Lycaea proserrata, Zeidler, 2021

Zeidler, Wolfgang, 2021, Review of the hyperiidean amphipod family Lycaeidae Claus, 1879 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 5081 (1), pp. 1-59 : 31-34

Lycaea proserrata sp. nov.

( Figs 14–15 )

Material examined. Holotype. Male , 7.0 mm, USNM 1246984 . Tropical W. Atlantic, N.E. of French Guiana [08°N 44°W], R/ V Gilliss, USNOO Expedition stn. 2-T1-C, trawl 10 feet, Farquhar, 20 January 1969.

Allotype. Female, 6.2 mm, NHMD-228266 , Dana stn. 3920 vii, S.W. Indian Ocean, N.E. of Seychelles [01°12’S 62°19’E], 600 mw, 9 December 1929.

Paratypes. All from the following Dana stations. Indo-Pacific: 2 females, 1 male, NHMD-228250 , 3734 iii [11°43’N 121°03’E], 300 mw, 27 June 1929 ; 5 females, 5 males, NHMD-228252 , 3800 iii [07°53’S 116°18’E], 300 mw, 18 August 1929 ; 4 females, NHMD-288253 , 3800 v [07°53’S 116°18’E], 50 mw, 18 August 1929 . Indian Ocean, from Bali to South Africa: 1 female, 1 male, NHMD-228260 , 3908 v [04°28’N 81°13’E], 100 mw, 22 November 1929 ; 1 male, NHMD-228264 , 3918 iv [00°35’N 66°09’E], 300 mw, 7 December 1929 ; 2 females, NHMD-619991 , 3920 vii [01°12’S 62°19’E], 600 mw, 9 December 1929 ; 3 females, 3 males, NHMD-228270 , 3921 viii [03°36’S 58°19’E], 100 mw, 11 December 1929 ; 6 females, 3 males, NHMD-228271–2 , 3924 iv–v [05°01’S 54°46’E], 100 & 50 mw, 14 December 1929 ; 4 females, 4 males, NHMD-228273–4 , 3925 iv–v [07°13’S 52°22’E], 100 & 50 mw, 16 December 1929 ; 1 male, NHMD-228277 , 3937 i [09°26’S 46°05’E], 500 mw, 22 December 1929 ; 1 female, NHMD-228279 , 3938 i [09°10’S 45°17’E], 500 mw, 23 December 1929 ; 4 females, 1 male, NHMD- 228282–3 , 3941 i–ii [07°24’S 41°51’E], 500 & 400 mw, 24 December 1929 ; 2 females, NHMD-228286–7 , 3942 ii, 3942 v [06°47’S 41°27’E], 400 & 100 mw, 25 December 1929 ; 3 females, NHMD-228288–9 , 3954 ii–iii [16°53’S 42°12’E], 300 & 200 mw, 9 January 1930 ; 1 female, 1 male, NHMD-228290–1 , 3957 ii, 3957 v [21°30’S 42°32’E], 300 & 50 mw, 11 January 1930 . Tropical Atlantic: 2 males, NHMD-228294 , 3997 ii [11°S 07°36’W], 600 mw, 27 February 1930 ; 1 female, NHMD-228300 , 3998 iv [07°34’S 08°48’W], 100 mw, 1 March 1930 ; 1 male, NHMD- 620067 , 4001 iv [03°56’N 12°32.5’W], 100 mw, 6 March 1930 . Additional male from S.W. Indian Ocean, off South Africa, SAMA C12600, Meiring Naude stn. SM 152D [30°13’30”S 31°27’30”E], 212 m, 17 May 1977 .

Other material: All from the following Dana stations, mostly in poor condition. Atlantic Ocean: 1 male, NHMD-228240 , 946 ; 4 females, 4 males, NHMD-228295 , 3997 iv; 1 female, NHMD-228299 , 3997 v; 8 females, NHMD-228301 , 3998 v; 5 females, NHMD-288302 , 4000 iv; 1 female, NHMD-288303 , 4000 x. Pacific Ocean: 1 female, 1 male, NHMD-228243 , 1208 xiv; 1 female, NHMD-228249 , 3620 v. Indian Ocean: 2 females, 2 males, NHMD-228246–7 , 3556 v–vi; 1 male, NHMD-228254 , 3804 iii; 2 females, 1 male, NHMD-228261 , 3913 v; 1 female, NHMD-228265 , 3918 v; 3 females, NHMD-228267 , 3920 viii; 3 females, 1 male, NHMD-228269 , 3921 vii; 4 females, NHMD-228278 , 3937 iii; 1 female, NHMD-228281 , 3939 ii.

Description of holotype. Male, 7.0 mm. Head sub-spherical, with small rounded knob anteriorly, about 1.3 x as deep as long, as long as first 4.5 pereonites combined. Buccal mass barely protruding below head. Callynophore of A1 without antero-distal corner; postero-distal corner small, rounded, partly over-lapping following article. G1 and G2 sub-chelate, G2 slightly longer than G1. G1 basis marginally inflated; merus with relatively straight distal margin, not v-shaped as in all other congeners; carpus sub-rectangular, about as wide as long, with small, sharp, postero-distal tooth; postero-distal corner of propodus not produced posteriorly to dactylus; dactylus relatively long and slender, almost as long as propodus. G2 very similar to G1 except carpus is more rectangular, slightly longer than wide. P3–6 with relatively short, slender dactylus, those of P3 and P4 about 0.2 x propodus, or slightly more. P3 and P4 morphologically similar, P4 marginally longer than P3; merus not inflated anteriorly as in other species, sub-equal in length to propodus, about 0.6 x basis; propodus length 1.2–1.3 x carpus. P5 length about 1.3 x P4, 1.2 x P6; basis rectangular, relatively slender, length about 2 x maximum width; merus sub-equal in length to propodus, almost 0.7 x basis; carpus length about 0.7 x propodus. P6 basis oval-shaped, with evenly convex margins, length about 1.5 x maximum width; merus length about 0.5 x basis, slightly shorter than propodus; carpus length about 0.8 x propodus; anterior margin of carpus and propodus, and antero-distal corner of merus, slightly serrated. P7 basis almost spherical, marginally longer than wide, length about 0.6 x basis of P6; length of remaining articles less than 0.3 x basis; dactylus sharp, hook-like. U1 and U2; endopod not fused with peduncle. U1 peduncle length about 3.0 x exopod; rami equal in length. Telson relatively narrow, length about 1.6 x width at base, with slight, but distinct, concavity on the margins, about one-third from the tip, apex evenly rounded, almost pointed.

Description of allotype. Female, 6.2 mm. Like holotype except for the following. Head relatively deep, almost 1.7 x as deep as long, as long as first 4 pereonites combined, without anterior knob. Dactylus of G1 and G2 slightly shorter, about 0.8 x propodus. P7 basis more elongate, length about 1.5 x width. Telson without concavity on margins, length only 1.3 x width at base.

Variations. The excavation of the carpus of G1 and G2 can vary slightly, sometimes approaching that of L. serrata , especially in some females, and the propodus is often extended slightly beyond the postero-distal corner of the carpus.

Etymology. This species is named “ proserrata ” (from the latin “ pro ”, just as) to indicate that it closely resembles L. serrata in that G1 and G2 have a long dactylus and the propodus lacks the characteristic postero-distal corner, and in that the articles distal to the basis of P7 are together relatively short. The morphology of G1 and G2 sometimes approaches that of L. serrata .

Remarks. It is with some hesitation that I describe this species as new to science but it has a number of characters that cannot be easily reconciled with any other species. The morphology of the male A1, lacking an antero-distal corner, alone distinguishes it from L. bovallii and L. vincentii . The morphology of G1 and G2 readily distinguish it from L. lilia and L. osbornae and also from L. pulex which have shorter dactyls and the propodus has a distinct, slightly serrated, postero-distal corner. Also, L. pulex is distinguished by the relatively short peduncle of U1. This species also bears some resemblance to L. nasuta but is readily distinguished from it by the longer dactylus of G1 and G2, the morphology of G2, the relatively longer and more slender telson and in that the endopod of U2 is not fused with the peduncle. Thus, L. proserrata is most similar to L. serrata and it is likely that the two have been confused in the past. However, in L. serrata the carpus of G1 and G2 is distinctly more excavate, and although this character can vary slightly with the excavation ranging from moderate to extreme, usually more extreme for G1, it is usually greater than found in L. proserrata . Also, males of L. proserrata are readily distinguished by the more slender habitus (compare figs 14 and 19) and are further distinguished from L. serrata by the following characters of that species: i) specimens of similar size, have a smaller head without an anterior knob; ii) the buccal mass extends well below the head; iii) some of the pereonites and pleonites are denticulate; iv) the merus and carpus of P5 are relatively broad (even in smaller specimens 5–6 mm); v) the dactylus of P7 is vestigial; vi) the peduncle of U1 is relatively short (only 2 x exopod); and vii) the telson is only marginally longer than wide; characters that are all at odds with L. proserrata . The long, relatively narrow, telson of L. proserrata males is especially distinctive, often with a slight concavity on the margins, about one-third from the tip. An unusual character noted for this species is that the distal margin of the merus of G1 and G2 is relatively straight, not v-shaped, over-lapping the carpus, which is characteristic of all other congeners. This character seems to be consistent in all the specimens examined and readily distinguishes this species. It is especially useful in distinguishing females from smaller (<9 mm) specimens of L. serrata in which the pereonites and pleonites are often only slightly carinate. Large females of L. serrata (> 9 mm) are easily distinguished by the inflated pereonites and the raised dorsal corners of the pleonites (fig. 18).

This is one of the smaller species of Lycaea , with females mature at about 5–7 mm and males at 6–9 mm. One female (NHMD-228295) is ovigerous at 5.2 mm. A gelatinous associate has not been recorded.

Distribution. The Dana collections, as detailed above, indicate that this species is widely distributed in the tropical regions of the Atlantic, Pacific and Indian Oceans. It seems to be most common in the Indian Ocean.

Figures

FIGURE 14. Lycaea proserrata sp. nov. Holotype male, 7.0 mm, USNM 1246984. Scale bars = 1.0 mm (habitus); 0.5 mm (A2, G1–P7); 0.2 mm (A1, Us).

FIGURE 15. Lycaea proserrata sp. nov. Allotype female, 6.2 mm, NHMD-228266. Scale bars = 1.0 mm (habitus); 0.2 mm (remainder).