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Oecologia Aug 2022Anthropogenic climate change and habitat alterations increase the importance of understanding the causes and consequences of variation in phenological traits. Although...
Anthropogenic climate change and habitat alterations increase the importance of understanding the causes and consequences of variation in phenological traits. Although the timing of phenological events may vary in response to both direct and mediated effects, methods to measure and distinguish direct and mediated effects have seldom been used. We used a Bayesian structural equation model (SEM) to evaluate potential direct and mediated effects of intrinsic individual and environmental factors on the timing and progression of spring molt in bighorn sheep. The SEM showed that molt phenology varied across years, was earlier in prime-aged and in heavier individuals, slower in males, and later in lactating ewes, especially if they were light. These results highlight how individual variation in intrinsic traits and life-history leads to substantial variation in a phenological trait. Indirect effects in the SEM predicted a delay in sheep molt phenology at high population density mediated through negative density effects on body mass and lactation probability. Cooler temperatures in late spring were also predicted to delay molt phenology via a negative effect on body mass. Finally, lactation reduced ewe mass which was predicted to delay molt phenology. This mediated effect thus increased the total delay (sum of direct and mediated effects) in molt phenology experience by lactating ewes. Our results underline the importance of estimating direct and indirect effects when modeling phenological traits. Because indirect effects could substantially affect estimates of total plasticity, they should be critically important to accurately predict phenological mismatches and demographic consequences of environmental change.
Topics: Adaptation, Physiological; Animals; Bayes Theorem; Climate Change; Female; Lactation; Male; Molting; Seasons; Sheep; Sheep, Bighorn
PubMed: 35964263
DOI: 10.1007/s00442-022-05231-7 -
Proceedings. Biological Sciences May 2018Birds and mammals have developed numerous strategies for replacing worn feathers and hair. Moulting usually occurs on an annual basis; however, moults that take place... (Review)
Review
Birds and mammals have developed numerous strategies for replacing worn feathers and hair. Moulting usually occurs on an annual basis; however, moults that take place twice per year (biannual moults) also occur. Here, we review the forces driving the evolution of various moult strategies, focusing on the special case of the complete biannual moult as a convergence of selection pressures across birds and mammals. Current evidence suggests that harsh environmental conditions or seasonality (e.g. larger variation in temperatures) drive evolution of a biannual moult. In turn, the biannual moult can respond to secondary selection that results in phenotypic alteration such as colour changes for mate choice dynamics (sexual selection) or camouflage requirements (natural selection). We discuss the contributions of natural and sexual selection to the evolution of biannual moulting strategies in the contexts of energetics, niche selection, functionality and physiological mechanisms. Finally, we suggest that moult strategies are directly related to species niche because environmental attributes drive the utility (e.g. thermoregulation, camouflage, social dynamics) of the hair or feathers. Functional efficiency of moult may be undermined if the pace of evolution fails to match that of the changing climate. Thus, future research should seek to understand the plasticity of moult duration and phenology, especially in the context of annual cycles.
Topics: Animals; Biological Evolution; Birds; Feathers; Hair; Mammals; Molting
PubMed: 29769361
DOI: 10.1098/rspb.2018.0318 -
PloS One 2021The crustacean molting process is regulated by an interplay of hormones produced by the eyestalk ganglia and Y-organs (YO). Molt-inhibiting hormone and crustacean...
Understanding molt control switches: Transcriptomic and expression analysis of the genes involved in ecdysteroidogenesis and cholesterol uptake pathways in the Y-organ of the blue crab, Callinectes sapidus.
The crustacean molting process is regulated by an interplay of hormones produced by the eyestalk ganglia and Y-organs (YO). Molt-inhibiting hormone and crustacean hyperglycemic hormone released by the sinus gland of the eyestalk ganglia (EG) inhibit the synthesis and secretion of ecdysteroid by the YO, hence regulating hemolymph levels during the molt cycle. The purpose of this study is to investigate the ecdysteroidogenesis pathway, specifically genes linked to changes in ecdysteroid levels occurring at early premolt (ePM). To this end, a reference transcriptome based on YO, EG, and hepatopancreas was de novo assembled. Two genes (cholesterol 7-desaturase Neverland and cytochrome p450 307a1-like Spook) involved in ecdysteroidogenesis were identified from the YO transcriptome using sequence comparisons and transcript abundance. Two other candidates, Hormone receptor 4 and probable cytochrome p450 49a1 potentially involved in ecdysteroidogenesis were also identified. Since cholesterol is the ecdysteroid precursor, a putative cholesterol carrier (Apolipoprotein D-like) was also examined to understand if cholesterol uptake coincided with the increase in the ecdysteroid levels at the ePM stage. The expression level changes of the five candidate genes in the YO were compared between intermolt (IM) and induced ePM (iePM) stages using transcriptomic analysis. Expression analysis using qPCR were carried out at IM, iePM, and normal ePM. The increase in Spook and Neverland expression in the YO at the ePM was accompanied by a concomitant rise in ecdysteroid levels. The data obtained from iePM stage were congruent with those obtained from the normal ePM stage of intact control animals. The present findings support the role of Halloween genes in the ecdysteroidogenesis and molt cycle in the blue crab, Callinectes sapidus.
Topics: Animals; Arthropod Proteins; Brachyura; Cholesterol; Ecdysteroids; Gene Expression Regulation, Developmental; Hemolymph; Invertebrate Hormones; Molting; Transcriptome
PubMed: 34478479
DOI: 10.1371/journal.pone.0256735 -
Annual Review of Entomology Jan 2015The developmental mechanisms that control body size and the relative sizes of body parts are today best understood in insects. Size is controlled by the mechanisms that... (Review)
Review
The developmental mechanisms that control body size and the relative sizes of body parts are today best understood in insects. Size is controlled by the mechanisms that cause growth to stop when a size characteristic of the species has been achieved. This requires the mechanisms to assess size and respond by stopping the process that controls growth. Growth is controlled by two hormones, insulin and ecdysone, that act synergistically by controlling cell growth and cell division. Ecdysone has two distinct functions: At low concentration it controls growth, and at high levels it causes molting and tissue differentiation. Growth is stopped by the pulse of ecdysone that initiates the metamorphic molt. Body size is sensed by either stretch receptors or oxygen restriction, depending on the species, which stimulate the high level of ecdysone secretion that induces a molt. Wing growth occurs mostly after the body has stopped growing. Wing size is adjusted to body size by variation in both the duration and level of ecdysone secretion.
Topics: Animals; Body Size; Ecdysone; Insect Proteins; Insecta; Insulin; Molting; Wings, Animal
PubMed: 25341104
DOI: 10.1146/annurev-ento-010814-020841 -
Hormone-related genes heterochronically and modularly regulate neotenic differentiation in termites.Developmental Biology May 2022Caste development in social insects requires the coordination of molting and metamorphosis during postembryonic development. In termites, i.e., hemimetabolous eusocial...
Caste development in social insects requires the coordination of molting and metamorphosis during postembryonic development. In termites, i.e., hemimetabolous eusocial insects, caste fate is determined during postembryonic development. However, it is not fully understood how the mechanisms of molting/metamorphosis are regulated in the course of differentiation between reproductive and sterile castes. In termites, only reproductives derived from alates are imagos and other sterile castes (including developmentally-terminal soldier caste) are basically juveniles or nymphs. Furthermore, supplementary reproductives that appear when the original queens and kings die or become senescent, exhibit larval features such as winglessness, and are called neotenics. Therefore, the question of whether neotenics are larvae or imagos is still under debate. In this study, by inducing female neotenic differentiation in a damp-wood termite Hodotermopsis sjostedti, morphological investigations together with juvenile hormone (JH) quantification and expression/functional analyses of genes responsible for molting and/or metamorphosis were carried out. JH titer and expression of one of the downstream genes (Kr-h1) were shown to be temporarily lowered, but increased just prior to the molt into neotenics, while consistently lowered in imaginal molt (i.e., alate differentiation). In contrast, ecdysone-related genes (EcR and E93) were upregulated at both neotenic and alate differentiation, suggesting that the heterochronic actions of ecdysone and JH lead the neotenic differentiation. Moreover, expression analyses, supported by reverse genetic experiments, showed that EcR and E93 were specifically upregulated in genital sternites (EcR and E93) and ovaries (E93) and required for the development of imaginal characters. These results suggest that the resultant mosaic phenotype of female neotenics is due to modular responses of different body parts to hormonal actions.
Topics: Animals; Ecdysone; Female; Isoptera; Juvenile Hormones; Molting; Sex Differentiation
PubMed: 35248548
DOI: 10.1016/j.ydbio.2022.02.012 -
Scientific Reports Jul 2022Termite castes express specialized phenotypes for their own tasks and are a good example of insect polyphenism. To understand the comprehensive gene expression profiles...
Termite castes express specialized phenotypes for their own tasks and are a good example of insect polyphenism. To understand the comprehensive gene expression profiles during caste differentiation, RNA-seq analysis based on the genome data was performed during the worker, presoldier, and nymphoid molts in Reticulitermes speratus. In this species, artificial induction methods for each molt have already been established, and the time scale has been clarified. Three different periods (before the gut purge (GP), during the GP, and after the molt) were discriminated in each molt, and two body parts (head and other body regions) were separately sampled. The results revealed that many differentially expressed genes (head: 2884, body: 2579) were identified in each molt. Based on the independent real-time quantitative PCR analysis, we confirmed the different expression patterns of seven out of eight genes in the presoldier molt. Based on the GO and KEGG enrichment analyses, the expressions of genes related to juvenile hormone titer changes (e.g., JH acid methyltransferase), nutrition status (e.g., Acyl-CoA Delta desaturase), and cell proliferation (e.g., insulin receptor), were shown to specifically fluctuate in each molt. These differences may have a crucial impact on caste differentiation. These data are important resources for future termite sociogenomics.
Topics: Animals; Isoptera; Juvenile Hormones; Molting; Transcriptome
PubMed: 35831400
DOI: 10.1038/s41598-022-15984-z -
Scientific Reports Aug 2022Trilobite exuviae record the development of individual trilobites and their molting process and can also contain information on their behavior. The silt- to fine-grained...
Trilobite exuviae record the development of individual trilobites and their molting process and can also contain information on their behavior. The silt- to fine-grained tuffites of the middle part of the Middle Member of the Upper Devonian Hongguleleng Formation in western Junggar contains abundant phacopidae trilobite, specifically Omegops sp. A, almost all of which are exuviae. Based on the preservation pattern, burial environment, and set of organisms co-occurring with Omegops sp. A, we speculate that the environment represented by the middle part of the Middle Member of the Hongguleleng Formation served only as the molting site of Omegops sp. A, and that their primary habitat was elsewhere. Omegops sp. A would have thus travelled to deep-water to molt. The reasons for allopatric molting may have included avoiding predators and interference from competing organisms during molting. This implies that the migratory behavior of some modern arthropods may have existed since at least the Devonian. This behavior suggests that Late Devonian phacopidae trilobites may have migrated to deeper water expanded their ecological domain as a survival strategy in response to unfavorable ecological environment.
Topics: Animals; Arthropods; Fossils; Molting; Preservation, Biological; Water
PubMed: 35974064
DOI: 10.1038/s41598-022-18146-3 -
Scientific Reports Aug 2020Molt is a critical developmental process in crustaceans. Recent studies have shown that the hepatopancreas is an important source of innate immune molecules, yet...
Molt is a critical developmental process in crustaceans. Recent studies have shown that the hepatopancreas is an important source of innate immune molecules, yet hepatopancreatic patterns of gene expression during the molt cycle which may underlie changes in immune mechanism are unknown. In this study, we performed Illumina sequencing for the hepatopancreas of the mud crab, Scylla paramamosain during molt cycle (pre-molt stage, post-molt stage, and inter-molt stage). A total of 44.55 Gb high-quality reads were obtained from the normalized cDNA of hepatopancreas. A total of 70,591 transcripts were assembled; 55,167 unigenes were identified. Transcriptomic comparison revealed 948 differentially expressed genes (DEGs) in the hepatopancreas from the three molt stages. We found that genes associated with immune response patterns changed in expression during the molt cycle. Antimicrobial peptide genes, inflammatory response genes, Toll signaling pathway factors, the phenoloxidase system, antioxidant enzymes, metal-binding proteins and other immune related genes are significantly up-regulated at the post-molt stage and inter-molt stage compared with the pre-molt stage, respectively. These genes are either not expressed or are expressed at low levels at the pre-molt stage. To our knowledge, this is the first systematic transcriptome analysis of genes capable of mobilizing a hepatopancreas immune response during the molt cycle in crustaceans, and this study will contribute to a better understanding of the hepatopancreas immune system and mud crab prophylactic immune mechanisms at the post-molt stage.
Topics: Animals; Brachyura; Gene Expression Profiling; Hepatopancreas; Molting
PubMed: 32753724
DOI: 10.1038/s41598-020-70139-2 -
The Journal of Experimental Biology Jan 2019The molting process of arthropods, chiefly controlled by ecdysteroids, is generally considered very stressful. Our previous investigations have shown that crayfish,...
The molting process of arthropods, chiefly controlled by ecdysteroids, is generally considered very stressful. Our previous investigations have shown that crayfish, after having experienced stressful situations, display anxiety-like behavior (ALB), characterized by aversion to light in a dark/light plus-maze (DLPM). In the present experiments, the spontaneous exploratory behavior of isolated crayfish was analyzed in a DLPM at different stages of their molt cycle. All tested animals displayed transitory aversion to light similar to ALB, before and, mostly, after molting, but not during inter-molt. Injection of ecdysteroids into inter-molt animals elicited ALB after a delay of 4 days, suggesting a long-term, possibly indirect, hormonal effect. Importantly, ecdysteroid-induced ALB was suppressed by the injection of an anxiolytic benzodiazepine. Thus, molts and their hormonal control impose internal stress on crayfish, leading to aversion behavior that has the main characteristics of anxiety. These observations are possibly generalizable to many other arthropods.
Topics: Animals; Anti-Anxiety Agents; Astacoidea; Benzodiazepines; Exploratory Behavior; Light; Male; Molting
PubMed: 30530836
DOI: 10.1242/jeb.186999 -
Biological Reviews of the Cambridge... May 2017Fault bars are narrow malformations in feathers oriented almost perpendicular to the rachis where the feather vein and even the rachis may break. Breaks in the barbs and... (Review)
Review
Fault bars are narrow malformations in feathers oriented almost perpendicular to the rachis where the feather vein and even the rachis may break. Breaks in the barbs and barbules result in small pieces of the feather vein being lost, while breaks in the rachis result in loss of the distal portion of the feather. Here, we provide a comprehensive review of 74 papers on fault bar formation in hopes of providing a clearer approach to their study. First, we review the evidence that the propensity to develop fault bars is modified by natural selection. Given that fault bars persist in the face of survival costs, we conclude that they must be an unfortunate consequence of some alternative adaptation that outweighs the fitness costs of fault bars. Second, we summarize evidence that the development of fault bars is triggered by psychological stress such as that of handling or predation attempts, and that they persist because the sudden contractions of the muscles in the feather follicle that control fright moults also causes the development of fault bars in growing feathers. Third, we review external and physiological (e.g. corticosterone) agents that may affect the likelihood that an acute stress will result in a growing feather exhibiting a fault bar. These modifying factors have often been treated as fundamental causes in the earlier literature on fault bars. Fourth, we then use this classification to propose a tentative model where fault bars of different severity (from light to severe) are the outcome of the interaction between the propensity to produce fault bars (which differs between species, individuals and feather follicles within individuals) and the intensity of the perturbation. This model helps to explain contradictory results in the literature, to identify gaps in our knowledge, and to suggest further studies. Lastly, we discuss ways in which better understanding of fault bars can inform us about other aspects of avian evolutionary ecology, such as the physiology of moult, the integration of moult into avian life cycles, and the strategies used to minimize stress during moult. Moreover, the study of fault bars may be relevant to understanding the aerodynamics of flight and the early evolution of flight.
Topics: Adaptation, Physiological; Animals; Biological Evolution; Birds; Ecology; Feathers; Molting; Selection, Genetic
PubMed: 27062218
DOI: 10.1111/brv.12273