Molt Cycle Research Articles

Function Analysis of Cholesterol 7-Desaturase in Ovarian Maturation and Molting in Macrobrachium nipponense: Providing Evidence for Reproductive Molting Progress.

The Cholesterol 7-desaturase gene plays an important role in insect ecdysone synthesis, but its role in ovarian development has not been reported. In this study, characteristics and the phylogenetic relationship of Cholesterol 7-desaturase were identified by bioinformatics. qPCR showed that the Mn-CH7D gene was highly expressed in the ovary, which was much higher than that in other tissues, and the expression level of Mn-CH7D reached the highest level at the third stage of the ovarian development stage (O-III). During embryonic development, the Mn-CH7D gene expression was highest in the zoea stage. The function of the Mn-CH7D gene was explored by RNA interference. The experimental group was injected with Mn-CH7D dsRNA through the pericardial cavity of M. nipponense, while the control group was injected with the same volume of dsGFP. Statistical analysis of gonadal development and GSI calculation showed that the silencing of Mn-CH7D resulted in the suppression of gonadal development. In addition, the molting frequency of the experimental group was significantly lower than that of the control group during the second molting cycle after silencing Mn-CH7D. On the seventh day after silencing, ecdysone content in the experimental group was significantly reduced. These results demonstrated that the Mn-CH7D gene played a dual role in ovarian maturation and molting of M. nipponense.

The use of physiological and transcriptional analyses to examine molting regulatory mechanisms in juvenile horseshoe crab Tachypleus tridentatus

Molting is a necessary developmental process in crustaceans, and is holistically regulated by a range of hormones and associated genes. In order to investigate physiological changes occurring at the molecular level during the molting cycle of juvenile Tachypleus tridentatus, chitinase and N-acetyl-β-D-glucosaminidase (β-NAGase) activities were firstly measured by absorbance spectrophotometry. In addition, ecdysone content was quantified by ELISA, and changes in expression levels of genes relevant to ecdysis were examined based on quantitative real-time PCR (qRT-PCR) and RNA-sequencing (RNA-seq). Results showed that chitinase, β-NAGase activity, and ecdysone content increased at the intermolt stages, peaked at premolt stages, and decreased to a lower level at molt and postmolt stages. Chitinase and β-NAGase were positively correlated with ecdysone. RNA-seq revealed that a total of 6482 differentially expressed genes (DEGs) in the four different molting stages, and 5763 DEGs had higher expression levels in the premolt stage than in the intermolt stage. A total of 59 shared DEGs were identified in all molting stages, and the highly expressed DEGs were mainly related to chitin binding, stratum corneum structural composition and neuropeptide hormone activity signaling pathways. KEGG pathway analysis showed that at the premolt stage, digestion, transport, and catabolic signaling pathways were significantly enriched and innate immune response pathways were significantly enriched as molting progressed. These results suggested that the molting of juvenile horseshoe crabs may be directly regulated by ecdysone, and chitinase and β-NAGase play a synergistic role with ecdysone during the molting cycle. The key biological processes and signaling pathways involved in hormone regulation, epidermal structural proteins, catabolism, apoptosis, and immune response potentially regulate the molting process of horseshoe crab juveniles. This study provides a theoretical basis for enhancing understanding of the molting and growth processes in marine arthropods, and a strong theoretical support for the developmenting of captive rearing technologies for Chinese horseshoe crabs.

Ammonia Stress Disturbs Moult Signaling in Juvenile Swimming Crab Portunus trituberculatus

Ammonia is a significant concern during hatchery culture in brachyuran species, and its accumulation may lead to abortive moulting and large-scale deaths of the early juveniles. To date, the underlying mechanism for ammonia-induced alteration of the moulting process is still unknown. In this study, we aimed to investigate the effects of ammonia on the moulting as well as the potential mechanisms in early juveniles of the swimming crab Portunus trituberculatus, an important aquaculture species in China. We evaluated the survival rate and moulting rate of the juvenile crabs (C2) and analyzed the expression pattern of the genes in key components of molt signaling during a complete moulting cycle under different concentrations of ammonia nitrogen (the control group: <0.1 mg/L; the LA group: 5 mg/L; and the HA group: 20 mg/L). The results showed that: (1) the survival rate in the LA and HA groups was lower than that in the control group at the end of the experiment, and moulting death syndrome (MDS) was only observed in the HA group; (2) the moulting rate was higher in the LA group and lower in the HA group compared to the control group; (3) consistent with the results of the moulting experiment, MIH showed decreased expression, and genes related to ecdysteroid synthesis, ecdysteroid receptors, and responsive effectors exhibited increased expression in the LA group compared to the control group; and (4) although MIH expression was upregulated, increased expression of the genes associated with ecdysteroid synthesis, ecdysteroid receptors and downstream effectors still observed in the HA group. Our results indicated that low levels of ammonia can promote moulting in juvenile swimming crabs by inhibiting the expression of MIH and activating moult signaling, whereas high levels of ammonia inhibit moulting and lead to MDS through impairing moult signaling.

Alopecia in Two Species of Insectivorous Bats during the Critical Time Period of Female Reproduction

Alopecia in bats has been related to multiple stressors, such as ectoparasite infestations, environmental contaminant exposure, idiopathic disease, and reproductive stress. Here we note occurrences of alopecia in 2 species of insectivorous bats, including a federally endangered species. In the summer of 2022, we encountered 3 Eptesicus fuscus (Big Brown Bat) and 7 Myotis grisescens (Gray Bat) with alopecia during mist-net and harp-trap surveys at multiple locations in Tennessee, USA. Seven of the 10 bats with bald spots were adult lactating or post-lactating females, 1 was an adult pregnant female, and 2 were adult nonreproductive males. No bats with alopecia were encountered after the lactation or post-lactation time period, despite continued mist-net and harp-trap surveys. The cause of the alopecia is unknown and warrants further investigation of prevalence across pre-reproductive (pre-pregnancy), reproductive (pregnancy, lactation, and spermatogenesis), and post-reproductive (pup volancy) periods in these populations. Understanding natural molt cycles versus alopecia as an outward sign of stress in individuals is critical for assessing the health of bat populations.

Sores of boreal moose reveal a previously unknown genetic lineage of parasitic nematode within the genus Onchocerca.

Long-standing reports of open sores on the hind legs of moose (Alces alces) have been recorded in Alaska (as well as Canada, Europe, and Michigan), eliciting concerns about causes and infection. We used histological and genomic methods to investigate the sores from 20 adult moose on the Kenai Peninsula, Alaska. We paired this with thermal imagery and molt scoring of adult moose to further describe sore formation and understand its timing. Severe, ulcerative and eosinophilic dermatitis was found in all moose with sores present, and microfilariae within intraepidermal pustules were additionally found in four samples. Genetic analysis of sores from moose revealed a previously unknown genetic lineage of Onchocerca. Adult moose molt and lose their barrier of protection against flies in June and July during peak fly activity, leaving them vulnerable and allowing the development of sores. In summary, our results indicate that the cause for the sores on the hindleg of moose is a previously unknown genetic lineage of Onchocerca, probably transmitted by black flies, in timing with the molt cycle of adult moose. These sores leave moose exposed to pathogens, making them vulnerable, and challenging their health and fitness.

English

Abstract An intensive, long-term study of the life history of O. rusticus was conducted in Fleetwood Creek, a small stream in Southern Ontario, Canada. The reproductive biology as well as molting cycle were investigated and the larval development and morphology was documented in detail for the first time in this important invasive species. Despite recent climate change effects, such as higher maximum temperatures as well as significant short term temperature fluctuations, the overall life cycle does not appear significantly different from previous studies conducted in the 1980s and 1990s but the crayfish activity appeared to be affected by temperature fluctuations associated with climate change. Mating and spawning occurred in the first week of April. The onset of mating and spawning occurred at temperatures of 9-10°C which was somewhat higher than previously reported for this species in this region of Ontario. Abdominal eggs were carried for approximately 7-weeks and larval stages remain attached to their mothers between 12 and 15 days. Free-living young were first observed in early June. Maturity is attained within the first summer, at 19-20 mm carapace length, in at least 30% of the young-of-the-year and most individuals of both sexes are mature at 25 mm carapace length. Monitoring was conducted weekly and daily during molting and spawning periods in spring 2021 and 2022, which makes this study unique with respect to most other life history field studies.

Crustacean Female Sex Hormone (CFSH) Transcript and Protein Profiles and Its Functions in Gradually Developing Adult-Specific-Features during the Prepuberty Molt Cycle of the Blue Crab, Callinectes sapidus

Crustacean female sex hormone (CFSH) plays a pivotal role in developing adult-specific female characteristics, specifically the mating and parental care system of the female blue crab, Callinectes sapidus, manifested after the puberty-terminal molt. Therefore, this study aimed to determine if there is a relationship between CFSH and the development of phenotypes specific to the female C. sapidus during its life cycle and if the continued presence of CFSH is required for developing adult-specific features during the prepuberty molt cycle. First, CasCFSH transcripts in females steadily increase, starting from crab stages 3-4 to prepuberty, except for a decrease at crab stages 15-16. The prepuberty females have the highest CasCFSH transcripts, with ∼5.6-fold higher than adults. CFSH protein levels at prepuberty are the highest but similar to adults. The first and visible secondary female characteristics include a pair of gonopores or a triangular abdomen and four pairs of pleopods seen as early as crab stages at ∼3 (carapace width, CW, 5-7 mm) - 5 (CW 8-10 mm), respectively. The adult-specific female morphological features that are developed gradually throughout the prepuberty molt cycle are manifested only after the puberty-terminal molt. A CasCFSH knockdown study by injecting CasCFSH-dsRNA into prepuberty females at specific molt stages provides further evidence: the continued presence of CasCFSH is required for gradually developing adult-specific morphological features during the prepuberty molt cycle. Overall, the abdomen size is first determined at the intermolt stage. Then, the abdominal shape, gonopores, sternal tubercles, spermathecae, and ovigerous setae and hairs are formed at the intermolt and early premolt stages. Finally, the plumose hairs are developed during intermolt, early, and late premolt stages.

Feed Efficiency, Tissue Growth and Energy Budget Changes during the Molting Cycle of Juvenile Mud Crab, Scylla serrata: Effects of Dietary Proteins, Fishmeal versus Soy Protein Concentrate

Three isoenergetic diets differing in their fishmeal/soy protein concentrate (SPC) ratio were assessed on the tissue growth and energy budget of juvenile crabs Scylla serrata in postmolt stages (PMolt) and in intermolt stages (IMolt). The average growth rates on a dry matter basis were 2.064 ± 0.324% and 0.492 ± 0.08% initial BW.day−1 during PMolt and IMolt stages, respectively. The efficiencies of the feed conversion (FCE, %), protein retention (PRE, %) and energy retention (ERE, %) were similar for the three experimental diets. However, FCE, PRE and ERE in PMolt stages were four to five times higher than in IMolt stages. The feed intake, energy and protein required for growth in PMolt stages were obviously higher than in IMolt stages. The energy budgets (% total energy intake) were marginally affected by diet but were significantly affected by the molt stage. The maintenance energy was lower in PMolt stages (49.84 ± 4.9%) than in IMolt stages (83.33 ± 2.45%). The excess in maintenance energy in IMolt stages represents the portion set aside for the next molt: shell energy content (4.97 ± 0.31%) and energy for ecdysis (±28%). Conversely, recovery energy was significantly higher in PMolt stages (34.39 ± 0.99%) than in IMolt stages (8.33 ± 1.7%). In conclusion, SPC sustained good tissue growth and good feed utilization and can be used as a main source of dietary protein for crab juveniles in captivity.

Comparative transcriptomics reveals the immune dynamics during the molting cycle of swimming crab Portunus trituberculatus.

Molting is one of the most important biological processes of crustacean species, and a number of molecular mechanisms facilitate this complex procedure. However, the understanding of the immune mechanisms underlying crustacean molting cycle remains very limited. This study performed transcriptome sequencing in hemolymph and hepatopancreas of the swimming crab (Portunus trituberculatus) during the four molting stages: post-molt (AB), inter-molt (C), pre-molt (D), and ecdysis (E). The results showed that there were 78,572 unigenes that were obtained in the hemolymph and hepatopancreas of P. trituberculatus. Further analysis showed that 98 DEGs were involved in immunity response of hemolymph and hepatopancreas, and most of the DEGs participated in the process of signal transduction, pattern recognition proteins/receptors, and antioxidative enzymes system. Specifically, the key genes and pathway involved in signal transduction including the GPCR126, beta-integrin, integrin, three genes in mitogen-activated protein kinase (MAPK) signaling cascade (MAPKKK10, MAPKK4, and p38 MAPK), and four genes in Toll pathway (Toll-like receptor, cactus, pelle-like kinase, and NFIL3). For the pattern recognition proteins/receptors, the lowest expression level of 11 genes was found in the E stage, including C-type lectin receptor, C-type lectin domain family 6 member A and SRB3/C in the hemolymph, and hepatopancreatic lectin 4, C-type lectin, SRB, Down syndrome cell adhesion molecule homolog, Down syndrome cell adhesion molecule isoform, and A2M. Moreover, the expression level of copper/zinc superoxide dismutase isoform 4, glutathione peroxidase, glutathione S-transferase, peroxiredoxin, peroxiredoxin 6, and dual oxidase 2 in stage C or stage D significantly higher than that of stage E or stage AB. These results fill in the gap of the continuous transcriptional changes that are evident during the molting cycle of crab and further provided valuable information for elucidating the molecular mechanisms of immune regulation during the molting cycle of crab.

Genome-Wide Detection of Selection Signatures for Pelt Quality Traits and Coat Color Using Whole-Genome Sequencing Data in American Mink.

Domestication and selection are the major driving forces responsible for creating genetic variability in farmed species. American mink has been under selection for more than 100 years for improved body size and pelt quality. This study aimed to identify the genomic regions subjected to selection for pelt quality traits, and coat color using the whole genome sequences of 100 mink raised in the Canadian Centre for Fur Animal Research (CCFAR) at Dalhousie Agriculture Campus (Truro, NS, Canada), and Millbank fur farm (Rockwood, ON, Canada). Measurements of three dried pelt characteristics (including pelt size (n = 35), overall quality of fur (n = 27), and nap size (n = 29)), and three coat color of Black, Stardust, and Pastel (Stardust_ Black (n = 38), and Pastel_Black (n = 41)) were used to assign animals to pairwise groups. Signatures of selection were detected using integrated measurement of fixation index (Fst), extended haplotype homozygosity (XP-EHH), and nucleotide diversity (θπ) tests. In total, overlapping top 1% of Fst and XP-EHH harbored 376 genes for pelt quality traits (110 for nap size, 163 for overall quality of fur, and 98 pelt size), and 194 genes for coat color (123 for Pastel_Black and 71 for Stardust_Black) were detected in different groups. Integrating results of Fst, and XP-EHH with the θπ test supported 19 strongly selected regions on chromosomes 3, 4, 5, 6, 7, 8, 9, and 10 that contained 33 candidate genes related to fur quality, hair follicle function, and pelt size traits. Gene ontology revealed numerous genes related to the hair cycle process and molting cycle process, epidermis development, Wnt signaling pathway and muscle development. This study provided the first map of putative selection signals related to pelt quality and coat color in American mink, which could be used as a reference for future studies attempting to identify genes associated with economically important traits in mink.

Identification and functional study of calcification-related peptide from the oriental river prawn (Macrobrachium nipponense)

Molting is an essential physiological process that occurs during crustacean development, with cuticle hardening integral to the process. However, little is known about the molecular mechanisms underlying calcification processes in crustaceans. In this study, we cloned a novel calcification-related peptide gene from the cuticle of the oriental river prawn, Macrobrachium nipponense (Mn-CRP), including mRNA and genomic DNA sequences. The full-length Mn-CRP cDNA was 551 bp and encoded 100 amino acids (AAs). The genomic DNA sequence was 1307 bp and consisted of two introns separating three exons. The deduced AA sequence had a typical chitin-binding 4 domain conserved structure. To examine Mn-CRP function, gene expression patterns in different tissues and molting cycle stages were analyzed by quantitative real-time PCR. Mn-CRP expression was significantly higher in the cuticle than in other tissues and at post-molt stages than in other molt cycle stages, where exoskeleton calcification occurred. Furthermore, silenced Mn-CRP expression by RNA interference (RNAi) effectively inhibited molting and slowed M. nipponense growth rates. These data showed Mn-CRP had an important role in M. nipponense exoskeleton calcification. This study laid the foundation for further research on the molecular mechanisms underpinning molting in crustaceans.

The interplay between prior selection, mild intermittent exposure, and acute severe exposure in phenotypic and transcriptional response to hypoxia.

Hypoxia has profound and diverse effects on aerobic organisms, disrupting oxidative phosphorylation and activating several protective pathways. Predictions have been made that exposure to mild intermittent hypoxia may be protective against more severe exposure and may extend lifespan. Here we report the lifespan effects of chronic, mild, intermittent hypoxia, and short‐term survival in acute severe hypoxia in four clones of Daphnia magna originating from either permanent or intermittent habitats. We test the hypothesis that acclimation to chronic mild intermittent hypoxia can extend lifespan through activation of antioxidant and stress‐tolerance pathways and increase survival in acute severe hypoxia through activation of oxygen transport and storage proteins and adjustment to carbohydrate metabolism. Unexpectedly, we show that chronic hypoxia extended the lifespan in the two clones originating from intermittent habitats but had the opposite effect in the two clones from permanent habitats, which also showed lower tolerance to acute hypoxia. Exposure to chronic hypoxia did not protect against acute hypoxia; to the contrary, Daphnia from the chronic hypoxia treatment had lower acute hypoxia tolerance than normoxic controls. Few transcripts changed their abundance in response to the chronic hypoxia treatment in any of the clones. After 12 h of acute hypoxia treatment, the transcriptional response was more pronounced, with numerous protein‐coding genes with functionality in oxygen transport, mitochondrial and respiratory metabolism, and gluconeogenesis, showing upregulation. While clones from intermittent habitats showed somewhat stronger differential expression in response to acute hypoxia than those from permanent habitats, contrary to predictions, there were no significant hypoxia‐by‐habitat of origin or chronic‐by‐acute treatment interactions. GO enrichment analysis revealed a possible hypoxia tolerance role by accelerating the molting cycle and regulating neuron survival through upregulation of cuticular proteins and neurotrophins, respectively.

The effects of different diet, salinity and light condition on growth performance and moulting cycle of juvenile mud crab, Scylla paramamosain

Scylla paramamosain is an importantly economical mariculture crab. To figure out the optimized conditions in the culture of juvenile crabs, three experiments were conducted to examine the effects of diet, salinity and light condition on the growth performance (body weight gain, BWG; carapace width gain, CWG; carapace length gain, CLG) and moulting cycle (MC) of crablets from V to VII stages. The growth performances of the crablets from stages V–VII have no significant differences after feeding different diets. However, the MC of crablet V fed Artemia or mixed fish were significantly shorter than that fed artificial diet. The CLG of crablet VI in salinity 25‰ was significantly higher than that in salinity 15‰, while the CWG and CLG of crablet VII in salinity 15‰ were significantly higher than that in salinity 5‰. The MC of the crablets V–VI reared in salinity 25‰ and 15‰ were significantly shorter than that in salinity 5‰, while it was significantly shorter in salinity 25‰ than that in salinity 15‰ from crablets VI–VII. For light conditions, the BWG of crablet VI with full cover was significantly higher than that with half cover. Whereas, the MC of the crablets V and VI with full cover was significantly shorter than that without cover or half cover. These findings indicated that crablet V and VI may prefer to exposing to 25‰ salinity and dark environment and feeding on Artemia for faster growth. Thus, the current findings may serve as a guide for establishing appropriate conditions in the aquaculture of juvenile mud crabs.

Astaxanthin: The ubiquitous and abundant carotenoid as a pivotal interior factor of anti‐oxidation and immune for the moulting of Portunus trituberculatus

This study was designed to demonstrate the pivotal carotenoid(s) contents and its correlation with anti-oxidative capacities in the moulting of P. trituberculatus. Experiments were carried out to investigate the cyclic fluctuations of carotenoids contents, anti-oxidative indices activities (contents) and non-specific immune indices activities (contents) in the hepatopancreas, haemolymphs and epithelia of juvenile P. trituberculatus during the moulting cycle. Further, a regressing analysis was made on the correlation between carotenoids contents and anti-oxidative indices values during the moulting cycle. The results showed that the total anti-oxidative capacity and immunity (in haemolymphs) at ecdysis decreased drastically, even though other anti-oxidative indices activities increased, when compared to those in the intermoult duration (or premoult) respectively. The decreases in T-AOC mean juveniles suffer excess oxidative damages at ecdysis. Both triglycerides and carotenoids were taken up in hepatopancreas during the inter-moult, then consumed mostly in the moulting process. The carotenoids compositions analysis results not only illustrated astaxanthin was the only carotenoid species exiting ubiquitously in hepatopancreas, haemolymphs and epithelia in all moulting stages, but also showed astaxanthin was the only one detected in haemolymphs in all moulting stages. Following correlation regression results showed astaxanthin contents were positively related to total antioxidant capacity values in haemolymphs. Accordingly, astaxanthin should be an important anti-oxidative factor in haemolymphs during the moulting. In conclusion, those results clearly suggested astaxanthin should be the ubiquitous and abundant carotenoid for anti-oxidation in P. trituberculatus during the moulting cycle. This awareness may provide a understanding of astaxanthin physiological mechanism in P. trituberculatus.

Interaction analysis of hemolymph extracellular vesicles miRNA and hemocytes mRNA reveals genes and pathways associated with molting in Scylla paramamosain

Molting is a key biological process in crustaceans, with impacts on their growth, development and reproduction. Extracellular vesicles (EVs) serve as bio-cargo carrying such as nucleic acids, proteins, and lipids which mediate intercellular communication and participate in various cell biological processes. In this study, we obtained hemocyte transcriptome data during the intermolt, premolt, and postmolt stages of the mud crab Scylla paramamosain. We analyzed the differentially expressed genes in the three stages of molt and identified a number of immune-related genes and structural cuticle genes. We then isolated and characterized the EVs from the hemolymph of S. paramamosain and sequenced their miRNA. In total, we characterized 89 EVs microRNAs (miRNAs) targeting 1447 genes that are potentially involved in the molting process of S. paramamosain. The EVs miRNAs mainly regulated the immune-related genes and affected the molting process by mediating ecdysone signaling and insulin signaling pathways during the mud crab molt cycle. This is the first study of EVs miRNAs and their interaction with mRNA to identify important candidate genes associated with, or regulating, the molting process. This study provides a better understanding of, and novel insights into, the molting cycle of crustaceans and offers baseline information for further studies in the mechanisms regulating molt.

Feedback between a retinoid-related nuclear receptor and the let-7 microRNAs controls the pace and number of molting cycles in C. elegans.

Animal development requires coordination among cyclic processes, sequential cell fate specifications, and once-a-lifetime morphogenic events, but the underlying timing mechanisms are not well understood. Caenorhabditis elegans undergoes four molts at regular 8 to 10 hour intervals. The pace of the cycle is governed by PERIOD/lin-42 and other as-yet unknown factors. Cessation of the cycle in young adults is controlled by the let-7 family of microRNAs and downstream transcription factors in the heterochronic pathway. Here, we characterize a negative feedback loop between NHR-23, the worm homolog of mammalian retinoid-related orphan receptors (RORs), and the let-7 family of microRNAs that regulates both the frequency and finite number of molts. The molting cycle is decelerated in nhr-23 knockdowns and accelerated in let-7(-) mutants, but timed similarly in let-7(-) nhr-23(-) double mutants and wild-type animals. NHR-23 binds response elements (ROREs) in the let-7 promoter and activates transcription. In turn, let-7 dampens nhr-23 expression across development via a complementary let-7-binding site (LCS) in the nhr-23 3' UTR. The molecular interactions between NHR-23 and let-7 hold true for other let-7 family microRNAs. Either derepression of nhr-23 transcripts by LCS deletion or high gene dosage of nhr-23 leads to protracted behavioral quiescence and extra molts in adults. NHR-23 and let-7 also coregulate scores of genes required for execution of the molts, including lin-42. In addition, ROREs and LCSs isolated from mammalian ROR and let-7 genes function in C. elegans, suggesting conservation of this feedback mechanism. We propose that this feedback loop unites the molting timer and the heterochronic gene regulatory network, possibly by functioning as a cycle counter.

Comparative Transcriptome Analysis on the Regulatory Mechanism of Thoracic Ganglia in Eriocheir sinensis at Post-Molt and Inter-Molt Stages.

Eriocheir sinensis is an aquatic species found distributed worldwide. It is found in the Yangtze River of China, where the commercial fishing of this valuable catadromous aquatic species has been banned. As an important member of the phylum Arthropoda, E. sinensis grows by molting over its whole lifespan. The central nervous system of Eriocheir sinensis plays an important regulatory role in molting growth. Nevertheless, there are no reports on the regulatory mechanisms of the nervous system in E. sinensis during the molting cycle. In this study, a comparative transcriptome analysis of E. sinensis thoracic ganglia at post-molt and inter-molt stages was carried out for the first time to reveal the key regulatory pathways and functional genes operating at the post-molt stage. The results indicate that pathways and regulatory genes related to carapace development, tissue regeneration, glycolysis and lipolysis and immune and anti-stress responses were significantly differentially expressed at the post-molt stage. The results of this study lay a theoretical foundation for research on the regulatory network of the E. sinensis nervous system during the post-molt developmental period. Detailed knowledge of the regulatory network involved in E. sinensis molting can be used as a basis for breeding improved E. sinensis species, recovery of the wild E. sinensis population and prosperous development of the E. sinensis artificial breeding industry.

Fisheries dataset on moulting patterns and shell quality of American lobsters H. americanus in Atlantic Canada

Monitoring the moulting phenology of American lobsters (Homarus americanus) is important for maintaining sustainable lobster stocks. Changes in lobster landings can affect reproduction and disease susceptibility. Data on lobster moult indicators and on life-history traits (sex, size) were collated from a twelve-year monitoring program (2004–2015) in six lobster fishing areas in Atlantic Canada. A total of 141,659 lobsters were sampled over 1,195 sampling events using a standardized protocol and commercial lobster fishing traps. The dataset contains pleopod stages, estimated hemolymph protein levels (°Brix values) and shell hardness as well as lobster sex and size. Evaluation of sex ratio dynamics is also possible but existing biases in sampling males and females needs to be noted. This dataset is valuable in terms of inferring spatio-temporal trends in the life history of lobsters, as well as in the analysis of their moult cycle, and hence more generally for fisheries science and marine ecology.

Whole-body transcriptome analysis provides insights into the cascade of sequential expression events involved in growth, immunity, and metabolism during the molting cycle in Scylla paramamosain

The molecular mechanisms underlying the dynamic process of crab molting are still poorly understood at the individual level. We investigated global expression changes in the mud crab, Scylla paramamosain, at the transcriptome level and revealed a cascade of sequential expression events for genes involved in various aspects of the molting process using whole-body sequencing of juvenile crabs. RNA-sequencing (RNA-seq) produced 139.49 Gb of clean reads and 20,436 differentially expressed genes (DEGs) among different molting stages. The expression patterns for genes involved in several molecular events critical for molting, such as cuticle reconstruction, cytoskeletal structure remodeling, hormone regulation, immune responses, and metabolism, were characterized and considered as mechanisms underlying molting in S. paramamosain. Among these genes, we identified 10,695 DEGs in adjacent molting stages. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that significantly enriched pathways included structural constituents of cuticle, binding and chitin metabolic processes, steroid hormone biosynthesis, insulin resistance, and amino sugar metabolic processes. The expression profiles of 12 functional genes detected via RNA-seq were corroborated via real-time RT-PCR assays. The results revealed gene expression profiles across the molting cycle and identified possible activation pathways for future investigation of the underlying molecular mechanisms.

The impact of seismic survey exposure on the righting reflex and moult cycle of Southern Rock Lobster (Jasus edwardsii) puerulus larvae and juveniles

Anthropogenic aquatic noise is recognised as an environmental pollutant with the potential to negatively affect marine organisms. Seismic surveys, used to explore subseafloor oil reserves, are a common source of aquatic noise that have garnered attention due to their intense low frequency inputs and their frequent spatial overlap with coastal fisheries. Commercially important Southern Rock Lobster (Jasus edwardsii) adults have previously shown sensitivity to signals from a single seismic air gun. Here, the sensitivity of J. edwardsii juveniles and puerulus to the signals of a full-scale seismic survey were evaluated to determine if early developmental stages were affected similarly to adults, and the range of impact. To quantify impact, lobster mortality rates, dorsoventral righting reflex and progression through moult cycle were evaluated following exposure. Exposure did not result in mortality in either developmental stage, however, air gun signals caused righting impairment to at least 500 m in lobsters sampled immediately following exposure, as had previously been reported in adults with corresponding sensory system damage following exposure. Impairment resulting from close range (0 m) exposure appeared to be persistent, as previously reported in adults, whereas juveniles exposed at a more distant range (500 m) showed recovery, indicating that exposure at a range of 500 m may not cause lasting impairment to righting. Intermoult duration was (time between moults) significantly increased in juveniles exposed at 0 m from the source, indicating the potential for slowed development, growth, and physiological stress. These results demonstrate that exposure to seismic air gun signals have the potential to negatively impact early life history stages of Southern Rock Lobsters. The similarity of both the impacts and the sound exposure levels observed here compared to previous exposure using a single air gun offer validation for the approach, which opens the potential for accessible field-based experimental work into the impact of seismic surveys on marine invertebrates.