Alarm substance in Gyrinus aeratus (Coleoptera,Gyrinidae)

Gyrinid beetles are common in ponds and lakes in Sweden, where they aggregate in open areas of the surface. Gyrinid beetles have pygidial glands which produce compounds rendering them unpalatable to fish. This study examines whether the pygidial secretion can be used for alarm purposes in addition to other functions. Experiments showed that gyrinid beetles responded to water prepared with the pygidial compounds by evasive behaviour. The beetles did not respond when the compound was mediated by air. One component of the defense system of gyrinids is how they advertise their presence. The aggregation of dark beetles with their typical motion pattern when alerted is very conspicuous and easily identified by an experienced predator. We suggest that this aspect of gyrinid defence can be characterized as aposematic.     

A taxonomic review of the Gyrinidae (Coleoptera) in Korea

A taxonomic review of Korean Gyrinidae is presented. Seven species [Dineutus orientalis (Modeer, 1776), Gyrinus gestroi Régimbart, 1883, Gyrinus japonicus Sharp, 1873, Gyrinus pullatus Zaitzev, 1908, Orectochilus punctipennis Sharp, 1884, Orectochilus Regimbarti Sharp, 1884 and Orectochilus villosus (Müller, 1776)] in three genera are recognized, one of which (Orectochilus punctipennis Sharp, 1884) is reported for the first time in Korea. We also found that Gyrinus curtus Motschulsky, 1866 previously recorded in Korea was an incorrect identification of Gyrinus pullatus Zaitzev, 1908. Habitus and SEM photographs, distribution maps, keys, and diagnoses of genera and species are provided.     

On the systematic position of the family Gyrinidae (Coleoptera: Adephaga)

Various characters of adult and larval members of Adephaga and Cupedidae were analyzed, and suggest that Gyrinidae are the sister-group of the remaining Adephaga, and are not closely related to the remaining aquatic Adephaga. The aquatic families Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae seem to form a well founded monophyletic unit. The following characters are considered as synapomorphies of Adephaga excluding Gyrinidae: bifurcate condition of the muscle (= M.) tentoriopraementalis inferior, reduction of hypopharynx, strongly developed prosternal process, reduction in size and specialized modification of the ventral sclerite of the mesothorax, strongly developed mesofurcal arms, a high mesopleural ridge, globular mesocoxae restricted to rotatory movements, invaginated sternum VIII (coxostemum), the strongly curved base of the median lobe of the aedeagus, which articulates with the parameres, the rotated position of the aedeagus in repose, fusion of the larval clypeolabrum with the frons and reduction of the larval lacinia. Mesal shifting of M. episterno-coxalis prothoracis, and the fusion of the apical portions of the malpighian tubules of either side are considered as synapomorphies of Adephaga excluding Rhysodidae and Gyrinidae. Lateral reduction of the meta “sternal” transverse ridge and the presence of the subcubital setal binding patch of the hind wing are considered as synapomorphic characters of Trachypachidae, Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae. We postulate that the metacoxal fusion occurred independently in gyrmids and the common ancestor of Trachypachidae, Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae. Consequently we consider this character state as another synapomorphy of Trachypachidae and Hydradephaga excluding Haliplidae and Gyrinidae. The following characters are considered as synapomorphies of Noteridae, Amphizoidae, Hygrobiidae and Dytiscidae: Loss of tactile setae on the head capsule, metafurcal origin on the intercoxal wall, expansion of the intercoxal wall, elongation of the subcubital setal binding patch, loss of Mm. furca-coxale anterior and posterior, reduction of the larval abdominal segments IX and X, and the shifting of the uropmphi onto the ventral side of segment VIII. Presence of M. tentorio-mandibularis and M. stipitopalpalis intemus are certainly primitive features of adult gyrinids but the distribution of these character states among most members of Adephaga is yet unclear. Chemical defence gland constituents point towards a very isolated position of Gyrinidae. The old age of the group, documented by a larva found in upper Permian deposits, may support the hypothesis of a sister-group relation-ship between Gyrinidae and the remainder of Adephaga.     

Larval morphology and chaetotaxy of Macrogyrus oblongus (Boisduval, 1835) (Coleoptera: Gyrinidae)

The larvae of the grooved whirligig beetle Macrogyrus oblongus (Boisduval, 1835) are described and illustrated including detailed morphometric and chaetotaxic analyses of selected structures. Larvae of Macrogyrus Régimbart, 1882 Régimbart, M. (1882), ‘Essai Monographique de la Famille des Gyrinidae. 1re partie’, Annales de la Société entomologique de France, 51, 379–458. [Google Scholar] exhibit the characters traditionally recognised as autapomorphies of the Gyrinidae. The first instars bear egg bursters on the parietal, a potential additional autapomorphy. Putative larval autapomorphies of the tribe Dineutini are the presence of additional setae on the mandible, the absence of the seta TR2, and the presence of pore-like additional structures on the ultimate palpomeres. Macrogyrus larvae differ from those of the other known dineutine genera (Andogyrus Ochs, 1924 and Dineutus MacLeay, 1825) in the absence of a neck constriction and in the distal position of the pore LAc. Other useful characters to distinguish genera within Dineutini are the presence or absence of additional setae on the cardo and coxa, and the posterior margin of the lacinia dentate or smooth.     

The unique locomotor apparatus of whirligig beetles of the tribe Orectochilini (Gyrinidae,Coleoptera)

Whirligig beetles, which are known for their rapid gliding on the water surface, have evolved a unique locomotor apparatus. External and internal thoracic structures of Orectochilus villosus (Orectochilini) are described in detail and documented with microcomputed tomography, computer‐based 3D reconstructions, and scanning electronic microscopy (SEM). The results are compared with conditions found in other genera of Gyrinidae and other groups of Coleoptera. The focus is on structures linked with locomotion, especially on the unusual flight apparatus, which differs strongly from that of other beetles. As in the other Orectochilini, the prothorax of Orectochilus displays characters typical for Gyrinidae, with triangular procoxae and forelegs transformed into elongated, sexually dimorphic grasping devices. The musculature of this segment is similar to the pattern found in other Coleoptera. Similar to all other extant Gyrinidae, the mesothorax is characterized by an extensive and flat mesoventrite, suitable for gliding on the water surface. As in Heterogyrinae and the other Gyrininae, the pterothoracic legs are transformed into paddle‐like structures, enabling the beetles to move with high speed on the surface film. The musculature of the mesothorax is reduced compared to other Coleoptera, but similar to what is found in the other Gyrininae. The metathoracic skeleton and musculature are simplified in Orectochilini compared to other Gyrininae and other groups of Coleoptera. In O. villosus, only 10 metathoracic muscles are preserved. 36 are present in an archostematan beetle, a condition probably close to the coleopteran ground plan. The metathoracic dorsal longitudinal bundles are absent in Gyrininae, muscles that play a role as indirect flight muscles in most other neopteran insects. The rest of the posteromotoric flight apparatus is distinctly modified, with a limited number of skeletomuscular elements taking over more functions. The large muscle M84 (IIIdvm7) M. noto–trochanteralis, for instance, functions as dominant wing levator, but is also responsible for the powerful and rapid backstroke of the hind legs. The presence of this muscle is a synapomorphy of Heterogyrinae and Gyrininae. The narrow metafurca in the latter group is likely linked to its large size. The elytra likely contribute to the control of the flight of the beetle, whereas they shield and inhibit the flight apparatus during swimming.     

The New World whirligig beetles of the genus Dineutus Macleay, 1825 (Coleoptera,Gyrinidae, Gyrininae,Dineutini)

All New World members of the whirligig beetle genus Dineutus Macleay, 1825 are treated. The New World Dineutus are found to be composed of 18 species and 6 subspecies: one species, Dineutus mexicanus Ochs, 1925, stat. n. is elevated from subspecies to species rank, and the subspecies Dineutus carolinus mutchleri Ochs, 1925, syn. n. is synonymized here with the typical form. Lectotypes are designated for Dineutus discolor Aubé, 1838, Dineutes metallicus Aubé, 1838, Dineutus solitarius Aubé, 1838, Dineutes analis Régimbart, 1883, and Gyrinus longimanus Olivier, 1795. Each taxonomic unit is provided with a taxonomic history, type locality, diagnosis, distribution, habitat information, and a discussion section. The aedeagus and male mesotarsal claws are illustrated, and dorsal and ventral habitus images of both sexes, for each species and subspecies are provided. General distribution maps are provided for all taxonimc units. A key to the genera of New World Gyrinidae, as well as all the New World Dineutus species is provided. General Dineutus anatomy as well as a clarification of homology and anatomical terms is included.     

On the thoracic anatomy of the Madagascan Heterogyrus milloti and the phylogeny of Gyrinidae (Coleoptera)

Gyrinidae is a group of beetles with a unique specialization of swimming on the water surface. Heterogyrus milloti Legros (Heterogyrinae) from Madagascar is a species with various preserved plesiomorphic features. The information on the morphology and biology was very limited until recently, and the thoracic anatomy remained largely unknown. Consequently, the aim of the present study is to describe external and internal thoracic features of Heterogyrus Legros in detail and to interprete them with respect to their phylogenetic and functional significance, with a special focus on the unusual flight apparatus of Gyrinidae. Characters documented with innovative techniques are compared to conditions found in other gyrinid genera and other groups of Adephaga, including characters of other body parts and larvae. A data matrix with 144 characters of adults, larvae and eggs was compiled and analysed cladistically. Gyrinidae excluding Spanglerogyrus Folkers (Heterogyrinae + Gyrininae) is supported by many apomorphies, mainly by a unique locomotor apparatus with paddle‐like middle and hind legs. The results confirm Heterogyrus as the earliest diverging branch in Gyrinidae except Spanglerogyrus, implying a sister‐group relationship between this genus and Gyrininae, a clade comprising Gyrinini, Dineutini and Orectochilini. The presence of an opening between the mesanepisternum and elytra, reduction of the lateral metafurcal arms, loss of the metathoracic M. furcacoxalis lateralis, and modifications of the head, including the dorsal shift of the upper subcomponent of the compound eyes, are synapomorphies of the three tribes. The monophyly of Gyrinini is moderately well‐supported, whereas Orectochilini is strongly supported by different characters including a highly simplified but functioning flight apparatus. A clade comprising Orectochilini and the dineutine genera is suggested by synapomorphies of adults and larvae. The monophyly of Dineutini was supported in a recent study, but not by the characters analysed here. Features of adults, larvae and eggs indicate that Gyrinidae are the sister group to the remaining adephagan families, as suggested in some earlier morphology‐based studies and recent analyses of large molecular datasets.     

Über das Ortungsvermögen des TaumelkäfersGyrinus substriatus Steph. (Coleoptera,Gyrinidae)

Zusammenfassung An freischwimmenden, wie an ortsfest, aber drehbar gehaltenen Taumelkäfern wird untersucht, welche von sieben einfachen mathematischen Operationen zur nervösen Weiterverarbeitung der von den Antennen beim Empfang von Wasserwellen aufgenommenen mechanischen Signale nicht ausgeschlossen werden können. Es sind: Messung der Laufzeit der Signale zwischen beiden Antennen (Modell 1), Multiplikation der Summe der Signale mit dem zeitlichen Integral über ihre Differenz (Modell 6) sowie die Kreuzkorrelation zwischen den Signalen (Modell 7). Die Versuche zeigen, daß schwimmende Taumelkäfer in hohem Maße spontanaktiv sind. Hierdurch werden Fehler beim Anpeilen und Anschwimmen der Beute kompensiert.

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The capability of direction-finding by the whirligig beetleGyrinus substriatus Steph. (Coleoptera, Gyrinidae)

Summary The reactions of whirligig beetles (either freeswimming or suspended turnably) to sources of surface waves of the water were investigated in order to determine which of seven simple mathematical operations for describing the nervous processing of mechanical signals received by the antennae could be excluded. The non-excludable operations were: measurement of the time needed for a signal to go from one antenna to the other (model 1), multiplication of the sum of the signals by the time integral of their difference (model 6), and cross-correlation between the signals (model 7). The experiments have shown, that swimming whirligig beetles act very spontaneously. This activity compensates errors in finding directions and in approaching the prey.

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Die Verfasser danken der Deutschen Forschungsgemeinschaft für die zur Durchführung der Untersuchungen bereitgestellten Mittel sowie Frau Hildegard Muchowski für ihren Einsatz beim Ermitteln der Bahndaten der schwimmenden Käfer.     

Experimental Studies and Dynamics Modeling Analysis of the Swimming and Diving of Whirligig Beetles (Coleoptera: Gyrinidae)

Whirligig beetles (Coleoptera, Gyrinidae) can fly through the air, swiftly swim on the surface of water, and quickly dive across the air-water interface. The propulsive efficiency of the species is believed to be one of the highest measured for a thrust generating apparatus within the animal kingdom. The goals of this research were to understand the distinctive biological mechanisms that allow the beetles to swim and dive, while searching for potential bio-inspired robotics applications. Through static and dynamic measurements obtained using a combination of microscopy and high-speed imaging, parameters associated with the morphology and beating kinematics of the whirligig beetle''s legs in swimming and diving were obtained. Using data obtained from these experiments, dynamics models of both swimming and diving were developed. Through analysis of simulations conducted using these models it was possible to determine several key principles associated with the swimming and diving processes. First, we determined that curved swimming trajectories were more energy efficient than linear trajectories, which explains why they are more often observed in nature. Second, we concluded that the hind legs were able to propel the beetle farther than the middle legs, and also that the hind legs were able to generate a larger angular velocity than the middle legs. However, analysis of circular swimming trajectories showed that the middle legs were important in maintaining stable trajectories, and thus were necessary for steering. Finally, we discovered that in order for the beetle to transition from swimming to diving, the legs must change the plane in which they beat, which provides the force required to alter the tilt angle of the body necessary to break the surface tension of water. We have further examined how the principles learned from this study may be applied to the design of bio-inspired swimming/diving robots.     

Sexual Selection on Accessory Glands, Genitalia and Protarsal Pads in the Whirligig Beetle Dineutus nigrior Roberts (Coleoptera: Gyrinidae)

Sexual selection is a potent force in the evolution of morphology in sexually reproducing species. When large size in a trait is favored by sexual selection the trait often exhibits positive allometry. Mating behavior in whirligig beetles consists of males attempting to grasp reluctant females using enlarged protarsi (protarsal pads). Here we use allometry and a mating experiment to investigate sexual selection pressures on accessory glands, intromittant genitalia (aedeagus), and protarsal pads in males of the whirligig beetle Dineutus nigrior Roberts. Accessory gland size exhibited positive allometry and males with larger accessory glands were more likely to copulate suggesting that larger size in this trait is favored by sexual selection. Males with larger accessory glands attempted to copulate more often but did not exhibit fewer failed mating attempts before copulating. This suggests that the increased probability of mating in males with large accessory glands is due to higher mating attempt frequency and not to increased ability to overcome female resistance. The length of the aedeagus exhibited negative allometry and males with a longer aedeagus did not have increased mating success. This is consistent with stabilizing selection favoring an intermediate size in this trait. The allometric slope of the protarsal pad did not differ from isometry and males with larger protarsal pads did not have increased mating success. This suggests that larger protarsal pads are not favored by sexual selection.     

Neurosecretory cells in the optic lobe of two aquatic coleopteran species,Dineutes indicus aube and Cybister rugulosus redt

In each optic lobe and optic peduncle of two aquatic beetles viz. Dineutes indicus and Cybister rugulosus the neurosecretory cells are observed with the help of various histochemical techniques. These cells are arranged to form a discrete group. A group in the optic lobe of both species contains about 25 to 30 neurosecretory cells. On the basis of staining properties the neurosecretory cells are classified into A and B types. These cells stain with chrome haematoxylin-phloxine and paraldehyde fuchsin, but do not stain with azan. Histochemically, the neurosecretory material is positive for proteins and shows a negative reaction for 1,2-glycols. The cells show variations in RNA contents in correlation with the state of secretory activity. Axons of the neurosecretory cell group of the optic lobe are observed directed to the optic peduncle. The axonal tract from neurosecretory cells in the optic peduncle runs towards the lateral margin of the brain.     

Embryonic development of a whirligig beetle,Dineutus mellyi,with special reference to external morphology (insecta: Coleoptera,Gyrinidae)

The egg morphology and successive changes of developing embryos of the whirligig beetle, Dineutus mellyi (Adephaga: Gyrinidae) are described from observations based on light and scanning electron microscopy. The egg surface is characterized by minute conical projections covering the entire egg surface, a stalk‐like micropylar projection at the anterior pole of the egg, and a longitudinal split line along which the chorion is cleaved during the middle embryonic stages. The germ band or embryo is formed on the ventral egg surface, and develops on the surface throughout the egg period; thus, the egg is a superficial type, as is the case in most coleopteran species. A pair of lateral tracheal gills (LTGs) of the first abdominal segment originates from appendage‐like projections arising at the lateral side of pleuropodia, and the LTGs of the second to ninth abdominal segments are arranged in a row with that of the first segment. Therefore, LTGs are structures with serial homology. The paired dorsal tracheal gills (DTGs) of the ninth abdominal segment are formed on the regions just latero‐dorsal to the LTGs of this segment. Regarding the pleuropodia as the structures being homologous with thoracic legs, neither the LTGs nor DTGs are homologous with thoracic legs, but originate in the more lateral region corresponding to the future pleura of the thoracic segments. The last (10th) abdominal segment in the larva is formed by the fusion of the embryonic 10th and 11th abdominal segments. Four terminal hooks at the end of the last abdominal segment originate from two pairs of swellings on the posterior end of the embryonic 11th abdominal segment. It is proposed that the terminal hooks possibly correspond to the claws of medially fused cerci of the embryonic 11th abdominal segment. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.     

适应性突变的遗传学特征

基于大肠杆菌FC40菌株的研究结果表明,适应性突变依赖RecBCD重组途径的酶,要求SOS反应的部分基因功能,lac+回复突变序列都是在单核苷酸短重复序列处的一个碱基缺失。有证据表明有的适应性突变来自一个或多个暂时性的超突变的细胞亚群,它们的基因组发生大量的突变,转座子高频丢失。产生这种暂时性的超突变的增变子可能是因为细胞的MMR活性暂时不足,或是因错误翻译产生丧失了校读活性的DNA聚合酶III。其他一些研究系统虽然得到了一些同FC40菌株不一致的结论,但所有实验证据都表明,在饥饿等环境胁迫因子作用下,非生长或缓慢生长的细胞可以产生突变,这种突变具有生长依赖的自发突变所不同的一些遗传学特征。 Abstract:The research based on the Escherichia coli FC40 showed that adaptive mutations required the enzymes of RecBCD recombination pathway and some unknown proteins of SOS response,and the mutation spectrum of lac+ revertants is single-base deletions in the small mononucleotide repeats.Some evidence showed that the revertants with adaptive mutations partly come from one (or some) subset of transient hypermutable subpopulation of cells,in which high frequently losing of transposons and genome-wide mutations were observed.It was suggested that this kind of transient hypermutability may be due to the transient deficient activity of mismatch repair (MMR) system,or a defective epsilon unit of DNA polymerase III generated by mistranslation.Although other systems demonstrated some different mechanisms from FC40,all research works suggested that,adaptive mutations occurred in nondividing or nongrowing cells under environmental stresses,for example,starvation,displayed different genetic features from growth-dependent spontaneous mutation.     

Morphological variation in Gyrinus sericeolimbatus Rég. in New Guinea and description of a new Gyrinus species (Coleoptera: Gyrinidae)

Abstract. Samples of Gyrinus sericeolimbatus from twenty-six localities in New Guinea vary greatly in metric body characters as well as in elytral reticulation patterns. The variation is smaller within than between populations. Although the characters of adjacent populations are usually similar, certain proximate populations exhibit significant differences, probably resulting from some kind of dispersal barrier. Similarities between populations at comparable latitudes suggest that some of the morphological variation is altitude-related. In addition, evidence is found for habitat-related morphological differentiation. Changes in phenotypes in response to possible environmental factors in ontogeny and constraints imposed by various selection pressures are discussed.
A new species, G.brincki sp.n., from western New Guinea is described.