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Yasuyuki Arakane - One of the best experts on this subject based on the ideXlab platform.
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cuticular protein with a low complexity sequence becomes cross linked during insect cuticle sclerotization and is required for the adult molt
Scientific Reports, 2015Co-Authors: Neal T Dittmer, Michael R Kanost, Subbaratnam Muthukrishnan, Karl J Kramer, Yasuyuki ArakaneAbstract:In the insect cuticle, structural proteins (CPs) and the polysaccharide chitin are the major components. It has been hypothesized that CPs are cross-linked to other CPs and possibly to chitin by quinones or quinone methides produced by the laccase2-mediated oxidation of N-acylcatechols. In this study we investigated functions of TcCP30, the third most abundant CP in protein extracts of elytra (wing covers) from Tribolium castaneum adults. The mature TcCP30 protein has a low complexity and highly polar amino acid sequence. TcCP30 is localized with chitin in horizontal laminae and vertically oriented columnar structures in rigid cuticles, but not in soft and membranous cuticles. Immunoblot analysis revealed that TcCP30 undergoes laccase2-mediated cross-linking during cuticle maturation in vivo, a process confirmed in vitro using recombinant rTcCP30. We identified TcCPR27 and TcCPR18, the two most abundant proteins in the elytra, as putative cross-linking partners of TcCP30. RNAi for the TcCP30 gene had no effect on larval and pupal growth and development. However, during adult eclosion, ~70% of the adults were unable to shed their Exuvium and died. These results support the hypothesis that TcCP30 plays an integral role as a cross-linked structural protein in the formation of lightweight rigid cuticle of the beetle.
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Loss of function of the yellow-e gene causes dehydration-induced mortality of adult Tribolium castaneum
Developmental Biology, 2015Co-Authors: Karl J Kramer, Michael R Kanost, Subbaratnam Muthukrishnan, Richard W. Beeman, Yasuyuki ArakaneAbstract:Abstract Yellow protein (dopachrome conversion enzyme, DCE) is involved in the melanin biosynthetic pathway that significantly accelerates pigmentation reactions in insects. Recent studies have suggested that the insect yellow genes represent a rapidly evolving gene family generating functionally diverse paralogs, but the exact physiological functions of several yellow genes are still not understood. To study the function(s) of one of the yellow genes, yellow-e (TcY-e), in the red flour beetle, Tribolium castaneum, we performed real-time PCR to analyze its developmental and tissue-specific expression, and utilized immunohistochemistry to identify the localization of the TcY-e protein in adult cuticle. Injection of double-stranded RNA for TcY-e (dsTcY-e) into late instar larvae had no effect on larval–pupal molting or pupal development. The pupal cuticle, including that lining the setae, gin traps and urogomphi, underwent normal tanning. Adult cuticle tanning including that of the head, mandibles and legs viewed through the translucent pupal cuticle was initiated on schedule (pupal days 4–5), indicating that TcY-e is not required for pupal or pharate adult cuticle pigmentation in T. castaneum. The subsequent pupal–adult molt, however, was adversely affected. Although pupal cuticle apolysis and slippage were evident, some of the adults (~25%) were unable to shed their Exuvium and died entrapped in their pupal cuticle. In addition, the resulting adults rapidly became highly desiccated. Interestingly, both the failure of the pupal–adult molt and desiccation-induced mortality were prevented by maintaining the dsTcY-e-treated insects at 100% relative humidity (rh). However, when the high humidity-rescued adults were removed from 100% rh and transferred to 50% rh, they rapidly dehydrated and died, whereas untreated beetles thrived throughout development at 50% rh. We also observed that the body color of the high humidity-rescued dsTcY-e-adults was slightly darker than that of control animals. These results support the hypothesis that TcY-e has a role not only in normal body pigmentation in T. castaneum adults but also has a vital waterproofing function.
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RNAi-based functional analysis of yellow-e in Tribolium castaneum
Entomological Research, 2011Co-Authors: Michael R Kanost, Subbaratnam Muthukrishnan, Karl J Kramer, Richard W. Beeman, Yasuyuki ArakaneAbstract:Pigmentation/melanization is an important physiological event in insect development and is involved in cuticle tanning, wound healing and encapsulation as a defensive response as well as in egg chorion hardening. “Yellow” protein (dopachrome conversion enzyme, DCE) is involved in the melanin biosynthetic pathway and significantly accelerates pigmentation and melanization reactions. Recent studies have suggested that yellow is a rapidly evolving gene family generating functionally diverse paralogs. However, the exact physiological functions of several yellow genes are still not understood. Tribolium castaneum (Tc) is an excellent experimental insect to determine the roles of individual yellow genes because it is possible to carry out RNA interference (RNAi) experiments by injecting gene-specific double-stranded RNAs (dsRNAs) into insects at all developmental stages. Injection of dsRNAs for Tcyellow-e (TcY-e) into last instar larvae had no effect on larval-pupal molting, and the resulting pupae developed normally. The pupal cuticle including the setae, gin traps and urogomphi showed normal tanning. Adult cuticle could also be viewed through the translucent pupal cuticle. Adult cuticle tanning including the head, mandibles and legs was initiated on schedule (pupal day 4-5), indicating that TcY-e is not required for pupal or adult cuticle pigmentation in T. castaneum. The subsequent pupal-adult molt, however, was adversely affected. Although pupal cuticle apolysis and slippage were evident, some of the adults (∼20%) were unable to shed their Exuvium and died entrapped in their pupal cuticle. In addition, the resulting adults rapidly became completely desiccated. Failure of the pupal-adult molt and desiccation-induced mortality were prevented by maintaining dsRNA TcY-e-treated insects at 100% relative humidity (rh). When the humidity-rescued adults were subsequently moved from 100% rh to 50% rh, they quickly desiccated and died (wild-type insects thrive throughout development at 50% rh). These results suggest that TcY-e has a “critical waterproofing” function for cuticle rather than cuticle pigmentation.
Nan-yao Su - One of the best experts on this subject based on the ideXlab platform.
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Postecdysis Sclerotization of Mouthparts of the Formosan Subterranean Termites (Isoptera: Rhinotermitidae).
Journal of Economic Entomology, 2016Co-Authors: Garima Kakkar, Thomas Chouvenc, Nan-yao SuAbstract:In termites, it is challenging to recognize the incidence of molting in workers because of their successive stationary molt, asynchronous molting among individuals, cryptic behavior, a soft and poorly sclerotized cuticle, and they immediately consume the shed exuvia of nestmates. This study describes a method in which the degree of sclerotization of the mouthparts in newly molted workers of the Formosan subterranean termite can be quantified and used to determine if an individual has recently molted, within a 36-h time frame. Changes in the tanning of mouthparts over time were used as a measure of the index of sclerotization in workers postmolting. Upon ecdysis, the primary point of articulation of the mandible already initiated sclerotization, which may allow the movement of the mandibles during the shedding of the Exuvium. The sclerotization of the secondary point of articulation and the mandibular teeth, and the width of sclerotization of the mandibles, progressively increased until reaching a plateau around 36-h postecdysis, which imply that workers can regain some level of activity as early as 2 d after ecdysis. Our observations allowed for the determination of variables for the sclerotization of the mouthparts to easily identify workers that recently molted, and this method will be useful in future studies that focus on the molting activity of workers over time and space within a termite colony, in the scope of improving current control strategies for termite pests.
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Molting Process in the Formosan Subterranean Termite (Isoptera: Rhinotermitidae)
Annals of The Entomological Society of America, 2013Co-Authors: Lin Xing, Thomas Chouvenc, Nan-yao SuAbstract:This study describes the behavioral and histological changes that take place during ecdysis in the Formosan subterranean termite. The molting process was described in four distinct phases, starting with the peristaltic contraction of the abdomen to the complete shedding of the Exuvium. Although individual termites still managed to go through the molting process when isolated from their nestmates, it required more time for the molting individual to complete the process than when aided by its nestmates. Histological observations were made on termites during the intermolt period, the premolting or fasting period, the pre-ecdysis and the ecdysis periods, and on newly molted individuals. Symbiotic protozoans were voided at the beginning of the premolting/fasting period. The detachment and reattachment of the muscles of the abdominal segments occurred during pre-ecdysis, and the leg muscle detachment and reattachment occurred during ecdysis. During pre-ecdysis, the abdominal cuticle had a wrinkled texture and two layers of cuticles were observed, one of which was the newly formed cuticle underneath the old one. Finally, the old tracheae were shed from the tracheal system and were pulled out from the spiracular openings of the mesothorax with the help of the nestmates. We concluded that, as social insects, the presence of nestmates during the molting of individual termites reduced the time necessary to complete the ecdysis, and the histological description of the molting process provides a template for further studies on the effect of chitin synthesis inhibitors on ecdysis in termites.
Stanislav N Gorb - One of the best experts on this subject based on the ideXlab platform.
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epidermis architecture and material properties of the skin of four snake species
Journal of the Royal Society Interface, 2012Co-Authors: Mariechristin G Klein, Stanislav N GorbAbstract:On the basis of structural and experimental data, it was previously demonstrated that the snake integument consists of a hard, robust, inflexible outer surface (Oberhautchen and β-layer) and softer, flexible inner layers (α-layers). It is not clear whether this phenomenon is a general adaptation of snakes to limbless locomotion or only to specific conditions, such as habitat and locomotion. The aim of the present study was to compare the structure and material properties of the outer scale layers (OSLs) and inner scale layers (ISLs) of the Exuvium epidermis in four snake species specialized to live in different habitats: Lampropeltis getula californiae (terrestrial), Epicrates cenchria cenchria (generalist), Morelia viridis (arboreal) and Gongylophis colubrinus (sand-burrowing). Scanning electron microscopy (SEM) of skin cross sections revealed a strong variation in the epidermis structure between species. The nanoindentation experiments clearly demonstrated a gradient of material properties along the epidermis in the integument of all the species studied. The presence of such a gradient is a possible adaptation to locomotion and wear minimization on natural substrates. In general, the difference in both the effective elastic modulus and hardness of the OSL and ISL between species was not large compared with the difference in epidermis thickness and architecture.
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material properties of the skin of the kenyan sand boa gongylophis colubrinus squamata boidae
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 2010Co-Authors: Mariechristin G Klein, Julia Deuschle, Stanislav N GorbAbstract:On the basis of structural data, it has been previously assumed that the integument of snakes consists of a hard, robust, inflexible outer surface (Oberhautchen and β-layer) and soft, flexible inner layers (α-layers). The aim of this study was to compare material properties of the outer and inner scale layers of the Exuvium of Gongylophis colubrinus, to relate the structure of the snake integument to its mechanical properties. The nanoindentation experiments have demonstrated that the outer scale layers are harder, and have a higher effective elastic modulus than the inner scale layers. The results obtained provide strong evidence about the presence of a gradient in the material properties of the snake integument. The possible functional significance of this gradient is discussed here as a feature minimizing damage to the integument during sliding locomotion on an abrasive surface, such as sand.
Limin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Conjugation in Hyalophysa chattoni Bradbury (Apostomatida): An adaptation to a symbiotic life cycle.
European Journal of Protistology, 2013Co-Authors: Phyllis Clarke Bradbury, Stephen M. Hash, Faye Kucera Rogers, Steven H. Neptun, Limin ZhangAbstract:Abstract Hyalophysa chattoni, borne as an encysted phoront on a crustacean's exoskeleton, metamorphoses to the trophont during the host's premolt. After the molt within 15 min to 2 h conjugants with food vacuoles appear in the Exuvium, swimming along with the trophonts. Starvation in other ciliates usually precedes conjugation, but food vacuoles in conjugants do not preclude starvation. Only after ingestion and dehydration of vacuoles ceases, does digestion of exuvial fluid begin. Conjugants resorb their feeding apparatus as they fuse. A single imperforate membrane from each partner forms the junction membrane. In a reproductive cyst conjugants divide synchronously, but now the junction membrane is interrupted by pores and channels. After the last division the daughters undergo meiosis – two meiotic divisions and one mitotic division yielding two prokarya as they simultaneously differentiate into tomites. After fertilization, pairs separate and the synkaryon divides once into a macronuclear anlage and a micronucleus. Exconjugants leave the cyst and seek a host. The parental macronucleus remains active until the phoront stage when the anlage develops. Owing to random association of micronuclei during meiosis, Hyalophysa's exconjugants are more genetically diverse than exconjugants from conventional patterns of conjugation.
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Conjugation in Hyalophysa chattoni Bradbury (Apostomatida): An adaptation to a symbiotic life cycle
European Journal of Protistology, 2013Co-Authors: Phyllis Clarke Bradbury, Stephen M. Hash, Faye Kucera Rogers, Steven H. Neptun, Limin ZhangAbstract:Hyalophysa chattoni, borne as an encysted phoront on a crustacean's exoskeleton, metamorphoses to the trophont during the host's premolt. After the molt within 15. min to 2. h conjugants with food vacuoles appear in the Exuvium, swimming along with the trophonts. Starvation in other ciliates usually precedes conjugation, but food vacuoles in conjugants do not preclude starvation. Only after ingestion and dehydration of vacuoles ceases, does digestion of exuvial fluid begin. Conjugants resorb their feeding apparatus as they fuse. A single imperforate membrane from each partner forms the junction membrane. In a reproductive cyst conjugants divide synchronously, but now the junction membrane is interrupted by pores and channels. After the last division the daughters undergo meiosis - two meiotic divisions and one mitotic division yielding two prokarya as they simultaneously differentiate into tomites. After fertilization, pairs separate and the synkaryon divides once into a macronuclear anlage and a micronucleus. Exconjugants leave the cyst and seek a host. The parental macronucleus remains active until the phoront stage when the anlage develops. Owing to random association of micronuclei during meiosis, Hyalophysa's exconjugants are more genetically diverse than exconjugants from conventional patterns of conjugation. © 2013 Elsevier GmbH.
Roberto Bertolani - One of the best experts on this subject based on the ideXlab platform.
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Tardigrada (Water Bears)
Encyclopedia of Inland Waters, 2020Co-Authors: Roberto Bertolani, Tiziana Altiero, Diane R. NelsonAbstract:The Tardigrada are hydrophilous, segmented, molting micrometazoans that occupy a diversity of niches in freshwater, marine, and terrestrial habitats. A sister group of the arthropods, this phylum of bilaterally symmetrical lobopods, most less than 1 mm in length, have a hemocoel, a complete digestive tract, a dorsal gonad with one or two gonoducts, and a dorsal lobed brain with a ventral nerve cord and five ganglia. About 1000 species have been described based on the morphology of sclerified structures, especially the claws and buccal–pharyngeal apparatus. Reproduction occurs through fertilized or unfertilized eggs, with individuals being either gonochoric, unisexual, or hermaphroditic, and eggs are deposited either freely or within the shed Exuvium. Parthenogenesis, very frequent in limnic and terrestrial tardigrades, allows them to colonize new territories by passive dispersal of a single individual. Quiescence (cryptobiosis: anhydrobiosis, anoxybiosis, cryobiosis, and osmobiosis) and diapause (encystment and resting eggs) occur during the tardigrade life history. Ecological parameters and global distribution patterns are poorly known or understood. Methods for collection, microscopy, and culturing have been developed.
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The Tardigrades of Emilia (Italy). III. Piane di Mocogno (Northern Apennines)
Zoologischer Anzeiger – A Journal of Comparative Zoology, 2004Co-Authors: Roberto Guidetti, Roberto BertolaniAbstract:Samples of leaf litter, mosses and lichens were collected in a beech forest at Piane di Mocogno (Emilia, Italy), 1200 m asl. The tardigrade community of the leaf litter was similar to that found in this substrate in Italy and in the U.S.A. At Piane di Mocogno the species association within the leaf litter was different from that in mosses and lichens (which have similar fauna), confirming that very different communities characterise different substrates such as leaf litter and mosses. During this faunal analysis, six species of tardigrades were found for the first time in this area. The presence of Microhypsibius bertolanii (first record in leaf litter and in Italy) and Eohypsibius nadjae are note worthy. Ornamented eggs in an Exuvium of Hypsibius cf.scabropygus were also recorded for the first time.
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Evolution of the Reproductive Mechanisms in Tardigrades — A Review
Zoologischer Anzeiger – A Journal of Comparative Zoology, 2004Co-Authors: Roberto BertolaniAbstract:Abstract Although tardigrades can reproduce only through gametes they have exploited several modes of reproduction, which may be determined by their environment. Marine species (mainly heterotardigrades) are gonochoristic; hermaphroditism is only cited once, and parthenogenesis is unknown. In many cases females mature one egg at a time throughout adult life, whereas males are semelparous. Gonochorism is still present in limno-terrestrial species, while sporadic hermaphroditism occurs in several eutardigrade families. Thelytoky is the most common mode of reproduction in non-marine Tardigrada. Females are iteroparous, laying groups of eggs (free or in the Exuvium), while males are semelparous (in a limnic species) or iteroparous with a continuous or cyclical maturation of the spermatozoa (in species from moss and leaf litter). Self-fertilisation appears to characterise hermaphroditic species, found in freshwater, mosses, leaf litter and soil. Egg maturation in these species is similar to that of the gonochoristic species, while spermatozoa mature in appreciable numbers before the oocytes, subsequently maturing continuously but in small numbers over the life of the animal. Parthenogenesis in limno-terrestrial tardigrades always appears continuous. In many species only females occur, but morpho-species populations may be found with both bisexual amphimictic (diploid) and unisexual thelytokous (often but not always polyploid) cytotypes. We can hypothesise that with the evolution of cryptobiosis and passive dispersal unstable and isolated habitats may favour parthenogenesis and self-fertilisation, as both reproductive modes allow colonisation of a new territory by a single individual. Parthenogenesis and hermaphroditism do not occur in the same species, and we can surmise that self-fertilisation will only evolve where parthenogenesis has never occurred.
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Phylogenetic significance of egg shell variation in tardigrades
Zoological Journal of the Linnean Society, 2002Co-Authors: Roberto Bertolani, Lorena Rebecchi, Sandra K. ClaxtonAbstract:Abstract Freshwater and semiterrestrial tardigrades produce either smooth shelled eggs laid in the Exuvium or ornamented eggs laid freely, in contrast to the more primitive marine heterotardigrades which have smooth shelled free-laid eggs. Data are presented on the observation of free-laid ornamented eggs in the primitive non marine heterotardigrade genusOreellaand in a number of eutardigrade genera includingEohypsibius, Amphibolus, MinibiotusandMacrobiotus. These findings have provided a sound basis for the formulation of a hypothesis in which the evolution of the tardigrade egg can be explained by two separate events. The first is the acquisition of ornamentation and the second is the utilization of the Exuvium for oviposition with subsequent loss of egg ornamentation. This hypothesis is consistent with new taxonomic arrangements within eutardigrade families and genera (based on character) of the animals) which have led to a more uniform assortment in terms of egg types. This means that egg type (smooth or ornamented) becomes a valid taxonomic character at the generic level.
