Monocorophium josei, Valério-Berardo, Maria Teresa & Souza, Ana Maria Thiago De, 2009

Valério-Berardo, Maria Teresa & Souza, Ana Maria Thiago De, 2009, Description of two new species of the Corophiidae (Amphipoda, Crustacea) and register of Laticorophium baconi (Shoemaker, 1934) from Brazilian waters, Zootaxa 2215, pp. 55-68 : 64-68

Monocorophium josei sp. nov.

Figures 6–8 .

Material examined: Holotype, female, 4.0 mm, 24º30’94” S – 46º49’65” W, 19 m, col. N/Pq W. Besnard, II/ 2006, MZUSP 19615; Paratypes: 24º30’94” S – 46º49’65” W, 19 m, col. N/Pq W. Besnard, II/2006, MZUSP 19616, 2 males and 1 female.

Etymology: The species is dedicated to the first author’s younger son.

Diagnosis: Rostrum short. Female antenna 1 peduncular article 1 with 1 distal and 1 proximal robust setae on ventral margin, proximal dorsomedial margin with 2 robust setae. Male antenna 1 proximal dorsomedial margin with 1 spine. Female antenna 2 peduncular article 4 with 1 single short acute process on distoventral corner. Male antenna 2 peduncular article 4, ventrodistal margin with 1 large and 1 small spine; peduncular article 5 with small proximal process on ventroanterior margin. Gnatopod 1 on female with dactylus reaching to corner of palm, but in gnathopod 1 of male distinctly exceeding the palm. Gnathopod 2 dactylus with 3 spines on posterior margin. Pereopod 4 basis distinctly broader than pereopod 3 basis. Uropod 2 inner ramus outer margin with 1 medial robust seta.

Description. Holotype. Female: 4.0 mm. Head ( Fig. 6 ) with rostrum short, broad, not recessed and not exceeding lateral head lobes; eyes well developed. Antenna 1 ( Fig. 6 ) peduncle articles sparcely setose, article 1 with 1 distal and 1 proximal robust setae on ventral margin, proximal dorsomedial margin with 2 robust setae; article 2 0.6 X longer than article 1; flagellum with 5–6 articles. Antenna 2 ( Fig. 6 ) pediform; peduncular article 3 square, with 2 robust setae on ventral margin; peduncular article 4 length 1.2 X breadth, distoventral corner with 1 single short acute process, dorsomedial margin with 3 spines; article 5 with 1 spine on dorsomedial margin and with 1 acute process on distoventral corner; flagellum with 2 articles. Mandible ( Fig. 6 ) incisor with 3 teeth, lacinia mobilis similar to incisor, accessory setal row with 2 plumose setae and 3 robust setae, molar with lower distal margin with 7 setae; palp proximal article distal margin with a square projection and 1 long pinnate setae, distal article attached at an angle with proximal one. Maxilla 1 ( Fig. 6 ) palp exceeding outer plate, distal margin with 5 robust setae; outer plate with 7 robust setae. Maxilla 2 ( Fig. 6 ) inner and outer plate with a row of plumose setae. Maxilliped ( Fig. 6 ) inner plate not broad, distal margin with 4 plumose setae; outer plate with a row of plumose setae along inner margin; palp 4-articulate, 2 proximal articles twice longer than 2 distal articles, article 4 with 1 distal robust seta.

Gnathopod 1 ( Fig. 7 ) coxa anterior margin acute, with 3 long plumose setae; basis slender, length 3.5 X breadth, with 1 long seta on posterodistal corner; ischium with 6 long plumose setae on posterodistal margin; merus length about ½ ischium length; carpus length 2 X breadth, with a row of plumose setae along posterior margin and 3 setae on anterodistal margin; propodus subequal in length to carpus and length 2 X breadth, with 3 long setae along posterior margin and 2 long setae on anterodistal corner; palm serrate, with 4 robust setae; dactylus reaching to corner of palm, posterior margin serrate and with 1 medial spine. Gnathopod 2 ( Fig. 7 ) coxa rectangular and with ventral margin rounded; basis broad, length 1.3X breadth, with 1 short simple seta on posterodistal margin; ischium very short, rectangular, with 1 short simple seta on posterodistal margin; merus subequal in length to basis, with 2 long simple setae and a row a long plumose setae along posterior margin, reaching near apex of distal margin of carpus; carpus subtriangular, increasing in width, with 2 simple seta on anterior margin and 3 simple setae on posterior margin; propodus twice longer than carpus, posterior and lateral margins with long facial pectinate setae; dactylus posterior margin with 3 teeth.

Pereopod 3 ( Fig. 7 ) coxa short and ovate; basis elongate, inflated medially, length 1.8 X breadth; ischium short, as long as wide; merus about ½ basis length, anterodistal margin produced, with 4 simple setae; carpus broader than longer, narrow proximally, with 4 plumose setae on posterior margin; propodus longer than carpus, with 3 plumose setae and 3 simple setae along posterior margin and 2 simple seta on anterodistal corner; dactylus is about as long as propodus, falcate. Pereopod 4 ( Fig. 7 ) coxa very short; basis broad, length 1.4 X breadth; others articles similar to pereopod 3, except for number of setae. Pereopod 5 ( Fig. 7 ) coxa bilobate; basis as long as broad, inflated medially, with 4 simple setae along posterior margin and 1 simple seta on anterior margin; ischium ½ long as merus, with 2 simple setae on posterodistal corner; merus twice longer than carpus, with 2 simple setae on posterior margin, 3 simple setae on anterodistal corner; propodus elongate, twice longer than carpus, with 2 simple setae on posterodistal corner and 4 simple setae along anterior margin; dactylus curved anteriorly and small. Pereopod 6 ( Fig. 7 ) basis 1.3 X longer than broad; others articles similar to pereopod 5, except for number of setae. Pereopod 7 ( Fig. 7 ) elongate, basis length 1.6 X breadth, with a row of simple setae on posterior margin and a row of plumose setae on anterior margin; ischium about ½ merus length,with 1 simple seta on anterodistal margin; merus with 3 simple setae along anterior and posterior margins; carpus subequal in length to merus, with simple setae along anterior and posterior margins; propodus with simple short setae along anterior margin, half distal posterior margin and posterodistal corner with long simple setae; dactylus smooth on anterior margin, with 1 short plumose seta on posteroproximal margin.

Epimeral plate 1 ( Fig. 6 ) smooth on ventral margin; epimeral plate 2 with 3 long plumose setae on ventral margin. Pleopods 1–3 ( Fig. 8 ) similar to each other; peduncle stout, breadth 1.4 X length, outer margins with plumose setae, inner margins with 2 coupling spines; rami with basal articles longer and broader than distal articles, inner ramus little longer than outer ramus.

Urosomites 1 – 3 ( Fig. 8 ) fused, with lateral marginal ridge of urosome smooth. Uropod 1 ( Fig. 8 ) inserted ventrolaterally and reaching the end of uropod 2; peduncle twice longer than rami with 1 spine interamal, outer margin with 5 robust setae; outer and inner rami with 5 robust setae along outer margins and 1 apical robust seta. Uropod 2 ( Fig. 8 ) half uropod 1 length; peduncle outer margin with 3 simple setae; outer ramus broader than inner ramus, with outer margin with a row of setules and 3 setae; inner ramus outer margin with 1 medial setae; both rami with 1 robust seta on apex. Uropod 3 ( Fig. 8 ) uniramous; peduncle breadth 1.5 X length, with a row of setules and setae on outer margin; ramus ovate, subequal in length to peduncle, with setae on outer and apical margins and a row of setules on outer margin. Telson ( Fig. 8 ) small, broadly subtriangular.

Male: 4.5 mm. Head ( Fig. 6 ) rostrum little longer than female. Antenna 1 ( Fig. 6 ) peduncle articles 1 and 2 with long setae on ventral margin, article 1 with 1 proximal and 1 medial spine on ventral margin, proximal dorsomedial margin with 1 spine; article 2 0.9X article 1 length; flagellum with 6 articles. Antena 2 ( Fig. 6 ) pediform, peduncular article 3 square, article 4 1.4 X longer than article 5, ventrodistal margin with 1 large and 1 small spine; peduncular article 5 with small proximal process on ventromedial margin; flagellum 3- articulate. Gnathopod 1 ( Fig. 7 ) dactylus slender, distinctly exceeding the palm.

Remarks: Monocorophium josei sp. nov. is unique among Monocorophium species with short rostrum, in having a pereopod 3 basis narrower than pereopod 4 basis and evident sexually dimorphic antenna 2. Other diagnostic character observed only in this species of the genera is the sexually dimorphic palm of gnathopod 1. The female has dactylus only overlapping the palm, but in the male the dactylus distinctly exceeding the palm.

Another species of the genera registered in Brazilian coast by Serejo (1998) was Monocorophium acherusicum (Costa, 1851) . Although in this cosmopolitan species, there are variations in the number of robust setae and spines on antennae, that observed by Serejo (1998) the M. josei sp. nov. is easily distinguished from it by having: male antenna 1 peduncular article 1 with 1 small proximal spine on dorsomedial margin (absent in C. acherusicum ); female antenna 1 peduncular article 1 with 2 robust setae on dorsomedial and ventral margins (3 – 5 strong spines in C. acherusicum ); rostrum short and broad, not deeply recessed; pereopod 7 carpus slender and without protuberance on anterior margin.

Figures

FIGURE 6. Monocorophium josei sp. nov. female 4 mm (MZUSP 19615). Scale bars = 0.1 mm.

FIGURE 7. Monocorophium josei sp. nov. female 4 mm (MZUSP 19615). Scale bars = 0.1 mm.

FIGURE 8. Monocorophium josei sp. nov. female 4 mm (MZUSP 19615). Scale bars = 0.1 mm.