Podocerus orontes, Hughes, 2013

Hughes, L. E., 2013, Podoceridae of Tropical Australia (Peracarida: Amphipoda), Records of the Australian Museum 65 (1), pp. 1-37 : 19-23

Podocerus orontes sp. nov.

Figs 14–17

Type material. Holotype male, 7.4 mm, dissected, 3 slides, MAGNT Cr 017399, Orontes Reef, Port Essington , Cobourg Peninsula (11°0.4'S 132°4.75'E), 10.15 m, 19 September 1985, coll. C. Hood, L. Vail and R. Williams; paratype female, dissected, 5.9 mm, 1 slide, MAGNT Cr 017400, Orontes Reef, Port Essington , Cobourg Peninsula (11°0.4'S 132°4.75'E), 10.15 m, 19 September 1985, coll. C. Hood, L. Vail and R. Williams; paratype male, SEM pin mount, AM P.85669, Orontes Reef, Port Essington , Cobourg Peninsula (11°0.4'S 132°4.75'E), 19 September 1985; paratypes 10 + specimens, MAGNT Cr 004975, Orontes Reef, Port Essington , Cobourg Peninsula (11°0.4'S 132°4.75'E), 10.15 m, 19 September 1985, coll. C. Hood, L. Vail and R. Williams; 1 male, 6.2 mm, SEM pin mount, AM P. 87034, Orontes Reef , Port Essington , Cobourg Peninsula (11°0.4'S 132°4.75'E), 19 September 1985; 10+ specimens, MAGNT Cr 011685, north of North West Vernon Island , Beagle Gulf (12°1.02'S 131°1.86'E), 38 m, shale and gravel, 11 October 1993, coll. K. E. Coombes.

Type locality. Orontes Reef, Port Essington, Cobourg Peninsula , Northern Territory (11°0.4'S 132°4.75'E) .

Etymology. Named from the type locality, applied as a noun in apposition.

Additional material examined. Northern Territory. 2 specimens (1 male, 1 female), MAGNT Cr 012180, west of North Peron Island, Timor Sea (13°10.26'S 129°55.62'E), 15 m, coarse sand and shale, 3 October 1993, coll: R. Williams ; 1 male specimens, MAGNT Cr 015891, northwest of Middle Point, Darwin Harbour (12.5'S 130.85'E), 3–4 m, sand, silt weed and sponges, 30 May 1989, coll: K. Coombes & R. Williams ; female, 7.8 mm, SEM pin mount carcass and dissection, 1 slide, AM P.87031, Area C East, Arafura Sea (9°22'59"S 134°09'47"E), 108 m, several large rocks, bioclastic gravel and sand, Smith-McIntyre grab, 11 May 2005, coll. G. D. F. Wilson (SS05/2005/019/GR033) ; 3 specimens, AM P.79144, Area C East, Arafura Sea (9°22'59"S 134°09'47"E), 108 m, several large rocks, bioclastic gravel and sand, Smith-McIntyre grab, 11 May 2005, coll. G. D. F. Wilson (SS05/2005/019/GR033); female, dissection, 1 slide, AM P.87623, Area C East, Arafura Sea (9°22'59"S 134°09'47"E), 108 m, several large rocks, bioclastic gravel and sand, Smith-McIntyre grab, 11 May 2005, coll. G. D. F. Wilson (SS05/2005/019/GR033) .

Western Australia. Female gravid, 9.2 mm, dissected, AM P.87629, Van Diemen Rise , eastern Joseph Bonaparte Gulf , Timor Sea (11°08'21"S 129°55'00"E), 31 m, Smith- McIntyre grab, 4 September 2009, Geoscience Australia, RV Solander ( SOL 21 GR29); male, 6.4 mm, dissected, AM P.87630, Van Diemen Rise, eastern Joseph Bonaparte Gulf, Timor Sea (11°37'21"S 129°50'07"E), 34 m, Smith-McIntyre grab, 17 September 2009, Geoscience Australia, RV Solander ( SOL41 GR77); male (damaged), AM P.87631, Van Diemen Rise, eastern Joseph Bonaparte Gulf, Timor Sea (12°24'14"S 129°58'10"E), 40 m, Smith-McIntyre grab, 19 September 2009, Geoscience Australia, RV Solander ( SOL 48 GR91); very small male, AM P.84680, Carnarvon Shelf (23°46'18"S 113°20'37"E), 44 m, Smith-McIntyre grab, 7 August 2008, coll. GeoscienceAustralia: Marine and Coastal Environment Group ( SOL 105 GR02) .

Diagnosis. Head rostrum weakly developed, almost absent; eyes not protruding from head. Gnathopod 1 coxa larger than coxa 2, as broad as long, anteroventral corner not produced, apically rounded; carpus rectolinear, 2.5 times as long as broad; propodus subtriangular. Gnathopod 2 merus posterior margin lined with dense brush of setae; propodus elongate subovoid, length 2.3 times width, palm with one proximal subtriangular and one small distal tooth, palm poorly defined. Pereonite 6 dorsal carina broad, produced posteriorly, subtriangular, apically subacute. Pereonite 7 dorsal carina produced posteriorly, subtriangular, apically rounded. Pleonites 1–2 dorsal carina broad, produced posteriorly, subtriangular, apically rounded. Epimera 1–3 posteroventral corner rounded. Uropod 1 with well-developed ventromedial spine, spine twice as long as broad. Uropod 2 biramous, ventromedial spine as long as broad. Telson dorsal lobe with 2 long and 2 short apical setae.

Female. Gnathopod 2 merus with 2 apical robust setae; propodus length 2.1 times width, propodus palm with large crenulate medial tooth, palm defined by corner with tooth and 1 robust seta; dactylus closing short of palm end.

Description. Based on holotype male, 7.4 mm. MAGNT Cr17399. Body cuticle with posterior dorsal carinae, laterally smooth. Head dorsally smooth; rostrum weakly developed, almost absent; eyes not protruding from head; lateral cephalic lobe subquadrate; anteroventral corner rounded. Antenna 1 (based on paratype female MAGNT Cr017400) subequal to body; peduncle article 2 subequal to article 3; primary flagellum 0.7 peduncle length; accessory flagellum 1-articulate, 5 times as long as broad. Antenna 2 distinctly longer than antenna 1, 1.5 times body length with dense concentration of long slender setae along posterior margin; article 4 subequal to article 5; flagellum about 0.25 times peduncle length. Antennae 2 flagellum posterior margin with line of short robust setae. Mandible accessory setal row with 2 setae. Maxilla 1 palp distal margin with 5 robust setae.

Gnathopod 1 coxa larger than coxa 2, as broad as long, anteroventral corner not produced, apically rounded; basis 3 times as long as broad, without anterodistal setae; carpus rectolinear, 2.5 times as long as broad; propodus subtriangular, anterior margin with clusters of long slender setae, palm margin smooth with 6 robust setae near corner of palm; dactylus posterior margin with serrate teeth, cuticle surface serrate. Gnathopod 2 basis 2.1 times as long as broad, anterodistal corner produced, rounded lobes with robust setae; merus posterior margin lined with dense brush of setae, with broad produced lobe, lobe 1.1 times as broad as long, apically rounded, without robust setae; carpus free, distinct from propodus; propodus elongate subovoid, length 2.3 times width, anterior margin with clusters of short robust setae, medial surface with dense plumose setae, palm straight, lined with dense bunch of plumose setae, with broad, well developed distal shelf, shelf margin smooth, propodus palm with one proximal subtriangular and one small distal tooth, palm poorly defined; dactylus eXtending the length of palm. Pereonite 6 dorsal carina broad, produced posteriorly, subtriangular, apically subacute. Pereonite 7 dorsal carina produced posteriorly, subtriangular, apically rounded.

Pleonites 1–2 dorsal carina broad, produced posteriorly, subtriangular, apically rounded. Epimera 1–3 posteroventral corner rounded. Uropod 1 biramus; peduncle 4 times as long as broad, with well-developed ventromedial spine, spine twice as long as broad; inner ramus 1.3 times peduncule length; outer ramus 0.75 times length of the inner ramus. Uropod 2 biramous, ventromedial spine as long as broad; outer ramus 0.5 times length of inner ramus. Uropod 3 uniramus; ramus without setae. Telson dorsal lobe with 2 long and 2 short apical setae, lower margin without lateral or apical setae.

Female (sexually dimorphic characters) based on paratype female, 5.9 mm. MAGNT Cr17400.

Gnathopod 2 basis twice as long as broad, anterodistal corner with long robust setae; merus posterior margin narrow, lobes as long as broad, apically subacute with 2 apical robust setae; propodus length 2.1 times width, palm acute, straight, ⅔ the length of the propodus with well-developed shelf, shelf margin strongly crenulate, propodus palm with large crenulate medial tooth, palm defined by corner with tooth and 1 robust seta; dactylus closing short of palm end.

Variation. In male and female adult specimens the pereonites 6–7 and pleonites 1–2 carina may be rounded, subacute or acute. This variation was not related to the gender or growth stage of specimens and was observed in material from several locations.

Remarks. The enlarged female gnathopod 2 in P. orontes sp. nov. is a more extreme example of sexual dimorphism than previous reported within the Podoceridae . The dorsal carina formula, form of gnathopod 1 and the consistent presence of the male and female morphotypes in samples from multiple locations over 100 km apart supports the idea that individuals are conspecific (as opposed to mismatched seXes). In both male and females the rounded and acute apical carina forms, not related to gender or growth stage, have been noted for P. ferreus sp nov.

The combination of four carina on the dorsum is known for P. fulanus Barnard, 1970 (males and females) and P. ferreus sp. nov. Podocerus orontes sp. nov. males can be separated from all other podocerid species by the combination of the male gnathopod 2 propodus palm with distal shelf and 1 large distal tooth, as well as the uropod 1 and 2 with ventromedial spine. The distal shelf and tooth of gnathopod 2 are similar in P. gloriosae Ledoyer, 1986 from Madagascar but this species has additional dorsal carina and no uropod ventromedial spines.

The female gnathopod 2 propodus palm with several broad multidentate teeth is currently unique compared to other male and female podocerids. A further distinguishing feature of P. orontes sp. nov. in both sexes is the gnathopod 1 elongate carpus (length 2.5 times breadth).

Distribution. Australia. Northern Territory: Port Essington, Timor Sea, Beagle Gulf, Darwin Harbour, North West Shelf (current study).

Figures

Figure 14.Podocerus ornontes sp. nov.male, 6.2 mm,AM P.87034, Cobourg Peninsula, Northern Territory.SEM photographs:(A) whole animal lateral view (scale 200 µm); (B) whole animal dorsal view (scale 200 µm); (C) head lateral view (scale 100 µm); (D) head dorsal view (scale 100 µm) and (E) gnathopod 2 propodus palm plumose setae (scale 20 µm).

Figure 15. Podocerus ornontes sp. nov. female, 7.8 mm, AM P.87031, Cobourg Peninsula, Northern Territory. SEM photographs: A) whole animal lateral view (scale 200 µm); (B) whole animal dorsal view whole animal lateral view with antennae (scale 1 mm); (C) whole animal dorsal view (scale 200 µm) (D) head lateral view (scale 100 µm); (E) head dorsal view (scale 100 µm); and (F) gnathopod 2 propodus palm plumose setae (scale 100 µm).

Figure 16. Podocerus ornontes sp. nov. holotype male, 7.4 mm, MAGNT Cr17399, Orontes Reef, Northern Territory, scale 0.1 mm.

Figure 17. Podocerus ornontes sp. nov. female, 7.8 mm, AM P.87031, Orontes Reef, Northern Territory, scale 0.1 mm.