Procrangonyx japonicus ( Uéno, 1930 )

Nakano, Takafumi, Tomikawa, Ko & Grygier, Mark J., 2018, Rediscovered syntypes of Procrangonyx japonicus, with nomenclatural consideration of some crangonyctoidean subterranean amphipods (Crustacea: Amphipoda: Allocrangonyctidae, Niphargidae, Pseudocrangonyctidae), Zootaxa 4532 (1) : -

Procrangonyx japonicus ( Uéno, 1930)

( Figs 1 , 2 )

Eucrangonyx japonicus Uéno, 1930: 21 –23, fig. 1.

Eocrangonyx japonicus .— Tomikawa & Shinoda, 2016: 585 –593, figs. 2–6.

Material examined. Syntypes. KUZ Z1759 , two individuals, collected from underground water in Tokyo, Japan, on 26 January 1930 ( Uéno 1930; Fig. 1 ); these two specimens, upon which the original description of the species was based, are automatically fixed as syntypes under Article 73.2 of the Code .

Redescription of uropod 3. Left uropod 3 of one individual still discernable. Inner ramus absent; outer ramus uniarticulate, with two long, robust setae and seven short, simple, slender setae ( Fig. 2 ).

Remarks. It was hard to observe the detailed morphological characteristics of the syntypes due to their poor condition. The preservative solution of the specimens appears to have dried up, whereupon the amphipods became flattened against the bottom of the glass tube and were damaged ( Figs 1A , 2A ). However, the left uropod 3 of one of them was sufficiently well preserved to confirm that its outer ramus comprises only a single article. Therefore, Uéno’s (1930) original description of uropod 3 was correct. This means that P. japonicus is variable in this respect, the outer ramus being either uniarticulate (present syntype) or biarticulate ( Tomikawa & Shinoda 2016). Molecular phylogenetic analysis has shown that Procrangonyx primoryensis Stock & Jo, 1990 is a member of a monophyletic lineage consisting otherwise only of Pseudocrangonyx species (Tomikawa et al. 2016). It is clear that Procrangonyx and Pseudocrangonyx are phylogenetically close, and Procrangonyx , despite its being nomenclaturally available as demonstrated above, could potentially be reduced to an invalid junior synonym of Pseudocrangonyx , as previous studies have implied ( Sidorov & Holsinger 2007; Tomikawa & Shinoda 2016). In this context, a molecular phylogenetic study of the relations of Procrangonyx japonicus is a necessary future step.

Figures

FIGURE 1. Procrangonyx japonicus (Uéno), syntypes, KUZ Z1759. (A) Photograph showing two individuals. (B) Historical handwritten label. Scale bar, 5 mm.

FIGURE 2. Procrangonyx japonicus (Uéno), syntype, KUZ Z1759. (A) Photograph of left uropods 1–3 of one of the syntypes, lateral view. (B) Photograph of the terminal part of left uropod 3, lateral view. (C) Line drawing of the terminal part of uropod 3, lateral view. Scale bars, 0.5 mm (A), 0.1 mm (B, C).