Oosternum attenuatum, Hebauer, Martin Fiká Č Ek Franz & Hansen, Michael, 2009

Hebauer, Martin Fiká Č Ek Franz & Hansen, Michael, 2009, Taxonomic revision of New World species of the genus Oosternum Sharp (Coleoptera: Hydrophilidae: Sphaeridiinae) I. Definition of species groups and revision of the Oosternum aequinoctiale group, Zootaxa 2054, pp. 1-37 : 24-26

Oosternum attenuatum sp. n.

(Figs. 39, 43, 50–51, 61a–b, 67, 73, 84)

Type locality: Panama, Coclé Province, 7.2 km NE of El Cope, 750 m a.s.l.

Type material: Holotype. male ( ZMUC): “ PANAMA: Cocle / 7.2km NE El Cope, 750m / 7.Jun.1995 / R. Anderson 95-007 / wet montane forest”. Paratypes (41): PANAMA: 7 unsexed specimens ( KSEM, NMPC, ZMUC): same label data as holotype; 1 male ( KSEM): “ PANAMA: Darién / Estacion Ambiental Cana, / Cerro Pirre, 1300 m / 7°45'20"N, 77°41'6"W / 6 VI 1996; R. Anderson / PAN2A96 96-113 ex.: / cloud forest transition litter”; 1 female ( KSEM): “ PANAMA: Darién, Cana / Biological Station, 530 m / 7°45'18"N, 77°41'6"W / 0 3–0 7 Jun 1996; J. Ashe / R. Brooks, PAN1AB95 0 65 / ex: flight intercept trap”; 1 female ( KSEM): “ PANAMA: Coclé / 7.2 km NE El Copé, 730 m / 08°37'N, 80°35'W. #140 / 20 V-7 VI 1995, J. Ashe, / R. Brooks, flt. intercept trap”; 1 female ( KSEM): “ PANAMA: Panama / Cerro Campana (Capira) / 08°44'N, 79°57'W / 5 June 1995, 790 m / J. Ashe, R. Brooks #129 / ex: flight intercept trap”; 1 male, 3 unsexed specimens ( FMNH, NMPC): “ PANAMA: Panama / Cerro Campana / 3200' Feb. 1976 / A. Newton // wet debris / small stream”; 2 males, 24 unsexed specimens ( FMNH, NMPC): “El Valle, Coclé Prov., / (trail to Las Minas) / PANAMA: II:23 1959 / alt. 2400–2600 ft. [= 760–800 m a.s.l.] // Coll. by / Henry S. Dybas // F. M. N. H. (HD) / #59-220 // ground debris / Berlese (B-348)”

Additional material examined (30): COLOMBIA: 1 female ( CNC): “ COLOM. 1500 / Anchicaya [= San José de Anchicaya, ca. 3°44΄N, 77°00΄W] / VII.23.1970 / J. M. Campbell // HOLOTYPE / Oosternum attenuatum / M. Hansen”; 1 female ( CNC): “ COLOMBIA, Qbda. / Sasamuco, 23 km.W. / Villavicencio, 3–5. / III.1972 S.&J.Peck / 1000m. T912-914”; 5 females ( FMNH, NMPC): “ COLOMBIA: Meta, 23 km / NW Villovicencio. [= Villavicencio] / 1,000 m elev.; 5:III:1972 / leg. S. & J. Peck // FM(HD) #72-148, Ber. #234 / Ber.: Forest litter, 50 / litres”. ECUADOR: 5 females ( CMN, NMPC): “ ECU: Pich. 16 km E / SantoDomingo [= Santo Domingo de los Colorados], Tinalandia [Reserva Natural] / 4.V.–25.VII.85, S&J.Peck / 680m, malaise-FIT / rainforest”; 9 females, 3 unsexed specimens ( KSEM, NMPC): “ ECUADOR: Esmeraldas / Bisla Biological Station, 500 m / 0°20'24"N 79°42'36"W / 7–19 JUL 1998; P. Hibbs / ECU 2H98 001D; ex: flight intercept trap”; 1 female ( KSEM): “ ECUADOR: Pichincha / Macquipucuna Biological Station / 1300 m; 0°7'12"N, 78°37'48"W / 8–18 MAR 1996; P. Hibbs / ECU 2H96 008B; ex: malaise trap”; 5 females ( FMNH, NMPC): “ ECUADOR: Pichincha prov. / 47 km S. of Santo Domingo / Rio Palenque Sta. 700', leg. / S. Peck V:18-30-1975 // FM(HD)#75-293. Ber / 299A. Forest / litter 78 kg.”.

Differential diagnosis. Body widest at junction of pronotum and elytra; pronotum moderately convex; pronotal punctation dense, consisting of sharply impressed semicircular scar-like to rasp-like punctures; pronotal interstices lacking microsculpture; median carina of prosternum without anterior tooth; preepisternal elevation of mesothorax 1.8× longer than wide; median portion of metaventrite without intersticial microsculpture; eyes large, separated by 7.0× of one eye; parameres without inner projections; lateral projections of median lobe narrow, developed in apical 0.45 of median lobe.

Resembling O. gibbicolle and O. acutheca by body widest at junction of pronotum and elytra and pronotum without intersticial microsculpture. From O. gibbicolle it is easily recognizable by scar-like to rasplike pronotal punctures (all punctures are ring-like in O. gibbicolle ). From O. acutheca it can be recognized by less convex and shorter pronotum (Fig 39), sparser and slightly finer pronotal punctation (Figs. 50–51), larger eyes and narrowly drop-like preepisternal elevation of mesothorax (Fig. 73). As most of these external characters vary slightly both in O. attenuatum and O. acutheca , it is best to confirm the identification by examination of the male genitalia which provide very easy characters for distinguishing of both species (parameres lack inner projections in O. attenuatum whereas they bear moderately large inner projections in O. acutheca ; compare Figs. 43 and 46).

Description. HABITUS. Body widely oval, widest on base of elytra, highly convex in lateral view, strongly narrowing posteriad; TL/TW ratio = 1.6. Length: 1.30–1.40 mm, length of HT: 1.30 mm; width: 0.80–0.90 mm, width of HT: 0.80 mm.

COLORATION. Coloration of dorsal side brown to dark brown, head slightly darker than pronotum and elytra, lateral sides of elytra and pronotum reddish. Ventral side brown to reddish brown. Femora, tibiae and antennal club reddish, tarsi and antennomeres 1–6 yellowish.

HEAD. Clypeus with dense punctation consisting of small, sharply impressed, slightly rasp-like punctures, each puncture bearing fine decumbent yellowish seta; interstices without microsculpture; anterior margin slightly concave. Frons with moderately dense punctation, consisting of small, sharply impressed rounded to ring-like punctures, punctures gradually becoming scar-like posteriad; interstices without microsculpture. Eyes moderately large, separated by 7.0× of width of one eye. Mentum 2.4× wider than long, anterior margin deeply emarginate; punctation consisting of small, quite unsharply impressed round punctures bearing minute setae; interstices with fine and dense mesh-like microsculpture. Submentum with poriferous disc-like ereas. Maxillary palpus with palpomeres 2 and 4 ca. 1.5× longer than palpomere 3. Scapus longer than antennomeres 2–6 combined; antennal club ca. 2.2× longer than wide.

PROTHORAX. Pronotum slightly more convex than elytra, punctation consisting of semicircular, scarlike, sharply impressed punctures, similar on whole surface of pronotum; interstices without microsculpture. Median carina of prosternum straight in lateral view. Median portion of prosternum 1.2× wider than long, postero-mesal projection with shallow notch, pits laying next to ridges delimiting prosternal plate moderately large.

MESOTHORAX. Scutellar shield bearing a few minute punctures, interstices without microsculpture. Elytral series 1–5 arising basally, series 6–7 subbasally, series 8 in anterior 0.15, series 9 nearly reaching elytral base. Elytral series 7 and 8 markedly closer to each other than to other series. Serial punctures fine and sparse. Elytral intervals moderately convex at suture; intervals 5, 7 and 9 hardly more convex than adjacent intervals; punctation arranged to series at least on some intervals, consisting of sparsely arranged, small punctures. Elytral interstices shiny, without microsculpture. Epipleuron narrowing posteriad, reaching elytral apex. Preepisternal plate drop-like, 1.8× longer than wide; median part flat, bearing densely arranged, moderately large setiferous punctures; interstices without microsculpture.

METATHORAX. Punctation of median portion of metaventrite sparse, consisting of sharply impressed rasp-like punctures, interstices without microsculpture, shiny. Anepisternum 6.6× longer than wide.

LEGS. Tarsi with short and sparse pubescence ventrally.

ABDOMEN. Ventrite 1 with additional longitudinal ridges laterally.

MALE GENITALIA. Paramere 1.3× longer than phallobase, without inner projection, bearing two long setae apically. Phallobase narrow, 1.7× longer than wide. Median lobe gradually narrowing to obtusely pointed apex in apical 0.4; lateral projections narrow, developed in apical 0.5 of median lobe.

Variation. Examined specimens vary slightly in coloration, density of punctation on lateral parts of frons (punctation is very dense in holotype, but sparser and similar to remaining parts of frons in most paratypes), and in shape and density of punctation of the lateral portion of the pronotum (punctures are slightly denser and more circular laterally in some specimens, in contrast to semicircular punctures on the pronotal disc). So far, males are known only from Panama; all specimens examined from Colombia and Ecuador are females. Detailed examination via SEM photographs showed that the Ecuadorian specimens differ from those from Panama in the microsculpture of the mentum (this is more reduced and forming large meshes in the Ecuadorian specimens, see Fig. 61 b; compare with Fig. 61 a showing the specimen from Panama), Colombian specimens were not examined via SEM. Remaining characters of the Ecuadorian and Colombian specimens seem to correspond well to those from Panama. Further studies are needed to confirm the status of Ecuadorian and Colombian specimens by the found of a male or the proof of the parthenogenesis of these populations.

Etymology. Latin attenuatus = weakened, here in the sense of narrowing down, referring to the posteriad attenuate elytra of this species. This name was used for this species by M. Hansen in his original manuscript. Habitat. The type series was sifted from leaf litter in wet montane forest. Ecuadorian specimens were collected using FIT/Malaise traps in a rainforest.

Distribution. Distributed in southern part of Central America and northern part of Andes Mts. at altitudes 500–1500 m a.s.l. Known from Panama (Coclé Province), Colombia (Provinces of Cundinamarca, Meta and Valle del Cauca) and Ecuador (Esmeraldas, Pichincha and Santo Domingo de los Tsachillas Provinces)

Figures

FIGURES 60 – 65. Mentum. 60: O. acutheca; 61: O. attenuatum (a: specimen from Panama, b: specimen from Ecuador); 62: O. gibbicolle; 63: O. latum; 64: O. aequinoctiale; 65: O. holosericeum.