Podocerus rockingham, Hughes, 2013

Hughes, L. E., 2013, Podoceridae of Tropical Australia (Peracarida: Amphipoda), Records of the Australian Museum 65 (1), pp. 1-37 : 23-26

Podocerus rockingham sp. nov.

Figs 18–19

Type material. Holotype male, 3.8 mm, dissected, 3 slides, WAM C.51669, reef west of groyne, 2 km south of Cape Peron (32°16'S 115°41'E), 3 m, brown algae in deep channels in limestone reef, 26 December 1983, coll. R. Springthorpe (WA 310); paratype female, 3.2 mm, dissected, 1 slide (poor condition), AM P.87619, reef west of groyne, 2 km south of Cape Peron (32°16'S 115°41'E), 3 m, brown algae in deep channels in limestone reef, 26 December 1983, coll. R. Springthorpe (WA 310); paratype male, 3.6 mm, SEM pin mount, AM P.85666, reef west of groyne, 2 km south of Cape Peron (32°16'S 115°41'E), 3 m, brown algae in deep channels in limestone reef, 26 December 1983, coll. R. Springthorpe (WA 310); paratypes many specimens, AM P.79830, reef west of groyne, 2 km south of Cape Peron (32°16'S 115°41'E), 3 m, brown algae in deep channels in limestone reef, 26 December 1983, coll. R. Springthorpe (WA 310).

Type locality. Cape Peron , Western Australia (32°16'S 115°41'E) .

Etymology. Named after the town of Rockingham, a settlement near the type locality. Applied as a noun in apposition.

Additional material examined. Male, AM P.79489, rocks near shore, Canal Rocks, south of Yallingup (33°40'16"S 114°59'40"E), 0.5 m, on narrow-leafed brown alga Sargassum sp., 6 December 2000, coll. R. A. Peart (WA 745); male, AM P.79491, rocks near shore, Canal Rocks, south of Yallingup (33°40'16"S 114°59'40"E), 0.5 m, on broad-leafed brown alga Sargassum sp., 6 December 2000, coll. R. A. Peart (WA 741).

Diagnosis. Body cuticle with sparse slender setae. Gnathopod 1 as broad as long, anteroventral corner greatly produced ventrally, apically subacute. Gnathopod 2 carpus indistinct, fused with propodus; propodus subovate, with weakly developed distal shelf, shelf margin strongly crenulate, palm without teeth or sinus, defined by 3 robust setae; dactylus closing short of palm end. Pereonite 7 dorsal carina broad, produced posteriorly, subtriangular, apically rounded. Pleonites 1–2 dorsal carina broad, produced posteriorly, subtriangular, apically rounded; epimeron 1 posteroventral corner rounded. Urosomite 1 length 1.5 times as long as broad. Uropod 1 peduncle 2 with well-developed ventromedial spine, spine 3 times as long as broad.

Description. Based on holotype male, 3.8 mm. WAM C51669J. Body cuticle with posterior dorsal carinae, laterally smooth with sparse slender setae.

Head dorsally smooth; rostrum short, one tenth of head length; eyes greatly bulging; lateral cephalic lobe subacute; anteroventral corner subquadrate. Mouthparts. Mandible accessory setal row with 5 setae. Maxilla 1 palp distal margin with 2 robust setae.

Gnathopod 1 coxa larger than coxa 2, as broad as long, anteroventral corner greatly produced ventrally, apically subacute; basis 2.5 times as long as broad, without anterodistal setae; carpus rectolinear with truncate lobe, lobe twice as long as broad; propodus subrectangular, anterior margin with clusters of long slender setae, palm margin minutely crenulate, with 1 robust seta near corner of palm; dactylus posterior margin with serrate teeth, cuticle surface with raised serrations. Gnathopod 2 basis 1.5 times long as broad; anterodistal corner subquadrate without lobes with long slender setae; merus posterior margin with rows of slender setae and narrow produced lobe, lobe as long as broad, apically acute, without robust setae; carpus indistinct, fused with propodus; propodus subovate, length 1.8 times width, anterior margin with clusters of long robust setae, medial surface with dense plumose setae, palm acute, straight, ⅔ the length of the propodus with weakly developed distal shelf, shelf margin strongly crenulate, palm without teeth or sinus, defined by 3 robust setae; dactylus closing short of palm end. Pereonite 7 dorsal carina broad, produced posteriorly, subtriangular, apically rounded.

Pleonites 1–2 dorsal carina broad, produced posteriorly, subtriangular, apically rounded; epimeron 1 posteroventral corner rounded. Epimera 2–3 posteroventral corner subquadrate. Urosomite 1 length 1.5 times as long as broad. Uropod 1 biramus; peduncle 2.5 times as long as broad, with well-developed ventromedial spine, spine 3 times as long as broad; inner ramus 1.3 times peduncule length; outer ramus 3⁄4 the length of the inner ramus. Uropod 2 biramous; peduncle ventromedial spine absent; outer ramus 3⁄4 length of inner ramus. Uropod 3 uniramus; ramus with apical setae. Telson dorsal lobe with 2 apical setae, lower margin with pair of slender apical setae.

Remarks. The male gnathopod 2 propodus in P. rockingham sp. nov. and P. akanthius Hughes, 2012 , from SouthAustralia, have a weakly developed distal shelf and crenulate palmar margin without teeth, similar to P. karu J. L. Barnard, 1972 from New Zealand and P. manawatu J. L. Barnard, 1972 , recorded in New Zealand and southern Australia. Podocerus rockingham sp. nov. and P. akanthius have three dorsal carinae and uropod 2 without a ventromedial spine, separating them from the dorsally smooth P. karu and P. manawatu which have a ventromedial spine on uropod 2.

The relationship between P. rockingham sp. nov. and P. akanthius is very close with regard to the three dorsal carinae, the distinctive gnathopod 1 coxa greatly attenuated and projecting ventrally, and the gnathopod 1 propodus shape. Podocerus rockingham sp. nov. can be distinguished by the apically rounded dorsal carina, the more subovate gnathopod 2 propodus, medial surface with dense setae and palm crenulate along only part of the margin. The apically rounded carinae are consistent in P. rockingham sp. nov. from juveniles, as small as 2.0 mm, to adult specimens. In P. akanthius the dorsal carinae have acute apices and the gnathopod 2 is slightly longer, less setose and with the palm weakly crenulate along the entire margin.

Interestingly, the gnathopod 2 propodus palm as either partially crenulate or fully crenulate is a relationship noted between the New Zealand species P. karu and P. manawatu by Barnard 1970, respectively.

Distribution. Western Australia: Cape Peron, Yallingup.

Figures

Figure 18. Podocerus rockingham sp. nov. paratype male, 3.6 mm, AM P.85666, Cape Peron, Western Australia. SEM photographs: (A) whole animal lateral view (scale 200 µm); (B) whole animal dorsal view (scale 100 µm); (C) head dorsal view (scale 100 µm); (D) gnathopod 2 propodus palm plumose setae (scale 20 µm) and (E) head lateral view (scale 100 µm).

Figure 19. Podocerus rockingham sp. nov. holotype male, 3.8 mm, AM P.87618, Cape Peron, Western Australia (scale 0.1 mm).