Latitudinal thermal gradient effect on the cost of living of the intertidal porcelain crab Petrolisthes granulosus

Species with wide latitudinal distributions are exposed to significant abiotic gradients throughout their geographic range. Thermal gradients are especially important for ectothermic species inhabiting the intertidal zone because they affect their life history traits and fitness. In order to identify the role of latitudinal thermal gradients (specifically the exposition to different thermal maximums) in the cost of living of intertidal crustaceans, we compared specific fitness-related traits, such as body size and reproductive capacity (reproductive output, size at onset of sexual maturity and egg volume) in Petrolisthes granulosus individuals from 3 sites across an extensive latitudinal gradient (covering similar to 50% of its total distributional range): Iquique (20 degrees 16' 12 '' S), Coquimbo (30 degrees 04' 12 '' S) and Concepcion (36 degrees 40' 45 '' S). Furthermore, metabolic rate experiments were conducted to assess the energetic cost associated with high temperatures encountered in P. granulosus habitats. We observed that the southernmost population (Concepcion) had a larger body size and presented larger size classes that did not exist in northerly populations. The latitudinal trend shown by growth and reproductive capacity traits was negatively linked to the associated thermal gradient. However, no differences were found in the relationship between energetic cost (in terms of metabolic rate) and temperatures experienced by P. granulosus. Thus, the patterns of body size and reproductive capacity observed for P. granulosus could not be explained by differences in energetic costs generated by the different thermal regimes of the study sites. Further studies should consider other environmental (e.g. quantity and quality of available food) and/or genetic factors that may be influencing the latitudinal patterns observed for body size and reproductive output in P. granulosus

Molecular characterization and expression patterns of peroxiredoxin V (PrxV) from the scallop Argopecten purpuratus after Vibrio splendidus challenge

The scallop Argopecten purpuratus is a species of importance for aquaculture in Chile and Peru, but in recent years, they have decreased their growth rates and experienced massive mortalities potentially associated with pathogenic infections. Characterization of proteins involved in the immunity status of A. purpuratus is of interest to develop molecular markers to support its culture. Here we report the characterization of a new Peroxiredoxin (Prx) homologue, the first one identified in A. purpuratus. Prxs are a ubiquitous family of cysteine-dependent peroxidase enzymes that play a dominant role in the regulation of peroxide levels in cells, as rapidly detoxify peroxynitrite, hydrogen peroxide and organic hydroperoxides. The molecular and phylogenetic analyses of this gene showed that it is a new member of the PrxV family, thus, it was designated as ApPrxV. This gene showed to be constitutively expressed in each examined tissue, but at a higher level in the striated adductor muscle. ApPrxV expression was highly upregulated in haemocytes in response to an immune challenge with pathogen bacteria Vibrio splendidus. Overall results indicate that ApPrxV is a constitutive and inducible protein that can play an important role in the immune response of A. purpuratus against bacterial infection. Therefore, the results of this study can (i) provide the bases for future functional studies to assess the health status of A. purpuratus; and (ii) can guide the development of molecular markers for future selective breeding of this bivalve

First insight into the heritable variation and potential response to selection of phototaxis and locomotion behavior associated to the light/dark stimuli in the abalone Haliotis discus hannai

© 2018 Elsevier B.V. Abalones are especially susceptible to environmental lighting conditions. This factor greatly affects crucial biological process such as feeding rates, energy balance, physiological stress status, and consequently, growth and survival of farmed abalone. Most of these effects have been studied in the economically valuable abalone Haliotis discus hannai. The use of specific photoperiods, and/or light qualities and intensities, have been proposed as managing strategies to increase its production; however, for extensive off-shore or in intensive land-based farming systems, lighting conditions are not likely to be easily managed. Despite the great importance of the biological responses to the light/dark stimuli for abalone farming production, to the best of our knowledge the genetic control upon the variation associated behavioral traits have not been studied. Therefore, the aim of this study was to estimate the heritable variation and potential responses to selection

The Gill Microbiota of <i>Argopecten purpuratus</i> Scallop Is Dominated by Symbiotic Campylobacterota and Upwelling Intensification Differentially Affects Their Abundance

Despite the great importance of gills for bivalve mollusks (respiration, feeding, immunity), the microbiota associated with this tissue has barely been characterized in scallops. The scallop Argopecten purpuratus is an important economic resource that is cultivated in areas where coastal upwelling is intensifying by climate change, potentially affecting host-microbiota interactions. Thus, we first characterized the bacterial community present in gills from cultivated scallops (by 16S rRNA gene amplicon sequencing) and assessed their stability and functional potential in animals under farm and laboratory conditions. Results showed that under both conditions the gill bacterial community is dominated by the phylum Campylobacterota (57%), which displays a chemoautotrophic potential that could contribute to scallop nutrition. Within this phylum, two phylotypes, namely symbionts A and B, were the most abundant; being, respectively, taxonomically affiliated to symbionts with nutritional functions in mussel gills, and to uncultured bacteria present in coral mucus. Additionally, in situ hybridization and scanning electron microscopy analyses allowed us to detect these symbionts in the gills of A. purpuratus. Given that shifts in upwelling phenology can cause disturbances to ecosystems, affecting bacteria that provide beneficial functions to the host, we further assessed the changes in the abundance of the two symbionts (via qPCR) in response to a simulated upwelling intensification. The exposure to combined decreasing values in the temperature, pH, and oxygen levels (upwelling conditions) favored the dominance of symbiont B over symbiont A; suggesting that symbiont abundances are modulated by these environmental changes. Overall, results showed that changes in the main Campylobacterota phylotypes in response to upwelling intensification could affect its symbiotic function in A. purpuratus under future climate change scenarios. These results provide the first insight into understanding how scallop gill-microbial systems adapt and respond to climate change stressors, which could be critical for managing health, nutrition, and scallop aquaculture productivity

Phenotypic means and genetic estimates for HSP70 induced levels, measured in the haemocyte (intracellular) and serum (extracellular) fractions of the haemolymph of challenged <i>Haliotis rufescens</i> at two development stages, young adults and near harvest adults.

<p>Genetic estimates of the additive genetic variance (<i>V</i>_A); residual variance (<i>V</i>_R); phenotypic variance (<i>V</i>_P); heritability (<i>h</i>^<i>2</i>); and coefficients of additive genetic variance (<i>CV</i>_A) and residual variance (<i>CV</i>_R).</p><p>Immune response through HSP70 expression was assessed in abalone belonging to 60 full-sib families (n = 492 and 357 for young and near harvest adults, respectively). Genetic parameters were estimated using two models ^a(S-m, simple model that only included the additive genetic effect as a random effect for young adults; and ^bSO-m, model that also included the order of sampling as a fixed effect for near harvest adults). Models changed depending on the factors that were significant at a specific age. Phenotypic means were compared by two-way ANOVA (different letters denote significant differences at <i>P</i> < 0.01)</p><p>Phenotypic means and genetic estimates for HSP70 induced levels, measured in the haemocyte (intracellular) and serum (extracellular) fractions of the haemolymph of challenged <i>Haliotis rufescens</i> at two development stages, young adults and near harvest adults.</p

Potential Response to Selection of HSP70 as a Component of Innate Immunity in the Abalone <i>Haliotis rufescens</i>

<div><p>Assessing components of the immune system may reflect disease resistance. In some invertebrates, heat shock proteins (HSPs) are immune effectors and have been described as potent activators of the innate immune response. Several diseases have become a threat to abalone farming worldwide; therefore, increasing disease resistance is considered to be a long-term goal for breeding programs. A trait will respond to selection only if it is determined partially by additive genetic variation. The aim of this study was to estimate the heritability (<i>h</i>²) and the additive genetic coefficient of variation (<i>CV</i>_A) of HSP70 as a component of innate immunity of the abalone <i>Haliotis rufescens</i>, in order to assess its potential response to selection. These genetic components were estimated for the variations in the intracellular (in haemocytes) and extracellular (serum) protein levels of HSP70 in response to an immunostimulant agent in 60 full-sib families of <i>H</i>. <i>rufescens</i>. Levels of HSP70 were measured twice in the same individuals, first when they were young and again when they were pre-harvest adults, to estimate the repeatability (<i>R</i>), the <i>h</i>² and the potential response to selection of these traits at these life stages. High HSP70 levels were observed in abalones subjected to immunostimulation in both the intracellular and extracellular haemolymph fractions. This is the first time that changes in serum levels of HSP70 have been reported in response to an immune challenge in molluscs. HSP70 levels in both fractions and at both ages showed low <i>h</i>² and <i>R</i>, with values that were not significantly different from zero. However, HSP70 induced levels had a <i>CV</i>_A of 13.3–16.2% in young adults and of 2.7–8.1% in pre-harvest adults. Thus, despite its low <i>h</i>², HSP70 synthesis in response to an immune challenge in red abalone has the potential to evolve through selection because of its large phenotypic variation and the presence of additive genetic variance, especially in young animals.</p></div

Induced levels of HSP70 in haemocytes and serum of challenged red abalone <i>Haliotis rufescens</i>.

<p>HSP70 levels were measured in the intracellular (haemocytes) and extracellular (serum) fractions of <i>H</i>. <i>rufescens</i>, in individual not injected (i.e., injection control), injected with sterilized sea water (SSW) (i.e., challenge control) and injected with the β-glucan, zymosan (24-h post-injection). The data are shown as X ± S.E., n = 6–10 per condition. (*) indicates significance (<i>P</i> < 0.01) between treatment and controls at the indicated haemolymph fraction.</p

A Diet Rich in HUFAs Enhances the Energetic and Immune Response Capacities of Larvae of the Scallop <i>Argopecten purpuratus</i>

Massive mortalities in farmed larvae of the scallop Argopecten purpuratus have been associated with pathogenic Vibrio outbreaks. An energetic trade-off between development-associated demands and immune capacity has been observed. Given that highly unsaturated fatty acids (HUFAs) are essential nutrients for larval development, we evaluated the effect of diets based on microalgae low and high in HUFAs (LH and HH, respectively) on the energetic condition and the immune response of scallop larvae. The results showed that the HH diet increased cellular membrane fluidity in veliger larvae. The routine respiration rate was 64% higher in the HH-fed veligers than in the LH-fed veligers. Additionally, the metabolic capacity tended to be higher in the HH-fed veligers than in the LH-fed veligers after the Vibrio challenge. After the challenge, the HH-fed veligers presented higher transcript induction of ApTLR (immune receptor) and ApGlys (immune effector) genes, and the HH-fed pediveligers presented higher induction of ApLBP/BPI1 (antimicrobial immune effector) gene, than the LH-fed larvae. Furthermore, the HH-fed veligers controlled total Vibrio proliferation (maintaining near basal levels) after the bacterial challenge, while the LH-fed veligers were not able to control this proliferation, which increased three-fold. Finally, the HH-fed larvae showed 20–25% higher growth and survival rates than the LH-fed veligers. Overall, the results indicated that the administration of a HH diet increases cell membrane fluidity and energy metabolic capacity, which in turn enhances immunity and the ability to control Vibrio proliferation. The administration of microalgae high in HUFAs would be a promising strategy for improving scallop larval production efficiency

The combined effects of ocean acidification and warming on a habitat-forming shell-crushing predatory crab

In mid rocky intertidal habitats the mussel Perumytilus purpurarus monopolizes the substratumto the detriment of many other species. However, the consumption of mussels by the shell-crushing crab Acanthocyclus hassleri creates within the mussel beds space and habitat for several other species. This crab uses its disproportionately large claw to crush its shelled prey and plays an important role in maintaining species biodiversity. This study evaluated the consequences of projected near-future ocean acidification (OA) and warming (OW) on traits of A. hassleri linked with their predatory performance. Individual A. hassleri were maintained for 10-16 weeks under contrasting pCO(2) (similar to 500 and 1400 mu atm) and temperature (similar to 15 and 20 degrees C) levels. We compared traits at the organismal (oxygen consumption rate, survival, calcification rate, feeding rates, crusher claw pinching strength, self-righting speed, sarcomere length of the crusher claw muscles) and cellular (nutritional status ATP provisioning capacity through citrate synthase activity, expression of HSP70) level. Survival, calcification rate and sarcomere length were not affected by OA and OW. However, OW increased significantly feeding and, oxygen consumption. Pinching strength was reduced by OA; meanwhile self-righting was increased by OA and OW. At 20 degrees C, carbohydrate content was reduced significantly by OA. Regardless of temperature, a significant reduction in energy reserves in terms of protein content by OA was found. The ATP provisioning capacity was significantly affected by the interaction between temperature and pCO(2) and was highest at 15 degrees C and present day pCO(2) levels. The HSP70 levels of crabs exposed to OW were higher than in the control crabs. We conclude that OAand OWmight affect the amount and size of prey consumed by this crab. Therefore, by reducing the crab feeding performance these stressors might pose limits on their role in generating microhabitat for other rocky intertidal species inhabiting within mussel beds. (C) 2020 Elsevier B.V. All rights reserved