Posts Tagged 'reproduction'



Expression of calcification‐related ion transporters during blue mussel larval development

The physiological processes driving the rapid rates of calcification in larval bivalves are poorly understood. Here, we use a calcification substrate‐limited approach (low dissolved inorganic carbon, CT) and mRNA sequencing to identify proteins involved in bicarbonate acquisition during shell formation. As a secondary approach, we examined expression of ion transport and shell matrix proteins (SMPs) over the course of larval development and shell formation. We reared four families of Mytilus edulis under ambient (ca. 1865 µmol/kg) and low CT (ca. 941 µmol/kg) conditions and compared expression patterns at six developmental time points. Larvae reared under low CT exhibited a developmental delay, and a small subset of contigs was differentially regulated between ambient and low CT conditions. Of particular note was the identification of one contig encoding an anion transporter (SLC26) which was strongly upregulated (2.3–2.9 fold) under low CT conditions. By analyzing gene expression profiles over the course of larval development, we are able to isolate sequences encoding ion transport and SMPs to enhance our understanding of cellular pathways underlying larval calcification processes. In particular, we observe the differential expression of contigs encoding SLC4 family members (sodium bicarbonate cotransporters, anion exchangers), calcium‐transporting ATPases, sodium/calcium exchangers, and SMPs such as nacrein, tyrosinase, and transcripts related to chitin production. With a range of candidate genes, this work identifies ion transport pathways in bivalve larvae and by applying comparative genomics to investigate temporal expression patterns, provides a foundation for further studies to functionally characterize the proteins involved in larval calcification.

Continue reading ‘Expression of calcification‐related ion transporters during blue mussel larval development’

Parental environments alter DNA methylation in offspring of the purple sea urchin, Strongylocentrotus purpuratus

Highlights
• Maternal environment impacts DNA methylation of early stage offspring.

• Developmental environment has a minimal impact on DNA methylation.

• DNA methylation differences across developmental stages are minimal.

• Differences in DNA methylation is associated with body size of embryos.

Abstract
Phenotypic plasticity, within and across generations, is a strategy by which organisms can respond rapidly to environmental change. Epigenetic modifications, such as DNA methylation, have been proposed to be involved in phenotypic plasticity. We examined the potential for the environment to mediate both transgenerational and intragenerational plasticity in DNA methylation and phenotypes in early stages of the purple sea urchin, Strongylocentrotus purpuratus, an ecologically important herbivore in kelp forest ecosystems. This approach involved a controlled laboratory experiment where adult urchins were acclimated during gametogenesis to upwelling (~1300 μatm pCO2 & 13 °C) or non-upwelling (~650 μatm pCO2 & 17 °C) conditions that are representative of their kelp forest habitat. Progeny from these adults were raised in either high (~1050 μatm) or low (~450 μatm) pCO2 treatments and sampled at three developmental stages. Differences in condition experienced by mothers were associated with differentially methylated genes in the offspring. However, differences in developmental conditions corresponded to little observable effects on gene methylation in the progeny. Variation in gene body methylation across treatments was correlated with body size of the embryos and larvae, illustrating a potential link between transgenerational phenotypic plasticity and DNA methylation. Overall, our results suggest that epigenetic factors such as DNA methylation have the potential to contribute to phenotypic plasticity in a transgenerational framework, and further, that epigenetic processes may act as a mechanism of rapid response to environmental change.

Continue reading ‘Parental environments alter DNA methylation in offspring of the purple sea urchin, Strongylocentrotus purpuratus’

Extreme, but not moderate climate scenarios, impart sublethal effects on polyps of the Irukandji jellyfish, Carukia barnesi

Highlights
• Sublethal effects on Carukia barnesi polyps only manifested in extreme conditions.

• Individual metabolites were suppressed in extreme pH and elevated temperature treatments.

• C. barnesi polyps are unaffected by the most optimistic climate scenario and can survive in extreme conditions.

Abstract
Ocean acidification and warming, fueled by excess atmospheric carbon dioxide, can impose stress on marine organisms. Most studies testing the effects of climate change on marine organisms, however, use extreme climate projection scenarios, despite moderate projections scenarios being most likely to occur. Here, we examined the interactive effects of warming and acidification on reproduction, respiration, mobility and metabolic composition of polyps of the Irukandji jellyfish, Carukia barnesi, to determine the responses of a cubozoan jellyfish to moderate and extreme climate scenarios in Queensland, Australia. The experiment consisted two orthogonal factors: temperature (current 25 °C and future 28 °C) and pH (current (8.0) moderate (7.9) and extreme (7.7)). All polyps survived in the experiment but fewer polyps were produced in the pH 7.7 treatment compared to pH 7.9 and pH 8.0. Respiration rates were elevated in the lowest pH treatment throughout most of the experiment and polyps were approximately half as mobile in this treatment compared to pH 7.9 and pH 8.0, regardless of temperature. We identified metabolites occurring at significantly lower relative abundance in the lowest pH (i.e. glutamate, acetate, betaine, methylguanidine, lysine, sarcosine, glycine) and elevated temperature (i.e. proline, trigonelline, creatinine, mannose, acetate, betaine, methylguanidine, lysine, sarcosine) treatments. Glycine was the only metabolite exhibiting an interactive effect between pH and temperature. Our results suggest that C. barnesi polyps are unaffected by the most optimistic climate scenario and may tolerate even extreme climate conditions to some extent.

Continue reading ‘Extreme, but not moderate climate scenarios, impart sublethal effects on polyps of the Irukandji jellyfish, Carukia barnesi’

Sperm motility of oysters from distinct populations differs in response to ocean acidification and freshening

Species’ responses to climate change will reflect variability in the effects of physiological selection that future conditions impose. Here, we considered the effects of ocean acidification (increases in pCO2; 606, 925, 1250 µatm) and freshening (reductions in salinity; 33, 23, 13 PSU) on sperm motility in oysters (Crassostrea gigas) from two populations (one recently invaded, one established for 60+ years). Freshening reduced sperm motility in the established population, but this was offset by a positive effect of acidification. Freshening also reduced sperm motility in the recently invaded population, but acidification had no effect. Response direction, strength, and variance differed among individuals within each population. For the established population, freshening increased variance in sperm motility, and exposure to both acidification and freshening modified the performance rank of males (i.e. rank motility of sperm). In contrast, for the recently invaded population, freshening caused a smaller change in variance, and male performance rank was broadly consistent across treatments. That inter-population differences in response may be related to environmental history (recently invaded, or established), indicates this could influence scope for selection and adaptation. These results highlight the need to consider variation within and among population responses to forecast effects of multiple environmental change drivers.

Continue reading ‘Sperm motility of oysters from distinct populations differs in response to ocean acidification and freshening’

An experimental evaluation of the sensitivity of coastal marine fishes to acidification, hypoxia, and warming

Ocean acidification (OA) during the coming century will impact marine ecosystems in profound ways. Laboratory studies have played a pioneering role in identifying biological vulnerabilities and have documented deleterious effects in taxonomically diverse fauna. The early life-stages of marine fish may be particularly sensitive to OA, thereby constituting a global threat to some of the world’s most important marine resources. Despite the rapid accumulation of experimental evidence, considerable uncertainty remains in estimating the scope of OA impacts. To date, most studies have relied on relatively short-term exposures to estimate effects of elevated pCO, while few have considered longer term OA effect across multiple life-stages. Additionally, while single-factor CO2 experiments are a necessary first step in identifying OA sensitivities, there is a growing understanding that OA will proceed concurrently with warming and deoxygenation, yet multi-stressor factorial experiments remain rare. Furthermore, meta-analyses of existing research have highlighted the large, and thus far unexplained variability in OA responses among taxa and populations. One promising mechanism which could explain this variability involves the role of local adaptation to existing pCO2fluctuations that characterizes marine habitats to different degrees. This framework remains untested in fish. The primary goal of this dissertation was to apply state-of-the-art experimental techniques to address the aforementioned knowledge gaps. By using two ecological important forage species, the Atlantic silverside (Menidia menidia) and Northern sand lance (Ammodytes dubius) with contrasting life-history characteristics, this dissertation provides novel insights into potential near-future climate impacts on fish. Chapter 1 summarizes a long-term OA experiment on M. menidia finding that elevated pCO2 exposure resulted in small but significant reductions in offspring size and condition factor. Chapter 2 tested CO2 × temperature effects in M. menidia offspring and found complex growth and survival responses. Chapter 3 reports on CO2 × temperature trials on offspring of A. dubius and documented precipitous reductions to survival and growth. Chapter 4 describes two CO2 × dissolved oxygen trials on M. menidia offspring that demonstrated a negative synergistic effect on embryonic survival. Together, this dissertation provides much needed baseline data and novel insights into climate effects in forage fish.

Continue reading ‘An experimental evaluation of the sensitivity of coastal marine fishes to acidification, hypoxia, and warming’

Effect of ocean acidification on the nutritional quality of marine phytoplankton for copepod reproduction

Phytoplankton are the oceans’ principal source of polyunsaturated fatty acids that support the growth and reproduction of consumers such as copepods. Previous studies have demonstrated ocean acidification (OA) can change the availability of polyunsaturated fatty acids to consumer diets which may affect consumer reproduction. Two laboratory experiments were conducted to examine the effects of feeding high-pCO2-reared phytoplankton on copepod egg production, hatching success, and naupliar survival. Marine phytoplankton Rhodomonas salina, Skeletonema marinoi, Prorocentrum micans, and Isochrysis galbana were exponentially grown in semi-continuous cultures at present (control) (400 ppm CO2, pH~8.1) and future (1,000 ppm CO2, pH~7.8) conditions and provided to Acartia tonsa copepods over 4 consecutive days as either nitrogen-limited (Exp. I) or nitrogen-depleted (Exp. II) mixed assemblage of phytoplankton. The composition of FAs in the phytoplankton diet was affected by pCO2 concentration and nitrogen deficiency; the ratio of essential fatty acids to total polyunsaturated fatty acids decreased in phytoplankton grown under high pCO2 and the mass of total fatty acids increased under nitrogen depletion. Additionally, total concentrations of essential fatty acids and polyunsaturated fatty acids in the diet mixtures were less under the high-pCO2 compared to the control-pCO2 treatments. Median egg production, hatching success, and naupliar survival were 48–52%, 4–87%, and 9–100% lower, respectively, in females fed high-pCO2 than females fed low-pCO2 phytoplankton, but this decrease in reproductive success was less severe when fed N-depleted, but fatty acid-rich cells. This study demonstrates that the effects of OA on the nutritional quality of phytoplankton (i.e., their cellular fatty acid composition and quota) were modified by the level of nitrogen deficiency and the resulting negative reproductive response of marine primary consumers.

Continue reading ‘Effect of ocean acidification on the nutritional quality of marine phytoplankton for copepod reproduction’

Physiological effects of climate change on the American lobster, Homarus americanus

Increases in anthropogenic input of carbon dioxide into the atmosphere have caused widespread patterns of ocean warming and ocean acidification. Both processes will likely have major impacts on commercial fisheries and aquaculture, with acidification posing a particular threat to many marine calcifying invertebrates. In the State of Maine, commercial fisheries landings and a growing aquaculture industry have a combined value in excess of $600 million, 75% of which is sustained by marine calcifiers. Moreover, the American lobster (Homarus americanus) supports the most economically valuable fishery in the Gulf of Maine and Atlantic Canada. Previous research has documented a strong link between lobster biology and ocean temperature, but it is unclear how H. americanuswill respond to a rapidly changing environment. Additionally, previous efforts have focused primarily on the direct effects of a changing climate on lobsters (i.e., changes in growth, survival, and calcification), with little emphasis placed on the potential for sublethal effects to impact the population.

In this dissertation, I explore the effects of increasing ocean temperatures and acidification on H. americanus to understand how environmental changes can alter the health and physiology in multiple life stages of marine calcifying invertebrates. In Chapter 1, I introduce the global patterns and effects of climate change on marine calcifiers and review the current state of knowledge of my study species. In Chapter 2, I discuss how exposure to warming conditions impacts larval development, with a focus on potential trade-offs between enhanced growth and developmental instability. In Chapter 3, I continue to explore the sublethal impacts of warming on larval lobsters by examining changes in gene expression patterns in postlarvae exposed to varying temperatures during development. Chapter 4 explores how short-term exposure to acidified conditions impacts subadult (50 – 65 mm carapace length) lobster thermal physiology, hemolymph chemistry, and stress levels, a relatively understudied yet crucial life history stage. Finally, Chapter 5 summarizes the overarching themes of the dissertation, and concludes by providing suggestions for future research efforts.

Continue reading ‘Physiological effects of climate change on the American lobster, Homarus americanus’


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Ocean acidification in the IPCC AR5 WG II

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