Showing papers by "Rolf G. Beutel published in 2023"
TL;DR: In this article , the authors synthesized the presently available information on the evolution, development, modifications and biological functions of the elytra of Coleoptera, and they postulate that the potential of the Elytra to take over multiple tasks has enormously contributed to the unparalleled diversification of beetles.
Abstract: Conversion of forewings into hardened covers, elytra, was a ground-breaking morphological adaptation that has contributed to the extraordinary evolutionary success of beetles. Nevertheless, the knowledge of the functional aspects of these structures is still fragmentary and scattered across a large number of studies. Here, we have synthesized the presently available information on the evolution, development, modifications and biological functions of this crucial evolutionary novelty. The formation of elytra took place in the earliest evolution of Coleoptera, very likely already in the Carboniferous, and was achieved through the gradual process of progressive forewing sclerotization and the formation of inward directed epipleura and a secluded sub-elytral space. In many lineages of modern beetles, the elytra have been distinctly modified. This includes multiple surface modifications, a rigid connection or fusion of the elytra, or partial or complete reduction. Beetle elytra can be involved in a very broad spectrum of functions: mechanical protection of hind wings and body, anti-predator strategies, thermoregulation and water saving, water harvesting, flight, hind wing folding, diving and swimming, self-cleaning and burrow cleaning, phoresy of symbiotic organisms, mating and courtship, and acoustic communication. We postulate that the potential of the elytra to take over multiple tasks has enormously contributed to the unparalleled diversification of beetles.
2 citations
TL;DR: The Xenos vesparum of the highly specialized Strepsiptera is a new insect model in the context of host-parasite relationships as discussed by the authors , and the endoparasitic female and male secondary larvae were studied using µCT, 3D-reconstructions, histology, and photomicrography.
Abstract: Abstract Xenos vesparum of the highly specialized Strepsiptera is a new insect model in the context of host-parasite relationships.The endoparasitic female and male secondary larvae were studied using µCT, 3D-reconstructions, histology, and photomicrography.The infectious primary larva is followed by a trophic and endoparasitic secondary larval stage. In contrast to immature stages of other holometabolous groups, the second instar increases dramatically in size. Compound eyes and external wing anlagen are present in male larvae before the pupal stage. In contrast to the females, the brain of males bears well-developed optic neuropils and retinula cells are present.The cephalothorax is comparatively simple in the female larvae, yet distinctly more complex than in the adult, where most muscles are reduced. Large testes are present in male larvae and numerous oocytes in the females, but they are still immature.The larval features are discussed in the context of holometabolous development and heterochronic processes. Unique features of Strepsiptera are the early differentiation of the sexes and the occurrence of compound eyes and external wing anlagen in male secondary larvae. The phylogenetic position of Strepsiptera suggests that this is a secondary feature and thus an autapomorphy. To address mature females of Stylopidia as neotenic adults is an oversimplification.They display a mosaic pattern of paedomorphic characters such as features of the nervous system and the presence of stemmata, but also non-paedomorphic structures, such as the spiracles.
1 citations
TL;DR: This article examined the 1st instar larvae of Dilar montanus and found intrinsic antennal muscles and Johnston's organ, the first record of these structures in holometabolous larvae and proved that the first two larval antennomeres are homologous with the scapus and pedicellus.
Abstract: Dilaridae are a distinctive and phylogenetically ambiguous neuropteran family. The anatomy of immature stages was largely unknown so far. We examined the 1st instar larvae of Dilar montanus in detail and present results of live observations for the first time. The minute, cryptic larvae display features correlated with their underground lifestyle, for instance a strongly flattened head, stout antennae, eyelessness, and burrowing forelegs. In contrast to molecular data, several characters suggest a 'dilarid clade' combining Dilaridae with Mantispoidea, for instance a very thin and curved or reduced tentorial bridge, straight and subparallel sucking stylets, and an elongated postmentum. We found intrinsic antennal muscles and Johnston's organ, the first record of these structures in holometabolous larvae. This proves that the first two larval antennomeres are homologous with the scapus and pedicellus. The described characters are discussed and analyzed with an updated matrix of neuropteran larval characters. Alternative scenarios of character evolution are presented. Additionally, we show how the 1st instar larvae move and feed in the substrate, and also a high resolution video record of the function of the elongate tubular ovipositor and the egg-laying behavior in an adult female under natural conditions. This article is protected by copyright. All rights reserved.
TL;DR: In this article , the authors show that traumatic insemination is widespread in Strepsiptera and that it is associated with the injection of sperm in the female's haemocoel.
Abstract:
Traumatic insemination refers to mating in which males pierce the female’s integument with his penis for insemination. Strepsiptera are often listed as an example for this mode of copulation. However, while traumatic insemination in Mengenillidae with free-living females is undisputed, its occurrence in Stylopidia with permanent endoparasitic females – 97% of the known species of Strepsiptera – has remained unclear. Rather, observations from a single study on Xenos vesparum (Xenidae) that questioned traumatic insemination in this species became generalized for Stylopidia. Here we show that integration of data from various imaging methods provides convincing evidence for traumatic insemination being phylogenetically widespread in Strepsiptera. Specifically, we provide the first evidence of injury wounds from traumatic insemination in species of Mengenillidae, Corioxenidae, Elenchidae, Halictophagidae and Xenidae. Using three-dimensional models of copulating pairs of Stylops ovinae (Stylopidae) and X. vesparum, we visualize the physical piercing of the female’s integument by the male’s penis. Finally, we show in species of Mengenillidae, Xenidae and Stylopidae that traumatic mating is associated with the injection of sperm in the female’s haemocoel. Our results significantly alter the understanding of the reproductive biology of Strepsiptera and imply that traumatic insemination has been the ancestral mode of copulation and retained in most, if not all, extant families.
TL;DR: The morphology of the adult free-living females of Mengenilla moldrzyki and Eoxenos laboulbenei (Strepsiptera, Mengenillidae) was documented with µCT-based 3D reconstructions and histological serial sections as mentioned in this paper .
Abstract: The morphology of the adult free‐living females of Mengenilla moldrzyki and Eoxenos laboulbenei (Strepsiptera, Mengenillidae) was documented with µCT‐based 3D reconstructions and histological serial sections. External and internal features of both species are characterized by far‐reaching specialization and structural simplification. The well‐developed mandibles are moved by large muscles. Other mouthparts and their corresponding musculature are simplified or absent. The brain is partly shifted into the prothorax. It is followed by a single postcerebral ganglionic complex also containing the subesophageal ganglion and an unpaired abdominal nerve. Postcephalic sclerites are absent, except for the plate‐like pronotum and small pleural sclerites. Wings and associated muscles are missing. The lumina of the large midgut and the anterior hindgut are disconnected. Seven bulb‐shaped Malpighian tubules in M. moldrzyki is the highest number yet described for Strepsiptera. The 10‐segmented abdomen lacks appendages. An unpaired birth organ opens ventrally on abdominal segment VII. The entire body cavity is filled with numerous freely floating eggs, 1386 in the specimen of M. moldrzyki and 721 in E. laboulbenei. Genital ducts, defined gonads, and genital glands are missing. The morphology of female Mengenillidae is discussed with respect to sexual dimorphism and structural features of the postembryonic stages. Phylogenetic implications are outlined.
TL;DR: In this paper , the authors proposed a Model for Describing Cuticular Anatomical Structures (MoDCAS) which incorporates structural properties and positional relationships for standardized, consistent, and reproducible descriptions of arthropod phenotypes.
Abstract: The spectacular radiation of insects has produced a stunning diversity of phenotypes. During the past 250 years, research on insect systematics has generated hundreds of terms for naming and comparing them. In its current form, this terminological diversity is presented in natural language and lacks formalization, which prohibits computer-assisted comparison using semantic web technologies. Here we propose a Model for Describing Cuticular Anatomical Structures (MoDCAS) which incorporates structural properties and positional relationships for standardized, consistent, and reproducible descriptions of arthropod phenotypes. We applied the MoDCAS framework in creating the ontology for the Anatomy of the Insect Skeleto-Muscular system (AISM). The AISM is the first general insect ontology that aims to cover all taxa by providing generalized, fully logical, and queryable, definitions for each term. It was built using the Ontology Development Kit (ODK), which maximizes interoperability with Uberon (Uberon multi-species anatomy ontology) and other basic ontologies, enhancing the integration of insect anatomy into the broader biological sciences. A template system for adding new terms, extending, and linking the AISM to additional anatomical, phenotypic, genetic, and chemical ontologies is also introduced. The AISM is proposed as the backbone for taxon-specific insect ontologies and has potential applications spanning systematic biology and biodiversity informatics, allowing users to (1) use controlled vocabularies and create semi-automated computer-parsable insect morphological descriptions; (2) integrate insect morphology into broader fields of research, including ontology-informed phylogenetic methods, logical homology hypothesis testing, evo-devo studies, and genotype to phenotype mapping; and (3) automate the extraction of morphological data from the literature, enabling the generation of large-scale phenomic data, by facilitating the production and testing of informatic tools able to extract, link, annotate, and process morphological data. This descriptive model and its ontological applications will allow for clear and semantically interoperable integration of arthropod phenotypes in biodiversity studies.