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The blood clam (Tegillarca granosa) is an economically important marine shellfish in the southeast coastal area of China. In T. granosa breeding practice, growth-related traits are most important phenotypic selection index. In order to increase the breeding efficiency, we used a previously published genetic linkage map of T. granosa to map quantitative trait loci (QTL) for growth-related traits in a single full sibling F1 family. Eight growth-related traits including shell length (SL), shell height (SH), shell width (SW), shell weight (Swi), shell umbo width (SUW), as well as outer ligament length (OLL), meat weight (MW) and total weight (TW) of T. granosa were measured for QTL mapping. The estimated phenotypic correlations between any 2 of the 8 growth-related traits were significant (P < 0.001). Twenty-nine QTL were identified for growth-related traits, including 13 QTL with the phenotypic variance of 4.20-15.63% in the female map and 16 QTL of 3.99%-14.58% in the male map. Thirteen amplification fragment length polymorphism (AFLP) markers were validated to closely link to seven QTL except the shell height. This is the first report of QTL mapping on growth-related traits in T. granosa. These QTL and their tightly linked markers present the initial step towards the goal of marker-assisted selection in T. granosa. [ABSTRACT FROM AUTHOR]

Meretrix meretrix is one of the economical shellfish that has been exploited in Kendari Bay, Indonesia. Several studies have been done, but its growth pattern and condition index are not fully known. This study aims to determine its growth pattern and condition index at the Kambu River estuary, Kendari Bay. This research was conducted for 6 months from August 2021 to January 2022. Clams were collected using a rake, cleaned, and brought to the laboratory to be measured for length and weight using calipers and scales with an accuracy of 0.1 mm and 0.01g, respectively. Furthermore, the clam meat was dried using an oven and weighed. Data on growth and condition index were analyzed using simple regression and the Mann-Whitney test, respectively. The results showed that the growth of M. meretrix was in negative allometric conditions, with b values in males and females in the range of 2.20-3.00 and 1.86-2.73, respectively. The condition index of male and female clam ranged from 1.86-2.62 and 1.66-2.41, respectively, and differed significantly by month. The results of the Mann-Whitney test on clam showed that there was no significant difference between August-November and December-January. In conclusion, male and female clam had relatively different patterns based on the observation period, while the condition index was in the skinny and medium category. [ABSTRACT FROM AUTHOR]

The individual linear growth of 90 specimens of the freshwater pearl mussel Margaritifera margaritifera was studied by measuring the successive annual rings on the surface of the shell. It was found that the growth of each mollusk can be described using a united equation, a particular case of which is the Bertalanffy equation with an average growth retardation coefficient a = 0.048 year–1 and the coefficient of the initial conditions d = 5.3 mm/year. It was noted that the growth of mollusks is accompanied by three regular biorhythms with periods of 13.4, 6.8, and 4.0 years, with the first two biorhythms fading, the latter having a constant amplitude. It was found that a decrease in the amplitude of fading biorhythms can be described by a power equation with the same coefficients. Questions related to the nature of the biorhythms identified are discussed. [ABSTRACT FROM AUTHOR]

Triploid organisms, in particular oysters, are widely used in marine aquaculture. However, the advantage of triploid oysters compared to diploids has not been proven in all cases. Comparative morphological analysis of Pacific oysters Crassostrea gigas of different ploidy levels allows evaluating the benefits of raising triploids in the Black Sea. First, the morphological characteristics of diploid and triploid Pacific oysters C. gigas farmed in the Black Sea were studied. Allometric ratios of weight (W, g) and shell height (H, mm) of oysters were obtained, which are described by the equations W2n = 4 x 10-4 x H2n 2.56, R² = 0.86 and W3n = 9 x 10-5 x H3n 2.90, R² = 0.91. Triploids showed positive allometry and had more biomass at smaller shell height than diploid oysters. A clear linear relationship of the height and length of oyster shells was established. Significant differences in linear parameters between 2n and 3n C. gigas farmed in Donuzlav Liman are not seen. Based on these results, it is assumed that the advantage of the growth of 3n mollusks is less evident in farms located at high latitudes. The environmental factors and farm technology have probably affected the growth of oysters to a greater degree than their ploidy. [ABSTRACT FROM AUTHOR]

The pearl mollusk Pteria penguin is popular for the production of half-pearls (mabe or cultured blister pearls). Research was carried out on two shell size classes implanted with half-pearl nuclei: the standard 140–145 mm size class (n = 200) was the control, and the smaller 130–135 mm size class (n = 200) was the test group. The mollusks were hung on strings at a sea depth of 2 m for up to 10 months. Implant rejection rates for the two mollusk groups were not significantly different, but the small mollusks had much lower mortality and grew faster. Nacre growth was not significantly different. Digital spectral analysis showed that the three red-green-blue (RGB) colors of the cultured half-pearls followed independent sinusoidal seasonal patterns with time periods of about 10 ± 0.3 months. The amplitude of variation in the RGB colors of the cultured half-pearls were all larger in the small pearl mollusks. [ABSTRACT FROM AUTHOR]

Individual linear growth in 26 specimens of Anodonta beringiana is studied by measuring the successive annual rings on the surface of the shells. It is shown that the growth of mollusks is well described by the von Bertalanffy growth equation. The coefficients of this equation do not significantly differ between individuals, averaging k = 0.062 ± 0.011 year–1 and L∞ = 155.8 ± 19.5 mm. Species lifespan, calculated as a product of the growth constant k and the maximum longevity of mussels in the population, is 1.7. This value is close to the average species lifespan of other bivalve species. [ABSTRACT FROM AUTHOR]

Abstract One of the main challenges for spiny lobster aquaculture is the successful development of formulated feeds that are attractive, readily consumed by lobsters and promote optimal growth and survival. In a 54-day growth trial, we investigated the performance of four moist formulated feeds containing A) non-homogenised flesh ingredients; B) fish meal only; C) 10% krill meal; or D) homogenised flesh ingredients; and a reference diet of shucked blue mussel (Mytilus galloprovincialis) flesh, on growth, nutritional condition and feeding behaviour of juvenile tropical spiny lobster (Panulirus ornatus) reared either communally or individually. Growth and survival achieved by lobsters fed mussel were significantly higher than all other treatments. However, lobsters fed the formulated feed containing 10% krill meal (treatment C) and reared communally had a significantly higher growth, survival and feeding performance when compared to the formulated feeds with inclusion of non-homogenised and homogenised flesh ingredients (treatments A and D). The highest levels of feed interaction and pellet consumption among the formulated feeds were also recorded for treatment C. We demonstrated that the inclusion of krill meal in formulated feeds provides a benefit when compared to the inclusion of the flesh ingredients. Flesh ingredient format (homogenised or non-homogenised) had no effect on growth performance of lobsters, suggesting that the process of homogenisation of flesh ingredients does not provide any benefit in promoting feed consumption. Furthermore, time-series photography analysis trials showed that all the formulated feeds only promoted a feeding response within the first 2–3 h post-feeding, whereas mussel retained its attractiveness throughout the feeding period. These results suggest that the prolonged attractiveness remains an impediment for formulated feed performance in lobster culture. The present study also showed that growth performance and feeding response were higher in lobsters reared communally than individually. As observed in other spiny lobster species, it is likely that social interactions in communal housing may have provided cues that stimulated feeding responses and promoted higher growth rates. Highlights • This study provided essential information for the inclusion of krill meal and flesh ingredients in feeds for juvenile lobster. • Time-series photography analysis was used to better understand the feeding behaviour of early juvenile tropical lobster. • This study reports the first finding on the growth performance of P. ornatus juveniles that were hatchery reared from eggs. [ABSTRACT FROM AUTHOR]

Abstract Oysters are hyper-accumulators of copper (Cu) and zinc (Zn) and are a good food source for trace element supplements. However, increasing heavy metal pollution in estuaries and coastal areas has posed a critical threat to oysters and thus led to food safety issues. Here, we assessed if it is possible to obtain oyster varieties with differential metal-accumulated properties through genetic improvement. The narrow-sense heritabilities of Cu and Zn accumulation capabilities and growth traits in Fujian oyster (Crassostrea angulata) were estimated to determine the degree to which Cu and Zn accumulation is under genetic control. In addition, we investigated the trade-offs between Cu/Zn accumulation and some farming performances, including growth-related traits, and the contents of glycogen and eight free amino acids. Moderate estimates were observed for narrow-sense heritability of Cu (0.189 ± 0.061) and Zn (0.373 ± 0.091) accumulation capability, while growth-related traits showed moderate-high heritability (0.168 ± 0.059–0.595 ± 0.116). High-level genetic (0.802 ± 0.080) and phenotypic (0.853 ± 0.012) correlations were detected between Cu and Zn accumulation capability, while correlations between metal accumulation and growth traits were low (−0.023 ± 0.042–0.491 ± 0.200). Moreover, Cu and Zn accumulation in Fujian oyster exhibited no significant influence on the quality traits measured, except for Taurine (Tau). Tau contents in high Cu/Zn accumulated oysters were significantly higher than in low-accumulated oysters, suggesting an important role of Tau in Cu/Zn accumulation. Our results provide important information to guide effective selective breeding of Fujian oysters with specific Cu/Zn accumulation capabilities. Highlights • Narrow-sense heritabilities, phenotypic and genetic correlations of Cu and Zn accumulation capabilities in Fujian oyster were estimated. • Correlations between Cu/Zn accumulation and growth-related traits were calculated. • Relationships between Cu/Zn accumulation and traits including the contents of glycogen and flavor amino acids were assessed. • This study contributes to selective breeding programs for oysters with specific Cu and Zn accumulation capabilities. [ABSTRACT FROM AUTHOR]

Abstract Around 34 years ago, the first reports on the performance of triploid oysters were published. Since then, triploid oysters have offered many benefits to the oyster industry, such as faster growth, improved meat quality, partial sterility, and increased survival due to disease resistance. However, the extent of a triploid growth advantage, in particular, can vary across studies, measurement parameters, environmental conditions and husbandry practices. To quantitatively compare diploid and triploid oyster growth rates, a meta-analysis was performed with 29 published studies using triploid oysters produced by chemical induction or by crossing diploid and tetraploid oysters (i.e., "mated triploids"). The difference in growth rate between ploidy was evaluated using natural log transformed response ratios (ln[3n/2n]) in a random-effects model weighted by sample size. The positive response ratios in 126 of the 148 independent experiments showed a significant growth advantage of the triploid over the diploid. On average, mated triploids grew 20% faster than diploids in shell height and 49% faster in whole wet weight. While chemically induced triploids had marginally less growth advantage than mated triploids, growing on average 8% faster than diploids in shell height and 31% faster in whole wet weight. Response ratios for experiments using mated triploids and measuring whole wet weight was significantly affected by species and length of study, while response ratios for experiments using chemically induced triploids and measuring whole wet weight was significantly affected by initial size at deployment. Conversely, response ratios for experiments using mated triploids or chemically induced triploids and measuring shell height were not affected by any tested moderator. The lack of a triploid growth advantage in 15% of the experiments (22/148) could have been influenced by a variety of factors including intraspecific variation, differences in sampling, husbandry practices, and environmental conditions. Highlights • Response ratios from 148 experiments indicated a significant triploid advantage in whole wet weight and shell height growth. • Species and length of experiment signifcantly affected whole wet weight growth in experiments using "mated" triploids. • Initial size significantly affected whole wet weight growth in experiments using chemically induced triploids. • No triploid growth advantage in 15% of the experiments stresses the importance of physical and environmental factors.. [ABSTRACT FROM AUTHOR]

Abstract The great scallop, Pecten maximus , presents a strong variability of growth and reproductive patterns along its spatial distribution range. Such differences in life history traits result from complex interactions between organisms and environmental conditions that can be apprehended through the study of energy dynamics. As the determination of accurate food proxy can be a limitation for modeling bioenergetic, recent work by Lavaud et al. (accepted, this issue) , based on the DEB theory, provided a new approach consisting of using temperature and growth time series to reconstruct the required assimilated energy to support observed growth. In this study we present an application of this method to growth trajectories of the great scallop P. maximus used to elucidate: (1) life history traits patterns and (2) the choice of food availability proxies. The inverted DEB model was used to reconstruct the functional response (f) for different age classes of P. maximus in 10 locations of its spatial distribution range. We especially explored the patterns of reconstructed f along latitudinal and bathymetric gradients. Average reconstructed f as well as its maximum value were found to increase with latitude. The variability of f , although increasing, did not show a significant relationship with the geographical position. Along the bathymetric gradient strong positive relationships were found between the mean f or its variability and depth. Ontogeny had low effect on the reconstructed f. Furthermore, as the inverted DEB model allows the reconstruction of physiological variables and energy fluxes, we explored the potential differences in reserve and maintenance fluxes dynamics from great scallops living in these contrasting environments. For one of the study sites, comparisons of f with field measurements of 11 food indicators (chlorophyll- a from the pelagic/benthic domains, phytoplankton cell counts, etc.) highlighted the complexity of the functional response and the diet of P. maximus. Pelagic or benthic phytoplankton biovolume, diatoms and dinoflagellates counts and chlorophyll-a were found to be the major contributors to the variability of f. Results suggest that although assimilation is best described by a combination of indicators, chlorophyll- a remains a good enough indicator of food availability for great scallops and bivalves in general. Highlights • We reconstructed food assimilation from growth in P. maximus using inverted an DEB model. • Ten locations from France to Norway and along a bathymetric gradient were studied. • Results showed an increase of mean functional response and its variations with latitude. • Stronger positive relationships were found between reconstructed f and depth. • Functional response was compared to various food indicators to identify food sources. [ABSTRACT FROM AUTHOR]

Despite recent improvements in treatment, ovarian cancer is still the leading cause of death from gynaecological malignancies. Today, marine mollusks are considered as natural source of new biologically and pharmacologically active compounds by scientists and the pharmaceutical industries. The aim of this study is to investigate the selective apoptotic effects of Turbo coronatus crude extract fractions on human epithelial ovarian cancer (EOC) cells and mitochondria. The cells and mitochondria were isolated from cancerous and non-cancerous ovarian tissues and exposed to IC50 concentration of F1 fraction for evaluation of mitochondrial and cellular parameters. Our results showed that F1 fraction of T. coronatus crude extract significantly induced toxic effects only in the cancerous ovarian mitochondria, including increased reactive oxygen species (ROS) formation, mitochondrial membrane depolarization, mitochondrial swelling, and cytochrome c release. Flow-cytometry analysis demonstrated that F1 fraction of T. coronatus progressively induced apoptosis and necrosis only on EOC but not non-cancerous cells. We eventuallyconcluded that F1 fraction of T. coronatus crude extract selectively induces apoptosis in EOC through a ROS- mediated pathway. [ABSTRACT FROM AUTHOR]

Background: The Pacific abalone, Haliotis discus hannai, is the most important cultivated abalone in China. Improving abalone muscle growth and increasing the rate of growth are important genetic improvement programs in this industry. MicroRNAs are important small noncoding RNA molecules that regulate post-transcription gene expression. However, no miRNAs have been reported to regulate muscle growth in H. discus hannai. Results: we profiled six small RNA libraries for three large abalone individuals (L_HD group) and three small individuals (S_HD group) using RNA sequencing technology. A total of 205 miRNAs, including 200 novel and 5 known miRNAs, were identified. In the L_HD group, 3 miRNAs were up-regulated and 7 were down-regulated compared to the S_HD specimens. Bioinformatics analysis of miRNA target genes revealed that miRNAs participated in the regulation of cellular metabolic processes, the regulation of biological processes, the Wnt signaling pathway, ECM-receptor interaction, and the MAPK signaling pathway, which are associated with regulating growth. Bone morphogenetic protein 7 (BMP7) was verified as a target gene of hdh-miR-1984 by a luciferase reporter assay and we examined the expression pattern in different developmental stages. Conclusion: This is the first study to demonstrate that miRNAs are related to the muscle growth of H. discus hannai. This information could be used to study the mechanisms of abalone muscle growth. These DE-miRNAs may be useful as molecular markers for functional genomics and breeding research in abalone and closely related species. [ABSTRACT FROM AUTHOR]

Shell morphometrics of the invasive mussel Mytilus galloprovincialis were compared at five sites and growth rate at four sites (in four seasons) in the Knysna estuarine embayment. Mussels from two sites (The Heads, Leisure Isle) where wave action was present had shells significantly lower for any length when compared with other more sheltered sites. There was no significant difference in shell width of mussels for any given length among sites. Mussels from The Heads had thicker shells than other sites, and those from Leisure Isle thicker shells than three other embayment sites where shells did not differ in thickness. Growth rate of mussels at two embayment sites (Thesen's Wharf and Thesen Islands Marina) was greatest in autumn and summer whereas at The Heads and Leisure Isle there was little seasonal difference in growth rate. Growth rate of mussels at Thesen's Wharf and Thesen Islands Marina was mainly greater in all seasons when compared with mussels at The Heads and Leisure Isle. The more rapid growth rate of mussels at the sheltered embayment sites might in part explain why M. galloprovincialis now dominates the mid- to lower intertidal on hard substrata in this region of the Knysna estuary. [ABSTRACT FROM AUTHOR]

The study included a descriptive study of the external appearance of the Melanopsis buccinoidea shell, which included the length, width, number of shell spire as well as size of the opening of shell, as well as its weights (wet - dry - ash and ash free dry weights). The knowledge of the egg-laying mechanism provides us with very important information for subsequent research into the life cycle of this species of molluscs in the region. [ABSTRACT FROM AUTHOR]

Determining the magnitude and causes of intrinsic variability is a main issue in the analysis of bivalve growth. Inter-individual variability in bivalve growth has been attributed to differences in the physiological performance. This hypothesis has been commonly tested comparing the physiological rates of fast and slow growers after size differentiation has occurred. This experimental design may detect a link between growth and physiological performance, but we cannot interpret the posterior physiological performance as a driver for the prior growth variability. Considering these limitations, this work introduces a new methodological framework for the analysis of bivalve growth variability. We have conducted sequential measurements of size and physiological performance (feeding, digestion and metabolic rates) in even-sized mussels growing under homogeneous environmental conditions. This experimental design allows us to distinguish between changes over time within individuals, i.e. growth and trends in the physiological rates, from differences between individuals with respect to a baseline level. In addition, Functional Data Analysis provides powerful tools to summarize all the information obtained in the exhaustive sampling scheme and to test whether differences in the physiological performance enhance growth dispersion. Our results report an increasing dispersion in both size and physiological performance over time. Although mussels grew during the experiment, it is difficult to detect any increasing or decreasing temporal pattern in their feeding, digestion and metabolic rates due to the large inter-individual variability. Comparison between the growth and physiological patterns of mussels with final size above (fast growers) and below (slow growers) the median found that fast growers had larger feeding and digestion rates and lower metabolic expenditures during the experimental culture than mussels with slow growth, which agrees with the hypothesis of a physiological basis for bivalve growth variability. [ABSTRACT FROM AUTHOR]

Ageing is defined as the progressive decline in tissue and organ functions over time. This study aims to evaluate the ageing effect on cultured pearl quality phenotypes (including size and quality traits) in the graft-recipient animal model: Pinctada margaritifera. For this, eight uniform grafting experiments were designed using two hatchery-produced pearl oyster families as donors, which were followed through time, between 7 and 30 months in age. For each age category, 20 donors were studied for each culture site giving a total of 2400 grafted oysters. Several phenotypic measurements were made: 1) donor family growth performance from shell size records, 2) pearl size and corresponding quality traits, and 3) expression of some genes related to biomineralization processes on both the mantle graft and on pearl sac tissues. Results showed that: 1) donor age has an impact on pearl size, with grafts coming from the youngest donors yielding the biggest pearls; and 2) grafts from donors between 12 and 18 months in age produced pearls of the highest quality (grade and surface quality), a result supported by an analysis where the level of expression for a panel of genes associated with biomineralization was greatest in donors within the 12 to 18 months age group. These results indicate that donors aged between 12 and 18 months have high potential for biomineralisation and nacre deposition, and likely produce larger and higher quality cultured pearls than older donors. [ABSTRACT FROM AUTHOR]

The Atlantic surfclam (Spisula solidissima) is a commercially important species in North American waters, undergoing biological and ecological shifts. These are attributed, in part, to environmental modifications in its habitat and driven by climate change. Investigation of shell growth patterns, trace elements, and isotopic compositions require an examination of growth lines and increments preserved in biogenic carbonates. However, growth pattern analysis of S. solidissima is challenging due to multiple disturbance lines caused by environmental stress, erosion in umbonal shell regions, and constraints related to sample size and preparation techniques. The present study proposes an alternative method for describing chronology. First, we analyzed growth patterns using growth lines within the shell and hinge. To validate the assumption of annual periodicity of growth line formation, we analyzed the oxygen isotope composition of the outer shell layer of two specimens (46°54'20"N; 56°18'58"W). Maximum δ18Oshell values occurred at the exact same location as internal growth lines in both specimens, confirming that they are formed annually and that growth ceases during winter. Next, we used growth increment width data to build a standardized growth index (SGI) time-series (25-year chronology) for each of the three parts of the shell. Highly significant correlations were found between the three SGI chronologies (p < 0.001; 0.55 < τ < 0.68) of all specimens. Thus, ligament growth lines provide a new method of determining ontogenetic age and growth rate in S. solidissima. In a biogeographic approach, the shell growth performance of S. solidissima in Saint-Pierre and Miquelon was compared to those in other populations along its distribution range in order to place this population in a temporal and regional context. [ABSTRACT FROM AUTHOR]

Abstract: Worldwide, there are approximately 100 Haliotis species, more commonly known as abalone or ‘Paua’ in New Zealand, ‘Venus's‐ears’ in Greece, ‘Awabi’ in Japan, ‘Perlemoen’ in South Africa and ‘Ormers’ in Europe. Regardless of what they are called in any part of the world, a high monetary value is coupled to this animal, because it is largely considered a seafood delicacy. Subsequently, a great deal of research primarily focused on improving the health and growth rates of abalone were carried out to maximise productivity of the commercial farming efforts in various countries. In this review, we comprehensively describe the most recent available scientific literature on abalone biology, and those aspects related to the growth of this organism; more specifically, those factors related to the uptake and breakdown of metabolic products which ensures long‐term growth. We subsequently discuss this in terms of basic animal design, farming outcomes, feeding, cellular growth mechanisms and the unique metabolic processes that exist in these species. Using this information and the knowledge of the metabolic processes in other organisms, we additionally make a number of new hypotheses regarding how these metabolic processes may function in terms of abalone growth. Based on the information presented in this review, we also identify major research opportunities and gaps in the existing knowledge of abalone metabolism, which when elucidated may not only serve the purpose of better understanding these organisms growth but also could potentially lead to increased productivity of the abalone commercial farming sector. [ABSTRACT FROM AUTHOR]

Age estimation methods based on hard structures require a process of validation to confirm the periodical pattern of growth marks. Among such processes, one of the most used is the marginal increment ratio (MIR), which was stated to follow a sinusoidal cycle in a population. Despite its utility, in most cases, its implementation has lacked robust statistical analysis. Accordingly, we propose a modeling approach for the temporal periodicity of growth increments based on single and second order harmonic functions. For illustrative purposes, the MIR periodicities for two geoduck species (Panopea generosa and Panopea globosa) were modeled to identify the periodical pattern of growth increments in the shell. This model identified an annual periodicity for both species but described different temporal patterns. The proposed procedure can be broadly used to objectively define the timing of the peak, the degree of symmetry, and therefore, the synchrony of band deposition of different species on the basis of MIR data. [ABSTRACT FROM AUTHOR]

The transfer of seaweeds from subtidal bottoms to nearby intertidal rocky shores is a common but often overlooked phenomenon. Freshly detached seaweeds often represent critical trophic subsidies for herbivores living in upper-shore rocky intertidal areas, such as the marine snail Diloma nigerrima. This species relies on three species of seaweeds for food and displays feeding strategies to deal with a resource that is scarce and at times unpredictable. This study focused on the nutritional quality of freshly detached algae (Durvillaea antarctica, Lessonia spicata and Lessonia trabeculata) and measured Diloma nigerrima’s algal consumption rates in trials with and without choice. Absorption efficiency and growth of individual snails fed on each alga were also measured. Durvillaea antarctica had the highest nutritional quality and was the most consumed algae in both single and multiple-choice trials. Absorption efficiency was also highest for D. antarctica but growth rates of snails fed with this species were similar to those fed with the other algae. Combined, these results suggest that D. nigerrima has the ability to discriminate among seaweeds based on their nutritional quality. A potential increase in oxygen uptake when D. nigerrima is consuming the preferred food item is also proposed as a plausible hypothesis to explain the mismatch between snails’ preference and growth rate. These results aim to guide further studies on trophic subsidies and their role in coastal systems. [ABSTRACT FROM AUTHOR]

Abstract: IGF‐1R plays a critical role in many physiological activities, such as development, growth, metabolism, and reproduction. Identification of genetic markers in the IGF‐1R gene significantly associated with important growth traits of Odontobutis potamophila may accelerate genetic improvement. In this study, we characterized the cDNA sequence of the IGF‐1R gene of O. potamophila, and our data revealed that IGF‐1R contained an open reading frame of 1650 bp, encoding a polypeptide of 549 amino acids (aa). Quantitative real‐time polymerase chain reaction demonstrated that IGF‐1R was ubiquitously expressed in all tested tissues, and the most predominant expression of IGF‐1R was detected in gonad. Moreover, IGF‐1R was expressed at different developmental stages from embryo to larva, and its highest expression level was found at the morula stage. In addition, we identified three single nucleotide polymorphisms (SNPs; 1777T>C, 1704G>A, and 1208G>A) within IGF‐1R locus and found that one SNP (1208G>A) was significantly associated with important growth traits of O. potamophila. Results showed that the overall length, body length, trunk width, caudal peduncle length, body weight, and body width in fish with AG genotype were significantly greater compared with those with GG genotype (P < 0.05). However, the other two SNPs (1777T>C and 1704G>A) did not show significant associations with any growth traits. Therefore, SNPs within the IGF‐1R locus could be used as a selection criterion to improve growth traits of O. potamophila. [ABSTRACT FROM AUTHOR]

The early post-parasitic phase is considered to be the most vulnerable life stage of the endangered freshwater pearl mussel (Margaritifera margaritifera), yet little is known about the spatial variability in juvenile performance at a river scale. The main aim of this study was to determine within-river variation in habitat suitability for juvenile M. margaritifera. The growth and survival rates of juveniles (one and two year old) were measured in the Vltava River (Czech Republic) in relation to several physical and chemical variables using a total of 166 bioindication units (individual mesh cages and sandy boxes) during two thermally different vegetation seasons. Three spatial scales were studied: a longitudinal river profile, bottom habitat types, and hyporheic microhabitats. Both the survival rate and growth of the exposed juveniles varied considerably within the studied river. The effect of the longitudinal river profile and the roles of temperature, oxygenation within microhabitats, episodic pollution, and exposure method were demonstrated. This study represents the first example of a hierarchized approach to the assessment of a riverine mussel biotope with the use of bioindication methods. The results demonstrate the importance of the scale and bioindication method used in understanding the suitability of a river environment to juvenile freshwater mussels. [ABSTRACT FROM AUTHOR]

Determining how, when, and why energy allocation occurs based on different life history traits, provides core knowledge for understanding evolution, ecology, and conservation of populations. We assumed that, in seasonal environments, Anodontites trapesialis, a common freshwater mussel in the Pantanal wetland, has to time its maturation, its larvae incubation time, and adjusts its breeding strategy seasonally. From histological analyses of gametes, larval count, and marginal increment of the shell rings, we present information about phenology and growth strategies to investigate the influence of environment and reproductive period on growth. We determined for the first time, asymptotic maximum size and longevity for this mussel. This species is a functional hermaphrodite, with maturation and spawning starting at the end of the flood period, when the water begins to recede and fishes return to the main river channel. The larvae, lasidium in this case, disperse on host fishes at this time. As we predicted, the flood pulse is the main regulatory factor to the growth patterns and reproductive period establishment. The species’ life history traits are discussed in the context of life history theory as adaptive responses to the dynamic balance imposed by the seasonality of the Pantanal. [ABSTRACT FROM AUTHOR]

Here we analyse in detail, for the first time, the growth pattern of the endangered freshwater mussel Margaritifera auricularia in the Ebro basin, a life history trait essential for conservation purposes. We combined information on size and age from captive bred juveniles, together with growth annuli from living preadults studied in the field, and empty shells of preadult and adult individuals. We compared the fit of six types of (asymptotic and sigmoid) non-linear growth models and, in terms of residual errors and AIC values, the sigmoid ones were superior, being the Generalized von Bertalanffy and Richards models the best fitted ones. After an initial exponential growth phase in juveniles, growth rate starts to decelerate at an inflection point corresponding to an age of seven years. At an age of about 30 years, the growth rate markedly declines and attains an asymptote at c. 150 mm shell length. Global growth rate is relatively low but comparable to other members of the family, and the maximum age estimated from ring counts was 68 years. We demonstrate that the use of sigmoid models provides more accurate estimation of growth patterns in freshwater mussels, as previously observed for other bivalves. [ABSTRACT FROM AUTHOR]

The bivalve family Vesicomyidae comprises two subfamilies: Pliocardiinae and Vesicomyinae. The Pliocardiinae include conspicuous mostly large- and medium-sized clams, which live in symbiosis with chemoautotrophic bacteria and often dominate chemosynthetic communities in the deep sea. The Vesicomyinae comprise poorly-studied tiny bivalves, which at first sight differ considerably from their better known, large-sized relatives. Vesicomyines have a worldwide distribution from mid-slope to hadal depths and reach abundances of thousands of specimens in one trawl catch in deep-sea trenches. The genus Vesicomya is morphologically very similar to the genus Kelliella, the type genus of family Kelliellidae. This fact has long caused taxonomic ambiguities and it has been suggested that Vesicomya and Kelliella, as well as their respective nominate families, should be synonymized. In this paper we study the relationship between Vesicomya and Kelliella, for the first time using not only morphological characters but also genetic divergence based on the mitochondrial cytochrome c oxidase subunit I (COI) gene. Our molecular data indicate that the genera Vesicomya and Kelliella are clearly distinct and that Kelliella is distantly related to the Vesicomyidae. Results of morphological analysis support the molecular inferences. We provide further evidence for the relationship of vesicomyines and pliocardiines and propose an evolutionary scenario according to which Vesicomyinae is the less derived group and Pliocardiinae the more derived. We provide the first information on stable carbon and nitrogen isotopic composition of soft tissues of Vesicomya and Kelliella. These data do not suggest involvement of chemosynthetically fixed carbon in the nutrition of either Vesicomya or Kelliella. We revise current usage of these two genera and provide lists of the species of each, with details of their distribution. A new species, Vesicomya alleni, is described on the basis of morphological and molecular characters. [ABSTRACT FROM AUTHOR]

Despite Lissachatina fulica being a pest of agricultural and ornamental plants in the worldwide tropics for more than 100 years, information on its biology is limited. In this study, 360 snails were reared in the laboratory from a colony collected from the wild (non-native) population in Miami-Dade County, Florida, and were monitored for growth (height and mass) and egg production for up to 930 d. Snails averaged 195 d old and 97mm in height when egg laying was initiated. Though the average snail peristome thickness was lower (0.1 mm) before eggs were first laid than after (0.4 mm), peristome thickness was inconsistent in predicting full reproductive maturity. Egg production averaged 4,698 eggs per snail and egg viability averaged 49% in the first 540 d after hatching. Oviposition without mating was shown to be possible, but occurred rarely (3% of snails) and with lower viability rates and smaller clutch sizes. The ability to oviposit without mating and the high reproductive rates found in this study indicate that eradication efforts addressing new infestations must be complete, because even one snail may start another population. [ABSTRACT FROM AUTHOR]

The occurrence and the intensity of specific behavioural defensive reactions were investigated in freshwater snails of the family Physidae, which vigorously shake their shells when attacked by invertebrate predators. Physella acuta and Physa fontinalis were exposed to two species of leeches with different hunting strategies-- the molluscivorous Glossiphonia complanata and the opportunistic predator Erpobdella octoculata. Parameters of reaction were measured and compared between snails and leeches. Significant differences were found in the reactions of both snail species in 10 out of 11 measured parameters. Physa fontinalis reacted more intensively, with a higher number of shell movements triggered by both leech species. The study showed possible recognition by the prey of the predator species, followed by a specific defensive reaction. In general, G. complanata elicited more intensive reactions, especially in treatment with P. fontinalis. [ABSTRACT FROM AUTHOR]

Mitochondrial COI sequence variation was examined in members of the Pyrgulopsis kolobensis complex to clarify further the confused taxonomy of these springsnails, which were treated as a single species prior to a recent study that recognized five morphologically and genetically distinct species for the populations in the Virgin River drainage of southern Utah. Phylogenetic analyses of 44 currently undescribed populations in this complex from the eastern Great Basin and Snake River basin congruently resolved five divergent lineages. One of the lineages contained most of the newly sequenced specimens as well as the haplotypes of three currently recognized regional species. The mean genetic distance within this lineage was slight (0.7%) and consequently we treat it as a single, morphologically variable species for which the name P. pilsbryana has precedence and should be used. Two of the other lineages (both having small geographic ranges) are sometimes sympatric both with each other and with P. pilsbryana (as envisaged herein), but could not be distinguished morphologically and may be divergent haplogroups of P. pilsbryana or undescribed cryptic species. The remaining two lineages are single populations in eastern Nevada and southern Utah that, together with other, previously detected lineages from these areas, will require additional morphological study to determine their taxonomic status. Further molecular sampling, especially of the many populations in Nevada that have not been analysed so far, is also needed to help complete the taxonomic revision of the P. kolobensis complex. [ABSTRACT FROM AUTHOR]

The Ampullariidae (apple snails) are freshwater snails of tropical and subtropical regions. Recent research has concentrated on a few species that are invasive or potential biocontrol agents, but the basic life history traits of most species remain unknown. One such poorly known species is Pomacea americanista, endemic to the Alto Paraná and Iguazú Rivers in southern South America, which may be vulnerable to environmental degradation. We studied the growth, survivorship, maturation and reproductive activity of P. americanista to help evaluate its resilience under different scenarios of environmental change. Fifty snails that hatched in the laboratory from two egg masses collected in San Francisco Stream (Misiones Province, Argentina) were reared under controlled conditions until their natural death. Shell growth was almost linear up to the 20th week of life, subsequently decreasing smoothly. Growth rate, asymptotic sizes, time to reach asymptotic size and age at maturity were greater for females than males. Mortality patterns were similar for both sexes, with no deaths up to 38 weeks and steady mortality thereafter, the maximum longevity being 143 weeks. The fecundity of P. americanista is lower than that of other apple snails under similar conditions. Under laboratory conditions males and females underwent a single extended reproductive period, but under the seasonal climate in their natural habitats their life cycle would probably extend for more than 3 years, with two or more reproductive periods. The low fecundity and the late maturity of P. americanista indicate slow population growth and low resilience relative to invasive apple snails. These traits, combined with a restricted geographical range and an association with hard substrates in swiftly flowing waters, suggest that P. americanista could be vulnerable. [ABSTRACT FROM AUTHOR]

There are 108 species of nematode that are known to have co-evolved with gastropods and use them as definitive, intermediate or paratenic hosts. One nematode (Phasmarhabditis hermaphrodita) is lethal to eight species of snail, but nine species are resistant for unknown reasons. This study investigated whether a previously untested snail species, Arianta arbustorum, was susceptible to P. hermaphrodita. Snails were exposed to 0, 30 and 90 P. hermaphrodita per cm2 applied to the soil surface for 40 days. Survival, feeding inhibition and differences in weight were monitored. It was found that A. arbustorum was resistant to P. hermaphrodita. The nematode did not cause mortality, induce feeding inhibition or affect weight. At the end of the experiment, surviving A. arbustorum had encapsulated and killed the invading nematodes in their shells. Inspection of shells of A. arbustorum collected on sand dunes in the north of Scotland, and in those collected by others in 1966 and 1908, revealed the presence of encapsulated nematodes. Arianta arbustorum can encapsulate and kill invading nematodes under laboratory conditions and in the wild, and the evidence of encapsulation remains for a long time. [ABSTRACT FROM AUTHOR]

Empty mollusc shells provide evidence of the species' presence over various temporal and spatial scales. However, the persistence of the shell can differ depending on the levels of soil pH and soil humidity. Although this is generally known, there are virtually no experimental data on shell decomposition rate and its relation to shell size and site conditions. Here we study disappearance and degradation rates of shells of nine common species covering the variation in shell size and ecological requirements of temperate European land snails. These shells were exposed to decomposition during a 3-year field experiment in six forest types, representing a gradient of soil pH and humidity. Rates of disappearance and (in larger species) of degradation were estimated by removing the exposed shells and measuring their condition after 6, 12, 24 and 36 months. The disappearance rate was modelled by generalized linear models in relation to species and forest type. The data showed an increase in shell disappearance rate from dry alkaline through to wet acidic forests, but the effect of species size outweighed that of habitat. While shells of large species only started to disappear after 3 years in wet acidic sites, most shells of small species had already disappeared by that time. In contrast, in dry habitats the loss of small shells only started after 3 years. The results clearly support the benefits of using empty shells in mollusc research, especially less damaged shells, which represent the individuals that were alive less than 2 years ago, regardless of shell size and habitat type. However, the marked differences in decomposition rate related to shell size and habitat also highlight the need to take these into account if a studied parameter is confounded with variation in shell size and/or site alkalinity or humidity. [ABSTRACT FROM AUTHOR]

The interest in Arctica islandica growth biology has recently increased due to the widespread use of its shell as a bioarchive. Although temperature and food availability are considered key factors in its growth, their combined influence has not been studied so far under laboratory conditions. We tested the interactive effect of temperature and food availability on the shell and tissue growth of A. islandica juveniles (9–15 mm in height) in a multi-factorial experiment with four food levels (no food, low, medium, and high) and three different temperatures (3, 8, 13 °C). Shell and tissue growth were observed in all treatments, with significant differences occurring only among food levels (2-way ANOVA; P-value < 0.05). Siphon activity (% open siphons), however, was affected by temperature, food, and the interaction between them (2-way ANOVA; P-value < 0.05). Siphon observations, as indication of feeding activities, played a key role to better understand the growth variation between individuals. [ABSTRACT FROM AUTHOR]

A sclerochronological and radiocarbon-based study of life history traits of Stimpson's hard clam ( Mercenaria stimpsoni ), collected alive from Funakoshi Bay, northeast Japan, showed the lifespan of the species to be at least 92 years (determined from annual growth line counts). Three M. stimpsoni specimens exhibited the following synchronous growth pattern, suggestive of environmental control; annual increment width increasing after 1955 to a maximum value between 1970 and 1980, subsequently decreasing gradually until 2000, and thereafter remaining constant or increasing slightly. Variations on annual growth patterns, as well as standardized growth indices chronology, were relatively closely linked to the Atlantic Multidecadal Oscillation (AMO), but less so to Pacific Decadal Oscillation (PDO). Carbonate samples collected from ontogenetically younger shell portions, estimated from growth line counts to have been deposited before 1950, contained no nuclear bomb-test radiocarbon, thereby supporting the accuracy of annual growth line counts (versus overcounting from ventral margin). Together with the synchronous annual increment width patterns, this indicated that age and annual growth rate estimations for M. stimpsoni based on growth line counts were reliable and applicable to high-resolution sclerochronological analyses, which should contribute to a deeper understanding of multi-decadal northwest Pacific climate variability. [ABSTRACT FROM AUTHOR]

The present study reports weight-length (W-L) relationships and discusses the relative growth of the banded murex (Hexaplex trunculus) from intertidal and offshore areas of the Gulf of Gabès (southern Tunisia). Overall, 9634 H. trunculus were sampled (6608 from intertidal and 3026 from offshore), with both populations comprising broad ranges in shell length (intertidal: 13.6-78.5 mm; offshore: 22.9-91.1 mm) and total weight (intertidal: 0.2-63.8 g; offshore: 0.6-92.5 g). In both populations, W-L relationships were highly significant and the morphometric parameters were highly correlated (intertidal: r = 0.967; offshore: r = 0.973). Relative growth was significantly different between populations, with intertidal H. trunculus displaying a negative allometry (b = 2.962) and offshore H. trunculus exhibiting isometric growth (b = 3.013). Factors influencing total weight (soft-body weight and shell weight) and potentially responsible for differences in W-L relationships and relative growth between populations were discussed. In addition, a useful comparative analysis for fisheries biology, assessment and management purposes was performed with analogous information from other populations of H. trunculus from the Mediterranean Sea and the Atlantic Ocean. [ABSTRACT FROM AUTHOR]

This paper presents the resuls of growth rate and condition index analysis of Mytilus galloprovincialis in integrated system and monoculture. The aim of this study was to show if there are differences in growth and condition index of mussels between integrated multi-trophic aquaculture (IMTA) and monoculture farming. The growth rate and condition index were monitored during a 13-month study at three different sites: 1) close to fish cages (NBL), 2) 100 m removed from fish cages (NUD), 3) at a monoculture mussel farm (SVN) around 8 km far away from cages. The most intense growth of mussels was recorded in spring, and the least intense in summer. After 13 months, monitored individuals at all three locations achieved commercial size. The growth rate was very similar at all sites. The condition index showed spatial and temporal differences. Condition index values on site NUD were mostly higher compared to SVN and NBL, which were very similar, exept for the period from October to December when CI was similar on NBL and NUD site and higher in comparation with SVN. CI values on NBL an NUD site during cold period indicate on fact that mussels probably feed on the nutrients from fish farm origins.The highest mortality rate was recorded at the NBL site, probably due to the effects of fouling organisms. [ABSTRACT FROM AUTHOR]

The levels of mineral element Na, Mg, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Mo, Al, As, Ag, Cd, and Tl were quantified in the whole shells of the freshwater bivalveAnodonta woodianaat three different growth stages (i.e. J1 juveniles of 1 month old, J2 juveniles of 3.5 months old, and adults of 36 months old). The concentrations of Na and Al were different between different growth stages (p < 0.05). The highest Na concentrations (2715 ± 86 μg/g dry weight) were found in J2 juveniles. The highest Al concentrations (303.9 ± 5.95 μg/g dry weight) were found in J1 juveniles. Manganese concentrations (517.0 ± 47.98 μg/g dry weight) were significantly higher in J2 juveniles than in J1 juveniles (432.3 ± 9.87 μg/g dry weight) (p < 0.05). Copper concentrations (27.32 ± 0.15 μg/g dry weight) were significantly higher in J1 juveniles than in J2 juveniles (26.21 ± 0.86 μg/g dry weight) and adults (24.74 ± 1.43 μg/g dry weight) (p < 0.05). Burdens of Na, Ca, Mn, Fe, Co, Cu, Mo, Ag, and Tl were positively correlated with the shell length (p < 0.05). These findings can possibly contribute to an understanding of elemental requirements for shell growth and, hence, facilitate improvement of survival and growth rates during artificial mussel culture. [ABSTRACT FROM AUTHOR]

Growth rate is one of the most important traits from the point of view of individual fitness and commercial production in mollusks, but its molecular and physiological basis is poorly known. We have studied differential gene expression related to differences in growth rate in adult individuals of the commercial marine clam Ruditapes decussatus. Gene expression in the gills and the digestive gland was analyzed in 5 fast-growing and five slow-growing animals by means of an oligonucleotide microarray containing 14,003 probes. A total of 356 differentially expressed genes (DEG) were found. We tested the hypothesis that differential expression might be concentrated at the growth control gene core (GCGC), i.e., the set of genes that underlie the molecular mechanisms of genetic control of tissue and organ growth and body size, as demonstrated in model organisms. The GCGC includes the genes coding for enzymes of the insulin/insulin-like growth factor signaling pathway (IIS), enzymes of four additional signaling pathways (Raf/Ras/Mapk, Jnk, TOR, and Hippo), and transcription factors acting at the end of those pathways. Only two out of 97 GCGC genes present in themicroarray showed differential expression, indicating a very little contribution of GCGC genes to growth-related differential gene expression. Forty eight DEGs were shared by both organs, with gene ontology (GO) annotations corresponding to transcription regulation, RNA splicing, sugar metabolism, protein catabolism, immunity, defense against pathogens, and fatty acid biosynthesis. GO termenrichment tests indicated that genes related to growth regulation, development and morphogenesis, extracellular matrix proteins, and proteolysis were overrepresented in the gills. In the digestive gland overrepresented GO terms referred to gene expression control through chromatin rearrangement, RAS-related small GTPases, glucolysis, and energy metabolism. These analyses suggest a relevant role of, among others, some genes related to the IIS, such as the ParaHox gene Xlox, CCAR and the CCN family of secreted proteins, in the regulation of growth in bivalves. [ABSTRACT FROM AUTHOR]

Myostatin (MSTN), also called growth and differentiation factor-8 (GDF-8), is a member of the transforming growth factor-β (TGF-β) superfamily and an inhibitor of muscle differentiation and growth. In this report, we identified and characterized a MSTN gene (CnMSTN) from the scallop Chlamys nobilis . The open reading frame of CnMSTN was 1374 bp in length, encoding 457 amino acids. The structure of CnMSTN included a putative signal peptide, a TGF-β propeptide domain, and a conserved TGF-β domain. Phylogenetic analysis showed that the CnMSTN gene was clustered in the same subgroup with the MSTN gene found in Mollusca. Quantitative real-time PCR showed that the CnMSTN gene was widely expressed in all tissues tested, with the highest expression level observed in the adductor muscle. Six single nucleotide polymorphisms (SNPs) were identified in the promoter region, but no SNP was detected in the exon regions. Association analysis showed that SNP g.-579A/C had significant effects on body mass, soft-tissue mass, and adductor muscle mass. The CC and AC genotypes of g.-579A/C had significantly higher growth trait values than that of genotype AA ( P < 0.05). These results suggest that CnMSTN could be used as a candidate gene for the selective breeding of C. nobilis . [ABSTRACT FROM AUTHOR]

The effect of kelpEcklonia maximainclusion in formulated feeds on abalone growth and gut bacterial communities has not been previously investigated in South Africa. An eight-month on-farm growth trial was conducted with sub-adultHaliotis midae(∼43 mm shell length) fed graded levels of kelp in formulated feeds. Kelp inclusion (0.44–3.54% of pellet dry mass) promoted faster growth (65.7–74.5% total mass gain), with better feed and protein conversions (apparent feed conversion ratio [FCR] 1.4–1.8, apparent protein efficiency ratio [PER] 2.3–2.7), as compared with the non-supplemented feed (52.3% total mass gain, FCR 2.1, PER 1.9;p< 0.001). Abalone-gut bacterial DNA was sequenced using 16S rRNA gene pyrosequencing and the sequences were clustered into operational taxonomic units (OTUs) at a 97% similarity level. A supplementary 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) analysis was employed. The dominant OTUs differed in terms of their relative abundances, with an autochthonousMycoplasmastrain being significantly more abundant (p= 0.03) in the gut of abalone fed a kelp-supplemented feed. The DGGE band patterns displayed higher within-group variability for abalone fed the control diet, suggesting that dietary kelp inclusion promotes gut-bacteria homeostasis. This may contribute to better feed utilisation and growth in abalone fed kelp-supplemented feeds. [ABSTRACT FROM AUTHOR]

Many hybrids of marine molluscs show improved growth in comparison to their pure parental species. Yet, little is known about the physiological mechanisms underlying the better hybrid performance. In this study, movement, oxygen consumption rate ( M ̇ O 2 ), and heart rate were determined in 22 month old cultured abalone Haliotis rubra , H. laevigata and their interspecies hybrid, the latter of which exhibits improved growth rate. Abalone were exposed to an acute temperature increase following acclimation to 16 or 23 °C at high and low oxygen levels (100% or 70% air saturation, respectively). Movement of hybrids and H. laevigata was generally not affected by temperature and oxygen levels, yet H. rubra showed a strong thermal response. Heart rate and M ̇ O 2 /temperature slopes revealed that hybrids were least affected by oxygen levels. Arrhenius break-point temperatures of hybrids and H. laevigata , but not H. rubra , were generally higher when abalone were acclimated to 23 °C in comparison to 16 °C. The hybrid had more stable maximum heart rate and M ̇ O 2 values across acclimation conditions in comparison to H. laevigata and H. rubra . Thus, it appears that hybrids are able to maintain physiological functions over a broader environmental range. This improved tolerance to environmental fluctuations may bolster energy metabolism and improve growth in variable environments such as aquaculture farms. [ABSTRACT FROM AUTHOR]

Hyriopsis cumingii is one of the most important freshwater pearl mussels in China. Recently, this species can produce freshwater nucleated pearls of high quality. Here, we investigated whether nucleated pearl quality is influenced by the growth traits of the host mussel or other factors like cultivation period. We implanted host mussels with a spherical nucleus consisting of a small piece of mantle tissue from donor mussels. After 24 and 36 months of culture, host mussel growth traits including body weight and shell length, height, width and weight were recorded. These factors were then correlated with the quality traits of the pearls they produced, such as nacre thickness, size, weight, lustre and colour. Results indicated pearls obtained at 36 months after seeding were significantly larger in terms of nacre thickness, size and weight compared to those harvested at 24 months. In particular, nacre thickness ( r = 0.33-0.48, P = 0.00), pearl size ( r = 0.39-0.43, P = 0.00) and pearl weight ( r = 0.35-0.47, P = 0.00) were showed to be significantly correlated with host mussels shell length, body weight and shell weight at 24 or 36 months. Larger and heavier host mussels tended to produce bigger pearls. In contrast, host mussels did not affect pearl colour. Cumulatively, our results suggest that longer culturing times and a larger host mussel may help produce better quality nucleated pearl. This information can help guide selective breeding programs designed to improve pearl quality produced by H. cumingii. [ABSTRACT FROM AUTHOR]

The growth and health of cultured blue mussels ( Mytilus edulis ) are affected by environmental conditions. Typically, culture sites are situated in sheltered areas near shore (i.e., < 1 km distance from land, < 20 m depth); however, land runoff, user conflicts and environmental impact in coastal areas are concerns and interest in developing deep water (> 20 m depth) mussel culture has been growing. This study evaluated the effect of culture depth on blue mussels in a cold water coastal environment (Newfoundland, Canada). Culture depth was examined over two years from September 2012 to September 2014; mussels from three shallow water (5 m) and three deep water (15 m) sites were compared for growth and biochemical composition; culture depths were compared for temperature and chlorophyll a . Differences between the two years examined were noted, possibly due to harsh winter conditions in the second year of the experiment. In both years shallow and deep water mussels presented similar condition; in year 2 deep water mussels had a significantly better biochemical profile. Lipid and glycogen analyses showed seasonal variations, but no significant differences between shallow and deep water were noted. Fatty acid profiles showed a significantly higher content of omega-3 s (20:5ω3; EPA) and lower content of bacterial fatty acids in deep water sites in year 2. Everything considered, deep water appeared to provide a more favorable environment for mussel growth than shallow water under harsher weather conditions. [ABSTRACT FROM AUTHOR]

Ivory shell, Babylonia areolata, is one of the commercially important mariculture species in southern China and South-East Asia. The selection programme for growth trait has been conducted since 2010 in two selected lines for three generations, namely the Hainan (H) and Thailand (T) selected lines. Ten polymorphic microsatellite loci were used to monitor changes in their genetic diversity and structure during the selection process. A relatively high level of overall genetic diversity was observed, while the number of microsatellite allele declined slightly in the mass selection lines. Comparative diversity estimates indicated greater genetic diversity in H line than T line. Moreover, a relatively weak but significant genetic differentiation was found in both of the selected generations. In addition, the higher genetic variation observed in H line is most likely caused by artificial selection while selection bias on a growth advantage for the T population. These findings suggest no significant decline of genetic diversity was observed in the presently selected lines and that a potential exists for genetic improvement and development for B. areolata. [ABSTRACT FROM AUTHOR]

A 10-day experiment was performed to examine different mono, binary and ternary dietary combinations on survival and growth of D-shaped and umbone black-lip pearl oyster, Pinctada margaritifera, larvae. The three tropical microalgae species were the flagellate Isochrysis galbana clone T. Iso (CS-177) and diatoms Chaetoceros calcitrans (CS-178) and Chaetoceros muelleri (CS-176) which were fed to D-shaped and umbone larvae at a density of 7000 and 14 000 cells mL−1, respectively. A second experiment was performed to investigate the feasibility of replacing T. Iso with a lipid emulsion for both D-shaped and umbone larvae for 10 and 12 days, respectively. The treatments included only T. Iso, unfed and lipid emulsion to substitute T. Iso at levels of 10% (LIP10), 30% (LIP30) and 100% (LIP100). In the first experiment, results showed that a monospecific diet of T. Iso led to significantly higher ( P < 0.05) survival and growth of D-shaped larvae than all the other treatments. Meanwhile, D-shaped larval survival was significantly lower when only fed C. calcitrans as well as growth for those fed C. calcitrans or in combination with C. muelleri. However, for umbone larvae, survival and growth were significantly higher when fed a binary combination of T. Iso and C. muelleri or the ternary combination of T. Iso, C. muelleri and C. calcitrans compared with all other treatments. For the second experiment, results showed that with increasing lipid emulsion replacement, survival of both D-shaped and umbone larvae significantly decreased ( P < 0.05); however, the LIP100 treatment was not significantly different ( P > 0.05) from the unfed treatment. For D-shaped larvae, no significant growth difference was detected ( P > 0.05) between the T. Iso and LIP10 fed treatments while for umbone larvae, the T. Iso, LIP10 and LIP30 were not significantly different ( P > 005). These results indicate that microalgae combinations appear more necessary for later staged P. margaritifera larvae. In addition, the use of a lipid emulsion appeared to provide some nutrition to the larvae, although more research should be conducted to improve the use of such replacements. [ABSTRACT FROM AUTHOR]

We studied the feeding and growth rates, feed efficiency and nutritional composition of subadult octopuses (689 ± 77 g) fed low-lipid diets with two different protein/energy ratios (P/E): Medium P/E diet (30.5 g protein MJ−1, 662 g kg−1 protein dry weight (dw)) or High P/E diet (36.8 g protein MJ−1, 843 g kg−1 protein dw). Survival was 100% for the Medium P/E and 87.5% for the High P/E diet. The specific feeding rates were 1.91% and 1.67% body weight day−1 for the Medium P/E and High P/E diet, respectively ( P < 0.05). The specific growth rates (0.92% and 1.25% body weight day−1), feed efficiency indices (47.3% and 72.7%), productive protein value (23.9% and 29.1%) and digestive gland index (5.6% and 6.4%) were significantly better in animals fed the High P/E than the Medium P/E diet ( P < 0.05). The proximate composition of the digestive gland was similar for both diets, but the total lipid content of carcass was higher in animals fed the Medium P/E diet ( P < 0.05). Our results suggest that the protein content of the feed could be a factor regulating feeding rates in octopus. [ABSTRACT FROM AUTHOR]

Among the potential larval shell formation genes in mollusks, most are expressed in cells surrounding the shell field during the early phase of shell formation. The only exception ( cgi-tyr1) is expressed in the whole larval mantle and thus represents a novel type of expression pattern. This study reports another gene with such an expression pattern. The gene encoded a SoxC homolog of the Pacific oyster Crassostrea gigas and was named cgi-soxc. Whole-mount in situ hybridization revealed that the gene was highly expressed in the whole larval mantle of early larvae. Based on its spatiotemporal expression, cgi-soxc is hypothesized to be involved in periostracum biogenesis, biomineralization, and regulation of cell proliferation. Furthermore, we investigated the interrelationship between cgi-soxc expression and two additional potential shell formation genes, cgi-tyr1 and cgi-gata2/3. The results confirmed co-expression of the three genes in the larval mantle of early D-veliger. Nevertheless, cgi-gata2/3 was only expressed in the mantle edge, and the other two genes were expressed in all mantle cells. Based on the spatial expression patterns of the three genes, two cell groups were identified from the larval mantle ( tyr1 / soxc / gata2/3 cells and tyr1 / soxc / gata2/3 cells) and are important to study the differentiation and function of this tissue. The results of this study enrich our knowledge on the structure and function of larval mantle and provide important information to understand the molecular mechanisms of larval shell formation. [ABSTRACT FROM AUTHOR]

The first real-time evidence of the rotation of the operculum of the trochid gastropod Phorcus lineatus has been obtained by marking the operculum of live individuals and recording the angular orientation of the operculum in relation to the apertural tooth using time-lapse microscopy. Short-term monitoring of the rotation of opercula of juvenile P. lineatus in a temperature-controlled tidal aquarium at temperatures of 15 and 19 °C gave mean rates (clockwise) of 5.6 and 7.2°/d (0.097 and 0.126 rad/d), respectively, representing a 30% increase for a 4 °C rise in temperature and a complete turn in 1.7-2.0 months. A daily phase difference of 6 h in the tidal cycle had no effect on rates. Measured rates of opercular rotation were converted to more conventional growth rates, based on weight and physical dimensions, by using biometric data from the study population. In the case of weight, close agreement between theory and direct measurement was demonstrated. Quasi-regular series of imprints of the opercular disc and peripheral striae visible on some opercula are interpreted as evidence of a discontinuous mode of growth, the features acting like the 'ticks of a clock'. The ratio of the angular separation of these features to rates of opercular rotation is in close accord with a semidiurnal rhythm. The rate of opercular rotation is recommended as a growth parameter in its own right, measurement of which is useful (especially over short periods), for elucidating in fine detail the effects of environmental factors on growth in aquaria and mesocosms and, with more difficulty, on the shore. [ABSTRACT FROM AUTHOR]