Shoemakerella subchelata, Sorrentino, Rayane, Senna, André R. & Lowry, James K., 2014

Sorrentino, Rayane, Senna, André R. & Lowry, James K., 2014, A new species and first record of the genus Shoemakerella Pirlot, 1936 (Crustacea: Amphipoda: Lysianassidae) from Brazil, Zootaxa 3784 (4), pp. 484-492 : 485-491

Shoemakerella subchelata sp. nov.

( Figs 1–5 )

Etymology. The specific epithet refers to the concavity in the palm of gnathopod 2, which makes it strongly subchelate.

Material examined. Holotype, female, 5 November 1970, 22º00'S, 40º06'W, off Quissamã, Northern coast of Rio de Janeiro state, 90 m depth, in algae Laminaria, Mini Biological Trawl, UFBA 1601. Paratypes: 2 females, 5 November 1970, 22º00'S, 40º06'W, off Quissamã, Northern coast of Rio de Janeiro state, 90 m depth, in algae Laminaria, Mini Biological Trawl, UFBA 1602.

Diagnosis. Lateral cephalic lobe well developed, subtriangular, apically rounded, compound eyes trapezoidal. Antenna 1, approximately 1.4 × the length of antenna 2, primary flagellum with 12 articles and accessory flagellum with 6 articles, all distally setose. Maxilla 1, outer plate, setal-teeth producing a distal corona in a 7/4 formation; ST1–3 1-cuspidate, ST4 2-cuspidate, ST5 3-cuspidate, ST6–7 multicuspidate, STA simple and subconical, STB-D apically bifid. Gnathopod 2 strongly subchelate, propodus, subtrapezoidal, distally broadened, anterodistal corner truncate with a tuft of stout setae, palm scarcely setose, palmar corner produced and rounded, covered by small scales; dactylus with a robust unguis, curved, small setae on the inner margin, not reaching the palmar corner.

Description. Body, dorsal margin without setae. Lateral cephalic lobe well developed, subtriangular, apically rounded, compound eyes trapezoidal. Antenna 1, approximately 1.4 × the length of antenna 2, article 1 of peduncle robust, 1.6 × longer than wide and double the length of article 2, article 2 approximately 1.75 × the length of article 3, with a tuft of slender setae in the distal corner, primary flagellum with 12 articles and accessory flagellum with 6 articles, all distally setose. Antenna 2, article 2 approximately 1.5 × longer than wide and approximately 9 × the length of article 3, article 4 1.8 × longer than wide, dorsal margin setose, ventral margin with one seta, small, slender and plumose, distal margin with four simple slender setae followed by a small plumose seta, article 5 elongate, 2.5 × longer than wide and 1.25 × longer than article 4, dorsodistal and ventrodistal corners with tufts of simple long setae, flagellum 8-articulate.

Mouthparts forming a subquadrate bundle. Epistome and labrum fused to each other, defined by a small and subtle cleft. Epistome dorsally concave and less produced than labrum. Labrum dorsally produced and rounded, apical margin covered by small simple setae. Right mandible, incisor smooth, convex and laminar; molar rounded, as a not triturative lobe, with the row of stout setae followed by the row of slender setae; lacinia mobilis absent; accessory row of setae composed with three stout setae below the molar; palp 3-articulate, article 1 about 2 × longer than wide, without setae, article 2 approximately 3.9 × the length of article 1, dorsal and ventral margins without setae, with 3 setae in the dorsodistal corner, article 3 covered by setules on its whole surface, with two apical setae. Maxilla 1, outer plate, with 11 setal-teeth in 6/5 arrangement; ST1–3 large, stout, 1-cuspidate, ST4 2- cuspidate, ST5 3-cuspidate, ST6–7 multicuspidate, STA simple and subconical, STB-D apically bifid. Maxilla 2, inner plate 2.3 × the width of the outer plate, with simple setae posteriorly, distal margin with row of setae; anterior plate with anterodistal marginal setae. Maxilliped, inner plate suboval, small, submarginal setae and nodular setae present; outer plate rounded, distal margin smooth, anterodistal corner with submarginal setae; palp well developed, 4-articulate, article 1 with 3 setae, articles 2 and 3 with inner margin densely setose, dactylus curved and without setae.

Gnathopod 1 simple; coxa well developed, not covered by coxa 2; basis short, rows of setae in the anterior part, 3.7 × as long as the ischium; propodus tapering distally, without denticulate patch near posterodistal margin; dactylus simple, curved. Gnathopod 2 strongly subchelate, coxa 2.5 × as long as wide, with small posteroventral notch, basis long, 1.8 × longer than the ischium, posteriorly curved; ischium long, 3 × as long as wide; merus rounded in the posterodistal margin, with tuft of setae; carpus expanded posteriorly, with setae on the side and 10 large setae in the anterodistal margin; propodus, subtrapezoidal, distally broadened, anterodistal corner truncate with one tuft of stout setae, anterior margin setose, palm acute, concave, slightly setose, palmar corner produced and rounded, covered by small scales; dactylus with a robust unguis, curved, small setae in the inner margin, not reaching the palmar corner.

Pereopod 3, coxa 2.4 × longer than wide; merus, margin slightly expanded anteroventrally, with one seta; dactylus simple. Pereopod 4, coxa expanded posteroventrally, anteroventral corner rounded. Pereopod 5, coxa rounded in the distal margin. Pereopod 6, coxa small; anterodistal margin expanded, posterior margin densely setose, concave. Pereopod 7, coxa small, posterior margin serrate, concave, anterior margin setose. Epimeral plate 1, posterior margin retracted and convex. Epimeral plate 2, posterior margin quadrate, anterior margin rounded with three setae. Epimeral plate 3, posterior margin straight, posteroventral corner rounded, with 1 anterior seta.

Uropod 1, peduncle with 3 dorsal setae; rami of subequal length. Uropod 2, peduncle with five setae; outer ramus with five setae; inner ramus with three setae and constriction present. Uropod 3, peduncle, dorsolateral flange present, with three small dorsal setae; outer ramus 1-articulate. Telson entire, slightly longer than wide, apical margin slightly concave, with asymmetrical setation, with one small stout seta and three submarginal plumose setae.

Geographic distribution and bathymetry. The new species is known only from the type locality, 22º00'S, 40º06'W, off Quissamã, Northern coast of Rio de Janeiro State, 90 m depth.

Remarks. Shoemakerella subchelata sp. nov. can be easily distinguished from the other species in the genus by: maxilla 1 STA simple and subconical; gnathopod 2 strongly subchelate, with propodus, subtrapezoidal, distally broadened, palm acute, concave, and palmar corner produced and rounded.

In addition, the basis of pereopod 7 in S. subchelata sp. nov. has a concave posterior margin, similar to the Australian species, S. barnardi , not present in S. cubensis or S. lowryi . Shoemakerella subchelata sp. nov. differs from S. barnardi in having a concave posterior margin on the basis of pereopod 6 and a slightly concave apical margin on the telson. The Australian species, S. barnardi , has a slightly convex posterior margin on the basis of pereopod 6 and the apical margin of telson is rounded to angulate.

The genus was known until now only from the western North Atlantic Ocean and the Indo-West Pacific Ocean ( Lowry & Stoddart 2009). Shoemakerella . subchelata is the first record of Shoemakerella from the South Atlantic Ocean.

Figures

FIGURE 1. Shoemakerella subchelata sp. nov.: female, holotype, off Quissamã, Rio de Janeiro state, Brazil, 22 º 00 ' S – 40 º 06 ' W, UFBA 1601. Scale bars: 0.1 mm for A 1 - 2; 0.5 mm for the remains.

FIGURE 2. Shoemakerella subchelata sp. nov.: female, holotype, off Quissamã, Rio de Janeiro state, Brazil, 22 º 00 ' S – 40 º 06 ' W, UFBA 1601. Scale bars: 0.1 mm.

FIGURE 3. Shoemakerella subchelata sp. nov.: female, holotype, off Quissamã, Rio de Janeiro state, Brazil, 22 º 00 ' S – 40 º 06 ' W, UFBA 1601. Scale bars: 0.5 mm.

FIGURE 4. Shoemakerella subchelata sp. nov.: female, holotype, off Quissamã, Rio de Janeiro state, Brazil, 22 º 00 ' S – 40 º 06 ' W, UFBA 1601. Scale bars: 0.5 mm.

FIGURE 5. Shoemakerella subchelata sp. nov.: female, holotype, off Quissamã, Rio de Janeiro state, Brazil, 22 º 00 ' S – 40 º 06 ' W, UFBA 1601. Scale bars: 0.5 mm for Ep 1 - 3; 0.1 mm for the remains.