Koroga megalops Holmes 1908

Koroga megalops Holmes, 1908

(Figs 19–22)

Koroga megalops Holmes, 1908: 503, fig. 13.— Stephensen, 1923: 60, fig. 5.— Stephensen, 1925: 60, fig. 5.— Stephensen, 1933: 11.—K.H. Barnard, 1937: 145, fig. 3.— Thorsteinson, 1941: 56, pl. 2, figs 18–20.— Shoemaker, 1945: 186.— Gurjanova, 1951: 192, fig. 62.— Birstein & Vinogradov, 1955: 222.— Birstein & Vinogradov, 1958: 224.— Birstein & Vinogradov, 1960: 166, 187.— Gurjanova, 1962: 93, fig. 20.— Nagata, 1963: 1.—J.L. Barnard, 1964: 317, fig. 2.— Birstein & Vinogradov, 1964: 152 (list), 171.— Birstein & Vinogradov, 1970: 402, table 1, 417, table 3.— Percy & Ambler, 1974: 749, table 2.— Thurston, 1990: 270.— Barnard & Karaman, 1991: 494.— Lowry & Stoddart, 2003: 283.

Types. Holotype, female (ovigerous), 10 mm, USNM 38539.

Type-locality. Vicinity of Funter Bay, Lynn Canal, Alaska, 640 m depth.

Australian material examined. New South Wales. 1 female, AM P.69465, east of Sydney (33°44.5'S 152°24.4'E to 34°08.9'S 152°09.68'E), 0–1800 m over bottom depth 2994–3828 m, Isaacs-Kidd midwater trawl, 27–28 April 1989, J. R. Paxton, HMAS Cook [JP 89-5]; 1 male, AM P.69464, east of Broken Bay (33°30.0'S 152°09.0'E to 33°33.0'S 152°11.0'E), 922–1015, beam trawl, 12 February 1986, R. T. Springthorpe, FRV Kapala [K86-01-08]; 1 female, AM P.69461; 1 female, AM P.69462; 1 male, AM P.69463, east of Shoalhaven Heads (34°54.0'S 151°14.0'E to 34°50.0'S 151°15.0'E), 988–1015, beam trawl, 26 October 1983, FRV Kapala [K83-14- 04]; 5 specimens, NMV J67749, 52 km east-south-east of Nowra (34°56.10'S 151°14.69'E), 3 m Isaacs-Kidd midwater trawl, G.C.B. Poore et al., 21 October 1988, RV Franklin [SLOPE 51]; 4 specimens, NMV J15791, 63 km east-south-east of Nowra (34°57.06'S 151°20.39'E), 3 m Isaacs-Kidd midwater, G.C.B. Poore et al., 21 October 1988, RV Franklin [SLOPE 52]; 9 specimens, AM P.43370, north-east of Coffs Harbour, New South Wales, Australia (30°10.93’S 153°32.26’E), 1000 m, Globigerina ooze, baited trap, 8–9 September 1994, J.K. Lowry & K. Dempsey, MV Carrie Ann [NSW-1000]; 1 specimen, AM P.43433, off Wollongong (34°32.4’S 151°22.8’E), 1000 m, baited trap, 27–28 March 1994, J.K. Lowry & K. Dempsey, MV Robin E [NSW-955]; 1 specimen, AM P.43449, off Wollongong (34°32.4’S 151°22.8’E), 1000 m, baited trap, 28–29 March 1994, J.K. Lowry & K. Dempsey, MV Robin E [NSW-971]; 2 specimens, AM P.44379, off Wollongong, (34°33.42’S 151°21.35’E), 1000 m, Globigerina ooze, baited trap, 6–7 May 1993, P. Freewater & party, MV Robin E [NSW-789]; 25 specimens, AM P.48100; 2 specimens, AM P.48126, north-east of Coffs Harbour, (30°10.93’S 153°32.26’E), 963 m, baited trap, 11–12 August 1993, P.B. Berents, R. T. Springthorpe & W. Vader, MV Cheryl Lee [NSW-862 & NSW-863]; 19 specimens, AM P.49811; 1 specimen, AM P.56084, north-east of Coffs Harbour (30°10.88’S 153°32.22’E), 1000 m, baited trap, 12–13 August 1993, P.B. Berents, R. T. Springthorpe & W. Vader, MV Cheryl Lee [NSW-876 & NSW-877]; 20 specimens, AM P.50078, north-east of Coffs Harbour (30°10.93’S 153°32.26’E), 1000 m, baited trap, 9–10 September 1994, J.K. Lowry & K. Dempsey, MV Carrie Ann [NSW-1022]; 14 specimens, AM P.51129.

Queensland. 2 specimens, AM P.47886, due east of Mooloolaba (26°36.23’S 153°50.23’E), 1006 m, baited trap, 2–3 August 1994, J.K. Lowry & K. Dempsey, MV Capricorn I [QLD-1140].

Tasmania. 22 specimens, AM P.96584, Hill D1, south-southeast of South East Cape (44°23.4'S 147°16.2'E), 1942 m, baited trap, 31 January 1997, CSIRO party on FRV Southern Surveyor, FRV Southern Surveyor [SS01/97/ 65]; 3 specimens, NMV J67750, 52 km east-north-east of Cape Tourville (42°02.39'S 148°58.26'E), 3 m Isaacs-Kidd midwater trawl over bottom depth 1695–2029 m, 28 October 1988, G.C.B. Poore et al., RV Franklin [SLOPE 76]; 2 specimens, NMV J67751, 61 km east-north-east of Cape Tourville (41°58.49'S 149°04.41'E), 3 m Isaacs-Kidd midwater trawl over bottom depth 1685–2524 m, 28 October 1988, G.C.B. Poore et al., RV Franklin [SLOPE 75]; 2 specimens, AM P.57983, east of Fortescue Bay (43°08.96’S 148°15.36’E), 1000 m, baited trap, 8–9 April 1994, J.K. Lowry & K. Dempsey, MV Martrudan [TAS-423]; many specimens, AM P.73692, 76.8km southsoutheast of South East Cape, Main Pedra Hill (44°15.6’S 147°07.8’E), 1312 m, baited trap, 21–24 January 1997, CSIRO party, FRV Southern Surveyor [SS01/97/08]; 50 specimens, AM P.73693, 82.8 km south-southeast of South East Cape, Hill U (44°19.2’S 147°07.2’E), 1083–1448 m, baited trap, 27–28 January 1997, CSIRO party, FRV Southern Surveyor [SS01/97/41]; 10 specimens, AM P.73694, Hill V, south-southeast of South East Cape (44°23.6’S 147°10.7’E), 1400 m, baited trap, 30 January 1997, CSIRO party, FRV Southern Surveyor, [SS01/97/ 61]; many specimens, AM P.73695, Hill D1, south-southeast of South East Cape (44°23.4’S 147°16.2’E), 1942 m, baited trap, 31 January 1997, CSIRO party, FRV Southern Surveyor [SS01/97/65]; 13 specimens, AM P.76864; 4 specimens, AM P.76865; 21 specimens, AM P.76866; 1 specimen, AM P.76867; 5 specimens, AM P.76868; 6 specimens, AM P.76869; 37 specimens, AM P.76870, north of Hill U Seamount, Huon Study Area (44°17.53’S 147°11.6’E), 1350 m, baited trap, 7 April 2007, S.J. Keable, FRV Southern Surveyor [SS02/2007/57].

Victoria. 3 specimens, NMV J67752, 78 km south of Point Hicks (38°30.13'S 149°15.52'E), 3 m Isaacs-Kidd midwater trawl over bottom depth 1960–1990 m, 25 October 1988, G.C.B. Poore et al., RV Franklin [SLOPE 65].

Extralimital material examined. United States. 7 specimens, AM P.35549, Alexander Archipelago, Revillagigedo Island, Bushy Point, Alaska (55°44.38’N 131°45.22'W), 0–503 m, plankton net, 30 June 1905, United States Fish Commission, USS Albatross [4747].

Description. Based on female, approx. 10.0 mm, AM P.69462. Head, lateral cephalic lobes broadly rounded; eyes reniform. Antenna 1 peduncular article 1 without anterodistal lobe; accessory flagellum 4-articulate, terminal article not offset; primary flagellum with weak 2-field callynophore; calceoli absent. Antenna 2 peduncular article 3 elongate, articles 3 to 5 not enlarged, brush setae present; flagellum short; calceoli absent. Labrum, epistome and upper lip separate; epistome produced equally with upper lip; upper lip not produced. Mandible incisors large, left and right symmetrical; molar setose, with a weakly spinose triturating area; palp attached slightly proximally, article 2 margins subparallel, article 3 blade-like. Maxilla 1 outer plate setal-tooth 7 present, cuspidate along most of inner; palp distal margin with apical robust setae, serrate at apicomedial corner. Maxilliped outer plate with 2 short, slender apical robust setae.

Gnathopod 1 strongly subchelate; coxa large, about as long as coxa 2, subrectangular with concave anterior margin; basis sparsely setose along anterior margin; ischium short (length less than 2 × breadth); carpus compressed, shorter than propodus; propodus large, margins subparallel, palm transverse, entire, slightly concave; dactylus simple. Gnathopod 2 propodus palm moderately obtuse. Pereopod 4 coxa with a moderately developed posteroventral lobe. Pereopod 5 coxa without distinct lateral ridge; basis longer than broad, posterior margin not serrate. Pereopod 7 basis posterodistally produced less than halfway along merus.

Pleonite 3 without mid-dorsal carina, not produced dorsodistally, posterodorsal margin not produced. Epimeron 3 posterior margin smooth, posteroventral corner narrowly rounded. Urosomite 1 not projecting over urosomite 2, with rounded boss. Uropod 2 inner ramus without constriction. Uropod 3 peduncle without dorsolateral flange; outer ramus article 2 short, with plumose setae on both rami. Telson notched, without dorsal robust setae, with 1 apical robust setae on each lobe.

Sexually dimorphic characters. Based on male, 8.7 mm, AM P.69463. Antenna 1 primary flagellum with strong 2-field callynophore; calceoli present. Antenna 2 flagellum short; calceoli present.

Depth range. Depths given in the literature range from 0–9120 m (Birstein & Vinogradov 1960), however, as these records represent specimens taken in trawls with no closing mechanism they are highly overestimated. Most records seem to come from bathyal and upper abyssal depths, i.e. approximately 200–3000 m.

Feeding strategy. A scavenger frequently taken in traps off the east coast of Australia. According to Thurston (1990) K. megalops attacks and feeds voraciously on dead and moribund fish in net catches.

Remarks. This is the first record of K. megalops in Australian waters though it has been taken from the Kermadec Trench and off the east coast of New Zealand (Birstein & Vinogradov 1960).

Distribution. North-east Pacific Ocean. Alaska (Holmes 1908; Thorsteinson 1941); Queen Charlotte Islands (J.L. Barnard 1964); Kurile-Kamchatka Region (Birstein & Vinogradov 1955, 1958, 1970); east of the Ryukyu Islands, Japan (Birstein & Vinogradov 1960). North-west Pacific Ocean. Japan Trench (Nagata 1963). North Atlantic Ocean. South of Iceland (Stephensen 1935); Bermuda (Shoemaker 1945). Indian Ocean. Near the Seychelles (K.H. Barnard 1937). Sea of Okhotsk. Off the Patience Peninsula, Sakhalin, Russia (Gurjanova 1962); Kuril Strait (Gurjanova 1962). Bering Sea. Komandorski Islands (J.L. Barnard 1964). South Pacific Ocean. Kermadec Trench (Birstein & Vinogradov 1960); off the east coast of New Zealand (Birstein & Vinogradov 1960); east coast of Australia (this study).