(Figs 1, 2)
Synopia ultramarina Dana, 1853: 995, pl. 68 fig. 6a–h. — Bovallius, 1886: 613, pl. 1, figs 1–21. — Stebbing, 1906: 271. — Spandl, 1924: 47, fig. 17 (part). — Schellenberg, 1926: 341. —K.H. Barnard, 1930: 367. — Shoemaker, 1933: 11. — Pirlot, 1936: 301. — Shoemaker, 1945: 195, fig. 8. — Nagata, 1965: 171. —J.L. Barnard, 1972: 51. — Ortiz, 1978: 9. — Ledoyer, 1986: 990, fig. 391. — Hirayama, 1988: 55, figs 279–282. — Barnard & Thomas, 1989: 363, figs 1–4 part. — Barnard & Karaman, 1991: 716. — Lowry & Stoddart, 2003: 124 (catalogue).
Synopia scheeleana. — Ledoyer, 1979: 137, fig. 88(II).
Type locality. Tropical Western Atlantic.
Material examined. 1 unsexed, AM P27058 (AJB H1 /29/11); male, 1 ‘A’ male specimen, 6.3 mm, 3 slides, AM P77868 (JML-7-10-1); 1 ‘B’ female, 4.0 mm, 3 slides, AM P77869 (JML-7-10-1); 10+ unsexed, AM P77870 (JML-7-10-1); 10+ unsexed, AM P77873 (JML 7-10 - 2); 14 unsexed, AM P77878 (JML 7-10 - 3); 6 unsexed, AM P70329 (JML 16-10 - 7); 4 unsexed, AM P77879 (JML 16-10 - 8); 2 unsexed, AM P77876 (JML 16-10 - 9); 4 unsexed, AM P77877 (JML 17-10 - 2); 4 unsexed, AM P77875 (JML 20-10 - 1); 5 unsexed, AM P77874 (JML 20-10 - 2); 82 unsexed, AM P36794 (JML 24-7 - 4); 1 unsexed, AM P77872 (QLD 1981); 183 unsexed, AM P77871 (QLD 2014).
Description. Based on male, 6.3 mm, AM P77868.
Head. Head protuberant. Rostrum short, apically acute; lateral cephalic lobe absent; eyes greater than half length of head; accessory eyes with 3 ommatidia. Antenna 1 peduncular article 1 without tooth; peduncular article 2 not elongate; flagellum 17–articulate. Antenna 2 flagellum 16–articulate. Mandible palp article 2 with 2 plumose setae; article 3 with 2 plumose apical setae; molar greatly enlarged, columnar, triturative, accessory setal row with 5 serrate setae. Maxilla 1 inner plate with 4 slender setae. Maxilliped foliaceaous.
Pereon. Pereonites 6–7 without lateral ridge. Pereonite 7 without carination. Gnathopod 1 weakly subchelate; coxa anterior margin not produced, coxa not tapering distally; basis about as long as carpus; propodus palm acute, without robust setae defining posterodistal corner of palm. Gnathopod 2 simple; coxa not distally tapering; basis about as long as carpus; dactylus vestigial, terminal setae short, subequal to length of dactylus. Pereopod 3 coxa anterodistal lobe absent, posterodistal lobe truncate, greater than half depth of coxa, margin smooth; basis width subequal to breadth of ischium. Pereopod 4 coxa smaller than coxa 3, subtriangular, posterior margin with well-developed lobe. Pereopods 5–6 basis subovoid, expanded, posterodistal lobe well developed, rounded, posterodistal lobe not extending past ischium. Pereopods 5–7 basis anterodistal corner weakly produced, rounded, posterior margin smooth. Pereopod 7 basis subrectangular, posterodistal lobe well developed, subacute, extending below ischium.
Pleon. Pleonites 1–3 without lateral ridges; without carination; posterodorsal margins smooth. Epimeron 1–3 posterior margin smooth, posterodistal corner rounded. Uropod 3 length greatly exceeding length of uropods 1–2; peduncle long (at least 2 x breadth). Telson moderately cleft (30-65%), much longer than uropod 3 peduncle, setae lining lateral margin, with 1 pair of slender and 1 pair of robust setae.
Habitat. Coral rubble, 12–18 m depth, nektonic at night.
Remarks. The presence of an accessory eye in Synopia ultramarina aligns it with S. caraibica Bovallius, 1886 and S. scheeleana Bovallius, 1886. In S. ultramarina the telson is moderately to deeply cleft which separates it from S. caraibica which has a weakly cleft telson (<30% of length). In S. ultramarina the pereopod 4 coxa is subtriangular whereas in S. scheeleana the coxa is subrectangular. Synopia ultramarina figured here has coxa 1 broader and pereopod 4 carpus less expanded in comparison to material figured by Hirayama (1988) and Barnard & Thomas (1989). Material figured by Ledoyer (1986) appears to have more rounded margins on coxae 1, 3 and 4. These slight variations are considered to be intraspecific variation within this widely distributed species.
Synopia ultramarina is exceptionally similar to Telsosynopia trifidilla Hughes & Lowry, 2006. These species co-occur at Lizard Island and One Tree Island and have been recorded from the same sample. Synopia ultramarina and Telsosynopia trifidilla are differentiated by the entire and cleft telson, respectively, however all other morphological variation between these species is slight. Material representing both sexes and a range of body sizes have been observed for both species and this dismisses the possibility of these taxa are a single species where the telsonic clefting is a growth stage.
Distribution. Australia. Queensland: Lizard Island (current study); Lowe Isles (K.H. Barnard 1930); Heron Island and One Tree Island (current study). Brazil (Dana 1853). Indian Ocean. (Dana 1853). Indonesia. Borneo (Pirlot 1936). Japan. Seto Inland Sea (Nagata 1965); Tomioka Bay (Hirayama 1988). Madagascar. (Ledoyer 1986). Red Sea (Spandl 1924). West Atlantic. (Dana 1853; Stebbing 1906); Bermuda (Shoemaker 1945); Caribbean (Shoemaker 1933; Ortiz 1978; Barnard & Thomas 1989).