Lucanidae Research Articles

A new species of the genus Prismognathus Motschulsky (Coleoptera: Lucanidae) from Yunnan, China

A new species of stag beetle, Prismognathus helii sp. nov., which has a distinct notch on each ultimate antennomere, is described from Yunnan Province, China. Colour plates are presented to illustrate its diagnostic characters.

Fight or flight alternative mating tactics may explain the iconic male polymorphism of the European stag beetle

The existence of different male morphologies within a single species is associated with alternative mating tactics across different animal groups, offering textbook examples of evolutionary biology. The European stag beetle Lucanus cervus is a flagship species which has long fascinated naturalists for its charismatic appearance and behavior, with males possessing large mandibles used in ritualized ground fights for females. Males are polymorphic, with larger males possessing disproportionately larger mandibles and being better fighters, while smaller males require less food to develop and may have better chances to escape predation. We discovered an alternative mating tactic that opens a new interpretation on the evolution of the smaller males, based on aggregations of flying males competing to catch flying females in mid-air. Flight aggregations occur earlier in the season and in sites with sparser canopy cover as compared to ground fight aggregations, but most importantly, smaller males tend to prevail due to their greater agility in flight. Competition between males is crucial for reproductive success in this species, and alternative mating tactics involving flight were unknown in beetles, advocating for further research on the ecology and evolution of the iconic male polymorphism of stag beetles.

Energetically costly weaponry in the large morph of male stag beetles

AbstractMales of many species develop disproportionately large weapons, and frequently the weapon size increases more quickly with body size in small than in large males—a trend often considered to result from the depletion of developmental resources limiting male weapon exaggeration. Based on the cost‐minimization hypothesis, a shallower weapon‐body size allometric slope in large than in small males could be selected for if the energetic maintenance costs of having oversized weapons increase faster in large than in small males. Whether males of different size groups that differ in the weapon‐body size allometric relationship also differ in the energetic costs of maintaining their weapons has not yet been investigated. Consequently, we studied this using the stag beetle (Cyclommatus mniszechi), in which males are larger in size and have larger mandibles than do females and are divided into two morphs: majors are larger and have longer mandibles than minors. In both male morphs, mandible size increases disproportionately with their body size, but it increases more quickly in minors than in majors. We measured the standard metabolic rate (SMR) of the three types of these beetles (the two male morphs and females) to investigate whether the energetic maintenance cost of carrying weapons differs among them. Body weight explained 80% of the variation in the SMR in the three types of beetles, and SMR increased more quickly with body weight in major males than in minor males or females. Weapon and body size also jointly explained approximately 80% of the variation in the SMR. Whereas SMR increased with body size in all three types of beetles (with a higher rate of increase in major males than in minor males or females), only the major males' SMR increased with weapon size. Overall, being heavier and larger and carrying oversized weapons are energetically costly in major males, something which could constrain the exaggeration of their weapons.

Flexible endoscopic treatment of Zenker's diverticulum-a retrospective, observational multicenter study.

The European Society of Gastroenterology and Endoscopy recommends a primarily flexible endoscopic approach for the treatment of Zenker's diverticulum. Due to the rarity of the disorder, evidence for its effectiveness and safety comes mainly from small, retrospective, single-center studies. In this retrospective, observational, multicenter cohort study, data from six German tertiary referral centers were analyzed. The primary outcome parameters were technical and clinical success; among the secondary outcomes, the rates of adverse events (AE) and re-admission with symptomatic recurrence and mortality were the most relevant. Between 2003 and 2024, 384 treatments were performed in 327 patients (61.8% male, mean age 74.70 (± 10.60)). Incision methods/techniques were 250 needle knives, 44 ESD knives, 64 stag beetle knives, 24 staplers, one APC-probe, and one Z-POEM. The Zenker's diverticulum overtube was used in 65.1%, prophylactic clipping in 30.2%, and antibiotic therapy in 25.3% of treatments. The rates of technical and clinical success were 99.2% and 97.4%, and the rates of AE and re-admission with symptomatic recurrence were 11.2% and 16.7%, respectively. Mortality was 0.3%. Comparative subgroup analyses of 312 diverticula without prior treatment versus 72 symptomatic recurrences and incision methods/techniques showed no significant differences in outcome parameters. The use of additional devices and prophylactic measures (clipping, antibiotic therapy) were not independent predictors of technical/clinical success or AE in uni-/multivariable regression analysis. Flexible endoscopic Zenker's diverticulotomy is a safe and effective minimally invasive treatment. Recurrences can be treated by flexible endoscopy with comparable results. None of the cutting methods, ancillary devices, or prophylactic measures showed superiority in effectiveness or safety.

Recent Southern Hemisphere Lamprimine Stag Beetle in Cretaceous Burmese Amber and Its Biogeographic Implications (Coleoptera: Lucanidae).

A new stag beetle fossil, Prostreptocerus burmiticus Yu & Cai gen. et sp. nov., is described based on a single male specimen. This is the first representative of the subfamily Lampriminae (Coleoptera: Scarabaeoidea: Lucanidae) from mid-Cretaceous Burmese amber. The new species is distinctive among Lucanidae due to its well-developed, right-angled mandible, frons featuring a pair of large protuberances, a coarse and sparsely punctate elytral disc, and large tubercles on the humeri. Prostreptocerus Yu & Cai is placed within Lampriminae based on several key characteristics. Morphologically, it is most similar to the extant Streptocerus Fairmaire, 1850. The current distribution of Streptocerus and Lampriminae is primarily restricted to the Southern Hemisphere, suggesting that this lineage is ancient and existed on Gondwanaland, which has significant geographical implications. This discovery extends the fossil record of Lampriminae and provides additional evidence for the existence of sexual dimorphism and potential combat behavior in Mesozoic lucanids. Additionally, Electraesalopsis Bai, Zhang & Qiu, 2017, previously placed as Lucanidae incertae sedis, shares many characteristics with Prostreptocerus Yu & Cai and is also assigned to Lampriminae based on a suite of traits.

Induction of male-like mandibles in XX individuals of a stag beetle by gene knockdown of a feminizer gene transformer.

Males and females share most of the genome, but many animals show different phenotypes between the sexes, known as sexual dimorphism. Many insect species show extreme sexual dimorphism, including beetles with "weapon traits" represented by extremely developed horns and mandibles. Existing studies of sex-specific development of beetle weapon traits suggest that sex-specific gene expression plays an important role. On the other hand, contributions of the Y-chromosome, which may potentially carry genes necessary for male development, to weapon trait expression have not been examined. In holometabolous insects, including beetles, the feminizing gene transformer (tra) is roughly conserved in its feminizing function. Only females express a functional isoform of Tra, which causes female differentiation. Knocking down tra in females leads to male tissue differentiation, enabling us to analyze male phenotypes in individuals lacking a Y-chromosome (XX-males). In this study, we investigate whether the Y-chromosome is necessary for stag beetles to express male-specific weapon traits by comparing tra-knockdown-induced XX-males with natural XY males. We show that XX-males could express weapons (enlarged mandibles) as in XY-males. These results suggest that the Y-chromosome does not have a major role in weapon trait expression in this species.

A chromosomal-level genome assembly of Serrognathus titanus Boisduval, 1835 (Coleoptera: Lucanidae)

The Stag beetle (Coleoptera: Lucanidae) is a fascinating group, often considered one of the most primitive within the Scarabaeoidea. They are valuable models for studying beetle evolution. However, the lack of high-quality genomes hinders our understanding of the evolution and ecology of Lucanidae. In this study, we present a chromosome-level genome of Serrognathus titanus by combining PacBio HiFi long reads, Illumina short reads, and Hi-C data. The genome spans 384.07 Mb, with a scaffold N50 size of 75.81 Mb, and most contigs (97.45%, 374.30 Mb) were anchored into six chromosomes. Our BUSCO analysis of the assembly indicates a completeness of 97.6% (n = 1,367), with 92.8% single-copy BUSCOs and 4.8% duplicated BUSCOs identified. Additionally, we found that the genome contains 43.87% (168.50 Mb) repeat elements and identified 14,263 predicted protein-coding genes. The high-quality genome of S. titanus provides valuable genomic information for comprehending the evolution and ecology of Lucanidae.

Study of the influence of macro-structure and micro-structure on the mechanical properties of stag beetle upper jaw

Macrostructural control of stress distribution and microstructural influence on crack propagation is one of the strategies for obtaining high mechanical properties in stag beetle upper jaws. The maximum bending fracture force of the stag beetle upper jaw is approximately 154, 000 times the weight of the upper jaw. Here, we explore the macro and micro-structural characteristics of two stag beetle upper jaws and reveal the resulting differences in mechanical properties and enhancement mechanisms. At the macroscopic level, the elliptic and triangular cross-sections of the upper jaw of the two species of stag beetles have significant effects on the formation of cracks. The crack generated by the upper jaws with a triangular section grows slowly and deflects easily. At the microscopic level, the upper jaw of the two species is a chitin cross-layered structure, but the difference between the two adjacent fiber layers at 45° and 50° leads to different deflection paths of the cracks on the exoskeleton. The mechanical properties of the upper jaw of the two species of stag beetle were significantly different due to the interaction of macro-structure and micro-structure. In addition, a series of bionic samples with different cross-section geometries and different fiber cross angles were designed, and mechanical tests were carried out according to the macro-structure and micro-structure characteristics of the stag beetle upper jaw. The effects of cross-section geometry and fiber cross angle on the mechanical properties of bionic samples are compared and analyzed. This study provides new ideas for designing and optimizing highly loaded components in engineering. Statement of significanceThe upper jaw of the stag beetle is composed of a complex arrangement of chitin and protein fibers, providing both rigidity and flexibility. This structure is designed to withstand various mechanical stresses, including impacts and bending forces, encountered during its burrowing activities and interactions with its environment. The study of the upper jaw of the stag beetle can provide an efficient structural design for engineering components that are subjected to high loads. Understanding the relationship between structure and mechanical properties in the stag beetle upper jaw holds significant implications for biomimetic design and engineering.

A chromosome-level genome assembly of Prosopocoilus inquinatus Westwood, 1848 (Coleoptera: Lucanidae)

Lucanidae (Coleoptera: Scarabaeidae) are fascinating beetles exhibiting significant dimorphism and are widely used as beetle evolutionary study models. However, lacking high-quality genomes prohibits our understanding of Lucanidae. Herein, we proposed a chromosome-level genome assembly of a widespread species, Prosopocoilus inquinatus, combining PacBio HiFi, Illumina, and Hi-C data. The genome size reaches 649.73 Mb, having the scaffold N50 size of 59.50 Mb, and 99.6% (647.13 Mb) of the assembly successfully anchored on 12 chromosomes. The BUSCO analysis of the genome exhibits a completeness of 99.6% (n = 1,367), including 1,362 (98.5%) single-copy BUSCOs and 15 (1.1%) duplicated BUSCOs. The genome annotation identifies that the genome contains 61.41% repeat elements and 13,452 predicted protein-coding genes. This high-quality Lucanidae genome provides treasured genomic information to our knowledge of stag beetles.

Evaluating log piles as stag beetle conservation measure

Evaluating log piles as stag beetle conservation measure

Colophon scholtzi sp. nov.: a newly described highly threatened stag beetle (Coleoptera: Lucanidae) from South Africa

Colophon scholtzi sp. nov.: a newly described highly threatened stag beetle (Coleoptera: Lucanidae) from South Africa

Introduced mammalian predators influence demography and trait variation of a New Zealand stag beetle

Most species co-evolve with their predators and develop strategies to avoid predation. This is not possible when a novel predator invades an environment. Native residents must quickly adapt to their new predator or face local extinction. Intense competition for mating opportunities exerts significant selective pressure that can drive the evolution of exaggerated structures across taxa. However, these elaborate traits can elevate the risk of predation for some organisms. In the present study, we observe the effect that rats have had on a population of endemic New Zealand stag beetles, Geodorcus helmsi. Rats in Rakiura | Stewart Island often prey on stag beetles, taking them to a sheltered area to eat them and discard any uneaten parts of the beetle, namely the head and mandibles. We compared the head size, mandible size and numbers of predated and non-predated male and female beetles in three sites in Rakiura | Stewart Island that differ in their abundance of mammalian predators. We found that the population demography and the size of the beetles differed significantly between sites. Additionally, we determined whether predated beetles were larger than non-predated beetles, across multiple years, regardless of site. We found that overall the predated specimens were larger than the non-predated beetles. The trends found here suggest that exaggeration of the male mandibles increases the predation risk of these iconic beetles, acting as a limit to mandible size.Implications for insect conservationOur results show for the first time the effect that novel predators can have on a population of animals with exaggerated sexually selected traits. The presence of novel predators can cause a shift in both population demography and trait distribution.

The first mitogenomic phylogenetic framework of Dorcus sensu lato (Coleoptera: Lucanidae), with an emphasis on generic taxonomy in Eastern Asia

BackgroundDorcus stag beetles in broad sense are one of the most diverse group in Lucanidae and important saproxylic insects playing a crucial role in nutrient recycling and forest biomonitoring. However, the dazzling morphological differentiations have caused numerous systematic confusion within the big genus, especially the puzzlingly generic taxonomy. So far, there is lack of molecular phylogenetic study to address the chaotic situation. In this study, we undertook mitochondrial genome sequencing of 42 representative species including 18 newly-sequenced ones from Eastern Asia and reconstructed the phylogenetic framework of stag beetles in Dorcus sensu lato for the first time.ResultsThe mitogenome datasets of Dorcus species have indicated the variable mitogenomic lengths ranged from 15,785 to 19,813 bp. Each mitogenome contained 13 PCGs, 2 rRNAs, 22 tRNAs, and a control region, and all PCGs were under strong purifying selection (Ka/Ks < 1). Notably, we have identified the presence of a substantial intergenic spacer (IGS) between the trnAser (UCN) and NAD1 genes, with varying lengths ranging from 129 bp (in D. hansi) to 158 bp (in D. tityus). The mitogenomic phylogenetic analysis of 42 species showed that Eastern Asia Dorcus was monophyletic, and divided into eight clades with significant genetic distance. Four of them, Clade VIII, VII, VI and I are clustered by the representative species of Serrognathus Motschulsky, Kirchnerius Schenk, Falcicornis Séguy and Dorcus s.s. respectively, which supported their fully generic positions as the previous morphological study presented. The topology also showed the remaining clades were distinctly separated from the species of Dorcus sensu lato, which implied that each of them might demonstrate independent generic status. The Linnaeus nomenclatures were suggested as Eurydorcus Didier stat. res., Eurytrachellelus Didier stat. res., Hemisodorcus Thomson stat. res. and Velutinodorcus Maes stat. res. For Clade V, IV, III and II respectively.ConclusionThis study recognized the monophyly of Dorcus stag beetles and provided a framework for the molecular phylogeny of this group for the first time. The newly generated mitogenomic data serves as a valuable resource for future investigations on lucanid beetles. The generic relationship would facilitate the systematics of Dorcus stag beetles and thus be useful for exploring their evolutionary, ecological, and conservation aspects.

Investigation of Fungal Community Structure in the Gut of the Stag Beetle Dorcus hopei (Coleoptera; Lucanidae): Comparisons Among Developmental Stages

Stag beetles, recognized as common saproxylic insects, are valued for their vibrant coloration and distinctive morphology. These beetles play a crucial ecological role in decomposition and nutrient cycling, serving as a vital functional component in ecosystem functioning. Although previous studies have confirmed that stag beetles are predominantly fungivores, the fluctuations in their intestinal fungal communities at different developmental stages remain poorly understood. In the current study, high-throughput sequencing was employed to investigate the dynamic changes within intestinal fungal communities at various developmental stages in the stag beetle Dorcus hopei. Results showed that microbial diversity was higher during the larval stage than during the pupal and adult stages. Furthermore, significant differences were identified in the composition of the intestinal fungal communities across the larval, pupal, and adult stages, suggesting that developmental transitions may be crucial factors contributing to variations in fungal community composition and diversity. Dominant genera included Candida, Scheffersomyces, Phaeoacremonium, and Trichosporon. Functional predictions indicated a greater diversity and relative abundance of endosymbiotic fungi in the larval gut, suggesting a potential dependency of larvae on beneficial gut fungi for nutrient acquisition. Additionally, the application of abundance-based β-null deviation and niche width analyses revealed that the adult gut exerted a stronger selection pressure on its fungal community, favoring certain taxa. This selection process culminates in a more robust co-occurrence network of fungal communities within the adult gut, thereby enhancing their adaptability to environmental fluctuations. This study advances our understanding of the intestinal fungal community structure in stag beetles, providing a crucial theoretical foundation for the development of saproxylic beetle resources, biomass energy utilization, plastic degradation strategies, and beetle conservation efforts.

First fossil record of false stag beetles (Coleoptera: Scarabaeoidea: Diphyllostomatidae): Evolutionary and biogeographical implications

The monogeneric scarabaeoid family Diphyllostomatidae contains only three extant false stag beetle species, all of which are restricted to California, USA. In this study, a fossil specimen newly found in mid-Cretaceous Kachin amber of northern Myanmar is putatively assigned to this family, here described as Prodiphyllostoma inexpectatum gen. et sp. nov. The discovery of this rare scarabaeoid as a Mesozoic amber inclusion from Myanmar is significant in consideration of the paleobiogeography and evolutionary history of this family.

The mitochondrial genome of a carnivorous lucanid, Figulus punctatus Waterhouse, 1873 (Coleoptera: Lucanidae)

This study represents the first report of the complete mitochondrial genome of a carnivorous stag beetle, Figulus punctatus. The genome is 17,664 bp long with a total of 37 genes including 13 protein-coding genes, 22 tRNA, and 2 rRNA. The nucleotide composition is 37.25% A, 31.71% T, 10.00% G, and 20.99% C (GC contents 30.99%). Our molecular phylogenetic analysis based on the maximum-likelihood method recognizes Figulini and Nigidiini as a monophyletic clade, with a robust support value, and suggests that their carnivorous feeding trait may have evolved once within the family.

The first chromosome-level genome of the stag beetle Dorcus hopei Saunders, 1854 (Coleoptera: Lucanidae)

Stag beetles (Coleoptera: Lucanidae) represent a significant saproxylic assemblage in forest ecosystems and are noted for their enlarged mandibles and male polymorphism. Despite their relevance as ideal models for the study of exaggerated mandibles that aid in attracting mates, the regulatory mechanisms associated with these traits remain understudied, and restricted by the lack of high-quality reference genomes for stag beetles. To address this limitation, we successfully assembled the first chromosome-level genome of a representative species Dorcus hopei. The genome was 496.58 Mb in length, with a scaffold N50 size of 54.61 Mb, BUSCO values of 99.8%, and 96.8% of scaffolds anchored to nine pairs of chromosomes. We identified 285.27 Mb (57.45%) of repeat sequences and annotated 11,231 protein-coding genes. This genome will be a valuable resource for further understanding the evolution and ecology of stag beetles, and provides a basis for studying the mechanisms of exaggerated mandibles through comparative analysis.

The genome sequence of the lesser stag beetle, Dorcus parallelipipedus (Linnaeus, 1758).

We present a genome assembly from an individual male Dorcus parallelipipedus (the lesser stag beetle; Arthropoda; Insecta; Coleoptera; Lucanidae). The genome sequence is 470.9 megabases in span. Most of the assembly is scaffolded into 10 chromosomal pseudomolecules, including the X and Y sex chromosomes. The mitochondrial genome has also been assembled and is 18.19 kilobases in length.

Genetic diversity and population structure of the endangered saproxylic beetle L. cervus in a fragmented landscape

Abstract Despite the significance of saproxylic beetle species for ecosystems, the investigation of fine‐scale population genetics within the stag beetle, Lucanus cervus, remains notably limited. Because of their limited dispersal distances and habitat fragmentation, high genetic structure and low genetic diversity are expected in its populations. To evaluate the impact of habitat fragmentation on genetic diversity and structure, we examined 150 specimens of L. cervus from three sites in western Poland: two forest stands and one stand located in an Oak avenue. We utilised 19 microsatellite DNA loci for this examination. Results of neighbour‐joining analysis and principal coordinates analysis, values of differentiation indexes (G'ST, D(Jost) and FST) and rare/private allele frequencies indicated weak genetic differentiation among individuals collected from the tree sites. A spatial component to the genetic structure was identified through STRUCTURE (LOCPRIOR), isolation by distance tests and spatial autocorrelation analysis. The genetic diversity remained relatively high (HE: 0.49–0.51), with no inbreeding observed and no significant differences in mean relatedness among individuals from sampling sites. Limited genetic differentiation between the individuals of L. cervus from the investigated sites may result from a lag time since fragment isolation, unrestricted gene flow and marker/sample size limitations. Though weak, the significant differentiation between two of the sites may be linked to environmental differences and distance. Genetic data support treating individuals from forests as a single management unit. Non‐invasive sampling suffices for genetic studies, but achieving balanced sampling is crucial for precise historical demography estimates of endangered species.

Adhesion and shrinkage transform the rounded pupal horn into an angular adult horn in Japanese rhinoceros beetle.

Clarifying the mechanisms underlying shape alterations during insect metamorphosis is important for understanding exoskeletal morphogenesis. The large horn of the Japanese rhinoceros beetle Trypoxylus dichotomus is the result of drastic metamorphosis, wherein it appears as a rounded shape during pupation and then undergoes remodeling into an angular adult shape. However, the mechanical mechanisms underlying this remodeling process remain unknown. In this study, we investigated the remodeling mechanisms of the Japanese rhinoceros beetle horn by developing a physical simulation. We identified three factors contributing to remodeling by biological experiments - ventral adhesion, uneven shrinkage, and volume reduction - which were demonstrated to be crucial for transformation using a physical simulation. Furthermore, we corroborated our findings by applying the simulation to the mandibular remodeling of stag beetles. These results indicated that physical simulation applies to pupal remodeling in other beetles, and the morphogenic mechanism could explain various exoskeletal shapes.