Ganigamoera, Sidorov, Dmitry A., 2010

Sidorov, Dmitry A., 2010, A new subgenus of eusirid amphipod (Crustacea: Amphipoda: Eusiridae) from subterranean waters and springs of the Eastern Sikhote-Alin Mountain Ridge, with comments on the morphology of sternal humps, genital papillae and pleopods, Zootaxa 2518, pp. 1-31 : 3-5

Ganigamoera subgen. nov.

Type species. Paramoera (Ganigamoera) myslenkovi sp. nov. (by original designation).

Diagnosis. Closely allied with Paramoera sensu Staude (see Staude 1995, p. 63) but with the following characteristic features: dorsal surface of body segments smooth, urosomite 1 saddle-shaped; ventral surface of pereonites 2–7 with sternal humps (blisters); sternal gills absent; small coxal gill 7 present in both sexes; females with large oostegites on pereopods 2–4 and a smaller strap-like oostegite on pereopod 5; males with genital papillae on ventral surface of pereonite 7.

Rostrum vestigial; lateral cephalic lobe mammilliform; inferior antennal sinus moderate without cleft; eyes reduced or absent; antenna 1 longer than antenna 2, accessory flagellum 1-articulate, scale-like with 3–4 apical setae; gland cone of antenna 2 with short or long setae; calceoli of pontogeneiid type (see Lincoln & Hurley 1981) present in male antennae. Mandible with a little knob at the base of the palp, molar triturative, lacinia mobilis trifurcate, palp articles 2 and 3 of equal length; inner plate of maxilla 1 with 8–9 plumose setae, outer plate with 10 pectinate robust setae; inner plate of maxilla 2 with oblique row of 5–6 plumose setae; inner plate of maxilliped with 2 strong apical peg setae, outer plate with a row of 6–7 medial robust setae, article 3 of maxilliped palp armed with a several simple setae on disto-medial face, dactylus with stiff setae along inner margin.

Coxae 1–3 deep, coxa 4 sub-quadrate with posterior lobe, excavate, anterior lobe of coxa 6 smaller than posterior ones, coxae 1–7 with short setae on ventral margins. Gnathopods feeble; gnathopod 2 larger than gnathopod 1 in both sexes; carpus of gnathopod 2 longer than propodus in both sexes; propodi of both gnathopos sub-rectangular and sub-linear, palm slightly oblique in females; defining angle with less than 8 notched setae. Pereopods 5 and 6 shorter than pereopod 7; bases of pereopods 5–7 broad with densely serrated posterior margins; distoposterior lobe of pereopod 7 base indistinct; carpus as long as or shorter than propodus of pereopods 5–7; dactyli of pereopods 3–7 smooth with 2 minute setae in base of nail.

Pleopods ordinary in general construction, with blunt processes located on inner face of first articles of outer rami for both sexes; pleopod 2 gonopodous in male. Posterior corner of epimera 2–3 acutely produced; ventral margin of epimera 1–2 unarmed. Outer rami of uropods 1–2 slightly shorter than inner rami; peduncle of uropod 3 with small peduncular process, outer ramus slightly shorter than inner ramus, rami narrow, lanceolate, fringed with plumose or simple setae. Lobes of telson fused for less than half of length, tips of lobes notched, with 1 or 2 setae apically.

Discussion of affinities. The morphological comparison of Ganigamoera subgen. nov. with other related North Pacific representatives (see Tables 1, 2) suggests significant mosaicity of some characteristics within the proposed groups. Several characteristics are, however, recognized as constant: the shape of the inferior antennal sinus of the head, the presence of sternal gills or humps, the placement of calceoli and armament on the outer plate of maxilla 1 and the inner plate of the maxilliped, the shape of gnathopods and the armament of the defining angle of palms.

The most interesting classification question involves the subterranean genus Relictomoera . Ganigamoera subgen. nov. differs significantly from Relictomoera because the anterolateral margin of the head is more like those on Paramoera and Sternomoera . However, the peculiar cephalic anterolateral margin of Relictomoera (“unusually sinusoid” by definition of Barnard & Karaman 1982) raises some questions. Hirayama (1990) examined Ueno’s type specimens on Relictomoera and observed that both species R. relicta (Ueno, 1971) and R. tsushimana (Ueno, 1971) have cephalic lobes typically observed in members of Paramoera . Because of this similarity, he proposed restoring them to their former genus (see Hirayama, 1990, p. 959). To determine a clear relationship between Relictomoera and Ganigamoera subgen. nov., taxonomical reassessment of the former is required (for more details, see Table 2).

Ganigamoera subgen. nov. differs from Sternomoera Barnard & Karaman, 1982 , in the absence of sternal gills. It differs from grade Paramoera sensu Staude (1995) in its smaller eyes and lack of cleft in the inferior antennal sinus. The following differences were observed between Hawaiian Moanamoera Staude, 1995, and Ganigamoera subgen. nov.: the antennae extend equally; there are a few setae on the outer plate of maxilla 1; the shorter article 3 of the mandibular palp and its characteristic armament is different; and the bases of pereopods 5–7 are very broad, and their posterior margins extend significantly (for more details, see Barnard 1977). Ganigamoera subgen. nov. differs from Humilomoera Staude, 1995, in the greater setosity of the inner plates of both maxillae, the presence of coxal gill 7 and the notched tips of the telson lobes.

Ganigamoera subgen. nov. is more incongruent with Rhithromoera Staude, 1995, and the latter has more similarities with grade Paramoera (s. l.) than with the other two designated by the Staude subgenera. There are several significant features that are shared: the palp article 3 of the mandible is as long as article 2; the gnathopods are robust; the carpus is shorter than the propodus in female gnathopod 2; the propodi of gnathopods are moderate, and the palm is distinctly oblique; the gnathopods have 8 or more setae at a defining angle; the epimera 1 through 3 have shallow crenulation; and the tips of the telson lobes are complete. There is also a similarity in article 3 of the maxilliped palp of P. (P.) bousfieldi Staude, 1995 , P. (P.) suchaneki Staude, 1995 , and P. (R.) bucki Staude, 1995 , in that they are armed with 2–5 robust comb-like setae on the distomedial face. The presence of a “small irregular bump at the anterior margin of pereonite 1 for P. (R.) carlottensis Bousfield, 1958 (see Staude 1995, p. 91), is interesting but is likely an artefact because it was only observed once in the holotype.

Some features are unique to Ganigamoera subgen. nov. and are not found in the Far Eastern and the Eastern North Pacific groups of Paramoera , Sternomoera and Relictomoera . They are: the presence of humps; the much longer carpus of female gnathopod 2; and the presence of 2 strong peg setae on the inner plate of maxilliped (though this feature was reported previously for P. erimoensis and Awacaris ).

The affinity between Ganigamoera subgen. nov. and the far eastern Paramoera species is discussed at the section Taxonomic comments of described species (see also Table 1).

Remarks. Ganigamoera subgen. nov. is probably not monophyletic and apparently presented by the freshwater stygomorphic derivatives of heterogeneous lineages of marine or brackish water species of Paramoera . The following differences of a new species support this conclusion: the characteristics of the armament of the peduncular articles of the antennae; the shape of upper lip and body of mandibles; the furnishing of uropod 3; and the length of the telson (for more details, see Table 1).

Species and distribution. P. (G.) myslenkovi sp. nov. and P. (G.) tiunovi sp. nov. inhabit subterranean waters and springs in the basins of two rivers located near each other on the eastern slope of the Sikhote-Alin Mountain Ridge, Far East (see Fig. 1 ).

Etymology. The subgeneric name Ganigamoera derived from the combination of the Udehe word ganiga (a mythical creature living in the water) and moera (the same root of related genera).

Figures

FIGURE 1. Map-scheme indicating collection sites in the South Primory.