Mimonectes gaussi (Woltereck, 1904)

Zeidler, Wolfgang, 2012, A review of the hyperiidean amphipod families Mimonectidae and Proscinidae (Crustacea: Amphipoda: Hyperiidea: Scinoidea) 3533, Zootaxa 3533, pp. 1-74 : 33-37

Mimonectes gaussi (Woltereck, 1904)

( Figs. 14–15)

Sphaeromimonectes gaussi Woltereck, 1904b: 629 .— Woltereck 1906: 868, fig. 4. Woltereck 1927: 80–81, figs, 18–22.

Mimonectes gaussi — Stephensen & Pirlot 1931: 531. Shoemaker 1945: 221–224, figs. 26–27. Vinogradov 1957: 167, 179 (table) [English]. Vinogradov 1960: 218–219. Vinogradov 1964: 126–127. Vinogradov 1970: 385 (table). Sanger 1973: 10, 15. Thurston 1976: 384–385 (table), 391. Vinogradov et al. 1982: 113 (key), 119–120, fig. 50. Vinogradov 1990: 51. Vinogradov 1991: 261 (table). Vinogradov 1999: 1147 (table), 1171, fig. 4.43. Escobar-Briones et al. 2002: 367 (list). Gasca 2009: 86 (table). Mori et al. 2010: 3 (list), 8 (list).

Parascina fowleri Stebbing, 1904: 21–22 , pl. 2B.— Chevreux 1905: 1 (part). Scott 1909: 33–34, pl. 2, figs. 10–16; pl. 3, figs. 16–17. Woltereck 1909: 151. Chevreux 1919: 9–10 (part). Stephensen 1923: 7–8 (part). Schellenberg 1927: 602–603, fig. 12. Pirlot 1929: 55–56. Barnard 1932: 252–253. Chevreux 1935: 142–143.

Mimonectes fowleri — Stephensen & Pirlot 1931: 519–528, figs. I.3, II.5, VII–X. Stephensen 1932: 376 (list). Pirlot 1939: 22. Reid 1955: 13 (only stn. 82).

Mimonectes diomedeae [mis-identification]— Shoemaker 1945: 221–224 (part).

Type material. The unique holotype is in the MFN (21334). It is a partly dissected, mature female, with welldeveloped oostegites, measuring about 20 mm. The type locality is the north-east Atlantic (40°34’N 12°46’W); collected by the Gauss, Deutschen Südpolar-Expedition, 26 July 1901.

Type material of synonyms. Type material of P. fowleri is in the NHM (1905.111.8.22), consisting of two male or juvenile specimens; one mounted whole on a microscope slide, probably the one illustrated by Stebbing (1904), measuring about 8 mm and one other, damaged specimen, measuring about 9 mm, used to illustrate the mouthparts. The type locality is the Bay of Biscay , HMS Research stns. 26b & 27a, 2000–1500 & 1250–0 fathoms respectively, G.H. Fowler, 26 June 1903. An examination of this material has confirmed the generally accepted synonymy .

Material examined. Types. The holotype of M. gaussi and the syntypes of P. fowleri as detailed above.

Other material examined. N.E. Atlantic: Two males ( ZMUC); south of Iceland (61°34’N 19°03’W), Thor stn. 180, 1800 mw, 10 July 1904 . Eight males ( ZMUC); south of Iceland (61°30’N 17°08’W), Thor stn. 183, 1800 mw, 11 July 1904 . Eighteen females, 11 juv. ( USNM 1149253 ); off Portugal, R/ V Discovery, 1959. Female ( ZMUC); Gulf of Guinea (05°27’N 00°07’E), Atlantide stn. 82, 0–100 m, 29 January 1946 . Male & two males & female, male ( ZMUC); north of Madeira (33°26’N 16°59’W), Dana stns. 1142 VI, VII & IX, 5000, 4000 & 2000 mw respectively, 15 October 1921 . Male ( ZMUC CRU-20415); west of Sierra Leone (08°26’N 15°11’W), Dana stn. 4003 II, 5000 mw, 9 March 1930 . N.W. Atlantic: Seven females, two males, two juv. ( USNM 1149263 ); mid- Atlantic (27°44’N 37°10’W), R/ V Pillsbury stn. P6511–21cx, 270–430 m, 1 November 1966 . Juv. ( ZMUC); Davis Strait , Greenland (63°06’N 56°00’W), Ingolf stn. 24, 377–0 m, 25 June 1895 . Female ( ZMUC); north of Brazil (08°19’N 44°35’W), Dana stn. 1171, 3000 mw, 13 November 1921 . Two females ( ZMUC); Caribbean Sea (17°54’N 64°54’W), Dana stn. 1186 III, 3000 mw, 30 November 1921 . Juv. male ( SAMA C6877 ); Veach Canyon, east of New York (39°51.34’N 69°37.15’W), ROV dive 2139–5, ex. G. Matsumoto, 8 August 1987 . Two males ( SAMA C6878 ); western Caribbean Sea, off Chincharro Bank (18°34.783’N 87°08.609’W), Gordon Gunter ( NOAA) stn. 49, J. Lamkin, 3 March 2006 . S.E. Atlantic: Two males & juv. male ( ZMUC); off South Africa (30°15’S 13°15’E), Dana stns. 3978 VII &VIII, 4000 & 3000 mw respectively, 13 February 1930 . Female ( ZMUC); off South Africa (23°26’S 03°56’E), Dana stn. 3980 IX, 3000 mw, 17 February 1930 . Female ( ZMUC); north of St. Helena (07°34’S 08°48’W), Dana stn. 3998 IX, 3000 mw, 1 March 1930 . Female , male & female ( ZMUC); south of Liberia (00°31’S 11°02’W), Dana stns. 4000 IV & VIII, 100 & 4000 mw respectively, 4 March 1930 . Female ( ZMUC); Gulf of Guinea (04°00’S 08°25’E), Galathea stn. 66, 5300 mw, 5 December 1950 . S.W. Atlantic: Female ( USNM 1149252 ); east of Pernambuco, Brazil (08°05’S 25°24’W), R/ V Gillis, stn. 6-T7 (USNOO exped.), 720 m, 10 February 1969 . N.W. Pacific: Female ( SAMA C6879 , ex. JAMSTEC), Sagami Bay , Japan (35°01’N 139°21.6’E), 559 m, ROV HyperDolphin dive 306, 15 June 2004 . Juv. ( SAMA C7574 , ex. JAMSTEC); Sagami Bay , Japan (35°00’N 139°20’E), R/ V Tansei Maru stn. P-MTD-2 (cruise KT 96–10), 400 m, col. D.J. Lindsay, 13 July 1996 . Juv. ( SAMA C7575 , ex. JAMSTEC); Sagami Bay , Japan (35°00’N 139°20’E), R/ V Kaiyo stn. IO60315A-5 (cruise KY 06–03), 450–500 m, col. D.J. Lindsay, 15 March 2006 . Male ( SAMA C7576 , ex. JAMSTEC); Sagami Bay , Japan (34°50’N 139°36’E), R/ V Kaiyo stn. IO60320A-4-2 (cruise 06–03), 600–700 m, col. D.J. Lindsay, 20 March 2006 . Female ( SAMA C7577 , ex. JAMSTEC); Sagami Bay , Japan (34°41’N 139°49’E), R/ V Kaiyo stn. IO60324D-2 (cruise 06–03), 600–650 m, col. D.J. Lindsay, 24 March 2006 . Juv. ( SAMA C7578 , ex. JAMSTEC); Sagami Bay , Japan (34°41’N 139°49’E), R/ V Kaiyo stn. IO60324D-6 (cruise 06–03), 400–450 m, col. D.J. Lindsay, 24 March 2006 . Female ( SAMA C7579 , ex. JAMSTEC); Suruga Bay , Japan (34°32’N 138°32’E), R/ V Kaiyo stn. IO40328b-6H (cruise 04–03), 11–1000 m, col. D.J. Lindsay, 24 March 2004 . Two females ( SAMA C7014 , ex. JAMSTEC); outside Kurose Hole, S. of Sagami Bay , Japan (33°48’N 139°56’E), R/ V Yokosuka stn. IO704 (cruise YK 07–06), 500–595 m, col. D.J. Lindsay, 21 April 2007 . Male ( SAMA C6880 , ex. JAMSTEC), Suruga Bay , Japan (34°32’N 138°32’E), 11–1000 m, col. D.J. Lindsay, 28 May 2004 . N.E. Pacific: Female ( SAMA C6945 ); off Vancouver I. (48°20’N 125°04’W), ex M. Galbraith, cruise WCU1, 250–0 m, Aug / Sept 2009 . S.E. Pacific: Male ( ZMUC); south-east of Panama (00°18’S 99°07’W), Dana stn. 3558 II, 2000 mw, 18 September 1928 . Female ( ZMUC); south of Tahiti (18°49’S 153°10’W), Dana stn. 3577 IX, 2000 mw, 19 October 1928 . S.W. Pacific: Female ( ZMUC); near Samoa (11°00’S 172°37’W), Dana stn. 3587 V, 2000 mw, 2 November 1928 . Female ( ZMUC); east of New Caledonia (20°00’S 174°29’E), Dana stn. 3602 VII, 3000 mw, 22 November 1928 . Juv. ( ZMUC); near New Caledonia (22°43’S 166°05.8’E), Dana stn. 3613 VIII, 3000 mw, 22 November 1928 . Male ( ZMUC); north of New Zealand (25°47’S 172°24’E), Dana stn. 3621 III, 3000 mw, 8 December 1928 . Female , two males & male & male ( ZMUC); north of New Zealand (30°08’S 176°50’E), Dana stns. 3627 II, III & IV, 4000, 3000 & 2000 mw respectively, 14 December 1928 . Three females, 25 males ( ZMUC); north of New Zealand (34°24’S 178°42.5’E), Dana stn. 3630 II, 2000 mw, 17 December 1928 . Eight males & four females, male ( ZMUC); east of New Zealand (41°47’S 176°55’E), Dana stns. 3640 VII & VIII, 2500 & 2000 mw respectively, 7 January 1929 . Female ( ZMUC); west of New Zealand (35°36’S 171°52’E), Dana stn. 3651 VI, 600 mw, 22 January 1929 . Male ( ZMUC); Tasman Sea (33°30.5’S 165°53’E), Dana stn. 3653 VII, 3500 mw, 26 January 1929 . Female & three males ( ZMUC); Tasman Sea (33°26’S 157°02’E), Dana stns. 3656 II & IV, 4000 & 2000 mw respectively, 29 January 1929 . Indo-Pacific: Male & two males ( ZMUC); South China Sea (06°55’N 114°02’E), Dana stns. 3688 III & IV, 3000 & 2000 mw respectively, 8 April 1929 . Female, male ( ZMUC); South China Sea (07°13.5’N 111°49’E), Dana stn. 3689 III, 2000 mw, 9 April 1929 . E. Indian: Female & male ( ZMUC); south of the Maldives (01°45’N 71°05’E), Dana stns. 3917 II & IV, 3700 & 2200 mw respectively, 15 December 1929 .

Diagnosis. Females: Body length up to 20 mm, reaching sexual maturity at about 15 mm or less. Pereon of mature specimens moderately inflated, due to enlarged pereonites 1–5. Antennae 1 as long as head and first 1.5 pereonites combined (medially). Antennae 2 much reduced, consisting of two small articles. Gnathopod 1; basis almost as long as remaining articles combined; carpus and propodus of similar length; propodus armed with long, fine setae on both margins, antero-distal corner produced into relatively long, sharp process over-lapping the dactyl, postero-distal corner similarly produced but much shorter; dactyl long and slender, length about 0.4x propodus. Gnathopod 2 slightly longer and more slender than G1; basis almost as long as remaining articles combined; carpus slightly shorter than propodus; propodus with fine setae on distal margin, both distal corners produced as for G1; dactyl as for G1, length about 0.3x propodus. Pereopods 3 & 4 similar in structure with P4 marginally longer; merus relatively short, length slightly less than twice ischium, or about 0.25x basis, with anterodistal corner slightly produced forward; carpus slightly shorter than basis, amygdaloid in shape, mid-width almost 0.3x length; propodus length about 0.6x carpus, relatively narrow, tapering distally. Pereopod 5 slightly longer than P4; basis length twice merus; carpus length 1.4x merus; propodus length almost 0.8x carpus, relatively thin, tapering distally; dactyl very short and thin. Pereopod 6; length about 0.7x P5; basis length slightly more than twice merus; carpus length 1.5x merus; propodus slightly shorter than carpus, relatively thin, tapering distally; dactyl very short and thin. Pereopod 7 slightly shorter than P6; structure and relative lengths of articles similar to P6. Uropoda with relatively broad peduncles and rami; all with inner ramus slightly longer than outer and slightly shorter than peduncle. Uropod 1; inner ramus length 1.5x outer, and 0.9x peduncle. Uropod 2; inner ramus length 1.6x outer, and 0.8x peduncle. Uropod 3; inner ramus length 1.2x outer, and 0.9x peduncle; peduncle width about 0.6x length. Telson triangular; length about 0.3x peduncle of U3.

Males: Like females except for the following. Largest male recorded only about 9 mm, reaching sexual maturity at about 8 mm. Pereon slightly arched, oval-shaped from dorsal aspect; pereonites 1–4 sometimes with slight dorsal keel (fig. 15). Antennae 1 as long as head and first five pereonites combined; peduncular articles and callynophore relatively broader. Antennae 2 reduced in immature specimens, about 0.7x (or more) length A 1 in mature specimens. Articles of G1–P4, all relatively more slender. Gnathopod 1; basis length only 0.6x remaining articles combined; propodus slightly shorter than carpus, with numerous long, fine setae anteriorly; dactyl relatively stronger. Gnathopod 2 slightly shorter than G1; relative lengths of articles similar to G1. Pereopods 3 & 4; carpus linear, not amygdaloid; merus relatively longer, length about 0.4x basis; propodus only slightly shorter than carpus. Pereopod 4 marginally shorter than P3. Pereopod 5; basis length 2.5x merus; carpus length 2.2x merus; dactyl slightly stronger. Pereopod 6 marginally longer than P5, and longest pereopod; basis length 2.2x merus; carpus length 2.1x merus; propodus length 0.8x carpus; dactyl slightly stronger. Pereopod 7 similar to P 5 in length and relative lengths of articles. Uropoda with rami marginally more slender in immature specimens, sometimes with inner ramus of U3 slightly longer than the peduncle (fig. 14).

Colour, according to water-colour paintings by K. Stephensen (in ZMUC) of female from Dana stn. 1171, pale-red to pink with slightly darker abdomen. Based on photo provided by D.J. Lindsay—pereon, buccal mass and gnathopods rose-red; pleon light red; remainder mainly translucent.

Remarks. This is a much smaller species than the previous two, with females reaching sexual maturity at about 15 mm and males at about 8 mm. Also, unlike the previous two species, the pereon of mature females is only moderately inflated (fig. 14). Stephensen and Pirlot (1931), for example, illustrate an ovigerous female, about 10 mm in length, with the pereon only slightly inflated.

This species is very similar to M. diomedeae . Both are readily distinguished from all their congeners by the morphology of the gnathopods, in that they are the only species where the antero-distal angle of the propodus is projected into a distinct, sharp process, partly over-lapping the dactyl. Mimonectes gaussi differs from M. diomedeae mainly in the shape of the propodus of the gnathopods. In M. gaussi it is relatively narrow, tapering distally, whereas in M. diomedeae it is oval-shaped, almost not tapering distally, and the antero-distal denticle is broader, more-or-less petaloid. Additional distinguishing characters are as follows. In females of M. gaussi pereopods 6 & 7 are much shorter than pereopod 5 (relatively longer in M. diomedeae ), and the propodus of pereopods 5–7 is distinctly shorter than the carpus (similar in length or marginally longer in M. diomedeae ). Males of M. gaussi have pereopods 3–5 with stronger dactyls (feeble in M. diomedeae ), the carpus of pereopods 3 & 4 is not inflated (amygdaloid), and the propodus of pereopods 5–7 is distinctly shorter than the carpus (longer than carpus, especially for P 7 in M. diomedeae ).

An immature male specimen (5.6 mm) from the north-west Atlantic (SAMA C6877), captured by submersible, was found in association with the ctenophore Bolinopsis sp. This specimen also differed from others in having slightly more slender pereopods and uropoda, and relatively longer rami (fig. 14). Another specimen, an immature female, from Japan (SAMA C6879), also captured by submersible, was found in association with an unidentified lobate ctenophore.

Distribution. This species is not as common as the previous two, but it has been recorded from all the world’s oceans except the Mediterranean Sea. In the Atlantic most previous records are from the north, ranging from the Davis Strait ( Stephensen 1923) to Madeira and Bermuda, with only one record from the south, off South Africa ( Barnard 1932 —as Parascina fowleri ). In the Pacific it has been recorded from various regions, in the north-west from the Kuril-Kamchatka region to the Philippines and off Mexico, and in the south from near the Kermadec Trench and off the coast of Chile. The only record from the north-eastern Pacific is by Sanger (1973) who records it from off British Columbia, but this identification needs to be verified. The only previous record from the Indian Ocean is by Vinogradov (1964) who recorded it from the Arabian Sea and the tropics to 19°S.

The Dana collected this species from all major oceans, providing many range extensions, particularly in the tropical and South Pacific, with new records for the South China Sea (stns. 3688 & 3689) and the Tasman Sea (stns. 3653 & 3656). The latter is also a new record for Australian waters. In the Indian Ocean the Dana only collected it from one station (3917), near the Maldives, indicating that this species, like the previous two, may be less common there than in the Atlantic or Pacific. Additional records for the north-western Atlantic and Japanese waters are provided by specimens in museum collections (SAMA). Surprisingly there are no confirmed records from the north-east Pacific.

According to Vinogradov et al. (1982), this species is usually found in depths exceeding 500 m, but rises to shallower depths. Most of the Dana specimens were collected with 2000–4000 mw, with two at 5000 mw, and only one each at 100 mw and 600 mw.