Lycaea osbornae, Zeidler, 2021

Zeidler, Wolfgang, 2021, Review of the hyperiidean amphipod family Lycaeidae Claus, 1879 (Crustacea: Amphipoda: Hyperiidea), Zootaxa 5081 (1), pp. 1-59 : 24-25

Lycaea osbornae sp. nov.

( Figs 10–11 )

Material examined. Holotype: Female, 4.7 mm, USNM 1242790 . North Atlantic , Georges Bank, S. of Massachusetts [39°26’N 68°03’30”W], R/VAlbatross, surface, 31 August 1885.

Allotype: Male, 5.2 mm (recently moulted), NHMD-228125 , Dana stn. 3563 iv, S.E. Pacific, N.E. of Marquesas Is. [07°45.5’S 131°22’W], 100 mw, 29 September 1928.

Paratypes 1: 1 female, 3.7 mm, USNM 1242790 , collected with holotype. 2 : 1 female, 3.3 mm, SAMA C12577, N.E. Pacific, off Vancouver Island [49°15.09’N 126°40’W], “LaPerouse and Line P Monitoring Program”, stn. A 4, 250 m, September 2009 (from M. Galbraith). On the salp Cyclosalpa bakeri Ritter, 1905 . 3 : 1 female 5.8 mm, NHMD-619242 , collected with allotype. 4 : 1 female, 4.4 mm, NHMD-228132 , Dana stn. 3843 iv, S.E. Indian Ocean, N. of Cocos / Keeling Is. [09°59’S 97°56’E], 200 mw, 9 October 1929. 5 : 2 females, 6.1 and 6.5 mm, NHMD- 228242 , Dana stn. 1208 iii, N.E. Pacific, off Panama [06°48’N 80°33’W], 300 mw, 16 January 1922. 6 : 2 males about 8.6 mm, NHMD-228248 , Dana stn. 3563 v, same data as allotype but 50 mw .

Description of holotype. Female, 4.7 mm. Head relatively large, rounded, much deeper than long (about 1.7 x), as long as first 3 pereonites combined. Buccal mass protruded well below head. G1 and G2 sub-chelate, G1 slightly shorter than G2. G1 with slightly inflated basis; carpus rectangular with small, pointed, postero-distal tooth, reaching to about the middle of the propodus; propodus with small, slightly serrated, postero-distal corner produced very slightly posteriorly to dactylus; dactylus slender, relatively long, length 0.5 x propodus. G2 similar to G1 except for basis which is more slender and longer (1.5 x that of G1) accounting for the extra length. P3–6 with very short, stubby dactylus, those of P3 and P4 about 0.2 x as long as propodus, or slightly more. P3 and P4 morphologically similar, P4 slightly longer than P3; merus marginally inflated anteriorly, marginally longer than propodus, about 0.5 x basis; carpus marginally shorter than propodus. P5 length about 1.2 x P4 and P6; basis rectangular, length about 2 x maximum width; merus marginally inflated anteriorly, sub-equal in length to propodus, about 0.6 x basis; carpus length about 0.8 x propodus. P6 basis rectangular but slightly wider medially, length about 2 x maximum width, slightly shorter than basis of P5; merus with slightly serrated antero-distal corner, slightly inflated anteriorly, maximum width almost 0.6 x length, slightly shorter than propodus, about 0.5 x basis; carpus relatively wide but more or less rectangular, length about 0.6 x propodus; anterior and distal margin of carpus and anterior margin of propodus, slightly serrated. P7 basis with bulging posterior margin, length about 1.7 x maximum width, about 0.7 x basis of P6; remaining articles together relatively long, almost 0.7 x basis; propodus with antero-distal corner produced into small, rounded lobe; dactylus sharp, hook-like. U1 and U2; endopod not fused with peduncle. U1 peduncle relatively short, about 1.7 x length of exopod or only slightly longer; rami relatively slender, endopod slightly longer than exopod. U2 endopod slightly longer than peduncle. Telson rounded, length marginally shorter than width at base.

Description of allotype. Male, 5.2 mm. Like holotype female except for the following. Head relatively large, rounded, much deeper than long (about 1.5 x), as long as first 4 pereonites combined. A1 callynophore without antero-distal corner; postero-distal corner small, rounded, separated from following article by distinct notch. Dactylus of G1 and G2 slightly longer, about 0.7 x propodus. P5 length about 1.3 x P4 and P6; basis relatively longer about 2.4 x width. P6 merus equal in length to propodus. P7 basis more rectangular, length about 2 x width; length of remaining articles together slightly less than 0.4 x basis. U1 peduncle slightly longer, about 2 x length of exopod. U2 endopod slightly shorter than peduncle.

Paratype USNM 1242790. Female, 3.7 mm. This specimen is in poor condition but is like the holotype except for the morphology of G2 where the postero-distal corner of the carpus is relatively small, barely reaching to about one-third of the propodus ( Fig. 10A ). However, this may be a juvenile character as noted for stage iv of L. pulex by Harbison (1976). Also, the dactylus of G1 and G2 is relatively shorter and less slender than for the holotype.

Paratype SAMA C12577. Female, 3.3 mm, recently moulted, immature. It is like the holotype in all respects except that the dactylus of G1 and G2 ( Fig. 10B ) and P3–6 are marginally longer and sharper. However, one might expect that the dactyls of recently moulted specimens might be less worn and hence slightly longer and sharper. Collected on the salp Cyclosalpa bakeri Ritter, 1905 .

Paratype NHMD-619242. Female, 5.8 mm. Morphologically identical to the holotype. The dactylus of P6, on the right, is partly retracted.

Paratype NHMD-228132. Female, 4.4 mm. Like the holotype. The dactylus of G2 is marginally longer.

Paratypes NHMD-228242. Two females, 6.5 and 6.1 mm. Both are like the holotype except that the dactylus of G2 is slightly longer and in the smaller specimen the postero-distal corner of the carpus of G1 and G2 is worn and both are more excavate, especially on the left side. The larger specimen is ovigerous.

Paratypes NHMD-228248. Two males, about 8.6 mm, one with head detached. Both with mature antennae and head with rounded knob as occurs in mature specimens of L. nasuta ( Fig. 9 ), otherwise like the allotype. One specimen with the dactylus of P6, on the right, fully retracted ( Fig. 11 ).

Etymology. I take great pleasure in naming this species for my colleague Dr Karen Osborn, Research Zoologist/ Curator, Department of Invertebrate Zoology, Smithsonian National Museum of Natural History, Washington DC, in acknowledgement for her, and her team’s, research efforts investigating the evolutionary significance of vision and eye morphology in hyperiideans, and also for gaining the funds to enable me to spend two months at the Smithsonian in 2015, thus, in part, making this current review possible.

Remarks. Lycaea osbornae is most similar to L. lilia based on the morphology of G2. It differs primarily in that the morphology of G1 is like that of G2 and in that the postero-distal corner of the carpus is pointed and the dactylus is relatively longer and slender (not stubby). In addition, the peduncle of U1 is relatively shorter, less than 2 x the length of the exopod (about 2.5 x or more in L. lilia ) and the telson is wider and more rounded in L. lilia . Also, in Lycaea osbornae the peduncle of U2 is shorter than the endopod, a character only shared with L. pachypoda , L. pulex and males of L. serrata , all species from which L. osbornae is readily distinguished by the morphology of G1 and G2.

An unusual character of this species is the retractile dactylus of P6 which has not been found in any other species of Lycaea except L. intermedia but, as for that species, it is not evident in all specimens and can be difficult to determine unless the dactylus is at least partly retracted.

One paratype ( SAMA C12577) from the N.E. Pacific was collected on the salp Cyclosalpa bakeri Ritter, 1905 .

Distribution. Known only from a few records, from the type locality, the north and S.E. Pacific and the S.E. Indian Ocean, as detailed above.

Figures

FIGURE 9. Lycaea nasuta Claus, 1879. Male 6.2 mm (recently moulted), USNM 1241181. Scale bars = 0.5 mm (habitus); 0.2 mm (G1–P7, Us); 0.1 mm (A1).

FIGURE 10. Lycaea osbornae sp. nov. Holotype female, 4.7 mm, USNM 1242790. A. G1–2 from paratype female, 4.7 mm, collected with holotype. B. G1–2 from paratype female, 3.3 mm, SAMA C12577. Scale bars = 0.5 mm (habitus); 0.2 mm (G1–P7, Us); 0.1 mm (A1, G1–2 of A & B).

FIGURE 11. Lycaea osbornae sp. nov. Allotype male, 5.2 mm, NHMD-228125. P6’ from paratype male, 8.6 mm, NHMD- 228248. Scale bars = 0.5 mm (habitus); 0.2 mm (remainder).