Cymadusa chuawe, Peart, Rachael A., 2007

Peart, Rachael A., 2007, A review of Australian Cymadusa (Crustacea: Amphipoda: Ampithoidae) with descriptions of eight new species, Zootaxa 1540, pp. 1-53 : 4-8

Cymadusa chuawe sp. nov.

( Figs. 1–3 )

Type material. Holotype: female, ovigerous, 14.0 mm, WAM C 38528, W side of Northwest Cape, Tantabiddi Beach, Western Australia, Australia, 21°53’S 113°58’E, 18 June 1997, 10 m, on Sargassum sp., University of Charleston Western Australian Expedition.

Paratypes: WAM C 38529 (male, 11.0 mm), AM P51270 (females and males, 10–12 mm), west side of Northwest Cape, Tantabiddi Beach, Western Australia, Australia, 21°53’S 113°58’E, 18 June 1997, 10 m, on Sargassum sp., University of Charleston Western Australian Expedition.

Diagnosis. Antenna 1 accessory flagellum with 2 articles. Maxilla 1 inner plate with 6 slender setae. Gnathopod 1 with sparsely setose margins; merus produced to form a small, subacute distoventral lobe; carpus subequal in length to propodus; palm acute, entire, without midmedial tooth, without posterodistal tooth defining palm, with a defining robust seta. Gnathopod 2 with sparsely setose margins; merus produced to form a small, rounded distoventral lobe; carpus shorter than propodus; palm transverse, entire, without midmedial tooth, with a small subacute posterodistal tooth defining the palm, with defining robust seta; dactylus subequal in length to palm, tapering evenly to an acute point. Epimeron 3 posteroventral corner narrowly rounded. Uropod 3 peduncle with 6 distal robust setae; outer ramus without patch of small lateral denticles, with lateral setal fringe. Telson distally truncate, apical cusps small, with oblique lateral and medial rows of slender setae.

Description. Male (based on paratype male, 11.0 mm, WAM C 38529). Head as long as deep. Antenna 1 longer than antenna 2; peduncular article 1 longer than article 2 (1.1x), article 2 longer than article 3 (4 x), article 3 shorter than article 1 (0.2 x); accessory flagellum with 2 articles. Antenna 2 slender, similar to antenna 1, sparsely setose on ventral margin; peduncle article 4 subequal in length to article 5; flagellum with 23–25 articles. Mandible molar with 8 robust setae in the accessory setal row; palp stout, long, setose along posterior margin, article 1 shorter than article 2 (0.7 x), article 2 shorter than article 3 (0.9 x), article 3 longer than article 1 (1.6 x). Lower lip with lateral lobe longer than medial lobe; mandibular lobe with straight margins, rounded apically. Maxilla 1 palp with 2 articles, with 9 apical robust setae, inner plate with 6 slender setae; Maxilla 2 inner plate narrow, outer plate broader. Maxilliped outer plate with large robust setae.

Pereon. Gnathopod 1 with sparsely setose margins; coxa larger than gnathopod 2 coxa, produced distoventrally, distoventral margin rounded, anterior margin convex or straight, ventral margin with a row of small setules along ventral margin and with long tuft of slender setae in posteroventral corner; basis subequal in length to coxa with slender setae, posterodistal lobe small and rounded without any setae present; merus anterior margin with setae absent; carpus longer than merus, subrectangular, carpal lobe truncated and slightly rounded, anterior margin with slender setae only; propodus narrow (length 1.5 x width), ovoid; dactylus subequal in length to palm, inner margin rugose. Gnathopod 2 coxa ventral margin with a row of small setules along ventral margin and with a tuft of long slender setae in the posteroventral corner; basis shorter than coxa, with a fringe of long slender setae, posterodistal lobe large and subacute with setae absent; merus anterior margin with sparse slender setae; carpus subequal in length to merus, subtriangular, anterior margin with slen- der setae only; propodus broad (length 1.1 x width), not produced into an anterodistally setose lobe; dactylus tapering evenly, acute, inner margin rugose. Pereopod 5 basis with marginal robust setae, with medial slender setae; merus subrectangular; propodus not expanded distally, with 3 distal simple, striated, robust setae; dactylus hooked. Peraeopod 6 basis posterior margin rounded proximally, straight distally, with marginal robust setae, with medial slender setae; merus subrectangular; propodus slightly expanded distally, with 3 distal simple, striated, robust setae; dactylus slightly curved. Peraeopod 7 basis with marginal robust setae, without medial slender setae; propodus defined distally by 3 simple, striated robust setae.

Pleon. Epimeron 3 posteroventral corner narrowly rounded. Uropod 1 peduncle with more than 5 marginal robust setae, with long setal fringe; inner ramus slightly longer than outer ramus, with 9 marginal robust setae, slender setae absent; outer ramus with 10 marginal robust setae, slender setae absent. Uropod 2 peduncle with 4 marginal robust setae, setal fringe absent; inner ramus slightly longer than outer ramus, with 11 marginal robust setae, slender setae absent; outer ramus with 10 marginal robust setae, slender setae absent. Uropod 3 peduncle longer than broad (1.1 x width), short in relation to rami length (1.6 x), marginal robust setae absent, marginal slender setae absent, with 3 distal slender setae; outer ramus longer than inner ramus, without patch of small conical denticles; inner ramus with 5 distal robust setae, with 6 distal slender setae. Telson distally truncate.

Female (sexually dimorphic characters; based on holotype, 14.0 mm, WAM C 38528). Head longer than deep. Antenna 1 subequal to antenna 2, peduncular article 1 subequal to article 2 (1 x), article 2 longer than article 3 (3.8 x), article 3 shorter than article 1 (0.3 x). Antenna 2 peduncle article 4 subequal to article 5; flagellum with 24–26 articles. Gnathopod 1 subequal in size to gnathopod 2; coxa subequal in size to gnathopod 2 coxa. Gnathopod 2 propodus palm acute, entire, without midmedial tooth, with small subacute posterodistal tooth defining palm; subequal in length to palm, dactylus tapering evenly, acute, inner margin rugose.

Etymology. The species name is an anagram of the initials of the collection trip (University of Charleston Western Australian Expedition).

Remarks. Cymadusa chuawe is morphologically similar to C. munnu Poore & Lowry, 1997 , from eastern Australia and C. tishana sp. nov. from Western Australia (see account of C. tishana for distinguishing characters). Cymadusa chuawe and C. munnu share a smooth epimeron 3 posteroventral corner (no tooth), a midmedial tooth on the palm of gnathopod 2 (quite small and rounded in C. chuawe ; and the uropod 3 peduncle lacks marginal robust setae. However, the main difference between the two species is in the shape of the gnathopod 2 propodus, having an acute angle in C. chuawe and with a transverse angle in C. munnu .

Habitat. Cymadusa chuawe collected from washes of rocks and algae (especially Sargassum sp.) in the intertidal zone.

Distribution. Northwest Cape, Tantabiddi Beach, Western Australia (Indian Ocean).

Figures

FIGURE 1. Cymadusa chuawe sp. nov., holotype, female, WAM C 38528, 14 mm. Paratype, male, WAM C 38529, 11 mm, west side of Northwest Cape, Tantabiddi Beach, Western Australia.

FIGURE 2. Cymadusa chuawe sp. nov., holotype, female, WAM C 38528, 14 mm. Paratype, male, WAM C 38529, 11 mm, west side of Northwest Cape, Tantabiddi Beach, Western Australia.

FIGURE 3. Cymadusa chuawe sp. nov., holotype, female, WAM C 38528, 14 mm. Paratype, male, WAM C 38529, 11 mm, west side of Northwest Cape, Tantabiddi Beach, Western Australia.