Stebbingiella globulosa, Marques-Junior, Paulo R. & Senna, André R., 2013

Marques-Junior, Paulo R. & Senna, André R., 2013, Description of a new genus and species of the family Melphidippidae Stebbing, 1899 (Crustacea: Amphipoda) from the deep waters of Brazil, Zootaxa 3641 (4), pp. 463-475 : 465-474

Stebbingiella globulosa sp. nov.

( Figs 1–6 )

Etymology. The specific epithet relates to the shape of the eyes, highly projected and globular.

Material examined. Holotype: Male, 16.0 mm, dissected and drawn, mounted on slides with glycerol gelatin, #MBT 180, 25°55'S – 45°46'W, off São Paulo state coast, Brazil, 224 m, 29/V/1971, rectangular dredges, R/V Prof. W. Besnard leg., DZUFRJ 4944.

Paratypes: one female, 23.8 mm, dissected and drawn, mounted on slides with glycerol gelatin, #MBT 180, 25°55'S – 45°46'W, off São Paulo state coast, Brazil, 224 m, 29/V/1971, rectangular dredges, R/V Prof. W. Besnard leg., DZUFRJ 4945, 4 females, in 70% ethanol, #RPC 1282, 25°58'S – 46°07'W, off São Paulo state coast, Brazil, 260-268 m, 07/XII/1970, rectangular dredges, R/V Prof. W. Besnard leg., DZUFRJ 4946.

Diagnosis. Rostrum absent. Lateral cephalic lobe subacute, with globular eyes extremely produced, reaching beyond the second article of antenna 2 peduncle. Antennae elongate. Antenna 1 longer than antenna 2. Primary flagellum much longer than the peduncle. Accessory flagellum 7-articulate. Maxilla 1, outer plate with 6 apical stout setae. Coxae short, slightly setose, not contiguous, coxae 3–4 with strong acute to subacute anterior projection, coxae 5–7 with strong acute to subacute posterior projection, coxa 6 without projections. Gnathopods robust, strongly subchelate, sexually dimorphic. Pereopods 3–4, carpus with posterior margin setose, dactyli elongate. Pereopods 5–7, anterior margin with slender and stout setae continuously. Pleonites dorsally smooth. Urosomites 1–2 dorsally bicarinate. Uropods 1–2 marginally spinose, with rami subequal in length. Uropod 3 highly extended, peduncle slightly elongate, rami elongate subequal in length, apically truncate, outer ramus 2- articulate. Telson cleft, not fully movable with two globular lobes, about 2X wider than long.

Description. Head wider than deep. Rostrum absent. Cephalic lateral lobe subacute, with globular eyes extremely produced, reaching beyond the second article of antenna 2 peduncle, antero-ventral margin of the head sinuous, without fissure. Compound eyes extremely produced and globular, ocelli densely distributed on dorsal and distal parts.

Antenna 1 elongate, marginally setose, peduncle, articles elongate, first article about 3.3X longer than wide, and slightly shorter than the second article, second article about 9X longer than wide, third article 11X longer than wide, remaining articles subequally sized; primary flagellum 26-articulate, accessory flagellum 7-articulate. Antenna 2 shorter than antenna 1 and marginally setose, flagellum 17-articulate. Right mandible, incisor multicuspidate, lacinia mobilis bifid well-developed, molar well-developed sub-triturative; palp 3-articulate, first article subquadrate, second article slender, bristle 6.3X longer than wide, ventral margin setose, third article 6.7X longer than wide, densely setose in the distal region, about 0.7X the length of the second article. Left mandible subequal to right mandible, with 4 setae in the apical region of the molar. Labrum rounded, with two elements, the first larger, distal margin with minute setae, with a medial concavity and a sharp projection at one end of the concavity. Labium, inner plate rounded with small setae at the apex, outer plate with 3–4 thick setae on inner margin. Maxilla 1, inner plate suboval elongate, marginal row of setae present, with 2 plumose setae on apical margin; outer plate subrectangular, apical margin with 6 strong setae, palp 2-articulate, first article subquadrate, second article broad, 4.6X longer the first article and about 3.8X longer than wide, with four strong setae on the apical border. Maxilla 2, inner plate densely setose on apical margin, inner margin with row of marginal setae; outer plate subrectangular, 1.3X longer than the inner plate, 2X longer than wide, densely setose on apical margin, with internal setae simple and external setae pappous. Maxilliped, inner plate subrectangular, 3X longer than wide, inner margin with apical setulae, outer plate suboval, well-developed, 2.6X longer than wide, inner margin with thick setae; palp 4- articulate, first article subquadrate, second article well-developed, 3.3X longer than wide, inner margin with simple setae, outer margin with a long seta at the distal region, third article suboval marginally setose, fourth article weakly developed, 0.2X the length of the third article with a thin and elongate claw, 2.5X the length of the fourth article. Gnathopod 1 subchelate, coxa wider than long, glabrous, projected posteriorly; basis subrectangular, posterior distal margin with 4 setae, 3X longer than wide, anterior margin has a notch in the distal portion, with setae on its margin after this notch; merus longer than wide, postero-distally produced and subacute with posterior margin setose; carpus subtriangular, slightly elongate, posterior margin setose, with two robust setae at the apex of its posterior projection, densely setose on the antero-distal and postero-distal angles; propodus elongate, about 2X longer than wide, oval, palm defined by a long thick seta, palm and posterior margin carrying small robust setae, anterior margin with setae on the distal region; dactylus robust, curved and elongate, approximately twice the length of the palm. Gnathopod 2 of female subchelate, coxa wider than long, glabrous, posteriorly projected, and acute wedge-shaped; basis subrectangular, 4.6X longer than wide, with seta only distally; merus as long as wide, distal margin produced and subacute, without setae on its margin, carpus subtriangular, slightly elongate, with a strong postero-distal projection; propodus elongate, about 1.8X longer than wide, oval, palm with robust setae, anterior margin densely setose; dactylus elongate, as long as palm, strongly subchelate, without marginal bristles. Pereopod 3, coxa slightly longer than broad, produced anteriorly, anteroventral angle blunt and apically rounded, with 3 setae in the produced region; basis subrectangular, 5X longer than wide, anterior margin with 1 seta, and posterior margin with 5 setae; merus with subparallel anterior and posterior margins 3X longer than wide, anterior margin with 1 seta in the apical region, posterior margin with 2 setae in the apical region; carpus 2X longer than wide with a robust seta anteriorly in the apical region, posterior margin setose; propodus thin, about 5.2X longer than wide; dactylus long and acute. Pereopod 4 slightly larger than pereopod 3, coxa produced anteriorly, anteroventral angle acute; basis subrectangular, 6X longer than wide, anterior margin with 1 seta, and posterior margin with 5 setae; merus with subparallel anterior and posterior margins, 3X longer than wide, anterior margin with 1 seta on apical region, posterior margin with 2 setae in the apical region and 1 seta in the proximal; carpus 2X longer than wide, slightly concave on anterior margin; propodus thin, about 4.8X longer than wide; dactylus long and acute. Pereopod 5 elongate; coxa produced posteriorly, posteroventral angle acute; basis subrectangular 3.3X longer than wide; merus with subparallel anterior and posterior margins, 8X longer than wide, posterior margin with 4 moderately robust setae two of which located on the distal region, anterior margin setose; carpus thin, marginally setose, 14.8X longer than wide; propodus thin and elongate, slightly setose in the anterior and posterior margins; dactylus short, distally acute. Pereopod 6, coxa subquadrate; basis 2.3 times longer than wide, with a small seta on distal regions of the anterior and posterior margins; merus with subparallel anterior and posterior margins, anteriorly setose, with two moderately robust setae in the posterodistal region. Pereopod 7, coxa subquadrate, produced posteriorly, anteroventral angle acute, with two rounded lobes at the distal region; basis strong, 3.5X longer than wide; merus as long as basis, about 7.8X longer than wide, with moderately robust setae marginally. Pleopods 1–3 biramous; rami subequal in length, multi-articulate, marginally setose. Pleopod 1, peduncle 7.4X longer than it is wide, with a simple seta on anterior margin, which has 0.7X the length of the ramus.

Pleopod 2 peduncle 4.8X longer than wide. Pleopod peduncle 3 about 2.4X longer than wide and approximately 0.1X the length of the ramus. Urosomite 1, dorsal margin setose, posterior-dorsal angle bicarinate. Urosomite 2, posterior-dorsal angle bicarinate. Urosomite 3, dorsal margin slightly setose, posterior-dorsal angle simple. Uropod 1, peduncle subrectangular, marginally spiny, about 5.6 times longer than wide; rami subequal in length, marginally spiny. Uropod 2, peduncle subrectangular 3X longer than wide, subequal in length to the rami, branches subequal in length, outer ramus anteriorly spiny, inner ramus with 3 stout setae in the distal region. Uropod 3 very extended, peduncle slightly elongate, 2.3X longer than wide; rami elongate, densely setose marginally, outer ramus 2- articulate, apically truncated, inner ramus apically rounded, slightly shorter then outer ramus. Telson cleft, not fully movable, with two globular lobes, about 2X wider than long, with stout setae on two lobes.

Sexual dimorphic characters. Male specimen is extremely similar to females, bearing sexual dimorphisms only in the following characters: Gnathopod 2 of male strongly subchelate, coxa subquadrate, 1.4 X wider than long, glabrous; basis subrectangular, 4X longer than wide, anterior distal margin with 4 simple setae; merus 1.9X longer than wide, distal margin produced and subacute, without setae on its margin, carpus subtriangular, posterior margin setose; propodus robust, suboval, about 1.6 times longer than wide, with 5 setae on antero-distal margin, palm defined by a strong acute process, slightly longer than the posterior margin, portion next to the joint with dactylus carrying a trapezoid process, followed by two subacute spines, portion close to palmar angle deeply Ushaped concave; dactylus stout, curved, subequal in length to palm, without setae on margin.

Discussion. Stebbingiella gen. nov. resembles other genera of the family in having a slim body, elongate antennae, antenna 1 longer than antenna 2, primary flagellum longer than the peduncle, inner lobes of the labium present, labrum with an apical notch (deep notch in Melphisana ) and uropods marginally spinose.

On the other hand the new genus differs from Melphidippa by the following characters (character states of Melphidippa in parentheses): lateral cephalic lobe subacute (rounded or subquadrate), antenna 1 accessory flagellum 7-articulate (2-articulate and elongate), labrum rounded, distal margin minutely setose, with deep apical notch and a sharp projection at one end of the apical notch (roughly rounded below, but with small apical notch), maxilla 1, outer plate with 6 stout setae (9 stout setae), coxae 3–4 little setose, anteriorly produced, anteroventral angle subacute / acute (highly setose, rarely contiguous, without anterior projections), gnathopods moderately robust, heavily subchelate, genders unequal (weak, little subchelate, genders monomorphic), uropods 1–2, branches subequal in length (outer branch strongly reduced), uropod 3 slightly elongate (highly elongate) rami subequal in length (outer ramus slightly smaller than the inner), apically truncate, outer ramus 2-articulate (1- articulate, lanceolate), metasoma has no teeth (dorsally toothed some teeth arranged transversely), telson cleft, not fully movable, with two globular lobes, about 2X wider than long (normal length, slit halfway, lobes tapered, subapical notch, poorly armed).

Likewise, Stebbingiella gen. nov. differs from Melphidippella by having (character states of Melphidippella in parentheses) lateral cephalic lobe subacute (globular, produced to the middle of the first article of peduncle of antenna 1, carrying a strong acute spine on apical margin), antenna 1 accessory flagellum 7-articulate (1-articulate, vestigial), labrum rounded, distal margin minutely setose, with deep apical notch and a sharp projection at one end of the apical notch (labrum grossly rounded below, but with small apical notch), maxilla 1, outer plate with 6 stout setae (11 stout setae), coxae 3–4 anteriorly produced, anterior ventral angle subacute / acute (rarely contiguous, without anterior projections), gnathopods moderately robust, heavily subchelate, genders unequal (weak, little subchelate, elongate wrists, genders equal), uropods 1–2 rami subequal in length (outer ramus strongly reduced), uropod 3, peduncle a little elongate (strongly elongate), apically truncate, outer ramus 2-articulate (1-articulate, lanceolate), metasome has no teeth (dorsally toothed some teeth arranged transversely), telson cleft, not fully movable with two globular lobes, about 2X wider than long (normal length, cleft up to two-thirds of its length, tapered lobes, apically notched, weakly armed).

Stebbingiella gen. nov. differs from Melphisana by having (characters states of Melphisana in parentheses): lateral cephalic lobe subacute (subglobular), antenna 1 accessory flagellum 7-articulate (1-articulate, vestigial), maxilla 1, outer plate with 6 stout setae (9 stout setae), coxae 3–4 anteriorly produced, anteroventral angle subacute / acute (without anterior projections), gnathopods moderately robust, heavily subchelate, genders unequal (poor, little subchelate, wrists elongate, genders monomorphic), uropods 1–2, rami subequal in length (exterior ramus strongly reduced), uropod 3, peduncle slightly elongate (highly elongate), apically truncate, outer ramus 2- articulate (1-articulate, lanceolate), metasoma without teeth (toothed dorsally, some teeth arranged transversally), telson cleft, not fully movable, with two globular lobes, about 2X wider than long (normal length, uncleft, apically emarginate, poorly armed).

Stebbingiella gen. nov. differs from Melphisubchela by having (character states of Melphisubchela in parentheses): reaching beyond second article of peduncle of antenna 2 (subquadrate), antenna 1, accessory flagellum 7-articulate (4-articulate), maxilla 1, outer plate with 6 stout setae (7 stout setae), maxilliped, fourth article shorter than the claw (fourth article longer than the claw), coxae 3–4 anteriorly produced, antero-ventral angle subacute / acute (no anterior projections), gnathopods slightly robust, strongly subchelate, sex unequal (propodus suboval, strongly subchelate), uropods 1–2, rami subequal in length (outer ramus strongly reduced), telson cleft, not fully movable with two globular lobes, about 2X wider than long (normal length, cleft up to half length, tapered lobes, subapical notch, poorly armed).

Stebbingiella gen. nov. has exclusive features such as the cephalic lateral lobe subacute, globular eyes extremely produced, reaching beyond the second article of peduncle of antenna 2, antenna 1 accessory flagellum 7- articulate, labrum rounded, distal margin minutely setose, with deep apical notch and an acute projection on apical end of the notch, maxilla 1, inner plate suboval elongate, outer plate with 6 stout setae, maxilla 2 without facial row of setae, coxae 3–4 anteriorly produced, antero-ventral angle subacute / acute, coxae 5–7 produced posteriorly, subacute, gnathopods moderately robust, subchelate, sexually dimorphic, uropods 1–2, rami subequal in length, uropod 3, peduncle a little elongate, rami subequal in length, apically truncate, outer ramus 2-articulate, pleonites dorsally smooth, urossomites 1–2 dorsally bicarinate, telson cleft, not fully movable, with two globular lobes, about 2X wider than long.

Geographical distribution. Stebbingiella globulosa sp. nov. is known only from the Brazilian continental slope, off the coast of the state of São Paulo. Type locality: 25°S–46°W, 224 m to 268 m ( Fig 7 ). This is the first record of the family Melphidippidae from Brazilian waters.

Bathymetric range. The specimens were collected at depths between 224 m and 268 m.

Figures

FIGURE 1. Stebbingiella globulosa sp. nov.: female, paratype, 23.8 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4945. Scale bar: 5.0 mm.

FIGURE 2. Stebbingiella globulosa sp. nov.: female, paratype, 23.8 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4945. Scale bar: 0.2 mm.

FIGURE 3. Stebbingiella globulosa sp. nov.: female, paratype, 23.8 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4945; male, holotype, 16.0 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4944. Scale bar: 0.5 mm.

FIGURE 4. Stebbingiella globulosa sp. nov.: female, paratype, 23.8 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4945. Scale bar: 0.5 mm.

FIGURE 5. Stebbingiella globulosa sp. nov.: female, paratype, 23.8 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4945. Scale bar: 0.5 mm.

FIGURE 6. Stebbingiella globulosa sp. nov.: female, paratype, 23.8 mm, São Paulo, Brazil, 25 º 55 ’ S – 45 º 46 ’ W, DZUFRJ 4945. Scale bars: 0.2 mm for T; 0.5 mm for the remains.

FIGURE 7. Distribution of Stebbingiella globulosa sp. nov. SP: São Paulo state; Star: type locality, 25 º 55 ’ S – 45 º 46 ’ W; Circle: ocurrence of paratypes, 25 º 55 ’ S – 45 º 46 ’ W (Distribution map by Danielle P. Cintra).