Cytogenetic analysis of Ctenostomini by C-banding and rDNA localization and its relevance to the knowledge of the evolution of tiger beetles (Coleoptera: Cicindelidae)

In this work, the first cytogenetic data on Neotropical Collyrinae is provided, by way of their karyotypes, C-banding and ribosomal genes (rDNA) localization using fluorescence in situ hybridization (FISH). The two species analysed, Ctenostoma (Procephalus) ornatum ornatum (male) and Ctenostoma (Euctenostoma) rugosum(female) showed, respectively, a diploid number of 17 and 18 chromosomes. C. ornatum ornatum has a multiple sex chromosome system ( n=7 + X₁X₂Y), and mitotic and meiotic metaphase cells showed rDNA gene labelling in the smallest autosomal pair. In this species, no C-bands were obtained, while C. rugosum seems to exhibit centromeric and/or interstitial C-bands in almost all chromosomes. The observation of a multiple sex chromosome system in Ctenostomini ensured the appearance of this characteristic in the hypothetical ancestral of Collyrinae and Cicindelini. The subfamily Collyrinae is not uniform in what concerns diploid chromosome number and rDNA gene localization, because C. ornatum ornatum possesses a lower chromosome number and autosomal rDNA genes when compared with the other Collyrinae species studied ( Neocollyris spp.). Independent events leading to the reduction in chromosome number might have taken place during the split of the Collyrinae into the tribes Ctenostomini and Collyrini.     

Exceptional anoxia resistance in larval tiger beetle, Phaeoxantha klugii (Coleoptera: Cicindelidae)

Abstract. The tiger beetle Phaeoxantha klugii inhabits Central Amazonian floodplains, where it survives the annual inundation period in the third-instar larval stage submerged in the soil at approximately 29 °C for up to 3.5 months. Because flooded soils quickly become anoxic, these larvae should be highly resistant to anoxia. The survival of adult and larval P. klugii was therefore tested during exposure to a pure nitrogen atmosphere in the laboratory at 29 °C. Adult beetles were not resistant (< 6 h). Survival of larvae decreased over time, maximum survival was 15 days, whereas time to 50% mortality was 5.7 days (95% confidence interval 3.8–7.9). Anoxia resistance was additionally tested in third-instar larvae submerged within sediment for 40 days before anoxia exposure in the laboratory. Anoxia resistance was greatly enhanced in these larvae, showing a survival rate of 50% after 26 days of anoxia exposure. It appears that the gradual flooding process and/or the submersion phase induced a physiological alteration, most probably a strong depression in metabolic rate, which requires some days for induction. The degree of anoxia resistance in larval P. klugii is remarkable among terrestrial arthropods worldwide, even more so considering the high ambient temperatures. The species is well-suited to serve as a model organism for studying the physiological mechanisms of anoxia and submersion resistance in terrestrial arthropods inhabiting tropical floodplains.     

Diurnal Tiger Beetles (Coleoptera: Cicindelidae) Capture Prey Without Sight

Although much research has examined the process of prey capture by tiger beetles, an underlying assumption in this work is that tiger beetles are principally, or even exclusively, visual predators. Because this assumption is untested, we performed a series of experiments on four diurnally active tiger beetles in the Genus Cicindela. Individual beetles were placed in chambers in complete darkness and allowed to forage on apterous Drosophila for 6 h. Contrary to expectations, adults of all tested species captured more than 90% of prey items. These results show that other modalities can be used by tiger beetles during prey capture. Beyond potentially providing an explanation for observed night activity in tiger beetle species, the significance of these findings lies in the need to test underlying assumptions of even well-studied organisms.     

Microhabitat and rhythmic behavior of tiger beetle Callytron yuasai okinawense larvae in a mangrove forest in Japan

Mangrove forests are regularly flooded by tides at intervals of approximately 12.4 h (tidal rhythm). Larvae of the tiger beetle Callytron yuasai okinawense in a mangrove forest made shallow burrows in mounds up to 1 m in height constructed by the mud lobster Thalassina anomala. No larval burrows were observed on the forest floor, which was very muddy even during low tide. Some larvae plugged the burrow openings before they were submerged at high tide. The mean interval between consecutive burrow plugging events was 12.37 h, which is similar to the period of tidal cycles. Nine out of 30 larvae plugged the burrow openings even when the burrows did not become submerged. Plugging behavior may be governed by an endogenous biological clock, or may be a response to exogenous information about tidal level (e.g. moisture seeping through the ground).     

Hearing in tiger beetles (Cicindelidae)

ABSTRACT. Tympanic hearing organs (ears) are reported for several tiger beetle (Cicindelidae) species. The paired ears are positioned bilaterally on the first abdominal tergum and consist of cavities covered by thin tympana. When the beetle is not flying the elytra covers its ears and reduces their sensitivity to sound. However, when the beetle is flying, its exposed ears are capable of detecting ultrasonic pulses. Under a microscope, beetles with their elytra artificially raised contract their abdomens in response to ultrasound. Ultrasonic emissions directed toward flying beetles induce them immediately to fly downward and land, a response which probably aids escape from predators, particularly echolocating bats. Other possible uses for the ears are the avoidance of diurnal insect predators and intraspecific communication.     

How slippage-derived sequences are incorporated into rRNA variable-region secondary structure: implications for phylogeny reconstruction

We analyzed the type and frequency of mutational changes in hypervariable rRNA regions, using the highly length-variable region V4 of the small subunit rRNA locus of tiger beetles (Cicindelidae) as an example. Phylogenetic analysis of indels in closely related species showed that (1) most indels are single nucleotides (usually A or T and sometimes G) or di-nucleotides of A and T. These occur at numerous foci, and they exhibit a strong bias for duplication of 5' single and di-nucleotide motifs but not 3' motifs. (2) Insertions/deletions in stem-forming regions affected paired and unpaired bases with about equal frequency but they did not disrupt the secondary structure. (3) Recurring mutations involving short repeats of the same bases caused parallel evolution of similar sequence motifs in the rRNA of different lineages. The observed types of change are consistent with the propostion that slippage is the main mutational mechanism. Slippage-derived sequences tend to be self-complementary, and therefore the stem-loop structure could be self-organizing as a consequence of the underlying mutational mechanism. Thus, the secondary structure in the cicindelid V4 region may be conserved due to the dynamics of the mutational mechanism rather than to functional constraints. These processes may also have a tendency to produce similar primary sequences irrespective of phylogenetic associations. The findings have implications for sequence alignment in phylogenetic analysis and should caution against the use of secondary structure to improve the determination of positional homology in hypervariable regions.     

New Records of Insects Associated with Araucaria Trees: Phytophagous Coleoptera and Hymenoptera and their Natural Enemies

For the recently initiated programs of sustainable forestry with the Brazilian pine, Araucaria angustifolia, knowledge of the insects associated with this tree is of paramount importance. In a forest reserve on the Serra Geral of Rio Grande do Sul, Brazil, a three year monitoring was conducted. Forty coleopteran and 5 hymenopteran species totaling about 6200 specimens were recorded, of which 19 and 4 taxa respectively were previously unknown to live on this conifer. They are the coleopterans Lobopoda dallieri (Alleculidae), Taphroderes sahlbergi (Brentidae), Tithonus virescens (Cerambycidae), Plocamocera sp., Enoclerus sp., sp. indet. (Cleridae), Micromimus sp. (Curculionidae: Cossoninae), Corthylus papulans, Xyleborus catharinensis, Xylechinosomus sp. (Curculionidae: Scolytinae), Dilobitarsus quadrituberculatus, Semiotus intermedius, Ptesimopsia sp. (Elateridae), Eudircaea laticornis, Megapsilaphus sexnotatus (Melandryidae), cf. Copidita sp. (Oedemeridae), Ahasverus sp. (Silvanidae), Temnochila sp., sp. indet. (Trogositidae) and the hymenopterans Eubazus sp. (Braconidae), Ephialtes sp., Epirhyssa cf. celaena, (Ichneumonidae) and Ophrynopus depressatus (Orussidae). Data on their life histories are provided, and also for the coleopterans Taurorcus chabrillacii (Cerambycidae), Araucarius brasiliensis, Eurycorynophorus scabriculus (Curculionidae: Cossoninae), Corthylus praealtus and C. rufopilosus (Curculionidae: Scolytinae) which were already known to occur on Araucaria trees. The results of our survey provide the first records for many insects, especially beetles, as belonging to the araucariofauna. Some of them can be considered potential pest species. Perspectives of applied forest entomology as well as biogeographic aspects are discussed.     

Use of simple remote sensing tools to expedite surveys for rare tiger beetles (Insecta: Coleoptera: Cicindelidae)

Tiger beetles (Insecta: Coleoptera: Cicindelidae) often occupy small patches of suitable habitat in otherwise unsuitable landscapes. Such patches are easily overlooked, which may lead to underestimates of both the number of occurrences and the overall population size. In this study, simple World Wide Web-based tools (Google Earth and Microsoft Terraserver) were used to search high-resolution satellite imagery for patches of suitable habitat for globally and regionally rare tiger beetles on a 3,278 ha wildlife refuge in Maryland, USA. This tract is largely forested but contains scattered small open areas of sand and clay soils that are potential habitat for tiger beetles of conservation concern. Visual inspection of remotely sensed imagery resulted in the identification of 19 potential habitat patches, 15 of which yielded tiger beetle populations when surveyed on the ground. The number of species of tiger beetles recorded from this tract was increased from 3 to 8 and two new sites were discovered for the state sensitive species Cicindela scutellaris rugifrons Dejean. In addition, a small population of C. splendida Hentz was discovered, a species last reported from Maryland in 1948. The technique described here shows great promise for locating small patches of potential tiger beetle habitat in otherwise unsuitable landscapes.