Cerapus jonsoni, Valério-Berardo, Maria Teresa, Souza, Ana Maria Thiago De & Rodrigues, Carina Waiteman, 2008

Valério-Berardo, Maria Teresa, Souza, Ana Maria Thiago De & Rodrigues, Carina Waiteman, 2008, Description of two new species of Ischyroceridae (Crustacea: Amphipoda) from the coast of Southeastern Brazil, Zootaxa 1857, pp. 55-65 : 56-59

Cerapus jonsoni sp. nov.

( Figs. 1 – 2 )

Material examined: Holotype, male, 4.0 mm, 24º10’17” S – 46º37’08” W, 14 m, col. N/Pq W. Besnard, VIII/ 2005, MZUSP 18445; Paratypes: 24°03’96” S – 46°22’38” W, 17.3 m, col. N/Pq W. Besnard. VIII/2005, MZUSP 18446, 2 males and 2 females; 25°02’14” S – 45°41’65” W, 94 m, col. N/Pq W. Besnard, VIII/2005, MZUSP 18477, 2 males and 2 females; 24º10’17” S – 46º37’08” W, 14 m, col. N/Pq W. Besnard, VIII/2005, MZUSP 18448, 2 females.

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

Diagnosis: Head rostrum acute, very short, length 0.2 X head. Antenna 1 about half body length article 1 longer than article 3 (1.2 X); flagellum 4-articulated. Antenna 2 shorter than antenna 1 (0.9 X); flagellum 4- articulated, article 1 longer than article 2 (2 X). Gnathopod 2 male carpochelate, palmar margin transverse, rounded excavate, posterodistal spine large, anterodistal spine small and serrate, located near articulation with propodus; propodus elongate, length 2.3 X breadth. Pereopod 5–7 dactylar accessory spine formula 1:1:1. Uropod 1 peduncle with ventrodistal crown of cuticular setose rounded projection.

Description: Holotype male 4.0 mm.

Head ( Fig. 1 ): rostrum acute, very short, length 0.2 X head, lateral cephalic lobe weakly produced, eyes large. Antenna 1 ( Fig. 1 ): setose, about half body length; peduncle rectangular, not produced anterodistally or medially; article 1 longer than article 3 (1.2 X); flagellum 4-articulated, article 1 longer than article 2 (2 X). Antenna 2 ( Fig. 1 ): setose; slightly shorter than antenna 1 (0.9 X); flagellum 4-articulated, article 1 longer than article 2 (2 X).

Mandible ( Fig. 1 ): incisor with 6 teeth; lacinia mobilis multidentate with 5 acessory setal row; molar process triturative; mandible palp article 2 with 3 medial setae, longer than article 3 (1.6 X), article 3 with 4 long distal setae. Maxilla 1 ( Fig. 1 ): inner plate not known; outer plate with 7 setae-teeth; palp 2-articulated with 5 apical robust setae and 3 subapical setae. Maxilla 2 ( Fig. 1 ): outer plate longer and slightly broader than inner plate, both plates apically setose. Maxilliped ( Fig. 1 ): inner plate subquadrate with 2 apical robust setae and a row of plumose and simple setae on distal margin; outer plate reaching to half of length of palp article 2, with 5 chisel-shaped robust setae along medial margin and apically with 2 long robust setae; palp, article 2 longer than articles 3 and 4 combined (1.2 X), article 3 setose distally, article 4 with 2 apical setae.

Pereon constricted between peraeonites 1–2. Peraeonite 1 with a very short sternal kell. Coxa 1 fused in peraeonite, coxae 3 and 4 bilobed, coxa 5 largest.

Gnathopod 1 ( Fig. 1 ):coxae with anterior margin acute; basis inflated distally, posteriodistal corner with 1 long seta; ischium smaller than merus (0.8 X), with 1 long seta on posterodistal corner; merus with 6 setae on posterodistal margin; carpus as long as broad, with medial and apical setae on posterior margin, with setae on anterodistal corner; propodus longer than carpus (1.3 X), palm subchelate, oblique, with pectinate and simple setae on posterior margin; dactylus elongate, closing along entire palm inner margin serrate. Gnathopod 2 ( Fig. 1 ): carpochelate; basis robust with 1 seta on posterodistal corner; ischium and merus short, with 1 seta on posterodistal corner; carpus enormous, length 1.4 X breadth, palmar margin transverse, corner produced into 1 strong spine with a rounded distal concavity and shorter serrated-spine nearly propodus articulation; propodus elongate, length 2.3 X breadth, with 3 small rounded projections along posterior margin; dactylus elongate, length 0.8X propodus, posterior margin crenulate, with 1 medial and 2 distal setae, closing along entire margin of large outer spine of carpus.

Pereopod 3 ( Fig. 1 ): basis length 1.8 X breath, without denticle along anterior margin; ischium short; merus short, as long as wide, anterodistal corner lobed, with 1 seta, posterodistal corner with 2 setae without ridges; carpus short, subequal in length to merus, with a row of pectinate setae along posterior margin and 2 setae on anterodistal corner; propodus with 5 setae along posterior margin and 2 apical setae; dactylus with 1 spine and 3 short setae on medial posterior margin. Pereopod 4 ( Fig. 2 ): basis length 1.3 X breadth; isquium and merus subequal in length; merus slightly lobed on anterodistal corner; carpus with setae on anterodistal and posterodistal corners; propodus with a row of pectinate setae along posterior margin; dactylus smooth on posterior margin. Pereopod 5 ( Fig. 2 ): coxa as long as wide, with 1 seta on ventral margin; basis length 1.2 X breadth; merus anterior lobe reaching to end of distal margin of carpus, posterior lobe with 2 plumose setae; dactylus short, uncinate with 1 recurved spine. Pereopod 6 ( Fig. 2 ): coxa without setal fringe on ventral margin, basis length 1.4 X breadth; carpus with 2 long plumose setae and 2 setae on posterodistal corner; Pereopod 7 ( Fig. 2 ): coxa without setal fringe on ventral margin, basis length 2.0 X breadth; merus and carpus with long plumose setae on both margins; dactylus uncinate with 1 recurved spine.

Pleopods 1–3 ( Fig. 2 ): decreasing in size. Pleopod 1 outer ramus 7-articulate, basal article longeR and broadeR than distal articles; inner ramus longer than outer ramus (1.2 X), 6-articulate, basal article longest. Pleopod 2 biramous, outer ramus 6-articulate, basal article longest; inner ramus reduced, 1-articulate. Pleopod 3 outer ramus larger than inner ramus, 1-articulate; inner ramus reduced, 1- articulate. Uropod 1 ( Fig. 2 ): birramous; peduncle longer than outer ramus (1.3 X), with 3 medial plumose setae, with ventrodistal crown of cuticular setose rounded projection; inner ramus nearly ½ length of outer ramus, with 1 apical pinnate robusta seta; outer ramus outer margin serrate and with a row of short setae, with 1 apical pinnate robust seta. Uropod 2 ( Fig. 2 ): unirramous; peduncle length 4 X breadth; ramus small, asetose. Uropod 3 ( Fig. 2 ): unirramous, peduncle length 2.8 X breadth, ramus small, with 3 minute recurved spines. Telson ( Fig. 2 ): broader than long (3.2 X), moderately cleft (0.4 X), each lobe with with 12 to 13 recurved hooks arranged in 2 rows on dorsal surface, with 1 plumose seta on each apex.

Female paratype, 4.7 mm: differs from male mainly in gnathopod 2 and pereopod 5. Gnathopod 2 ( Fig. 2 ): subchelate; carpus small, as long as broad; propodus palm oblique with setae along inner margin. Pereopod 5 ( Fig. 2 ): coxa length 1.5 X breadth.

Tube ( Fig. 1 ): composed of very fine detritus material with masticated amphipod silk, which forms a tube in concentric rings.

Remarks: The number of the Cerapus species recorded in the West Atlantic until now is not confirmed. C. benthophilus Thomas & Heard, 1979; C. cudjoe Lowry & Thomas, 1991 and C. thomasi Ortiz & Lemaitre, 1997 were described in this region, but Lowry & Berents, 1989 suggested that the records of C. tubularis Say, 1817 ( Cowles, 1930; Wass, 1965, 1972; Feely & Wass, 1971; Watling & Maurer, 1972; Bousfield, 1973; Fox & Bynun, 1975) have to be verified. Wakabara et al., 1991 and Valério-Berardo et al. 2000 registered C. tubularis from Brazilian coast, but the specimens identified were lost and are not possible to confirm the identification. Cerapus jonsoni sp. nov. is easily distinguished from them by dacyli of pereopods 6 and 7 with 1 accessory spine. In addition, Cerapus jonsoni sp. nov. differs from C. cujdoe and C. thomasi by ventrodistal margin of peduncle of uropod 1 with a crown of cuticular setose projection instead of a hook, diagnostic character of these species. Also, Cerapus jonsoni sp. nov. differs from C. benthophilus in the number of articles of antennae flagellum (more than 6 in C. benthophilus ) and in the basis of male gnathopod 2 without proximal setal tuff. Cerapus jonsoni sp. nov. differs from C. tubularis in the number of articles in the flagellum of the antennae (2 and 3 in C. tubularis ); the transverse shape of the palm of male gnathopod 2; telson partly cleft and the presence of a ventrodistal crown of cuticular setose projection on uropod 1 peduncle.

Figures

FIGURE 1. Cerapus jonsoni sp. nov. Holotype, male, 4.0 mm, 24 º 10 ’ 17 ” S – 46 º 37 ’ 08 ” W, 14 m, col. N / Pq W. Besnard, VIII / 2005, MZUSP 18445. Scale bars = 0.1 mm, unless indicated otherwise.

FIGURE 2. Cerapus jonsoni sp. nov. Holotype, male, 4.0 mm, 24 º 10 ’ 17 ” S – 46 º 37 ’ 08 ” W, 14 m, col. N / Pq W. Besnard, VIII / 2005, MZUSP 18445; Paratype female, 4.7 mm, 24 ° 03 ’ 96 ” S – 46 ° 22 ’ 38 ” W, 17.3 m, col. N / Pq W. Besnard. VIII / 2005, MZUSP 18446. Scale bars = 0.1 mm.