Ampithoe rotunda, 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 : 83-86

Ampithoe rotunda sp. nov.

( Figs 66–69 )

Type material. Holotype: AM P61894, male, 2 mm, shallow lagoon, Heron Reef , Heron Island, Great Barrier Reef, QLD, 23°27’S 151°55’E, 13 Feb 1999, 1.4 m, on Dictyota sp. , R. Peart & S. Richards . Paratypes: AM P61895, 1 female , 4 mm, type locality; AM P61896, 3 specimens ; AM P61897, 3 specimens , type locality.

Diagnosis. Antenna 2 slender, similar to antenna 1, not densely setae on ventral margin. Lower lip with lateral lobe longer than medial lobe. Maxilla 1 inner plate with 1 slender seta. Gnathopod 1 carpal lobe rounded; carpus subequal in length to 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 2 or 3 slender setae; carpus shorter than propodus; palm acute, entire, without midmedial tooth, with a small subacute posterodistal tooth defining palm, without a defining robust seta; dactylus subequal in length to palm. Pereopod 3 basis narrow; merus narrow. Pereopods 5–7 weakly prehensile. Pereopod 5 merus subrectangular. Uropod 3 peduncle with 3 distal robust setae, outer ramus subequal in length to inner ramus, with 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, 2 mm, AM P61894. Head as long as deep. Antenna 1 longer than antenna 2; peduncular article 1 longer than article 2 (1.26 x), article 2 longer than article 3 (2.17 x), article 3 shorter than article 1 (0.36 x); primary flagellum with 18 articles. Antenna 2 peduncular article 4 longer than article 5; flagellum 15 articulate. Mandible molar with 4 or 5 robust setae in setal row; palp slender, long, apically setose, article 1 shorter than article 2 (0.47 x), article 2 longer than article 3 (1.71 x), article 3 longer than article 1 (1.23 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 reduced setation (robust setae small).

Pereon. Gnathopod 1 without densely setose margins; coxa subequal to gnathopod 2 coxa, produced distoventrally, distoventral margin acute, anterior margin concave, ventral margin with a row of small setules; basis subequal to coxa, with sparse (sometimes plumose) slender setae, posterodistal lobe small and rounded, 1 slender seta; merus produced to form a small, rounded distoventral lobe, anterior margin with setae absent; carpus longer than merus, subtriangular, anterior margin with slender setae only; propodus narrow (length 1.52 x width), ovoid; palm with 1 defining robust seta; dactylus inner margin denticulate. Gnathopod 2 coxa ventral margin with a row of small setules; basis subequal to coxa, with sparse slender setae; merus produced to form a short, subacute distoventral lobe, anterior margin with setae absent; carpus longer than merus, subtriangular, anterior margin with slender setae only; propodus broad (length 1.06 x width), nearly rounded, not produced into an anterodistally setose lobe; dactylus tapering evenly, acute, inner margin denticulate. Pereopod 5 basis with marginal robust setae, without medial slender setae; distal articles slender; propodus slightly expanded distally, subrectangular, with 4 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 a long setal fringe, with small rounded distoventral spur; rami subequal in length; inner ramus with 1 or 2 marginal robust setae, slender setae absent; outer ramus with 3–5 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 3–5 marginal robust setae, slender setae absent; outer ramus with 3–5 marginal robust setae, slen- der setae absent. Uropod 3 peduncle longer than broad (1.76 x width), long with respect to the rami length (2.3 x), marginal robust setae absent, marginal slender setae present, with 3–5 distal slender setae; inner ramus with 1 or 2distal slender setae. Telson with oblique medial rows of slender setae.

Female. (sexually dimorphic characters). Based on paratype, female, 4 mm, AM P61895. Antenna 1 primary flagellum with 1–20 articles. Antenna 2 flagellum with 12 articles. Gnathopod 1 subequal in size to gnathopod 2; palm entire. Gnathopod 2 basis shorter than coxa, posterodistal lobe small and round, with 1 slender seta; merus produced to form a small, rounded distoventral lobe; propodus ovoid; palm with a subacute mid-

medial tooth, defined by 1 robust seta. Uropod 1 peduncular distoventral spur absent.

Etymology. This species name is derived from the roundness of the gnathopod 2 propodus.

Remarks. Ampithoe rotunda sp. nov. is most similar to A. meganae sp. nov., with differences discussed under the account of the latter.

Habitat. Brown algae, mainly Dictyota spp.

Distribution. Heron Island, Queensland, Australia.

Figures

FIGURE 66. Ampithoe rotunda sp. nov., holotype, male, AM P61894, 2 mm. Paratype, female, AM P61895, 4 mm. Heron Island, Queensland, Australia.

FIGURE 67. Ampithoe rotunda sp. nov., holotype, male, AM P61894, 2 mm. Paratype, female, AM P61895, 4 mm. Heron Island, Queensland, Australia. Scales represent 0.2 mm.

FIGURE 68. Ampithoe rotunda sp. nov., holotype, male, AM P61894, 2 mm. Paratype, female, AM P61895, 4 mm. Heron Island, Queensland, Australia. Scales represent 0.2 mm.

FIGURE 69. Ampithoe rotunda sp. nov., holotype, male, AM P61894, 2 mm. Heron Island, Queensland, Australia. Scales represent 0.2 mm. Pereopod 6 is missing.