Nanosaphes Giron & Short, 2018

Giron, Jennifer C. & Short, Andrew Edward Z., 2021, The Acidocerinae (Coleoptera, Hydrophilidae): taxonomy, classification, and catalog of species, ZooKeys 1045, pp. 1-236 : 1

Genus Nanosaphes Giron & Short, 2018 Figs 1L , 2 , 40E-H , 41

Nanosaphes Girón & Short, 2018: 143.

Gender.

Masculine.

Type species.

Nanosaphes tricolor Girón & Short, 2018: 151; by original designation.

Diagnosis.

Very small beetles, body length 1.15-1.45 mm. Body shape oval in dorsal view; slightly to moderately, and evenly convex in lateral view (Fig. 41 ). Coloration uniformly brown, to variable along the body; ground punctation shallow to moderately marked (Fig. 41 ). Shape of head trapezoid and relatively wide. Eyes moderate in size, slightly emarginated anteriorly, not projected from outline of head. Clypeus trapezoid, with anterior margin broadly emarginate. Labrum fully exposed. Mentum with lateral oblique ridges. Antennae with eight antennomeres; cupule slightly asymmetric, with rounded outline. Maxillary palps slender, moderately long nearly 0.7 × the width of head; inner margin of maxillary palpomere 2 nearly straight, outer margin curved along apical half (e.g., Fig. 41C, F ). Each elytron with ground punctures usually only shallowly marked, seemingly forming longitudinal rows, with irregularly distributed systematic punctures bearing rather long setae, denser along lateral and posterior regions; elytra without sutural striae. Prosternum flat, at most only weakly convex. Posterior elevation of mesoventrite, usually projected as low and short longitudinal carina between mesocoxae; anapleural sutures only weakly curved, separated at anterior margin by distance nearly 0.9 × width of anterior margin of mesepisternum. Metaventrite with posterolateral and mesal glabrous patches (e.g., Fig. 41C, F ). Protibiae with spines of anterior row hair-like, semi erect, relatively long, thick and sparse. Metafemora mostly densely covered by hydrofuge pubescence (e.g., Fig. 41C, F ). All tarsomeres with long and thick spines on ventral faces of tarsomeres 2-4; metatarsomeres 2-4 gradually decreasing in size, metatarsomere 5 as long as 3 and 4 combined, 2 slightly shorter. Fifth abdominal ventrite apically emarginate, with fringe of stout setae. Aedeagus trilobed (Fig. 40E-H ), nearly parallel sided, with basal piece 0.3-0.6 × length of parameres; median lobe with well-developed lateral basal apodemes, wider at base than base of each paramere, usually narrower at apex than preapical width of parameres; apex of median lobe rounded; parameres from slightly shorter to longer than median lobe, and only narrowing at apex; gonopore situated beyond midpoint of median lobe.

Differential diagnosis.

The minute size of Nanosaphes make them smaller than any other Acidocerinae in the New World, and about equal in size to the smallest species of Agraphydrus in the Old World. They are among the smallest water scavenger beetles worldwide. The lack of elytral serial or sutural striae and the antennae with eight antennomeres also separate Nanosaphes from all other Neotropical Acidocerinae genera except the co-occurring Globulosis . Nanosaphes can be easily separated from Globulosis by its smaller size and narrower, more parallel sided body form (broader and almost rotund in Globulosis , Fig. 32 ).

Distribution.

Neotropical: Brazil ( Pará), Guyana, Suriname; Fig. 5 .

Natural history.

Species are associated with stream margins, particularly where there are marginal banks of sand and roots.

Larvae.

Immature stages are not known for Nanosaphes .

Taxonomic history.

Nanosaphes was only recently described.

Remarks.

There are four known species of Nanosaphes , which can be differentiated from each other by external morphological features (e.g., elytral punctation, coloration, shape of the posterior elevation of the mesoventrite), which is somewhat unusual by acidocerine standards. We have seen additional material of Nanosaphes from other regions within the Guiana Shield.

Species examined.

Holotypes and paratypes of all known species were available for this study.

Selected references.

Girón and Short 2018: original description of the genus and all its known species; Short et al. 2021: phylogenetic placement.

Figures

Figure 1. Variation across Acidocerinae, dorsal and lateral views A Colossochares ellipticus B Peltochares sp. C Peltochares conspicuus D Aulonochares tubulus E Helochares sp. F Helochares tristis G Novochares sp. H Helopeltarium ferrugineum I Batochares sp. J Helobata larvalis K Radicitus sp. L Nanosaphes tricolor M Agraphydrus cf. attenuatus N Tobochares luteomargo O Tobochares sulcatus P Quadriops similaris Q Crucisternum ouboteri R Primocerus neutrum S Agraphydrus coomani T Agraphydrus sp. U Globulosis flavus V Crephelochares nitescens.

Figure 2. Phylogeny of the Acidocerinae simplified from Short et al. (2021), indicating the distribution, preferred habitat, and currently described number of species for each genus. For habitat, filled black circles indicate that at least some species of the genus are commonly found in this habitat; light grey circles indicate the genus has been found in this habitat, but is rare or not typical for the group; white circles indicate no species have been recorded for the genus in this habitat.

Figure 5. Known distribution of genera of Acidocerinae: Crucisternum, Ephydrolithus, Globulosis, Helobata, Helochares, Helopeltarium, Katasophistes, and Nanosaphes.

Figure 32. Habitus of Globulosis flavus A dorsal habitus B lateral habitus C ventral habitus. Scale bar: 1 mm.

Figure 40. Aedeagi of Katasophistes and Nanosaphes spp. A K. charynae B K. cuzco C K. merida D K. superficialis E N. tricolor F N. hesperus G N. castaneus H N. punctatus. Scale bars: 0.3 mm (A-C); 0.1 mm (E-H).

Figure 41. Habitus of Nanosaphes spp. A-C N. tricolor: A dorsal habitus B lateral habitus C ventral habitus D-F N. punctatus: D dorsal habitus E lateral habitus F ventral habitus. Scale bars: 0.5 mm.