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Global average temperatures and sea water pCO2 have rapidly increased due to the oceanic uptake of atmospheric carbon dioxide producing severe consequences for a broad range of species. The impacts on marine ectotherms have been largely reported at short-term scales (i.e. from days to weeks); however, the prolonged effects on long-term processes such as reproduction have received little attention. The gastropod Ocenebra erinaceus is a key predator structuring communities on rocky shores of the French and UK coasts. Even though rocky shore species are regarded as being very tolerant to changes in temperature and pH, many of them are living near their upper tolerance limits, making them susceptible to rapid environmental changes. Here, we report that future mean sea water conditions (RCP8.5, + 3°C and ~ 900 µatm CO2) do not significantly affect the physiology and molecular response of O. erinaceus adults after 132 days. During the first fifty-days, there was a slight impact on oxygen consumption rates and body weight; however, after ninety-five days of exposure, gastropods relied on food resources to fully acclimate to the experimental condition. Despite this, it was after long-term exposure (~ 10 months) reproduction ceased in females exposed to these future sea water conditions. Therefore, in the short-term O. erinaceus appear to be capable of full compensation; however, in the long-term, they fail to invest in reproduction. Future research should take into account the combined results from both, short- and long-term effects to improve our projections of the ecological consequences of climate change.

In response to the continuous variation of environmental parameters, species must be able to adjust their physiology to overcome stressful conditions, a process known as acclimatization. Numerous laboratory studies have been conducted to understand and describe the mechanisms of acclimation to one environmental stressor (e.g. cyclic hypoxia), but currently our understanding of how acclimation to one stressor can change tolerance to a subsequent stressor is limited. Here, in two different experiments, we used the shrimp Palaemon varians to test how, following 28-days acclimation to cyclic hypoxia (mimicking a cyclic hypoxic regime currently found in its natural habitat), critical thermal maximum (CT max) and sensitivity to copper (Cu 2+) exposure (30 mgL −1) changed in comparison to shrimp acclimated to normoxic conditions and then exposed to thermal stress or Cu 2+. Acclimation to cyclic hypoxia improved both CT max (~1 °C higher than controls) and survival to acute Cu 2+ exposure (~30% higher than controls) and induced significant gene expression changes (i.e. up-regulation of heat shock protein 70 – HSP70, hypoxia inducible factor – HIF, phosphoenolpyruvate carboxykinase – PEPCK, glucose 6-P transporter – G6Pt, metallothionein – Mt, and down-regulation of hemocyanin – Hem) in animals acclimated to cyclic hypoxia. Our results demonstrate how acclimation to cyclic hypoxia improved tolerance to subsequent stressors, highlighting the complexity of predicting organismal performance in variable (i.e. where multiple parameters can simultaneously change during the day) environments.

About 400 subglacial lakes are known from Antarctica. The question of whether life unique of subglacial lakes exists has been paramount since their discovery. Despite frequent evidence of microbial life mostly from accretion ice, subglacial lakes are characterized by physiologically hostile conditions to metazoan life, as we know it. Pure water (salinity ≤0.4–1.2%), extreme cold (−3°C), high hydrostatic pressure, areas of limited or no oxygen availability and permanent darkness altogether require physiological adaptations to these harsh conditions. The record of gene sequences including some associated with hydrothermal vents does foster the idea of metazoan life in Lake Vostok. Here, we synthesize the physico-chemical environment surrounding sub-glacial lakes and potential sites of hydrothermal activity and advocate that the physico-chemical stability found at these sites may be the most likely sites for metazoan life to exist. The unique conditions presented by Lake Vostok may also offer an outlook on life to be expected in extra-terrestrial subglacial environments, such as on Jupiter's moon Europa or Saturn's moon Enceladus.

The maternal environment may influence the quantity and quality of resources invested in offspring (per-offspring provisioning) and this trait, in turn, affects larval fitness and may carry-over into early juvenile life. Here, per-offspring investment was measured across three consecutive breeding seasons for the caridean shrimp, Palaemon varians. Egg and hatchling larval dry weight as well as hatchling larval biochemical composition were measured. Results indicate that egg volume is positively correlated with dry weight, but egg volume as a proxy for dry weight should be used with caution. Correlations were identified between per-offspring investment and average breeding season temperature, but the period over which temperature was averaged was important to whether these correlations were positive or negative, highlighting the complexity of identifying environmental influence on phenotypic traits. The most important factor determining offspring size and per-offspring investment was maternal size, which may be influenced by the environment as carapace length varied significantly between breeding seasons. These data demonstrate variation in egg and larval composition, related to maternal size, which will affect early life traits and survivorship for P. varians.

Climate warming is altering the distribution of species, producing range shifts and promoting local extinctions. There is an urgent need to understand the underlying mechanisms that influence the persistence of populations across a species' distribution range in the face of global warming. Ocenebra erinaceus is a marine gastropod that exhibits high intraspecific variability in maternal investment and physiological capacity during early stages, which suggests local adaptation to natal environmental conditions. In this study, reproductive traits and trans-generational adaptation were measured in two subtidal populations: one from the middle (the Solent, UK) and another towards the southern end of their geographic distribution (Arcachon, France). Local adaptation was evaluated with a transfer experiment (i.e. Arcachon females transferred to Solent thermal conditions) and trans-generational adaptation was evaluated in the thermal tolerance response of embryos exposed to temperatures between 10 and 20 °C. This study shows that both populations have similar fitness; however, there are adaptive costs to live under their natal location, resulting in trade-offs between reproductive traits. Transferred females show lower reproductive output, which suggests that females are maladapted to live under a new environment. The trans-generational experiment demonstrates contrasting thermal tolerance ranges between populations. Adaptation to local thermal conditions was observed in transferred embryos, showing poor performance and high mortalities under the new environment. Our results provide a better understanding of intraspecific differences and adaptations across a species’ distribution range and provide insights into how climate warming will impact encapsulated species exhibiting location-specific adaptation.

The fauna of decapod crustaceans in the Southern Ocean has historically been considered impoverished, with only about a dozen species of decapod shrimp overall, of which only three species are common and abundant on the Antarctic continental shelf. Crabs and lobsters were assumed to be absent or very rare in the Southern Ocean, mainly ascribed to the physiological constraint of cold polar waters. Polar temperatures have been hypothesized to reduce decapod activity, especially in combination with high magnesium levels in the hemolymph ([Mg2+]HL), as [Mg2+] has a relaxant effect. Mg2+ is abundant in seawater and in combination with polar temperatures causes a relaxant effect in Crustacea (Frederich et al. 2001). Because most crabs are capable of regulating [Mg2+]HL only slightly below the [Mg2+] of seawater, their ability to maintain activity should be hampered (Frederich et al. 2001, Aronson et al. 2015a). In contrast, caridean shrimp regulate [Mg2+]HL to very low levels. The combined effect of low temperatures and high [Mg2+]HL might explain the limits of cold tolerance in decapods and has been put forward as the principal reason for the absence of crabs and lobsters from the high‐polar regions (Frederich et al. 2001, Aronson et al. 2015a). These large, benthic, shell‐crushing decapods, along with shell‐crushing teleosts and elasmobranchs, are important in structuring benthic communities at lower latitudes.

espanolLas hipotesis filogeneticas para los peracaridos del orden Cumacea son escasas y no han proporcionado una solucion definitiva. En el presente estudio se utilizo un fragmento del rDNA 16S mitocondrial para formular una hipotesis filogenetica para tres familias de cumaceos, Diastylidae, Bodotriidae y Leuconidae. Ademas se han analizado las relaciones intrafamiliares de esta ultima. Los cumaceos es un grupo monofiletico con tanaidaceos e isopodos como taxones externos. De las tres familias analizadas, los Diastylidae fueron la unica con buen apoyo para la monofilia. El genero Leucon se resol- vio parafiletico mientras que el subgenero Crymoleucon fue monofiletico. Ademas, se analizo la estructura genetica de dos especies de leuconidos Leucon antarcticus Zimmer, 1907 y L. intermedius Muhlenhardt-Siegel, 1996 del mar de Weddell y el mar de Ross respectivamente. Ambas especies mostraron diferentes patrones de variabilidad genetica intraespecifica. A diferencia de L. intermedius, para L. antarcticus se observo una distribucion bimodal del mismatch distribution, que se corre- laciona con las distribuciones geograficas y de profundidad entre el mar de Ross y el mar de Weddell. Aunque una evaluacion clara de la especiacion criptica en estas especies requiere trabajo adicional con mas especimenes de mas regiones geograficas y rangos de profundidad mas amplios, las diferencias que se muestran en las secuencias del rDNA 16S solo pueden explicarse por la separacion genetica de poblaciones entre el mar de Weddell y el mar de Ross durante un periodo de tiempo prolongado. EnglishPhylogenetic hypotheses for the peracarid order Cumacea are scarce and have not provided a solution to the full extent. In the present study, a fragment of the mitochondrial 16S rDNA was used to erect a phylogenetic hypothesis for three cumacean families, Diastylidae, Bodotriidae and Leuconidae, along with intra-family relationships of the latter. The Cumacea resolved monophyletic with tanaids and isopods as outgroup taxa. The Diastylidae were the only family with good support for monophyly. The genus Leucon resolved paraphyletic, whereas the subgenus Crymoleucon was monophyletic. Furthermore, the genetic structure was analysed for two leuconid species, Leucon antarcticus Zimmer, 1907 and L. intermedius Muhlenhardt-Siegel, 1996, from the Weddell Sea and the Ross Sea. The two species showed different patterns of intraspecific genetic variability. In contrast to L. intermedius, a bimodal distribution of pairwise genetic distances was observed for L. antarcticus, which is correlated with geographical and depth distributions between the Ross Sea and the Weddell Sea. Although a clear evaluation of cryptic speciation in these species requires additional work on more specimens from more geographic regions and broader depth ranges, differences shown in the sequences of 16S rDNA can only be explained by genetic separation of populations between the Weddell Sea and the Ross Sea for an extended period of time

Experimental approaches to assess whether shallow-water benthic invertebrates can extend bathymetric ranges in response to changing climate have focused on the developing ecophysiological model Palaemon varians . However, P. varians may not be representative of other shallow-water shrimp species: this species inhabits the highly variable salt marsh environment and is eurythermal, euryhaline, and euryoxic. Inferences concerning the capacity of an ancestral species to directly colonise the deep sea have therefore been regarded with caution. We provide evidence that acute thermal and hyperbaric tolerance in the intertidal and subtidal shrimp Palaemon serratus are lower than in the salt marsh and brackish-water shrimp P. varians, suggesting that adaptation to differing habitats has resulted in differing physiological tolerance to acute stress conditions. Nonetheless, hyperbaric tolerance in P. serratus supports the proposition that the common ancestor of these species may have possessed the physiological capability to colonise bathyal depths. The consistent interaction between temperature and hydrostatic pressure tolerance in these species supports the suggestion that shallow-water species may have the capacity to deepen bathymetric distribution in response to ocean warming.

An unusually high proportion of Antarctic echinoderms brood their young. Protection, reproductive constraints, low temperatures and limited food supply are all suggested motives for this reproductive pattern. This study looks at the reproductive energetics of the Antarctic asteroid Rhopiella hirsuta, and to establish the dynamics of feeding and elemental composition throughout its early juvenile development. Brooding females were analysed in terms of adult size, brood size and juvenile size with non-significant trends occurring with depth. Four brooding females were frozen straight after sampling and enabled the study of changes in elemental composition throughout embryo and early juvenile development with regard to their feeding mode. Morphological and elemental analyses indicate aseasonality of reproduction and lecithotrophic early ontogeny in this species. The most advanced juveniles found were significantly different from all earlier stages, with an increase in dry weight (DW) to 5.87 (± 1.08) mg suggesting growth, but a high C:N ratio of 8.60 (± 0.59) that would indicate lecithotrophy. However, as the increase in DW was attributed to an increase in carbon, but not to an increase in nitrogen, it was not possible for the food source to be of organic origin.

Environmental temperature plays an important role in shaping the distribution and abundance of marine ectothermic organisms. As a general rule, larvae and juveniles are more sensitive to thermal stress than adults and, as a consequence, represent key life stages that determine in part the geographic range of a species. Identifying critical thermal limits during ontogeny allows for the prediction of the potential impacts of climate warming on the distribution of marine ectotherms. However, thermal tolerance - and therefore the potential to meet the challenge of warming- is known to vary at population scale for many species. In order to fully appreciate a species' future under climate warming, multiple populations studies from different thermal environments are necessary. In this study, we compared the thermal tolerance response during the intracapsular development of the marine gastropod Ocenebra erinaceus between two geographically separated populations: one from the middle (Solent, UK) and another from the south of the species' geographic range (Arcachon, France). The results show that the thermal tolerance response was influenced by geographic origin. Embryos from the relatively warm-water southern population (France) show a warm-eurythermal tolerance window with optimal temperatures between 12 and 18 °C. On the contrary, embryos from the cold-water northern population (UK) exhibit a narrow, warm-stenothermal, thermal tolerance window with optimal temperatures between 14 and 16 °C. In both populations, temperatures outside of the thermal range cause lethal and sub-lethal effects. Importantly, previously observed dispersal polymorphism was not observed at hatching time in either population in our study. Our study demonstrates that during early developmental stages, embryos are adapted to local thermal conditions and that they live very close to their upper thermal limits. Temperatures outside this range cause detrimental and contrasting effects on embryonic development of O. erinaceus , implying that the effects of future warming will depend on the population response to local environmental history. Our results suggest that global warming could shift the geographical distribution range of O. erinaceus poleward.

Benthic assemblages of the Antarctic continental shelf are dominated by sessile and slow-moving, epifaunal invertebrates. This community structure persists because shell-crushing (durophagous) predators are absent or ecologically insignificant in shelf habitats. Durophagous teleosts, elasmobranchs, and crustaceans have been excluded by cold waters over the Antarctic shelf for millions of years. Now, as shallow waters warm rapidly, predatory king crabs (Lithodidae) living in the upper bathyal zone could emerge onto the shelf and into nearshore habitats. To assess the potential for a bathymetric expansion, we genetically inferred the historical demography of a population of the most abundant durophagous predator found in deep water off the western Antarctic Peninsula: the lithodid Paralomis birsteini Macpherson. Analysis of mitochondrial DNA sequences from crabs sampled at 1200–1400 m depth on the slope off Marguerite Bay suggests this population has expanded twice over the past 132,000 years. Those expansions were possibly coincident with episodes of climatic warming in Antarctica and elsewhere, raising the possibility of a third expansion in response to anthropogenic climate change.

Data are presented on growth in early juvenile (N = 36; 2.05–3.95 mm carapace length) Lithodes maja Linnaeus, 1758 reared at 6 °C in the laboratory, and on growth in males (N = 24; 45.9–113.3 mm carapace length) and females (N = 9; 61.0–81.3 mm carapace length) maintained at 6 °C in the laboratory. Growth rate did not differ significantly among early juvenile, males, or females, and therefore appeared linear across the size range examined. Intermoult period increased with increasing size. Growth and intermoult period models were combined to estimate size at age. Age at maturity appears greater in L. maja than in other species of Lithodes, suggesting that L. maja may be more vulnerable to fisheries overexploitation.

Global temperatures are rapidly changing, causing shifts in both biotic and abiotic environments. In the short term, physiological plasticity is likely to play an important role in the survival of species. We studied the association between temperature and reproductive investment in the common whelk Buccinum undatum, a North Atlantic gastropod exhibiting non-pelagic development. We calculated the number of eggs per capsule volume and egg energetic status (Carbon: Nitrogen (C: N) ratio) for egg masses from a temperate population of whelks from the Solent, UK over a four-year period (2009–2013). Data were compared with egg masses from a sub-Arctic population from Iceland collected in 2011. Results were compared to local seasonal water temperatures to examine the association between temperature and reproductive investment. In the Solent, average winter temperatures increased significantly between 2009 and 2013, the winter increase being significant. Both the number of eggs per capsule volume and the C:N ratio of eggs increased significantly between the initial and final spawning years. The number of eggs per capsule volume was significantly lower in eggs collected in Iceland, but C:N ratio was significantly higher. The results indicate that shifts in reproductive investment in B. undatum are associated with environmental temperature. B. undatum appears to show a high level of physiological plasticity in reproduction which may, in the short term, facilitate species survival as annual temperature shifts become more variable.

Extant deep-sea fauna, including hydrothermal vent endemics such as bresiliid shrimp, are descended from shallow-water ancestors. Previous studies have demonstrated the capacity of shallow-water shrimp to acclimate to hydrostatic pressure representative of the vent environment. It has been proposed that this hyperbaric acclimation depends in part on shifts in phospholipid fatty acid composition to maintain biomembrane function. These shifts are also predicted to reduce critical temperature tolerance, potentially limiting the possibility of direct colonisation of the hydrothermal vent environment. Here, we present evidence that acclimation to high hydrostatic pressure (10 MPa ≈ 1000 m water depth) decreases acute temperature tolerance from 30.2 °C to 27.1 °C in the shallow-water shrimp Palaemon varians acclimated to 10 °C. Statistically significant shifts in phospholipid fatty acid composition occurred during exposure to high hydrostatic pressure, suggesting that homeoviscous modifications support shifts in environmental tolerances during hyperbaric acclimation. Despite the reduction in temperature tolerance, P. varians retains sufficient thermal scope to tolerate the thermal regime in the hydrothermal vent environment, allowing for the possibility of direct deep-sea hydrothermal vent colonisation by shallow-water shrimp.

Polymetallic seafloor massive sulphide deposits are potential targets for deep-sea mining, but high concentrations of metals (including copper - Cu) may be released during exploitation activities, potentially inducing harmful impact. To determine whether shallow-water shrimp are suitable ecotoxicological proxies for deep-sea hydrothermal vent shrimp the effects of waterborne Cu exposure (3 and 10 days at 0.4 and 4 μM concentrations) in Palaemon elegans, Palaemon serratus, and Palaemon varians were compared with Mirocaris fortunata. Accumulation of Cu and a set of biomarkers were analysed. Results show different responses among congeneric species indicating that it is not appropriate to use shallow-water shrimps as ecotoxicological proxies for deep-water shrimps. During the evolutionary history of these species they were likely subject to different chemical environments which may have induced different molecular/biochemical adaptations/tolerances. Results highlight the importance of analysing effects of deep-sea mining in situ and in local species to adequately assess ecotoxicological effects under natural environmental conditions. This work was developed under the MIDAS project (Managing im-pacts of deep-sea resource exploitation), funded by the EuropeanCommission, European Union, 7th Framework Programme under thetheme“Sustainable management of Europe's deep sea and sub-seafloorresources”(Grant Agreement 603418). This work was also supported bythe Fundação para a Ciência e Tecnologia I.P. Portugal (FCT) and theDireção-Geral de Política do Mar (DGPM), Portugal through the projectMining2/2017/001–MiningImpact 2 (JPI Oceans), and FCT furtherfunded the grants CEECIND005262017 and UID/MAR/00350/2013.We acknowledge the captains and crews of the oceanographic ship“Pourquoi Pas?”, and the pilots of Victor 6000 Remotely OperatedVehicle, for their dedicated assistance during sampling of vent shrimps.We are also grateful to F. Lallier, chief scientist of the Biobaz cruise. Wewould like to warmly thank Océanopolis staffmembers, J-M Carré, SDelaporte and O Gouello, for their important contributions to shrimpmaintenance. info:eu-repo/semantics/publishedVersion

Owing to the influence of the Humboldt Current many cold-water adapted brachyuran crabs of commercial interest have vast (>40°latitude) distributional ranges along the Pacific Coasts of Peru and Chile. Development of artisanal diving and trapping fisheries on these crabs (mainly Cancridae and Xanthidae) is either uncontrolled (Peru) or existing management measures, like the minimum landing size of 12 cm carapace width, and the prohibition to catch ovigerous females, are poorly enforced (Chile). Under El Nino conditions, occurring on average every 4 years, the upper temperature limit of these temperate species can be exceeded in Peru, leading to mass mortalities of adult crabs and a breakdown of the artisanal crab fishery. Temperature changes (latitudinal or in the course of El Nino Southern Oscillation) may have pervasive effects on reproduction and early life history stages as represented for Romaleon setosus, which ultimately determine the recruitment of crabs to the fishery. The recent development of the fishery, namely the decline of the landings of Romaleon setosus and Homalaspis plana in Central- to Northern Chile, compensated by the rapidly developing fishery on Metacarcinus edwardsii in Southern Chile is presented and discussed in the light of temperature effects on the crabs’ (reproductive) biology. We conclude that an enforcement of the legal minimum size is needed to allow for a sustainable fishery of both species throughout their distribution range.

Some extant deep-sea shrimp are known to be descended from shallow-water ancestors that adapted to environmental conditions (constant low temperature and high hydrostatic pressure) in the deep sea. During acclimation to low temperature and high hydrostatic pressure representative of the deep-sea, critical thermal tolerance decreases and critical pressure tolerance increases in the shallow-water shrimp Palaemon varians. It has been suggested that these shifts may depend in part on adjustments to phospholipid fatty acid composition and/or metabolic adjustments. Here, we present evidence that metabolic rate does not change during sustained exposure to low temperature (5 °C) in the shallow-water shrimp Palaemon varians, and that metabolic rate and acute environmental tolerances are not correlated during sustained exposure to low temperature, suggesting that standard metabolic rate does not affect acute environmental tolerances. In contrast, we present evidence that phospholipid fatty acid composition does shift during sustained exposure to low temperature. Desaturation of fatty acids during sustained exposure to low temperature supports the suggestion that cell lipid bilayer homeoviscous modifications are important in low temperature acclimation. Shifts in several individual phospholipid fatty acids during sustained low temperature exposure are correlated with critical thermal tolerance. Exploring the greater complexity apparent in the responses of these phospholipid fatty acids to sustained low temperature exposures suggests a potential homeostatic impact moderating adverse impacts on nervous system function. However, shifts in phospholipid fatty acids are not correlated with critical pressure tolerance during exposure to low temperature, suggesting that shifts in critical pressure tolerance are related to modifications other than cell lipid bilayer composition.

Climate warming can affect the developmental rate and embryonic survival of ectothermic species. However, it is largely unknown if the embryos of populations from different thermal regimes will respond differently to increased warming, potentially due to adaptations to natal environmental conditions. The effects of temperature on respiration rates and oxygen content of the intracapsular fluid were studied during the intracapsular development of Ocenebra erinaceus in two subtidal populations, one from the middle of their geographic distribution, the Solent, UK and another towards the southern portion: Arcachon, France. In this laboratory study, embryos were exposed to temperatures in the range of 14–20 °C. The encapsulation period for both populations was shorter at higher temperatures and intracapsular oxygen availability decreased as development progressed. However, the embryonic aerobic response differed between populations. Encapsulated embryos from the southern population (Arcachon) showed higher respiration rates and metabolic adjustment to elevated temperatures; however, encapsulated embryos from the Solent showed no metabolic adjustment, high capsular mortalities and limited acclimation to high temperatures. Our results suggest that aerobic response of encapsulated embryos is locally adapted to the temperature history of their natal environment and illustrates the importance of local environmental history in determining the fate of key life stages in response to a changing marine climate.

Adaptations in per-offspring investment and larval development are considered to have been crucial to the global radiation of deep-water lineages of lithodine crabs (Lithodinae). Temperature is proposed to drive latitudinal trends in energy provisioning of eggs in marine invertebrates, mediated by thermally dependent intraspecific plasticity in per-offspring investment. Consequently, a changing climate may be expected to directly affect larval provisioning. We analysed available data to examine any differences in per-offspring investment and larval development among deep-water lineage lithodines. Although data are few, interspecific differences in the thermal scope of deep-water-lineage lithodine larvae appear coupled with differences in biogeography. This coupling suggests environmental temperature influences larval thermal scope. Lithodine phylogeography suggests that larval cold-eurythermy in deep-water-lineage lithodines is a derived trait that has evolved in relatively warm and variable subantarctic shallow water. Therefore, we hypothesise that capacity to adapt to warmer and more variable environmental conditions may afford deep-water-lineage lithodines some resilience to ocean warming, depending on the rates of environmental and adaptive change. Interspecific comparisons also suggest that larval duration and per-offspring investment are positively correlated. Faster development at a given temperature is associated with higher respiration rates and greater energetic reserve utilisation. Therefore, we hypothesise that selection pressure for contrasting metabolic adaptations in different thermal environments contributes to shifts in larval duration and per-offspring investment.

Physiological adaptations enabling tolerance of low temperature, as well as adaptations in larval development, are thought to be critical to the global radiation of deep-water lineages of lithodine crabs. However, global climate change is warming the oceans, potentially impacting the biogeographic distributions of these large predatory crabs. To date, larval thermal scope has only been explored in a few deep-water lineage lithodines. We assessed larval development parameters in the northern stone crab Lithodes maja at temperatures ranging from 1 °C to 15 °C. We examined larval survival, duration of development, energetic reserve utilisation, and respiration rate. L. maja larvae displayed a narrow thermal tolerance window and metamorphosed successfully at 6 °C only. Differential uses of energetic reserves among temperatures during development in L. maja support the interpretation of a narrow larval thermal scope and indicate that 6 °C is the optimum temperature for development in this species. Consequently, continued ocean warming is likely to force biogeographic range shifts in L. maja.

Salt marshes are a key coastal environment for their important role as nursery habitats for marine and estuarine fish and crustaceans. Salt marshes are variable environments where species can experience daily cyclic hypoxic stress, characterised by profound variations in oxygen partial pressure (pO₂) from supersaturated conditions (~42 kPa) to extremely hypoxic conditions (~3 kPa) in ~12‐hr. Here, under laboratory conditions, we assessed the physiological consequences of exposing the shrimp Palaemon varians, a species commonly found in the salt marshes of northern Europe, to the daily cyclic hypoxic regime currently experienced in its habitat in August (7.1 ± 1.8 hr/day below 4.0 kPa). In the laboratory, adults were kept at water pO₂

Different physiological thresholds of species across biogeographic boundaries can show a long-term scope for adaptation. Characterised by cold-stenothermal conditions, polar and deep-sea environments are constrained by thermal stability across wide regions, and polar invertebrates are broadly considered to be highly sensitive to only subtle changes in thermal regime. We examine the respiratory response of two distinct biogeographic populations of the widespread bivalve Lissarca notorcadensis from deep waters in the Southern Ocean to acute thermal changes, and present distinct respiratory responses for each population. Populations from the Weddell Sea living in cooler water temperatures (

The Antarctic fish fauna from outer continental shelf/upper slope depths is under-sampled compared to that of the inner shelf, and there are limited quantitative data available on absolute abundance and taxonomic change with depth. A photographic survey of demersal fishes was conducted along a depth-gradient of 400–2099 m on the outer shelf and upper slope west of Anvers Island, Palmer Archipelago. A total of 1490 fishes were identified at least to the family level. Notothenioids composed 52.7% of absolute abundance and non-notothenioids 47.3%. The most abundant families were Nototheniidae (39.4%), followed by Macrouridae (28.9%), Zoarcidae (16.9%), and Channichthyidae (12.1%). The most abundant species were the notothenioidsLepidonotothen squamifrons(30.5%) andChionobathyscus dewitti(11.7%), and the non-notothenioidMacrourusspp. (29.5%). The absolute abundance of all fishes peaked at 400–599 m. Depths of maximum abundance were 400–599 m forL. squamifrons, 700–1499 m forMacrourusspp., and 900–1499 forC. dewitti. At 700–999 m the abundance shifted from primarily notothenioids to the non-notothenioidsMacrourusspp. and zoarcids. Fishes of the outer shelf and upper slope are not provincialized like those of the inner shelf and are circum-Antarctic.

Intraspecific polymorphism during development, such as poecilogony or dispersal polymorphism, has rarely been observed in the marine environment. The ecological advantages of this bet-hedging strategy, whereby the offspring from one species exhibit multiple developmental modes, include the potential for rapid colonization of new habitats while simultaneously achieving a degree of gene flow between populations. The muricid gastropod, Ocenebra erinaceus, is a common, shallow-water marine predator found across England and France. Historically, O. erinaceus caused significant damage to shellfisheries, but more recently it has been impacted by TBT-induced imposex. Despite the previous attention given to this species, little is known about its encapsulated development. Studying O. erinaceus egg capsules from the Solent, UK, we describe intracapsular development at 15 °C, the in situ temperature at time of oviposition. Within each capsule, all embryos developed; no nurse eggs were present. Development was categorized into eight ontogenetic stages, although not all individuals displayed every stage; embryos hatched as either swimming late-pediveliger larvae or crawling juveniles after 59–69 days, indicating dispersal polymorphism to occur in this species. Swimming late-pediveliger larvae completed metamorphosis within 72 h of hatching. As O. erinaceus continues to recover from TBT pollution, dispersal polymorphism may facilitate a rapid expansion in both population size and range. If this occurs, O. erinaceus has the potential to, once again, become a serious problem for shellfisheries around Europe.