Atyaephyra desmarestii (Millet, 1831)

Ravaux, Juliette, Bosc, Olivia, Fusari, Charles-Edouard, Gricourt, Sara-Mae, Itin, Maria, Lestin, Michel & de Mazancourt, Valentin, 2025, Thermal tolerance and vulnerability to climate warming in the freshwater shrimp Atyaephyra desmarestii and Caridina multidentata, Journal of Thermal Biology 129, pp. 104121-104121 : 5-9

3.1. Thermal tolerance and acclimation capacity assessment of two populations of Atyaephyra desmarestii

The CTMax values for A. desmarestii originating from Spain were 33.2 ◦ C (acclimation at 18 ◦ C), 35.0 ◦ C (acclimation at 23 ◦ C), and 37.3 ◦ C (acclimation at 28 ◦ C), corresponding to a 2 ◦ C increase in CTMax for each 5 ◦ C increase in acclimation temperature ( Fig. 2 ). The calculated thermal safety margin is 15 ◦ C (acclimation at 18 ◦ C), 12 ◦ C (acclimation at 23 ◦ C), and 9 ◦ C (acclimation at 28 ◦ C).

The CTMax value for A. desmarestii originating from France was 34.7 ◦ C (acclimation at 23 ◦ C), giving a summer thermal safety margin of 12 ◦ C ( Fig. 2 ).

4.2. Thermal limit variation with latitude: the case of Atyaephyra desmarestii

Here we compare the CTMax of two populations of A. desmarestii more than 900 km apart, corresponding to 6 ◦ on a latitudinal axis: the southern population of Spain and the northern population of the Paris region ( Fig. 2 ). The expected variation in CTMax should be around 1 ◦ C for these populations (about 0.17 ◦ C per degree of latitude; Sunday et al., 2019), yet the CTMax values obtained were equivalent, all other things being equal: acclimation at the same temperature, identical maintenance and experimental conditions. These data suggest that this species’ upper thermal limit would not shift as a function of the geographic zone, meaning that the thermal tolerance would not adjust to the thermal conditions of its habitat at the scale of its geographical distribution. And yet, the populations from Spain and from France are subject to clearly different thermal conditions in their environment, particularly with regard to extreme summer temperatures. A broad correspondence has been shown between thermal limits and extreme environmental temperatures, suggesting that latitudinal patterns of thermal tolerance can be largely explained by the extreme temperatures encountered in each environment ( Sunday et al., 2019). Temperature recorded in summer ranged from 19 to 31 ◦ C on the Spanish site ( Arbat-Bofill, 2015), and from 19 to 23 ◦ C on the French site (measurement in the Seine over 26 years for the 20th century; Rivi`ere et al., 2021). The data of the Seine do, however, show a warming of the water temperature, which sometimes reaches 27 ◦ C and more rarely exceeds 27 ◦ C. High summer temperatures for the French population therefore remain several degrees below those of the Spanish population. Moreover, the French population has settled in the Seine since at least 1843 (No¨ el, 2017), so it’ s a long-established colonization that has given this population ample time to adapt to the climatic conditions of this habitat.

These preliminary results pave the way for further study of this species to determine the seasonal thermal limits of populations over its geographical range, in order to test the relationship between geographical distribution and thermal tolerance. This would involve comparing populations at the north-south limits of the species’ range, where differences in habitat temperature are most marked, to confirm whether the latitudinal migration leads to a shift in the thermal tolerance. Experimental translocations of shrimp populations could also provide information on the kinetics and range of species’ acclimation and ultimately adaptation to a new thermal environment.

Figures

Fig. 2. Critical thermal maximum of two populations of Atyaephyra desmarestii acclimated to different temperatures. Left panel: photograph of an A. desmarestii specimen (photo credits: V. de Mazancourt), and map showing the location of the sampling sites in France (Vitry-sur-Seine) and Spain (Flaça). Right panel: CTMax data are represented as box plots, with whiskers indicating the minimum and maximum, the box delimiting the first quartile and third quartile, and the median and mean identified by an horizontal line (the value for median and mean is equivalent and is shown next to the line). The experiments were conducted on a sample size of n = 9 (Spain, 28 ◦C), n = 10 (Spain, 18 ◦C), and n = 12 (Spain, 23 ◦C and France 23 ◦C) individuals. Values sharing a common letter are not significantly different (p> 0.05). The summer thermal safety margin (dotted lines) is calculated as the difference between the CTMax (mean) and the maximum water temperature (31 ◦C for Spain: Arbat-Bofill, 2015; 27 ◦C for France: Rivi`ere et al., 2021).