Ampithoe cookana, Peart, 2007

Peart, Rachael A., 2007, A review of the Australian species of Ampithoe Leach, 1814 (Crustacea: Amphipoda: Ampithoidae) with descriptions of seventeen new species, Zootaxa 1566 (1), pp. 1-95 : 13-18

Ampithoe cookana sp. nov.

( Figs. 7–10 )

Type material. Holotype: AM P61832, male, 6 mm, north ledge, Cook Island , NSW, 28°11.44’S 153°34.67’E, 8 Jun 1983, 12 m, on Chlorodesmis sp. , E. Ho & K. Attwood . Paratype: AM P61833, female, 8 mm, type locality .

Diagnosis. Antenna 2 slender, similar to antenna 1, with short, dense setae on ventral margin. Lower lip with lateral lobe longer than medial lobe. Maxilla 1 inner plate with 6 slender setae. Gnathopod 1 carpal lobe truncated; carpus shorter than propodus; palm convex, without midmedial tooth, without posterodistal tooth defining palm; dactylus subequal in length to palm. Gnathopod 2 without densely setose margins; basis posterodistal lobe large and rounded, with three slender setae; carpus shorter than propodus; palm acute, excavate, without midmedial tooth, with small subacute posterodistal tooth defining palm, without defining robust setae; dactylus subequal in length to palm. Pereopod 3 basis expanded; merus narrow. Pereopods 5–7 simple. Pereopod 5 merus subrectangular. Uropod 3 peduncle with 5 distal robust setae, outer ramus shorter than inner ramus, without patch of small conical lateral denticles, without lateral setal fringe; inner ramus with 3 distal robust setae. Telson distally truncate, apical cusps small.

Description. Based on holotype male, 6 mm, AM P61832. Head as long as deep. Mandible molar with 5 or 6 robust setae in the accessory setal row; palp stout, long, setose along posterior margin, article 1 shorter than article 2 (0.34 x), article 2 longer than article 3 (1.16 x), article 3 longer than article 1 (2.53 x). Lower lip mandibular lobe with curved margins, subacute apically. Maxilla 1 palp with apical robust setae. Maxilla 2 inner plate narrow, outer plate broader. Maxilliped outer plate with developed setation (robust setae large).

Pereon. Gnathopod 1 without densely setose margins; coxa larger than gnathopod 2 coxa, produced distoventrally, distoventral margin rounded, anterior margin straight, ventral margin with a row of small setules along ventral margin; basis shorter than coxa, with sparse (sometimes plumose) slender setae, posterodistal lobe small and rounded, 2 or 3 slender setae; merus produced to form a small, rounded distoventral lobe, anterior margin with setae absent; carpus longer than merus, subtriangular, anterior margin with more than 3 robust setae; propodus narrow (length 1.76 x width), subrectangular; palm with 1 defining robust seta; dactylus inner margin denticulate. Gnathopod 2 coxa ventral margin, with a row of small setules; basis shorter than coxa, with sparse slender setae; merus produced to form a short, rounded distoventral lobe, anterior margin with setae absent; carpus longer than merus, subtriangular, anterior margin with more than 4 robust setae; propodus broad (length 1.12 x width), ovoid, not produced into an anterodistally setose lobe; dactylus tapering evenly, acute, inner margin denticulate. Pereopod 5 basis with marginal robust setae, with medial slender setae; distal articles slender; propodus not expanded distally, subrectangular, with 4 distal simple striated robust setae; dactylus strongly curved. Pereopod 6 basis posterior margin rounded proximally, straight distally, without marginal robust setae, without medial slender setae; merus subrectangular; propodus not expanded distally, with 3 distal simple striated robust setae; dactylus strongly curved. Pereopod 7 basis with marginal robust setae, without medial slender setae; propodus defined distally by 3–5 simple robust setae.

Pleon. Epimeron 3 posteroventral corner broadly rounded. Uropod 1 peduncle with more than 5 robust setae, with long setal fringe; inner ramus slightly longer than outer ramus, with more than 5 marginal robust setae, slender setae absent; outer ramus with more than 5 marginal robust setae, slender setae absent. Uropod 2 peduncle with 3–5 robust setae, setal fringe absent; inner ramus slightly longer than outer ramus, with more than 5 marginal robust setae, slender setae absent; outer ramus with more than 5 marginal robust setae, slender setae absent. Uropod 3 peduncle longer than broad (1.49 x width), long with respect to rami length (2.24 x), marginal robust setae absent, marginal slender setae present, with 3–5 distal slender setae; inner ramus with more than 5 distal slender setae. Telson with apical and lateral slender setae.

Female (sexually dimorphic characters). Based on paratype, female, 8 mm, AM P61833. Antenna 1 longer than antenna 2; peduncular article 1 subequal in length to article 2 (0.98 x), article 2 longer than article 3 (3.05 x), article 3 shorter than article 1 (0.33 x); primary flagellum with 30 articles; accessory flagellum absent. Atenna 2 slender, similar to antenna 1, with short, dense setae on ventral margin; peduncular article 4 subequal in length to article 5; flagellum in complete with 6–10 articles .

Gnathopod 1 subequal in size to gnathopod 2; coxa subequal in size to gnathopod 2 coxa; basis subequal in length to coxa; merus produced to form a short, subacute distoventral lobe; carpus subequal in length to propodus, anterior margin with slender setae only; palm not defined by robust setae; dactylus overreaching the palm. Gnathopod 2 basis posterodistal lobe small and round, with 2 or 3 slender setae; merus produced to form a small, subacute distoventral lobe; carpus anterior margin with 1 robust seta and slender setae; palm entire, without tooth defining palm, defined by 1 robust seta.

Etymology. This species name is derived from the name of the type locality, Cook Island.

Remarks. Ampithoe cookana sp. nov. resembles A. katae sp. nov. and A. rachanoi Peart, 2002 from Thailand, in having simple pereopods 5–7, an entire gnathopod 1 palm, gnathopod 2 has sparsely setose margins and a palm without a midmedial tooth. Of these species, A. cookana most closely resembles A. katae , differing chiefly in the following features: three slender setae on the gnathopod 2 basal lobe ( A. katae has one robust seta on gnathopod 2 basal lobe), 3 or 4 instead of 1 robust setae on the anterior margins of gnathopods 1 and 2 carpus, and the gnathopod 2 propodus bears an anterodistally setose lobe (absent in A. katae )

Habitat. Ampithoe cookana occurs in turtle grass, Chlorodesmis sp. at a depth of 12 m.

Distribution. Cook Island, New South Wales, Australia.

Figures

FIGURE 7. Ampithoe cookana sp. nov., holotype, male, AM P61832, 6 mm. Paratype, female, AM P61833, 8 mm. Cook Island, New South Wales, Australia.

FIGURE 8. Ampithoe cookana sp. nov., holotype, male, AM P61832, 6 mm. Paratype, female, AM P61833, 8 mm. Cook Island, New South Wales, Australia. Scales represent 0.5 mm for antennae 1–2 and 0.2 mm for mouthparts. Male antennae missing.

FIGURE 9. Ampithoe cookana sp. nov., holotype, male, AM P61832, 6 mm. Paratype, female, AM P61833, 8 mm. Cook Island, New South Wales, Australia. Scales represent 0.5 mm.

FIGURE 10. Ampithoe cookana sp. nov., holotype, male, AM P61832, 6 mm. Cook Island, New South Wales, Australia. Scales represent 0.5 mm for pereopods 3, 5–7 and 0.2 mm for uropods 1–3 and telson. Pereopod 4 not illustrated, as it is identical to pereopod 3.