Research Article |
Corresponding author: Martin Fikácek ( mfikacek@gmail.com ) Academic editor: James Liebherr
© 2018 Emmanuel Arriaga-Varela, Sin Yeng Wong, Alexander Kirejtshuk, Martin Fikácek.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Arriaga-Varela E, Wong SY, Kirejtshuk A, Fikácek M (2018) Review of the flower-inhabiting water scavenger beetle genus Cycreon (Coleoptera, Hydrophilidae), with descriptions of new species and comments on its biology. Deutsche Entomologische Zeitschrift 65(1): 99-115. https://doi.org/10.3897/dez.65.26261
|
The hydrophilid genus Cycreon Orchymont, 1919, previously known from two historical specimens only, is reviewed based on the numerous material collected recently from the inflorescences of various Araceae species in the Malay Peninsula and Borneo. Four species are recognized in the genus: C. sculpturatus Orchymont, 1919 from Sumatra, C. armandi Shatrovskiy, 2017 from Singapore, C. adolescens sp. n. from peninsular Malaysia, and C. floricola sp. n. with two subspecies, the nominotypical one from Peninsular Malaysia, and C. floricola borneanus subsp. n. from Borneo. All species are very similar, differing only by the pronotal punctation, shape of the clypeus and the mentum, and the form of the median lobe of the aedeagus. Specimens of C. floricola sp. n. and C. adolescens sp. n. were collected from inflorescences of various genera of the family Araceae. The field observations and analysis of mid gut contents indicates that they feed on organic material on internal organs of the inflorescences, including the pollen of the host plant. They were also observed to carry a large amount of pollen and are likely pollinators of their host species of Araceae.
Sphaeridiinae , Megasternini , flower visitor, Araceae , Schismatoglottideae , new species, Malay Peninsula, Borneo, Oriental Region, pollination
Among the water scavenger beetles (Polyphaga: Hydrophiloidea: Hydrophilidae), the members of the tribe Megasternini stand out in terms of species and morphological diversity, faster speciation rate and the wide array of microenvironments inhabited (
Only two specimens of Cycreon are known so far in the literature, representing two different species. The genus was described by d’
Extensive sampling of insects associated with inflorescences of Malayan aroid plants was performed recently by
Examined specimens and depositories. A total of 1444 specimens of Cycreon were examined. Label data are reproduced verbatim; notes on the label data or additional information are written between square brackets []. List of examined specimens is available in DarwinCore-formatted spreadsheet file at Zenodo repository (https://doi.org/10.5281/zenodo.1258208). This file was also used to prepare the distribution map using QGIS software and freely available GLOBE altitude data and DIVA-GIS country borders data. The authors did not examine holotypes of C. sculpturatus and C. armandi as these are not accessible for the examination, and adopted the information about them from
The examined specimens are deposited in the following collections:
SRBC Sergey Ryndevich collection, Baranovichy, Belarus;
Morphological studies. Specimens were dissected, with genitalia embedded in a drop of alcohol-soluble Euparal resin on a piece of glass glued to a small piece of cardboard attached below the respective specimen. Habitus photographs were taken using a Canon D-550 digital camera with attached Canon MP-E65mm f/2.8 1–5 macro lens. Pictures of genitalia were taken using a Canon D1100 digital camera attached to an Olympus BX41 compound microscope; combined pictures were were made with Helicon Focus software. Scanning electron micrographs were taken using Hitachi S-3700N environmental electron microscope at the Department of Paleontology, National Museum in Prague. Pictures used for plates were adapted in Adobe Photoshop CS6. All original pictures including additional views not presented in this paper are included in the dataset submitted to the Zenodo archive under doi 10.5281/zenodo.1258208.
All known species of Cycreon are very similar and share most structural characters. We therefore provide a generic description which includes shared morphological features, while the species descriptions are restricted mostly to species-specific characters.
Cycreon Orchymont, 1919: 119.
Cycreon sculpturatus Orchymont, 1919 (by original designation).
(1) antennal grooves on prosternum small and marked by a weak ridge close to the lateral margins of prosternum (Fig.
Cycreon is distinct among Megasternini in lacking the median carina of abdominal ventrite 1 (Fig.
Body (Fig.
Head. Clypeus with anterior margin with very fine bead, anteromedian margin slightly to strongly emarginate medially (Figs
Prothorax. Pronotum transverse, moderately convex, about as wide as bases of elytra combined; lateral margins minutely bordered; anterior and posterior angles rounded (Fig.
Mesothorax. Mesoventrite completely fused with anepisternum; anterior collar of mesothorax narrow. Median portion of mesoventrite simply tectiform, elevation forming a ridge shortly overlapping anterior margin of metaventrite. Grooves for reception of procoxae absent (Fig.
Metathorax. Metaventrite (Fig.
Legs. Procoxae large, subglobular, transverse, with long setae, junction with trochanter; meso- and metacoxae wide, transverse. Tronchatero-femoral junction straight. Femora flattened, comparatively long, with very short setae; profemur without impressed parts; metafemur 1.1× as long as mesofemur (Fig.
Abdomen with five ventrites. Ventrite 1 without median carina (Fig.
1 | Clypeus strongly emarginated mesally (Figs |
2 |
– | Clypeus very weakly emarginated mesally (Figs |
3 |
2 | Pronotum with dense, completely ring-like impressions (punctures) (Fig. |
C sculpturatus d’Orchymont, 1919 |
– | Pronotum with moderately dense, half-moon shaped impressions (punctures) (Fig. |
C. armandi Shatrovskiy, 2017 |
3 | Pronotum with completely circular impressions (punctures). Mentum less transverse, 1.7× as long as wide (5B), with anteromedial emargination reaching 1/5 of length, and with many ring-like impressions (punctures) in posterior half. Aedeagus with parameres about as long as phallobase; median lobe wide, bluntly pointed at apex (Fig. |
C. adolescens sp. n. |
– | Pronotum with completely ciruclar or semicircular impressions (punctures). Mentum more transverse, 2.0× as long as wide (Figs |
4 |
4 | Pronotum with incomplete ring-like impressions (punctures) only (Figs |
.. C. floricola floricola spp. n. |
– | Pronotum with all or vast majority of impressions (punctures) in shape of complete rings (Figs |
C. floricola borneanus ssp. n. |
Habitus and morphology of Cycreon species. A–D – general habitus: A–B – C. floricola floricola ssp. n. (A – dorsal; B – lateral); C – C. floricola borneanus ssp. n., dorsal; D – C. adolescens sp. n., dorsal. E–O – morphology of C. floricola floricola ssp. n.: E – head and pronotum dorsally. F–K – mouthparts (F – mandible with unabraded apex; G – mandible with abraded apex; H – mandible, mesal view; I – labium; J – labrum; K – maxilla. L – metathoracic wing. M–O – tibiae and tarsi (M – prothoracic leg; N – mesothoracic leg; O – metathoracic leg).
External morphology of Cycreon floricola floricola ssp. n. A– head, ventral view; B – detail of male mouthparts in ventral view; C – prothorax in ventral view; D – detail of the antennal groove; E – meso- and metaventrite; F – prosternum and mesoventral elevation in ventrolateral view; G – abdominal ventrites. Abbreviations: abv1 – abdominal ventrite 1; ang – antennal grooves.
Male genitalia of Cycreon species (except C. sculpturatus for which male remains unknown). A–D – C. floricola floricola ssp. n., holotype; E–H – C. floricola borneanus ssp. n., holotype; I–J – C. adolescens sp. n., holotype; K–M – C. armandi Shatrovskiy, 2017, holotype. A, E, K – median lobe; B, F – median lobe in lateral view; C, G, L – tegmen; D, H, M – sternite 9; I – whole aedeagus; J – reconstructed shaped of the median lobe. K–M adapted from
Surface sculptures of Cycreon species. A–C, J – C. adolescens sp. n., holotype; D–F – C. floricola borneanus ssp. n., paratype; G–I, K – C. floricola floricola ssp. n., paratype from the type locality. A, D, G – head punctation; B, E, H – pronotum punctation; C, F, I – elytral punctation; J–K – punctation of mentum.
Diagnostic characters of known Cycreon species. A–C – C. adolescens sp. n.; D–F – C. floricola borneanus ssp. n.; G–I – C. floricola floricola ssp. n.; K–L, S – C. armandi; O–R – C. sculpturatus. A, D, G, K, O – anterior margin of clypeus; B, E, H, L, P – mentum (superficial sculpture omitted in L and P); C, F, I, M, Q – pronotal punctation; R–S – metatibia. K, M–S redrawn from
Biology of Cycreon floricola sp. n. A–B – alive specimens of C. floricola borneanus in the inflorescence of Schottarum sarikeense at Sebankoi Recreational Park, Betong, Roban, Sarawak in January 2010 (photo by S.-Y. Wong). C–E – safranine-dyed gut content of C. floricola borneanus collected from Schismatoglottis calyptrata complex in Tawau Hills, Kebun Botani on 8th July 2016 (collecting event AR-2659). F–I – examples of aroid plants on which the species were collected (F – Alocasia longiloba; G – Schismatoglottis giamensis; H–I – Ooia glans).
Cycreon sculpturatus Orchymont, 1919: 121.
Cycreon
sculpturatus
:
Indonesia: South Sumatra: Palembang [ca. 2.9861°S, 104.7555°E].
None (information adopted from
Cycreon sculpturatus can be distinguished from other species of the genus by the deeply incised clypeus, pronotum densely covered with complete ring-like impressions (punctures) and straight meso- and metatibiae.
Body 2.6 mm long; colouration light reddish-brown, with slightly darker head and elytra; clypeus about 2.5× as wide as long, with anterior margin conspicuously emarginate medially (Fig.
Only know by a single female specimen from the type locality (Indonesia, Sumatra, Palembang) (Fig.
According to
Cycreon armandi Shatrovskiy, 2017: 589.
Singapore.
None (information adopted from
Cycreon armandi can be distinguished from other known species by the deeply incised clypeus, the semicircular impressions (punctures) on the pronotum, and the curved meso- and metatibae.
Body 3.3 mm long; colouration completely light reddish-brown; clypeus about 2× as wide as long, anterior margin of clypeus strongly emarginate medially (Fig.
Only known from the type locality in Singapore (Fig.
According to
Malaysia, Pahang, Genting Highland [ca. 3.4233°N, 101.7930°E].
Holotype (male, teneral specimen): “Malaysia, PAHANG / Genting Highland / 24.X.2012 / H. Takizawa” (
MALAYSIA: Pahang: Cameron Highlands, Tanah Rata, Robinson Waterfall [ca. 4.461778°N 101.38803°E], in flowers of Araceae, 15.iii.2015, H. Takizawa lgt. (5 females: EIHE,
This species is most similar to Cycreon floricola borneanus ssp. n. in the very weakly emarginate anterior margin of the clypeus and pronotal punctation consisting of circular punctures, and straight meso- and metatibiae. It differs from the latter in the structure of the male genitalia (relatively longer phallobase and widely pointed apex of the median lobe) and by the less transverse mentum (1.7× wider than long), with many ring-like impressions in posterior half.
Measurements. 2.4–3.0 mm long (length of holotype: 2.8 mm), 1.7× as long as wide, widest at basal fifth of elytra; weakly convex, 3.3–3.5× as long as high (height of holotype: 0.82 mm). Colouration. Light brown with slightly darker elytra (Fig.
Head. Clypeus about 2.4× as long as wide, with anterior margin of clypeus margin very weakly emarginate medially. Frons and clypeus with punctation composed of complete circular impressions (punctures) with a small setiferous puncture on anterior margin (Fig.
Prothorax. Pronotum transverse, widest at base 2.2× wider than long; 1.6× wider at base than between anterior angles, 1.7× wider than head including eyes. Punctation dense and shallow, consisting of circular impressions with one small setiferous puncture on posterior margin (Fig.
Pterothorax. Elytra widest at anterior fifth, 1.1–1.2× as long as wide, 2.9–3.0× as long as pronotum, 1.2–1.3× as wide as pronotum. Punctation on intervals composed of semicircular impressions with a setiferous puncture on posterior margin (Fig.
Male genitalia (Fig.
The species name reflects the teneral condition of the holotype (from Latin adolescens = growing up, maturing).
The species is only known two localities in Pahang province, Malaysia.
No details about collecting circumstrances are available for type specimens; additional specimens from Tanah Rata were collected from inflorescences of Araceae (H. Takizawa, pers. comm. 2018).
Measurements. 2.2–3.4 mm long (length of holotype: 2.9 mm), 1.8–2.0× as long as wide, widest at basal fifth of elytra; weakly convex, 3.1–3.4× as long as high (height of holotype: 0.9 mm). Colouration. Light brown with darker elytra (Figs
Head. Clypeus about 2.5× as wide as long, with anterior margin of clypeus margin very weakly emarginate medially. Frons and clypeus with punctation composed of complete circular impressions (punctures) with one small setiferous puncture on anterior margin (Figs
Prothorax. Pronotum transverse, widest at base, 2.2× as wide as long; 1.5–1.6× wider at base than at anterior angles, 1.6× as wide as head including eyes. Punctation dense and shallow, consisting of semicircular to complete ring-like impressions with a small setiferous puncture on posterior margin (Figs
Pterothorax. Elytra widest at anterior fifth, 1.1–1.2× as long as wide, 2.9–3.0× as long as pronotum, 1.1× as wide as pronotum. Punctation on intervals composed of semicircular impressions with setiferous puncture on posterior margin (Fig.
Legs. Metatibiae wide and flattened, very weakly curved, 0.35× as long as elytra, 4.8× as long as wide.
Male genitalia. Median projection of sternite 9 (Fig.
The species name reflects the association of this species with flowers, it consists of flori- (from Latin flos, floris = flower) and -cola (from Latin incola = inhabitant).
This species is composed of two phenotypically distinguishable forms which are geographically exclusive and are here descibed as subspecies. Morphological differences are mainly restricted to punctation on the pronotum, which consists exclusively of incomplete ring-like impressions in the mainland form (C. f. floricola ssp. n.), and exclusively or mainly of the completely ring-like forms in the specimens from Borneo (C. f. borneanus ssp. n.).
Malaysia, Kelantan, Guala Musang prov., Kuala Koh district, Taman Negara, 700 m from the entrance, 96 m a.s.l., 4°52.333ʹN 102°26.872ʹE.
Holotype (male:
This subspecies is very similar to Cycreon floricola borneanus ssp. n. with which it shares most of the external characters including genital morphology. Cycreon floricola floricola can be distinguished by the pronotal punctation consisting exclusively of the incomplete ring-like punctures. The dorsal coloration of the is slightly more contrasting in most specimens of C. floricola floricola than in representatives of C. f. borneanus ssp. n., with the pronotum darker compared to the elytra.
Measurements. 2.4–3.2 mm long (length of holotype: 2.7 mm), 1.9–2.0× as long as wide, widest at basal fifth of elytra; weakly convex, 3.2–3.4× as long as high (height of holotype: 2.7 mm). Colouration. Pale yellowish-brown with dark-brown elytra (Fig.
Pronotum 2.2× wider than long; 1.6× wider at base than between anterior angles, with punctation dense and shallow, consisting of semicircular impressions (punctures) with a small setiferous puncture on posterior margin. Punctation approximately same in size and density all over pronotum.
Elytra widest at anterior fifth, 1.1–1.2× as long as wide, 2.9–3.0× as long as pronotum, 1.1× as wide as pronotum. Punctation on intervals composed of semicircular impressions with one setiferous puncture on posterior margin.
The subspecies is known from two regions in Peninsular Malaysia, in provinces of Johor and Kelantan.
Many specimens of C. floricola floricola were collected inside of inflorescences of Schismatoglottis species and Kiewia ridleyi (
Malaysia, Sabah, Tawau, Lahad Datu, Tawau Hills National Park, Kebun Botani, 305 m a.s.l., 4°23ʹ59.4ʺN 117°53ʹ17.2ʺE.
Holotype (male:
This species is very similar to Cycreon floricola floricola with which it shares most external characters and genital morphology. Cycreon floricola borneanus ssp. n. can be distinguished from C. floricola floricola by the shape of the pronotal punctation consisting only or largely of complete ring-like punctures. The dorsal coloration of C. floricola borneanus sp. n. is usually more uniform, with elytral colouration not much darker than pronotal one.
Measurements. 2.2–3.4 mm long (length of holotype: 2.9 mm), 1.8–1.9× as long as wide, widest at basal fifth of elytra; weakly convex, 3.1–3.3× as long as high (height of holotype: 2.8 mm). Colouration. Pale brown with weakly darker elytra (Fig.
Pronotum 2.2× wider than long; 1.5× wider at base than between anterior angles, 1.6× wider than head including eyes. Punctation dense and shallow, consisting of complete ring-like impressions with one small setiferous puncture on posterior margin (Figs
Elytra widest at anterior fifth, 1.1–1.2× as long as wide, 2.9–3.0× as long as pronotum, 1.1× as wide as pronotum. Punctation on intervals composed of semicircular impressions with one setiferous puncture on posterior margin (Fig.
In most specimens examined from Borneo, the pronotal punctation consists exclusively of completely ring-like punctures. However, in few localities on the north-western coast of Borneo the punctation of 5-20% of specimens shows a mixture of complete and incomplete rings. In the absence of genetic data, we are unable to analyze this variation in detail, and hence temporarily treat even these specimens as C. floricola borneanus.
The name of this species is derived from Borneo, the historical name of island where all the known specimens of this subspecies were collected.
The species seems to be widespread in Borneo, it is recorded from Indonesia: Kalimantan Barat and Kalimantan Selantan and Malaysia: Sabah, Sarawak (Fig.
This subspecies has been collected in inflorescences of a number of plant species belonging to the Araceae family. It was collected in high numbers in flowers of the genus Schismatoglottis: S. calyptrata, S. colocasioideae, S. erumpens complex, S. giamensis (Fig.
All specimens of both subspecies of C. floricola have been collected in inflorescences of various Araceae genera, often in high numbers, indicating their tight association with this microhabitat. The fact that there were only two specimens of the genus known up to now likely correspond with the biology of Cycreon beetles, since no study of flower-inhabiting beetles associated with Araceae in the Malaysian Peninsula and Sunda islands was performed previously.
Mouthparts of Cycreon (Fig.
The excised clypeus and anterior margin of mentum is unusual in the Megasternini. Excised mentum is only known in the Central American genus Nitidulodes, which is also associated with aroid inflorescences (
Interactions of Cycreon with aroid inflorescences can be interpreted as an initial stage of development of cantharophyly, i.e. interrelations between beetles and plant reproductive organs, in which only adult are associated with flowers (e.g.,
We are indebted to H. Takizawa and Y. N. Minoshima (Japan) for providing us with the material from their collections. This work was supported by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 642241 to EAV, and by the Ministry of Culture of the Czech Republic (DKRVO 2018/13, National Museum, 00023272) to MF. The work of EAV at the Department of Zoology, Charles University, Prague was partly supported by grant SVV260434/2018. WSY acknowledges the funding from the Ministry of Education of Malaysia through Vote No. NRGS/1089/ 47 2013-(03). The study of AGK was performed in the frames of the state research project AAAA-A17-117030310210-3 and partly supported by the programme of the Presidium of the Russian Academy of Sciences “Evolution of organic world. Significance and influence of planetary processes” and the Russian Foundation of Basic Research (grant No. 18-04-00243–a).
List of known specimens of Cycreon in DarwinCore format