Phylogenetic analysis provides insights into the evolution of Asian fireflies and adult bioluminescence

An Overview of the Firefly Genus Pygoluciola Wittmer, a Phylogeny of the Luciolinae Using Mitochondrial Genomes, a Description of Six New Species, and an Assessment of a Copulation Clamp in This Genus (Coleoptera: Lampyridae: Luciolinae)

Pygoluciola Wittmer 1939 is overviewed, with an expanded generic redescription comprising 28 species, including 6 new species from China, described from features of males, associated females, and larvae. Their placement in the genus is confirmed by a phylogenetic analysis of their mitogenomes. They include Pygoluciola baise Fu & Ballantyne sp. nov. from Baise City, Guangxi Province; P. manmaia Fu & Ballantyne sp. nov. from Yunnan Province; P. quzhou Fu & Ballantyne sp. nov. from the City of Quzhou in Zhejiang Province; P. tunchangia Fu & Ballantyne sp. nov. from Tunchang county, Hainan Island; P. yingjiangia Fu & Ballantyne sp. nov. from Yingjiang county in Yunnan Province; and P. yupingia Fu & Ballantyne sp. nov. from Mt. Yuping, Hongya County in Sichuan Province. Specimens are assigned to Luciola davidis Olivier, which is transferred to Pygoluciola and redescribed. Species are assigned to one of five Groups we define in the genus, and this classification is challenged by molecular information. We reject the possibility of a copulation clamp in P. kinabalua Ballantyne by dissection of pinned type females and comparison with other species newly described here.

Genomics investigation of the potentially invasive firefly Photinus signaticollis Blanchard 1845: Complete mitochondrial genome, multigene phylogenies and obtention of the luciferase and luciferin-regenerating genes

A genomic investigation of the potentially invasive firefly Photinus signaticollis Blanchard1845 has been performed and led to the obtention of its complete 16,411 bp long mitochondrial genome. The mitogenome encodes 13 protein-coding genes, 22 tRNA genes and 2 rRNA genes. With other species of the Photinus complex it shares several premature terminations of some protein-coding genes and also an overlap between cox1 and tRNA-Tyr. By data-mining, the complete luciferase and luciferin-regenerating genes were also identified from the contigs file and compared with existing data, in addition to WG and CAD, two genes used in pioneering phylogenetic studies on fireflies. Three maximum likelihood phylogenies were derived from all these data. The multigene phylogeny based on all mitochondrial protein-coding genes strongly associates P. signaticollis with Photinus pyralis Linnaeus, 1758 and the lantern-less daily "winter firefly", Photinus corruscus Linnaeus, 1767. A second phylogeny based on concatenated sequences of the cox1, WG and CAD genes positions P. signaticollis as a sister clade to a large cluster of species containing the 7 sub-groups previously evidenced among the North American species of the Photinus complex. A third phylogeny based on the amino-acid sequence of the luciferase protein associates P. signaticollis to Photinus scintillans. The analysis presented here will most certainly help to come to a better understanding of the very complex inter-relationships in the very large Photinus genus.

A Mysterious Asian Firefly Genus, Oculogryphus Jeng, Engel & Yang (Coleoptera, Lampyridae): The First Complete Mitochondrial Genome and Its Phylogenetic Implications

The firefly genus Oculogryphus Jeng, Engel & Yang, 2007 is a rare-species group endemic to Asia. Since its establishment, its position has been controversial but never rigorously tested. To address this perplexing issue, we are the first to present the complete mitochondrial sequence of Oculogryphus, using the material of O. chenghoiyanae Yiu & Jeng, 2018 determined through a comprehensive morphological identification. Our analyses demonstrate that its mitogenome exhibits similar characteristics to that of Stenocladius, including a rearranged gene order between trnC and trnW, and a long intergenic spacer (702 bp) between the two rearranged genes, within which six remnants (29 bp) of trnW were identified. Further, we incorporated this sequence into phylogenetic analyses of Lampyridae based on different molecular markers and datasets using ML and BI analyses. The results consistently place Oculogryphus within the same clade as Stenocladius in all topologies, and the gene rearrangement is a synapomorphy for this clade. It suggests that Oculogryphus should be classified together with Stenocladius in the subfamily Ototretinae at the moment. This study provides molecular evidence confirming the close relationship between Oculogryphus and Stenocladius and discovers a new phylogenetic marker helpful in clarifying the monophyly of Ototretinae, which also sheds a new light on firefly evolution.

Firefly toxin lucibufagins evolved after the origin of bioluminescence

Fireflies were believed to originally evolve their novel bioluminescence as warning signals to advertise their toxicity to predators, which was later adopted in adult mating. Although the evolution of bioluminescence has been investigated extensively, the warning signal hypothesis of its origin has not been tested. In this study, we test this hypothesis by systematically determining the presence or absence of firefly toxin lucibufagins (LBGs) across firefly species and inferring the time of origin of LBGs. We confirm the presence of LBGs in the subfamily Lampyrinae, but more importantly, we reveal the absence of LBGs in other lineages, including the subfamilies of Luciolinae, Ototretinae, and Psilocladinae, two incertae sedis lineages, and the Rhagophthalmidae family. Ancestral state reconstructions for LBGs based on firefly phylogeny constructed using genomic data suggest that the presence of LBGs in the common ancestor of the Lampyrinae subfamily is highly supported but unsupported in more ancient nodes, including firefly common ancestors. Our results suggest that firefly LBGs probably evolved much later than the evolution of bioluminescence. We thus conclude that firefly bioluminescence did not originally evolve as direct warning signals for toxic LBGs and advise that future studies should focus on other hypotheses. Moreover, LBG toxins are known to directly target and inhibit the α subunit of Na+, K+-ATPase (ATPα). We further examine the effects of amino acid substitutions in firefly ATPα on its interactions with LBGs. We find that ATPα in LBG-containing fireflies is relatively insensitive to LBGs, which suggests that target-site insensitivity contributes to LBG-containing fireflies' ability to deal with their own toxins.

Cloning and characterization of luciferase from an Asian firefly Pygoluciola qingyu and its comparison with other beetle luciferases

The bioluminescence system of luminescent beetles has extensive applications in biological imaging, protein labeling and drug screening. To explore wild luciferases with excellent catalytic activity and thermal stability, we cloned the luciferase of Pygoluciola qingyu, one species living in areas of high temperature and with strong bioluminescence, by combining transcriptomic sequencing and reverse transcription polymerase chain reaction (RT-PCR). The total length of luciferase gene is 1638 bp and the luciferase consists 544 amino acids. The recombinant P. qingyu luciferase was produced in vitro and its characteristics were compared with those of eight luciferases from China firefly species and two commercial luciferases. Compared with these luciferases, the P. qingyu luciferase shows the highest luminescence activity at room temperature (about 25-28 ℃) with similar KM value for D-luciferin and ATP to the Photinus pyralis luciferase. The P. qingyu luciferase activity was highest at 35 ℃ and can keep high activity at 30-40 ℃, which suggests the potential of P. qingyu luciferase for in vivo and cell application. Our results provide new insights into P. qingyu luciferase and give a new resource for the application of luciferases.

Predatory fireflies and their toxic firefly prey have evolved distinct toxin resistance strategies

Toxic cardiotonic steroids (CTSs) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na+,K+-ATPase (NKA). Although most fireflies produce these toxins internally, species of the genus Photuris acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between Photuris and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication. Our study demonstrates that both Photuris and their firefly prey have evolved highly resistant NKAs. Using an evolutionary analysis of the specific target of CTS (ATPα) in fireflies and gene editing in Drosophila, we find that the initial steps toward resistance were shared among Photuris and other firefly lineages. However, the Photuris lineage subsequently underwent multiple rounds of gene duplication and neofunctionalization, resulting in the development of ATPα paralogs that are differentially expressed and exhibit increasing resistance to CTS. By contrast, other firefly species have maintained a single copy. Our results implicate gene duplication as a facilitator in the transition of Photuris to its distinct ecological role as a predator of toxic firefly prey.

Predatory fireflies and their toxic firefly prey have evolved distinct toxin resistance strategies

Toxic cardiotonic steroids (CTS) act as a defense mechanism in many firefly species (Lampyridae) by inhibiting a crucial enzyme called Na+,K+-ATPase (NKA). While most fireflies produce these toxins internally, species of the genus Photuris acquire them from a surprising source: predation on other fireflies. The contrasting physiology of toxin exposure and sequestration between Photuris and other firefly genera suggests that distinct strategies may be required to prevent self-intoxication. Our study demonstrates that both Photuris and their firefly prey have evolved highly-resistant NKAs. Using an evolutionary analysis of the specific target of CTS (ATPα) in fireflies, and gene-editing in Drosophila, we find that the initial steps towards resistance were shared among Photuris and other firefly lineages. However, the Photuris lineage subsequently underwent multiple rounds of gene duplication and neofunctionalization, resulting in the development of ATPα paralogs that are differentially expressed and exhibit increasing resistance to CTS. In contrast, other firefly species have maintained a single copy. Our results implicate gene duplication as a facilitator in the transition of Photuris to its distinct ecological role as predator of toxic firefly prey.

Complete mitochondrial genome of the Themus foveicollis (Coleoptera: Cantharidae)

The genus Themus Motschulsky, 1858 is one of the largest genera of beetle family Cantharidae, however, no complete mitochondrial genome is available in the public database so far. Here, we sequenced and analyzed the first complete mitochondrial genome of Themus, with T. foveicollis as the representative species. The mitochondrial genome was 16,469 bp in size with 37 genes including 13 protein-coding genes (PCGs), 22 transfer RNA genes, and two ribosomal RNA genes, as well as a non-coding region, which are arranged in the same way as the hypothetical ancestral insect. It exhibited a typical high A + T bias and a higher proportion of bases A and C than T and G (A: 41.1%, T: 37.5%, G: 8.6%, C: 12.9%). The phylogenetic trees of Elateroidea were reconstructed based on 13 PCGs sequences using the Bayesian inference (BI) and maximum-likelihood (ML) analyses to investigate its phylogenetic position. The results showed that Themus was consistently grouped with the remaining genera of Cantharidae and placed in a monophyletic clade of Cantharinae in high supporting values, which are congruent with the morphological classification. The newly sequenced mitochondrial genome in this study constitutes important reference data for reconstructing phylogeny of the family Cantharidae or the superfamily Elateroidea.

Rhagophthalmidae Olivier, 1907 (Coleoptera, Elateroidea): described genera and species, current problems, and prospects for the bioluminescent and paedomorphic beetle lineage

Rhagophthalmidae are a small beetle family known from the eastern Palaearctic and Oriental realms. Rhagophthalmidae are closely related to railroad worms (Phengodidae) and fireflies (Lampyridae) with which they share highly modified paedomorphic females and the ability to emit light. Currently, Rhagophthalmidae include 66 species classified in the following 12 genera: Bicladodrilus Pic, 1921 (two spp.), Bicladum Pic, 1921 (two spp.), Dioptoma Pascoe, 1860 (two spp.), Diplocladon Gorham, 1883 (two spp.), Dodecatoma Westwood, 1849 (eight spp.), Falsophrixothrix Pic, 1937 (six spp.), Haplocladon Gorham, 1883 (two spp.), Menghuoius Kawashima, 2000 (three spp.), Mimoochotyra Pic, 1937 (one sp.), Monodrilus Pic, 1921 (two spp. in two subgenera), Pseudothilmanus Pic, 1918 (two spp.), and Rhagophthalmus Motschulsky, 1854 (34 spp.). The replacement name Haplocladongorhami Kundrata, nom. nov. is proposed for Diplocladonhasseltii Gorham, 1883b (described in subgenus Haplocladon) which is preoccupied by Diplocladonhasseltii Gorham, 1883a. The genus Reductodrilus Pic, 1943 is tentatively placed in Lampyridae: Ototretinae. Lectotypes are designated for Pseudothilmanusalatus Pic, 1918 and P.marginalis Pic, 1918. Interestingly, in the eastern part of their distribution, Rhagophthalmidae have remained within the boundaries of the Sunda Shelf and the Philippines demarcated by the Wallace Line, which separates the Oriental and Australasian realms. This study is intended to be a first step towards a comprehensive revision of the group on both genus and species levels. Additionally, critical problems and prospects for rhagophthalmid research are briefly discussed.

Luminescent characteristics and mitochondrial COI barcodes of nine cohabitated Taiwanese fireflies

Background

Over 50 Taiwanese firefly species have been discovered, but scientists lack information regarding most of their genetics, bioluminescent features, and cohabitating phenomena. In this study, we focus on morphological species identification and phylogeny reconstructed by COI barcoding, as well as luminescent characteristics of cohabited Taiwanese firefly species to determine the key factors that influenced how distinct bioluminescent species evolved to coexist and proliferate within the same habitat.

Methods

In this study, 366 specimens from nine species were collected in northern Taiwan from April to August, 2016-2019. First, the species and sex of the specimens were morphologically and genetically identified. Then, their luminescent spectra and intensities were recorded using a spectrometer and a power meter, respectively. The habitat temperature, relative humidity, and environmental light intensity were also measured. The cytochrome oxidase I (COI) gene sequence was used as a DNA barcode to reveal the phylogenetic relationships of cohabitated species.

Results

Nine species-eight adult species (Abscondita chinensis, Abscondita cerata, Aquatica ficta, Luciola curtithorax, Luciola kagiana, Luciola filiformis, Curtos sauteri, and Curtos costipennis) and one larval Pyrocoelia praetexta-were morphologically identified. The nine species could be found in April-August. Six of the eight adult species shared an overlap occurrence period in May. Luminescent spectra analysis revealed that the λ _max of studied species ranged from 552-572 nm (yellow-green to orange-yellow). The average luminescent intensity range of these species was about 1.2-14 lux (182.1-2,048 nW/cm²) for males and 0.8-5.8 lux (122.8-850 nW/cm²) for females, and the maximum luminescent intensity of males was 1.01-7.26-fold higher than that of females. Compared with previous studies, this study demonstrates that different λ _max, species-specific flash patterns, microhabitat choices, nocturnal activity time, and/or an isolated mating season are key factors that may lead to the species-specific courtship of cohabitated fireflies. Moreover, we estimated that the fireflies start flashing or flying when the environmental light intensity decreased to 6.49-28.1 lux. Thus, based on a rough theoretical calculation, the sensing distance between male and female fireflies might be 1.8-2.7 m apart in the dark. In addition, the mitochondrial COI barcode identified species with high resolution and suggested that most of the studied species have been placed correctly with congeners in previous phylogenies. Several cryptic species were revealed by the COI barcode with 3.27%-12.3% variation. This study renews the idea that fireflies' luminescence color originated from the green color of a Lampyridae ancestor, then red-shifted to yellow-green in Luciolinae, and further changed to orange-yellow color in some derived species.

Systematic review of the firefly genus Emeia Fu, Ballantyne & Lambkin, 2012 (Coleoptera, Lampyridae) from China

The Luciolinae genus Emeia Fu, Ballantyne & Lambkin, 2012 is reviewed. Phylogenetic relationships based on cox1 DNA barcoding sequences from 42 fireflies and 2 outgroup species are reconstructed. The dataset included three main Lampyridae subfamilies: Luciolinae, Photurinae and Lampyrinae, and Emeia was recovered within Luciolinae. A new species, Emeiapulchra Zhu & Zhen sp. nov., is described from the wetland of Lishui, Zhejiang, China. Emeiapulchra is sister species to E.pseudosauteri from Sichuan, which is supported by morphological characters and a phylogeny based on DNA barcoding sequences. The two species are separated geographically as shown on the distribution map. A key to species of Emeia using males is provided.

A chromosome-level genome assembly and intestinal transcriptome of Trypoxylus dichotomus (Coleoptera: Scarabaeidae) to understand its lignocellulose digestion ability

Lignocellulose, as the key structural component of plant biomass, is a recalcitrant structure, difficult to degrade. The traditional management of plant waste, including landfill and incineration, usually causes serious environmental pollution and health problems. Interestingly, the xylophagous beetle, Trypoxylus dichotomus, can decompose lignocellulosic biomass. However, the genomics around the digestion mechanism of this beetle remain to be elucidated. Here, we assembled the genome of T. dichotomus, showing that the draft genome size of T. dichotomus is 636.27 Mb, with 95.37% scaffolds anchored onto 10 chromosomes. Phylogenetic results indicated that a divergent evolution between the ancestors of T. dichotomus and the closely related scarabaeid species Onthophagus taurus occurred in the early Cretaceous (120 million years ago). Through gene family evolution analysis, we found 67 rapidly evolving gene families, within which there were 2 digestive gene families (encoding Trypsin and Enoyl-(Acyl carrier protein) reductase) that have experienced significant expansion, indicating that they may contribute to the high degradation efficiency of lignocellulose in T. dichotomus. Additionally, events of chromosome breakage and rearrangement were observed by synteny analysis during the evolution of T. dichotomus due to chromosomes 6 and 8 of T. dichotomus being intersected with chromosomes 2 and 10 of Tribolium castaneum, respectively. Furthermore, the comparative transcriptome analyses of larval guts showed that the digestion-related genes were more commonly expressed in the midgut or mushroom residue group than the hindgut or sawdust group. This study reports the well-assembled and annotated genome of T. dichotomus, providing genomic and transcriptomic bases for further understanding the functional and evolutionary mechanisms of lignocellulose digestion in T. dichotomus.

The complete mitochondrial genome of the firefly Curtos fulvocapitalis (Coleoptera: Lampyridae)

We report the complete mitochondrial genome of the firefly Curtos fulvocapitalis Jeng et Yang 1998. The circular genome is 16,398 bp and has a base composition of A (42.21%), C (11.22%), G (7.73%), and T (38.85%). Our sequence is similar to those of other metazoans, which contain 13 protein-coding genes. All 13 protein-coding genes were initiated by the ATN (ATT, ATA, and ATG) codon. Nine protein-coding genes stopped with TAA or TAG codons, and the other four genes had an incomplete termination codon, a single T. We sequenced the mitochondrial genome of fireflies to analyze phylogenetic relationships and determine the evolution of their flashing signals.

Fireflies in South East Asia: Species Diversity, Distribution, and Habitat (2015-2021)

Fireflies are one of the most famous luminous insects that emit bioluminescence. The most famous fireflies in Southeast Asia are Pteroptyx , of the order Coleoptera and the Lampyridae family. This review paper combined the data on the species diversity and firefly distribution in Southeast Asian countries such as Malaysia, the Philippines, Indonesia, Cambodia, Myanmar, Singapore, Sri Lanka, Papua New Guinea, Laos, Thailand, and Vietnam published in 2015-2021. Some countries have limited data and no studies to identify firefly species and their habitat from 2015 to 2021; the data before 2015 was used. Furthermore, the lack of studies by Southeast Asian researchers regarding the richness of firefly species has been reviewed. Malaysian and Thailand researchers are among the forerunners in the study related to fireflies in the Southeast Asian region compared to other Southeast Asian countries. Lastly, not much is known about the display trees or habitat of fireflies in many areas such as the Philippines, Indonesia, Cambodia, Myanmar, Singapore, Sri Lanka, Papua New Guinea, Laos, Thailand, and Vietnam. More studies are warranted to be conducted in the future on firefly species and their habitat.

FA-nf: A Functional Annotation Pipeline for Proteins from Non-Model Organisms Implemented in Nextflow

Functional annotation allows adding biologically relevant information to predicted features in genomic sequences, and it is, therefore, an important procedure of any de novo genome sequencing project. It is also useful for proofreading and improving gene structural annotation. Here, we introduce FA-nf, a pipeline implemented in Nextflow, a versatile computational workflow management engine. The pipeline integrates different annotation approaches, such as NCBI BLAST+, DIAMOND, InterProScan, and KEGG. It starts from a protein sequence FASTA file and, optionally, a structural annotation file in GFF format, and produces several files, such as GO assignments, output summaries of the abovementioned programs and final annotation reports. The pipeline can be broken easily into smaller processes for the purpose of parallelization and easily deployed in a Linux computational environment, thanks to software containerization, thus helping to ensure full reproducibility.

Molecular cloning, characterization, and evolution analysis of the luciferase genes from three sympatric sibling fireflies (Lampyridae: Lampyrinae, Diaphanes)

Firefly adult bioluminescence functions as signal communication between sexes. How sympatric sibling species with similar glow pattern recognize their conspecific mates remains largely unknown. To better understand the role of the luciferases of sympatric fireflies in recognizing mates, we cloned the luciferase genes of three sympatric forest dwelling fireflies (Diaphanes nubilus, Diaphanes pectinealis, and Diaphanes sp2) and evaluated their enzyme characteristics. Our data show that the amino acid (AA) sequences of all three luciferases are highly conserved, including the identities (D. nubilus vs D. pectinealis: 99%; D. nubilus vs Diaphanes sp2: 98.5%; D. pectinealis vs Diaphanes sp2: 99.4%) and the protein structures. Three recombinant luciferases produced in vitro all possess significant luminescence activity at pH 7.8, and similar maximum emission spectrum (D. nubilus: 562 nm; D. pectinealis and Diaphanes sp2: 564 nm). They show the highest activity at 10 °C (D. pectinealis, Diaphanes sp2) and 15 °C (D. nubilus), and completely inactivation at 45 °C. Their KM for D-luciferin and ATP were 2.7 μM and 92 μM (D. nubilus), 3.7 μM and 49 μM (D. pectinealis), 3.5 μM and 46 μM (Diaphanes sp2). Phylogenetic analyses support that D. nubilus is sister to D. pectinealis with Diaphanes sp2 at their base, which further cluster with Pyrocoelia. All combined data indicate that sympatric Diaphanes species have similar luciferase characteristics, suggesting that other strategies (e.g., pheromone, active time, etc.) may be adopted to recognize mates. Our data provide new insights into Diaphanes luciferases and their evolution.

Characterization of the complete mitochondrial genome of Abscondita cerata (Olivier, 1911) (Coleoptera: Lampyridae) and its phylogenetic implications

We sequenced and assembled the complete mitochondrial genome of Abscondita cerata from Nankang, Taipei City, Taiwan. The complete mitogenome of A. cerata is 16,964 bp long, and contains 13 protein-coding, 22 tRNA, and two rDNA genes. Nucleotide compositions of the mitogenome of the A. cerata are A: 43.93%, T: 36.74%, C: 11.05%, and G: 8.28%. The AT and GC skewness of the mitogenome sequence are 0.0891 and −0.1434, showing the genome composition skewness toward adenine and cytosine. The clade including all Lampyridae species is well supported. The result indicates that Luciolinae is a monophyletic group but Lampyrinae is not a monophyletic group, as Lamprigera yunnana, which was originally classified into Lampyrinae, is sister to Luciolinae. The genus Lamprigera may share a unique phylogenetic position in Lampyridae. The genus Luciola is a polyphyletic group and the genus Abscondita is a monophyletic group. A. cerata is the sister species to A. chinensis in China. Mitogenomic data from this study will provide useful molecular markers for further studies on the population genetics, speciation, and conservation of endemic species A. cerata in Taiwan.

Characterization of the First Complete Mitochondrial Genome of Cyphonocerinae (Coleoptera: Lampyridae) with Implications for Phylogeny and Evolution of Fireflies

Complete mitochondrial genomes are valuable resources for phylogenetics in insects. The Cyphonoceridae represents an important lineage of fireflies. However, no complete mitogenome is available until now. Here, the first complete mitochondrial genome from this subfamily was reported, with Cyphonocerus sanguineus klapperichi as a representative. The mitogenome of C. sanguineus klapperichi was conserved in the structure and comparable to that of others in size and A+T content. Nucleotide composition was A+T-biased, and all genes exhibited a positive AT-skew and negative GC-skew. Two types of tandem repeat sequence units were present in the control region (136 bp × 2; 171 bp × 2 + 9 bp). For reconstruction of Lampyridae's phylogeny, three different datasets were analyzed by both maximum likelihood (ML) and Bayesian inference (BI) methods. As a result, the same topology was produced by both ML analysis of 13 protein-coding genes and 2rRNA and BI analysis of 37 genes. The results indicated that Lampyridae, Lampyrinae, Luciolinae (excluding Emeia) were monophyletic, but Ototretinae was paraphyletic, of which Stenocladius was recovered as the sister taxon to all others, while Drilaster was more closely related to Cyphonocerinae; Phturinae + Emeia were included in a monophyletic clade, which comprised sister groups with Lampyridae. Vesta was deeply rooted in the Luciolinae.

Genomic and experimental data provide new insights into luciferin biosynthesis and bioluminescence evolution in fireflies

Fireflies are among the most charismatic insects for their spectacular bioluminescence, but the origin and evolution of bioluminescence remain elusive. Especially, the genic basis of luciferin (D-luciferin) biosynthesis and light patterns is largely unknown. Here, we present the high-quality reference genomes of two fireflies Lamprigera yunnana (1053 Mb) and Abscondita terminalis (501 Mb) with great differences in both morphology and luminous behavior. We sequenced the transcriptomes and proteomes of luminous organs of two species. We created the CRISPR/Cas9-induced mutants of Abdominal B gene without luminous organs in the larvae of A. terminalis and sequenced the transcriptomes of mutants and wild-types. Combining gene expression analyses with comparative genomics, we propose a more complete luciferin synthesis pathway, and confirm the convergent evolution of bioluminescence in insects. Using experiments, the function of the firefly acyl-CoA thioesterase (ACOT1) to convert L-luciferin to D-luciferin was validated for the first time. Comparisons of three-dimension reconstruction of luminous organs and their differentially expressed genes among two species suggest that two positive genes in the calcium signaling pathway and structural difference of luminous organs may play an important role in the evolution of flash pattern. Altogether, our results provide important resources for further exploring bioluminescence in insects.

The genetic variations in the mitochondrial genomes of three Luciolinae fireflies

This paper studied the complete mitochondrial genomes of three fireflies, Pygoluciola qingyu, Emeia pseudosauteri and Abscondita terminalis. We discussed the variations in the mitochondrial genomes of samples of each firefly from different populations. The mitochondrial genomes of Abs. terminalis and P. qingyu are very stable among their different populations. The mitochondrial genome of E. pseudosauteri shows some variations among the different populations, especially in the COI sequence.

Complete mitochondrial genome of the Korean endemic firefly, Luciola unmunsana (Coleoptera: Lampyridae)

In this study, we announce the complete mitochondrial genome (mitogenome) of the Korean endemic firefly, Luciola unmunsana Doi, 1931. The full-length circular genome was 15,858 bp, with 77.94% A/T content. It contained the typical set of 37 metazoan genes: 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA) genes, as well as an A + T-rich region. The gene arrangement of the species is identical to that of the ancestral arrangement found in the majority of insects. The maximum-likelihood tree, built using all PCGs and two rRNAs via randomized accelerated maximum likelihood (RAxML) showed that L. unmunsana was grouped as a sister to L. curtithorax with the highest nodal support. However, another Luciola species clustered with the Aquatica species such that the genus Luciola was a non-monophyletic group. Therefore, more sampling is required to clarify the phylogeny of Luciola.

DNA-based species delimitation reveals cryptic and incipient species in synchronous flashing fireflies (Coleoptera: Lampyridae) of Southeast Asia

Synchronous flashing fireflies of the genus Pteroptyx are ubiquitous throughout Southeast Asia, yet fundamental knowledge about their biodiversity is lacking. Recent studies have revealed notable population-level phylogeographical structure within the Pteroptyx tener and P. bearni groups in Malaysia, suggesting that cryptic species may exist. Additionally, morphological and genetic similarities between P. balingiana and P. malaccae have raised questions about the former’s validity as a distinct species. We collected samples from previously unsampled populations and assembled the most comprehensive genetic dataset for Pteroptyx to date, to characterize species boundaries within the P. tener, P. bearni and P. malaccae groups. Using a suite of species delimitation analyses, we show that P. tener along the west coast of Peninsular Malaysia (PM) is distinct from populations from the east coast and Borneo despite the absence of morphological differentiation. However, analyses could not conclusively differentiate P. bearni from Borneo and eastern PM, nor identify P. balingiana and P. malaccae as distinct species, indicating that these populations may be conspecific or represent incipient species. This study underlines the need to increase geographical, taxonomic and genetic sampling of Southeast Asian fireflies to provide a better understanding of their biodiversity.