Pseudopleonexes justi, Peart, Rachael A., 2006

Peart, Rachael A., 2006, A revision of Pseudopleonexes Conlan, 1982 (Crustacea: Amphipoda: Ampithoidae) with description of three new species from Australia, Zootaxa 1344, pp. 1-22 : 9-15

Pseudopleonexes justi sp. nov.

( Figs. 5–8 )

Type material. Holotype: male, 6 mm, AM P62566, Point Lewis, Blanket Bay, Cape Otway, Victoria, Australia, 38°50’S 143°35’E, 26 April 1988, intertidal, on Caulocystis uvifera and Hormosira washings, P. B. Berents & R. T. Springthorpe. Paratype: female, 8 mm, AM P62567, type locality.

Diagnosis. Antenna 1 shorter than antenna 2. Antenna 2 slender, peduncle similar width to antenna 1 peduncle, not densely setose on ventral margin. Maxilla 1 palp with 2 articles. Gnathopod 1 carpus subequal in length to propodus, carpal lobe straight; propodus narrow; palm transverse, entire, without midmedial tooth, with posterodistal tooth defining palm, without defining robust seta; dactylus overreaching palm. Gnathopod 2 with long setae on margins, not plumose; basis posterodistal lobe large and rounded, with two to three slender setae; carpus longer than merus, shorter than propodus; propodus broad, ovoid, produced into an anterodistally setose lobe; palm acute, entire, without midmedial tooth, with small subacute posterodistal tooth defining palm, with one defining robust seta; dactylus subequal in length to palm. Pereopod 5 merus ovoid; distal articles broad. Pereopod 6 distal articles slender. Pereopod 7 distal articles slender. Uropod 3 peduncle with one distal robust seta.

Description. Based on holotype male, 6 mm, AM P62566. Head longer than deep. Epistome and upper lip angle directed posteriorly, at more than 45 degrees. Antenna 2 peduncular article 4 shorter than article 5; flagellum with 13 articles. Mandible molar well developed, triturating; with five robust setae in accessory setal row; palp with three articles, slender, short, apically setose, article 1 shorter than article 2 (0.81 x), article 2 shorter than article 3 (0.88 x), article 3 longer than article 1 (1.39 x). Upper lip distally setose, lateral margins each with a midlateral notch. Lower lip outer plate notched or entire, with medial and lateral lobes equal in size; mandibular lobe with curved margins, subacute apically. Maxilla 1 palp with 2 articles, with apical slender setae; inner plate with one slender seta. Maxilla 2 inner plate narrow, outer plate broader. Maxillliped outer plate with large robust setae.

Pereon. Coxae long. Gnathopod 1 smaller than gnathopod 2, without densely setose margins; coxa subequal to gnathopod 2 coxa, not produced distoventrally, distoventral margin rounded, ventral margin with a row of small setules and with a long tuft of slender setae in posteroventral corner; basis longer than coxa, with sparse, plumose or simple, slender setae, posterodistal lobe small and rounded, without setae; merus produced to form a small, rounded distoventral lobe, anterior margin without setae; carpus longer than merus, subtriangular, anterior margin without setae; propodus subrectangular; dactylus inner margin denticulate. Gnathopod 2 coxa ventral margin with a row of small setules; basis longer than coxa, with sparse slender setae; merus produced to form a short, subacute distoventral lobe, anterior margin without setae; carpus subtriangular, anterior margin with slender setae only; dactylus tapering evenly, acute, inner margin denticulate. Pereopod 3 basis expanded; merus anteriorly expanded. Pereopod 4 basis and merus similar to pereopod 3. Pereopods 5–7 weakly prehensile. Pereopod 5 basis without marginal robust setae, without medial slender setae; propodus slightly expanded distally, subrectangular, with three distal simple striated robust setae; dactylus slightly curved. Pereopod 6 basis posterior margin rounded proximally, straight distally, without marginal robust setae, without medial slender setae; merus subrectangular; propodus subrectangular, slightly expanded distally, with three distal simple striated robust setae; dactylus slightly curved. Pereopod 7 basis without marginal robust setae, without medial slender setae; propodus subrectangular, defined distally by one to two simple, striated robust setae.

Pleon. Epimeron 3 posteroventral corner broadly rounded. Uropod 1 short, reaching midlength of peduncle of uropod 2 (in situ); peduncle with three to five robust setae, with a short setal fringe, with distoventral spur absent; rami subequal in length; inner ramus with robust setae absent, with slender setae absent; outer ramus with three to five marginal robust setae, slender setae absent. Uropod 2 peduncle with a broad, rounded laterodistal projection, with more than five robust setae, setal fringe absent; inner ramus slightly shorter than outer ramus, marginal robust setae absent, slender setae absent; outer ramus with three to five marginal robust setae, slender setae absent. Uropod 3 peduncle longer than broad (1.49 x width). Long with respect to the rami length (2.77 x), marginal robust setae absent, marginal slender setae present, with more than five distal slender setae; rami broad; outer ramus subequal in length to inner ramus, with two large recurved distal robust setae; inner ramus with more than five distal slender setae. Telson subtriangular, with apical slender setae, denticles absent.

Female (sexually dimorphic characters). Based on paratype female, 8 mm, AM P62567. Antenna 1 longer than antenna 2; peduncular article 1 longer than article 2 (1.34 x), article 2 longer than article 3 (1.81 x), article 3 shorter than article 1 (0.41 x); primary flagellum with 17 articles; accessory flagellum absent. Antenna 2 flagellum with 12 articles. Gnathopod 1 subequal in size to gnathopod 2; basis subequal in length to coxa, posterodistal lobe absent; carpal lobe straight; palm defined by one robust seta. Gnathopod 2 without densely setose margins; basis shorter than coxa; propodus not produced anterodistally; palm transverse, without tooth defining palm; dactylus overreaching palm.

Etymology. This species is named after Dr Jean Just, who has contributed much to ampithoid systematics, especially to the genus Pseudopleonexes .

Remarks. Pseudopleonexes justi is different from the other species as follows: the gnathopod 1 coxa is subequal in size to gnathopod 2 coxa and the carpal lobe is straight; the gnathopod 2 merus is produced to form a subacute distoventral lobe and the propodus is produced anterodistally to form a setose lobe; pereopods 5–7 are weakly prehensile; the uropod 3 peduncle bears one distal robust seta; and the telson bears subapical setae.

Habitat. Pseudopleonexes justi sp. nov. occurs in the intertidal zone inhabiting several types of algae.

Distribution. Blanket Bay, Cape Otway, Victoria, Australia.

Figures

FIGURE 5. Pseudopleonexes justi sp. nov., holotype, male, AM P 62566, 6 mm. Paratype, female, AM P 62567, 8 mm, Point Lewis, Blanket Bay, Cape Otway, Victoria, Australia.

FIGURE 6. Pseudopleonexes justi sp. nov., holotype, male, AM P 62566, 6 mm. Paratype, female, AM P 62567, 8 mm, Point Lewis, Blanket Bay, Cape Otway, Victoria, Australia. Scales represent 0.5 mm for antennae 1 – 2 (A 1, A 2) and 0.2 mm for mouthparts. Male antenna 1 is missing.

FIGURE 7. Pseudopleonexes justi sp. nov., holotype, male, AM P 62566, 6 mm. Paratype, female, AM P 62567, 8 mm, Point Lewis, Blanket Bay, Cape Otway, Victoria, Australia. Scales represent 0.5 mm.

FIGURE 8. Pseudopleonexes justi sp. nov., holotype, male, AM P 62566, 6 mm. Paratype, female, AM P 62567, 8 mm, Point Lewis, Blanket Bay, Cape Otway, Victoria, Australia. Scales represent 0.5 mm.