Fig. 6 C). Basis length 4 width; with 1 simple seta dorsally, with 3 simple setae ventrally and 1 long simple seta distally. Ischium length 0.6 basis length, length 2.6 width; with 2 simple setae dorsally, with 2 simple setae ventrally. Merus length 0.6 ischium length, length 1.7 width; with 1 simple seta distodorsally, with 2 simple setae ventrally. Carpus length 2.5 merus length, length 5.2 width; with 2 slender simple setae dorsally, with 5 stout unequally bifid setae ventrally. Propodus length 0.8 carpus length, length 5.0 width, with 2 simple setae and 1 long broom seta dorsally, with numerous small setae, membranously embedded, 3 stout unequally bifid setae and 1 simple seta ventrally. Dactylus length one-third of propodus length, length 3.6 width; with 3 simple setae medially. Dorsal claw length 0.8 dactylus length; with 2 slender setae between dorsal and ventral claw

Pereopod V ( Fig.7 A). Pereopods V and VII much longer and more slender than pereopods I – III. Basis length 4 width; with 1 simple seta and 1 long broom seta dorsally, with 4 simple setae ventrally. Ischium length 0.7 basis length, length 3 width; with 1 simple seta dorsally, 3 simple setae medially and with 2 simple setae dorsally. Merus length 0.5 ischium length, length twice width; with 2 long robust setae distodorsally, with 1 simple seta ventrally. Carpus length 2.8 merus length, length 7.2 width; with row of 5 long, slender natatory setae dorsally, with 3 simple setae ventrally, increasing in length distally. Propodus about as long as carpus, length 6.4 width; with row of 9 long, slender natatory setae dorsally, with 2 somewhat shorter simple setae distally, with 1 long, slender seta ventrally.

Dactylus length 0.25 propodus length, length 3.0 width; with 3 simple setae medially. Dorsal claw length 0.7 dactylus length; with 2 slender setae between dorsal and ventral claw

Pereopod VII ( Fig.7 B). Basis length 4.0 width; with 1 simple seta dorsally, with 2 simple setae ventrally. Ischium about half basis length, length 2.8 width; with 1 simple seta ventrally. Merus length 0.6 ischium length, length 2.1 width, with 2 simple setae distodorsally, with 2 setae of varying size distoventrally. Carpus length twice merus length, length 4.7 width; with 2 simple setae of varying size distodorsally, with 1 long, slender simple seta distoventrally. Propodus about as long as carpus, length 6.0 width, with 1 long, slender simple seta and 1 broom seta distodorsally, with 1 short simple seta ventrally and 1 stout unequally bifid and 1 simple seta distoventrally. Dactylus length one-third propodus length, length 3.5 width; with 3 simple setae medially. Dorsal claw length 0.7 dactylus length; with 2 slender setae between dorsal and ventral claw.

Pleopod 1 ( Fig. 7 C). Length 1.7 proximal width. Distal projection width 0.8 proximal width; lateral margins concave. Lateral lobes rounded; with 1 long simple seta. Distal margins almost straight, with 6 simple setae each.

Pleopod 2 ( Fig. 7 D). Sympod length 2.4 width, outer margin rounded; with 6 slender simple setae laterally increasing in size towards distal end; inner margin slightly concave. Endopod inserting 0.5 from distal tip of sympod; stylet length 0.7 sympod length, slightly curved, distal end almost reaching tip of sympod. Exopod short and rounded, with few tiny setule laterally.

Pleopod 3 ( Fig. 7 E). Protopodite length 1.5 width, length about half endopodite length. Exopodite about half endopodite length, length 1.3 width, tapering in width distally; with numerous short simple setae laterally and 1 long, robust seta distally. Endopodite length 1.4 width; with 3 long plumose setae distally (1 broken off).

Pleopod 4 ( Fig. 7 F). Protopodite rectangular, length 0.5 width, about 0.4 endopodite length. Exopodite slender, about as long as endopodite, length 6.5 width; with several thin setules laterally (one-sided) and 1 long robust plumose seta distally. Endopodite ovoid-shaped, about twice as long as wide.

Pleopod 5 ( Fig. 7 G) small oval lobe, without setation, about as long as pleopod 4. Length 2.4 proximal width; width tapering towards distal end.

Uropods (drawn in situ; Fig. 7 H). Protopod trapezoid with 1 simple seta distally. Exopodite with 3 simple setae (1 broken off) terminally. Endopodite with 2 simple setae laterally, with 3 broom setae (1 broken off) and 1 long, slender simple seta terminally.

Remarks. Species in the genus Hebefustis have been previously assigned to two distinct clusters based on the shape of the lateral margins of pereonites 6 and 7 (acute vs. rounded; Siebenaller & Hessler 1977; Kaiser 2008). Aside from the new species rounded margins are also present in H. alleni , H. mollicellus , H. par , H. primitivus , H. robustus and H. vafer . Hebefustis juansenii sp. n. can be identified by possessing a robust spine on pereonite 2 antero-lateral margin in both male and female. The following species also bear a spine on pereonite 2: H. clareolithis , H. cornutus , H. robustus , H. vafer , H. mollicellus , H. dispar and H. primitivus . However, in all these species this feature seems to be sexually dimorphic, as it is only present in males ( Siebenaller & Hessler 1977; Kaiser 2008). In H. primitivus only the male is illustrated, though. So, for this for this species it is not known whether the occurrence of a spine on pereonite 2 is gender related.

Furthermore, H. juansenii can be distinguished from all species in the genus by the presence of two pairs of posterolateral spine on the pleotelson, with the proximal pair inserting in an acute angle (≤45°) 0.6 from the pleotelson anterior margin. Two pairs of posterolateral spines can also be found in H. primitivus , but differs in the angle (90°) and distance (0.3) from the anterior margin. The new species can be further delimited from H. primitivus by the following characters: pereonites 1–4 lateral margins acute (vs. rounded); pleotelson lateral margins straight (vs. rounded); uropods clearly extending beyond posterior margin (vs. not visible in dorsal view); male pleopod 1 distal projection forming 90° angle (vs. straight), lateral lobes with 3 simple setae (vs. 1).

Hebefustis juansenii sp. n. shares some similarities with H. mollicellus . The latter differs from the new species as follows: male pleopod 1; operculum lateral and distal margin with <20 simple setae (vs.> 40). The new species can be distinguished from H. robustus based on the following characters: operculum posterior margin straight (vs. rounded); maxilliped epipodite reaching mid of palpal article 3 (vs. upper-third of palpal article 2); pleopod 2 stylet long, clearly extending beyond tip of sympod (vs. almost reaching the tip); sympod outer margin with 9 simple setae (vs. 6). Hebefustis juansenii sp. n. differs from H. vafer as follows: posterolateral projection in female only slightly pronounced (vs. strongly pronounced).

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 3. Hebefustis juansenii sp. n.; A – F, holotype female (ZMH – K – 43951); A, habitus, dorsal view. B, maxilliped. C, antennula. D – E, pereopods I – II, detail: dorsal and ventral claw. F, antenna. Scale bar: A = 500 µm, B – F = 250 Μm.

FIGURE 4. Hebefustis juansenii sp. n.; A – D paratype male (ZMH – K – 43952); A, habitus, dorsal view. B, antenna. C, antennula. D, pleotelson, ventral view. Scale bar: A = 500 Μm, B – C = 100 Μm; D = 250 Μm.

FIGURE 5. Hebefustis juansenii sp. n.; A – E paratype male (ZMH – K – 43952); A, habitus, dorsal view. B, left mandible. C, right mandible. D, maxilliped. E, maxillula. F, maxilla, detail: inner endite. Scale bar: A = 500 Μm, B – F = 100 Μm.

FIGURE 6. Hebefustis juansenii sp. n.; A – C paratype male (ZMH – K – 43952); A, pereopod I, detail: dorsal and ventral claw. B, pereopod II. C, pereopod III. Scale bar: A – C = 100 Μm.

FIGURE 7. Hebefustis juansenii sp. n.; A – H paratype male (ZMH – K – 43952); A, pereopod V. B, pereopod VII. C – G, pleopods 1 – 5. H, uropod. Scale bar: A – H = 100 Μm.