Cherax Destructor Research Articles

Cherax destructor (Clark, 1836) and Cherax quadricarinatus (von Martens, 1868): Biochemical parameters and preliminary analysis of food quality

The breeding of Cherax spp., initially conducted in Australia, has aroused interest in Europe and Italy over the past two decades. The use of these species in aquaculture has led to the study of their nutritional properties to evaluate the commercial potential and to identify biochemical haemolymphatic parameters which may be of use when monitoring the health status of farmed animals. Moisture, ash, lipid, protein and fatty acid contents of the abdomen muscle of Cherax destructor and Cherax quadricarinatus were evaluated in this study and compared with other crustacean species. Haemolymphatic levels of glucose, triglycerides, cholesterol and lactate dehydrogenase were also measured. The two species did not show significant differences in nutritional or biochemical haemolymphatic parameters (except for glucose) and were found to possess good nutritional values for human consumption.

Activity, movement and habitat‐use patterns of a critically endangered endemic Australian freshwater crayfish

AbstractEstablishing the activity, movement and habitat‐use patterns of endangered species is fundamental in designing effective conservation plans. In Australia, the critically endangered freshwater crayfish, Euastacus dharawalus, is facing considerable risk of extinction due to numerous stressors, including the proliferation of the invasive Cherax destructor throughout their range. However, little is known about the fine‐scale spatial ecology of E. dharawalus and if this overlaps with C. destructor. Here, we aimed to establish the activity, movement and habitat‐use patterns of E. dharawalus as well as conduct a preliminary assessment into the overlap of their spatial ecology with that of C. destructor. In 2020, 15 E. dharawalus and six C. destructor were radio tracked at a site along Wildes Meadow Creek in the Southern Highlands region of New South Wales, Australia. Additionally, in 2021, 12 more E. dharawalus were tracked at this site over the same period. Euastacus dharawalus exhibited high site fidelity, small home ranges and diurnal activity patterns. Both E. dharawalus and C. destructor indicated significant preference for bank habitat, indicating potential for individual competitive interactions. We also report a significant reduction in the movement and activity of E. dharawalus from 2020 to 2021, possibly in response to population control of C. destructor or environmental variation across the 2 years. Our results indicate that the preservation or restoration of bank habitat will be critical to the conservation of E. dharawalus. Further, due to the extent of habitat‐use overlap between E. dharawalus and C. destructor, we conclude that C. destructor represents a substantial competitive threat to E. dharawalus, and therefore, C. destructor population control efforts should continue within the range of E. dharawalus.

Will the experimental population control of an invasive crayfish influence the diet and trophic position of a native crayfish? An assessment using stable isotopes

Context Trophic overlap between invasive and native species can cause a competitive displacement of the native. In Australian freshwaters, the invasive crayfish Cherax destructor has proliferated into the ranges of native Euastacus species. Aims To examine trophic overlap between C. destructor and the critically endangered Euastacus dharawalus and determine whether C. destructor population control causes shifts in the diet and trophic position of E. dharawalus. Methods We compared δ13C and δ15N values of tissue from both species collected from two sites. Population control of C. destructor was then conducted at one site, whereas the C. destructor population remained uncontrolled at the second site. The δ13C and δ15N values of E. dharawalus were then once again assessed. Key results Both species occupied similar trophic positions and consumed similar proportions of each food resource prior to control efforts. However, we found increases in the contribution of detritus to the diet of E. dharawalus following the removal of C. destructor, whereas no dietary shifts occurred at the uncontrolled site. Conclusions and implications The increase in detrital consumption suggests that control of C. destructor increased the availability of a preferred resource. Further, dietary competition between C. destructor and E. dharawalus is likely and reinforces C. destructor representing a substantial threat to Euastacus crayfish.

Study of the embryonic period of female crayfish egg development in different species

Freshwater crayfish farming is a promising area of production in the food market. This aquaculture industry is currently gaining popularity around the world, but given the high consumer demand, it requires modernisation. The efficiency of aquaculture production is based on the introduction of innovative methods into production processes, which are based on knowledge of biological characteristics, including reproductive capacity and the embryonic period of caviar development. The study aims to assess the reproductive quality of females and determine the incubation period of caviar, its quantity, weight, and survival rate. The study presents the results of research on the reproductive qualities and embryonic period of crayfish eggs of four species (Cherax quadricarinatus, Procambarus clarkii, Procambarus fallax forma virginalis, Cherax destructor) kept in separate closed water supply tanks at an optimal planting density of 4 individuals per 0.45 m2 . Studies have shown that the colour range of caviar and the duration of the incubation period for its maturation varies among different crayfish species. Thus, the first stage of incubation was the shortest and ranged from 2.80 (Florida crayfish) to 3.55 (destructor crayfish) days, while the second stage lasted the longest – from 13.17 to 15.80 days for Australian and broad-toed crayfish, respectively. Based on the analysis of the physiological characteristics of the female crayfish micropopulation, they were divided into quality categories, considering the following indicators: female weight, egg weight, total number of eggs, and number of eggs per 1 g of female. Females of the Australian red snapper of the excellent category was the best among all species in terms of live weight (63.0±0.67 g), egg weight (5.0±0.05 g) and total number of eggs (376.8±16.34 pcs.), the lowest similar indicators were in the marble species (16.8±0.15 g, 1.6±0.03 g, 124.5±2.66 pcs.), respectively. In terms of the number of eggs per 1 g of female weight, Florida crayfish prevailed (7.8±0.19). Instead, the destructor crayfish had intermediate results in these characteristics. The study results can be used in the economic activities of enterprises producing aquatic organisms

Comparative metabolomics analysis investigating the impact of melatonin-enriched diet on energy metabolism in the crayfish, Cherax destructor.

Melatonin is a multifunctional bioactive molecule present in almost all organisms and has been gradually used in the aquaculture industry in recent years. Energy metabolism is an essential process for individuals to maintain their life activities; however, the process through which melatonin regulates energy metabolism in aquatic animals remains unclear. The present study aimed to conduct a comprehensive analysis of the regulatory mechanism of melatonin for energy metabolism in Cherax destructor by combining metabolomics analysis with the detection of the key substance content, enzymatic activity, and gene expression levels in the energy metabolism process after culturing with dietary melatonin supplementation for 8weeks. Our results showed that dietary melatonin increased the content of glycogen, triglycerides, and free fatty acids; decreased lactate levels; and promoted the enzymatic activity of pyruvate kinase (PK), malate dehydrogenase (MDH), and acetyl-CoA carboxylase. The results of gene expression analysis showed that dietary melatonin also increased the expression levels of hexokinase, PK, MDH, lactate dehydrogenase, lipase, and fatty acid synthase genes. The results of metabolomics analysis showed that differentially expressed metabolites were significantly enriched in lysine degradation and glycerophospholipid metabolism. In conclusion, our study demonstrates that dietary melatonin increased oxidative phosphorylation, improved glucose utilization, and promoted storage of glycogen and lipids in C. destructor. These lipids are used not only for energy storage but also to maintain the structure and function of cell membranes. Our results further add to the understanding of the mechanisms of energy regulation by melatonin in crustaceans.

Dietary melatonin positively impacts the immune system of crayfish, Cherax destructor, as revealed by comparative proteomics analysis

Melatonin, an indoleamine with various biological activities, is being used increasingly in the aquaculture industry for its broad immune effects. Cherax destructor is an emerging economically cultured crayfish that faces many problems in the breeding process. Previous work found that dietary melatonin has positive effects on the growth and immunity of C. destructor, but the specific mechanism involved remained unclear. In this study, proteomics was used to determine the mechanism of action of melatonin in C. destructor. Results showed that dietary melatonin resulted in decreased levels of hydrogen peroxide, alanine aminotransferase, and aspartate aminotransferase, but increased levels of glutathione peroxidase, acid phosphatase, and glutathione S-transferases. In total, 608 proteins were differentially expressed (418 upregulated and 190 downregulated), and were enriched in three main categories: innate immunity (B cell receptor signaling pathway and natural killer cell-mediated cytotoxicity), glucose metabolism (pentose phosphate pathway, pentose and glucuronate interconversions, and propionate metabolism), and amino acid metabolism (valine, leucine, and isoleucine degradation, and cysteine and methionine metabolism). In addition, dietary melatonin was also involved in the regulation of the mTOR signaling pathway, and upregulated the expression of genes encoding key factors, such as Ras-related GTP-binding protein A/B, eukaryotic initiation factor 4E, eukaryotic initiation factor 4E-binding protein, and p70 ribosomal S6 kinase. Overall, this study demonstrates the role of melatonin in the physiological regulation of C. destructor, laying the foundation for the development of melatonin as a feed additive in the aquaculture of this species.

Effects of dietary melatonin on growth performance, antioxidant capacity, and nonspecific immunity in crayfish, Cherax destructor.

Melatonin (MT) is an indole hormone widely found in plants and animals. Many studies have shown that MT promotes the growth and immunity of mammals, fish, and crabs. However, the effect on commercial crayfish has not been demonstrated. The purpose of this study was to evaluate the effects of dietary MT on growth performance and innate immunity of Cherax destructor from three aspects of individual level, biochemical level, and molecular level after 8 weeks of culture. In this study, we found that MT supplementation increased weight gain rate, specific growth rate, and digestive enzyme activity in C. destructor compared to the control group. Dietary MT not only promoted the activity of T-AOC, SOD, and GR, increased the content of GSH, and decreased the content of MDA in the hepatopancreas, but also increased the content of hemocyanin and copper ions and AKP activity in hemolymph. Gene expression results showed that MT supplementation at appropriate doses increased the expression of cell cycle-regulated genes (CDK, CKI, IGF, and HGF) and non-specific immune genes (TRXR, HSP60, and HSP70). In conclusion, our study showed that adding MT to the diet improved growth performance, enhanced the antioxidant capacity of hepatopancreas, and immune parameters of hemolymph in C. destructor. In addition, our results showed that the optimal dietary supplementation dose of MT in C. destructor is 75-81mg/kg.

Acoustic Signals and Behavior of the Invasive Freshwater Crayfish Cherax destructor (Clark, 1936)

The study of acoustic signals in aquatic animals contributes to developing new monitoring systems based on passive acoustics and improves our knowledge of their behaviors and ecology. Here, the sounds produced by the invasive species crayfish Cherax destructor and their possible role in intraspecific interactions are analyzed. Synchronized acoustic and video monitoring systems were used in a tank to record acoustic signals and associated behavioral events (tail flips, number of encounters, number of fights) and states (velocity and distance moved, angular velocity, duration of fighting and proximity). The crayfish were monitored in seven layouts combining males (M) and females (F) (F, M, FF, MM, MF, MMF, FFM). Both males and females produced two types of acoustic signals (high- and low-frequency sounds). Grouped animals produced fewer low-frequency sounds than single animals. In a grouped layout, more sounds were recorded when animals were in proximity (distance between two specimen less than 6 cm). In a single layout, sounds were not associated with a specific event or behavioral state. The number of signals emitted in the FF group and single M group were significantly higher than those in other layouts. Our study indicates that low-frequency sounds are produced non-accidentally and provide a baseline for future tests on intraspecific acoustic communication on this species. This study could help implement low-cost passive acoustic monitoring able to identify this species and the possible negative effect of its dispersion in a non-native environment.

Comparative ultrastructure of the antennae and sensory hairs in six species of crayfish.

Antennae in crayfish are essential for gaining information about the local topography and localising food, chemicals, conspecifics or predator. There are still gaps in the research on the morphology of antennae in decapods compared to other arthropods. Biometrical and ultrastructural methods were applied using light and cryo-scanning electron microscopies to study the morphology of antennae in six different crayfish species, including marbled crayfish Procambarus virginalis, Mexican dwarf crayfish Cambarellus patzcuarensis, red swamp crayfish Procambarus clarkii, signal crayfish Pacifastacus leniusculus, common yabby Cherax destructor, and spiny-cheek crayfish Faxonius limosus to find their potential morphological differences. Significant differences in the antenna length, length and width of each segment to carapace length ratios, and the number of segments were found in the six crayfish species. The ultrastructure revealed differences in the distribution of sensory hairs on the antenna and the morphology of the antennal surface. The different morphology of antennae might reflect adaptation to the conditions of their specific habitats. In addition, results showed that a combination of differences in the morphological features and biometrical measurements of antennae could be used for the distinguishment of different studied crayfish species.

Further Insights into Invasion: Field Observations of Behavioural Interactions between an Invasive and Critically Endangered Freshwater Crayfish Using Baited Remote Underwater Video (BRUV).

Competitive behavioural interactions between invasive and native freshwater crayfish are recognised as a key underlying mechanism behind the displacement of natives by invaders. However, in situ investigations into behavioural interactions between invasive and native crayfish are scarce. In Australian freshwater systems, the invasive Cherax destructor has spread into the ranges of many native Euastacus species, including the critically endangered Euastacus dharawalus. Staged contests between the two species in a laboratory setting found E. dharawalus to be the dominant competitor, however, this has yet to be corroborated in situ. Here, we used baited remote underwater video (BRUV) to examine in situ intra- and inter-specific behavioural interactions between E. dharawalus and C. destructor. We sought to evaluate patterns of dominance and differential contest dynamics between the species to provide indications of competition between the two species. We found E. dharawalus to be dominant over C. destructor based on pooled interspecific interaction data and size-grouped interactions where C. destructor was the smaller opponent. Alarmingly, however, when C. destructor was within a 10% size difference the dominance of E. dharawalus was lost, contrasting with the outcomes of the laboratory-staged study. In addition, we report that small C. destructor initiated significantly more contests than larger conspecifics and larger E. dharawalus, a pattern that was not observed in smaller E. dharawalus. Further, intraspecific interactions between C. destructor were significantly longer in duration than intraspecific interactions between E. dharawalus, indicating a willingness to continue fighting. Concerningly, these outcomes point towards inherent and greater aggressiveness in C. destructor relative to E. dharawalus and that only larger E. dharawalus hold a competitive advantage over C. destructor. Therefore, we conclude that C. destructor represents a substantial threat to E. dharawalus through competitive behavioural interactions. Further, due to the disparity between our findings and those produced from laboratory-staged contests, we recommend the use of in situ studies when determining the behavioural impacts of invasive crayfish on natives.

Effects of temperature on the growth parameters, hepatopancreas structures, antioxidant ability, and non-specific immunity of the crayfish, Cherax destructor

Effects of temperature on the growth parameters, hepatopancreas structures, antioxidant ability, and non-specific immunity of the crayfish, Cherax destructor

Effects of Low Temperature on Antioxidant and Heat Shock Protein Expression Profiles and Transcriptomic Responses in Crayfish (Cherax destructor).

Low temperature is a critical factor restricting the growth and survival of aquatic animals, but research on the mechanism of response to low temperature in Cherax destructor is limited. C. destructor is one of the most important freshwater crustaceans with strong adaptability in Australia, and it has been commercialized gradually in recent years. Here, growth indicators, antioxidant parameters, anti-stress gene expression, and transcriptome sequencing were used on crayfish following 8 weeks of low-temperature acclimation. The results showed that weight gain, length gain, and molting rates decreased as the temperature decreased. The activity of antioxidant enzymes decreased, while the content of antioxidant substances and the expression of anti-stress genes increased. Transcriptome sequencing identified 589 differentially expressed genes, 279 of which were upregulated and 310 downregulated. The gene functions and pathways for endocrine disorders, glucose metabolism, antioxidant defense, and immune responses were identified. In conclusion, although low-temperature acclimation inhibited the basal metabolism and immune ability of crayfish, it also increased the antioxidant substance content and anti-stress-gene expression to protect the organism from low-temperature damage. This study provided molecular insights into the study of low-temperature responses of low-temperature-tolerant crustacean species.

Temperature and body size influence personality and behavioural syndromes in an invasive crayfish

The presence of repeatable behaviours that vary between individuals (animal personality) and the mechanisms that underpin these behaviours are of significant ecological and evolutionary importance. With current climatic trends predicted to facilitate biological invasions, we sought to examine how personality and behavioural syndromes may influence invasion potential in the face of a changing climate. We assessed a population of an invasive crayfish, Cherax destructor , in a laboratory setting for (1) the presence of temporally and contextually repeatable behavioural differences between individuals along three axes: (i) activity, (ii) boldness/shyness and (iii) exploration/avoidance, (2) correlations between body size, sex and behavioural traits at the between-individual level, (3) the influence of predicted near-future increases in temperature on personality and (4) the presence of behavioural syndromes (between-individual correlations among behaviours). Individuals exhibited repeatable variation along the three behavioural axes, providing support for the presence of animal personality. Body size was negatively correlated with exploration and activity, but sex was unrelated to personality across the three axes. Exploration increased with temperature, whereas the effect of temperature on activity was dependent on the treatment order. Finally, activity and exploration were positively correlated, indicative of a behavioural syndrome. This study provides evidence of state-dependent personality and support for the existence of behavioural syndromes which may facilitate biological invasions. Our work also provides evidence to suggest that predicted future increases in temperature will promote exploratory behaviour in invasive populations of C. destructor . • Invasive Cherax destructor exhibited personality along three behavioural axes. • Body size was negatively correlated with both active and exploratory behaviour. • Exploration of a novel environment increased at predicted near-future temperatures. • Correlations between behaviours provide evidence of an invasive syndrome. • Increasing exploration with temperature may increase future invasive potential.

Diversity and Distribution of the Inland Water Decapods of Sicily (Crustacea, Malacostraca)

The current knowledge of Sicilian inland water decapod malacostracans is scarce and an updated synopsis on species distribution is lacking. Therefore, we reviewed the checklist and recent distribution of Sicilian inland water decapods based on published and unpublished records and novel observations with the aim of providing an exhaustive repository, also to be used as a sound baseline for future surveys. Overall, five native decapod species occur in the study area, i.e., the atyid shrimp Atyaephyra desmarestii, the palaemonid shrimps Palaemon adspersus, P. antennarius, and P. elegans, and the freshwater crab Potamon fluviatile, and their current local distributions are described. In addition, three alien species were recorded: the common yabby Cherax destructor and the red swamp crayfish Procambarus clarkii, strictly linked to inland waters, and the Atlantic blue crab Callinectes sapidus, a mainly marine species that can also colonise the lower stretches of rivers and coastal brackish waters. The collected data suggest the existence of a partial segregation of native versus non-native species, with the latter currently confined to coastal water bodies and the lower stretches of rivers. Moreover, the exclusively freshwater caridean A. desmarestii and P. antennarius show a parapatric distribution in the study area, which may suggest the existence of mutual exclusion phenomena. The results obtained raise some concerns about the effects of alien species on the native biota, and dedicated monitoring and management strategies should be implemented in order to better understand and mitigate their impact.

Moult cycle staging in decapod crustaceans (Pleocyemata) and the Australian crayfish, Cherax destructor Clark, 1936 (Decapoda, Parastacidae)

Abstract We tabulated decades of published moult stage criteria of Decapoda: Pleocyemata on setogenesis and changes in pleopods, uropods and gastroliths; and reviewed them focusing on the comparative biology of Cherax destructor. We found their staging criteria relatively consistent. For C. destructor, lacking were a comprehensive description with micrographs; a juvenile application; and, known stage duration. Therefore, we developed comprehensive moult staging techniques in juvenile C. destructor using pleopods, antennules and gastroliths. Using pleopod staging, we found C. destructor exhibits anecdysis as a true transition stage (D0), which occupied around half the moult cycle. We successfully applied this method to juvenile and adult marbled crayfish. We report on these suggested novel techniques: moult staging using pleopods: novel in crayfish; moult staging using antennules: novel in decapods; moult staging using gastrolith deposition: novel in C. destructor; and, calculating the gastrolith moult mineralization index using height: novel in decapods.

Does habitat complexity and prior residency influence aggression between invasive and native freshwater crayfish?

AbstractAggressive encounters between invasive and native species are considered a key threat associated with the spread of invasive species. Extrinsic factors such as habitat complexity can profoundly influence the outcome of aggressive interactions between conspecifics, and this may also be the case in invasive‐native species interactions. This study used invasive and native freshwater crayfish species in Australia as a model system to investigate the influence of habitat complexity on aggression in both intraspecific and interspecific contests. Paired contests between the native Euastacus spinifer and the invasive Cherax destructor were conducted in the laboratory under high and low habitat complexity conditions. Furthermore, the influence of prior residency was examined, with one individual assigned the resident and the other as the intruder. In intraspecific contests, the number of interactions and aggression score were significantly reduced under high complexity conditions; however, complexity had no effect on the time spent interacting and contest outcome. Instead, the two crayfish species differed in terms of time spent interacting. In interspecific contests, complexity had no effect on any of the aggression metrics. Alarmingly, however, we demonstrate that when C. destructor was a resident the likelihood that E. spinifer won a contest fell to a mere 8% compared to 31% when E. spinifer was resident. This study suggests that while habitat complexity plays a role in shaping aggressive behaviour in intraspecific interactions, invasive species are competitively dominant if they are already established i.e. resident in a location and even as intruders. Therefore, preserving habitat complexity in freshwater systems may not be sufficient to sustain populations of native species, and other measures that mitigate the potential for range overlap between the species would also be needed to prevent the further spread of invasive species such as C. destructor within freshwater ecosystems.

Dietary fatty acid profiles shape crayfish biosynthesis and performance: Implications for riverine food webs

Abstract Alteration of riverine flows can modify the structure and function of ecosystems, changing energy pathways and patterns of micronutrient transfer between trophic levels. Fatty acids (FAs) commonly are used to evaluate food quality, since some FAs required for somatic growth and physiological functions in animals must be obtained from their diet. FAs also are used in food‐web studies as biotracers as a consequence of their constrained metabolic biosynthesis by animals. However, their utility may be confounded by selective retention or modification of dietary FAs by consumers. We conducted a 70‐day feeding trial to compare growth and survival of an abundant and widespread mesoconsumer (Cherax destructor, the common yabby or crayfish) fed three contrasting diets: a poor‐quality detritus‐based diet; a high protein invertebrate diet; and a high‐quality commercial aquaculture pellet. Fatty acid profiles were obtained for each dietary treatment and contrasted with crayfish FA profiles at the end of the experiment to examine patterns of FA retention and integration. We also collected wild crayfish from floodplain wetland and river habitats, and obtained FA profiles from their stomach contents and body tissue to compare with experimental crayfish. Experimental crayfish fed high‐quality commercial pellets doubled in mass during the 70‐day assay, invertebrate fed crayfish growth was intermediate, and growth of crayfish fed detritus was negligible. Fatty acid profiles of crayfish fed our three contrasting diets differed significantly at the end of the experiment. Proportions of the polyunsaturated omega‐6 FA linoleic acid (LIN, 18:2ω6) in crayfish followed the same inequality observed in growth and diets: pellets > invertebrates > detritus. Pellet‐fed crayfish preferentially assimilated greater proportions of FAs 20:4ω6 (ARA), 20:5ω3 (EPA) 18:1ω9 (OA) and 16:1ω7 (POA) into their tissue. Fatty acid profiles of floodplain crayfish differed to profiles of riverine crayfish, and floodplain crayfish had higher proportions of essential FAs ARA and LIN in their tissues. Fatty acid biosynthesis by crayfish was best described by a hypothesis of FA allostasis rather than homeostasis; in this, FA profiles of crayfish were shaped by their diet, and selective integration and modification of high‐quality FAs from basal resources rich in these micronutrients led to higher proportions in crayfish tissues. Here we present evidence for the conversion of shorter‐chain essential FAs by freshwater crayfish to compensate for a lack of long‐chain FAs in their diet. We provide a necessary step for improving our understanding of micronutrient dynamics and the transfer of essential molecules between trophic levels in lowland river food webs. Floodplain habitats are known to provide higher‐quality basal food resources for mesoconsumers than riverine habitats, and here we identify one mechanism by which that may be extended to subsequent trophic levels.

Haemolymphatic Parameters in Two Aquaculture Crustacean Species Cherax destructor (Clark, 1836) and Cherax quadricarinatus (Von Martens, 1868).

Simple SummaryThe spread of freshwater crustacean farms, in particular of the Australian species Cherax, has been widespread in recent years and has aroused particular interest at an economic level. Knowledge of the basic levels of some biochemical parameters becomes particularly important to understanding the health status of the animals and, therefore, for the maintenance of aquaculture facilities. In this study, the values of some biochemical parameters of two species of Cherax, Cherax destructor and Cherax quadricarinatus, reared in an Italian aquaculture plant, were evaluated for the first time. These parameters should contribute to assessing the health status of these animals on a farm and to understanding if they will be affected by stressful conditions or not.In the last few years, there has been a notable development in the breeding of freshwater shrimp (astaciculture), which involved various species and in particular, the two Australian Parastacidae species, Cherax destructor and Cherax quadricarinatus. Information about the haemolymphatic parameters of these two species is fragmentary, and filling these gaps becomes important given their importance in aquaculture. Cellular and biochemical parameters were analyzed in both species to create a reference baseline for these parameters to identify the state of welfare or suffering of these animals. The results showed that the total haemocyte count, haemocyte subpopulations, enzymatic activities and pH are similar between the two species, while total protein and osmolality are higher in C. destructor than C. quadricarinatus. Knowledge of these parameters could assist in evaluating the good health status of these species kept in aquaculture facilities.

The NGS Magic Pudding: A Nanopore-Led Long-Read Genome Assembly for the Commercial Australian Freshwater Crayfish, Cherax destructor.

Cherax destructor, the yabby, is an iconic Australian freshwater crayfish species, which, similar to other major invertebrate groups, is grossly under-represented in genomic databases. The yabby is also the principal commercial freshwater crustacean species in Australia subject to explotation via inland fisheries and aquaculture. To address the genomics knowledge gap for this species and explore cost effective and efficient methods for genome assembly, we generated 106.8 gb of Nanopore reads and performed a long-read only assembly of the Cherax destructor genome. On a mini-server configured with an ultra-fast swap space, the de novo assembly took 131 h (∼5.5 days). Genome polishing with 126.3 gb of PCR-Free Illumina reads generated an assembled genome size of 3.3 gb (74.6% BUSCO completeness) with a contig N50 of 80,900 bp, making it the most contiguous for freshwater crayfish genome assemblies. We found an unusually large number of cellulase genes within the yabby genome which is relevant to understanding the nutritional biology, commercial feed development, and ecological role of this species and crayfish more generally. These resources will be useful for genomic research on freshwater crayfish and our methods for rapid and super-efficient genome assembly will have wide application.

Postembryonic development in freshwater crayfish (Decapoda: Astacidea) in an evolutionary context

Detailed morphology of the first three postembryonic developmental stages (Stages I-III juvenile) in representatives from all four crayfish families, Austropotamobius torrentium (von Paula Schrank, 1803) (Astacidae), Procambarus virginalis Lyko, 2017 (Cambaridae), Cambaroides japonicus (De Haan, 1841 [in De Haan, 1833-1850]) (Cambaroididae) and Cherax destructor Clark, 1936 (Parastacidae) are described and the diagnostic characters for each family are indicated. A phylogenetic tree of freshwater Astacidea, based on these new diagnostic juvenile characters is constructed to suborder, superfamily and family levels, and compared with a molecular phylogenetic tree. The evolutionary history of maternal care in freshwater crayfish is discussed based on particular features of the postembryonic stages of each family. Using comparisons between the phylogenetic tree and global geo-history, the location and timing of the early evolution of maternal care in postembryonic development and the extension of this care are estimated.