Carangolioides hamatus, Sittrop & Serejo & Souza-Filho & Senna, 2014

Sittrop, Daniela J. P., Serejo, Cristiana S., Souza-Filho, Jesser F. & Senna, André R., 2014, New genera and species of Urothoidae (Amphipoda) from the Brazilian deep sea, with the re-assignment of Pseudurothoe and Urothopsis to Phoxocephalopsidae, Journal of Natural History 49 (9), pp. 527-552 : 539-544

Carangolioides hamatus gen. nov. et sp. nov.

( Figures 4–6 )

Material examined

Holotype: female, 5.4 mm, Oceanprof II #49, 22°04 ′ 32 ″ S, 39°54 ′ 11 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ21434 .

Paratypes: 1 specimen, sex unknown, 4.3 mm, 1 male, 4.3 mm, 1 female, 4.3 mm, Oceanprof II #49, 22°04 ′ 32 ″ S, 39°54 ′ 11 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21435 ; 1 specimen, sex unknown, 4.7 mm, Oceanprof I #64, 22°36 ′ 03 ″ S, 40°21 ′ 45 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21436 ; 2 specimens, sex unknown, 2.0 to 3.8 mm, Oceanprof I #54; 21°57 ′ 17 ″ S, 39°56 ″ 01 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21437 ; 1 female, 4.7 mm, Oceanprof II #79, 22°20 ′ 22 ″ S, 40°01 ′ 24 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21438 .

Etymology

The species name is a Latin adjective hamatus (hooked), and refers to the hookshaped posteroventral corner on the epimeral plate 3.

Diagnosis

Head without rostrum; anteroventral angle with a sharp projection. Lacinia mobilis dentate. Gnathopod 1 and 2 palm longer than posterior margin of corresponding propodus. Coxa 4 with excavated posterior margin, posteroventral angle acute and produced. Pereopod 5 basis with smooth posterior margin. Epimeral plate 3

posteroventral angle produced into a large hook. Uropod 1 and 2 rami with robust setae.

Description

Head without eyes; rostrum absent; anteroventral corner produced into a curved acute and long spine. In the illustration this projection slightly overlaps the anteroventral margin of the head. Antenna 1 peduncular article 1 with five slender setae on posterior margin; primary flagellum 5-articulate and subequal in length to peduncular article 3; accessory flagellum present, 3-articulate. Antenna 2 reaching end of peduncular article 2 of antenna 1; peduncular article 4 longer and stouter than article 5, with row of 14 robust setae on anterior margin, and row of seven long setae on lateral surface; article 5 with row of nine robust setae on anterior margin, and two long setae on posterior margin. Mandible molar present, non-triturative; right mandible lacinia mobilis 5-dentate; left lacinia mobilis bifid, accessory setal row present, with four simple setae; incisor process well developed, of moderate length and smooth; palp article 2 longer than article 3, with three marginal setae; article 3 with one subdistal and six distal long setae. Maxilla 1 inner plate with three distal pappose setae; outer plate with nine robust setae; palp article 1 1.6 times longer than article 2; article 2 with three distal pappose setae. Maxilla 2 outer plate wider than inner plate, both with long setae on distal margin. Maxilliped inner plate with three apical robust setae, outer plate reaching two-thirds of palp article 2, with seven marginal robust setae; palp article 2 expanded, 1.8 times longer than wide, distomedial margin produced, medial margin densely setose; article 3 widened distally; article 4 half length of article 3, with a slender distolateral seta.

Gnathopod 1 coxa rectangular, longer than wide (2.5 times), anteroventral angle rounded and posteroventral angle about 90°; basis long and slender, widened distally, posterior margin with four long setae, facial margin with two combs of long setae (5–7); carpus slightly longer than propodus, posterior margin slightly lobate and densely setose; propodus with a tuft of setae on anterodistal angle; palm acute, longer than outer margin, with six long setae and one robust seta near palmar corner; dactylus stout, longer than propodus. Gnathopod 2 coxa rectangular, longer than wide (2.4 times), anteroventral angle rounded and posteroventral angle about 90°; basis long and slender, widened distally, posterior margin with 16 long setae, facial margin with five long setae; carpus slightly longer than propodus, posterior margin not lobate and densely setose; propodus facial margin densely setose; palm acute, longer than outer margin, with eight long setae defining palmar corner; dactylus moderately stout, as long as palm. Pereopod 3 coxa longer than wide (1.8 times), with two setae on posteroventral angle; basis 2.3 times longer than wide, with one seta on posterodistal angle; merus with a row of oblique and facial setae, longer than propodus and carpus together; carpus robust 1.1 times longer than wide, with nine robust and long setae on posterior margin; propodus more slender than carpus, with five robust setae on posterior margin; dactylus short, 0.7 times propodus length. Pereopod 4 coxa longer than wide (1.2 times), posterior margin excavate with posteroventral angle produced into an acute process; basis 2.6 times longer than wide, with three plumose setae on posterodistal angle; merus with a row of oblique and facial setae, longer than propodus and carpus together; carpus robust 1.25 times longer than wide, with nine robust and long setae on posterior margin; propodus more slender than carpus, with seven robust setae on posterior margin; dactylus short, 0.9 times propodus length. Pereopod 5 coxa wider than long (1.2 times), with posteroventral lobe produced; basis ovate, longer than wide (1.4 times), posterior margin smooth with five long setae; merus as long as wide, posterodistal angle with a very long plumose seta and one short seta; carpus 1.3 times longer than wide, anterior margin with two combs of robust setae (7–6), posterior margin with two combs of setae (5–5), posterodistal angle with three very long setae; propodus as long as carpus, 2.3 times longer than wide, anterior margin with one proximal comb of two robust setae and one middle and distal combs of slender setae (3–3), posterior margin with one comb of robust setae (3), posterodistal angle with two slender setae; dactylus styliform, 1.1 times longer than propodus. Pereopod 6 coxa wider than long (1.4 times), with posteroventral lobe slightly produced; basis ovate, longer than wide (1.3 times), posterior margin smooth with a row of 11 facial very long plumose setae; merus longer than wide (2.3 times), anterior margin with nine slender setae, posterior margin with seven slender setae and one robust seta on posterodistal angle; carpus 2.1 times longer than wide, anterior margin with three combs of slender setae (2-2-7), posterodistal angle with six slender setae; propodus as long as carpus, 2.2 times longer than wide, anterior margin with one middle comb of three slender setae, distal margin with five slender setae; dactylus short, 0.8 times longer than propodus. Pereopod 7 coxa wider than long (1.3 times), with posteroventral lobe not produced; basis ovate, longer than wide (1.25 times), posterior margin smooth, lacking setae; merus longer than wide (1.2 times), anterior margin with four slender setae, posterior margin with two combs of slender setae (2–5); carpus 2.4 times longer than wide, anterior margin with three combs of slender setae (2-2-7), posterodistal angle with six slender setae; propodus as long as carpus, 2.2 times longer than wide, anterior margin with one middle comb of three slender setae, distal margin with five slender setae; dactylus short, 0.8 times of propodus length.

Epimeral plate 1 ventral margin with four pappose setae; posteroventral angle acute. Epimeral plate 2 ventral margin with four pappose setae; posteroventral angle acute and slightly produced. Epimeral plate 3 ventral margin lacking setae, posteroventral angle strongly produced into an upturned acute spine. Uropod 1 peduncle shorter than rami (0.7 times), both inner and outer margins with four robust setae; inner ramus slightly shorter than outer ramus, with two medial robust setae; outer ramus with three robust setae. Uropod 2 peduncle shorter than rami (0.8 times), inner margin with three robust setae, outer margin with one robust seta on distal angle; inner ramus glabrous and subequal outer ramus; outer ramus with one medial robust seta. Uropod 3 slightly longer than uropod 2 and 0.6 times the uropod 1 length, peduncle wider than long (1.2 times), shorter than outer ramus (0.6 times), distal inner angle with one robust seta, distal outer angle with two robust setae; rami foliaceous; inner ramus shorter than article 1 of outer ramus, inner margin with four long setae and two distal pappose setae; outer ramus 2-articulate, article 1 3.3 times longer than article 2, inner margin with three slender setae, outer margin with three robust setae and one long seta; article 2 with two distal pappose setae. Telson deeply cleft (up to 70% length), lateral margins each with two short setae; distal margin of each lobe weakly incised distally with one robust seta.

Variation

Paratypes showed variation in the number of setae on the ventral margin of both epimeral plates 1 and 2, and in the number of long setae in the facial row on the basis of pereopod 6, which varied from 9 to 12.

Remarks

Apart from the generic differences, Carangolioides hamatus gen. et sp. nov. shows some similarities with Urothoe falcata . At a glance, both species can be differentiated by epimeral plate 3, which has the posteroventral angle strongly produced into an upturned acute spine in the new species. However, C. hamatus sp. nov. differs from the latter in having the palm of gnathopod 2 longer than the posterior margin of the propodus; the posterior margin of pereopod 7 smooth versus dentate; basis of pereopod 6 not widened distally; coxa 7 lacking a posteroventral lobe; and the inner ramus of uropod 3 shorter than article 1 of the outer ramus, versus subequal.

Geographic distribution

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

Bathymetric range

Collected at 750 m depth.

Figures

Figure 4. Carangolioides hamatus gen. et sp. nov., holotype, female, 5.4 mm, 22°04′32″ S, 39°54′11″ W, 750 m depth, MNRJ21434. Scale bars: 0.5 mm for Hd; 0.2 mm for A1–2, Md, Mp, UL; 0.1 mm for all others.

Figure 5. Carangolioides hamatus gen. et sp. nov., holotype, female, 5.4 mm, 22°04′32″ S, 39°54′11″ W, 750 m depth, MNRJ21434. Scale bars: 0.1 mm for T; 0.2 mm for U1–3; 0.5 mm for all others.

Figure 6. Carangolioides hamatus gen. et sp. nov., holotype, female, 5.4 mm, 22°04′32″ S, 39°54′11″ W, 750 m depth, MNRJ21434. Scale bars: 0.5 mm.