Redescriptions and lectotype designations of Central American species of Phaenonotum Sharp (Coleoptera, Hydrophilidae) based on the type material from the David Sharp collection

Abstract In order to understand the identity of the Central American species of the genus Phaenonotum Sharp, 1882, the type specimens of the species described by Sharp (1882) deposited in the David Sharp collection in the Natural History Museum in London have been re-examined. The following species are redescribed: Phaenonotum apicale Sharp, 1882, Phaenonotum collare Sharp, 1882, Phaenonotum dubium Sharp, 1882 (confirmed as junior synonym of Phaenonotum exstriatum (Say, 1835)), Phaenonotum laevicolle Sharp, 1882, Phaenonotum rotundulum Sharp, 1882 and Phaenonotum tarsale Sharp, 1882. Lectotypes are designated for Phaenonotum apicale, Phaenonotum collare, Phaenonotum rotundulum and Phaenonotum tarsale. External diagnostic characters and morphology of male genitalia are illustrated. A table summarizing diagnostic characters allowing the identification of the species is provided.


Introduction
The genus Phaenonotum Sharp, 1882 was described by the British specialist on water beetles, David Sharp, in his treatment of the Central American hydrophilid fauna in the famous Biologia Centrali-Americana. Based on material from Mexico, Nicaragua, Guatemala, Costa Rica and Panama available to him, Sharp (1882) recognized and described six species of that genus, and also recognized that the North American species Cyclonotum exstriatum (Say, 1835) is congeneric. A few other species originally described in other genera were later assigned to Phaenonotum by other authors (Knisch 1924;Orchymont 1937) and few additional species were described subsequently from Brazil (Orchymont 1937(Orchymont , 1943, Argentina (Bruch 1915), Venezuela (Archangelsky 1989), U.S.A (Smetana 1978) and Cuba (Deler-Hernández et al. 2013). In addition, the monotypic genus Hydroglobus Knisch, 1921 from Argentina was considered a part of Phaenonotum by Archangelsky (1991), but this was not followed by subsequent authors (see e.g. Clarkson et al. 2014 for diagnostic characters between Hydroglobus and Phaenonotum). At present, Phaenonotum seems to occur exclusively in the Neotropical and southern Nearctic Region from where 18 species are described (Hansen 1999;Deler-Hernández et al. 2013). The identity of the only non-American species, P. africanum Régimbart, 1907 from the island of Bioko in Guinean Gulf, Africa, is unclear and the species needs to be re-examined.
Despite being frequently collected, Phaenonotum species were never properly revised, and only the fauna of North America and Argentina (partly) were treated in details by modern authors (Smetana 1978;Archangelsky 1991). Hence, no information on morphology of the species or identity of their types was published for the majority of species after their original descriptions, which makes the identification of newly collected material almost impossible. The only species for which types were reexamined and redescriptions and/or illustrations published are P. argentinense Bruch, 1915, P. regimbarti Bruch, 1915, and P. exstriatum (Say, 1835 and its synonyms (Smetana 1978;Archangelsky 1991). In addition, the lectotype of P. laevicolle Sharp, 1882 was designated by Smetana (1976), but without providing any information about the identity of that species. Of the recently described species, photos of the habitus and genitalia, and some details on morphology of P. minor Smetana, 1978were published by Deler-Hernández et al. (2013. The assignment of P. caribense Archangelsky, 1989 to Phaenonotum was found questionable based on preliminary molecular data (A. Deler-Hernández & V. Sýkora, unpubl. data).
In the course of the review of Phaenonotum from the Greater Antilles, it was necessary to study the identities of the Central American species of the genus described by D. Sharp in order to confirm or exclude their occurrence in the Caribbean islands. The type series of all species described by Sharp and deposited in the Natural History Museum in London were therefore re-examined. To facilitate future studies, the results of these studies are summarized in the present paper, providing the redescriptions and illustrations of the species examined. In needed cases, the lectotypes have been designated in order to fix the identity of the species for future studies.

Material and methods
Habitus photographs were taken using Canon EOS 550D digital camera with attached Canon MP-E65mm f/2.8 1-5× macro lens, and subsequently adapted in Adobe Photoshop CS5. Drawings of male genitalia are based on photographs taken using Canon EOS 1100D digital camera attached to Olympus BX41 compound microscope and subsequently combined in Helicon Focus software. Scanning electron micrographs of lectotypes were taken using Hitachi S-3700N environmental electron microscope at the Department of Paleontology, National Museum in Prague, using the uncoated specimens in low vacuum regime. Morphological terminology follows Smetana (1978), Archangelsky (1989Archangelsky ( , 1991 and Deler-Hernández et al. (2013).
Part of the specimens including the lectotypes were dissected, their genitalia were mounted in an alcohol soluble Euparal resin on a small piece of glass attached to the same pin as the specimen.
All lectotypes designated were labeled with the following red label: "Lectotype [or Paralectotype] / Phaenonotum / species-name with author and year of description / des. Deler-Hernández".
Under each species listed as material examined label data are given verbatim between quotes (" "), each line of text is separated by a slash with spaces on both sides (/) and the information of each label is separated by double slashes with space on both sides (//). Other data are in square brackets ([ ] (Fig. 1a), elytra uniformly convex in lateral view (Fig. 2a). Dorsal surface dark brown (Fig. 1a). Antennae and maxillary palpi testaceous. Ventral surface reddish. Leg reddish, tarsomeres yellowish. Head and pronotum with fine and sparse punctures. Elytral punctation strongly impressed, coarser than pronotal and head punctation. Pronotum wider than long and convex. Epipleura very broad throughout. Meso-and metaventral processes fused into a common keel; mesoventral process arrow-head shaped with a distinct hood, as wide as metaventral process basally, metaventral process slender, parallel-sided, length of metaventrite medially (including metaventral process) ca. four times longer than mesoventral process; metathoracic discrimen indistinct (Fig. 3a). Profemora with long sparse pubescence in basal 0.75. Meso-and metafemora with very sparse and short pubescence only. All tarsi with long setae on ventral surface. Aedeagus (Fig. 4a) 0.4 mm long, with median lobe reaching apices of parameres; basal portion of median lobe angulate laterally, apical portion strongly narrowing; shape of the gonopore oval. Parameres wide and curved in median region. Phallobase not examined in detail.
Comments on lectotype designation. Sharp (1882) mentions specimens from two localities: Nicaragua: Chontales and Guatemala: Guatemala City, but without specifying the number of specimens. In the Sharp collection, there are two specimens standing under the name of P. apicale, one from each locality mentioned, and both corresponding with the data in the original description. We hence consider both as syntypes. The specimen from Guatemala City is the only male, and thus is designated here as lectotype, despite it appearing to be slightly teneral. Otherwise, there are four specimens from localities not corresponding to those given in the original description, which we do not consider as a part of the type series (see Other material examined). Type locality (following lectotype designation). Chontales, Nicaragua. Redescription. Habitus as in Figs. 1b and 2b. Body length 3.5-3.9 mm (lectotype: 3.9 mm). Body form oval in dorsal view (Fig. 1b), elytra less convex anteriorly and more convex posteriorly in lateral view (Fig. 2b). Dorsal surface brown (Fig. 1b). Antennae and maxillary palpi testaceous. Ventral surface reddish brown. Leg reddish, tarsomeres yellowish. Head with coarse and strongly impressed punctures. Pronotum with fine punctures, but sparser than head punctation. Elytral punctation (Fig. 1b) strongly impressed, punctures of the same size as on head and as coarse as head punctations. Epipleura very broad throughout. Meso-and metaventral processes slender and fused into a common keel; mesoventral process arrow-head shaped with an distinct hood, slightly wider than apex of metaventral process basally, metaventral process slender, nearly parallel-sided, only indistinctly narrowing anteriad, length of metaventrite medially (including metaventral process) ca. four time longer than mesoventral process; metathoracic discrimen distinct, forming a shallow impression basally (Fig.  3b). All tarsi with long setae on ventral surface. Aedeagus (Fig. 4b) 0.4 mm long, with median lobe reaching apices of parameres; basal portion of median lobe rounded laterally, apical portion widely rounded, median lobe narrowing towards apex; shape of the gonopore transversely oval. Parameres wide and slightly sinuate in median region. Phallobase as long as wide.
Comments on lectotype designation. Sharp (1882) mentions specimens from two localities: Nicaragua: Chontales and Guatemala: El Tumbador, without specifying the numbers of specimens. Specimen(s) from Guatemala are assigned to the "var.  Nicaraguan specimens mentioned in the original description, and one corresponding with "var. paulo angustior". Only the specimens from Nicaragua are considered as part of the type series, and one of them, a dissected male, is designated as a lectotype, in order to fix the identity of the species for future studies.   Smetana (1978: 14). For complete synonymy of P. exstriatum see Hansen (1999). Type locality. San Geronimo, Guatemala. Redescription. Habitus as in Fig. 1c. Body length 3.5-3.7 mm (lectotype: 3.5 mm). Body form oval in dorsal view (Fig. 1c), elytra convex in lateral view. Dorsal surface dark brown (Fig. 1c). Antennae and maxillary palpi testaceous. Pronotum slightly paler than elytra. Ventral surface reddish brown. Leg reddish, tarsomeres yellowish. Head with fine and sparse punctures. Pronotum with punctures of same size as on head. Elytral punctation strongly impressed, much denser than on pronotum and head. Epipleura very broad throughout. Meso-and metaventral processes fused into a common keel; mesoventral process arrow-head shaped with an distinct hood, as wide as metaventral process basally, metaventral process slender, parallel-sided, length of metaventrite medially (including metaventral process) ca. four times longer than mesoventral process; metathoracic discrimen indistinct (Fig. 3f). Profemora with long sparse pubescence in basal 0.75. All tarsi with long setae on ventral surface. Aedeagus (Fig. 4c) 0.4 mm long, with median lobe reaching apices of parameres or nearly so; basal portion of median lobe nearly straight laterally, apical portion widely rounded, median lobe nearly of the same width throughout; shape of the gonopore transversely oval. Parameres strongly sinuate in median region. Phallobase as long as wide (Fig. 4d).
Comments on synonymy. Examined type specimens of P. dubium morphologically correspond with specimens of P. exstriatum listed in "Additional material examined" in all characters, including morphology of the aedeagus and meso-metaventral process. Hence, we confirm that P. dubium is a junior synonym of P. exstriatum, as proposed by Smetana (1978).
Type locality (following lectotype designation). Cordova, Mexico. Redescription. Habitus as in Figs 1d and 2c. Body length 2.5-2.7 mm (lectotype: 2.7 mm). Body form oval in dorsal view (Fig. 1d), elytra evenly convex in lateral view (Fig. 2c). Dorsal surface brown (Fig. 1d). Antennae and maxillary palpi testaceous. Ventral surface reddish brown. Leg reddish, tarsomeres yellowish. Head with fine and sparse punctures. Pronotum with punctures of same size as on head. Elytral punctation strongly impressed, much coarser than pronotal and head punctation. Epipleura very broad throughout. Meso-and metaventral processes fused into a common keel; mesoventral process arrow-head shaped with narrow hood, its base narrower than apex of metaventrite; metaventral process stout, slightly widened subapically, length of metaventrite medially (including metaventral process) ca. three times longer than mesoventral process (Fig. 3c). All tarsi with long setae on ventral surface. Aedeagus (Fig.  4e) 0.5 mm long, with median lobe not reaching apices of parameres; basal portion of median lobe nearly straight laterally, apical portion widely rounded, median lobe narrowing towards apex; shape of the gonopore transversely subtriangular. Parameres wide and curved in median region. Phallobase not examined in detail.
Comments on synonymy. Orchymont (1937) considered P. laevicolle as a junior synonym of P. globulosum described from Colombia, based on the study of the type specimens of both taxa. However, he only compared external characters used for diagnosis of Phaenonotum species at that time (i.e. dorsal punctation, length of tarsi), and did not study ventral morphology and male genitalia, which are crucial characters for species identification. Smetana (1976) reexamined the types of P. laevicolle including genitalia, but he did not provide any comments on the synonymy proposed by Orchymont (1937), he neither studied the types of P. globulosum. For that reason, the synonymy of P. laevicolle with P. globulosum needs to be confirmed by future studies.   Other type material. Sharp (1882) also examined specimens from Mexico: Cordova, Toxpam, Guatemala: San Juan, San Joaquin, Zapote, and Panama: Volcan de Chiriqui, 4000 to 6000 feet, all of which have to be considered as paralectotypes. We did not examine these specimens.

Phaenonotum rotundulum
Type locality (following lectotype designation). San Geronimo, Guatemala. Redescription. Habitus as in Figs 1e and 2d. Body length approximately 2.8-3.3 mm (lectotype: 3.3 mm). Body form oval in dorsal view (Fig. 1e), elytra highly and evenly convex in lateral view (Fig. 2d). Dorsal surface reddish brown (Fig. 1e). Antennae and maxillary palpi testaceous. Ventral surface reddish brown. Leg reddish, tarsomeres yellowish. Head with fine and sparse punctures. Pronotum with punctures of same size as on head. Elytral punctation strongly impressed, much coarser than on pronotum and head. Epipleura very broad throughout. Meso-and metaventral processes fused into a common keel; mesoventral process arrow-head shaped with indistinct hood, its base as wide as apex of metaventral process, metaventral process wide basally, strongly narrowing anteriad and hence triangular in shape, length of metaventrite medially (including metaventral process) ca. three time longer than mesoventral process; metathoracic discrimen weakly developed (Fig. 3d). Profemora with long sparse pubescence in basal 0.75. All tarsi with long setae on ventral surface. Aedeagus (Fig. 4f) 0.5 mm long, with median lobe not reaching apices of parameres; basal portion of median lobe curved laterally, apical portion widely rounded, median lobe narrowing towards apex; shape of the gonopore oval. Parameres slightly sinuate in median region. Phallobase not examined in detail.
Comments on lectotype designation. Our request to borrow the Sharp specimens of P. rotundulum resulted in the receipt of the above five specimens. These specimens, however, clearly represent only a smaller part of the type series, as many other localities were mentioned in the original description by Sharp (1882). All specimens examined agree with the data provided in the original description, and hence are clearly part of the type series. In order to fix the identity of the species for future studies, we are designating the dissected male labeled as "Type" as the lectotype of P. rotundulum.  (Fig. 1f), elytra highly and evenly convex in lateral view (Fig. 2e). Dorsal surface dark brown (Fig. 1f). Antennae and maxillary palpi testaceous. Pronotum slightly paler than elytra. Ventral surface reddish brown. Leg reddish, tarsomeres yellowish. Head with fine and sparse punctures. Pronotum with punctures of same size as on head, but slightly more sparsely than the head. Elytral punctation strongly impressed, much denser than on pronotum and head. Epipleura very broad throughout. Meso-and metaventral processes fused into a common keel; mesoventral process arrow-head shaped, very wide basally, slightly hooded apically, its base slightly wider than apex of metaventral process, metaventral process stout, parallel-sided, length of metaventrite medially (including metaventral process) ca. three time longer than mesoventral process; metathoracic discrimen weakly developed (Fig. 3e). Profemora with long sparse pubescence in basal 0.75. All tarsi with long setae on ventral surface. Aedeagus (Fig. 4g) 0.7 mm long, with median lobe slightly overlapping apices of parameres; basal portion of median lobe nearly straight laterally, apical portion widely rounded, median lobe nearly of the same width throughout; shape of the gonopore rounded. Parameres slightly sinuate in median region. Phallobase slightly longer than wide.

Phaenonotum tarsale
Comments on lectotype designation. Our request to borrow the Sharp specimens of P. tarsale resulted in the receipt of the above four specimens, all of them corresponding with the original description and clearly part of the type series. In order to fix the identity of the species for future studies, we are designating the dissected male as the lectotype of P. tarsale.

Discussion
The identification of species of Phaenonotum is a difficult task, due to the similarity of the species and the complicated process of finding relevant morphological characters. This may explain the absence of keys to Phaenonotum species. Studies on Phaenonotum from Central America, together with preliminary studies on this genus in the Caribbean and South America (Deler-Hernández, unpublished data) show that reliable identification is possible based on several external morphological characters, especially the morphology of the meso-metaventral process. This structure exhibits some variation between species, especially in the shape of the metaventral process, the width of the mesoventral process, and the "size" of the apical hood of the mesoventral process (Table 1; Fig. 3; figs 10-12 in Deler-Hernández et al. 2013;figs 230-231 in Smetana 1978). Male genitalia, though very similar at first view, provide the most important characters for species identification, such as the shape of the apex and the base of the median lobe, the shape and position of the gonopore, and the shape of the external margin of the parameres (Fig. 4). Body size is also helpful in some cases, allowing the  Smetana 1978), i.e. the dorsal coloration and punctation of pronotum and elytra, are insufficient for a reliable identification, although may be helpful when used in combination with those of the meso-metaventral elevation and the aedeagus.