Posts Tagged 'echinoderms'

Behavioral defenses of shellfish prey under ocean acidification

Biological interactions between predators and prey constitute a key component of the ecology and evolution of marine systems, and animal behavior can affect the outcome of predator–prey interactions. It has been recently demonstrated that CO2-induced ocean acidification can alter the behavior of marine organisms and potentially alter predator–prey dynamics. This study combines both quantitative (meta-analysis) and qualitative approaches to review the effects of ocean acidification on behavioral prey defenses in marine invertebrates. A systematic literature search identified 34 studies that experimentally assessed behavioral defenses under elevated pCO2 spanning three phyla: crustaceans, echinoderms, and molluscs. A meta-analysis suggested that exposure to elevated seawater pCO2 can negatively affect behavioral defenses in bivalve molluscs and malacostracan crustaceans. By contrast, defenses of cephalopod molluscs seem to be positively impacted by elevated pCO2, whereas gastropods and echinoids appear unaffected. A qualitative assessment of studies on combined effects of ocean acidification and warming revealed that combined effects typically differ from ocean acidification–only effects. Based on a qualitative assessment of three studies to date, neurological interference of GABAA receptors under elevated pCO2 may play a major role in ocean acidification effects on prey defense behaviors; however, more research is needed, and other mechanistic underpinnings are also important to consider. Ultimately, the results of this study suggest that behavioral prey defenses in some shellfish taxa may be vulnerable to ocean acidification, that the effects of ocean acidification are often different under warming scenarios than under present-day temperature scenarios, and that GABAA interference may be an important mechanism underpinning behavioral responses of shellfish prey under ocean acidification. Despite the importance of shellfish behavioral defenses in the ecology and evolution of marine biological communities, however, research to date has only scraped the surface in understanding ocean acidification effects. Increased research efforts on the effects of multiple stressors, acclimation and adaptation, environmental variability, and complex situational and ecological contexts are needed. Studies of fish behavioral defenses under ocean acidification can help streamline hypotheses and experimental approaches, particularly given the similar effects of elevated pCO2 on GABAA function.

Continue reading ‘Behavioral defenses of shellfish prey under ocean acidification’

Vertical distribution of echinoid larvae in pH stratified water columns

The abundance and distribution of many benthic marine organisms are shaped by the success of their dispersive larval life-history stage. An increasing number of studies have shown that ocean acidification negatively impacts the larval life-history stage, including those of echinoids which are commercially and ecologically important. However, little is known about the behavioral responses of echinoid larvae to different pH levels in the water column. Changes in vertical movement in response to the naturally occurring pH variations caused by biological activities and/or physical conditions could affect dispersal and recruitment. In this study, we quantified the vertical distribution of larval sand dollars, Dendraster excentricus (Echinodermata), in water columns with stratified layers of seawater varying in salinity and pH. When larval sand dollars swimming upwards in ambient seawater (pHNBS 7.86 ± 0.04) encountered a layer of low pH (pHNBS 7.54 ± 0.04) seawater, about half of the individuals (53 ± 28%) were aggregated near the transition layer 60 min after the start of the experiment. Preliminary video analysis showed larvae reversed their direction of travel and altered the shape of their helical swimming trajectories, upon encountering the transition layer moving from ambient to low pH water. In contrast, when larval sand dollars swimming upwards in acidified seawater encountered ambient seawater, they continued to swim upward to aggregate near the top of the column. In control water columns with uniform pH, larvae did not change swimming behavior regardless of whether pH was ambient or acidified and whether salinity was uniform or stratified. These results indicate that stratification itself did not strongly affect the vertical distributions of larvae. These observations suggest that echinoid larvae, and perhaps many other types of planktonic larvae, may use behavioral plasticity to reduce exposure to stresses from ocean acidification. The presence and effectiveness of these responses may improve the ability of larvae to cope with stressful, dynamic habitats, and hence may be significant to prediction of potential impacts of global climate change.

Continue reading ‘Vertical distribution of echinoid larvae in pH stratified water columns’

Sea urchins in a high CO2 world: impacts of climate warming and ocean acidification across life history stages

Uptake of anthropogenic carbon dioxide (CO2) is changing seawater chemistry (ocean acidification) causing a reduction in seawater pH and saturation state (Ω) of the CaCO3 minerals needed for calcification and increased organism hypercapnia (pCO2). Ocean acidification and global warming are having negative impacts on sea urchin larvae and adults. As sea urchins calcify in both these life stages, they have been used as a model group to investigate the impacts of climate change on marine species. In general, near-future acidification has a stunting effect on sea urchin growth as seen in smaller larval and adult skeletons, a change largely caused by energetic constraints and reduced Ω. These effects can be reduced by moderate warming and sufficient food supply. Variation in the response to acidification and/or warming within and between species indicates that there is capacity for phenotypic plasticity to adjust to changing climate. The presence of sea urchin populations at naturally acidified habitats indicates resilience to acidification and highlights species-specific and biological system adaptive strategies to life at low pH. We need to identify the sea urchin species that are resilient and their phenotypic plastic responses or genetic adaptations to climatic stressors to understand the echinoid fauna of the future.

Continue reading ‘Sea urchins in a high CO2 world: impacts of climate warming and ocean acidification across life history stages’

Parental acclimation to future ocean conditions increases development rates but decreases survival in sea urchin larvae

Environmental conditions experienced by parents can have lasting effects on offspring. For some marine organisms, parental acclimation may attenuate the negative effects observed in offspring exposed to the same conditions. Here, development of the coral reef sea urchin Echinometra sp. A was examined in larvae derived from parents acclimated for 20 months in either present-day conditions or those predicted for the year 2100 (+ 2 °C/pH 7.8). Egg size was measured, and larval morphology, survival and respiration were quantified in larvae raised in present-day (26 °C/pH 8.1) and 2100 (28 °C/pH 7.8) treatments to near settlement to determine whether parental acclimation promotes greater resilience to climate change stressors. Although there was no difference in egg size, larvae from 2100 parents were generally larger and more developmentally advanced than those derived from present-day parents. However, negative carryover effects reduced survival in offspring of parents acclimated to 2100 conditions. At 15 days post-fertilization, survival of offspring derived from 2100 parents was 50.6% and 43.7% when raised in present-day and 2100 conditions, respectively, compared to 59.9% and 64.6% in offspring derived from present-day parents. When raised in 2100 conditions, respiration declined by 36.8% in larvae derived from present-day parents, while respiration rates of larvae from 2100 parents increased by 109%, suggesting that carryover effects may be associated with higher energy consumption and physiological stress in larvae from 2100 parents. Although parental acclimation enhanced growth of larvae in early development, overall, negative carryover effects outweighed potential benefits of parental acclimation to ocean warming and acidification in this species.

Continue reading ‘Parental acclimation to future ocean conditions increases development rates but decreases survival in sea urchin larvae’

Behavioral responses to ocean acidification in marine invertebrates: new insights and future directions

Ocean acidification (OA) affects marine biodiversity and alters the structure and function of marine populations, communities, and ecosystems. Recently, effects of OA on the behavioral responses of marine animals have been given with much attention. While many of previous studies focuses on marine fish. Evidence suggests that marine invertebrate behaviors were also be affected. In this review, we discussed the effects of C02-driven OA on the most common behaviors studied in marine invertebrates, including settlement and habitat selection, feeding, anti-predatory, and swimming behaviors, and explored the related mechanisms behind behaviors. This review summarizes how OA affects marine invertebrate behavior, and provides new insights and highlights novel areas for future research.

Continue reading ‘Behavioral responses to ocean acidification in marine invertebrates: new insights and future directions’

Impact of growing up in a warmer, lower pH future on offspring performance: transgenerational plasticity in a pan-tropical sea urchin

Transgenerational plasticity (TGP) may be an important mechanism for marine organisms to acclimate to climate change stressors including ocean warming (OW) and ocean acidification (OA). Conversely, environmental stress experienced by one generation may have detrimental latent effects on subsequent generations. We examined TGP in the embryos and larvae of the pan-tropical sea urchin, Tripneustes gratilla, in response to OA (pH 7.77), OW (+2 °C), or both OA and OW, OAW (+2 °C, pH 7.77) using a parent (F0) generation reared in treatments from the early juvenile to the mature adult, incorporating gonadogenesis and germline differentiation. Embryos and larvae of acclimated parents were reared in all four treatments to the 2-day-old pluteus stage. Larvae from OA and OAW parents were resilient to the effects of acidification, while larvae from OW and OAW parents were more tolerant to warmer temperature (29 °C). Parental acclimation, however, had predominantly negative effects on the size of offspring with reductions in larval arm lengths by as much as 21.4%, while eggs were up to 21.8% smaller in females raised at 29 °C. We highlight the complexity and trade-offs of TGP in this first transgenerational climate change study on a marine macroinvertebrate where the F0 generation was acclimated over their reproductive life.

Continue reading ‘Impact of growing up in a warmer, lower pH future on offspring performance: transgenerational plasticity in a pan-tropical sea urchin’

Elevated pCO2 does not impair performance in autotomised individuals of the intertidal predatory starfish Asterias rubens (Linnaeus, 1758)

Highlights

• Ocean acidification research requires further understanding on the interactions with other stressors.

• We examined the combined effects of pCO2 and arm autotomisation on Asterias rubens.

• Neither stressor affected mortality, growth, arm regeneration, righting time or arm calcium content.

• Lipid content in the pyloric caeca increased in response to elevated pCO2.

• A. rubens appears unaffected by short-term exposure to pCO2 levels predicted for 2100.

Abstract

The impacts of ocean acidification remain less well-studied in starfish compared to other echinoderm groups. This study examined the combined effects of elevated pCO2 and arm regeneration on the performance of the intertidal predatory starfish Asterias rubens, as both are predicted to come at a cost to the individual. A two-way factorial experiment (~400 μatm vs ~1000 μatm; autotomised vs non-automised individuals) was used to examine growth rates, lipid content (pyloric caeca and gonads), and calcium content (body wall) in both intact and regenerating arms, as well as subsequent effects on rate of arm regeneration, righting time (behaviour) and mortality over 120 days. Autotomised individuals tended to show lower (not significant), survival and growth. Elevated pCO2 had no effect on mortality, body growth, arm regeneration, righting time or arm calcium content. Lipid content was higher in the pyloric caeca, but not in the gonads, in response to elevated pCO2 irrespective of autotomisation. The results of the study suggest that adult A. rubens remain unaffected by increased pCO2 and/or arm autotomy for 120 days, although longer term experiments are necessary as the results indicated that survival, growth and calcification may be impaired with longer-term exposure to elevated pCO2.

Continue reading ‘Elevated pCO2 does not impair performance in autotomised individuals of the intertidal predatory starfish Asterias rubens (Linnaeus, 1758)’


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