Shell Hardness Research Articles

Mechanical Characteristics of Bivalve (Mollusc) Shells from the East Coast of India: Implications and Their Significance on the Survival Strategy

Due to natural selection, an increase in biotic and abiotic factors develops an adaptive response in bivalves (molluscs) for survival. Morphological variation in a bivalve is strongly correlated with the changes in the structural and compositional properties of a shell. Therefore, the mechanical characteristics of a shell reflect its morpho-functional adaptation against predation and ecological stresses. An initial investigation into the primary mechanical attributes of predominant bivalve shells from the east coast of India, Tegillarca granosa, Meretrix meretrix, Sunetta meroe, Mactra turgida and Donax scortum, has been documented in this study. The quantitative assessment of the centreline thickness, Vickers hardness and density variation of the shells were measured and correlated along with the preliminary investigation of the microstructural patterns. The results from our study are in agreement with the most vulnerable region of a shell, located just below the umbonal zone, which has been verified through predatory boreholes in other studies. Our data shows a high correlation between shell hardness and density, which could also be the potential properties to consider in detail for future studies, apart from the shell thickness, which could provide a broader perspective on the stability of bivalve shells. Different microstructural patterns observed in the species could be phylogenetically driven based on their life modes.

Lobster quality indicators for grading

AbstractMale lobsters (Homarus americanus) harvested as ‘quarters’ (1.25 lbs/567 g) in two time periods (winter, N = 16, and summer, N = 25) of 2018 are examined. Indicators of quality data were collected for each lobster, including non‐invasive measures (shell hardness, carapace length, sex, live weight, colour, body shape, location, time of harvest) and invasive measures (blood protein [BRIX] level at time of harvest, cooked weight, meat content). Lobster BRIX levels are used as a proxy for actual meat content and as the key indicator of lobster quality. A regression model of the relationship between the natural logarithmic transformation of lobster BRIX levels (independent variable) and meat content yield as a percentage of shell‐on (uncooked) weight (dependent variable) is presented. The objective of this study is to evaluate alternative BRIX‐based decision rules for achieving desired meat content percentage yields for preparing shipments to global markets. The present study found that BRIX‐based grading rules can be determined to achieve minimum desired meat yields, minimum overall shipment yields and minimum proportions of shipments below desirable yield rate. For a minimum desired industry threshold of 24% meat content, the preferred BRIX value rules are (i) 8.5 mg mL−1 and (ii) ‘9 mg mL−1 with 10% plus condition’. These rules improve the admissibility of samples and reduce the risk of below desirable meat yields.

Impact of ocean acidification on shells of the abalone species Haliotis diversicolor and Haliotis discus hannai

Ocean acidification (OA) results from the absorption of anthropogenic CO2 emissions by the ocean and threatens the survival of many marine calcareous organisms including molluscs. We studied OA effects on adult shells of the abalone species Haliotis diversicolor and Haliotis discus hannai that were exposed to three pCO2 conditions (ambient, ∼880, and ∼1600 μatm) for 1 year. Shell periostracum corrosion under OA was observed for both species. OA reduced shell hardness and altered the nacre ultrastructure in H. diversicolor, making its shells more vulnerable to crushing force. OA exposure did not reduce the shell hardness of H. discus hannai and did not alter nacre ultrastructure. However, the reduced calcification also decreased its resistance to crushing force. Sr/Ca in the shell increased with rising calcification rate. Mg/Ca increased upon OA exposure could be due to a complimentary mechanism of preventing shell hardness further reduced. The Na/Ca distribution between the aragonite and calcite of abalone shells was also changed by OA. In general, both abalone species are at a greater risk in a more acidified ocean. Their shells may not provide sufficient protection from predators or to transportation stress in aquaculture.

Competition between two congener invaders: Food conditions drive the success of the quagga over zebra mussel in a large shallow lake

Abstract Dreissena rostriformis bugensis (quagga mussel, QM) has spread into areas occupied by an earlier invader, Dreissena polymorpha (zebra mussel, ZM) in Europe and North America. Usually QM displaces ZM within a few years or both species coexist, although the mechanisms driving these outcomes have not been uncovered clearly. In Lake Balaton (central‐eastern Europe), QM displaced ZM in the oligotrophic (food‐limited) basin, whereas they coexist in the eutrophic (food‐rich) basin. Searching for the drivers of interactions in dreissenid assemblages, we compared survival, growth, allometry, shell hardness, biomacromolecule content and superoxide dismutase (SOD) expression (indicating nutrition stress) of dreissenids collected in both basins in a field survey, and in individuals collected from the food‐rich basin and experimentally transplanted (10 weeks) to the food‐limited or food‐rich (i.e. the same) basin. In the field survey, QM from the food‐rich basin showed the greater height increment per unit length than coexisting ZM and food‐limited conspecifics. ZM had the hardest shells of all the mussel populations. In the food‐rich basin, ZM did not differ from QM in weight, protein, and carbohydrate contents, but had higher lipid content and SOD expression. Food‐limited QM, compared to conspecifics from the food‐rich basin, had weaker shells, but their protein, carbohydrate, and lipid contents showed faster increments per unit size, thus adults made up for the initial advantage of the food‐rich population. QM survived better than ZM after transplantation irrespective of the basin. Shells were harder in ZM versus QM and in the food‐rich versus food‐limited conditions. QM grew at both locations, whereas ZM only in the food‐rich basin. The protein and carbohydrate contents were greater in the food‐rich versus food‐limited basin, with no interspecific differences. Lipid content in QM was higher in the food‐limited versus food‐rich basin, whereas the opposite held for ZM. We demonstrated that the dreissenid species could coexist in food‐rich conditions, despite the higher level of stress in ZM (as shown by weaker survival, higher SOD expression), whereas QM displaced ZM under food‐limiting conditions, probably due to the ability to replace missing storage carbohydrates with accumulated lipids. Nevertheless, QM from the food‐limited basin also showed symptoms of nutritional stress (changes in biomacromolecule content, lower shell hardness). Results suggest that the ability to show a rapid change in metabolism could be an important advantage of QM over ZM in their competition.

Selection of superior late-blooming almond (Prunus dulcis [Mill.] D.A.Webb) genotypes using morphological characterizations.

Almond (Prunus dulcis [Mill.] D.A.Webb) is one of the earliest domesticated trees and the evidence dates back to 3000-2000 BC. In the present study, 198 almond seedling origin trees were studied to select late-flowering genotypes having high kernel quality. Significant variabilities were exhibited among the genotypes investigated based on the recorded traits. Full-blooming date ranged from mid-March to mid-April. The Ward dendrogram clustered the genotypes into two major clusters forming several subclusters. After clustering the genotypes based on the full-blooming dates, 68 late-blooming genotypes were recognized and reanalyzed based on the quantitative characters to select the superior ones. Nut-related characters were as follows: nut length: 22.34-43.05 mm, nut width: 14.07-24.34 mm, nut thickness: 9.21-18.00 mm, nut weight: 1.88-6.62 g, and shell thickness: 2.26-4.59 mm. Kernel-related characters were as follows: kernel length: 16.73-25.91 mm, kernel width: 8.50-13.64 mm, kernel thickness: 3.56-7.37 mm, and kernel weight: 0.35-1.41 g. Kernel weight was positively and significantly associated with nut weight, kernel thickness, kernel length, kernel width, nut length, and branch leaf width. Thus, these key variables are the main traits accounting for kernel weight, and they should be considered together in breeding with aiming at increasing the kernel weight. Based on ideal values of the important and commercial characters of almond, such as fruit yield, nut weight, shell hardness, kernel shape, kernel weight, and kernel taste, 19 late-blooming genotypes were promising and are recommended for cultivation in orchards.

Multiple interacting factors affect seed predation in an African savanna small mammal community

Abstract Multiple factors affect seed predation, including seed traits, habitat type, seed predator community composition, predation risk, and seasonality. How all these factors and their interactions simultaneously influence seed predation has rarely been tested experimentally in situ. Here, we assessed the relative contribution of the factors driving seed predation in an African savanna rodent community, comprising six ecologically similar species. We first conducted seed preference tests under semicaptive conditions to determine which seed trait (size, shell hardness, nutritional content) influenced seed predation. Then we performed in situ experiments to establish whether rodent community composition (diversity and abundance), seed type, habitat type, seasonality, predation risk, and their interactions affected seed predation. Semicaptive experiments showed that rodents preferred smaller, lighter seeds, containing relatively high water content. In situ experiments showed that predation risk was an important factor influencing seed predation, with rodents removing considerably more seeds in areas where predation risk was lower. Habitat type also affected seed predation, but its effects were strongly linked to predation risk. In areas where predation risk was higher, rodents removed more seeds in more heterogeneous habitats, whereas in areas where predation risk was lower, rodents removed more seeds in less heterogeneous habitats. Seasonality was the least influential factor shaping seed predation. Rodents removed more seeds in winter compared to other seasons, but only in areas where predation risk was low. We provide experimental evidence for a multifaceted approach to understanding the relative contribution of the different factors driving variation in seed predation in natural communities and show that these factors are likely hierarchically arranged.

Growth and shell hardness of the apple snail Pomacea flagellata Say, 1829, reared at three calcium concentrations.

The snail Pomacea flagellata inhabits aquatic systems with high calcium concentration and it is important to food webs; unfortunately, its natural populations are decreasing due to overfishing and habitat destruction. Here we tested the effect of three water calcium concentrations on the growth and hardness of snail shells in triplicate recirculation culture systems for 12 weeks. In each culture, 100 juvenile snails were seeded at constant density and fed with balanced tilapia feed. Thirty snails were randomly collected every 15 days and measured in length and total weight. The size, weight, and shell hardness of the snails for the 500 mg/L calcium treatment were significantly higher than the mean size of the snails in the other treatments (300 mg/L and 243.33 mg/L). The calcium supply in the culture promotes growth and allows the snails to produce healthier and stronger shells, in addition to improving their growth rate, which is important for the management of the species.

Genome-wide association analysis and validation with KASP markers for nut and shell traits in almond (Prunus dulcis [Mill.] D.A.Webb)

Almond shell hardness is an economically important quality trait that protects the integrity of the kernel. It is directly related with shelling or crack-out percent. In the U.S. and Australian markets, soft to semi-hard shells varieties have been used in the industry, while in the European market, hard shells are dominantly sold and distributed. The origin of a hard shell is from wild almond species. Soft shells in the USA and Australia have been selected for a higher crack-out percent or larger kernel and ease of processing. Here, we examined breeding populations totaling 264 trees that were genotyped with genotyping-by-sequencing (GBS) where shell hardness was measured with a texture analyzer, and shell weight, in-shell weights and shell thickness were measured and crack-out percent was calculated. In a genome-wide association, seven genetic loci were found to be associated with shell hardness, crack-out percent, shell thickness and shell weight. Of these seven, one was shared between multiple traits. Kompetitive allele-specific PCR (KASP) assays were developed and tested in unrelated breeding lines from Australia, Spain, France and Italy. One KASP assay was found to be highly predictive of shell hardness in this diverse panel and can be applied for use in marker-assisted breeding.

Effect of Aquaculture-Related Diets on the Long-Term Performance and Condition of the Rock Crab, Cancer irroratus

Shellfish and salmonid aquaculture operations in Eastern Canada attract several mobile epibenthic species as a result of added structural complexity and increased food availability (bivalve fall-off and waste salmonid feed). It is not clear whether the aggregation of predators and scavengers below coastal farms contributes positively or negatively to their population dynamics, due to concerns about the quality of food items found under farms. We conducted an 18-month laboratory study to investigate the effect of diets composed of 1) mixed items, 2) mussels (Mytilus edulis), and 3) salmonid feed on the performance and condition of the rock crab,Cancer irroratus. Diet had no impact on crab survival but several negative consequences were observed in crabs fed the salmonid feed diet when compared to the mixed diet: reduced 1) moulting rates during the second growing season, 2) inter-molt growth, 3) gonad and hepatopancreas indices, 4) hemolymph dissolved compounds, 5) hepatopancreatic glycogen, and 6) shell hardness. Crabs fed the mussel diet had similar performance and condition when compared to the mixed diet. Fatty acid composition of muscle, gonad, and hepatopancreas tissues revealed that a salmonid feed diet decreased n3/n6 ratio when compared to a mixed or a mussel diet; those differences were mostly due to increases in the proportions of terrestrial (18:1n9 and 18:2n6) and decreases in proportions of marine essential (20:5n3 and 22:6n3) fatty acids. Together, these results point to a minimal impact of a mussel-only diet on crabs, whereas the salmonid feed diet resulted in negative impacts on condition. Our experimental results explored the consequences of a ‘worst-case scenario’ in which crabs were forced to feed on a single item for a long period of time; the realized impact in field settings will depend on other factors such as consumption of alternate food items underneath a farm, proportion of time spent in farms, and level of overlap between crab habitat and aquaculture facilities.

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.

Shell Disorder Models Detect That Omicron Has Harder Shells with Attenuation but Is Not a Descendant of the Wuhan-Hu-1 SARS-CoV-2.

Before the SARS-CoV-2 Omicron variant emergence, shell disorder models (SDM) suggested that an attenuated precursor from pangolins may have entered humans in 2017 or earlier. This was based on a shell disorder analysis of SARS-CoV-1/2 and pangolin-Cov-2017. The SDM suggests that Omicron is attenuated with almost identical N (inner shell) disorder as pangolin-CoV-2017 (N-PID (percentage of intrinsic disorder): 44.8% vs. 44.9%—lower than other variants). The outer shell disorder (M-PID) of Omicron is lower than that of other variants and pangolin-CoV-2017 (5.4% vs. 5.9%). COVID-19-related CoVs have the lowest M-PIDs (hardest outer shell) among all CoVs. This is likely to be responsible for the higher contagiousness of SARS-CoV-2 and Omicron, since hard outer shell protects the virion from salivary/mucosal antimicrobial enzymes. Phylogenetic study using M reveals that Omicron branched off from an ancestor of the Wuhan-Hu-1 strain closely related to pangolin-CoVs. M, being evolutionarily conserved in COVID-19, is most ideal for COVID-19 phylogenetic study. Omicron may have been hiding among burrowing animals (e.g., pangolins) that provide optimal evolutionary environments for attenuation and increase shell hardness, which is essential for fecal–oral–respiratory transmission via buried feces. Incoming data support SDM e.g., the presence of fewer infectious particles in the lungs than in the bronchi upon infection.

Identification and functional analysis of the estradiol 17β-dehydrogenase gene on the shell hardness of Scylla paramamosain during the molting cycle

Estradiol 17 β-dehydrogenase (17E2DH) is an oxidoreductase gene involved in the metabolism of androgen and estrogen in mammals and birds, and is also associated with molting in crustaceans. However, neither the full-length estradiol 17 β-dehydrogenase nor its molecular mechanism during molting has been reported in crabs. In this study, the cDNA encoding 17-beta-dehydrogenase was cloned from the hepatopancreas of Scylla paramamosain and named Sp17E2DH. The full length Sp17E2DH consists of 922 bp with an open reading frame encoding 255 amino acids. Phylogenetic analysis showed that the predicted Sp17E2DH protein is conserved and clustered with the 17E2DH from other crustacean species. RT-qPCR and immunohistochemistry analyses indicated that the expression level of Sp17E2DH was lowest before molting (TQ), up-regulated at 3 h after molting (TH3h), and highest at 48 h after molting (TH48h) in the hepatopancreas and muscles. An RNA interference experiment showed that the mRNA expression level of Sp17E2DH was significantly down-regulated (P < 0.05) and the hardness of crab shells was significantly decreased (P < 0.05) at TH48h in the hepatopancreas and muscles after injection of Sp17E2DH-targeted dsRNA. Genes such as gastrolith protein (P = 0.045), cuticular protein 15 (P = 0.021), chitin synthase (P = 0.047) and troponin C2 (P = 0.013) were significantly suppressed at TH48h after Sp17E2DH dsRNA injection compared to the control groups, which were potentially regulated by Sp17E2DH to control shell hardness of S. paramamosain. In summary, the results suggest that Sp17E2DH plays a vital role in the molting cycle and shell hardening of the mud crab, and the dsRNA interference of Sp17E2DH may be used to prolong the marketing shelf life of live soft-shelled mud crabs.

Plasticity in organic composition maintains biomechanical performance in shells of juvenile scallops exposed to altered temperature and pH conditions

The exposure to environmental variations in pH and temperature has proven impacts on benthic ectotherms calcifiers, as evidenced by tradeoffs between physiological processes. However, how these stressors affect structure and functionality of mollusk shells has received less attention. Episodic events of upwelling of deep cold and low pH waters are well documented in eastern boundary systems and may be stressful to mollusks, impairing both physiological and biomechanical performance. These events are projected to become more intense, and extensive in time with ongoing global warming. In this study, we evaluate the independent and interactive effects of temperature and pH on the biomineral and biomechanical properties of Argopecten purpuratus scallop shells. Total organic matter in the shell mineral increased under reduced pH (~ 7.7) and control conditions (pH ~ 8.0). The periostracum layer coating the outer shell surface showed increased protein content under low pH conditions but decreasing sulfate and polysaccharides content. Reduced pH negatively impacts shell density and increases the disorder in the orientation of calcite crystals. At elevated temperatures (18 °C), shell microhardness increased. Other biomechanical properties were not affected by pH/temperature treatments. Thus, under a reduction of 0.3 pH units and low temperature, the response of A. purpuratus was a tradeoff among organic compounds (biopolymer plasticity), density, and crystal organization (mineral plasticity) to maintain shell biomechanical performance, while increased temperature ameliorated the impacts on shell hardness. Biopolymer plasticity was associated with ecophysiological performance, indicating that, under the influence of natural fluctuations in pH and temperature, energetic constraints might be critical in modulating the long-term sustainability of this compensatory mechanism.

Comparison of growth, survival and fertility of the southern and northern populations of Crassostrea ariakensis and their hybrids in southern China

Crassostrea ariakensis is widely distributed in the estuaries of China and has the advantages of wide salinity adaptation and strong resistance, but the artificial aquaculture of C. ariakensis is mainly concentrated in southern China. Long-term geographical isolation resulted in genetic variation between the northern and southern C. ariakensis populations. In this study, the reproductive isolation between two independent population of C. ariakensis was evaluated by hybridization. Results showed that the fertilization rate, cleavage rate and D Larval rate of interpopulation hybrids (NS- northern ♂ × southern ♀ and SN- southern ♂ × northern ♀) were significantly lower than those of intrapopulation inbreed groups (SS and NN). Moreover, southern maternal larvae (SS and NS) have significant survival advantages. The growth trend between the two sites was very different in early stage (from 90th to 210th day), but it was consistent in late stage (from 210th to 480th day), with a significant decreasing trend of SS > NS > SN > NN. The survival rates of SN and NS was significantly higher than that of NN, indicating that the high temperature tolerance and stress resistance of hybrids were improved. The positive maternal effect advantages (MEAs) at most time points of both sites demonstrated that parental origin, especially the maternal origin, had a significant effect on the survival and growth of progeny. Hybrid advantages (HAs) for growth of both sites were opposite, and positive HAs of survival accounted for most of both sites, indicating that environmental conditions and survival could significantly affect the growth, and interpopulation hybrids did not necessarily always show positive HAs. Moreover, the maternal origin would affect the shell shape and shell hardness, resulted in NS similar to SS and SN similar to NN, respectively. Additionally, all interpopulation hybrids could produce mature gametes. These results confirmed that there was no serious reproductive isolation between the two populations. The southern maternal groups, especially SS, had better growth and survival advantages, could be used as good new strains for large-scale breeding in southern China, and also provided basic data for the commercial promotion of C. ariakensis in southern China.

Toxicity of two drugs towards the marine filter feeder Mytilus spp, using biochemical and shell integrity parameters

The increasing presence of anthropogenic contaminants in the environment may constitute a challenge to non-target biota, considering that most contaminants can exert deleterious effects. Salicylic acid (SA) is a non-steroid anti-inflammatory drug (NSAID) which exerts its activity by inhibiting the enzyme cyclooxygenase (COX). Another class of drugs is that of the diuretics, in which acetazolamide (ACZ) is included. This pharmaceutical acts by inhibiting carbonic anhydrase (CA), a key enzyme in acid-base homeostasis, regulation of pH, being also responsible for the bio-availability of Ca2+ for shell biomineralization processes. In this work, we evaluated the chronic (28-day) ecotoxicological effects resulting from the exposures to SA and ACZ (alone, and in combination) on individuals of the marine mussel species Mytillus spp., using enzymatic (catalase (CAT), glutathione S-transferases (GSTs), COX and CA), non-enzymatic (lipid peroxidation, TBARS levels) and morphological and physiological (shell hardness, shell index and feeding behaviour) biomarkers. Exposure to ACZ and SA did not cause significant alterations in CAT and GSTs activities, and in TBARS levels. In terms of CA, this enzyme was inhibited by the highest concentration of ACZ in gills of exposed animals, but no effects occurred in the mantle tissue. The activity of COX was not altered after exposure to the single chemicals. However, animals exposed to the mixture of ACZ and SA evidenced a significant inhibition of COX activity. Morphological and physiological processes (namely, feeding, shell index, and shell hardness) were not affected by the here tested pharmaceutical drugs. Considering the general absence of adverse effects, further studies are needed to fully evaluate the effects of these pharmaceutical drugs on alternative biochemical and physiological pathways.

An intrapopulational study of organic compounds and biomechanical properties of the shell of the Antarctic bivalve Laternula elliptica (P. P. King, 1832) at King George Island

Laternula elliptica is a key bivalve species and widely distributed around the Antarctic continent. This bivalve has been the study subject in several studies centered on ecological, physiological, biochemical, and behavioral patterns. However, little is known about the chemistry and the biomechanical properties of the shells of this mollusk. Here, we present the first report of the intra-population variability in the organic composition and mechanical properties of L. elliptica shells. Further, we analyze different morphological traits and their association with the metabolism of a population of L. elliptica from King George Island, Western Antarctic Peninsula. The summer metabolic rates and the hepatosomatic index values indicate good health conditions of this clam’s population. Shell periostracum chemistry is quite similar to bivalves from temperate regions, but the relative amount of protein increased ca. five-fold in shells of L. elliptica. The microhardness is approximately 32% lower than in bivalves from temperate regions. Our characterization of the L. elliptica shells suggests that periostracum chemistry could be specially fitted to avoid shell carbon exposure to dissolution (e.g., in corrosive acidified seawater). In contrast, the reduction in shell hardness may result from prioritizing behavioral (burial) and shell repairing strategies to confront biological (predators) and physical disturbances (e.g., ice scouring). Similar studies in other Antarctic mollusks will help understand the role of shell structure and function in confronting projected climate changes in the Antarctic ocean.

The influences of quality attributes and socio-demographics on Chinese consumers' general and online consumptions of Canadian, US and Australian lobsters

PurposeThis study explores the influence of quality attributes and socio-demographics on Chinese consumers' general and online consumption of three origin-specific lobsters: Canadian, United States and Australian.Design/methodology/approachA web-based survey was administrated to 981 consumers from two cities in China: Shanghai and Qingdao. Descriptive analysis and binary logistic regression were used in the data analysis.FindingsChinese consumers were more willing to pay for the lobster quality attributes vitality, meat content, texture, size and safety. Their general and online consumption of three origin-specific lobsters is significantly linked to the following quality attributes and socio-demographics: meat content, size, shell hardness, texture, safety, nutrition, age, income, education, occupation, residential place and marital status.Originality/valueThis is the first study to explore the influence of quality attributes and socio-demographics on consumers' online consumption of luxury seafood.

A chromosome-level genome of the mud crab (Scylla paramamosain estampador) provides insights into the evolution of chemical and light perception in this crustacean.

Mud crabs, found throughout the Indo-Pacific region, are coastal species that are important fisheries resources in many tropical and subtropical Asian countries. Here, we present a chromosome-level genome assembly of a mud crab (Scylla paramamosain). The genome is 1.55Gb (contig N50 191kb) in length and encodes 17,821 proteins. The heterozygosity of the assembled genome was estimated to be 0.47%. Effective population size analysis suggested that an initial large population size of this species was maintained until 200 thousand years ago. The contraction of cuticle protein and opsin genes compared with Litopenaeus vannamei is assumed to be correlated with shell hardness and light perception ability, respectively. Furthermore, the analysis of three chemoreceptor gene families, the odorant receptor (OR), gustatory receptor (GR) and ionotropic receptor (IR) families, suggested that the mud crab has no OR genes and shows a contraction of GR genes and expansion of IR genes. The numbers of the three gene families were similar to those in three other decapods but different from those in two nondecapods and insects. In addition, IRs were more diversified in decapods than in nondecapod crustaceans, and most of the expanded IRs in the mud crab genome were clustered with the antennal IR clades. These findings suggested that IRs might exhibit more diverse functions in decapods than in nondecapods, which may compensate for the smaller number of GR genes. Decoding the S. paramamosain genome not only provides insight into the genetic changes underpinning ecological traits but also provides valuable information for improving the breeding and aquaculture of this species.

Morphological and pomological characterizations of almond (Prunus amygdalus L.) genotypes to choose the late-blooming superiors

The injuries caused by spring frosts are one of the main factors limiting the production and distribution of almond. Therefore, the present study was performed to select late-blooming almond genotypes that have high quantity and quality of kernel among the seedling originated populations. The genotypes studied showed significant diversity based on the characters measured (ANOVA, P < 0.01). Among all the genotypes studied, the range of nut weight, kernel weight, and kernel percentage was from 1.69–6.09 g, 0.50–1.38 g, and 12.80–45.69%, respectively. After clustering the genotypes based on the full-blooming data, 78 late-blooming genotypes were recognized and reanalyzed based on the fruit-related characters to select the superior ones. In the late-blooming genotypes, kernel taste was sweet in 17 and very sweet in two genotypes. Among those genotypes, the range of nut weight, kernel weight, and kernel percentage was from 1.69–6.09 g, 0.55–1.10 g, and 12.80–45.69%, respectively. The multiple regression analysis (MRA) showed that kernel percentage was found to be associated with shell thickness, kernel length, nut weight, kernel weight, and double kernel percentage. Finally, among the late-blooming genotypes, 21 genotypes were promising according to the ideal values of commercial characters of almonds, including, yield, nut weight, shell hardness, kernel weight, kernel percentage, and kernel flavor, and can be cultivated in the orchards.

In Litopenaeus vannamei, the cuticular chitin-binding proteins LvDD9A and LvDD9B retard AHPND pathogenesis but facilitate WSSV infection

Acute hepatopancreatic necrosis disease (AHPND) is a serious bacterial disease caused by V. parahaemolyticus strains which contain a virulent plasmid that encodes a binary pore-forming Pir toxin. Typically, these AHPND-causing bacteria first colonize in the shrimp stomach and then later cross to the hepatopancreas. To do this, they must pass through structural barriers which include the pliant cuticular lining of the stomach lumen. A previous transcriptomic study of shrimp challenged with the virulent 5HP strain of V. parahaemolyticus found significant upregulation of a contig associated with the cuticular proteins LvDD9A and LvDD9B. Here, we confirmed that the mRNA levels of these two genes were significantly upregulated not only in 5HP-infected shrimp, but also in the stomach of shrimp challenged with the white spot syndrome virus (WSSV). Using dsRNA-mediated gene silencing, we found that AHPND-causing bacteria migrated to the hepatopancreas within 3 h of AHPND infection in LvDD9A/B-silenced shrimp. Shrimp shell hardness of LvDD9A/B-silenced shrimp was also significantly decreased. Conversely, we found that silencing of LvDD9A/B significantly inhibited both WSSV gene expression and genome replication. Taken together, our data suggests that LvDD9A and LvDD9B are involved in both AHPND and WSSV infection. However, in AHPND, these cuticular proteins help to prevent bacterial migration from the stomach to the hepatopancreas, whereas in WSSV infection, they facilitate viral gene expression and genome replication.