Studies on trematode metacercariae infecting libellulid larvae from the Western Ghats, Wayanad region

Understanding the host specificity of trematode larvae is vital in predicting the mode of trophic level transfer of trematode parasites and their evolution. In this study, six species of trematode metacercariae, Eumegacetes sp., Orthetrotrema monostomum, Ganeo tigrinus, Mehraorchis sp., Pleurogenoides sp. and Phyllodistomum sp. infecting the larvae of the odonate family Libellulidae from the water bodies in the Wayanad region of the Western Ghats are recorded. The prevalence of infection of these metacercariae was 5.8%, 2.0%, 10.4%, 9.1%, 2.6% & 1.3%, respectively. Further, the mean intensity of infection was estimated to be 4.44, 1.67, 5.38, 6.21, 6.0 & 17.5 and the mean abundance 0.26, 0.03, 0.56, 0.56, 0.16 & 0.23 respectively.

Characterization and phylogenetic analysis of the complete mitochondrial genome of Neurothemis fulvia (Odonata: Anisoptera: Libellulidae)

Neurothemis fulvia is a dragonfly of wet forests and usually perches on fallen logs and shrubs. In this study, we sequenced and analyzed the complete mitochondrial genome (mitogenome) of N. fulvia. This mitogenome was 15,459 bp long and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and 2 ribosomal RNA unit genes (rRNAs). The nucleotide composition of the mitogenome was biased toward A and T, with 70.5% of A + T content (A 38.8%, T 31.7%, C 16.6%, and G 12.9%). Gene order was conserved and identical to most other previously sequenced Libellulidae dragonflies. Most PCGs of N. fulvia have the conventional start codons ATN (six ATG, three ATT, and two ATC), with the exception of cox1 and nad1 (TTG). Except for four PCGs (cox1, cox2, cox3, and nad5) end with the incomplete stop codon T––, all other PCGs terminated with the stop codon TAA or TAG. Phylogenetic analysis showed that N. fulvia got together with Tramea virginia with high support value. Libellulidae had a close relationship with Corduliidae, the relationships ((Hydrobasileus + Brachythemis) + (Orthetrum + (Acisoma + (Neurothemis + Tramea)))) were supported in Libellulidae.

Characterization and phylogenetic analysis of the complete mitochondrial genome of Pseudothemis zonata (Odonata: Anisoptera: Libellulidae)

Pseudothemis zonata is a commonly seen dragonfly with a big yellow or white ringlike spot on the third and fourth segments of its abdomen. In this study, we sequenced and analyzed the complete mitochondrial genome (mitogenome) of P. zonata. This mitogenome was 15,434 bp long and encoded 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and 2 ribosomal RNA unit genes (rRNAs). Gene order was conserved and identical to most other previously sequenced Libellulidae dragonflies. The whole mitogenome exhibited heavy AT nucleotide bias (74.6%). Most PCGs of P. zonata have the conventional start codons ATN (six ATG, three ATT, and two ATC), with the exception of cox1 and nad1 (TTG). Except for four genes (cox1, cox2, cox3, and nad5) end with the incomplete stop codon T−, all other PCGs terminated with the stop codon TAA or TAG. Phylogenetic analysis showed that P. zonata got together with Brachythemis contaminata with high support value, and the relationships ((Brachythemis + Psolodesmus) + ((Hydrobasileus + Trigomphus) + (Orthetrum + Acisoma))) were supported in Libellulidae.

Phylogeny of Libellulidae (Odonata: Anisoptera): comparison of molecular and morphology-based phylogenies based on wing morphology and migration

Background

Establishing the species limits and resolving phylogenetic relationships are primary goals of taxonomists and evolutionary biologists. At present, a controversial question is about interspecific phylogenetic information in morphological features. Are the interspecific relationships established based on genetic information consistent with the traditional classification system? To address these problems, this study analyzed the wing shape structure of 10 species of Libellulidae, explored the relationship between wing shape and dragonfly behavior and living habits, and established an interspecific morphological relationship tree based on wing shape data. By analyzing the sequences of mitochondrial COI gene and the nuclear genes 18S, 28S rRNA and ITS in 10 species of dragonflies, the interspecific relationship was established.

Method

The wing shape information of the male forewings and hindwings was obtained by the geometric morphometrics method. The inter-species wing shape relationship was obtained by principal component analysis (PCA) in MorphoJ1.06 software. The inter-species wing shape relationship tree was obtained by cluster analysis (UPGMA) using Mesquite 3.2 software. The COI, 18S, ITS and 28S genes of 10 species dragonfly were blasted and processed by BioEdit v6 software. The Maximum Likelihood(ML) tree was established by raxmlGUI1.5b2 software. The Bayes inference (BI) tree was established by MrBayes 3.2.6 in Geneious software.

Results

The main difference in forewings among the 10 species of dragonfly was the apical, radial and discoidal regions dominated by the wing nodus. In contrast, the main difference among the hindwings was the apical and anal regions dominated by the wing nodus. The change in wing shape was closely related to the ability of dragonfly to migrate. The interspecific relationship based on molecular data showed that the species of Orthetrum genus branched independently of the other species. Compared to the molecular tree of 10 species, the wing shape clustering showed some phylogenetic information on the forewing shape (with large differences on the forewing shape tree vs. molecular tree), and there was no interspecific phylogenetic information of the hindwing shape tree vs. molecular tree.

Conclusion

The dragonfly wing shape characteristics are closely related to its migration ability. Species with strong ability to migrate have the forewing shape that is longer and narrower, and have larger anal region, whereas the species that prefer short-distance hovering or standing still for a long time have forewing that are wider and shorter, and the anal region is smaller. Integrating morphological and molecular data to evaluate the relationship among dragonfly species shows there is some interspecific phylogenetic information in the forewing shape and none in the hindwing shape. The forewing and hindwing of dragonflies exhibit an inconsistent pattern of morphological changes in different species.

Complete mitochondrial genome sequence of Bekko Tombo Libellula angelina Selys, 1883 (Odonata: Libellulidae)

The dragonfly Libellula angelina Selys, 1883 (Odonata: Libellulidae) has been listed as a critically endangered species by the International Union for Conservation of Nature (IUCN) and is also an endangered insect in South Korea. We sequenced the whole genome (15,233 bp) of L. angelina species, which included a set of typical genes and one major non-coding AT-rich region with an arrangement identical to that observed in most insect genomes. The A + T-rich region harbored one identical repeat composed of 65 bp and two tRNA-like structures (trnF and trnK-like sequences) with proper anticodon and clover-leaf structures. Phylogenetic reconstruction using the concatenated sequences of 13 protein-coding genes (PCGs) and two rRNAs of the representative odonate mitogenomes utilizing both Bayesian inference and maximum-likelihood methods revealed a strong support for the monophyletic Zygoptera and a moderate to high support for the monophyletic Anisoptera suborders. Unlike that in conventional phylogenetic analysis, a relatively strong sister relationship was revealed between the suborders of Anisozygoptera and Zygoptera.

Simulated climate change increases larval mortality, alters phenology, and affects flight morphology of a dragonfly

For organisms with complex life cycles, climate change can have both direct effects and indirect effects that are mediated through plastic responses to temperature and that carry over beyond the developmental environment. We examined multiple responses to environmental warming in a dragonfly, a species whose life history bridges aquatic and terrestrial environments. We tested larval survival under warming and whether warmer conditions can create carry-over effects between life history stages. Rearing dragonfly larvae in an experimental warming array to simulate increases in temperature, we contrasted the effects of the current thermal environment with temperatures +2.5°C and +5°C above ambient, temperatures predicted for 50 and 100 years in the future for the study region. Aquatic mesocosms were stocked with dragonfly larvae (Erythemis collocata) and we followed survival of larvae to adult emergence. We also measured the effects of warming on the timing of the life history transition to the adult stage, body size of adults, and the relative size of their wings, an aspect of morphology key to flight performance. There was a trend toward reduced larval survival with increasing temperature. Warming strongly affected the phenology of adult emergence, advancing emergence by up to a month compared with ambient conditions. Additionally, our warmest conditions increased variation in the timing of adult emergence compared with cooler conditions. The increased variation with warming arose from an extended emergence season with fewer individuals emerging at any one time. Altered emergence patterns such as we observed are likely to place individuals emerging outside the typical season at greater risk from early and late season storms and will reduce effective population sizes during the breeding season. Contrary to expectations for ectotherms, body size was unaffected by warming. However, morphology was affected: at +5°C, dragonflies emerging from mesocosms had relatively smaller wings. This provides some of the first evidence that the effects of climate change on animals during their growth can have carry-over effects in morphology that will affect performance of later life history stages. In dragonflies, relatively smaller wings are associated with reduced flight performance, creating a link between larval thermal conditions and adult dispersal capacity.

Cytogenetic Characterization of Eight Odonata Species Originating from the Curonian Spit (the Baltic Sea, Russia) Using C-Banding and FISH with 18S rDNA and Telomeric (TTAGG)n Probes

We studied the karyotypes of 8 dragonfly species originating from the Curonian Spit (the Baltic Sea, Russia) using C-banding and FISH with 18S rDNA and "insect" telomeric (TTAGG)n probes. Our results show that Leucorrhinia rubicunda, Libellula depressa, L. quadrimaculata, Orthetrum cancellatum, Sympetrum danae, and S. vulgatum from the family Libellulidae, as well as Cordulia aenea and Epitheca bimaculata from the family Corduliidae share 2n = 25 (24 + X) in males, with a minute pair of m-chromosomes being present in every karyotype except for that of C. aenea. Major rDNA clusters are located on one of the large pairs of autosomes in all the species. No hybridization signals were obtained by FISH with the (TTAGG)n probe in the examined species with the only exception of S. vulgatum. In this species, clear signals were detected at the ends of almost all chromosomes. This finding raises the possibility that in Odonata the canonical "insect" (TTAGG)n telomeric repeat is in fact present but in very low copy number and is consequently difficult to detect by in situ hybridization. We conclude that more work needs to be done to answer questions about the organization of telomeres in this very ancient and thus phylogenetically important insect order.

Effects of experimental warming on survival, phenology and morphology of an aquatic insect (Odonata)

1. Organisms can respond to changing climatic conditions in multiple ways including changes in phenology, body size or morphology, and range shifts. Understanding how developmental temperatures affect insect life-history timing and morphology is crucial because body size and morphology affect multiple aspects of life history, including dispersal ability, while phenology can shape population performance and community interactions. 2. We experimentally assessed how developmental temperatures experienced by aquatic larvae affected survival, phenology, and adult morphology of dragonflies (Pachydiplax longipennis). Larvae were reared under 3 environmental temperatures: ambient, +2.5 °C, and +5 °C, corresponding to temperature projections for our study area 50 and 100 years in the future, respectively. Experimental temperature treatments tracked naturally-occurring variation. 3. We found clear effects of temperature in the rearing environment on survival and phenology: dragonflies reared at the highest temperatures had the lowest survival rates, and emerged from the larval stage approximately 3 weeks earlier than animals reared at ambient temperatures. There was no effect of rearing temperature on overall body size. Although neither the relative wing nor thorax size was affected by warming, a non-significant trend towards an interaction between sex and warming in relative thorax size suggests that males may be more sensitive to warming than females, a pattern that should be investigated further. 4. Warming strongly affected survival in the larval stage and the phenology of adult emergence. Understanding how warming in the developmental environment affects later life-history stages is critical to interpreting the consequences of warming for organismal performance.