Eur. J. Entomol. 102: 231–240, 2005 ISSN 1210-5759 Description of the larval stages of Gymnochthebius jensenhaarupi and phylogenetic analysis of the relationships with other species of the subfamily Ochthebiinae (Coleoptera: Hydraenidae) JUAN A. DELGADO1 and MIGUEL ARCHANGELSKY2 1Departamento de Zoología y Antropología Física, Facultad de Biología, Universidad de Murcia, 30100, Murcia, Spain; e-mail: [email protected] 2CONICET– Facultad de Ciencias Naturales (LIESA), Universidad Nacional de La Patagonia San Juan Bosco, Sarmiento 849, 9200 Esquel, Chubut, Argentina; e-mail: [email protected] Key words. Coleoptera, Hydraenidae, Ochthebiinae, Gymnochthebius, larvae, chaetotaxy, phylogeny, Argentina, Neotropics Abstract. The three larval instars of Gymnochthebius jensenhaarupi (Knisch, 1924) are described and illustrated, including a detailed analysis of their chaetotaxy and porotaxy. The specimens used in this study were collected with adults of G. jensenhaarupi and have been identified as such by association. Comparative notes on the morphology of these larvae with other species of the sub- family Ochthebiinae are given. A hypothesis of phylogenetic relationships between G. jensenhaarupi and other members of Ochthe- biinae with thoroughly described larvae is presented. The monophyly of Ochthebiinae is supported by additional larval features. On the other hand Ochthebius, as currently composed, seems to by paraphyletic. Gymnochthebius Orchymont, 1943 is confirmed as the sister group of Aulacochthebius Kuwert, 1887. INTRODUCTION ated with a number of larvae that can be assigned to this Gymnochthebius Orchymont, 1943 is a genus of Hyd- species. This finding offers a good opportunity to de- raenidae composed by thirty-one species. Most of them scribe and figure the larval morphology of Gymnochthe- are endemic to the Neotropical (20) or Australian (6) bius comparing its morphology with those of other known regions and a few (3) are known exclusively from the larvae of Ochthebiinae in order to evaluate their relative Nearctic region. The two remaining species have a wide position within this subfamily. American distribution and they are found both in the MATERIAL AND METHODS Neotropical and Nearctic realms (Hansen, 1998; Perkins Material examined & Archangelsky, 2002). As some other ochthebiine genera Gymnochthebius was originally proposed as a Twenty-one larvae (eight first instars, eight second instars and subgenus of Ochthebius Leach, 1815 but was convin- five third instars) from Argentina, La Rioja, Talampaya National Park, Shimpa River; 14.v.1999; leg. M. Archangelsky. cingly considered as a distinct genus by Perkins (1980). The larvae described below were collected with adults of G. Hansen (1991) pointed out morphological similarities jensenhaarupi and identified as such by association. All the between adults of Gymnochthebius and Aulacochthebius studied specimens seem to belong to the same species consid- Kuwert, 1887, but it was Perkins (1997) who explicitly ering their similar external morphology and congruent chaeto- postulated a close phylogenetic relationship between both taxic pattern. Furthermore, no other species of Hydraenidae was genera (along with Gymnanthelinus Perkins, 1997) in a collected in the same locality during the sampling period. Addi- lineage comprising also the genera Ochthebius, tional adults and larvae were collected in the same locality on Hughleechia Perkins, 1981 and Micragasma Sahlberg, 2.xi.1999 (three different stations) and 9.ii.2000 (one station). 1900 within the subfamily Ochthebiinae. Unfortunately, Adults of G. jensenhaarupi were also collected at the same locality on 3.viii.1999. this close phylogenetic relationships could not be tested All larvae were preserved temporarily in glycerol, which in Beutel et al. (2003) since these authors did not include allowed for their examination from various perspectives. After- Aulacochthebius in their cladistic study. wards the preparations were transferred into ethanol for two As in many other groups of Hydraenidae, the immature hours for glycerine removal, and then transferred onto perma- of Gymnochthebius are poorly known, thus these stages nent DPX slides. All preparations were stained with Chlorazol have been of little help until now both in taxonomic and Black. Drawings were made with a camera lucida attached to a in phylogenetic studies. Richmond (1920) studied the compound microscope. The terminology and format used in the larva of G. fossatus (LeConte, 1855) (under Ochthebius description of these larvae follows that of Delgado & Soler tuberculatus LeConte, 1878) but, even though lengthy, (1997b) and Delgado & Palma (1998). The specimens used in this study are deposited in the research collection of the former this description lacks good illustrations and does not men- author held at the Departamento de Zoología y Antropología tion key morphological characters of hydraenid larvae. Física, Facultad de Biología, Universidad de Murcia; additional Recently, several adults of Gymnochthebius jensenhaa- specimens are deposited in the research collection of M. Arch- rupi (Knisch, 1924) were collected in Argentina associ- angelsky, at the Universidad Nacional de La Patagonia. 231 Figs 4–8. First instar larva of G. jensenhaarupi, mouthparts and antenna. 4. dorsal view of labrum; 5, ventral view of labium; 6, ventral view of left maxilla; 7, dorsal view of right mandible; 8 dorsal view of right antenna. Abbreviations: C1-2: campaniform sensilla; Ga: galea; La1: lacinial seta 1; Lg, ligula; Lm1-5, labral marginal setae; M1-2, mandibular setae; Mnt, mentum; Pf1, palpiferal seta; Pmnt, prementum; Pr, prostheca; SD, sensory digitiform sensilla; Smnt, submentum; Stp1-4, Figs 1–3. First instar larva of G. jensenhaarupi, head capsule. setae of the stipes; IIA1-4, antennal setae of segment II; 1, dorsal view; 2, lateral view; 3, ventral view. Abbreviations: IIIA1-4, antennal setae of segment III; IIS1-2, antennal solen- CG, cephalic glands; Cl1-3, clypeal setae; EB and eb, egg- idia of segment II; IIIS1-3, antennal solenidia of segment III. bursters; EC1-2, epicranial campaniform sensilla; Ed1-2, epicra- nial discal setae; El1-2, epicranial lateral setae; Em1-2, epicranial marginal setae; FC1, frontal campaniform sensillum; reduced and composed by four small denticles, an ante- Fd1-2, frontal discal setae; Fl1-2, frontolateral setae; Fm1, fron- rior pair (Fig. 1: eb) not clearly detected in all specimens tomarginal setae; L1-2, cephalic lateral setae; LC1, cephalic lat- and a posterior pair (Fig. 1: EB) slightly conspicuous. eral campaniform sensillum; P1-4, epicranial posterior setae; Frontoclypeal suture indistinct. Clypeus (Fig. 1) with T1-4, temporal setae; V1-2, ventral setae. three setae on each side (Cl1–Cl3). Epicranial regions (Fig. 1) each with two campaniform sensilla (EC1, EC2), LARVAE OF GYMNOCHTHEBIUS JENSENHAARUPI one cephalic gland (CG) and ten setae: a row of four (Knisch, 1924) minute posterior setae (P1–P4), two epicranial dorsal (Figs 1–22) setae (Ed1, Ed2), two epicranial lateral setae (El1, El2) First instar and two epicranial marginal setae (Em1, Em2). Temporal regions (Fig. 2), each with four long setae (T1–T4). Lat- Elongate, slender. Head and body sclerites moderately eral regions (Fig. 2), each with one campaniform sen- sclerotized. Colour of sclerites uniformly yellowish. Total sillum (LC1) and two setae (L1, L2). Ventral regions body length about 1.2 mm. (Figs 2–3), each with two setae (V1, V2); gula wider than Head long. Labrum cordiform (Fig. 4) with the basic pattern of Head capsule width 0.29 mm ± 0.05 (mean ± S.D.; n = chaetotaxy of other hydraenid species (e.g. Delgado & 6); head transverse, approximately ovoid in silhouette, Palma, 1998), with two campaniform sensilla (C1, C2) on slightly narrowed posteriorly and subglobular laterally. each side and seven setae arranged in two rows: two Ecdysial line Y-shaped; five stemmata are present on discal setae (Ld1, Ld2) and five marginal setae each side, ocular area subdivided into two oblique rows. (Lm1–Lm5); campaniform sensilla (C1) inconspicuous in Chaetotaxy of head capsule as in Figs 1–3. Frontal region most specimens studied; setae Lm1, Lm3 and Lm5 situ- (Fig. 1) on each side with five setae, two frontodorsal ated dorsolaterally, Lm2 and Lm4 ventrolaterally (Fig. 4); (Fd1, Fd2), two frontolateral (Fl1, Fl2), one frontomar- setae Lm2 (Fig. 4) pectinate. Antennae (Fig. 8) 0.4 as ginal (Fm1). Campaniform sensillum (FC1) present and long as head capsule width, antennomere II about 3× as clearly visible in all specimens. Egg-bursters extremely long as antennomere I, with four setae (IIA1–IIA4) and 232 Figs 12–14. Larva of G. jensenhaarupi. 12, first instar, mesonotum; 13, first instar, abdominal tergum II; 14, third instar, proleg with labeled chaetotaxy in tibia and tarsungulus. Abbreviations: A1-4, anterior setae; Ad1, anterodorsal seta; Al1, anterolateral seta; Av1, anteroventral seta; C1-4, campani- form sensilla; Da1, Db1, Dc1, primary dorsal discal setae; DP1-2, dorsopleural setae; L1-3, lateral setae; P1-4, posterior setae; Pd1-2, posterodorsal setae; Pl1, posterolateral seta; Pv1, posteroventral seta; Sp, spiracle. Figs 9–11. Larva of G. jensenhaarupi, chaetotaxy of pro- thorax. 9, first instar; 10. second instar; 11, third instar. Abbre- longer than wide, transverse and widely separated from viations: A1-4, anterior setae; C1-5, campaniform sensilla; Da1, each other by submentum, each with one seta (Cdo1); Db1, Dc1, primary dorsal discal setae; Db’, subprimary dorsal