Cymadusa tishana, 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 : 42-46

Cymadusa tishana sp. nov

( Figs. 33–36 )

Type material. Holotype: male, 7 mm, WAM C 38530, Tish Point, Rosemary Island, Dampier Archipelago, Western Australia, Australia, 20°29.671’S 116°35.894’E, 30 August 1999, 0.5 m, on Dictyopteris sp., R. Peart.

Paratypes: female, 7 mm, WAM C 38531, west side of Malus Island, Dampier Archipelago, Western Australia, Australia, 26°30.612’S 116°38.918’E, 27 August 1999, 2.6 m, on Dictyota sp., R, Peart. female and male, AM P62533, type locality. AM P62534, females and males, 3 specimens, Tish Point, Rosemary Island, Dampier Archipelago, Western Australia, 20°29.671’S 116°35.894’E, 30 August 1999, 0.5 m, on Sargassum sp., R. Peart.

Diagnosis. Antenna 1 accessory flagellum with 2 articles. Maxilla 1 inner plate with 2 slender setae. Gnathopod 1 with sparsely setose margins; merus produced to form a long, acute distoventral lobe; carpus longer than propodus; palm acute, convex, without midmedial tooth, with posterodistal tooth defining palm, with 1 defining robust seta. Gnathopod 2 with long simple, slender setae on margins; merus produced to form a short, acute distoventral lobe; carpus subequal to propodus; palm acute, entire, with rounded midmedial tooth, with small subacute posterodistal tooth defining palm, with 1 defining robust seta; dactylus overreaching palm, tapering evenly, acute point. Epimeron 3 posteroventral corner broadly rounded. Uropod 3 peduncle with 4 distal robust setae; outer ramus without patch of small conical lateral denticles, without lateral setal fringe. Telson distally rounded, apical cusps small, with oblique lateral and medial rows of slender setae.

Description. Male (based on holotype, male 7 mm, WAM C 38530). Head as long as deep. Antenna 1 longer than antenna 2; peduncular article 1 subequal to article 2 (0.93 x), article 2 longer than article 3 (3.27 x), article 3 shorter than article 1 (0.33 x); primary flagellum with 35 articles. Antenna 2 slender, similar to antenna 1, not densely setose on ventral margin; peduncular article 4 longer than article 5; flagellum 25 articulate. Mandible molar with 6 robust setae in accessory setal row; palp stout, long, setose along posterior margin, article 1 shorter than article 2 (0.42 x), article 2 subequal to article 3 (1.05 x), article 3 longer than article 1 (2.28 x). Lower lip outer plate 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 larger than gnathopod 2 coxa, produced distoventrally, distoventral margin rounded, anterior margin straight, ventral margin with a row of small setules along ventral margin and with long tuft of slender setae in posteroventral corner; basis subequal to coxa, with sparse (sometimes plumose) slender setae, posterodistal lobe reduced, 1 slender seta; merus anterior margin with setae absent; carpus longer than merus, subtriangular, carpal lobe rounded, anterior margin with slender setae only; propodus narrow (length 1.62 x width), ovoid; dactylus overreaching palm, inner margin denticulate. Gnathopod 2 coxa ventral margin with a row of small setules along ventral margin and a tuft of long slender setae in the posteroventral corner; basis subequal to coxa, with sparse slender setae, posterodistal lobe absent; merus anterior margin with setae absent; carpus longer than merus, subtriangular, anterior margin with slender setae only; propodus broad (length 1.28 x width), ovoid, produced into an anterodistally setose lobe; dactylus inner margin denticulate. Pereopod 5 basis with marginal robust setae, without medial slender setae; merus subrectangular; propodus not expanded distally, subrectangular, with 3 distal simple striated robust setae; dactylus slightly curved.

Pleon. Uropod 1 peduncle with more than 5 robust setae, with short 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 more than 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 much longer than broad (2.24 x width), long with respect to rami length (3.01 x), with 3–5 marginal robust setae, marginal slender setae absent, with 3–5 distal slender setae; outer ramus shorter than inner ramus; inner ramus with 3 distal robust setae, with 1 or 2 distal slender setae.

Female. (sexually dimorphic characters; based on paratype female, 7 mm, WAM C 3853). Antenna 1 primary flagellum with 24 articles. Antenna 2 peduncular article 4 subequal in length to article 5; flagellum with 18 articles. Gnathopod 1 coxa subequal in size to gnathopod 2 coxa; merus produced to form a short, subacute distoventral lobe; carpus subequal in length to propodus, carpal lobe truncated; palm with posterodistal tooth defining the palm; dactylus subequal in length to the palm. Gnathopod 2 without densely setose margins; basis posterodistal lobe reduced, with 1 slender seta; merus produced to form a small, subacute distoventral lobe; propodus not produced anterodistally; palm without a midmedial tooth, without tooth defining palm.

Etymology. This species name is derived from the type locality, Tish Point Rosemary Island, Dampier Archipelago.

Remarks. Cymadusa tishana is similar to C. chuawe sp. nov., also from the west coast of Australia. These two species are share a 2-articulate accessory flagellum on antenna 1; non-plumose setae on the margins of gnathopod 2, and the palm of gnathopod 2 defined by a posterodistal tooth. These two species also resemble C. panwa Peart, 2002 from the Andaman Sea, but differ by having a midmedial tooth on the palm of the gnathopod 2 propodus.

The differences between C. tishana sp. nov. and C. chuawe are as follows: Cymadusa tishana sp. nov. has antenna 1 longer rather than subequal to antenna 2 and peduncular article 1 subequal to rather than longer than article 2;the inner plate of the maxilla 1 bears only one or two setae (more than four in C. chuawe ); in C. tishana , gnathopod 1 is subequal to, rather than smaller than gnathopod 2, the basis is subequal in length to the coxa, rather than shorter, with only sparse setae on the margin rather than a long setal fringe, the merus is produced to form a long and acute rather than a short subacute lobe, the carpus is longer than rather than subequal to the propodus, the carpal lobe is rounded rather than truncated, the palm is convex with adefining tooth, rather than straight and without a definingtooth, and the dactylus is longer than rather than subequal to the palm. In Cymadusa tishana the basis of gnathopod 2 has only sparsely rather than densely setose without the small posterodistal lobe, the merus is produced to form an acute rather than roundedlobe, the carpus is subequal to rather than shorter than the propodus, the propodus is ovoid and produced to form an anterodistal setose lobe rather than subrectangular and without a lobe, the palm is acute rather than transverse, and the dactylus is longer than rather than subequal to the palm.

Habitat. Cymadusa tishana sp. nov. occurs at 0.5–2.6 m depth on the brown algae Dictyota sp., Sargassum oligocystum and Dictyopteris sp.

Distribution. Dampier Archipelago, Western Australia, Australia.

Figures

FIGURE 33. Cymadusa tishana sp. nov., holotype, male, WAM C 38530, 7 mm. Paratype, female, WAM C 38531, 7 mm. Tish Point, Rosemary Island, Dampier Archipelago, Western Australia, Australia.

FIGURE 34. Cymadusa tishana sp. nov., holotype, male, WAM C 38530, 7 mm. Paratype, female, WAM C 38531, 7 mm. Tish Point, Rosemary Island, Dampier Archipelago, Western Australia, Australia. Scales 0.5 mm for antennae 1 – 2 and 0.2 mm for mouthparts.

FIGURE 35. Cymadusa tishana sp. nov., holotype, male, WAM C 38531, 7 mm. Paratype, female, WAM C 38531, 7 mm. Tish Point, Rosemary Island, Dampier Archipelago, Western Australia, Australia. Scales 0.5 mm.

FIGURE 36. Cymadusa tishana sp. nov., holotype, male, WAM C 38530, 7 mm. Tish Point, Rosemary Island, Dampier Archipelago, Western Australia, Australia. Scales 0.5 mm for pereopods 3 – 5 and 0.2 mm for uropods 1 – 3 and telson. Pereopods 6 – 7 missing.