Peltochares Regimbart , 1907

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 Peltochares Regimbart, 1907 Figs 1B, C , 4 , 11K , 44 , 45

Peltochares Régimbart, 1907: 49.

Peltochares conspicuus Type species. Peltochares conspicuus Régimbart, 1907: 49; by monotypy.

Stagnicola Montrouzier, 1860: 246 [preoccupied name by Stagnicola Gray, 1840 ( Mollusca)]

Stagnicola foveicollis Type species: Stagnicola foveicollis Montrouzier, 1860: 246; by monotypy; Bedel 1880: CXLVIII [synonymy].

Neohydrobius Blackburn, 1898: 221.

Philhydrus burrundiensis Type species: Philhydrus burrundiensis Blackburn, 1890: 447; by monotypy; d’Orchymont 1919b: 228 [synonymy].

Helochares "Clade C" in Short et al. 2021.

Gender.

Masculine.

Type species.

Peltochares conspicuus Régimbart, 1907: 49; by monotypy.

Diagnosis.

Body length 6-14 mm. Body shape oval in dorsal view, weakly to moderately convex in lateral view (Fig. 44 ). Dorsal surfaces even and smooth, either uniformly covered by short setae (Fig. 44A ), or with scarce long setae along particular areas of surface (associated with systematic punctures; Fig. 44D ), dark brown in coloration, usually uniform; ground punctation fine and shallow to moderate; ventral surfaces densely covered by fine golden setae (Fig. 44C, F ). Head subquadrate (Fig. 11K ). Eyes not emarginate, moderate in size, subquadrate, separated by 4.5-5.5 × width of eye, strongly projected from outline of head. Clypeus with anterior margin broadly emarginate, either roundly or acutely, sometimes further medially notched; membranous preclypeal area visible when clypeus strongly emarginated. Labrum fully exposed, often medially convex. Antennae with nine antennomeres, with moderately asymmetric and round cupule; antennomere 9 slightly to 2 × longer than antennomere 7. Maxillary palps slender, 1.3-1.8 × longer than maximum width of head, with palpomere 4 nearly 0.8 × as long as palpomere 3; maxillary palpomere 2 with inner margin slightly and evenly curved, and outer margin curved along apical half (Fig. 44C, F ). Mentum slightly depressed mesally, surface laterally punctate, mesally and anteriorly striate, with anteromedial region depressed (Fig. 44C, F ). Submentum punctate to crenulate. Pronotum evenly convex, usually with systematic punctures forming distinct anterolateral semicircles. Elytra without sutural striae, with margins usually only slightly flared (explanate in P. conspicuus ; Fig. 44A ); serial punctures usually absent (visible along entire length of elytra in P. conspicuus ; Fig. 44A ); ground punctation usually shallow (moderate to strongly marked in P. foveicollis ). Surface of prosternum flat to broadly convex, with anterior margin roundly projected anteriorly (Fig. 44C, F ). Posterior elevation of mesoventrite usually with longitudinal or somewhat longitudinal elevation, sometimes forming acute posterior point; apical region of elevation usually with long fine setae; anapleural sutures forming obtuse angle, nearly parallel along anterior section, separated anteriorly by distance 0.3-0.7 × anterior margin of mesepisternum. Metaventrite densely covered by hydrofuge pubescence, except for posterolateral patches (Fig. 44C, F ). Protibiae with anterior row of spines reduced to extremely reduced (Fig. 44C ); apical spurs of protibiae stout, ranging from very large (larger spur considerably larger and thicker than tarsal claws, e.g., P. foveicollis ), or very short (barely reaching apex of protarsomere 1, e.g., P. conspicuus ); pro- and mesotarsal claws are sexually dimorphic in some species (e.g., P. foveicollis ). Metafemora with tibial grooves sharply marked; metafemora with hydrofuge pubescence covering at least basal 3/4 of anterior surface (Fig. 44C, F ). Metatarsomeres 5 and 2 similar in length or 2 slightly longer, metatarsomere 2 slightly longer than metatarsomeres 3 and 4 combined; all tarsomeres with ventral surface rather densely covered by long spiniform setae on ventral surface (sparser on tarsomere 5). Abdomen with five pubescent ventrites. Fifth abdominal ventrite with apex emarginate, fringed by stout setae. Aedeagus spiked (Figs 16C, D , 45 ); main component of median lobe strongly sclerotized, slender, and apically acute, usually accompanied by additional shorter slender sclerotizations; apical region of parameres usually partly heavily sclerotized and partly membranous, often bifurcated; basal piece strongly reduced; gonopore usually not clearly visible.

Differential diagnosis.

The type species of Peltochares is easily recognized by its external morphology alone: laterally explanate pronotum and elytra, well defined serial punctures along elytra (Fig. 44A ), which somewhat resembles Helobata (Fig. 33A ), from which P. conspicuus can be distinguished by the exposed labrum of Peltochares (Fig. 11K ; concealed labrum in Helobata , Fig. 11L ). The most common forms of Peltochares more closely resemble Novochares and some Helochares , because of their darkly colored and highly polished dorsal habitus. Besides being distributed (although widespread) in the Old World, Peltochares species can be distinguished from the New World Novochares by the shape of the posterior elevation of the mesoventrite (longitudinally elevated in Peltochares , simply and broadly bulging, often with additional anterior low longitudinal ridge in Novochares ), in addition to characteristics of the male genitalia (spiked aedeagus in Peltochares , Figs 16C, D , 45 ; divided aedeagus in Novochares , Figs 16G, H , 43 ; see also explanation under the aedeagus section of Morphological variation in Acidocerinae and its taxonomic importance). From dark brown, highly polished, and relatively large species of Helochares , Peltochares can be distinguished by their slender maxillary palps, that are 1.3-1.8 × longer than the width of the head (Fig. 44C, F ), as opposed to shorter (0.6-1.2 × the width of the head) and relatively stout maxillary palps in Helochares (Figs 35C, F , 36C, F ), in addition to the aedeagal form (spiked in Peltochares , Figs 16C, D , 45 ; tubular in Helochares , Figs 16E, F , 37A-H ; see also explanation under the aedeagus section of Morphological variation in Acidocerinae and its taxonomic importance).

Distribution.

Afrotropical: Angola, Benin, Botswana, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Democratic Republic of the Congo, Ethiopia, Gabon, Gambia, Ghana, Guinea, Ivory Coast, Kenya, Liberia, Madagascar, Malawi, Mozambique, Namibia, Niger, Nigeria, Republic of the Congo, Rwanda, Senegal, Sierra Leone, Somalia, Republic of South Africa, South Sudan, Tanzania, Togo, Uganda, Western Sahara, Zambia, Zimbabwe. Australasian: Australia (Australian Capital Territory, New South Wales, Northern Territory, Queensland, Western Australia), Indonesia (Papua), New Caledonia, Papua New Guinea. Indo-Malayan: Bangladesh, Cambodia, China (Guangdong, Guangxi, Guizhou, Hong Kong, Jiangxi, Macao), Indonesia (Borneo, Sumatra), Laos, Malaysia, Nepal, Sri Lanka, Thailand, Vietnam. Palearctic: Canary Islands, Egypt, Israel, Japan (Nansei Islands); Fig. 6 .

Natural history.

Even though species currently placed in Peltochares have been treated in faunistic and taxonomic studies (e.g., Watts 1995, Hebauer 2001b), little is known about their ecology. Jia and Tang (2018) recently reported that P. atropiceus ( Régimbart) was living in natural ponds with leaf litter or water grass, sometimes collected on wet ground with plenty of grass; it can be collected at light in May and June in South China and has never been collected from the edges of rivers and streams. The female carries the egg case under the abdominal ventrites (Jia and Tang 2018).

Larvae.

Larval stages of Peltochares conspicuus Régimbart, were described by Bertrand (1962) from larvae collected along with adults on the surface of rocks in Madagascar. Fikáček (2003) provides a diagnosis of the larvae described by Bertrand (1962), but questions their identification, given that P. conspicuus has never been recorded from Madagascar. It seems most probable the description is of another species now placed Peltochares , as P. longipalpis has been recorded from Madagascar, but only future rearing or DNA sequencing of putative larvae will confirm this.

Lectotype designation.

We examined Régimbart’s syntype series for Peltochares conspicuous , consisting of nine specimens, that are deposited in the Muséum national d’Histoire naturelle, Paris, France. We determined all nine to be conspecific. It includes two specimens labeled 'Cape Lopez’, one of them labeled ' Peltochares conspicuus Rég.’; five specimens labeled Rembo N’Comi Fernand Vaz, one of them missing prothorax and head, and another one is missing the left elytron; one specimen labeled Rembo N’Comi Fernand Vaz (Gabon), missing prothorax and head; and one specimen labeled ‘Gabon’. All specimens, except the last one, are pinned; the specimen labeled ‘Gabon’ is glued by its abdomen in a small pinned card. To stabilize the identity of the type species of Peltochares , we here designate as the Lectotype the specimen that bears the ' Peltochares conspicuus Rég.’ label, which even though is not completely clean, has all its appendages complete. The following red label has been attached: "LECTOTYPE/ Peltochares / Peltochares conspicuus / Régimbart / des. Girón and Short". The remaining eight specimens are designated as paralectotypes. One of the specimens missing its prothorax and head was dissected to reveal the male genitalia, which is illustrated in Fig. 45A .

Taxonomic history.

The circumscription of Peltochares as used here is changed from its original meaning. Peltochares was originally described as a monotypic genus by Régimbart in 1907, from specimens collected in Gabon of a very unusual species ( P. conspicuus ) which was a rather large, circular beetle with extremely explanate margins of the pronotum and elytra (Fig. 44A-C ). A morphologically similar species was much later described from Indonesia and Malaysia, although that species was placed in the nominal subgenus of Helochares ( Helochares (s. str.) Helochares discus Hebauer, Hendrich & Balke). In their molecular phylogeny, Short et al. (2021) recovered H. discus in a clade ( Helochares Clade C) with some other larger, darkly colored (but not explanate) Old World species that were also placed in Helochares (s. str.), which showed that this clade was not closely related to the “true” Helochares but indeed represented an independent lineage. Examination of the male genitalia of one of the syntypes of P. conspicuus (the type of Pelotochares ) and members of " Helochares Clade C" in Short et al. (2021) revealed that they share a quite unique and similar configuration of the male genitalia (spiked genitalia, Figs 16C, D , 45 ; see also the aedeagus section of Morphological variation in Acidocerinae and its taxonomic importance above), even though they do not share the same extremely explanate body form.

Although the monophyly and morphological circumscription of " Helochares Clade C" is strongly supported, the proper genus name to assign to his lineage is not straightforward, as there are several generic names that had been long synonymized with Helochares that potentially come into play with the new circumscription of the genus. The genus Stagnicola Montrouzier, 1860 was based on what is now Helochares (s. str.) Helochares foevicollis , a species which is a definitive member of Helochares Clade C. However, Stagnicola is a preoccupied name and thus unavailable. More complicated is Neohydrobius Blackburn, 1898 and its type species, Philhydrus burrundiensis Blackburn, which is now considered a junior synonym of H. (s. str.) foevicollis . Neohydrobius , although eight years older than Peltochares , had a very short shelf-life, as it was synonymized with Helochares just 21 years after it was proposed by d’Orchymont (1919b) and therefore has not been used in more than a century. Meanwhile, Peltochares has been in continuous usage since 1907 and therefore we believe it is the best and most stable name to apply to this clade.

We had hoped to unilaterally maintain prevailing usage of Peltochares over Neohydrobius by invoking ICZN Article 23.9.1. However, not all the required criteria to apply this article appear to be met in this case. Although Neohydrobius appears to meet the first criterion (the senior synonym not being used as valid since 1899), we were only able to identify 19 works (by more than 10 authors) in the immediately preceding 50 years, but 25 works are required. Therefore, we will formally appeal to the commission for a ruling to maintain Peltochares over Neohydrobius . Accordingly, ICZN Article 82.1 states that prevailing usage is to be maintained until the ruling of the Commission is published and therefore, we use Peltochares in this work.

Remarks.

The group of species previously assigned to Helochares (s. str.), hereby transferred to Peltochares , was first recognized by Hebauer (2001b) as a discrete unit in morphological terms within Helochares . There are currently eight described species of Peltochares , including the following seven species that are transferred from Helochares for the first time: P. atropiceus ( Régimbart) comb. nov., P. ciniensis (Hebauer, Hendrich & Balke) comb. nov., P. discus (Hebauer, Hendrich & Balke) comb. nov., P. foveicollis (Montrouzier) comb. nov., P. longipalpis (Murray) comb. nov., P. papuensis (Hebauer) comb. nov., and P. taprobanicus (Sharp) comb. nov.

Species examined.

Peltochares atropiceus , P. ciniensis (including a paratype), P. conspicuus (including syntypes), P. foveicollis , P. longipalpis , and P. taprobanicus .

Selected references.

Régimbart 1907: 49: original description of the genus; Hebauer 2001b: taxonomic treatment of P. taprobanicus (as Helochares taprobanicus ) and allied species; Jia and Tang 2018: faunistic review of Chinese species including a redescription and some biological notes on P. atropiceus ; 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 4. Known distribution of genera of Acidocerinae: Acidocerus, Agraphydrus, Aulonochares, Batochares, Chasmogenus, Colossochares, and Crephelochares.

Figure 6. Known distribution of genera of Acidocerinae: Novochares, Peltochares, Primocerus, Quadriops, Radicitus, Sindolus, Tobochares, and Troglochares.

Figure 11. Head of miscellaneous Acidocerinae A-D anterolateral view: A Tobochares luteomargo with white arrow pointing to straight anterior margin of eye B Tobochares emarginatus with white arrow pointing to Tobochares canthus emarginating anterior margin of eye C Quadriops politus with white arrow pointing to Tobochares canthus fully dividing the eye in dorsal and ventral faces D Batochares sp. black arrow pointing to transverse carina on labrum E-L dorsal view of head: E Batochares sp. F Helochares tristis G Crephelochares nitescens, H Chasmogenus australis with black arrow pointing to preclypeal membrane I Colossochares ellipticus J Aulonochares tubulus K Peltochares conspicuus L Helobata larvalis.

Figure 16. Aedeagi A-E trilobed: A schematic B Chasmogenus schmits C, D spiked: C schematic D Peltochares foveicollis E, F tubular: E schematic F Helochares politus G, H divided: G schematic H Novochares pallipes.

FIgure 33. Habitus of Helobata spp. A-C H. larvalis: A dorsal habitus B lateral habitus C ventral habitus D H. quatipuru (from Clarkson and Almeida 2018) E H. amazonensis (from Clarkson and Almeida 2018) F H. pantaneira (from Clarkson et al. 2016). Scale bars: 1 mm.

Figure 35. Habitus of Helochares spp. A-C Helochares tristis: A dorsal habitus B lateral habitus C ventral habitus D-F H. sharpi: D dorsal habitus E lateral habitus F ventral habitus. Scale bar: 1 mm.

Figure 36. Habitus of Helochares spp. A-C H. laevis: A dorsal habitus B lateral habitus C ventral habitus D-F H. sp. (India, Goa): D dorsal habitus E lateral habitus F ventral habitus. Scale bar: 1 mm.

Figure 37. Aedeagi A-H Helochares spp.: A H. sp. (Guinea) B H. tristis C H. nr. cresphontes D H. nr. tatei E H. sp. (India, Goa) F H. sp. (Vietnam) G H. politus H H. songi (from Jia and Tang 2018, fig. 48) I Helopeltarium ferrugineum. Scale bars: 0.5 mm.

Figure 43. Aedeagi of Novochares spp. A N. sp. (Ecuador) B N. abbreviatus C N. pallipes D N. chaquensis E N. atratus F N. pichilingue G N. cf. tectiformis H N. cf. coya I N. cf. guadelupensis J N. cf. cochlearis. Scale bars: 0.5 mm.

Figure 44. Habitus of Peltochares spp. A-C P. conspicuus: A dorsal habitus B lateral habitus C ventral habitus D-F P. sp. (Tanzania): D dorsal habitus E lateral habitus F ventral habitus. Scale bars: 1 mm.

Figure 45. Aedeagi of Peltochares spp. A P. conspicuus B P. foveicollis C P. sp. (Australia) D P. sp. (Tanzania;). Scale bars: 1 mm.