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Arthropod Structure & Development

Margarita I Yavorskaya, Rolf G Beutel, Sergey E Farisenkov, Alexey A Polilov
Pterothoracic structures of the minute ptiliid Nephanes titan were examined and described in detail. Effects of miniaturization and the phylogenetic and functional background are discussed. Apomorphies shared with Hydraenidae are the large metascutal shield, the fringe of setae along the posterior edge of the wings, and the fusion of the mesoventrite with the mesanepisternum. Autapomorphies of Ptiliidae are the highly modified feather-like wings, the strongly elongated alacristae, the loss of the mesotrochantin, the enlarged metathoracic pleural wing joint, and the simplification of the direct flight musculature...
January 10, 2019: Arthropod Structure & Development
Alexey A Polilov, Natalia I Reshetnikova, Pyotr N Petrov, Sergey E Farisenkov
The wings of Ptiliidae, the coleopteran family containing the smallest free-living insects, are analyzed in detail for the first time. A reconstruction of the evolutionary sequence of changes associated with miniaturization is proposed. The wings of several species are described using light microscopy and scanning electron microscopy. The morphology and scaling are analyzed in comparison with larger representatives of related groups. The wings of all studied ptiliids show some degree of ptiloptery (feather-like shape, typical for extremely small insects)...
January 7, 2019: Arthropod Structure & Development
Anastasia Alexeevna Makarova, Victor Benne Meyer-Rochow, Alexey Alexeevich Polilov
The coleopteran family Ptiliidae (featherwing beetles) includes some of the smallest insects known with most of the representatives of this family measuring less than 1 mm in body length. A small body size largely determines the morphology, physiology, and biology of an organism and affects the organization of complex sense organs. Information on the organization of the compound eyes of Ptiliidae is scarce. Using scanning electron microscopy we analyzed the eyes of representatives of all subfamilies and tribes and provide a detailed description of the eye ultrastructure of four species (Nephanes titan, Porophila mystacea, Nanosella sp...
January 6, 2019: Arthropod Structure & Development
Stefan Fischer, Zhiyuan Lu, Ian A Meinertzhagen
Existing information on insect compound eyes is mainly limited to two-dimensional information derived from histological or ultrathin sections. These allow a basic description of eye morphology, but are limited in z-axis resolution because of the section thickness or intervals between sections, so that accurate volumetric information cannot be generated. Here we use serial-sectioning transmission electron microscopy to present a 3-D reconstruction at ultrastructural level of a complete ommatidium of a miniaturized insect compound eye...
December 31, 2018: Arthropod Structure & Development
Diego Castejón, Guiomar Rotllant, Javier Alba-Tercedor, Maria Font-I-Furnols, Enric Ribes, Mercè Durfort, Guillermo Guerao
We studied the anatomy and cytology of the midgut gland (MGl) of the common spider crab Maja brachydactyla Balss 1922 at several life stages (zoea, megalopa, first juvenile, and adult) using dissection, histology, electron microscopy, computed tomography, and micro-computed tomography (micro-CT). In newly hatched larvae, 14 blind-end tubules formed the MGl. The length of the tubules increases during the larval development. In the late megalopa, the number of tubules also increases. In adults, 35,000 to 60,000 blind-end tubules comprise the MGl...
December 14, 2018: Arthropod Structure & Development
Magdalena Rost-Roszkowska, Kamil Janelt, Izabela Poprawa
Thulinius ruffoi is a small freshwater tardigrade that lives in both non-polluted and polluted freshwater environments. As a result of tardigradan body miniaturization, the digestive system is reduced and simplified. It consists of a short fore- and hindgut, and the midgut in the shape of a short tube is lined with a simple epithelium. The midgut epithelium is formed by the digestive cells and two rings of crescent-shaped cells were also detected. The anterior ring is located in the border between the fore- and midguts, while the posterior ring is situated between the mid- and hindguts...
December 14, 2018: Arthropod Structure & Development
Qing-Xiao Chen, Wen-Liang Li, Ying-Wu Chen, Jing Chen, Yue-Qing Song
Proboscides are important feeding devices for most adult Lepidoptera and exhibit significant morphological modifications and types of sensilla associated with feeding habits. In this study the architectures of the proboscides and sensilla were compared between the cotton bollworm Helicoverpa armigera (Hübner) and the armyworm Mythimna separate (Walker) using scanning electron microscopy. The proboscides of both species consist of two elongated maxillary galeae joined by dorsal and ventral legulae, forming a food canal...
December 11, 2018: Arthropod Structure & Development
A A Tellez-Garcia, R Bello-Bedoy, J N Enríquez-Vara, A Córdoba-Aguilar, A E Gutiérrez-Cabrera
Triatomines (Heteroptera: Reduviidae) include around 139 species, widely known as vectors of Chagas disease. Our aim is to review the existing knowledge of the genital morphology and sexual behavior and provide some functional analysis of these traits in triatomines. A complex set of traits comprise genitalia and these are highly variable among species. The components of the phallus and seminal products (secreted by action of testes and two accessory glands) interact to allow successful sperm transfer to the female spermathecae (usually a pair of blind tubes that emerge from the common oviduct)...
December 6, 2018: Arthropod Structure & Development
Hans Pohl, Rolf G Beutel
In this review the presently available morphological data on primary larvae of Strepsiptera are interpreted with respect to effects of miniaturization, but also their possible functional or phylogenetic background. The morphology of the 1st instars is mainly affected by functional constraints linked with parasitism but also by very distinct effects of miniaturization. The latter include modifications of the cephalic cuticle, the extremely limited free space in the body lumen, the shift of origins of cephalic muscles to the thorax, a reduced number of cephalic and thoracic muscles, extensions of muscles with cell bodies and other organelles, and an extreme concentration of the entire central nervous system in the middle region of the body...
November 27, 2018: Arthropod Structure & Development
Andrey B Shatrov, Elena V Soldatenko, Vitaliy A Stolbov, Petr A Smirnov, Olga A Petukhova
This study is the first attempt to describe the ultrastructure and functional morphology of the dermal glands in Limnochares aquatica (L., 1758). The dermal glands were studied using light-optical, SEM and TEM microscopy methods during different stages of their activity. In contrast to the vast majority of other fresh water mites, dermal glands of the studied species are originally multiplied and scattered freely at the mite body surface. The opening of the glands is saddle-like, formed of several tight cuticular folds and oriented freely to the long axis of the mite body...
November 26, 2018: Arthropod Structure & Development
Alessandro Minelli, Giuseppe Fusco
Small arthropods are not simply scaled-down versions of their larger closest relatives, as changes in morphology and functional characters are largely governed by scaling laws. These same scaling laws set strict limits to size change toward smaller sizes. The evolution of extreme miniaturized forms involves the breaking of these constraints, by means of design innovations that allow evolutionary change to evade the limits posed by scaling laws. Here we review several cases studies in insects and other arthropods that illustrate this evolutionary path...
November 26, 2018: Arthropod Structure & Development
Szczepan M Bilinski, Waclaw Tworzydlo
The embryos and first instar larvae of the epizoic earwig, Arixenia esau, develop sequentially in two different compartments of the female reproductive system, that is ovarian follicles and the lateral oviducts (the uterus). Here we show that the second (intrauterine) phase of development consists of three physiologically disparate stages: early embryos (before dorsal closure, surrounded by an egg envelope), late embryos (after dorsal closure, surrounded by an egg envelope) and the first instar larvae (after "hatching" from an egg envelope)...
November 23, 2018: Arthropod Structure & Development
Alexey A Polilov, Anastasia A Makarova, Uliana K Kolesnikova
Revealing the effect of brain size on the cognitive abilities of animals is a major challenge in the study of brain evolution. Analysis of the effects of miniaturisation on brain function in the smallest insects is especially important, as they are comparable in body size to some unicellular organisms and next to nothing is known about their cognitive abilities. We analyse for the first time the structure of the brain of the adult featherwing beetle Nephanes titan, one of the smallest insects, and results of the first ethological experiments on the capacity of learning in this species...
November 22, 2018: Arthropod Structure & Development
Javier Ortega-Hernández, Ralf Janssen, Graham E Budd
The Ecdysozoa is a major animal clade whose main uniting feature is a distinctive growth strategy that requires the periodical moulting of the external cuticle. The staggering diversity within Ecdysozoa has prompted substantial efforts to reconstruct their origin and early evolution. Based on palaentological and developmental data, we proposed a scenario for the early evolution of the ecdysozoan clade Panarthropoda (Onychophora, Tardigrada, Euarthropoda), and postulated that a terminal mouth is ancestral for this lineage...
November 17, 2018: Arthropod Structure & Development
Jason A Dunlop
Arachnids and their relatives (Chelicerata) range in body length from tens of centimetres in horseshoe crabs down to little more than 80-200 μm in several groups of mites. Spiders (Araneae) show the widest range within a given Bauplan - the largest species being ca. 270 times longer than the smallest - making them excellent models to investigate scaling effects. The two mite clades (Parasitiformes and Acariformes) are the main specialists in being small. Miniaturisation, and its consequences, is reviewed for both fossil and extant chelicerates...
November 15, 2018: Arthropod Structure & Development
Brady K Quinn
In isochronal (ICD) and equiproportional development (EPD), the proportion of total immature (egg, larval, and/or juvenile) development spent in each stage (developmental proportion) does not vary among stages or temperatures, respectively. ICD and EPD have mainly been reported in copepods, and whether they occur in other arthropods is not known. If they did, then rearing studies could be simplified because the durations of later developmental stages could be predicted based on those of earlier ones. The goal of this study was to test whether different taxa have ICD, EPD, or an alternative development type in which stage-specific proportions depend on temperature, termed 'variable proportional' development (VPD), and also how well each development type allowed later-stage durations to be predicted from earlier ones...
November 14, 2018: Arthropod Structure & Development
Vladimir Gross, Sandra Treffkorn, Julian Reichelt, Lisa Epple, Carsten Lüter, Georg Mayer
Tardigrades form a monophyletic group of microscopic ecdysozoans best known for surviving extreme environmental conditions. Due to their key phylogenetic position as a subgroup of the Panarthropoda, understanding tardigrade biology is important for comparative studies with related groups like Arthropoda. Panarthropods - and Ecdysozoa as a whole - likely evolved from macroscopic ancestors, with several taxa becoming secondarily miniaturized. Morphological and genomic evidence likewise points to a miniaturized tardigrade ancestor...
November 14, 2018: Arthropod Structure & Development
Claus Nielsen
It has recently been suggested that the panarthropod mouth was ancestrally terminal, based on the assumption that the ancestral tardigrade had a terminal mouth and on the observations of a terminal mouth in adults of some stem-group fossils. This is shown to be unlikely, and it is concluded that the ancestral panarthropod had a ventral mouth.
November 13, 2018: Arthropod Structure & Development
Romano Dallai, David Mercati, José Lino-Neto, Glenda Dias, Camilla Folly, Pietro Lupetti
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 exceptional long and narrowed basal body (about 0.16 × 3...
November 13, 2018: Arthropod Structure & Development
Brendon E Boudinot
No consensus exists for the homology and terminology of the male genitalia of the Hexapoda despite over a century of debate. Based on dissections and the literature, genital skeletomusculature was compared across the Hexapoda and contrasted with the Remipedia, the closest pancrustacean outgroup. The pattern of origin and insertion for extrinsic and intrinsic genitalic musculature was found to be consistent among the Ectognatha, Protura, and the Remipedia, allowing for the inference of homologies given recent phylogenomic studies...
November 9, 2018: Arthropod Structure & Development
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