Fine structure of the ladybird spermatozoa (Insecta, Coleoptera, Coccinellidae)

The sperm structure of Clinidium canaliculatum (Costa): A contribution to the systematic position of Rhysodidae (Coleoptera: Carabidae)

The systematic position and the phylogenetic relationship of Rhysodidae members is still debated, with some authors considering the group as a separate family of Adephaga, while for others they could be a subfamily of Carabidae. The group have morphological traits quite different from Carabidae and an aberrant behaviour compared to ground beetles being not predaceous. The sperm ultrastructure of C. canaliculatum was studied comparatively with other species of beetles, Carabidae in particular. The results indicate that the sperm structure of this species is similar to that of the Carabinae species. As in these species, C. canaliculatum has sperm conjugates with an apical conical cap protecting the heads and the initial region of flagella. This sperm appearance is also shared by another species of Rhysodidae, Omoglymmius hamatus. The material of the apical cap consists of an electron-dense material with a peculiar outer net configuration. Many species of Carabidae, however, can present a different type of sperm conjugation, the spermatostyle: a long rod-like structure where the individual sperms have only the most apical part inserted in the cortical area and the flagella are completely free. C. canaliculatum sperm are endowed with a mono-layered acrosome, a nucleus of variable shape along its length, a flagellum consisting of a typical axoneme 9 + 9+2, provided with 16 protofilaments in the tubular wall of accessory tubules, two asymmetric mitochondrial derivatives with the left one larger than the opposite one, and the right accessory body elongated and larger than the opposite one. These sperm characteristics, which are shared also by another member of the group, suggest the demotion of the family Rhysodidae to the subfamily Rhysodinae within Carabidae, a result also supported by recent molecular data.

Insights into spermatogenesis in the migratory locust, Locusta migratoria (Linnaeus, 1758) (Orthoptera: Acrididae), following histological and ultrastructural features of the testis

The migratory locust, Locusta migratoria (Linnaeus, 1758), is one of the most destructive agricultural pests globally, and this species is particularly localized in several regions of Egypt. However, so far, very little attention has been paid to the characteristics of the testes. Furthermore, spermatogenesis requires careful analysis to characterize and track developmental episodes. We thus investigated, for the first time, the histological and ultrastructural properties of the testis in L. migratoria employing a light microscope, a scanning electron microscope (SEM), and a transmission electron microscope (TEM). Our results revealed that the testis comprises several follicles, emerging with distinct outer surface wrinkle patterns for each follicle throughout the length of the follicular wall. Furthermore, histological examination of the follicles showed that each has three developmental zones. Each zone has cysts with characteristic spermatogenic elements, beginning with the spermatogonia at the distal end of each follicle and ending with the spermatozoa at the proximal end. Moreover, spermatozoa are arranged in spermatozoa bundles called spermatodesms. Overall, this research provides novel insights into the structure of the testes of L. migratoria, which will significantly contribute to formulating effective pesticides against locusts.

Morphology of male and female reproductive systems in the ground beetle Apotomus and the peculiar sperm ultrastructure of A. rufus (P. Rossi, 1790) (Coleoptera, Carabidae)

Relatively few studies have focused on evolutionary losses of sexually selected male traits. We use light and electron microscopy to study the male and female reproductive anatomy of Apotomus ground beetles (Coleoptera, Carabidae), a lineage that we reconstruct as likely having lost sperm conjugation, a putative sexually selected trait. We pay particular attention to the structure of the testes and spermatheca. Both of these organs share a strikingly similar shape-consisting of long blind canals arranged into several concentric overlapping rings measuring approximately 18 mm and 19.5 mm in total length, respectively. The similarity of these structures suggests a positive evolutionary correlation between female and male genital organs. Males are characterized by unifollicular testes with numerous germ cysts, which contain 64 sperm cells each, and we record a novel occurrence of sperm cyst "looping", a spermatogenic innovation previously only known from some fruit fly and Tenebrionid beetle sperm. The sperm are very long (about 2.7 mm) and include an extraordinarily long helicoidal acrosome, a short nucleus, and a long flagellum. These findings confirm the structural peculiarity of sperm, testis, and female reproductive tract (FRT) of Apotomus species relative to other ground beetles, which could possibly be the result of shifts in sexual selection.

Ladybug Beetle Optimization algorithm: application for real-world problems

In this paper, a novel optimization algorithm is proposed, called the Ladybug Beetle Optimization (LBO) algorithm, which is inspired by the behavior of ladybugs in nature when they search for a warm place in winter. The new proposed algorithm consists of three main parts: (1) determine the heat value in the position of each ladybug, (2) update the position of ladybugs, and (3) ignore the annihilated ladybug(s). The main innovations of LBO are related to both updating the position of the population, which is done in two separate ways, and ignoring the worst members, which leads to an increase in the search speed. Also, LBO algorithm is performed to optimize 78 well-known benchmark functions. The proposed algorithm has reached the optimal values of 73.3% of the benchmark functions and is the only algorithm that achieved the best solution of 20.5% of them. These results prove that LBO is substantially the best algorithm among other well-known optimization methods. In addition, two fundamentally different real-world optimization problems include the Economic-Environmental Dispatch Problem (EEDP) as an engineering problem and the Covid-19 pandemic modeling problem as an estimation and forecasting problem. The EEDP results illustrate that the proposed algorithm has obtained the best values in either the cost of production or the emission or even both, and the use of LBO for Covid-19 pandemic modeling problem leads to the least error compared to others.

The sperm ultrastructure of Pytho depressus (Linnaeus, 1767) (Coleoptera, Pythidae)

The sperm ultrastructure of Pytho depressus (Pythidae) is described in this study. The sperm are short cells, about 85-90 μm long, with an acrosome consisting of three layers, a cylindrical nucleus, which at its base has the initial region of two mitochondrial derivatives. The flagellum has two well-developed triangular accessory bodies, and a 9 + 9+2 axonemal pattern with accessory tubules provided with 16 protofilaments in their wall. The structure and shape of the accessory bodies are diagnostic characters within the superfamily. The sperm morphology of P. depressus can be easily distinguished from those of Ripiphoridae, Meloidae and Tenebrionidae. The P. depressus sperm are organized in cysts as in other species of the group but the sperm are not well aligned and show an antiparallel orientation, a feature also observed in other tenebrionids. The phylogenetic implications of the observed sperm features are discussed in the context of comparative sperm ultrastructure of other insect species.

The Sperm Structure and Spermatogenesis of Trypophloeus klimeschi (Coleoptera: Curculionidae: Scolytinae)

The male reproductive system, sperm structure, and spermatogenesis of Trypophloeusklimeschi (Coleoptera: Curculionidae: Scolytinae), which is one of the most destructive pests of Populus alba var. pyramidalis (Bunge), were investigated using light microscopy, scanning electron microscopy, and transmission electron microscopy. The male reproductive system of T.klimeschi is composed of testes, seminal vesicles, tubular accessory glands, multilobulated accessory glands, vasa deferentia, and a common ejaculatory duct. In spermatogenesis, two phenomena are apparent: The nuclear chromatin condenses into two different patterns, and an oval preacrosomal vesicle is present at the flank of the Golgi apparatus. The sperm are short, measuring 76.7 ± 1.8 μm in length, and are 508.1 ± 12.9 nm in width. The sperm are composed of a three-layer acrosomal complex, a cylindrical nucleus, two mitochondrial derivatives, a 9 + 9 + 2 axoneme, and two accessory bodies with a large "puff"-like expansion. Mature sperm are individually stored in seminal vesicles. During spermiogenesis, the similarities in the nuclear chromatin condensation characteristics of Curculioninae and Scolytinae are indicative of their close phylogenetic relationship. It appears that the preacrosomal vesicle being flanked by the Golgi apparatus is a characteristic of spermatogenesis in Curculionidae.

Coevolution between female seminal receptacle and sperm morphology in the semiaquatic measurer bug Hydrometra stagnorum L. (Heteroptera, Hydrometridae)

The coevolution between sperm length and size of the female sperm-storage organs is described for the first time within Heteroptera. The long sperm of the measurer bug Hydrometra stagnorum is characterized by the unusually long acrosome with its anterior region helically arranged, and by a very short nucleus. The sperm flagellum has a 9 + 9+2 conventional axoneme and crystallized mitochondrial derivatives. The female spermatheca consists of an extraordinarily long spermathecal duct ending with an apical spermathecal bulb into which flows also the secretions of a relatively short spermathecal gland. Both spermathecal duct and gland have a thin epithelium lined by a cuticle, beneath which a complex of secretory and duct forming cells are present. The secretions of these two structures flow into the apical spermathecal bulb. A thick layer of muscle fibers surrounds the epithelium. These results confirm the opinion that the dimensions of the female reproductive sperm-storage organs are able to drive the sperm morphology.

The sperm ultrastructure of the click beetles (Elateridae) and related groups (Buprestidae and Lampyridae)

In the present study, we describe the sperm morphology of 11 species of Elateriformia (9 elaterids, 1 lampyrid and 1 buprestid) using transmission electron microscopy. All species exhibited sperm that is not usually observed in insects in general. The most highlighted features are the displacement of the nucleus running parallel to the flagellar components, hitherto observed only in coccinellid and carabid beetles, and the presence of thin and dense structures along the nucleus, probably derived from the centriole adjunct, a feature that is so far exclusive to these insects. The other structures are a typical axoneme for insects with 9 + 9 + 2 microtubules, in a position diametrically opposite relative to the nucleus, two slender, symmetrical mitochondrial derivatives and a pair of discrete accessory bodies. This arrangement provides a bilaterally symmetrical flagellum, which favourably influences sperm hydrodynamics, as will be discussed. The occurrence of this unusual structural arrangement in the sperm of species from superfamilies that are phylogenetically as distant as Elateroidea and Buprestoidea support the monophyly of the infraorder Elateriformia, as proposed by some previous molecular studies.

Sperm ultrastructure of three species of ladybirds (Coleoptera, Coccinellidae)

The sperm of three coccinellid species belonging to the subfamilies Chilocorinae, Coccinellinae and Epilachninae were studied under light and transmission electron microscopy. The basic sperm structure of these ladybirds is common to that of the other previously studied species, especially the acrosome in front of the basal body and not the nucleus, with this latter running parallel with the flagellar components. In the Chilocorinae Platynaspis luteorubra (Platynaspidini) the sperm are of the type 1, as in Scymnini and Coccinellini, since they exhibited a cylindrical basal body with 9 + 0 and then 9 + 2, microtubules continuing further in an initial flagellar portion with the only axoneme devoid of accessory structures. The sperm exhibits a thin nucleus and mitochondrial derivatives. Such uniformity of sperm ultrastructure could be indicative of the occurrence of a close relationship between Platynaspidini and Scymnini as also proposed in the previous studies. Conversely, they differ markedly from the sperm of type 3 observed in the Chilocorini Exochomus quadripustulatus. In the Coccinellini Propylea quatuordecimpunctata the sperm are also of the type 1, but they can be easily differentiated from those of the other Coccinellinae studied so far, because of their very short acrosome without the posterior extension, the relatively thicker mitochondrial derivatives and the cylindrical nucleus. Epilachna clandestina sperm resemble those of E. quadripustulatus but differ from them, because they exhibit an elliptical nucleus which is anteriorly very thin, and the asymmetrical mitochondrial derivatives in the anterior extremity, with the greater one starting at the same level of the basal body, rather than at the nucleus level, as it occurs in E. quadripustulatus. Because of the differences observed in the sperm ultrastructure we propose a new sperm type (Type 4) for E. clandestina. This study on ladybird spermatozoon ultrastructure clearly indicates that the current classifications of coccinellids do not reflect the natural history of this well-known insect family.

New findings on the sperm ultrastructure of Carabidae (Insecta, Coleoptera)

The sperm structure of several species belonging to different tribes of the large Carabidae family is described. Some species of Nebriinae, such as Nebria brevicollis and Notiophilus biguttatus, have free conventional insect sperm. Their sperm type can be regarded as the ancestral model for Carabidae. All the other species examined, either with isolated sperm such as Calomera nemoralis, Scarites sp., Duvalius andreinii and Anillus florentinus or with spermatozeugmata and sperm associated to spermatostyles such as Typhloreicheia usslaubi, Brachinus italicus, Carabus convexus, Calathus fuscipes, Calathus montivagus, and Paraphorus mendax, showed sperm with long nucleus and a parallel axoneme running the length of the tail starting from the apical bell-like acrosome. C. nemoralis, like Cicindela campestris previously studied, has a sperm structure similar to that of several other Carabidae, confirming their correct assignment to the family. C. convexus has the same sperm structure as previously studied C. preslii and C. interstitialis, indicating that the spermatozeugmata of the group consist only of an apical cap in which the anterior sperm regions are embedded. Unlike other Carabidae with spermatozeugmata, Carabini have the typical sperm organization with acrosome, nucleus and flagellum in a regular sequence. A. florentinus, (Trechinae) shows major differences, such as the absence of an acrosome and an extremely long nucleus that reaches the end of the tail in close association with the axoneme. T. usslaubi (Scaritinae) has slender spermatozeugmata with orderly quartets of sperm. The posterior region of the sperm tail is also unusual, showing a perfect circular section and a plasma membrane reinforced by a dense underlying layer. The present observations confirm that spermatozeugmata, can vary in shape and size among different species of the Carabidae. Such diversity may be the result of the male reproductive strategy, different in each species, that enhances the efficiency of sperm transfer to the female.

Sperm morphology of Elasmus polistis Burks, 1971 (Hymenoptera: Chalcidoidea: Eulophidae)

The sperm morphology of the parasitoid Elasmus polistis (Eulophidae) has been investigated with light and transmission electron microscopy. The sperm were filiform and spiraled, with 165.6 (± 4.6) μm in length, and showed a distinctive head, formed by a one-layered small acrosome and a nucleus, and a flagellar region. An extracellular sheath from which many long filaments radiated out covered the acrosome and part of the nucleus. The spiral nucleus, with 24.1 (± 1.3) μm in length, was filled with homogeneously compact chromatin. In the nucleus-flagellum transition, the centriole adjunct extended posteriorly from the nuclear base in a spiral around the basal body, which has two central microtubules, and axoneme for approximately 1.1 μm. The two mitochondrial derivatives began roughly at the same level and at the base of the centriole adjunct. In cross-section, they were symmetrical, with a slightly oval shape and a smaller diameter in comparison to the axoneme. The latter, also spiraled, consisted of 9 + 9 + 2 microtubules that was formed from the basal body situated just below and aligned with the nucleus. The E. polistis sperm showed the same basic structures and morphological characteristics as observed in other Chalcidoidea. However, it was possible to distinguish the sperm of this species from those of other Eulophidae by (i) the long length of the centriole adjunct on the flagellum, and (ii) the presence of two central microtubules within the basal body. The sperm characteristics suggest that Eulophidae is closely related to Trichogrammatidae and both families are more similar to Eurytomidae, Pteromalidae, and Torymidae than Agaonidae.

Sperm ultrastructure in several species of Carabidae beetles (Insecta, Adephaga) and their organization in spermatozeugmata

Sperm structure of seven species from different Carabidae tribes was studied. Carabus preslii and Carabus granulatus interstitialis form sperm bundles (spermatozeugmata) in which the heads of conventional insect sperm cells are embedded in the apical cap (spermatostyle), leaving the posterior flagella free. On the contrary, Pterostichus morio, Pterostichus melas, Pterostichus melanarius and Amara aulica form complex spermatozeugmata bearing conspicuous axial spermatostyles associated with lateral groups of sperm. Individual sperm cells are contained in chambers delimited by laminar extensions of the cortical region of the spermatostyle. Demetrias atricapillus shares the general spermatozeugma structure with the above species, but the anterior spermatostyle region has a different structure and posteriorly, the lateral groups of sperm are separated from the spermatostyle but remain connected to it by peduncles consisting of extensions of the cortical region of the spermatostyle. The sperm of the species examined in the study consist of a short, flat acrosomal cap and, with the exception of the Carabus species, show long nuclei which extend parallel to the axonemes, along the flagella. Two relatively small mitochondrial derivatives and two small accessory bodies flank the axoneme. These bodies become very thick in the posterior flagellar region of D. atricapillus. The study revealed different spermatozeugma models and different sperm organization in the Carabidae family.

The peculiar structure of the flagellar axoneme in Coccinellidae (Insecta-Coleoptera)

The ultrastructure of the complex organisation of the spermatozoa in Harmonia axyridis and Adalia decempunctata (Coccinellidae) was studied, with particular emphasis on the origin of the anterior shifting of the axonemal structure, which becomes parallel to the nucleus in the sperm flagellum. In studying the spermiogenesis, a centriolar remodelling was observed with the long centriole, present in the early spermatids, transformed in the spermatozoa into an exceptionally long and narrowed basal body (about 0.16 × 3.5-4.0 μm long) displaying a 9 + 0 microtubular pattern in the proximal part and a 9 + 2 pattern in the following part; this is a characteristic not observed in any other pterygotan insect. The sperm also have a very long acrosome surrounded by a dense layer of material extending along the whole basal body. These two uncommon features were discussed in the light of sperm movement.