On springtails (Hexapoda: Collembola): a morphofunctional study of the jumping apparatus.

BACKGROUND: Springtails (Hexapoda: Collembola) are tiny organisms that lead a hidden life, mostly occuring deep in the soil and on leaf litter. They have a variety of interesting body morphology patterns, the most famous of which is the catapult-like structure that enables them to jump and flee from predators. This highly specialized jumping apparatus consists of a mobile furca, which when at rest fits into a trigger, "the retinaculum" on the ventral side of the abdomen. Despite the many studies that have attempted to investigate the jumping apparatus, the actual mechanisms involved in the jump, for example the way in which the furca is released by the retinaculum, how and where the mechanisms of spring and hydrostatic pressure originate, are still not properly understood. The morphology of the jumping apparatus of Orchesella cincta was investigated in detail using confocal laser scanning microscopy and MicroCT techniques for 3D reconstruction. RESULTS: The morphology of O. cincta with both flexed and extended furca is analysed and described. The abdominal musculature involved in the jumping mechanism and relevant structures of the exoskeleton of retinaculum and furca are described in detail. With the data obtained in this study, hypotheses can be made about (1) where and how the spring and hydrostatic pressure mechanisms originate; (2) which muscles act on the extension and flexion of the furca; (3) which muscles act on the retinaculum and (4) how the retinaculum is released from the furca. CONCLUSIONS: The comparative morphological study proved informative, and shows how springtail jumping involves mechanisms unique to this taxon. Hydrostatic pressure regulation possibly varies between animals with distinct segmentation, and those with fused segmentation. Interesting cuticular characters were revealed, such as basal plates and sclerites related to the construction of the spring mechanism. The present study establishes itself as a model option for future morphofunctional studies on springtail's jumping. Analysis of videos and images using a high speed camera will be useful for understanding how the jump develops through take-off, aerial and landing phases.

Light and transmission electron microscopy of the haptoral sclerites of the monogenean gill parasite Macrogyrodactylus clarii.

The present study represents the first detailed description of the haptoral sclerites of Macrogyrodactylus clarii Gussev 1961. Light microscopy reveals outgrowths of the hamuli roots; two lateral spine-like extensions of the hood-like accessory sclerites; a ridged, fan-shaped distal end of an accessory sclerite; and two thread-like accessory sclerites with biforked ends associated with the pointed hooked region of each hamulus. Transmission electron microscopy (TEM) reveals the presence of parallel tubules in the root of the hamuli and structural differences along the length of the hamulus including the root, shaft, and pointed hooked region. The root consists of two layers, the shaft four layers and pointed hooked region only one layer with dense outer serrations. Characteristic features of the hamulus root are the presence of longitudinally orientated parallel tubules in its central core and parallel electron-dense ridges in the outer layer of its middle region; features not observed in either the shaft or the pointed hooked region. Each hamulus blade of M. clarii is associated with haptoral gland cells producing electron-dense secretory bodies. The 16 marginal hooklets each consist of a blade (sickle) articulating with a handle at the guard region and a domus. TEM revealed structural differences between the handle, the blade at the articulation region, and the distal hooked region. The domus, a filamentous thread-like sclerite at the light microscope level, consists of two electron-dense, fibrous thickenings connected to each other by a cytoplasmic process. Each marginal hooklet is associated with a small cavity and a large reservoir of homogeneous particles and secretory bodies. The possible functions of these structures are discussed in relation to equivalent features in other monogeneans.

Morphological and attachment changes of Lamellodiscus theroni (Monogenea: Diplectanidae) during its post-larval development on fish.

Species of the genus Lamellodiscus Johnston et Tiegs, 1922 (Monogenea: Diplectanidae) are characterised by a complex haptor bearing many different attachment elements: two pairs of main hooks joined by medial bars, 14 peripheral marginal hooks and one or two lamellodiscs, formed by several overlapping sclerotised plates (lamellae). These haptoral structures appear gradually during parasite development and, therefore, attachment strategies vary with developmental stage. The main aim of this work was to study the developmental changes of Lamellodiscus theroni Amine, Euzet et Kechemir-Issad, 2007 under experimental conditions, with special attention to the gradual variations in attachment strategies and the pathological implications. Throughout the gradual development of the sclerotised structures, six developmental phases were distinguished in L. theroni: phase I, with only 14 peripheral marginal hooks; phase II, with main hooks (ventral and dorsal) formed; phase III, with ventral bar formed; phase IV, with dorsal bars formed; phase V, with dorsal and ventral lamellodiscs formed; and phase VI, adult stage with male copulatory organ formed. During development, parasites attach to different parts of the first and secondary gill lamellae and the mode of attachment changes from unspecific stage, i.e. based on piercing any flat gill tissue in the early stages, through an intermediate stage when ventral and dorsal main hooks are completely functional and parasites become restricted to the interlamellar space, and finally to the definitive adult attachment stage when lamellodiscs are fully developed. The timing of key events in the development of L. theroni was used to establish adequate intervals for anthelmintic drug administration.

Characterization of the proteinaceous skeletal organic matrix from the precious coral Corallium konojoi.

The Japanese red and pink corals are known to be precious because of their commercial value resulting from their use in ornaments, jewelry, and medicine. Precious corals are very interesting models for biomineralization studies and possess two different skeletal structures: an axial skeleton and an endoskeleton (sclerites). Although it has long been known that the organic matrix proteins existing in coral skeletons are critical for the oriented precipitation of CaCO3 crystals, these proteins in moderate deep-sea Japanese precious corals remain uncharacterized. Therefore, in this study, we performed skeletal whole proteome analyses using 1D and 2D electrophoresis, nano-LC, and MALDI-TOF-TOF MS. We identified a total of 147 functional coral skeletal organic matrix proteins (120 from the sclerites and 36 from the axial skeleton), including two calcium-binding calmodulin. Among the organic matrix proteins identified, nine key proteins are highly typical and common in both skeletons. Strong glycosylation activity, which is essential for skeletal formation in calcifying organisms, was detected in both skeletons. This work demonstrates unique biomineralization-related proteins in precious corals and provides the first description of the major proteinaceous components of CaCO3 minerals in precious corals, enabling the comparative investigation of biocalcification in other octocorals.

A Tale's blade: Understanding evolutionary features of oviposition behavior based on Tettigoniidae (Insecta, Orthoptera, Ensifera) ovipositor morphology.

A remarkable characteristic of katydids (Orthoptera, Tettigoniidae) is the elongated ovipositor, which is associated with oviposition behavior. The high degree of complexity of both sclerites and muscles arrangement of the ovipositor, is only similar to the ovipositor of Hymenoptera. Here we describe the morphology of the ovipositor within Tettigoniidae, and add descriptions of known oviposition behavior. Fifteen skeletal structures can be recognized, of these, three pairs of muscles are new while nine pairs were already described in the literature. The new muscles are ap2vf, anterior projection of second valvifer; bcov, blade complex of the ovipositor; and dbl, dorsal blade. The morphology of the ovipositor blade complex (bcov), the shape of the first valvifer (1vf), posterior intervalvular sclerite (piv), tergite IX (T9), anterior projection of the second valvifer (ap2vf), and the second valvifer (2vf), and their related muscles affect oviposition in Tettigoniidae. This contribution helps to understand katydid's oviposition behavior. Additionally, the new descriptions help in the search for new characters in Tettigoniidae.

A new genus of soft coral (Octocorallia, Malacalcyonacea, Cladiellidae) and three new species from Indo-Pacific coral reefs.

Molecular systematic studies of the anthozoan class Octocorallia have revealed widespread incongruence between phylogenetic relationships and taxonomic classification at all levels of the Linnean hierarchy. Among the soft coral taxa in order Malacalcyonacea, the family Alcyoniidae and its type genus Alcyonium have both been recognised to be highly polyphyletic. A recent family-level revision of Octocorallia established a number of new families for genera formerly considered to belong to Alcyoniidae, but revision of Alcyonium is not yet complete. Previous molecular studies have supported the placement of Alcyoniumverseveldti (Benayahu, 1982) in family Cladiellidae rather than Alcyoniidae, phylogenetically distinct from the other three genera in that family. Here we describe a new genus, Ofwegenumgen. nov. to accommodate O.verseveldticomb. nov. and three new species of that genus, O.coronalucissp. nov., O.kloogisp. nov., and O.collisp. nov., bringing the total number of species in this genus to four. Ofwegenumgen. nov. is a rarely encountered genus so far known from only a few locations spanning the Indian and western Pacific Oceans. We present the morphological characters of each species and use molecular data from both DNA barcoding and target-enrichment of conserved elements to explore species boundaries and phylogenetic relationships within the genus.

Exploring the trends of adaptation and evolution of sclerites with regards to habitat depth in sea pens.

Octocorals possess sclerites, small elements comprised of calcium carbonate (CaCO3) that are important diagnostic characters in octocoral taxonomy. Among octocorals, sea pens comprise a unique order (Pennatulacea) that live in a wide range of depths. Habitat depth is considered to be important in the diversification of octocoral species, but a lack of information on sea pens has limited studies on their adaptation and evolution across depth. Here, we aimed to reveal trends of adaptation and evolution of sclerite shapes in sea pens with regards to habitat depth via phylogenetic analyses and ancestral reconstruction analyses. Colony form of sea pens is suggested to have undergone convergent evolution and the loss of axis has occurred independently across the evolution of sea pens. Divergences of sea pen taxa and of sclerite forms are suggested to depend on habitat depths. In addition, their sclerite forms may be related to evolutionary history of the sclerite and the surrounding chemical environment as well as water temperature. Three-flanged sclerites may possess the tolerance towards the environment of the deep sea, while plate sclerites are suggested to be adapted towards shallower waters, and have evolved independently multiple times. The common ancestor form of sea pens was predicted to be deep-sea and similar to family Pseudumbellulidae in form, possessing sclerites intermediate in form to those of alcyonaceans and modern sea pens such as spindles, rods with spines, and three-flanged sclerites with serrated edges sclerites, as well as having an axis and bilateral traits.

The Phylogenetic Relationships of the Fanniidae within the Muscoid Grade (Diptera: Calyptrata) Based on the Musculature of the Male Terminalia.

The abdominal and pregenital segments and the genitalia were studied in males of Fannia subpellucens (Zetterstedt, 1845), Fannia canicularis (Linnaeus, 1761) and Fannia incisurata (Zetterstedt, 1838). In comparison with the remaining members of the muscoid grade, in addition to the symmetry of the pregenital segments, significant reductions of the sclerites and musculature of the male terminalia have been observed in Fanniidae. The muscular structure of pregenital segments confirms that the fused pregenital ring is syntergosternite VI + VII + VIII. Symmetry and fusion, as well as the lower number of the sclerites and muscles of the pregenital segments and male genitalia of the Fanniidae, can be considered apomorphic character states. The presence of the lateral bacilliform sclerite, as well as the presence and position of the epandrial muscles M 26, three pairs of muscles M 19 and paired muscles M 18, can be considered as a plesiomorphic character state of the Fanniidae. The structure of the sclerites and muscles of the male abdominal segments and terminalia place the Fanniidae at the base of the muscoid grade and Oestroidea, as has been confirmed by recent molecular studies.

The skeletome of the red coral Corallium rubrum indicates an independent evolution of biomineralization process in octocorals.

BACKGROUND: The process of calcium carbonate biomineralization has arisen multiple times during metazoan evolution. In the phylum Cnidaria, biomineralization has mostly been studied in the subclass Hexacorallia (i.e. stony corals) in comparison to the subclass Octocorallia (i.e. red corals); the two diverged approximately 600 million years ago. The precious Mediterranean red coral, Corallium rubrum, is an octocorallian species, which produces two distinct high-magnesium calcite biominerals, the axial skeleton and the sclerites. In order to gain insight into the red coral biomineralization process and cnidarian biomineralization evolution, we studied the protein repertoire forming the organic matrix (OM) of its two biominerals. RESULTS: We combined High-Resolution Mass Spectrometry and transcriptome analysis to study the OM composition of the axial skeleton and the sclerites. We identified a total of 102 OM proteins, 52 are found in the two red coral biominerals with scleritin being the most abundant protein in each fraction. Contrary to reef building corals, the red coral organic matrix possesses a large number of collagen-like proteins. Agrin-like glycoproteins and proteins with sugar-binding domains are also predominant. Twenty-seven and 23 proteins were uniquely assigned to the axial skeleton and the sclerites, respectively. The inferred regulatory function of these OM proteins suggests that the difference between the two biominerals is due to the modeling of the matrix network, rather than the presence of specific structural components. At least one OM component could have been horizontally transferred from prokaryotes early during Octocorallia evolution. CONCLUSION: Our results suggest that calcification of the red coral axial skeleton likely represents a secondary calcification of an ancestral gorgonian horny axis. In addition, the comparison with stony coral skeletomes highlighted the low proportion of similar proteins between the biomineral OMs of hexacorallian and octocorallian corals, suggesting an independent acquisition of calcification in anthozoans.

Redescription of larva of the South African endemic dobsonfly genus Chloroniella Esben-Petersen, 1924 (Megaloptera, Corydalidae), with a proposed terminology for Corydalidae larval sclerites.

Chloroniella Esben-Petersen is a relict, monotypic genus of Corydalidae (Megaloptera), considered sister to the remaining dobsonfly genera (Corydalinae); it is the only genus of Corydalinae known from the Afrotropical region. The larva of its only species, C. peryngueyi Esben-Petersen, 1924, was originally described by Barnard in 1931. Herein we redescribe the larva of C. peryngueyi using Scanning Electron Microscopy (SEM), colored focus-stacked images, and drawings in order to provide greater morphological detail of this significant species. Also, we propose a standardized terminology for Corydalidae larval sclerites.

Morphological ontogeny of Zachvatkinibates latilamellatus (Acari: Oribatida: Punctoribatidae), and comments on Zachvatkinibates Shaldybina.

The morphological ontogeny of Zachvatkinibates latilamellatus Bayartogtokh Aoki, 1998 is described and illustrated. The juveniles of this species are light brown, with several pairs of small, sclerotized depressions on the gastronotum, which are unique in Zachvatkinibates Shaldybina, 1973. The larva has 12 pairs of gastronotal setae, including h3, all are inserted on unsclerotized integument; nymphs have 15 pairs, of which c-series is inserted on individual sclerites, d-, l-, h-series and p1 are on sclerotized integument, and p2 and p3 on unsclerotized integument. In all juveniles, a porose humeral organ is present.

Revision of the Metallactus generosus species-group with a preliminary evaluation of the effectiveness of the endophallus morphology in distinguishing critical sibling species (Coleoptera: Chrysomelidae: Cryptocephalinae).

A taxonomic revision of the Metallactus generosus species-group is given in the present study. The complex is made up of three Neotropical species, two redescribed here and one new: Metallactus generosus Suffrian, 1866, M. argentinensis Jacoby, 1907 and M. nigroplagiatus new species. Lectotypes are designated for M. generosus and M. argentinensis. An identification key for the species group is provided. The usefulness of endophallic sclerite morphology for taxonomic and diagnostic purposes within the genus Metallactus is briefly discussed. A lapsus calami is corrected, M. chamorroi Sassi, 2019 to M. chamorroae Sassi, 2019,.

The position of the Azeliinae in the Muscidae (Diptera) based on musculature of the male terminalia.

The male genital and pregenital skeleton and musculature were studied in males of the following species of the Muscidae subfamily Azeliinae: Drymeia firthiana (Huckett, 1965), Drymeia longiseta Sorokina & Pont, 2015, Drymeia segnis (Holmgren, 1883), Thricops nigritellus (Zetterstedt, 1838), Thricops hirtulus (Zetterstedt, 1838), Hydrotaea dentipes (Fabricius, 1805), Muscina stabulans (Fallén, 1817), and Muscina levida (Harris, 1780). Descriptions and figures of the genital sclerites and muscles of D. firthiana and M. stabulans are given. A comparison was made between the genital segments and muscles of previously studied species of Mydaeinae and Muscinae and those of the Azeliinae. Based on the structure of the skeleton and muscles of syntergosternite VII + VIII and the phallapodeme muscles, significant differences were found between the subfamily Azeliinae and the subfamilies Mydaeinae and Muscinae. The basal position of the Azeliinae within the family Muscidae was confirmed. A comparison of the genital segments and muscles of the Muscidae with those of the Scathophagidae (Scathophaga stercoraria (Linnaeus, 1758)) and Anthomyiidae (Delia platura (Meigen, 1826)) was made. Tendencies in reduction of the pregenital segments and musculature, as well as of the phallapodeme muscles in the evolution of the Muscoidea have been revealed. The complete set of phallapodeme muscles in the Scathophagidae and Anthomyiidae corresponds to the basal state, and therefore the structure of the genital sclerites and muscles in the Muscidae shows a certain degree of reduction. The progressive changes in the Muscidae from the Azeliinae through the Mydaeinae to the Muscinae were traced.

Notes on the Chinese fauna of Ceratocanthinae (Coleoptera: Hybosoridae), with description of a new species of Eusphaeropeltis Gestro, 1898.

The genus Eusphaeropeltis Gestro, 1898 (Coleoptera: Scarabaeoidea: Hybosoridae: Ceratocanthinae) is recorded for the first time from China and Eusphaeropeltis chenchaomingi Jiang, Ballerio, Guo Wang, new species is described from Yunnan Province. Habitus and diagnostic features of the adult of the new species are described and illustrated. Details of Eusphaeropeltis male and female genitalia are illustrated for the first time. All known Chinese species of the subfamily Ceratocanthinae are listed and a distribution map is provided.

Ocean warming is the key filter for successful colonization of the migrant octocoral Melithaea erythraea (Ehrenberg, 1834) in the Eastern Mediterranean Sea.

Climate, which sets broad limits for migrating species, is considered a key filter to species migration between contrasting marine environments. The Southeast Mediterranean Sea (SEMS) is one of the regions where ocean temperatures are rising the fastest under recent climate change. Also, it is the most vulnerable marine region to species introductions. Here, we explore the factors which enabled the colonization of the endemic Red Sea octocoral Melithaea erythraea (Ehrenberg, 1834) along the SEMS coast, using sclerite oxygen and carbon stable isotope composition (δ 18OSC and δ 13CSC), morphology, and crystallography. The unique conditions presented by the SEMS include a greater temperature range (∼15 °C) and ultra-oligotrophy, and these are reflected by the lower δ 13CSCvalues. This is indicative of a larger metabolic carbon intake during calcification, as well as an increase in crystal size, a decrease of octocoral wart density and thickness of the migrating octocoral sclerites compared to the Red Sea samples. This suggests increased stress conditions, affecting sclerite deposition of the SEMS migrating octocoral. The δ 18Osc range of the migrating M. erythraea indicates a preference for warm water sclerite deposition, similar to the native depositional temperature range of 21-28 °C. These findings are associated with the observed increase of minimum temperatures in winter for this region, at a rate of 0.35 ± 0.27 °C decade-1 over the last 30 years, and thus the region is becoming more hospitable to the Indo-Pacific M. erythraea. This study shows a clear case study of "tropicalization" of the Mediterranean Sea due to recent warming.

Muscular Arrangement and Sclerite Morphology in the Haptor of Tetraonchus monenteron (Monogenea, Dactylogyridea).

BACKGROUND : Tetraonchidae is a small and relatively monomorphic family of dactylogyroid monogeneans. Since the morphology of sclerites of the attachment organ (haptor) is one of the primary criteria in tetraonchid taxonomy, the confocal study of sclerites and associated musculature may provide valuable taxonomic information. PURPOSE : The aim of this study was to examine the haptoral sclerites and musculature in Tetraonchus monenteron (Wagener, 1857), a common parasite of pike. METHODS: Haptoral musculature of T. monenteron was studied using phalloidin staining and confocal microscopy, with sclerites visualized in the reflection confocal mode. RESULTS: Haptoral armature of T. monenteron consists of ventral and dorsal pairs of anchors, a ventral bar, eight pairs of marginal hooks and at least three pairs of accessory sclerites. Anchors are operated by 14 muscles, of which the most prominent are extrinsic muscles, the transverse muscle interconnecting the ventral anchors, three muscles connecting the ventral anchor to the ventral bar, and four muscles of the dorsal and ventral anchors inserting on the haptoral wall. The extrinsic muscles are attached to the braceshaped sclerites, which in turn are connected to the dorsal anchors via muscle bundles. CONCLUSION: The gaffing action of the dorsal anchors is likely to be achieved by the extrinsic muscles and the transverse muscle that clamps the extrinsic muscles against the body wall. The ventral anchors are probably held in attached position by the transverse muscle and four muscles inserting on the ventral bar and haptoral wall. The haptoral musculature may have potential utility for tetraonchid taxonomy.

Morphology of the elytral base sclerites.

The elytral base sclerites (= sclerites located at the articular region between the forewing and thorax in Coleoptera) of selected taxa were examined and homologized. Although the elytral base sclerites are highly modified compared to the wing base sclerites of the other neopterans, they can be homologized by using the conservative wing flapping and folding lines as landmarks. A reduction of the first axillary sclerite was identified as a general trend of the elytral base sclerites, although the sclerite usually has a very important function to mediate flight power from the notum to the wing. This result indicates that the functional constraint against the basal sclerites is relaxed because of the lack of an ability to produce flight power by elytra. In contrast, the elytral folding system formed by the basal sclerites is well retained, which probably occurs because proper wing folding is a key for the shelter function of the elytra. The elytral base sclerites apparently contain more homoplasies than the serially homologous hindwing base sclerites of Coleoptera, which suggests that the structure is less useful for higher-level systematics. However, the faster evolutionary rate of the elytral base sclerites suggests there is potential for studying the lower-level phylogeny of Coleoptera.

Is there a relationship between the morphology of the forewing axillary sclerites and the way the wing folds in aphids (Aphidomorpha, Sternorrhyncha, Hemiptera)?

The present study describes the relationship between the morphology of the forewing axillary sclerites and the way the wings fold among 24 aphid genera as compared to a representative of coccids. Architecture of the forewing base was imaged with scanning electron and optical (fluorescence) microscopy. Significant differences in morphology of axillary sclerites between aphid species were observed, despite their belonging to one infraorder. Detailed description of 41 features of axillary sclerites was made. There was no difference between axillaries of viviparous (Aphididae) and oviparous (Adelges sp., Phylloxera sp.) species. No clear relationship between morphology of the axillary sclerites and the wing folding could be confirmed. Instead, the thorax structure determines the way the wing folds in aphids. Phylogenetic analysis based on our results cannot be conducted at this stage of study. To show how three-dimensional the structures are and how difficult to describe, a short animation of Aphis fabae (Aphididae) wing base was added. This is a preliminary study about morphology of axillary sclerites among aphids.

X-ray microtomography (microCT) of male genitalia of Nothybus kuznetsovorum (Nothybidae) and Cothornobata sp. (Micropezidae).

The results of manual dissection of the musculature of the male genitalia in Nothybus kuznetsovorum are fully confirmed by the modern methods of Micro-CT. A comparative analysis of Neria commutata and Cothornobata sp. shows that an increase in the flexion in the genitalia of males and the displacement of syntergosternite VII to the ventral side in Cothornobata sp. caused the disappearance of the muscles ITM6-7r and ITM7-8r. In addition, this increase in flexion apparently caused the fusion of the M18 muscles into one bundle. The muscle ISM5-6c goes on to moving the second segment of the forcipate appendages of sternite V.

The wing base of the palaeodictyopteran genus Dunbaria Tillyard: Where are we now?

The structure of insect wing articulation is considered as reliable source of high level characters for phylogenetic analyses. However, the correct identification of homologous structures among the main groups of Pterygota is a hotly debated issue. Therefore, the reconstruction of the wing bases in Paleozoic extinct relatives is of great interest, but at the same time it should be treated with extreme caution due to distortions caused by taphonomic effects. The present study is focused on the wing base in Dunbaria (Spilapteridae). The articulation in Dunbaria quinquefasciata is mainly formed by a prominent upright axillary plate while the humeral plate is markedly reduced. Due to unique preservation of surface relief of the axillary plate, its composition shows a detailed pattern of three fused axillary sclerites and presumable position of the sclerite 3Ax. The obtained structures were compared among Spilapteridae and to other palaeodictyopterans Ostrava nigra (Homoiopteridae) and Namuroningxia elegans (Namuroningxiidae). The comparative study uncovered two patterns of 3Ax in Dunbaria and Namuroningxia, which correspond to their different suprafamilial classification. In contrast to previous studies these new results reveal the homologous structural elements in the wing base between Paleozoic Palaeodictyoptera and their extant relatives of Ephemeroptera, Odonata and Neoptera.