Lycaea Dana, 1852

Zeidler, Wolfgang, 2016, A review of the families and genera of the superfamily PLATYSCELOIDEA Bowman & Gruner, 1973 (Crustacea: Amphipoda: Hyperiidea), together with keys to the families, genera and species, Zootaxa 4192 (1), pp. 1-136 : 48-53

Genus Lycaea Dana, 1852

( Figs 18–20 )

Lycaea Dana, 1852: 316 .— Dana 1853: 1017.— Bate 1862: 338.— Claus 1879: 32 (key), 37–39.— Carus 1885: 426.— Gerstaecker 1886: 485 –486.— Claus 1887: 55 (key), 61–62.— Stebbing 1888: 1563.— Chevreux & Fage 1925: 427 (key), 429.— Pirlot 1929: 136.— Hurley 1955: 180 (incl. key).— Bowman & Gruner 1973: 46 (incl. key).— Zeidler 1978: 26 (incl. key).— Vinogradov et al. 1982: 381 (key), 381–382.— Shih & Chen 1995: 170 (key), 170–171.— Vinogradov 1999: 1194 (incl. key).

Pseudolycaea Claus, 1879: 32 (key), 41.— Carus 1885: 426.— Gerstaecker 1886: 486.— Claus 1887: 56 (key), 64.— Chevreux & Fage 1925: 427 (key), 430.— Pirlot 1929: 138.— Bowman & Gruner 1973: 46 (key), 47.— Shih & Chen 1995: 170 (key), 183.

Metalycaea Stephensen, 1925: 183 .— Nair 1993: 1172.— Nair 1995: 6 (key), 7.

Type species. Lycaea ochracea Dana, 1853 by subsequent designation. Type material could not be found in any major North American museum and is considered lost (see Evans 1967). Although the description and figures of Dana (1853) readily characterise this genus they are insufficient to determine the status of his species. The type locality is the south-west Pacific , north of New Zealand, near Sunday Island , April 1840 .

The diagnosis of Lycaea , presented here is based mainly on L. pulex Marion, 1874 , as the specific status of L. ochracea is uncertain and L. pulex is the next oldest available name. Unfortunately, type material of Lycaea pulex is also considerd lost because none could not be found in any major European institution. However, Marion’s description and figures readily characterise the species. The type locality is the Mediterranean Sea, Gulf of Marseille.

Type species of synonyms. The type species of Pseudolycaea is P. pachypoda Claus, 1879 by monotypy. Type material could not be found at the MFN or ZMH and is considered lost. However , the description and figures of Claus (1879, 1887) readily characterise this species, which is considered to be insufficiently different from other species of Lycaea to warrant generic recognition (see Remarks). Claus (1879) records one female from the Mediterranean Sea , near Messina and one female from the tropical south-west Indian Ocean, near Zanzibar .

The type species of Metalycaea is M. globosa Stephensen, 1925 by monotypy. The three female syntypes are in the ZMUC (CRU-6567), in spirit. The specimens were collected from the Mediterranean Sea by the Thor ; stn. 112 [36°56’N 02°15’E], 25 mw, 27 June 1910; stn. 118 [41°00’N 06°43’E], 65 mw, 30 June 1910 and stn. 160 [35°59’N 28°14’E], 1000 mw, 1 August 1910. The specimens from stns. 116 & 118 are illustrated by Stephensen (1925). This species is considered to be a synonym of Lycaea serrata Claus, 1879 (see Remarks).

Diagnosis. Body shape robust or globular. Head rounded, often enlarged in females. Eyes occupying most of head surface; grouped in one field on each side of head. Antennae 1 of males with 2-articulate peduncle; flagellum with large, crescent-shaped callynophore, with aesthestascs arranged in two-field brush medially; with three smaller articles inserted on antero-dorsal corner. Antennae 1 of females with 2-articulate peduncle; callynophore narrowly rectangular; with two smaller articles inserted terminally. Antennae 2 absent in females. Antennae 2 of males 5-articulate; strongly zig-zagged, with most articles folded back on each other; extending anteriorly under head and posteriorly between the gnathopoda and pereopoda to pereonite 7; basal article distinctly inflated, about half or less the length of following article; following three articles of similar length; terminal article very short, not folded, pointing posteriorly. Mandibular incisor relatively broad, with several teeth, with small distal lobe medially; in male orientated more or less parallel to palp. Maxillae 1 consisting of tiny, rounded, plate-like lobes. Maxillae 2 absent. Maxilliped with inner lobes completely fused; medial margin of outer lobes with membranous fringe. Gnathopods 1 & 2 usually sub-chelate, rarely almost simple; carpal process knife-shaped, armed with microscopic teeth or setae. Pereopods 3 & 4 distinctly shorter than pereopods 5 & 6. Pereopod 5; basis about twice as wide as merus, non-locking but may overlap with P6; articles 3–7 inserted terminally to basis. Pereopod 6; basis slightly wider than twice merus, does not overlap, or lock, with opposing pereopod; articles 3–7 inserted terminally to basis. Pereopod 7 reduced in size with large basis; all articles present; dactylus normal. Uropod 1 with articulated exopoda and endopoda. Uropod 2 rarely with endopod fused with peduncle. Uropod 3; endopod fused with peduncle. Rami of all uropoda lanceolate, usually with serrated margins.

Species. About eight species of uncertain taxonomic status.

Sexual dimorphism. Apart from the morphology of the mandibles and the antennae, females are more robust than males, especially in the pereon. Males are generally more elongate, and have a relatively smaller head.

Remarks. This genus resembles Tullbergella (Oxycephalidae) in the morphology of the male antennae, mandibles and maxillae. Species of Lycaea , for which the morphology of the first antennae of males is known, fall into two groups. Those without a distal bulge on the anterior/dorsal margin of the callynophore ( L. pulex , L. serrata , L. nasuta and L. pachypoda ), and those with a slight distal bulge on the anterior/dorsal margin of the callynophore ( L. vincentii , L. bovalli and L. bajensis ). The latter approaching the condition found in Simorhynchotus , and all Oxycephalidae , except Glossocephalus . Thus, Lycaea is most closely related to the family Oxycephalidae and future studies may warrant its inclusion, and this is supported by the molecular studies of Browne et al. (2007) and Hurt et al. (2013).

Species of Lycaea have always been difficult to determine and a thorough revision of the genus is required. Harbison and Madin (1976) provide a useful key to eight species, which they consider valid. Of these eight species, Vinogradov et al (1982) recognise three, but they regard L. pauli Stebbing, 1888 , considered synonymous with L. pulex by Harbison and Madin, as valid, and include L. pachypoda and L. lilia Volkov, 1982 (described as new). Considering the state of taxonomic confusion of this genus it seems pointless to provide a key to species.

In the past the genus Pseudolycaea has been considered monotypic amongst the family Lycaeidae , because of the almost simple gnathopoda. In all other respects it resembles Lycaea . As the gnathopoda of Lycaea can vary from sub-chelate to almost simple ( L. serrata ), the validity of Pseudolycaea seems unjustified, and, like Vinogradov et al. (1982), it is here regarded a synonym of Lycaea . Similarly, Metalycaea , which Nair (1993) resurrected as a valid genus of Oxycephalidae , is considered to be a synonym of Lycaea , because the type species, M. globosa , is indistinguishable from mature female specimens of L. serrata . Like Simorhynchotus , its inclusion in the Oxycephalidae on the presumed absence of the maxillae has been demonstrated to be invalid. An examination of the type material of M. globosa has confirmed the synonymy, although it was not possible to examine the mouthparts for the presence or absence of maxillae. The specimens referred to by Nair (1993) have not been examined.

Lycaea is a well-known associate of salps ( Dana 1853, Marion 1874, Chevreux 1900), and Harbison (1976) even recorded the distribution of males, females and juveniles of L. pulex and L. vincentii on salp chains. From the available evidence, it seems that females may remain on the host, once settled, while males are more pelagic in habit, seeking out the settled females. The greater development of the pleon and urosome of the male supports this hypothesis.

Lycaea pulex and L. pachypoda have been recorded from Salpa maxima and pyrosomes ( Chevreux 1892, 1900, Chevreux & Fage 1925, Laval 1980). Lycaea pachypoda has also been recorded from the medusa Liriope tetraphylla (Harbison et al. 1977) , while L. pulex has been recorded in association with a variety of salps, Cyclosalpa pinnata , Pegea confoederata (Harbison 1976) ; Cyclosalpa affinis , C. bakeri , C. pinnata , Helicosalpa komanii , Ihlea punctata , Pegea socia , P. bicaudata , P. confoederata , Salpa cylindrica , S. maxima, Transtedtra multitentaculata (Madin & Harbison 1977). Similarly, L. nasuta has been recorded with Cyclosalpa affinis ; L. vincentii with Pegea confoederata and Salpa maxima , and L. ‘bovallioides’ with Cyclosalpa pinnata , Pegea socia , P. confoederata , Salpa cylindrica and S. maxima (Madin & Harbison 1977) . Lycaea ‘bovallioides’ has also been recorded with the pteropod Corolla spectabilis (Harbison et al. 1977) .

Lycaea appears to be widespread in tropical and temperate regions of the world’s oceans. Because of the confused taxonomy of species it is difficult to determine depth ranges for species, but most seem to be epipelagic in habit.

Figures

FIGURE 18. Lycaea pulex Marion, 1874, male (9.0 mm), Tasman Sea, SAMA C 5282. Scale bars = 1.0 mm (A), 0.5 mm (remainder).

FIGURE 19. Lycaea pulex Marion, 1874, male (9.0 mm), Tasman Sea, SAMA C 5282. Scale bar = 0.5 mm.

FIGURE 20. Lycaea pulex Marion, 1874, female (8.2 mm) and male (9.0 mm), Tasman Sea, SAMA C 5281 & C 5282. Mouthparts from male. Scale bars = 0.5 mm (A 2 - m), 0.2 mm (remainder).