Paracerapus polutovi (Gurjanova)

Lowry, J. K. & Berents, Penelope B., 1996, The Ericthonius group, a new perpective on an old problem (Crustacea: Amphipoda: Corophioidea), Records of the Australian Museum 48 (1), pp. 75-109 : 103-107

Paracerapus polutovi (Gurjanova)

Figs 19 - 21

Cerapus polutovi Gurjanova, 1951: 946 , fig. 658. Paracerapus polutovi . Budnikova, 1989: 54.

? Cerapus comparativus Kudrjashov, 1975: 364 , fig. 1.

? Paracerapus comparativus . Budnikova, 1989: 54.

Type data. PARATYPES, male, 6.2 mm, AM P41691, female, 6.1 mm, male, AM P41692, East Kamchatka, Bering Sea, 20-29 m, 13 July 1934, stn 539.

Material described. Based on paratype male, 6.2 mm; dimorphic characters based on paratype female, 6.1 mm.

Diagnosis. Antennae: short, slender. Mandible: palp article 2 article 2 short, broad, length 1.8 x breadth, article 3 broad, clavate. Maxilla 1: outer plate with 10 setal-teeth. Gnathopod 2: male propodus broad, slightly curved, length 2.4 x width. Peraeopod 7: dactylus with row of accessory spines. Pleopod 2: biramous. Pleopod 3: biramous.

Description. Head: rostrum very short, straight, apically rounded; lateral cephalic lobe well developed, ventral corner rounded, subocular margin deeply recessed, anteroventral corner subquadrate, ventral margin horizontal, posterior margin vertical. Antenna 1: short, 0.27 x body length, without scales; peduncular article 1 with very weak keel, length 0.7 x peduncular article 3; accessory flagellum absent; flagellum long, 5-articulate (female 5), aesthetascs absent, article 1 long, 2 x article 2. Antenna 2: subequal in length to antenna 1; peduncle without scales; flagellum 5-articulate (female 6), article 1 long, 2.2 x article 2. Epistome and upper lip: fused. Mandible: left incisor with 4 cusps, right incisor with 4 cusps; left and right lacinia mobilis each with 4 cusps; left accessory setal row with 4 pappose robust setae, with 2 intermediate plumose setae, right accessory setal row with 4 pappose robust setae, with 3 intermediate plumose setae; molar triturating, molar flake on left and right side, molar seta only on right side; palp article 2 short, broad, length 1.8 x breadth, 1 x article 3 with 1 proximal A2-seta, with 5 posterior submarginal A2-setae, with 3 proximal and 10 posterior submarginal B2-setae, without D2-setae; article 3 clavate, long, 2.2 x breadth, with 1 proximal A3-seta, with distal A3-setae, with 10 posterior submarginal B3-setae, with 13 D3-setae and 3 E3-setae. Maxilla 1: inner plate small, with 2 simple apical setae; outer plate with 10 setal-teeth; palp with 6 terminal robust setae, without subterminal setae, flag seta present on distolateral corner. Maxilla 2: outer plate broader than inner; inner plate with setae distally along medial margin. Maxilliped: inner plate subrectangular with 3 nodular robust setae, without subterminal robust setae on medial corner, oblique setal row with 8 plumose setae; outer plate with 2 apical plumose setae, and 8 apicomedial robust setae; palp article 2, length 2 x breadth, article 3, length 1.7 x breadth.

Peraeonitel: without lateral keel in male. Peraeonite 2: without sternal keel in male. Peraeonite 5: male, length 1.7 x breadth, female, length 0.8 x breadth. Gnathopod 1: subchelate; coxa not fused to peraeonite 1 in male or female, length 1.2 x depth, without anteroventral lobe; basis in male with sparse setae along anterior margin, in female with sparse setae along anterior margin, without robust setae along anterior margin; carpus length 0.76 x depth with setose posterior lobe, anterior margin without setae in male and female; propodus length 1.6 x depth, with 7 rows of anteromedial setae; palm acute, without setae, with barbed robust setae. Gnathopod 2: carpochelate in male, subchelate in female; coxa not fused to peraeonite 2 in male or female, length 1.7 x depth, without sharp anteroventral cusp; basis long, bottle-shaped, length 2.6 x breadth; carpus massive, very long, slender, length 1.5 x breadth, posterior margin without tooth; palm obtuse, broadly excavate, without anterodistal tooth, posterodistal tooth well defined, medium in size, length 1 x width, without robust setae; propodus broad, curved, length 2.4 x width, without tooth on posterior margin, with teeth along posterior margin; dactylus, length 10.4 x propodus.

Peraeopod 3: coxa not fused to peraeonite 3 in male or female, length 2.3 x depth, without anteroventral lobe; basis length 1.1 x breadth, without inflated anterodorsal corner, with setae along anterior margin, without denticles along anterior margin; ischium length 1.2 x breadth; merus without ridges; carpus with 4 simple setae along distal half of anterior margin, with 10 simple setae along posterior margin; propodus with a few setae along posterior margin. Peraeopod 4: coxa not fused to peraeonite 4 in male or female, length 2.4 x depth, without anteroventral lobe; basis length 1.2 x breadth, without setal group along anterior margin; ischium long, length 1.4 x breadth; carpus without setae along distal half of anterior margin, with 7 simple setae along posterior margin; propodus with 8 simple setae along posterior margin. Peraeopod 5: coxa, length 1.5 x depth, without patches of small setae; anterior lobe of merus not extending beyond anterior margin of carpus, posterior lobe with 4 simple setae; propodus with 4 setae along posterior margin, dactylus short, uncinate with two accessory spines. Peraeopod 6: coxa without setal fringe ventrally, without patch of small setae; basis without anterior setae, without small denticles along posterodistal margin; merus, length 2.5 x breadth, without small anterodistallobe; carpus without anterodistal lobe, without posterodistal lobe, posterodistal corner bearing small setal bunch; propodus, anterodistal corner bearing large setal bunch; dactylus short, uncinate with rows of accessory spines. Peraeopod 7: coxa with posterodorsal lobe, without patch of small setae; basis without denticles along anteroproximal margin, without small denticles along posterodistal margin; merus, length 3 x breadth, without small anterodistal lobe, posterodistal corner bearing small setal bunch; carpus without anterodistal lobe, without posterodistal lobe, anterodistal corner bearing large setal bunch; propodus posterodistal corner bearing small setal bunch, anterodistal corner bearing small robust seta; dactylus short, uncinate with rows of accessory spines.

Oostegites: from gnathopod 2 to peraeopod 5. Gills: from peraeopod 3 to peraeopod 6.

Pleopods 1 to 3: decreasing in size. Pleopod 1: peduncle without patch of small setae, with 2 small distomedial hooks; rami subequal in length; inner ramus without patch of small setae, ll-articulate; outer ramus, article 1 with straight medial margin, 15-articulate. Pleopod 2: peduncle without patch of small setae, with 2 small distomedial hooks; biramous, inner ramus without patch of small setae, rami subequal in length, inner ramus 8-articulate; outer ramus broad, 1a-articulate, without patch of small setae. Pleopod 3: peduncle without patch of small setae, with 2 small distomedial hooks; rami subequal in length, without patch of small setae. Uropod 1: biramous, peduncle with distoventral corona of cuticular teeth, length 1.3 x outer ramus, without distoventral spine; outer ramus with lateral row of denticles, with 6 lateral setae, with large apical robust seta; inner ramus length 0.53 x outer ramus, without setae, with apical robust seta. Uropod 2: uniramous, peduncle length 2.5 x breadth, 2.8 x ramus; ramus small, with denticles and large apical robust seta. Uropod 3: uniramous peduncle length 1.6 x breadth; ramus with 3 curved spines. Telson: length 0.5 x breadth, cleft to base, each lobe with 22 to 25 anteriorly directed spines in two rows.

Tube. Unknown.

Remarks. According to Kudrjashov (1975) Paracerapus polutovi and P. comparativus (Kudrjashov, 1975) are closely related. Kudrjashov (1975) believed that the shape of the propodus of gnathopod 1 clearly distinguished the two species, but our illustration of the propodus is different to that of Gurjanova (1951), and appears more similar to that of Kudrjashov for P. comparativus . In males the carpochelate palm of P. polutovi is not as recessed as that of P. comparativus , but this condition may be related to the age of the individuals. It is possible that these two species are synonymous. Paracerapus comparativus is known from Iturup in the Kuril Islands, an island chain extending south from the Kamchatka Peninsula. Paracerapus polutovi occurs in the Commander Islands to the east of the Kamchatka Peninsula. Paracerapus comparativus needs to be redescribed in detail before its true relationship to P. polutovi can be considered.

Distribution. East Kamchatka and Commander Island, Bering Sea, littoral to 29 m depth.

Figures

Fig. 19. Paracerapus polutovi Gurjanova, 1951, lateral view, male paratype, 6.2 mm, AM P41691; East Kamchatka, Bering Sea.

FiJe. 21. /tllrtlc,,.rCll'u.\· polutovi Gurjanova, 1951, lateral view, male paratype, 6.2 mm, AM P41691; female, 6.I 1I1IU. nuale. AM P41692; East Kamchatka, Bering Sea. Scales represent 0.2 mm.