Cymadusa pemptos, 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 : 28-31

Cymadusa pemptos sp. nov.

( Figs 21–23 )

Type material. Holotype: male, 8 mm, AM P61924, Fifth Creek, Spencer Gulf, Port Pirie, South Australia, Australia, 33°12’S 137°55’E, August 1979, intertidal, 0.6–0.8 m, on Zostera sp., T. J. Ward. Paratypes: AM P61925 (female, 8 mm), AM P61926 (females and

Males, 3 specimens), type locality.

Diagnosis. Antenna 1 unknown. Maxilla 1 inner plate with 4 slender setae. Gnathopod 1 with sparsely setose margins; merus produced to form a small, acute distoventral lobe; carpus subequal to propodus; palm acute, entire, without midmedial tooth, without posterodistal tooth defining palm, with 1 defining robust seta. Gnathopod 2 with sparsely setose on margins; merus produced to form a long, subacute distoventral lobe; carpus shorter than propodus; palm acute, entire, with subacute midmedial tooth, with small subacute posterodistal tooth defining palm, with 1 defining robust seta; dactylus subequal in length to palm, tapering evenly, acute point. Epimeron 3 posteroventral corner narrowly rounded, with a small acute tooth. Uropod 3 peduncle with 5 distal robust setae; outer ramus without patch of small conical lateral denticles, with lateral setal fringe. Telson distally rounded, apical cusps small, with slender lateral and apical setae.

Description. Male (based on holotype, male, 8 mm, AM P61924). Head as long as deep. Mandible molar with nine robust setae in the accessory setal row; palp stout, long, setose along posterior margin, article 1 shorter than article 2 (0.47 x), article 2 subequal to article 3 (0.93 x), article 3 longer than article 1 (2.29 x).

Lower lip with lateral lobe longer than medial lobe; mandibular lobe with curved margins, rounded apically. Maxilla 1 palp well developed, with apical robust setae. Maxilla 2 inner plate narrow, outer plate broader. Maxilliped outer plate with developed setation (robust setae large).

Pereon. Gnathopod 1 coxa subequal to gnathopod 2 coxa, produced distoventrally, distoventral margin rounded, anterior margin straight, ventral margin with a row of small setules along ventral margin and with a long tuft of slender setae in posteroventral corner; basis subequal to coxa, with fringe of long, slender, plumose setae, posterodistal lobe small and rounded, with 2 or 3 slender setae; merus anterior margin with setae absent; carpus longer than merus, subtriangular, carpal lobe subacute, anterior margin with slender setae only; propodus narrow (length 1.54 x width), ovoid; dactylus subequal in length to palm, inner margin denticulate. Gnathopod 2 coxa ventral margin with row of small setules along ventral margin and a tuft of long slender setae in posteroventral corner; basis longer than coxa, with fringe of long, slender, plumose setae, posterodistal lobe large and rounded, with more than 3 slender setae; merus anterior margin without setae; carpus subequal to merus, subtriangular, anterior margin with 3 or 4 robust setae and slender setae; propodus broad (length 1.48 x width), subrectangular, not produced into an anterodistally setose lobe; dactylus inner margin denticulate. Pereopods 5–7 broken off.

Pleon. Uropod 1 peduncle with more than 5 robust setae and with a 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 3–5 marginal robust setae, slender setae absent. Uropod 3 peduncle longer than broad (1.45 x width), short in relation to rami length (1.95 x), marginal robust setae absent, and marginal slen- der setae present, with more than 5 distal slender setae; outer ramus shorter than inner ramus; inner ramus with 5 distal robust setaeand more than 5 distal slender setae.

Female (sexually dimorphic characters; based on paratype female, 8 mm, AM P61925). Gnathopod 1 coxa larger than gnathopod 2; basis shorter than coxa; merus produced to form a short, subacute distoventral lobe; propodus subrectangular; palm convex. Gnathopod 2 basis with sparse plumose or simple slender setae, posterodistal lobe small and rounded, with 2 or 3 slender setae; merus produced to form a small, subacute distoventral lobe; carpus longer than merus, anterior margin with 2 robust setae and slender setae; propodus ovoid; palm without a midmedial tooth.

Etymology. The species name is derived from the Greek for fifth, as the type locality for this species is Fifth Creek, Spencer Gulf, South Australia.

Remarks. Cymadusa pemptos sp. nov. is similar to two Indo-Pacific species, C. grossimana Ledoyer, 1984 from New Caledonia and C. lunata Myers, 1985 from Fiji. Common characters of these three species are a 1-articulate accessory flagellum on antenna 1 and a small acute tooth on the posteoventral corner of epimeron 3. Cymadusa pemptos sp. nov. is distinguished from these two species in several features including sparse setae on the margins of gnathopod 2 (strongly setose in C. lunata ; moderately setose in C. grossimana ) and gnathopod 2 with an entire palm, defined by a small posterodistal tooth and a robust seta (both C. lunata and C. grossimana have a deeply excavate gnathopod 2 palm with a reasonably large posterodistal tooth and no defining robust seta).

Habitat. Cymadusa pemptos occurs intertidally (0.6–0.8 m) on Zostera sp.

Distribution. Spencer Gulf, South Australia, Australia.

Figures

FIGURE 21. Cymadusa pemptos sp. nov., holotype, male, AM P 61924, 7 mm. Paratype, female, AM P 61925, 8 mm. Fifth Creek, Spencer Gulf, Port Pirie, South Australia, Australia.

FIGURE 22. Cymadusa pemptos sp. nov., holotype, male, AM P 61924, 7 mm. Fifth Creek, Spencer Gulf, Port Pirie, South Australia, Australia. Scales 0.2 mm. Male and female antennae are missing.

FIGURE 23. Cymadusa pemptos sp. nov., holotype, male, AM P 61924, 7 mm. Paratype, female, AM P 61925, 8 mm. Fifth Creek, Spencer Gulf, Port Pirie, South Australia, Australia. Scales 0.5 mm. Pereopods 5 – 7 are missing.