Chasmogenus abnormalis Sharp 1890
Creators: name: Devi, M. Bhubaneshwari
name: Devi, O. Sandhyarani
name: Fikáček, Martin
name: Minoshima, Yûsuke N.
name: Wanghengbam, Leiphon
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydrophilidae
Chasmogenus
Chasmogenus abnormalis

description: Chasmogenus abnormalis (Sharp, 1890)   
(Figs 1–13)  
 Philydrus abnormalis Sharp, 1890: 351. Type locality: Sri Lanka, Colombo.   
 Phylhydrus ferrugatus Régimbart, 1903: 57. Type localities: Cochinchine [= Vietnam], My Tho and Indonesia: Sumatra. Synonymized by Orchymont (1939: 159).   
 Philydrus nigritulus Régimbart 1903: 57. Type localities: Vietnam: Saigon, My Tho; Cambodia, Phnom Penh; Indonesia, Sumatra. Synonymized by Orchymont (1939: 159).   
 Enochrus (Lumetus) abnormicollis (Sharp): Zaitzev (1908: 385, misspelled name).   
 Helochares (Chasmogenus) regimbarti Knisch, 1924: 195 (replacement name for Philydrus nigritulus Régimbart). Synonymized by Orchymont (1939: 159).   
 Type material examined. Lectotype (hereby designated, Figs 1–6): male (BMNH): “ Philydrus / abnormalis / D.S. / Ceylon 17.4.82. / Lewis // [male symbol] // Colombo / On coast level / 7–27.IV.82, // Ceylon / G. Lewis / 1910-320. // Co- / type // A. dʼOrchymont vid. 1924 // 1936 / A. dʼOrchymont det. / Helochares (Crephelochares) / abnormalis (Sharp). Paralectotype: 1 female (BMNH): Philydrus / abnormalis / Type D.S. / Ceylon 17.4.82. / Lewis // Type / H.T. / / Sharp Coll. / 1905-313.”   
 Additional material examined (17 specimens). SRI LANKA: 1 male (BMNH): “[male symbol] // Colombo. / On coast level / 7–27.IV.82. // Ceylon / G. Lewis / 1910-320. // 1936 / A. d´ Orchymont det. / Helochares (Crephelochares) / abnormalis (Sharp) ” Considered as part of type series by Orchymont (1939), but the label data do not corresponds completely with the original description (see below for details). INDIA: Manipur: 2 males (IARI): 39 km S from Imphal, Phubala, Loktak Lake, wetland, 24°27.327ʹN 93º51.295ʹE, 763 m a.s.l., 21.xi.2013, leg. M. Bhubaneshwari, O. Sandhyarani and S. Dineshwar; 1 male, 1 female (DCIM): 45 km S from Imphal, Longum, Loktak Lake, wetland, 24º31.011ʹN 93º49.066ʹE, 822 m a.s.l., 7.ii.2014, leg. M. Bhubaneswari, O. Sandhyrani and S. Dineshwar. LAOS: Vientiane: 1 male, 1 unsexed specimen (NMPC): 55 km NE of Vientiane, 200 m a.s.l., 1.–4.v.2004, J. Bezděk lgt. JAPAN: Ryukyu Islands: Kagoshima Pref.: 1 ex. (KMNH), Amagi-chô, Tokunoshima I., 25.ii.2005, Y. Minoshima leg. Okinawa Pref.: 1 male (KMNH): Kita, Minamidaitô-jima I., Daitô Is., 25º51.006ʹN 131º14.338ʹE, 12.xii.2005, Y. Minoshima leg.; 1 female (KMNH): near Daitô-jinja, Minamidaitô-jima I., Daitô Is., 25º50.535ʹN 131º13.702ʹE, 11.iii.2005, Y. Minoshima leg.; 1 ex. (KMNH), Nagura, Ishigaki-jima I., 24º24.48ʹN 124º09.62ʹE, 18.xi.2005; Y. Minoshima leg.; 6 exs. (KMNH), Urauchi, Iriomote-jima I., 24º24.78ʹN 123º46.78ʹE, 31.xii.2005, Y. Minoshima leg.; 1 ex. (KMNH), Minami-bokujô, Yonaguni-jima I., 24º26.682ʹN 122º57.593ʹE, 25.xii.2005, Y. Minoshima leg.   
  Redescription. Form and coloration : Body elongate oval but rather depressed in lateral view, medium size, body length 3.3–4.4 mm (lectotype: 3.5 mm), body width 1.7–1.9 mm (lectotype: 1.8 mm). General dorsal coloration dark brown (in lectotype) to black, shiny. Head shiny, dark reddish, with nearly whole clypeus (in lectotype) or only its anterolateral portions slightly paler; pronotum of the same color as head, with anterior, lateral and posterolateral margins slightly paler. Elytra dark brown, of the same color as or slightly darker than head and pronotum. Ventral face of head brown, mentum and mouthparts slightly paler; mouthparts and antennae yellowish. Ventral face of thorax brown to dark brown. Abdominal ventrites dark brown with posterior margin of each ventrite slightly paler. Legs brown, tarsi yellowish.   
 Head: Punctation on clypeus moderately coarse but sparse, slightly finer on frons, with distinct larger systematic punctures on clypeus and at inner margin of each eye; interstices smooth, without microsculpture. Anterior margin of clypeus deeply excised, with the median straight portion rather narrow. Labrum strongly sclerotized, largely exposed in front of clypeus, intersegmentary membrane between clypeus and labrum narrowly exposed medially. Eyes large both dorsally and ventrally, dorsally divided by 2.3× the width of one eye. Maxillary palps long, palpomere 4 slightly shorter than palpomere 3, palpomere 3 slightly shorter than palpomere 2. Antennae with 9 antennomeres. Mentum coarsely punctuate, almost rugose; with distinct notch on anteromedial margin and depressed on anteromedial two-thirds.   
  Thorax:  Punctation on pronotum slightly coarser than on frons, with slightly larger systematic punctures present anterolaterally and posterolaterally; interstices smooth. Prosternum rather long in front of procoxae, with median carina present only extremely posteriorly, and without transverse groove. Mesoventrite with evenly rounded low carina, not bearing any long setae. Metaventrite with a narrow posteromedial glabrous area comprising ca. a half the total length of metaventrite. All femora densely pubescent in basal 0.80–0.85. Elytra with distinct sutural stria on posterior 0.75 to 0.80 of elytral length; punctation on elytral disc similar to pronotum, finer and sparser laterally and posteriorly; elytra without series of punctures, only with rather unorganized longitudinal groups of slightly larger systematic punctures.   
  Abdomen:  Abdominal ventrites densely pubescent, slightly more dense on posterior half, especially on ventrites 2– 5. Fifth ventrite with small medial emargination on posterior margin, ca. twice as long as wide and lined with yellow bristles.   
  Male genitalia:  Aedeagus 0.88–0.98 mm (lectotype 0.98 mm). Median lobe of aedeagus deeply inserted into phallobase, rather narrow on base, slightly widening up to apical third, then abruptly narrowing, with two subapical constrictions making subapical portion of lateral margin strongly sinuate; apex abruptly widened, truncate; internal sack with complex system on internal sclerites visible as dark internal structures; ventral portion with a strongly sclerotized median projection arising ca. at midlength of median lobe and reaching nearly the level of apical constriction of median lobe; base of the dorsal projection wide, then narrowing apicad into very narrow but apically truncate apex. Parameres only indistinctly longer than phallobase ventrally, but with much longer dorsal portion, inner margin of combined parameres V-shaped ventrally and widely U-shaped dorsally; inner margin of parameres weakly convex ventrally, strongly sinuate dorsally; outer margin of parameres evenly arcuate from base to apex; apical portion of paramere widened, inner margin of the apex with two small teeth (one dorsal and one ventral). Phallobase rather short, symmetrical, slightly narrowed basally, rounded at base.   
 Biology. Aquatic species; the Indian specimens were collected in along densely vegetated lake margins.   
 Distribution. Widely distributed in the Oriental region (India, Sri Lanka, Thailand, Cambodia, Vietnam, Taiwan, Singapore, Sumatra, Java, Sulawesi, Borneo, Philippines, Ryukyu Islands). Although we confirm here that the species is widely distributed in the Oriental Region, records from countries other than India, Sri Lanka, Laos and Japan (Ryukyu Islands) need to be re-confirmed based on a detailed study of the male genitalia.   
 Differential diagnosis. Chasmogenus abnormalis may be reliably distinguished from other Oriental species of the genus mainly by the morphology of the male genitalia, especially in the shape of apex of parameres and the median lobe of the aedeagus. Chasmogenus cattienus from Vietnam may be easily distinguished by wide median lobe with very narrow apex and simple apex of the parameres (see Hebauer 2002: Fig. 3). Aedeagi of C. rubricollis and C. larsi seem to be rather similar to that of C. abnormalis by the general shape and proportions, and additional studies of these species is needed to understand the differences. Based on the drawings provided by Hebauer (1992, 1995), it seems that C. rubricollis differs from C. abnormalis in apically narrowing parameres (apically widened in C. abnormalis), and C. larsi differs by parameres subapically sinuate on outer margin (evenly arcuate in C. abnormalis). The characteristic apically widened parameres with two more or less distinct inner teeth easily diagnose C. abnormalis from all other Oriental, African and Australian-Pacific species.   
 Lectotype designation. On our request to loan the type series of C. abnormalis, we received three specimens (one female and two males), which evidently are the same as those that Orchymont (1939) examined in the course of his revision of Helochares (Crephelochares) (= Chasmogenus). Only two of these specimens bear the label data precisely corresponding to the original description, i.e. locality data but also the collecting date of 17th April 1882. We consider only these two specimens as a part of the original type series, in spite of the fact that three syntypes were mentioned in the original description. Although the female specimen was considered as holotype by previous authors (Orchymont 1939, Hebauer 1992), the holotype was not specified in the original description and hence both specimens available need to be considered as syntypes. Since the morphology of the aedeagus is crucial for the species identification in Chasmogenus, we are designating here the male specimen as the lectotype, in order to fix the identity of the species.   
 Comments on variation in aedeagus morphology. Based on the specimens examined for this study, C. abnormalis are slightly variable in the extent of the subapical constriction of the median lobe of the aedeagus, and more variable in the detailed morphology of the apex of the paramere. The paramere is always widened apically, and bears two teeth (dorsal and ventral one). The size and shape of the teeth varies slightly even between the left and right paramere, and the teeth seem to be generally large in specimens from western part of the range (Sri Lanka, India) than in those from Southeast Asia. In the examined specimens from Ryukyu Island, these teeth are very small, even though still recognizable. The reexamination of the specimens from Ryukyu confirm that these specimens agree with the lectotype in all external characters and the morphology of the aedeagus, including the presence of two teeth at apex of the paramere; the simple apically widened parameres illustrated by Watanabe (1987: Fig. 5) are evidently due to inaccurate drawings.
description: Published as part of Devi, M. Bhubaneshwari, Devi, O. Sandhyarani, Fikáček, Martin, Minoshima, Yûsuke N. & Wanghengbam, Leiphon, 2016, Redescription and lectotype designation of Chasmogenus abnormalis (Sharp), with notes on its distribution, pp. 296-300 in Zootaxa 4144 (2) on pages 296-300, DOI: 10.11646/zootaxa.4144.2.12, http://zenodo.org/record/261465