Ocean acidification poses a significant threat to calcifying invertebrates by negatively influencing shell deposition and growth. An organism’s performance under ocean acidification is not determined by the susceptibility of one single life-history stage, nor is it solely controlled by the direct physical consequences of ocean acidification. Shell development by one life-history stage is sometimes a function of the pH or pCO2 levels experienced during earlier developmental stages. Furthermore, environmental factors such as access to nutrition can buffer organismal responses of calcifying invertebrates to ocean acidification, or they can function as a co-occurring stressor when access is low. We reared larvae and juveniles of the planktotrophic marine gastropod Crepidula fornicata through combined treatments of nutritional stress and low pH, and we monitored how multiple stressors endured during the larval stage affected juvenile performance. Shell growth responded non-linearly to decreasing pH, significantly declining between pH 7.6 and pH 7.5 in larvae and juveniles. Larval rearing at pH 7.5 reduced juvenile growth as a carryover effect. Larval rearing at pH 7.6 reduced subsequent juvenile growth despite the absence of a negative impact on larval growth, demonstrating a latent effect. Low larval pH magnified the impact of larval nutritional stress on competence for metamorphosis and increased carryover effects of larval nutrition on juvenile growth. Trans-life-cycle effects of larval nutrition were thus modulated by larval exposure to ocean acidification.
Two juvenile specimens of a new species of Oreaster were collected at Parque Nacional Arrecife Alacranes and Triángulos Oeste in the southern Gulf of Mexico. DNA of mitochondrial loci identifies them as members of the same clade as cloning larvae of Oreaster found abundantly in waters of the Florida Current-Gulf Stream system, and distinct from Oreaster clavatus and Oreaster reticulatus, the two known Oreasteridae species in the North Atlantic. Larvae from the new species of Oreaster persist as clones but also metamorphose and settle to the benthos with typical asteroid morphology.
Sporadic fluctuations in food availability may affect larval biology and post-metamorphic development in many marine invertebrates. In an experimental study in the laboratory, we investigated whether different regimes (1, 3, and 5 days) of initial starvation or feeding affect the survival and duration of the last planktotrophic larval stage (i.e., megalopa) of the neotropical mangrove fiddler crab Leptuca cumulanta. Newly metamorphosed crabs originating from megalopae starved for 1 and 3 days were cultured through the first 5 juvenile stages to further evaluate whether prior nutritional experience affects the post-larval performance of this species. All megalopae that were starved continuously died, while 80% of the larvae that were fed constantly metamorphosed successfully into the juvenile stage. Megalopae initially starved for 3 and 5 days exhibited lower survival (55% and 30% of larval metamorphosis, respectively) than larvae starved for only 1 day (85%) or fed constantly. The starvation periods (1, 3, and 5 days) also significantly prolonged the mean megalopal stage duration (12.8, 13.9, and 14.3 days, respectively) compared to the continuous feeding regime (10.6 days). Survival of the megalopae subjected to different periods of initial feeding (1, 3, and 5 days) was significantly lower (15.0%, 57.5%, and 62.5%, respectively) than survival of the larvae fed constantly. The mean megalopal stage duration, by contrast, did not vary among megalopae initially fed for 3 and 5 days or fed continuously (10.4 days). The larval starvation did not affect survival and carapace shape of juveniles, but it did alter their intermolt period, growth, and body size. These carryover effects were stronger in the first juvenile crab stage than in other juvenile stages. Our results indicate that the timing and duration of the starvation or feeding regime experienced by the megalopae may affect their successful survival and developmental period until metamorphosis to juvenile life. In addition, the preceding larval starvation associated with a prolonged larval period may also affect early juvenile performance in specific crab stages of L. cumulanta.
The barnacle Balanus glandula is a broadly distributed species in the temperate northeastern Pacific that is notable for a robust genetic cline between about 36° and 40° N latitude. Prior work established the evolutionary origins of this pattern and proposed that it is maintained by environmental selection. In recent years, “climate velocity” studies in marine habitats have shown dramatic distributional shifts for many species as they track their preferred temperature range in a warming ocean. We re-sampled B. glandula across its entire geographic range to determine whether there has been any shift in this genetic distribution, a development signaling that temperature or other climate factors are maintaining this genetic cline. Additionally, we asked whether the spatially distributed mitochondrial lineages also vary in reproductive output with latitude, using location as a proxy for temperature and other coastal environmental factors. Here we show that although the distribution of the genetic cline has not appreciably changed, there is a notable association of decreased reproductive output at lower latitudes of the distribution in the “northern” lineage of B. glandula.
Horseshoe crabs are harvested by the biomedical industry in order to create Limulus amebocyte lysate to test medical devices and pharmaceutical drugs for endotoxins. Most previous studies on the impacts of the biomedical bleeding process on horseshoe crabs have focused on mortality rates and sublethal impacts in the laboratory. In this study, we investigated the effects of the bleeding process on the behavior of horseshoe crabs after they had been released back into their natural environment. A total of 28 horseshoe crabs (14 control and 14 bled) were fitted with acoustic transmitters and released into the Great Bay Estuary, New Hampshire, during the spring of 2016. The acoustic tags transmitted information about the activity and depth of each animal, and these data were logged by an array of passive acoustic receivers. These data were collected from May to December 2016 and from March to October 2017. Bled animals approached mating beaches less than control animals during the first week after release, with the greatest differences between bled and control females. Bled animals also remained significantly deeper during the spawning season than control animals. However, overall, bled and control animals expressed similar biological rhythms and seasonal migrations. Thus, it appears as if the most obvious impacts of the bleeding process take place during the first one to two weeks after crabs are bled.
Salinity is one of the most crucial environmental factors that structures biogeographic boundaries of aquatic organisms, affecting distribution, abundance, and behavior. However, the association between behavior and gene regulation underlying acclimation to changes in salinity remains poorly understood. In this study, we investigated the effects of salinity stress on behavior (movement distance) and patterns of gene expression (using RNA sequencing) of the intertidal gastropod Batillaria attramentaria. We examined responses to short-term (1-hour) and long-term (30-day) acclimation to a range of salinities (43, 33 [control], 23, 13, and 3 psu). We found that the intertidal B. attramentaria is able to tolerate a broad range of salinity from 13 to 43 psu but not the acute low salinity of 3 psu. Behavioral experiments showed that salt stress significantly influenced snails’ movement, with lower salinity resulting in shorter movement distance. Transcriptomic analyses revealed critical metabolic pathways and genes potentially involved in acclimation to salinity stress, including ionic and osmotic regulation, signal and hormonal transduction pathways, water exchange, cell protection, and gene regulation or epigenetic modification. In general, our study presents a robust, integrative laboratory-based approach to investigate the effects of salt stress on a nonmodel gastropod facing detrimental consequences of environmental change. The current genetic results provide a wealth of reference data for further research on mechanisms of ionic and osmotic regulation and adaptive evolution of this coastal gastropod.