Fine structure of the female genital system of diving beetle Stictonectes optatus (Seidlitz, 1887) (Dytiscidae-Hydroporinae) and evidence of mating plug formation

The general organization of the female genital system of the diving beetle Stictonectes optatus was studied, clarifying the complex structure of the spermatheca and spermathecal gland. The two structures adhere closely to each other, sharing a small area of their cuticular epithelium. A long duct connects the bursa copulatrix to the spermatheca, where the sperm are stored. The sperm reach the common oviduct, where egg fertilization occurs, via a fertilization duct. The spermathecal gland cells have extracellular cisterns where secretions are stored. Thin ducts composed of duct-forming cells transport these secre-tions to the apical gland region and into the spermathecal lumen. Soon after mating, the bursa copulatrix is almost completely occupied by a plug secreted by the male accessory glands. The secretions of the bursa epithelium seem to contribute to plug formation. Later this plug becomes large and spherical, obstructing the bursa copulatrix. (c) 2023 Elsevier Ltd. All rights reserved

Sperm structure of the diving beetle Deronectes moestus incospectus (Leprieur, 1876) (Hydroporinae, Dytiscidae) and considerations on extracellular material surrounding sperm bundles

The sperm cells of the diving beetle Deronectes moestus incospectus are characterized by sperm conjugation leading to the formation of sperm bundles of 64 units each. These bundles are formed at the end of spermatocyte cell divisions occurring in the testes and can be detected in the anterior region of the deferent ducts (first type of sperm conjugation). Fusions of some sperm bundles can occur at the end of the deferent ducts. The sperm bundles show sperm-head stacks (sperm rouleaux) and are surrounded by a cup of extracellular material secreted by the epithelial cells of the deferent ducts. This material extends posteriorly around the sperm bundle to cover the nuclei and the initial region of the sperm flagella. The cup extracellular material consists of fine tubules, and is no longer visible in sperm bundles at the posterior end of the deferent ducts. The sperm cells of D. moestus incospectus have an axoneme with a 9 + 9 + 2 pattern and unusual mitochondrial derivatives having a matrix showing dense dots and a small crystallized domain. Two thin elongated accessory bodies are located between the mitochondrial derivatives and the axoneme. The extracellular material can have different morphologies in the various families of Adephaga, but all are produced by the epithelium of the deferent ducts. Thus it is reasonable to assume that it has the same function in the different groups

A new cave-dwelling species of Deuteraphorura from northern Italy (Collembola, Onychiuridae)

A new cave-dwelling species, Deuteraphorura pieroluccii sp. n., is described from northern Italy. The size of adult specimens, number, and distribution of dorsal and ventral pseudocelli, and number of compound vesicles of the post antennal organ were used to distinguish it among other congeneric species

Ultrastructure of the female reproductive organs of the diving beetle Deronectes moestus incospectus (Leprieur, 1876) (Dytiscidae, Hydroporinae)

: We describe the ultrastructure of the female reproductive organs of Deronectes moestus (Dytiscidae Hydroporinae). The long spermathecal duct has a simple epithelium lined internally by a thin cuticle and externally by a thick layer of muscle cells. The wide duct lumen contains electron-dense material, among which remnants of extracellular material are visible. This material consists of tubular structures assembled around sperm bundles previously described in the male deferent ducts. The so-called gland, disposed along the spermathecal duct, is a structure with epithelial cells lined by an irregular cuticle bearing a rich system of microvilli. Many mitochondria are visible in the apical cytoplasm of the epithelial cells, and a few spheroidal bodies are close to the basal nuclei. Since the epithelial ultrastructure of the gland suggests it is involved in fluid uptake from the lumen rather than secretory activity, the term gland, coined by other authors to describe this organ, is inappropriate. The spermatheca is a large structure with a complex epithelium showing secretory and duct-forming cells. The lumen of this organ contains sperm with the distinctive ultrastructural features of those described in the male deferent ducts, namely having a mitochondrial matrix with a small crystallized area and electron-dense dots. Because to its overall organization, the spermatheca of D. moestus can be considered a more integrated organ than those in previously studied hydroporine species

A description of a new species of the genus Promesomachilis from Spain (Insecta : Microcoryphia)

A new Microcoryphian species is described from southern Spain. The new species belongs to the genus Promesomachilis and is named P. intermedia n. sp. because of the presence of intermediate characteristics in comparison with the other two species of the genus. The main features of the new species are: male maxillary palp with a field of spiralized setae on the ventral side of articles II-V, some setae also on article VI; second article of the male labial palp without a process on its distal part, though a little protuberant; labial palp also lacks a field of specialized setae, which are present in the two other species; each female gonapophysis with only 14-16 annuli, the lowest number ever found in the genus. The main feature that allow us to distinguish the three species is the presence of a sensorial field on femur II and III. In P. intermedia it is on the outer part of the femur, whereas in the other two species it is different.Se describe una nueva especie de Microcoryphia procedente del sur de España a la que denominamos Promesomachilis intermedia n. sp., por presentar caracteres intermedios entre las dos únicas que se conocían del género. La nueva especie puede caracterizarse por las siguientes particularidades: la parte ventral de los artejos II a V del palpo maxilar posee un campo de sedas espiraladas que también se encuentran, aunque en menor número, en el artejo VI; la parte dorsal del segundo artejo del palpo labial del macho no presenta ni la protuberancia (apenas perceptible en la nueva especie), ni el campo de sedas especiales que se hallan en las otras dos; las gonapófisis de la hembra constan de 14-16 divisiones, el menor número entre las tres especies. La principal característica que permite separar la nueva especie de las otras dos es la presencia, en los dos sexos, de un campo sensorial en la cara externa del fémur del segundo y tercer par de patas. En las otras especies, este campo está situado en otros pares de patas

New Findings on the Sperm Structure of Tenebrionoidea (Insecta, Coleoptera)

Simple Summary Tenebrionoidea, with more than 30,000 described species and 30 currently recognized families, is a superfamily of difficult taxonomy. The aim of this work is to support the basal position of the Mordellidae among the beetle tenebrionoids. They have a low number of sperm cells per cysts, contrary to the more derived families of the group; moreover, their sperm are not distributed in two bundles at the opposite poles of the cysts, as occurs in the higher taxa, but their sperm flagella form a loop in the median region so that sperm nuclei are positioned close to the tail end. The sperm structure of two members of higher families, Oedemeridae and Tenebrionidae, are investigated to confirm the data mentioned above. The sperm looping, which also occurs in the closely related Ripiphoridae, could be the consequence of the growth asynchrony between the cyst size and the sperm length. The Mordellidae sperm are characterized, not by small mitochondrial derivatives and accessory bodies, but by a peculiar stiff and immotile thin flagellar posterior region provided with only accessory tubules. The sperm ultrastructure of a few representative species of Tenebrionoidea was studied. Two species belong to the Mordellidae (Mordellistena brevicauda and Hoshihananomia sp.), one species to Oedemeridae (Oedemera nobilis), and one species to Tenebrionidae (Accanthopus velikensis). It is confirmed that Mordellidae are characterized by the lowest number of spermatozoa per cyst (up to 64), a number shared with Ripiphoridae. In contrast, in the two other families, up to 512 spermatozoa per cyst are observed, the same number present, for example, in Tenebrionidae. Also, as in the other more derived families of tenebrionoids studied so far, during spermatogenesis in O. nobilis and A. velikensis, sperm nuclei are regularly distributed in two sets at opposite poles of the cysts. On the contrary, the Mordellidae species do not exhibit this peculiar process. However, during spermiogenesis, the bundles of sperm bend to form a loop in their median region, quite evident in the Hoshihananomia sp., characterized by long sperm. This process, which also occurs in Ripiphoridae, probably enables individuals to produce long sperm without an increase in testicular volume. The sperm looping could be a consequence of the asynchronous growth between cyst size and sperm length. The sperm ultrastructure of the Mordellidae species reveals that they can be differentiated from other Tenebrionoidea based on the shape and size of some sperm components, such as the accessory bodies and the mitochondrial derivatives. They also show an uncommon stiff and immotile posterior flagellar region provided with only accessory tubules. These results contribute to a better knowledge of the phylogenetic relationship of the basal families of the large group of Tenebrionoidea

Sexual size differences and colour polymorphism of Rhynchophorus phoenicis in the Southwest region of Cameroon

A total of 174 specimens of the African palm weevil Rhynchophorus phoenicis (F.) were sampled during 2010, in eight different localities of the Southwest region of Cameroon. Male and female weevils were measured (body length, abdomen length, abdomen width, pronotum length, pronotum width, head size, and length from tip of rostrum to antennal insertion), and the different pronotum patterns are described. Statistical analysis shows that all morphometric parameters correlate with body length in both males and females, and seven pronotum pattern types are identified, three of which are new. African palm weevil adults show sexual dimorphism: abdomen and head size are significantly greater in females, while pronotum length is significantly greater in males. No statistical differences in the frequencies of pronotum pattern types were seen between males and females, or among localities. A significant difference was seen for the abdomen width between two localities

The mitochondrial genome of the springtail Bourletiella arvalis (Symphypleona, Collembola)

The complete mitochondrial genome of the springtail Bourletiella arvalis (Fitch, 1863) is herein described and applied to a Bayesian phylogenetic analysis, inclusive of all the Collembola mitochon- drial DNAs sequenced so far. The gene content and order, as well as the nucleotide composition, con- form with the well-known features of hexapods’ mitochondrial genomes. The phylogenetic analysis supports the monophyly of Collembola, Poduromorpha, Entomobryomorpha and Symphypleona. However, no mtDNA from Neelipleona is available to date, therefore limiting the application of mito- chondrial genomes to further investigate springtail systematics

The mitogenome of the jumping bristletail Trigoniophthalmus alternatus (Insecta, Microcoryphia) and the phylogeny of insect early-divergent lineages

The complete mitochondrial genome of the machilid Trigoniophthalmus alternatus (Silvestri 1904) is herein described and applied to phylogenetic analyses, inclusive of the most early-divergent lineages of hexapods. Both gene content and order generally conform with the organization of the arthropods’ mitochondrial genome. One gene translocation involving trnA is the autapomorphic character observed in this species. Another peculiar molecular feature is the long size of the A + T-rich region, due to the occurrence of repeat units. The phylogenetic analyses support the typical placement, along the hexapods’ tree, of Ectognatha, Monocondylia and Dicondylia, with Diplura as the adelphotaxon of all true insects

Overlooked species diversity and distribution in the Antarctic mite genus Stereotydeus

In the harsh Antarctic terrestrial ecosystems, invertebrates are currently confined to sparse and restricted ice free areas, where they have survived on multi-million-year timescales in refugia. The limited dispersal abilities of these invertebrate species, their specific habitat requirements, and the presence of geographical barriers can drastically reduce gene flow between populations, resulting in high genetic differentiation. On continental Antarctica, mites are one of the most diverse invertebrate groups. Recently, two new species of the free living prostigmatid mite genus Stereotydeus Berlese, 1901 were discovered, bringing the number of Antarctic and sub-Antarctic species of this genus up to 15, of which 7 occur along the coast of Victoria Land and in the Transantarctic Mountains. To examine the biodiversity of Stereotydeus spp., the present study combines phylogenetic, morphological and population genetic data of specimens collected from nine localities in Victoria Land. Genetically distinct intraspecific groups are spatially isolated in northern Victoria Land, while, for other species, the genetic haplogroups more often occur sympatrically in southern Victoria Land. We provide a new distribution map for the Stereotydeus species of Victoria Land, which will assist future decisions in matters of the protection and conservation of the unique Antarctic terrestrial fauna