Molt Cycle Research Articles

The effect of the molting cycle on the acoustic characteristics of clicks emitted by Litopenaeus vannamei

In penaeid shrimp, the mandibles are responsible for emitting click sounds when they collide during food intake, which has been used to assess feeding activity by passive acoustic monitoring. However, the acoustic parameters of the clicks could be affected by variations in the thickness of mandible cuticle during the molting cycle. Thus, the aim of this study was to evaluate the effects of the molting cycle on the acoustic characteristics of clicks emitted during the feeding activity of Litopenaeus vannamei fed commercial pelleted diet. Shrimp with an average weight of 8.75 ± 1.05 g were individually maintained in 24 tanks in a recirculating water system. A total of 12 animals had their feeding activity individually recorded soon after ecdysis (postmolt group), while another 12 were recorded in the middle of their molting cycle (intermolt group). Recordings took place in anechoic chambers with a hydrophone connected to a digital recorder (sampling rate of 192 kHz), and the click acoustic parameters were characterized in Raven® 1.5 Pro software. After the recordings, the shrimp had their mandibles removed for length measurement and histological analysis of the mandibular cuticle. Body (weight and length) and mandibular measurements did not differ between shrimp groups, but those in the postmolt stage showed significantly lower cuticle thickness. The acoustic characteristics of the clicks were affected by shrimp molting stages, with significantly lower maximum energy (dB) and maximum frequency (kHz) in postmolt shrimp, probably related to their lower mandibular cuticle thickness. These results may contribute to the assessment of shrimp feeding behavior associated with the molting cycle, as well as to the optimization of algorithms controlling acoustic automatic feeders in farming systems.

Isothiocyanate-Rich Moringa Seed Extract Activates SKN-1/Nrf2 Pathway in Caenorhabditis elegans.

Moringa oleifera is a tropical tree that has its leaves, fruits, and seeds used as medicine and food. A standardized hydroalcoholic moringa seed extract (MSE) contains up to 40% of an isothiocyanate (MIC-1; moringin), a phytochemical known to have antioxidant and anti-inflammatory properties. Animal studies suggest that MSE may help with diseases, such as edema, colitis, obesity, and diabetes. In vitro studies have shown that MIC-1 activates the Nrf2 pathway, involved in detoxification and antioxidant pathways. To broaden the understanding of the molecular pathways regulated by MSE, we hypothesized that MSE improves the health span in Caenorhabditis elegans by activating the Nrf2 homolog (SKN-1). Our whole RNA-seq data showed that MSE at 0.1 mg/mL (100 µM MIC-1) regulated the expression of a total of 1555 genes, including genes related to C. elegans cuticle, molting cycle, and glutathione metabolism. MSE upregulated several glutathione S transferases (GST), involved in the detoxification of xenobiotics, and other SKN-1 downstream targets. MSE and MIC-1 upregulate skn-1 expression and induce SKN-1 nuclear translocation, suggesting that they activate the SKN-1/Nrf2 pathway. Moreover, the regulation of glutathione metabolism is likely dependent on the SKN-1 pathway, as the gst-4 upregulation by MSE was inhibited in skn-1 knockout mutant. However, MSE decreased survivability and delayed growth rate, while purified MIC-1 increased the lifespan of C. elegans. This study shows that MIC-1 is responsible for SKN-1/Nrf2 activation by MSE; however, components other than MIC-1 within MSE likely cause detrimental effects in C. elegans.

Explosive regeneration and anamorphic development of legs in the house centipede Scutigera coleoptrata

BackgroundRegenerating legs is advantageous for arthropods as their appendages exhibit crucial functional specializations. Many arthropods possess a ‘preferred breakage point’, where the appendage is most likely to break and where regeneration likely to occur, however, different taxa exhibit different levels of regenerative potential. Centipede appendage regeneration is categorized as 'progressive' or 'explosive'. In the later, the appendage is fully regenerated after one molt. This term was used for house centipedes that frequently lose their long legs. We chose Scutigera coleoptrata as a model to comprehensively investigate the process of leg appendotomy and regeneration as well as compare it with leg development in anamorphic instars.ResultsThe trochanter exhibits a preferred breakage point. Internally, it houses a three-layered diaphragm that effectively seals the lumen. In case of leg loss, the wound is quickly sealed. The epidermis detaches from the cuticle and muscles of the coxa get compacted, giving sufficient space for the regenerating leg. A blastema forms and the leg then grows in a coiled manner. The regenerating leg is innervated and syncytial muscles form. If the leg is lost in an early intermolt phase, progression of regeneration is slower than when a specimen is closer to the next molt. Instars of house centipedes can simultaneously develop and regenerate legs. The legs develop laterally on the posterior segments under the cuticle. As opposed to regeneration, the progression of leg development always follows the same temporal pattern throughout the entire intermolt phase.ConclusionSeveral factors are of major significance in house centipede leg regeneration. First, the ease with which they lose legs: the diaphragm represents an efficient tool for appendotomy. Moreover, the functional extension of the coxa provides space for a leg to be regenerated in. Lastly, the genetic predisposition allows them to regenerate legs within one molting cycle. This “package” is unique among land arthropods, and to this degree rare in marine taxa. Furthermore, observing leg regeneration and anamorphic leg development in parallel suggest that regeneration is most likely an epiphenomenon of development, and the differences are a requirement for the novel context in which re-development occurs.

Acute and chronic toxicity of rare earth elements-enriched sediments from a prospective mining area: Effects on life history traits, behavioural and physiological responses of Gammarus fossarum (Crustacea Amphipoda)

Rare earth elements (REE) have an essential role and growing importance in the world's economy. They are attracting interest from society, policymakers, and scientists. The rapidly growing global demand for REE in several strategic industrial and agricultural sectors led many countries to consider the (re)-opening of mining activities for REE extraction. Hence, their increasing use led to the disruption of their biogeochemical cycles with anthropic abnormalities already observed in aquatic ecosystems. Nonetheless, REE remain less studied, and their mechanisms of toxicity actions are not fully understood. As amphipods, Gammarus fossarum represent an important part of the aquatic macroinvertebrate assemblage and are generally used in ecotoxicological studies for their high ecological relevance. However, their use for the study of REE effects has been rather limited so far. The current study aims to assess the potential effects of two naturally REE-enriched sediments (N2 and B4) on G. fossarum. Effects on life history traits, behavioural and physiological responses have been evaluated. Exposing G. fossarum males for 72h to sediments N2 and B4 led to a decrease in haemolymph osmolality and locomotion while an increase in ventilatory activity was observed. Exposing G. fossarum pre-copula pairs with females at the same reproductive stage to the naturally REE-enriched sediments, for one moult cycle duration (∼30 days) showed that sediment B4 led to i) a significant uptake of REE, ii) a significant decrease in the proportion of females with oocytes and iii) a significant reduction in the total number of juveniles. The physicochemical analyses of sediments showed that B4 contains the highest amount of REE with a higher proportion of light REE. The present study gives the first insights into the potential toxicity of REE on G. fossarum as they may have deleterious effects on G. fossarum population's dynamics, which may alter the functioning of aquatic ecosystems.

Changes in the physiology and chitin metabolism in cultured juvenile Panulirus ornatus across the moult cycle

Crustaceans undergo periodic moulting events to facilitate growth, this is a physiological and energetically demanding process. In an aquaculture environment, crustaceans are generally cultured in a defined space and often at high densities, where exposure to cannibalism may be greater than in the wild. Panulirus ornatus is one such emerging aquaculture candidates, moulting frequently as juveniles and providing the opportunity to investigate the relationship between physiology and genetics throughout this important developmental period. In this study, P. ornatus juveniles were assessed every three days across the seventh to eighth juvenile moult phase, sampling was divided into six distinct time points. Brix index, hepatosomatic index, and circulating ecdysone concentrations were measured across these time points. The Brix index was validated as a useful tool for assessing the moult-stages of juvenile P. ornatus, with an increase in Brix value seen in the lead up to ecdysis. Chitin metabolism was mapped, with Chitinase 3 demonstrating hepatopancreas specificity, indicating a role outside of breakdown of dietary chitin. The investigation of physiological parameters across a moult cycle provides a basis for improving moult cycle staging in cultured P. ornatus juveniles and provides further characterisation of the changes that occur during moulting in this species.

Yorkie negatively regulates the Crustin expression during molting in Chinese mitten crab, Eriocheir sinensis

Molting is a key biological process of crustaceans, which is mainly regulated by 20-hydroxyecdyone (20E). The molting cycle could be divided into three main stages including pre-molt, post-molt and inter-molt stages. The mechanism of immune regulation during molting process still requires further exploration. Yorkie (Yki) is a pivotal transcription factor in the Hippo signaling pathway, and it plays an essential role in regulating cell growth and immune response. In the present study, a Yki gene was identified from Eriocheir sinensis (designed as EsYki), and the regulatory role of EsYki in controlling the expression of antimicrobial peptide genes throughout the molting process was investigated. The mRNA expression level of EsYki was higher at the pre-molt stage compared to the post-molt stage and inter-molt stage. Following the injection of 20E, there was a notable and consistent rise in the EsYki mRNA expression in haemocytes. The increase was observed from 3 h to 48 h with the maximum level at 12 h. And the phosphorylation of Yki in the haemocytes was also significantly up-regulated at 3 h post 20E injection. Moreover, the levels of EsYki mRNA expression at three molting stages were significantly increased post Aeromonas hydrophila stimulation. The maximum level was detected at post-molt stage following A. hydrophila stimulation, while the lowest level was observed at inter-molt stage. The expression pattern of EsCrus was in contrast to EsCrus. After EsYki mRNA transcripts were inhibited by Yki inhibitor (CA3), the mRNA expression levels of EsCrus1 and EsCrus2 following A. hydrophila stimulation were significantly elevated. Furthermore, the phosphorylation level of NF-κB was also increased following the inhibition of Yki. Collectively, our findings indicated that EsYki could be induced by 20E and has a suppressive effect on the expression of EsCrus via inhibiting NF-κB during molting process. This research contributes to the understanding of the immunological regulation mechanism during molting process in crustaceans.

Impact of Dietary Variations on Kuruma Shrimp (Penaeus japonicus) Assessed through Individual-Based Rearing and Insights into Individual Differences.

This study developed an individual-rearing method to compare the effects of live feed (sandworms Perinereis aibuhitensis), formulated pellet diets, and a mixture of live feed and formula feed on the Kuruma shrimp Penaeus japonicus, aiming to minimize the influence of non-dietary factors on the growth of P. japonicus, like cannibalism. Results indicated that live feed, with its higher protein, essential amino acids, and fatty acid content, led to significantly better growth and feeding performance in P. japonicus (p < 0.05) compared to pellet diets. A mixed diet resulted in a lower average daily protein intake yet maintained a growth and feeding performance comparable to live feed. The intestinal microbiota of shrimp, dominated by Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria, showed significant shifts with diet changes. Specifically, formulated feed increased the relative abundance of Vibrio and Photobacterium while decreasing Shimia and Rhodobacterales (p < 0.05), and feeding live food resulted in a more complex and stable bacterial network. Notably, individual variances in growth and feeding were observed among shrimps, with some on formulated diets showing growth comparable to those on live feed. Each shrimp's final weight, specific growth rate, protein efficiency rate, and average daily food intake positively correlated with its initial body weight (p < 0.05), and daily intake varied cyclically with the molting cycle. These findings suggest that individual-rearing is an effective approach for detailed feed evaluation and monitoring in P. japonicus, contributing to improved feed selection, development, and feeding strategies.

The Caenorhabditis elegans cuticle and precuticle: a model for studying dynamic apical extracellular matrices in vivo.

Apical extracellular matrices (aECMs) coat the exposed surfaces of animal bodies to shape tissues, influence social interactions, and protect against pathogens and other environmental challenges. In the nematode Caenorhabditis elegans, collagenous cuticle and zona pellucida protein-rich precuticle aECMs alternately coat external epithelia across the molt cycle and play many important roles in the worm's development, behavior, and physiology. Both these types of aECMs contain many matrix proteins related to those in vertebrates, as well as some that are nematode-specific. Extensive differences observed among tissues and life stages demonstrate that aECMs are a major feature of epithelial cell identity. In addition to forming discrete layers, some cuticle components assemble into complex substructures such as ridges, furrows, and nanoscale pillars. The epidermis and cuticle are mechanically linked, allowing the epidermis to sense cuticle damage and induce protective innate immune and stress responses. The C. elegans model, with its optical transparency, facilitates the study of aECM cell biology and structure/function relationships and all the myriad ways by which aECM can influence an organism.

Reproductive Capacity, but not Food Consumption, is Reduced by Continuous Exposure to Typical Genotoxic Stressor γ-Rays in the sentinel species Gammarus fossarum.

The long-term impacts of radiocontaminants (and the associated risks) for ecosystems are still subject to vast societal and scientific debate while wildlife is chronically exposed to various sources and levels of either environmental or anthropogenic ionizing radiation from the use of nuclear energy. The present study aimed to assess induced phenotypical responses in both male and female gammarids after short-term continuous γ-irradiation, acting as a typical well-characterized genotoxic stressor that can interact directly with living matter. In particular, we started characterizing the effects using standardized measurements for biological effects on few biological functions for this species, especially feeding inhibition tests, molting, and reproductive ability, which have already been proven for chemical substances and are likely to be disturbed by ionizing radiation. The results show no significant differences in terms of the survival of organisms (males and females), of their short-term food consumption which is linked to the general health status (males and females), and of the molting cycle (females). In contrast, exposure significantly affected fecundity (number of embryos produced) at the highest dose rates for irradiated females (51 mGy h-1) and males (5 and 51 mGy h-1). These results showed that, in gammarids, reproduction, which is a critical endpoint for population dynamics, is the most radiosensitive phenotypic endpoint, with significant effects recorded on male reproductive capacity, which is more sensitive than in females. Environ Toxicol Chem 2024;43:2071-2079. © 2024 SETAC.

Integrated analysis of miRNAome and transcriptome reveals that microgravity induces the alterations of critical functional gene modules via the regulation of miRNAs in short-term space-flown C. elegans

Microgravity, as a unique hazardous factor encountered in space, can induce a series of harmful effects on living organisms. The impact of microgravity on the pivotal functional gene modules stemming from gene enrichment analysis via the regulation of miRNAs is not fully illustrated. To explore the microgravity-induced alterations in critical functional gene modules via the regulation of miRNAs, in the present study, we proposed a novel bioinformatics algorithm for the integrated analysis of miRNAome and transcriptome from short-term space-flown C. elegans. The samples of C. elegans were exposed to two space conditions, namely spaceflight (SF) and spaceflight control (SC) onboard the International Space Station for 4 days. Additionally, the samples of ground control (GC) were included for comparative analysis. Using the present algorithm, we constructed regulatory networks of functional gene modules annotated from differentially expressed genes (DEGs) and their associated regulatory differentially expressed miRNAs (DEmiRNAs). The results showed that functional gene modules of molting cycle, defense response, fatty acid metabolism, lysosome, and longevity regulating pathway were facilitated by 25 down-regulated DEmiRNAs (e.g., cel-miR-792, cel-miR-65, cel-miR-70, cel-lsy-6, cel-miR-796, etc.) in the SC vs. GC groups, whereas these modules were inhibited by 13 up-regulated DEmiRNAs (e.g., cel-miR-74, cel-miR-229, cel-miR-70, cel-miR-249, cel-miR-85, etc.) in the SF vs. GC groups. These findings indicated that microgravity could significantly alter gene expression patterns and their associated functional gene modules in short-term space-flown C. elegans. Additionally, we identified 34 miRNAs as post-transcriptional regulators that modulated these functional gene modules under microgravity conditions. Through the experimental verification, our results demonstrated that microgravity could induce the down-regulation of five critical functional gene modules (i.e., molting cycle, defense response, fatty acid metabolism, lysosome, and longevity regulating pathways) via the regulation of miRNAs in short-term space-flown C. elegans.

Impact and accumulation of calcium on soft-shell mud crab Scylla paramamosain in recirculating aquaculture system

Soft-shell crabs are highly valued for their commercial significance and culinary appeal. To enhance production of soft-shell crabs, careful attention should be paid to the water calcium concentration in their culture. This study investigated the influences of different levels of calcium concentrations on the molting and growth of mud crab (Scylla paramamosain) within a meticulously controlled recirculating aquaculture system (RAS). We established three distinct water calcium concentration gradients (200, 300, and 450 mg/L) to comprehensively assess feeding habits, molting patterns, growth, and tissue calcium levels of mud crab. Initially, we observed a gradual reduction in water calcium concentrations with increments of crab molting events in RAS. Throughout one molting cycle, the feeding incidence of the crabs remained consistently high from 4 days to 37 days post-molt, irrespective of different calcium concentrations. Nonetheless, high water calcium levels (300 and 450 mg/L) significantly shortened molt intervals and accelerated exoskeletal calcification. Specifically, the molt intervals were 52.30 ± 2.72 d, 41.65 ± 5.24 d, and 37.70 ± 3.02 d, while the carapace hardening durations were 21.51 ± 4.33 h, 17.23 ± 3.38 h, and 13.46 ± 2.76 h at water calcium concentrations of 200, 300, and 450 mg/L, respectively. Moreover, elevated calcium concentrations also significantly enhanced weight gain of the mud crab during molting. Noteworthy, regardless of fluctuations in water calcium concentration, the condition factor of the molting crabs was approximately 63%, which could be an indicator of crab selection in soft-shell crab cultivation. Furthermore, the dynamic changes in calcium concentrations were disparate among different tissues in the post-molt stage. Gill and exoskeleton tissues exhibited an upward trend in calcium concentrations, while hemolymph and hepatopancreas tissues displayed distinct patterns of decrease followed by increase. Gill and exoskeleton tissues were identified as primary sites for calcium absorption and utilization, evidenced by a positive correlation between high calcium concentrations and increased calcium content in these tissues at 6 h and 3 d post-molt. Overall, our findings provide practical evidence for optimizing aquaculture management strategies through adjustments in water calcium concentration, thus to enhance production efficiency and profitability in soft-shell mud crab aquaculture.

Earliest evidence of avian primary feathermoult.

Feather moulting is a crucial process in the avian life cycle, which evolved to maintain plumage functionality. However, moulting involves both energetic and functional costs. During moulting, plumage function temporarily decreases between the shedding of old feathers and the full growth of new ones. In flying taxa, a gradual and sequential replacement of flight feathers evolved to maintain aerodynamic capabilities during the moulting period. Little is known about the moult strategies of non-avian pennaraptoran dinosaurs and stem birds, before the emergence of crown lineage. Here, we report on two Early Cretaceous pygostylian birds from the Yixian Formation (125 mya), probably referable to Confuciusornithiformes, exhibiting morphological characteristics that suggest a gradual and sequential moult of wing flight feathers. Short primary feathers interpreted as immature are symmetrically present on both wings, as is typical among extant flying birds. Our survey of the enormous collection of the Tianyu Museum confirms previous findings that evidence of active moult in non-neornithine pennaraptorans is rare and likely indicates a moult cycle greater than one year. Documenting moult in Mesozoic feathered dinosaurs is critical for understanding their ecology, locomotor ability and the evolution of this important life-history process in birds.

Effects of background color on survival, growth, and shell coloration of juvenile Chinese mitten crab (Eriocheir sinensis)

Background color is a crucial factor influencing the growth performance and feed utilization in crustaceans. However, little is known about its impacts on the culture performance of Chinese mitten crab (Eriocheir sinensis). In this study, we examined the impacts of six different background colors (white-W, black-BK, green-G, red-R, yellow-Y, and blue-BL) on growth, inter-molt period, and coloration and total carotenoids content of carapace of juvenile E. sinensis. The culture experiment comprised two trials: a 68-day individual culture, and a 30-day group culture. Individual culture results: No significant effects of background color were found on weight gain rate (WGR), specific growth rate (SGR), molting interval, carapace length and width, and survival rate (SR) of the juvenile crabs (P > 0.05). However, during the second molting cycle, the BL group exhibited the highest WGR, and the G group showed the lowest hepatopancreas index (HSI). Meanwhile, markedly lower feed conversion ratio (FCR) was obtained for the W group compared to the G and BK groups. Group culture results: Significantly higher SR was recorded for the BK group, and the highest limb loss rate was detected for Y group indicating the significant effects of background color on survival and aggressiveness of juvenile E. sinensis. Moreover, background color impacted the carapace coloration indices where the W, BK and Y groups showed the highest brightness (L*), redness (a*), and yellowness (b*) values, respectively. Furthermore, correlation analysis revealed a positive linear relationship between the L* value and background color (y =0.1638x+27.961, R2=0.613). In conclusion, our results demonstrated that background color significantly affects culture performance and carapace color. Black background color was shown to enhance the survival rate and reduce the limb amputation rate under group culture condition. These results provide new insights on the optimization of farming technology for juvenile E. sinensis.

Molecular characterization and functional identification of the insulin-like peptides receptor gene in the oriental river prawn Macrobrachium nipponense

The insulin-like signaling pathway plays diverse biological roles in regulating metabolism, immune responses, growth, and development in invertebrates. The insulin-like peptides (ILP) receptor (ILPR) is the pivotal protein in any insulin-like signaling pathway. In our previous study, we cloned the Mn-ILP gene from the oriental river prawn Macrobrachium nipponense and elucidated its function. However, the ILPR has not yet been described in M. nipponense. In the present study, we further examined the function of Mn-ILPR in M. nipponense. The full length of the Mn-ILPR mRNA was 4790 bp, encoding 1412 amino acids. Mn-ILPR was a transmembrane receptor under a subfamily of receptor tyrosine kinases. The Mn-ILPR mRNA was predominantly expressed in muscle and hepatopancreas. To elucidate the function of Mn-ILPR, we investigated its expression in different growth stages of prawns of both sexes, in prawns of different sizes at the same time, and in prawns of the same size at different stages of the molt cycle using qRT-PCR. The expression of Mn-ILPR was markedly higher: (1) in the rapid growth stage than in other stages of male individuals; (2) in the normal growth stage than in the gonad development stage of female individuals; (3) in large male individuals than in small male individuals; and (4) in the intermolt stage than in other stages of the molt cycle. Furthermore, the long-term knockdown of Mn-ILPR by RNAi effectively delayed the growth speed of M. nipponense. Meanwhile, the short-term knockdown of Mn-ILPR revealed that the ILP-ILPR signal pathway played a part in the process of growth of M. nipponense. These findings provide a greater understanding of the molecular mechanisms underlying growth and development in crustaceans.

Caenorhabditis elegans Hedgehog-related proteins are tissue- and substructure-specific components of the cuticle and precuticle.

In Caenorhabditis elegans, expanded families of divergent Hedgehog-related and patched-related proteins promote numerous processes ranging from epithelial and sense organ development to pathogen responses to cuticle shedding during the molt cycle. The molecular functions of these proteins have been mysterious since nematodes lack a canonical Hedgehog signaling pathway. Here we show that Hedgehog-related proteins are components of the cuticle and precuticle apical extracellular matrices that coat, shape, and protect external epithelia. Of four Hedgehog-related proteins imaged, two (GRL-2 and GRL-18) stably associated with the cuticles of specific tubes and two (GRL-7 and WRT-10) labeled precuticle substructures such as furrows or alae. We found that wrt-10 mutations disrupt cuticle alae ridges, consistent with a structural role in matrix organization. We hypothesize that most nematode Hedgehog-related proteins are apical extracellular matrix components, a model that could explain many of the reported functions for this family. These results highlight ancient connections between Hedgehog proteins and the extracellular matrix and suggest that any signaling roles of C. elegans Hedgehog-related proteins will be intimately related to their matrix association.

Effect of water temperature on the development of Portunus trituberculatus larvae in the off-season breeding mode (Decapoda, Portunidae)

Abstract To clarify the influence of different water temperatures on the development of Portunus trituberculatus (swimming crab) larvae during off-season (early autumn) breeding, a gradient of four rearing temperatures of 27, 29, 31 and 33°C was set up, and the effects of water temperature on larval development were systematically compared. The results showed that the moulting cycle (MC) from the zoea 1 (Z1)-zoea 2 (Z2) stage was not significantly affected by water temperature (), remaining at approximately 3 days. However, in the Z2-megalopa (M) stage, the MC in the 31°C group was consistently the shortest. The total developmental duration and total effective cumulative temperature during Z1-M in the 31°C group were the lowest at 9.97 days and 250 days · °C, respectively. According to the equation of water temperature and larval development rate, the development rate was the fastest when the water temperature was 31°C. As the water temperature increased, the survival rate (SR) of larvae at various stages gradually decreased. The SR of the 27°C group was consistently significantly higher than that of the 33°C group (), especially in the M stage, where the SR of the 33°C group was only 2%, which was significantly lower than that of the 27°C and 29°C groups (). Among the antioxidant indexes, both superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) were the lowest in the 29°C group at 315.75 U/mg protein and 0.36 mmol/g protein, respectively, and both were significantly lower than those in the 33°C group (). Catalase (CAT) and glutathione peroxidase (GSH-PX) were both the lowest in the 31°C group, and in this group the CAT was significantly lower than in the 33°C group, and GSH-PX was significantly lower than in the 27°C group (). For malondialdehyde (MDA) content, the four groups were basically maintained at about 2.5 nmol/mg protein, and there was no significant difference (). In terms of digestive enzyme activity, the activity of lipase (LPS) was basically maintained at 1.93 U/g protein. The other four digestive enzyme activity differences were mainly reflected in that the 31 and 33°C groups maintained relatively higher levels than the 27 and 29°C groups, especially the activities of α-amylase (AMS), and cellulase (CL) in the 33°C group, which were significantly higher than those in the 27 and 29°C groups (). Comprehensive indicators indicate that a water temperature between 29 and 31°C is the appropriate temperature for the development of the larvae of off-season breeding swimming crabs.

Concomitant investigation of crustacean amphipods lipidome and metabolome during the molting cycle by Zeno SWATH data-independent acquisition coupled with electron activated dissociation and machine learning

BackgroundDIA (Data-Independent Acquisition) is a powerful technique in Liquid Chromatography coupled with high-resolution tandem Mass Spectrometry (LC-MS/MS) initially developed for proteomics studies and recently emerging in metabolomics and lipidomics. It provides a comprehensive and unbiased coverage of molecules with improved reproducibility and quantitative accuracy compared to Data-Dependent Acquisition (DDA). Combined with the Zeno trap and Electron-Activated Dissociation (EAD), DIA enhances data quality and structural elucidation compared to conventional fragmentation under CID. These tools were applied to study the lipidome and metabolome of the freshwater amphipod Gammarus fossarum, successfully discriminating stages and highlighting significant biological features. Despite being underused, DIA, along with the Zeno trap and EAD, holds great potential for advancing research in the omics field. ResultsDIA combined with the Zeno trap enhances detection reproducibility compared to conventional DDA, improving fragmentation spectra quality and putative identifications. LC coupled with Zeno-SWATH-DIA methods were used to characterize molecular changes in reproductive cycle of female gammarids. Multivariate data analysis including Principal Component Analysis and Partial Least Square Discriminant Analysis successfully identified significant features. EAD fragmentation helped to identify unknown features and to confirm their molecular structure using fragmentation spectra database annotation or machine learning. EAD database matching accurately annotated five glycerophospholipids, including the position of double bonds on fatty acid chain moieties. SIRIUS database predicted structures of unknown features based on experimental fragmentation spectra to compensate for database incompleteness. SignificanceReproducible detection of features and confident identification of putative compounds are pivotal stages within analytical pipelines. The DIA approach combined with Zeno pulsing enhances detection sensitivity and targeted fragmentation with EAD in positive polarity provides orthogonal fragmentation information. In our study, Zeno-DIA and EAD thereby facilitated a comprehensive and insightful exploration of pertinent biological molecules associated with the reproductive cycle of gammarids. The developed methodology holds great promises for identifying informative biomarkers on the health status of an environmental sentinel species.

PENGARUH PEMBERIAN KALSIUM HIDROKSIDA (Ca(OH)2) PADA BUDIDAYA UDANG VANAME (Litopenaeus vannamei) AIR TAWAR

One of Indonesian aquaculture superior commodities is vannamei shrimp. The problems faced by freshwater vannamei shrimp farmers is that the shrimp growth is not optimal at 0 ppt salinity. Regarding shrimp survival, the crucial minerals needed are calcium (Ca), potassium (K), and magnesium (Mg). Calcium is able to increase shrimp skin calcium levels and the length of molting cycle, as well as for the growth of shrimp biomass and an increase in dissolved calcium can lead to an increase in pH. This research utilized calcium hydroxide Ca(OH)2, and was conducted for 45 days. The results showed that the highest SR value at P2 was 73.33%. The highest specific weight growth value was found in P3 as much as 6.21%/ day, and the highest specific length rate was found in P3 as much as 2.66%/ day. The highest coefficient of variance in weight was found in P2 with 46.3%, and the highest coefficient of variation in length was found in P2 with 12.88%. The best FCR value was found in P3 with 0.48. Therefore, adding Ca (OH)2 could increase the growth of vannamei shrimp in freshwater.

High densities of large tuaki, the New Zealand cockle Austrovenus stutchburyi, provide a post-settlement predation refuge for conspecific juveniles

Bivalves are ecosystem engineers, and their effective management relies on a full understanding of the mechanisms that influence population dynamics. Juvenile tuaki (New Zealand cockle) Austrovenus stutchburyi, a numerically dominant and ecologically important bivalve in New Zealand estuaries, were found at higher densities when surrounded by high densities of large adults within Waitati Inlet, in southern New Zealand. Consequently, we hypothesised that adults provided a refuge from predation for juveniles, resulting in higher juvenile survival and retention in dense beds. The observed pattern was consistent with post-settlement Allee effects, where declines in density and truncated size distributions may have resulted in unsuccessful recruitment if a density threshold was reached. Field experiments were undertaken in 2020 and 2021 to test the potential sheltering effect of adults on retention and survival of juveniles, with and without the addition of organic loading of sediments. Presence of adults had significant effects on juvenile retention and interaction with organic loading in 2020, but not in 2021. To isolate the effects of adult presence on predation of juveniles, a series of laboratory experiments were carried out using the predatory crab Ovalipes catharus. Juvenile survivorship from crab predation was enhanced in the presence of large adults, consistent with the hypothesised sheltering effect. Further, predation rates increased significantly from winter to summer, which correlated with increasing water temperatures and the breeding and moult cycle of crabs. These findings across surveys, field and laboratory manipulations have significant implications for effective fisheries management and restoration of bed-forming bivalves.

Identifying the genes involved in the egg-carrying ovigerous hair development of the female blue crab Callinectes sapidus: transcriptomic and genomic expression analyses

BackgroundCrustacean female sex hormone (CFSH) controls gradually developing adult female-specific morphological features essential for mating and brood care. Specifically, ovigerous hairs are developed during the prepuberty molt cycle of the blue crab Callinectes sapidus that are essential for carrying the eggs until they finish development. Reduced CFSH transcripts by CFSH-dsRNA injections result in fewer and shorter ovigerous hairs than the control. This study aimed to identify the specific genes responsible for ovigerous hair formation using transcriptomic, genomic and expression analyses of the ovigerous setae at three stages: prepuberty at early (OE) and late premolt (OL), and adult (AO) stages.ResultsThe de novo Trinity assembly on filtered sequence reads produced 96,684 Trinity genes and 124,128 transcripts with an N50 of 1,615 bp. About 27.3% of the assembled Trinity genes are annotated to the public protein sequence databases (i.e., NR, Swiss-Prot, COG, KEGG, and GO databases). The OE vs. OL, OL vs. AO, and OE vs. AO comparisons resulted in 6,547, 7,793, and 7,481 differentially expressed genes, respectively, at a log2-fold difference. Specifically, the genes involved in the Wnt signaling and cell cycle pathways are positively associated with ovigerous hair development. Moreover, the transcripts of ten cuticle protein genes containing chitin-binding domains are most significantly changed by transcriptomic analysis and RT-qPCR assays, which shows a molt-stage specific, down-up-down mode across the OE-OL-AO stages. Furthermore, the expression of the cuticle genes with the chitin-binding domain, Rebers and Riddiford domain (RR)-1 appears at early premolt, followed by RR-2 at late premolt stage. Mapping these 10 cuticle protein sequences to the C. sapidus genome reveals that two scaffolds with a 549.5Kb region and 35 with a 1.19 Mb region harbor 21 RR1 and 20 RR2 cuticle protein genes, respectively. With these findings, a putative mode of CFSH action in decapod crustaceans is proposed.ConclusionsThe present study describes a first step in understanding the mechanism underlying ovigerous hair formation in C. sapidus at the molecular level. Overall, demonstrating the first transcriptome analysis of crustacean ovigerous setae, our results may facilitate future studies into the decapod female reproduction belonging to the suborder Pleocyemata.