Amblyops G. O. Sars, 1872

Murano, Masaaki, 2012, The Genus Amblyops (Crustacea: Mysida: Mysidae: Erythropinae) from East Asia and Australia, with Descriptions of Ten New Species, Species Diversity 17 (1), pp. 49-85 : 50-51

Genus Amblyops G. O. Sars, 1872

Amblyopsis G. O. Sars, 1869: 328 .

Amblyops G. O. Sars, 1872: 3 ; Banner 1948: 382; Tattersall and Tattersall 1951: 246–247; O. S. Tattersall 1955: 103– 104; Ii 1964: 271–272; O. S. Tattersall 1965: 14–15; Kathman et al. 1986: 95.

Diagnosis.C arapace broadly and evenly rounded anteriorly, without de nite rostral projection.

Eyes in form of completely separated immovable plates without visual elements; each plate with or without papilliform projection on anterodorsal margin; anterior and lateral margins without serrulation, but margins and dorsal surface with ne spinules.

Antennular peduncle short and robust; third segment in female with setae along inner margin. Appendix masculina on third segment large and very hirsute.

Antennal scale long, overreaching distal margin of antennular peduncle by 1/3 to 1/2 of its length; distolateral denticle stout, extending to apex of blade and provided with one or more small subsidiary spinules near basal end of inner side; suture marking o small distal joint. Antennal peduncle composed of 4 segments; second segment connected to ventral side of third segment. Antennal sympod with 1 noticeable denticle at distolateral corner.

Endopods of third to eighth thoracopods with carpopropodus divided into 3 subsegments; articulation between proximal 2 subsegments very oblique.

Female with 3 pairs of oostegites on sixth to eighth pairs of thoracopods, those on sixth thoracopods rudimentary.

Genital organ of male with 2 to 7 hooked setae on apex.

Male sometimes with single sternal process between pair of genital organs.

Pleopods of male well developed, biramous and natatory;

rst pair with unsegmented endopod and multi-segmented exopod; fourth pair usually armed with modi ed setae on distal several segments of both rami; pseudobranchial lobe broadened.

Uropodal endopod tapering, usually slightly longer than telson, with one or more spines on inner ventral margin in statocyst region. Uropodal exopod much longer than endopod.

Telson linguiform or trapezoidal; margin armed with spines on posterior half to entire length, these spines usually increasing in length posteriorly; posterior end sometimes armed with 1 or 2 small spines between longer ones; apical pair of plumose setae usually present.

Type species. A mblyops abbreviatus (G. O. Sars, 1869) , present selection.

Remarks.N o type species of the genus Amblyops has been formally designated in previous literature, and therefore, Amblyops abbreviatus is selected herein as the type species of Amblyops .

fflere has been much confusion in the attribution of the author of the name Amblyops abbreviatus in previous literature. For example, G. O. Sars (1869) was attributed to this name by Holt and Tattersall (1905, 1906), Tattersall (1911, 1951), Banner (1954), Mauchline and Murano (1977), Kathman et al. (1986), and Müller (1993), but while M. Sars (1869) was attributed to it by Zimmer (1909), Banner (1948), Tattersall and Tattersall (1951), Gordan (1957), Birstein and Tchindonova (1958), Ii (1964), Price (2004), Fukuoka (2009), and Anderson (2010).

In fact, G. O. Sars (1869) established Amblyopsis with Pseudomma abbreviatum cited by M. Sars (1869) in a list of deep-sea organisms. However, the name P. abbreviatum of M. Sars (1869) is a nomen nudum without doubt, because any description was not provided by M. Sars (1869). G. O. Sars (1869) is the rst who presented a formal description of Amblyops abbreviatus (as Amblyopsis ) based on one specimen listed in M. Sars (1869) and additional one, and consequently, the author of the name Amblyops abbreviatus should be attributed to G. O. Sars (1869).

ffle genus Amblyops is readily distinguished from allied genera, such as Pseudomma , Paramblyops Holt and Tattersall, 1905 , Amblyopsoides O. S. Tattersall, 1955 , Scolamblyops Murano, 1974 , Parapseudomma Nouvel and Lagardère, 1976 , and Neoamblyops Fukuoka, 2009 , in having the eyes reduced to immovable, completely separated plates without visual elements, an evenly rounded anterior margin of the carapace, the distolateral spine of the antennal scale extending to the apex of the blade and possessing one or more subsidiary spinules on the inner side, the antennal peduncle having the second segment connected to the ventral side of the third segment, and the genital organ of the male being armed with two to seven hooked setae on the apex.

An Irish species, A. tenuicaudus , seems to belong to a different genus than Amblyops because it di ers from almost all the other species of the genus in having a nger-like projection on the dorsal surface of the eyeplates near the mid-line, a distolateral antennal-scale spine extending beyond the apex of the blade for its entire length, and a telson with an acute posterior end bearing a pair of plumose setae. However, a de nitive conclusion on this point will require future study.

ffle species of Amblyops live at considerabe depths, as a result the collection records are limited and specimens collected are more or less damaged during the collection. fflus, the morphology of almost all species is not satisfactorily known; especially, aspects of the genital organ and the fourth pleopod of mature males remain unclear. In this study, a sternal process was found between the eighth thoracopods in males. In future investigations, researchers should pay special attention to the shape and armature of this organ because it may prove to be a useful taxonomic feature.