Invasive versus native brachyuran crabs in a European rocky intertidal: respiratory performance and energy expenditures

Abstract

The invasive Asian shore crab Hemigrapsus sanguineus is now the second most abundant intertidal crab in the North Sea after the native European green crab Carcinus maenas. To compare their respiratory performance and energy expenditures, we measured standard respiration rates of both species from around the island of Helgoland, North Sea, Germany (54°11′N, 7°53′E) in 2015. Oxygen consumption was recorded in a flow-through setup between 5 and 20 °C. At lower temperatures, H. sanguineus had similar respiration rates as C. maenas, but approximately twofold higher rates at higher temperatures. Numerical models for the calculation of individual respiration rates were established and applied to the entire intertidal populations around Helgoland to compare the energy expenditures of both species. Abundance and biomass data recorded in August 2014 showed that H. sanguineus reached values as high as 21 and 59%, respectively, compared to those of C. maenas. Based on these data and the numerical respiration models, the energy expenditures of both populations were calculated for the whole year 2014. The H. sanguineus population reached, depending on the assumed diet of both species (complete herbivory versus complete carnivory), 86-135% of the expenditure value of C. maenas. As population densities of H. sanguineus are likely to increase in the North Sea, the energy expenditure of the invader and thus its impact on the energy flux in the intertidal habitat will further increase. Whether this will lead to an impact on the local intertidal community depends on species-specific dietary preferences and remains to be investigated.

Life History and Population Dynamics of Green Crabs (<em>Carcinus maenas</em>)

“…Under conditions of declining oxygen tension, the degree of respiratory independence shown by C. maenas is dependent on the animal's level of activity and inactive animals can maintain respiratory independence down to a PO2 of 60-80 mmHg [170]. Both male and female adult crabs from Helgoland, Germany, increased their respiration with increases in temperature as expected for an ectothermic animal, but had relatively low Q10 values, suggesting that C. maenas has a capacity to stabilize its metabolic rate under physically diverse habitats [171]. Large numbers of crabs move into the intertidal to forage during high tide [2,118,167] and some remain in the intertidal during low tide [2] so can experience hypoxia.…”

“…The brush-clawed shore crab, Hemigrapsus takanoi, was unintentionally introduced to the Netherlands in the late 1990's and is now abundant in the Eastern Scheldt, where adults compete with juvenile C. maenas [289]. A sibling species, the Asian shore crab, H. sanguineus, is also found in European waters, having arrived by 2003 in the Mediterranean Sea [290], around 2007 on the coast of France [291] and then Helgoland, Germany, where it is now the second most abundant intertidal crab in the North Sea after C. maenas [171]. It is predicted that the Asian shore crab will assert competitive dominance over the green crab in this region [171].…”

PopulationDynamics of Green Crabs (Carcinus maenas) -- A Review

“…Under conditions of declining oxygen tension, the degree of respiratory independence shown by C. maenas is dependent on the animal's level of activity and inactive animals can maintain respiratory independence down to a PO2 of 60-80 mmHg [131]. Both male and female adult crabs from Helgoland, Germany, increased their respiration with increases in temperature as expected for an ectothermic animal, but had relatively low Q10 values, suggesting that C. maenas has a capacity to stabilize its metabolic rate under physically diverse habitats [132]. Large numbers of crabs move into the intertidal to forage during high tide [1,81,117] and some remain in the intertidal during low tide [81] so can experience hypoxia.…”

“…in the Mediterranean Sea [217], around 2007 on the coast of France [218] and then Helgoland, Germany, where it is now the second most abundant intertidal crab in the North Sea after C. maenas [132]. It is predicted that the Asian shore crab will assert competitive dominance over the green crab in this region [132].…”

“…It is predicted that the Asian shore crab will assert competitive dominance over the green crab in this region [132].…”