Megalanceoloides remipes (K.H. Barnard, 1932 )

Zeidler, Wolfgang, 2022, Redescription of the rare, deep-sea hyperiidean amphipod Megalanceoloides remipes (K. H. Barnard, 1932) (Crustacea: Amphipoda: Hyperiidea), including the first description of males, Zootaxa 5094 (2), pp. 341-350 : 342-343

Megalanceoloides remipes (K.H. Barnard, 1932)

Lanceola remipes Barnard 1932: 255–257 , fig. 159.

Megalanceola remipes .— Vinogradov 1964: 114–117, figs 4–5.— Vinogradov et al. 1982 / 1996: 82 /95 (key), 82–83/97–98, fig. 26. (Considered a new species, M. gascae , by Williams & Bunkley-Williams (2019)).

Megalanceoloides remipes .—Zeidler 2009: 79, fig. 28.— Zeidler & De Broyer 2009: 71.— Gasca & Haddock 2016: passim, figs 1–4 (figs 1–2 “in vivo” colour photo) (= M. aequanime Gasca, 2017 ).— Zeidler 2019: 514.

Material examined. The unique holotype of M. remipes , a female measuring about 40 mm, from the south-west Atlantic [41°43’S 42°20’W], Discovery stn. 72, 2000–0 m, 1 June 1926 ( NHM 1936.11.2.2510) . Southwest Atlantic : male ( USNM 301871 ), Cruise 4, stn. 154, Drake Passage [54°43’S 64°28’W], 2105 m, 16 August 1962 ; female (figured here) ( USNM 1089977 ), Cruise 6, stn. 448, South Shetlands, east of King George Island [61°06’S 59°15’W], 2580 m, 14 January 1963 ; poor specimen ( USNM 1089983 ), Cruise 8, stn. 592, Scotia Sea, north-east of South Sandwich Island [55°15’S 25°37’W], 2562 m, 29 April 1963 ; male ( USNM 1090231 ), Cruise 9, stn. 670, north of South Georgia [50°28’S 35°02’W], 1565 m, 21 August 1963 . Southeast Pacific : all western Drake Passage; juvenile male ( USNM 1090233 ), Cruise 10, stn. 778 [59°35’S 82°30’W], 1251–1691 m, 19 October 1963 ; female ( USNM 1090236 ), Cruise 10, stn. 832 [62°36’S 74°40’W], 1775–2723 m, 4 November 1963 ; juvenile male ( USNM 1090237 ), Cruise 10, stn. 852 [56°39’S 74°59’W], 3111 m, 13 November 1963 ; male (figured here) ( USNM 1090239 ), Cruise 10, stn. 877 [55°23’S 78°16’W], 1940 m, 29 November 1963 .

Description of male ( Figs 1–2 )

Specimen (USNM 1090239) measuring 34 mm along a parabolic line drawn through the mid-section of the body from the front of the head to the tip of the telson. Body elongate, not massive; pereon and pleon highly sculptured with slight dorsal keel and lateral depressions (see Zeidler 2009, fig. 28; also colour photos by Gasca & Haddock 2019, fig. 1). Head with relatively short, rounded rostrum. Mouthparts not dissected but third article of mandibular palp 1.4 x as long as first two combined, with few, short setae on first two articles. First antennae about 2 x as long as head, with large callynophore; terminal articles worn, not discernible, presumably three in number as described by Vinogradov (1964) and Gasca & Haddock (2016). Second antennae relatively long, about 3.5 x length of A1, as long as head and first four pereonites combined; terminal peduncular article with small, pointed lobe, partly overlapping following article medially; first flagellar article the longest, about 1.7 x length of following article; terminal articles worn, not discernible, presumably four in number as described by Gasca & Haddock (2016) for M. aequanime . G1 basis slightly shorter than remaining articles combined, slightly broader proximally, with fringe of short setae on anterior margin; merus very short, conical-shaped, with fringe of short setae on distal margin; carpus length about 0.6 x basis, relatively broad, progressively broader distally, with distinct postero-distal corner protruding posteriorly beyond posterior margin of propodus; propodus much narrower and shorter than carpus, tapering gradually to insertion of partly retractile dactylus, length about 0.7 x carpus. G2 more slender and slightly longer than G1; basis slightly shorter than remaining articles combined, sub-rectangular in shape; merus like G1; carpus linear, length about 0.5 x basis, without prominent postero-distal corner; propodus slightly narrower and sub-equal in length to carpus, otherwise like G1. P3–4 very similar in length and morphology; basis with evenly convex posterior margin and straight anterior margin, with few setae proximally, length about 1/3 of remaining articles combined; ischium with rounded antero-distal lobes for articulation with merus; merus, carpus and propodus flattened and relatively broad; merus length about 0.5 x basis, almost triangular-shaped, very broad distally, with sharp corners, maximum width about 0.7 x length; carpus length about 1.7 x merus, oval-shaped, broader than merus, postero-distal corner with large, rounded hollow for articulation with propodus; propodus slightly shorter than carpus, conical, tapering sharply to rounded point, with few short setae distally; dactylus very small, fully retractile. P5 slightly shorter than P4, with even broader, flattened articles; basis with marginally concave margins and large, rounded postero-distal lobe overlapping ischium, maximum length almost 0.5 x remaining articles combined, width distally about 0.5 x maximum length; ischium with elongate, rounded postero-distal lobe; merus like in P4 but shorter and broader, maximum width about 1.2 x length; carpus oval-shaped, with large rounded antero-distal lobe overlapping more than 0.5 of propodus, antero-distal corner with large, rounded hollow for articulation with propodus, maximum length almost 2 x merus; propodus conical, very broad proximally, tapering to rounded point, distal margin fringed with fine setae, length almost 0.7 x carpus, maximum width about 0.5 length; dactylus very small, fully retractile. P6 length about 1.2 x P5, with relatively slender articles; basis marginally longer than 0.5 remaining articles combined, with rounded postero-distal lobe, partly overlapping ischium; ischium also with rounded postero-distal lobe; merus length about 0.6 x basis, marginally broader distally, with slight postero-distal corner; carpus sub-equal in length to merus, with slightly convex posterior margin; propodus slightly shorter than carpus, tapering gradually to rounded point, distal margin with fringe of relatively long setae (compared to P5); dactylus marginally longer than for P5, fully retractile. P7 slightly shorter but similar in structure to P6, except carpus relatively shorter, about 0.8 x merus and 0.9 x propodus. Genital papillae located medially at base of P7. U1 peduncle relatively long and slender, exceeding limit of peduncle of U2, outer margin slightly serrated; rami sub-equal in length, about 0.6 x peduncle length, with serrated margins. U2 peduncle relatively broader than for U1, especially distally, outer margin slightly serrated; endopod slightly shorter than peduncle, broader and longer than exopod (about 1.4 x); both rami with serrated margins. U3 peduncle with convex outer margin and medial ridge; endopod slightly shorter than peduncle, slightly broader and longer than exopod; both rami with serrated margins. Telson relatively narrow, with rounded apex, length almost 2 x width at base, exceeding limit of peduncle of U3 to about 1/3 of endopod length.

Description of female ( Figs 3–4 )

Specimen (USNM 1089977) recently ovigerous, judging by the well-developed oostegites, measuring about 40 mm along a parabolic line drawn through the mid-section of the body from the front of the head to the tip of the telson. Remarkably similar to male except for the following. Pereon and pleon slightly broader and more robust but distorted and not suitable for illustration. Mandibular palp article 3 about 1.5 x as long as first two combined. Second antennae with relatively longer first flagellar article, about 1.9 x length following article. G1 basis not broadened proximally. P5 basis marginally more slender. Telson barely reaching limit of peduncle of U3.

Figures

FIGURE 1. Megalanceoloides remipes (K.H. Barnard, 1932), male, 34 mm, from western Drake Passage (USNM 1090239). Scale bars = 5.0 mm (habitus); 1.0 mm (remainder).

FIGURE 2. Megalanceoloides remipes (K.H. Barnard, 1932), male, 34 mm, from western Drake Passage (USNM 1090239). Scale bar = 1.0 mm.

FIGURE 3. Megalanceoloides remipes (K.H. Barnard, 1932), female, about 40 mm, from eastern Drake Passage (USNM 1089977). Scale bar = 1.0 mm.

FIGURE 4. Megalanceoloides remipes (K.H. Barnard, 1932), female, about 40 mm, from eastern Drake Passage (USNM 1089977). Scale bar = 1.0 mm.