Lysianopsis concavus Senna, 2007

Senna, André R. & Serejo, Cristiana S., 2008, Amaryllididae and Lysianassidae (Amphipoda: Lysianassoidea) from off the central coast of Brazil (11 ºS – 22 ºS), with descriptions of three new species, Zootaxa 1718, pp. 45-68 : 60-65

Lysianopsis concavus Senna, 2007

( Figures 10–12 )

Lysianopsis concavus Senna, 2007: 182 .

Type material. Holotype: REVIZEE Benthos Program, Central SCORE, N/R Astro Garoupa col.: female, 7.0 mm, 14º48'30"S – 38º55'00"W, 20 m, July 1, 2001, MNRJ 18555.

Paratypes: REVIZEE Benthos Program, Central SCORE, N/R Astro Garoupa col.: 13 specimens, 14º56'49" S – 38º50'56" W, 20 m, July 1, 2001, MNRJ 19497; one specimen, 20º52'01" S – 40º10'01" W, 55 m, July 20, 2001, MNRJ 17758; one specimen, 13º38'46" S – 38º44'31" W, 55 m, July 2, 2001, MNRJ 17770; one specimen, 19º48'29" S – 37º56'20" W, 60 m, July 18, 2001, MNRJ 17778; five specimens, 16º47'10" S – 38º41'10" W, 50 m, June 30, 2001, MNRJ 18535; eight specimens, 15º34'05" S – 38º49'48" W, 20 m, July 1, 2001, MNRJ 18554; four specimens, 20º50'56" S – 40º10'01" W, 75 m, June 28, 2002, MNRJ 19436; eight specimens, 20º50'56" S – 40º10'01" W, 75 m, June 28, 2002, MNRJ 19437; one specimen, 20º29'20" S – 28º51'18" W, 52 m, July 10, 2001, MNRJ 19438; four specimens, 19º16'19" S – 38º01'08" W, 67 m, June 28, 2001, MNRJ 19439; two specimens, 19º31'37" S – 38º46'05" W, 65 m, June 28, 2001, MNRJ 19441; two specimens, 20º51'25" S – 33º38'10" W, 65 m, July 11, 2001, MNRJ 19442; two specimens, 19º31'05" S – 38º45'58" W, 85 m, June 18, 2002, MNRJ 19443; one specimen, 20º40'41" S – 34º35'02" W, 108 m, July 12, 2001, MNRJ 19445; one specimen, 15º34'05" S – 38º49'48" W, 20 m, July 1, 2001, MNRJ 19446; five specimens, 18º03'32" S – 37º18'54" W, 100 m, June 29, 2001, MNRJ 19447; two specimens, 15º49'41" S – 38º36'25" W, 82.9 m, June 21, 2002, MNRJ 19448; two specimens, 18º39'47" S – 37º52'12" W, 65 m, June 29, 2001, MNRJ 19449; two specimens, 13º04'30" S – 38º23'31" W, 91 m, June 23, 2002, MNRJ 19981.

Diagnosis. Epistome concave, upper lip more produced than epistome. Maxilla 1, outer plate, setal-teeth 6-7 with 4-5 cusps. Pereopod 6, basis with posterior margin slightly concave. Uropod 3, outer ramus 2-articulate. Telson with truncate and concave on distal margin, with two small distolateral setae.

Description. Holotype, female, 7.0 mm. Head longer than deep; lateral cephalic lobe rounded; rostrum absent; eye reniform. Antenna 1 small; article 1 of peduncle, 2X longer than broad; accessory flagellum with nine articles; primary flagellum with nine articles. Antenna 2 subequal in length to antenna 1; flagellum with nine articles. Mouthparts forming a subquadrate bundle. Epistome concave, upper lip more produced than epistome, anterodorsal corner presenting a lobe following by a notch, anteroventral corner with a sharp projection, ventral margin covered by small simple setae. Mandible with incisor smooth and with margins slightly convex; setal row with 7-8 setae; molar smooth; mandibular palp, article 1 small, 2X longer than broad, article 2, length 5X the width, ventral margin with two medial setae and two distal setae, article 3 length 4.5X the width, curved, minutely setose, distally truncate, with six long setae on the distal margin. Maxilla 1, outer plate, ST1 1-cuspidate, ST2-4 2-cuspidate, ST5 3-cuspidate, ST6 4-cuspidate, ST7 5-cuspidate, STA-D 2-cuspidate; palp 2-articulate, apical margin serrate, with a small slender seta on the distomedial corner. Lower lip, inner margin covered by small slender setae. Maxilliped, inner plate large, inner margin setose, apical margin with three nodular setae; outer plate small, suboval, with vestigial submarginal setae; palp with four articles, article 2, inner margin with eight setae, distolateral corner with two setae, article 3, inner margin with seven slender setae, distolateral corner with five long slender setae and a small slender seta, dactylus well developed with a subterminal seta, subterminal tooth present.

Gnathopod 1, coxa 1 as long as coxa 2, anterior margin slightly concave, anteroventral margin produced, rounded, submarginal setae present; basis 2.5X longer than broad, anterior margin setose; ischium, posterior margin setose; merus, subtriangular, with a tuft of setae on the posterior margin; carpus subtriangular, with a tuft of setae on the dorsodistal corner and a tuft of setae on the ventrodistal corner; propodus 2.25X longer than carpus, subrectangular, distally narrowed, posterior margin setose, without palm; dactylus simple, without slender or stout setae, nail present. Gnathopod 2, minutely subchelate; coxa 2 large; basis elongate, anterior margin setose; ischium elongate, with a tuft of setae on the posterodistal margin; merus subtriangular; carpus 1.2X larger than merus, minutely setose, anterior margin setose; propodus small, 0.5X carpus length, minutely setose, anterior and posterior margins setose, palm obtuse, posterodistal corner with a small robust setae; dactylus small, not reaching the palmar corner. Oostegite elongate, with nodular processes, without setae. Pereopod 3, coxa large, as long as coxa 2; basis with a tuft of setae on the posterodistal corner; ischium small, posterior margin setose; merus with posterior margin setose. Pereopod 4, coxa large, posteroventral lobe present, anterior margin slightly convex; basis, length 3X the width, with a tuft of setae on posterodistal corner; ischium, posterior margin setose; merus anterodistally projected, with a tuft of setae on the anterodistal corner, posterior margin setose; carpus, 0.5X the merus length, posterior margin setose; propodus slender, posterior margin with five slender setae; dactylus robust, dorsal margin with a proximal seta. Pereopod 5, coxa with slight anteroventral lobe present; basis expanded, anterior margin rounded, posterior margin serrate and rounded, posteroventral lobe present; ischium with a tuft of setae on the anterodistal corner; carpus and propodus, anterior margin with robust bifid setae; dactylus well developed, smooth. Pereopod 6, coxa, not posteriorly lobate, basis posteriorly expanded with posterodistal lobe slightly developed, anterior margin rounded and setose, posterior margin serrate and concave. Pereopod 7, basis expanded, anterior margin slightly rounded, posterior margin serrate and rounded, posterodistal lobe rounded.

Pleonites 1-3 and urosomites 1-3 dorsally smooth. Uropod 1, peduncle elongate, length 6X the width, with four dorsal setae and two distomedial setae; rami subequal in length, elongate, inner ramus with a small lateral seta. Uropod 2, peduncle with a dorsodistal seta and a distolateral seta, length 2X the width; rami subequal in length, inner ramus notched with a long dorsal seta. Uropod 3, peduncle small, 1.75X longer than broad, with dorsolateral flange, two dorsal setae and a dorsodistal seta; inner ramus approximately smaller, 0.9X than outer ramus length, outer ramus 2-articulate, rami without slender or stout setae. Telson entire, slightly longer than broad, without dorsal robust setae, apical margin truncate and concave, with two pairs of thin and small setae.

Remarks. Lysianopsis concavus Senna, 2007 is similar to other species of the genus, such as L. ozona Lowry & Stoddart, 1997 , in presenting a non prehensile gnathopod 1 in both sexes and a concave epistome; L. subantarctica (Schellenberg, 1931) , also presents the epistome with the concave dorsal margin and the upper lip strongly produced dorsally, with a lobe on the anterodorsal corner following by a notch. Lysianopsis subantarctica also is similar to the Brazilian species, for presenting the pereopod 6 with posterior margin of the basis concave, and presenting the gnathopod 1 simple and the outer ramus of uropod 3 2-articulate, as well as L. concavus .

However, L. concavus is the only species of the genus that presents telson with the concave apical margin, from where arose its etymology. Beside that, L. subantarctica presents the outer plate of maxilla 1 with a crown of ten setal-teeth, instead of 11 as in the other species of the genus.

Lowry & Stoddart (1984) describe the epistome of L. subantarctica as strongly produced, but it is clear in their illustration that the upper lip is the produced one, while the epistome is concave.

Distribution. Lysianopsis concavus Senna, 2007 was collected in several localities off the coast of Bahia and Espírito Santo States, including the islands and submerged mounts of the Vitoria-Trindade Chain, at depths from 40 to 108 m.

Figures

FIGURE 10. Lysianopsis concavus Senna, 2007, female 7.0 mm, 14 º 48 ’ 30 ” S – 38 º 55 ’ 00 ” W, 20 m, July 1, 2001, MNRJ 18555. Scale bars: 1.0 mm for habitus; 0.05 mm for LL; 0.1 mm for the remainder.

FIGURE 11. Lysianopsis concavus Senna, 2007, female 7.0 mm, 14 º 48 ’ 30 ” S – 38 º 55 ’ 00 ” W, 20 m, July 1, 2001, MNRJ 18555. Scale bars: 0.1 mm for Gn 1; 0.05 mm for the remainder.

FIGURE 12. Lysianopsis concavus Senna, 2007, female 7.0 mm, 14 º 48 ’ 30 ” S – 38 º 55 ’ 00 ” W, 20 m, July 1, 2001, MNRJ 18555. Scale bars: 0.05 mm for U 1 – 2; 0.1 mm for the remainder.