Protorchestia ceduna, Serejo & Lowry, 2008

Serejo, C. S. & Lowry, J. K., 2008, The Coastal Talitridae (Amphipoda: Talitroidea) of Southern and Western Australia, with Comments on Platorchestia platensis (Krøyer, 1845), Records of the Australian Museum 60 (2), pp. 161-206 : 196-199

Protorchestia ceduna n.sp.

Figs 27–29

Type material. HOLOTYPE: male 18.1 mm, AM P69066 (stubs J028–J032, J034–J035) . PARATYPES: 1 female ovigerous, 10.2 mm AM P69067 (2 slides, stub J033, SEM micrographs) ; 2 males and 6 ovigerous females, AM P69068 ; male, 10.9 mm, AM P69069 (slide) , small mangrove north of town, Ceduna, Eyre Peninsula , South Australia (32°8.87'S 133°40.24'E), small mangrove area with stony substrate, C. Serejo & J.K. Lowry, 19 Oct. 2003, SA 156 .

Additional material examined. Victoria: 1 male and 3 females, AM P69063, boat ramp with man-made rocky shore, Port Albert (38°40.23'S 146°41.86'E), among rocks, C. Serejo & J.K. Lowry, 10 Oct. 2003, VIC 124 .

South Australia: 7 males and 7 females, AM P69064 , North Beach, Wallaroo (33°54.51'S 137°37.77'E), broad flat beach with hard packed grey sand with a broad band of dead seagrass ( Zostera ) and large patches of beach rock, C. Serejo & J.K. Lowry, 16 Oct. 2003, SA 149 ; 1 male, AM P69065 , mangroves near boat ramp, Franklin Harbour, Cowell (33°41.26'S 136°55.65'E), thick mangrove (similar to Avicennia ) with rocks and logs on muddy substrate, C. Serejo & J.K. Lowry, 17 Oct. 2003, SA 150 ; 2 males and 1 female, Rio Rego?, sheltered beach, Baird Bay, Eyre Peninsula (33°6.43'S 134°16.63'E), stones on a very protected beach, C. Serejo & J.K. Lowry, 18 Oct. 2003, SA 154 .

Type material of Protorchestia lakei Richardson, 1996 . Holotype female 7.7 mm, AM P45574 . Paratype male, 9.2 mm, AM P 45575, northeast slope of Maatsuyker Island , Tasmania (on sea bird rookery between 10–80 m above sea level) .

Etymology. This species is named for the town of Ceduna, near the type locality.

Diagnosis. Maxillipedal palp article 4 distinct and small, 1⁄5 of article 3. Lower lip with distolateral setal tuft. Uropod 3 ramus with or without setae. Oostegites 2–4 moderately setose, with 26, 35 and 32 setae respectively. Telson about 1.5× longer than wide.

Description

Holotype male, 18.1 mm. Eye medium, 1⁄5–1/3 head length. Antenna 1 elongate, from midpoint to end of peduncle article 5 of antenna 2, flagellum with 8 articles. Antenna 2 shorter than head and first 3 pereonites, peduncular articles narrow and with sparse, small robust setae; flagellum with 16 articles. Lower lip with distolateral setal tuft. Mandible left lacinia mobilis 5-dentate. Maxilliped palp, article 2 without distomedial lobe, article 4 distinct and small, 1⁄5 of article 3.

Gnathopod 1 sexually dimorphic; subchelate; posterior margin of merus, carpus and propodus with rugose lobe; propodus subtriangular; palm transverse; dactylus shorter than palm, simplidactylate. Gnathopod 2 sexually dimorphic; subchelate; merus without medial lobe; carpus triangular, reduced, enclosed by merus and propodus; palm acute, smooth, posterodistal corner without protuberance; dactylus subequal in length to palm, attenuated distally. Coxae 2–4 as wide as deep. Pereopods 3–7 simplidactylate; dactylus without row or patch of dorsal short setae. Pereopod 4 subequal or slightly shorter than pereopod 3. Pereopod 4 dactylus similar to pereopod 3 dactylus. Pereopod 5 propodus distinctly longer than carpus. Pereopod 6 not sexually dimorphic; shorter than pereopod 7; coxa posterior lobe anterodistal corner rounded, with 1–2 marginal setae, posterior margin oblique to ventral margin, outer surface with ridge; carpus slender. Pereopod 7 basis posterodistal lobe absent; distal articles slender. Coxal gills simple or slightly lobate. Pereopods 3–5 gills subequal in size to gills 2 and 6.

Pleopods 1–3 well developed and biramous. Pleopods 1–3 peduncle without marginal setae. Epimeron 2 subequal in length to epimeron 3. Epimeron 3 posterior and ventral margins smooth, without setae, posteroventral corner with small subacute spine. Uropod 1 peduncle with 4–6 robust setae; distolateral robust seta present, large, about 1/3 to 1/2 length of outer ramus; inner ramus longer than outer ramus; inner ramus with 3 marginal robust setae; outer ramus without robust setae. Uropod 2 peduncle with 4 robust setae in two rows; inner ramus subequal in length to outer ramus; inner ramus with 3 marginal robust setae; outer ramus with marginal robust setae or without marginal robust setae; outer ramus with 1–2 marginal robust setae. Uropod 3 peduncle with 3 robust setae; ramus shorter than peduncle, triangular, narrowing distally, with 0–1 marginal seta, and 4 to 5 apical setae. Telson about 1.5× longer than wide; apically incised; with 2 apical robust setae per lobe; dorsal midline entire.

Female (sexually dimorphic characters), 10.2 mm. Antennae 1 with 6 articles. Antenna 2 with 13 articles. Gnathopod 1 propodus subrectangular; dactylus subequal in length to palm. Gnathopod 2 mitten-shaped; basis narrow, 3.4× longer than wide; posterior margin of merus, carpus and propodus with rugose lobe; palm obtuse; dactylus shorter than palm. Oostegites longer than wide; setae with curl-tips. Oostegites 2–4 moderately setose, with 26, 35 and 32 setae respectively. Uropod 3 peduncle with 0–1 robust setae.

Habitat. Estuarine zones and marshes.

Remarks. Protorchestia ceduna n.sp. is similar to P. lakei , species endemic to Tasmania northeast slope of Maatsuyker Island, in presenting a lower lip with distolateral setal tuft, general aspects of male and female gnathopods 1–2, and oostegites 2–4 with less than 36 marginal setae. Richardson (1996) described oostegite 2 bearing 24 setae and oostegites 3–4 bearing 20 and 24 setae respectively for P. lakei . The oostegites in the observed material have 26, 35 and 32 setae respectively, never surpassing 50 setae as seen in P. nitida and P. campbelliana . Also, a clear transversal ridge on coxa 6, 1–4 facial minute setae on the peduncle of pleopods 1–3, and posterior margin of propodus of pereopods 3–5 having 1–2 pairs of robust setae were observed. Richardson (1996) did not mention the coxa 6 ridge, described only pleopod peduncle 1 with setae, and noted that pereopod 5 lacked posterior setae but did not describe them for pereopods 3–4. Re-examination of the type material of P. lakei confirmed the presence of these character states.

The more intriguing variation occurs on uropods 2 outer ramus and ramus of uropod 3, which generally lack robust setae. This state is found in most specimens herein observed (males and females) varying in size from 7.2 to 11.7 mm. However, in some larger males (16.6 to 18.1 mm), and even a smaller female (9.8 mm), the uropod 2 outer ramus and/or uropod 3 ramus had 1 or rarely 2 robust setae. Furthermore, in a female and a large male (16.6 mm) the left uropod 3 had a robust seta and the right one had none, showing the variation in a single individual. Richardson’s 1996 description for P. lakei stated that the outer ramus of uropod 2 and ramus of uropod 3 lack marginal robust setae and variation in these structures in the type material was not observed.

Distribution. Victoria: Port Albert. South Australia: North Beach, Wallaroo; Franklin Harbour, Cowell; sheltered beach, Baird Bay, Eyre Peninsula; Ceduna, Eyre Peninsula.

Figures

Fig. 27. Protorchestia ceduna n.sp., paratype female, 10.2 mm, habitus and H, AM P69067, Ceduna, South Australia; holotype male, 18.1 mm, other parts, AM P69066, Port Albert, Victoria. Scales for habitus: 1 mm; H: 0.5 mm; remainder: 0.1 mm.

Fig. 28. Protorchestia ceduna n.sp., holotype male, 18.1 mm AM P69066, Port Albert, Victoria. Scales represent 0.2 mm.

Fig. 29. Protorchestia ceduna n.sp., holotype male, 18.1 mm, U1–2 and T, AM P69066, Port Albert, Victoria; female, 10.2 mm, G1–2, AM P69067, Ceduna, South Australia. Scales represent 0.2 mm.