Coronaurothoe rotunda, 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 : 545-550

Coronaurothoe rotunda gen. nov. et sp. nov.

( Figures 7–9 )

Material examined

Holotype: sex unknown, 3.0 mm, Oceanprof II #59, 21°52 ′ 59 ″ S, 39°55 ′ 32 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21443 .

Paratypes: 1 specimen, sex unknown, 3.5 mm, Oceanprof II #59, 21°52 ′ 59 ″ S, 39°55 ′ 32 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21444 ; 1 female, 4.3 mm, Oceanprof I #69, 22°31 ′ 12 ″ S, 40°15 ″ 11 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21445 ; 1 specimen, sex unknown, 3.0 mm, Oceanprof I #74, 22°27 ′ 31 ″ S, 40°09 ′ 23 ″ W, 750 m, N/ R Astro Garoupa col., MNRJ 21446 ; 1 specimen, sex unknown, 3.5 mm, Campos Basin , depth data and collector unknown, MNRJ 18320 .

Etymology

From Latin rotundus (rounded), referring to the rounded projection present at the anteroventral corner of the head.

Diagnosis

As for genus.

Description

Head without eyes; rostrum absent; anteroventral corner produced into rounded process. Antenna 1 peduncular article 1 with two slender setae on anterior margin; primary flagellum 4-articulate and 2.6 times as long as peduncular article 3; accessory flagellum absent. Antenna 2 reaching end of peduncular article 2 of antenna 1; peduncular article 4 as long as article 5, anterior margin with five slender setae, facial margin with two long setae; peduncular article 5 anterior margin with five slender setae. Upper lip rounded distally. Mandible molar present, large and triturative; right mandible lacinia mobilis 5-dentate; left mandible lacinia mobilis 4-dentate, accessory setal row absent; incisor process well developed, large and smooth; palp article 2 longer than article 3, with one marginal seta; article 3 with four distal setae. Maxilla 1 inner plate with one distal pappose seta and three short setae; outer plate with nine robust setae; palp article 1 shorter than article 2 (0.12 times); article 2 with six 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 about one-half length of palp article 2, with seven marginal robust setae; palp article 2 expanded, twice as long as wide, inner distal margin produced, inner margin densely setose; article 3 widened distally; article 4 0.3 times of article 3, with a slender distal setae.

Gnathopod 1 coxa rectangular, twice as long as wide, anteroventral corner subquadrate, posteroventral angle with a notch bearing a seta; basis long and slender, widened distally, posterior margin with four long setae; carpus slightly shorter than propodus, posterior margin slightly lobate and poorly setose; propodus with a tuft of setae on anterodistal angle; palm extremely acute, excavated and longer than posterior margin, with two long and robust setae near palmar corner; dactylus stout, as long as propodus. Gnathopod 2 coxa rectangular, 2.9 times longer than wide, posteroventral angle with a notch; basis long and slender, widened distally, posterior margin with one long seta; carpus 1.2 times longer than propodus, posterior margin not lobate and poorly setose; propodus facial margin setose; palm acute, shorter than outer margin, with one robust seta on palmar corner; dactylus stout, as long as palm. Pereopod 3 coxa twice as long as wide, with one seta on posteroventral angle; basis 2.5 times longer than wide, with one seta on posterodistal angle; merus with two setae on posterior margin, shorter than carpus and propodus combined; carpus moderately robust, 1.5 times longer than wide, with six long robust setae on posterior margin; propodus more slender than carpus, with four robust setae on posterior margin; dactylus short, 0.8 times propodus length. Pereopod 4 coxa almost as long as wide, posterior margin excavate with posteroventral angle produced into rounded process; basis 3.3 times longer than wide, with one short seta on posterodistal angle; merus with two long setae on posterior margin, longer than carpus and propodus combined; carpus moderately robust, 1.7 times longer than wide, with seven long robust setae on posterior margin; propodus more slender than carpus, with three robust setae on posterior margin; dactylus short, 0.75 times propodus length. Pereopod 5 coxa slightly wider than long, with posteroventral lobe produced; basis ovate, 1.3 times longer than wide, posterior margin slightly sinuous, distally notched, with two short setae; merus as long as wide, anterodistal angle with a robust seta; posterodistal angle with a robust seta; carpus 2.3 times longer than wide, anterior margin with two combs of robust setae (2–2), posterior margin with two combs of setae (2–2); propodus shorter than carpus, 2.75 times longer than wide, anterior margin with two combs of setae (2–2), posterodistal angle with two slender setae; dactylus styliform, 1.6 times longer than propodus. Pereopod 6 coxa 1.7 times wider than long, with produced posteroventral lobe; basis ovate, 1.8 times longer than wide, posterior margin smooth, lacking setae; merus 1.9 times longer than wide, anterior margin with two combs of setae (1–2), posterior margin with two setae on posterodistal angle; carpus 2.9 times longer than wide, anterior margin with two combs of slender setae (3–3), posterodistal angle with three slender setae; propodus about 0.7 times carpus length, 3.6 times longer than wide, anterior margin with two setae midway, distal margin with five slender setae; dactylus long, 1.4 times longer than propodus. Pereopod 7 coxa 1.2 times wider than long, with posteroventral lobe not produced; basis ovate, 1.4 times longer than wide, posterior margin smooth lacking setae; merus 1.3 times longer than wide, anterodistal angle with two seta, posterodistal angle with one long seta; carpus 2.5 times longer than wide, anterior margin with two combs of slender setae (3–5), posterior margin with a slender seta midway, posterodistal angle with three slender setae; propodus shorter than carpus, 3.8 times longer than wide, anterior margin with one middle comb of six slender setae, distal margin with six slender setae; dactylus short, 0.5 times of propodus length.

Epimeral plates 1–3 each with ventral margin lacking setae and with posteroventral angle acute. Uropod 1 peduncle 0.7 times shorter than rami, with one robust seta on both inner and outer distal angle; rami subequal in length and naked. Uropod 2 peduncle shorter than rami (0.85 times), with one facial robust seta, inner margin with four robust setae, outer margin with one robust seta; rami subequal in length and naked. Uropod 3 about 0.7 times the uropod 2 length and 0.5 times the uropod 1 length, peduncle 1.2 times longer than wide, 0.47 times shorter than outer ramus, distal outer angle with two robust setae; rami lanceolate; inner ramus subequal to article 1 of outer ramus, with one long seta on inner margin, with one apical long pappose seta; outer ramus 2-articulate, article 1 1.3 times longer than article 2, outer margin distal angle with one robust seta; article 2 with one apical long and pappose seta and one short seta. Telson cleft (about 40%), lateral margins with two short setae; distal margin of each lobe weakly incised distally with one robust seta.

Variation

Paratypes showed variation in number of pappose setae on the ventral margin of both epimeral plates 1 and 2, and the flagellum of antenna 1, that varied from 4- to 5- articulate.

Remarks

Coronaurothoe rotunda gen. et sp. nov. is easily distinguished from other species in the family Urothoidae by its mandible molar, palp of maxilla 1 and palp of maxilliped. However, this species shares some features with species of other urothoid genera. Thus, the lacinia mobilis in Coronaurothoe rotunda gen. et sp. nov. is present, as in almost all species of the family. Only Carangolia and some species of Urothoides lack the lacinia mobilis. The new species has a rounded apical margin of the upper lip, as in Urothoides . The lower lip of Coronaurothoe rotunda gen. et sp. nov. does not have a distolateral process, as in Carangolia and Urothoides species. Finally, the new species has pereopod 7 subequal in length to pereopod 6, as in the other four genera of Urothoidae . Only Urothoides shares the phoxocephalid-like pereopod 7 with the new taxon, which is much shorter than pereopod 6.

Geographic distribution

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

Bathymetric range

Collected at 750 m depth.

Key to genera of the family Urothoidae

1. Uropod 2 lacking rami ....................................................... Cunicus Griffiths, 1974 Uropod 2 biramous ............................................................................................. 2

2. Pereopod 7 shorter than pereopod 6, phoxocephalid-type ................................. .................................................................................. Urothoides Stebbing, 1891 Pereopod 7 subequal in length to pereopod 6, not phoxocephalid-type .............. 3

3. Uropod 3 rami foliaceous ....................................................... Urothoe Dana, 1852 Uropod 3 rami not foliaceous ............................................................................. 4

4. Lower lip outer lobe with distolateral projection; upper lip, distal margin truncated ......................................................................................... Carangolioides gen. nov. Lower lip outer lobe without distolateral projection; upper lip, distal margin not truncated .............................................................................................................. 5

5. Mandible molar with crown of stout setae; article 2 of maxilliped palp, distomedial corner produced into a blunt process .............................. Coronaurothoe gen. nov. Mandible molar and lacinia mobilis absent; incisor strongly developed ................ ....................................................................................... Carangolia Barnard, 1961

Figures

Figure 7. Coronaurothoe rotunda gen. et sp. nov., sex unknown, 3.0 mm, 21°52′59″ S, 39°55′32″ W, 750 m depth, MNRJ 21443. Scale bars: 0.2 mm for Hd; 0.1 mm for all others.

Figure 8. Coronaurothoe rotunda gen. et sp. nov., sex unknown, 3.0 mm, 21°52′59″ S, 39°55′32″ W, 750 m depth, MNRJ 21443. Scale bars: 0.1 mm for U1; 0.2 mm for U2°3; 0.5 mm for all others.

Figure 9. Coronaurothoe rotunda gen. et sp. nov., sex unknown, 3.0 mm, 21°52′59″ S, 39°55′32″ W, 750 m depth, MNRJ 21443. Scale bars: 0.5 mm.