Coxophoxus alonso, Senna, 2010

Senna, André R., 2010, A new genus and five new species of Phoxocephalidae (Crustacea: Amphipoda) from the south-east Brazilian deep sea, Journal of Natural History 44 (33 - 34), pp. 2075-2118 : 2086-2092

Coxophoxus alonso sp. nov.

( Figures 5–8 )

Material examined

Holotype: one male, 2.9 mm, Petrobras , Campos Basin, N / Rb Astro Garoupa, boxcorer, #50A, 22°02′31″S, 39°52′13″ W, 1050 m depth, 29 June 2003, MNRJ 21032 . Paratypes: one female, 2.8 mm, Petrobras , Campos Basin, N / Rb Astro Garoupa, boxcorer, #50A, 22°02′30″ S, 39°52′14″ W, 1050 m depth, 14 December 2002, MNRJ 21033 ; one female, 2.8 mm, Petrobras , Campos Basin, N / Rb Astro Garoupa, boxcorer, #56, 21°57′09″ S, 39°47′26″ W, 1350 m depth, 14 December 2002, MNRJ 21034 ; one female, 3.0 mm, Petrobras , Campos Basin, N / Rb Astro Garoupa, boxcorer, #45, 22°11′49″ S, 39°52′19″ W, 1050 m depth, 10 December 2002, MNRJ 21035 .

Etymology

The species name is a noun in apposition, and it is in honour of Dr Gloria Maria Alonso de Pina, of the Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, for her vast contribution to phoxocephalid taxonomy.

Diagnosis

Head, rostrum with lateral notches. Mandible, incisor with three blunt spines, lacinia mobilis as a small blunt peg. Maxilliped, outer plate subtriangular, slightly longer than inner plate, with one apical curved stout seta. Gnathopod 1, coxa weakly expanded anteroventrally. Gnathopods 1 and 2 palm obtuse, slightly convex, palmar corner defined by an acute spine with a lateral stout seta; dactyl reaching the palmar corner. Pereopod 4, coxa slightly expanded, with posterodorsal excavation. Pereopod 6, basis posteriorly expanded with posteroventral lobe present. Pereopod 7, basis with posterior margin serrate, posteroventral lobe strongly produced. Uropod 1, peduncle with small ventroapical point. Uropods 1 and 2, rami naked, subequal in length. Uropod 3, outer ramus carrying long plumose setae in male, inner ramus subequal in length to the outer ramus article 1 in female, and half length of the outer ramus article 1 in male.

Description

Head, rostrum with lateral notches. Eyes present, larger and ovate in male, rounded in female. Antenna 1, peduncle article 1 about 1.5 times as long as wide, 1.5 times as wide as article 2, ventrodistal corner with about three slender setae; flagellum with five articulations in male, bi-articulate in female. Antenna 2, article 4 dorsally setose, with a weak row of facial stout setae, article 5 slightly elongated, dorsodistally setose, flagellum elongated, about 80% the body length in male, and about 40% the body length in female. Mandible, molar conical, triturative; incisor with three blunt spines; accessory setal row weak, with two slender setae; lacinia mobilis as a small blunt peg; hump of palp small; palp article 1 short, about 1.2 times as long as wide, article 2 about four times as long as wide, 1.25 times longer than article 3, ventral margin with one proximal small slender seta, and two distomedial long slender setae, article 3 apically setose. Maxilla 1, inner plate naked; outer plate with six apical multicuspidate stout setae; palp uni-articulate, with three apical simple setae. Maxilla 2, inner plate slightly broader than outer plate, both plates weakly setose. Maxilliped, both inner and outer plates small, outer plate subtriangular, slightly longer than inner plate, with two setae on the inner margin and one apical curved stout seta; palp with four articulations, article 2 stout, 1.7 times longer than article 3, inner margin slightly setose, article 3 with facial setae, twice as long as broad, article 4 slender, with one subapical seta, apical nail present, 0.5 times as long as article 4.

Gnathopod 1, coxa weakly expanded anteriorly, anterior margin almost straight, ventral margin with four setae and one setule, basis elongated, 3.5 times longer than broad, anterior margin without setae, posterior margin with one small slender seta on posteroventral corner, merus subtriangular, carpus slender, suboval, about 0.7 times as long as propodus, posterior margin with one slender seta, propodus subrectangular, anterior and posterior margins subparallel, without setae, palm obtuse, slightly convex, setose, with a medial excavation, palmar corner defined by an acute spine with a lateral stout seta; dactyl slender, curved, reaching the palmar corner, without apical nail. Gnathopod 2 subequal to gnathopod 1, slightly larger, coxa weakly expanded anteriorly, anterior margin almost straight, ventral margin with four setae and one setule, basis elongated, 4.2 times longer than broad, anterior margin with one small slender seta, posterior margin with two small slender setae on posteroventral corner, merus subtriangular, carpus slender, suboval, about 0.7 times as long as propodus, posterior margin with two slender setae, propodus subrectangular, anterior and posterior margins subparallel, weakly setose, palm obtuse, slightly convex, setose, with a medial excavation, palmar corner defined by an acute spine with a lateral stout seta; dactyl slender, curved, reaching the palmar corner. Pereopod 3, coxa rectangular, 2.1 times longer than broad, without setae, anterior and posterior margins straight; subparallel, merus, carpus and propodus, length ratio 9: 5: 6; carpus, posteroventral margin setose; dactyl elongated, thin, as long as propodus. Pereopod 4, coxa posteriorly expanded, anterior margin almost straight, posterior margin slightly oblique, ventral margin without setae, posteroventral margin rounded to subquadrate, posterodorsal excavation present; merus, carpus and propodus, length ratio 25: 8: 11; carpus, posteroventral margin setose; dactyl elongated, thin, 1.4 times longer than propodus. Pereopod 5, basis slender, about six times longer than broad; merus, carpus and propodus, posteroventral margin setose, length ratio 8: 4: 5; dactyl elongated, thin, as long as propodus. Pereopod 6, basis expanded posteriorly, about 1.4 times longer than broad, anterior margin with five rows of setae (2-3-3-4-2), posterior margin smooth, posteroventral lobe rounded and smooth, merus, carpus and propodus, scarcely setose, length ratio 35: 37: 29, dactyl thin, 0.7 times as long as propodus. Pereopod 7, basis strongly expanded posteriorly, ovate, about 1.2 times longer than broad, anterior margin weakly setose, posterior margin rounded and serrate, posteroventral lobe rounded and smooth; merus, carpus and propodus, length ratio 9: 13: 10; merus, anterior margin with two rows of setae (1-3); carpus, anterior margin with two rows of setae (2-3), posteroventral corner with two setae; dactyl thin, 0.9 times as long as propodus.

Epimeral plate 3 without setae, posteroventral corner rounded, slightly produced posteriorly. Urosomite 1, dorsal carina present. Urosomite 3, weak dorsal carina present. Uropod 1, peduncle elongated, not combed, about three times longer than broad, dorsolateral margin with two small slender setae, dorsoapical corner with one stout seta, ventroapical corner with one small point; rami naked, subequal in length, slightly shorter than peduncle. Uropod 2, peduncle elongated, not combed, about 3.7 times longer than broad, with two dorsoapical stout seta; rami naked, subequal in length, about as long as peduncle. Uropod 3, peduncle not combed in both sexes; female uropod 3 peduncle about 2.5 times longer than broad, ventroapical corner with two stout setae and two small slender setae, dorsolateral corner with one small slender seta, dorsomedial corner with two slender setae; inner ramus, about five times longer than broad, without setae; outer ramus, article 1 subequal in length to the inner ramus, with two apical stout setae; article 2 slender, about 0.6 times as long as article 1, with two apical long slender setae; male uropod 3, peduncle 1.8 times longer than broad, dorsolateral corner with one stout seta; inner ramus subtriangular, small, half length of the outer ramus article 1, bearing two apical slender setae; outer ramus article 1 elongated, about five times longer than broad, bearing a few long plumose setae on the inner margin; article 2 slender, smooth, about 0.4 times as long as article 1. Telson deeply cleft, about 80% of its length, elongated, about 1.7 times longer than broad, with one apical stout seta and one small slender seta on each lobe, without dorsal and lateral setae.

Remarks

Coxophoxus alonso sp. nov. resembles C. hidalgo in many aspects, such as: antenna 2 lacking basal ensiform process; eyes present in both sexes, greater and ovate in males, rounded in females; molar triturative; maxilla 1 with inner plate naked and palp uni-articulated; gnathopods 1 and 2 carpus with eusirid attachment; basis of pereopod 5 thin; and telson elongated and deeply cleft. However, C. alonso sp. nov. differs from the latter species by: rostrum with lateral notches; antenna 2 flagellum very elongated in male and relatively reduced in female; coxa 1 weakly expanded anteroventrally; gnathopods 1 and 2 palms obtuse; coxa 4 with posterodorsal excavation; basis of pereopod 6 posteriorly expanded with posteroventral lobe present; basis of pereopod 7 with posteroventral lobe strongly produced, reaching the proximal part of the propodus; and male uropod 3 outer ramus bearing long plumose setae. The latter character represents an unusual pattern of sexual dimorphism in Phoxocephalidae because commonly the male uropod 3 inner ramus is elongated, contrary to that observed in the new species, in which the female uropod 3 inner ramus is elongated.

Coxophoxus alonso sp. nov. shares with C. coxalis ( Barnard KH, 1932) the elongated, spiniform dactylus of pereopod 6, and the broadly rounded posteroventral corner of epimeral plate 3. The new Brazilian species is similar to C. hidalgo Barnard JL, 1966 in that gnathopod 2 is slightly stronger than gnathopod 1, and in the presence of five rows of long setae on the anterior margin of the basis of pereopod 6. However, the new species is different from both in the main character which, according to Barnard JL (1966), differentiates C. hidalgo from the species described by Barnard KH (1932), that is to say, the length and width ratio of basis of pereopod 7. In C. alonso sp. nov. this ratio is greater than in both the previous mentioned species.

Geographic distribution

Known only from the type locality, Campos Basin , off Rio de Janeiro State coast .

Bathymetric range

Collected from 1050–1350 m depth.

Figures

Figure 5. Coxophoxus alonso sp. nov.: male, 2.9 mm, holotype, Campos Basin, 22°02′31″ S, 39°52′13″ W, 1050 m depth, 29 June 2003, MNRJ 21032. Scale bars: 1.0 mm for Hb; 0.1 mm for the remainder.

Figure 6. Coxophoxus alonso sp. nov.: male, 2.9 mm, holotype, Campos Basin, 22°02′31″ S, 39°52′13″ W, 1050 m depth, 29 June 2003, MNRJ 21032; female, 2.8 mm, paratype, Campos Basin, 22°02′31″ S, 39°52′14″ W, 1050 m depth, 14 December 2002, MNRJ 21033. Scale bars: 0.1 mm.

Figure 7. Coxophoxus alonso sp. nov.: female, 2.8 mm, paratype, Campos Basin, 22°02′31″ S, 39°52′14″ W, 1050 m depth, 14 December 2002, MNRJ 21033. Scale bars: 0.1 mm.

Figure 8. Coxophoxus alonso sp. nov.: male, 2.9 mm, holotype, Campos Basin, 22°02′31″ S, 39°52′13″ W, 1050 m depth, 29 June 2003, MNRJ 21032; female, 2.8 mm, paratype, Campos Basin, 22°02′31″ S, 39°52′14″ W, 1050 m depth, 14 December 2002, MNRJ 21033. Scale bars: 0.1 mm.