Explore the vast range of titles available.

In marine species with complex life cycles, thermal tolerance is usually narrower in larvae than in adults. Hence, range contraction and expansion, as a consequence of climate change, may be enhanced or hampered by among‐population variability in the thermal tolerance of larval stages. We quantified the performance (i.e., survival, development, and growth) of larvae of the shore crab Carcinus maenas at different temperatures (range 9°C to 27°C in steps of 3°C) in populations located towards the limits of the European distribution range (South: Vigo, Spain; North: Bergen and Trondheim, Norway). We hypothesised that, given the geographical distance, larvae from northern populations would show increased tolerance to low temperatures while those from southern populations would show increased tolerance to high temperatures. Such patterns would enhance poleward range expansion and counteract contraction as compared with a scenario where thermal tolerance does not change along the latitudinal gradient. Populations from southern Europe (Spain) showed slightly increased survival at higher temperatures compared to those further north and in invasive North American populations. However, there was little variation in larval tolerance between populations of Northern Spain and Norway: survival and growth rates were low at temperatures 9°C and 27°C. Larvae from the northernmost European populations (Norway) showed significantly shorter duration of development at low temperatures, which might have an adaptive value, contingent on the actual pattern of temperatures experienced during the larval phase. Further range expansions (or contractions) are likely to be driven solely by increasing temperatures unless populations located right at the range limit show increased tolerance to low (or high) temperatures. In larvae of the European shore crab Carcinus maenas, the temperature of highest survival decreased towards higher latitudes among populations distributed along the North European coast. C. maenas is native to Europe, but it is considered a global invader in coastal zones.

At the cellular level, acute temperature changes alter ionic conductances, ion channel kinetics, and the activity of entire neuronal circuits. This can result in severe consequences for neural function, animal behavior and survival. In poikilothermic animals, and particularly in aquatic species whose core temperature equals the surrounding water temperature, neurons experience rather rapid and wide-ranging temperature fluctuations. Recent work on pattern generating neural circuits in the crustacean stomatogastric nervous system have demonstrated that neuronal circuits can exhibit an intrinsic robustness to temperature fluctuations. However, considering the increased warming of the oceans and recurring heatwaves due to climate change, the question arises whether this intrinsic robustness can acclimate to changing environmental conditions, and whether it differs between species and ocean habitats. We address these questions using the pyloric pattern generating circuits in the stomatogastric nervous system of two crab species, Hemigrapsus sanguineus and Carcinus maenas that have seen a worldwide expansion in recent decades. Consistent with their history as invasive species, we find that pyloric activity showed a broad temperature robustness (>30°C). Moreover, the temperature-robust range was dependent on habitat temperature in both species. Warm-acclimating animals shifted the critical temperature at which circuit activity breaks down to higher temperatures. This came at the cost of robustness against cold stimuli in H. sanguineus, but not in C. maenas. Comparing the temperature responses of C. maenas from a cold latitude (the North Sea) to those from a warm latitude (Spain) demonstrated that similar shifts in robustness occurred in natural environments. Our results thus demonstrate that neuronal temperature robustness correlates with, and responds to, environmental temperature conditions, potentially preparing animals for changing ecological conditions and shifting habitats.

We studied the potential of a recently introduced species, the Asian brush-clawed crab ( Hemigrapsus takanoi ), to expand its distribution range further into the Baltic Sea. H. takanoi has been documented in the southwestern Baltic Sea since 2014. The ability to persist and further expand into the Baltic Proper will depend on their potential to sustain all stages of their complex life cycle, including pelagic larvae, under the Baltic Sea's conditions. Range limits may be established by the tolerance to low salinity, which in addition may be affected by water temperature. A key question is whether local populations at the distribution limit (within the Baltic Sea) show increased tolerance to low salinities and hence promote further expansion. We quantified the combined effects of salinity (10–33 PSU) and temperature (15–24 °C) on larval development in four populations of H. takanoi (two from the Baltic and two from the North Sea). We found substantial differences in larval performance between the populations from the Baltic and North Seas. Larvae from the North Sea populations always showed higher survival and faster development compared with those from the Baltic Sea. Only weak evidence of elevated tolerance towards low salinity was found in the larvae from the Baltic Sea populations. In addition, larvae from the population located near the range limit showed very low survival under all tested salinity-temperature combinations and no evidence of increased tolerance to low salinity. There was no apparent genetic differentiation among the studied populations in the mitochondrial cytochrome c oxidase subunit one gene (COI) implying high connectivity among the populations. In conclusion, the weak evidence of low salinity tolerance in Baltic Sea populations, and poor larval performance for the population located near the range limit, coupled with limited genetic differentiation suggest that subsidies are needed for populations to persist near the range limit. Alternatively, ontogenetic migrations would be required to sustain those populations. Monitoring efforts are needed to elucidate the underlaying mechanisms and document potential future range expansions.

We studied the potential of a recently introduced species, the Asian brush-clawed crab (Hemigrapsus takanoi), to expand its distribution range further into the Baltic Sea. H. takanoi has been documented in the southwestern Baltic Sea since 2014. The ability to persist and further expand into the Baltic Proper will depend on their potential to sustain all stages of their complex life cycle, including pelagic larvae, under the Baltic Sea's conditions. Range limits may be established by the tolerance to low salinity, which in addition may be affected by water temperature. A key question is whether local populations at the distribution limit (within the Baltic Sea) show increased tolerance to low salinities and hence promote further expansion. We quantified the combined effects of salinity (10-33 PSU) and temperature (15-24 C-degrees) on larval development in four populations of H. takanoi (two from the Baltic and two from the North Sea). We found substantial differences in larval performance between the populations from the Baltic and North Seas. Larvae from the North Sea populations always showed higher survival and faster development compared with those from the Baltic Sea. Only weak evidence of elevated tolerance towards low salinity was found in the larvae from the Baltic Sea populations. In addition, larvae from the population located near the range limit showed very low survival under all tested salinity-temperature combinations and no evidence of increased tolerance to low salinity. There was no apparent genetic differentiation among the studied populations in the mitochondrial cytochrome c oxidase subunit one gene (COI) implying high connectivity among the populations. In conclusion, the weak evidence of low salinity tolerance in Baltic Sea populations, and poor larval performance for the population located near the range limit, coupled with limited genetic differentiation suggest that subsidies are needed for populations to persist near the range limit. Alternatively, ontogenetic migrations would be required to sustain those populations. Monitoring efforts are needed to elucidate the underlaying mechanisms and document potential future range expansions.