Decreased calcium concentration interferes with life history defense strategies of Ceriodaphnia cornuta in response to fish kairomone

Abstract

Declining calcium in freshwater lakes has become a serious threat to aquatic organisms, which may affect the anti‐fish defense of cladocerans with high calcium demand. To evaluate the effects of low calcium on life history strategies of cladocerans for defending against fish predation, we exposed Ceriodaphnia cornuta to eight concentrations of calcium ranging from 0.5 to 50.0 mg L−1 in the absence and presence of fish kairomone, and observed the changes in body surface, recorded the key life‐history traits, and calculated the degree of its induced defense response. Results showed that, on average, low calcium (0.5, 1.0, 1.5 mg L−1) significantly reduced survival, maternal body size at maturation, and total offspring per female by 66.7%, 8.0%, and 48.8%, respectively, compared with those exposed to normal calcium level (10.0 mg L−1). At the normal calcium level, fish kairomone shortened the time to maturation, reduced maternal body size at maturation, and increased total offspring by 15.7%, 11.0%, and 29.6%, respectively, compared with those not exposed to fish kairomone. In the presence of fish kairomone, the reproduction of C. cornuta was affected by a narrower range of calcium concentrations. Calcium concentrations and fish kairomone showed a significant interaction on maternal body size at maturation, total offspring, and body size of neonates, i.e., low calcium impaired the life history defenses involved in maternal development, but enhanced the defense traits involved in reproductive performance, which indicated the diversified interference effects of decreased calcium on the life history defense strategies of C. cornuta against fish predators.

Impact of atrazine on the dynamic response of Daphnia pulex populations to fish predation risk

“…Our results showed that the high concentration of atrazine caused the decrease of individual dry weight of D. pulex, but as the concentration selected in this experiment was limited, thus the critical concentration of atrazine that causes the reduction of individual dry weight cannot be obtained. Previous studies concluded that fish predation kairomone attenuates the adverse effects of environmental stressors on the growth and reproduction of cladocerans (Robison et al, 2018;Gu et al, 2020b;Huang et al, 2021), and the results of our experiment demonstrated for the first time that the fish predation kairomone attenuated the negative effects of atrazine on several population traits. These results indicated that fish kairomone can alleviate the stress ability of cladocerans.…”

Induced anti-predation defense traits of Daphnia are associated with the gut microbiota composition

“…Speci cally, we used two predictive functions to t the data. An exponential rise to an asymptote function, y = J max (1-e -pt ), was used to t the relationships between D. magna body size and growth days at presence or absence of sh kairomone, where y is body size of D. magna at time t, J max is the predicted asymptotes of the exponential rise functions (maximum value) when t approaches in nity, and p describes the initial rate of change in the response [45]. An exponential decline to an asymptote function, y = L min + αe -rt , was used to t the relationships between spine length / body size of D. magna and growth days at presence or absence of sh kairomone, where y is spine length / body size of D. magna at time t, L min is the predicted asymptotes of the exponential decline functions (minimum value) when t approaches in nity, and r describes the initial rate of change in the response [48].…”

“…We set up the experiments in the absence (control) and presence (treatment) of sh kairomone. The stocked sh kairomone was diluted 20 times in the COMBO medium to produce the target concentration (one sh per 10 L), as detailedly described in Huang et al [45]. Each treatment or control contained 250 replicates, and each replicate containing one individual was cultured in 50 mL of the COMBO medium with the green alga S. obliquus as food (1.5 mg C L −1 ).…”

Novel Near-Infrared-II In Vivo Visualization Revealed Rapid Calcium Intestine Turnover in Daphnia magna with Delayed Impact by Cadmium and Acidification

“…Calcium (Ca) uptake and cycling are critical for freshwater organisms. 1 Bone and shell formation in freshwater organisms rely on Ca absorption and cycling. 2 The uptake and cycling of Ca ensure the maintenance of appropriate cellular Ca 2+ concentrations, thereby supporting normal metabolic reactions.…”

“…Numerous evidence suggested that D. magna was highly sensitive to low Ca concentrations, and field studies demonstrated reduced population growth in zooplankton species under such conditions 52. Laboratory studies further revealed that low-Ca environments led to diminished body size, survival rate, and reproductive capabilities in D. magna 1,53,54. However, previous studies predominantly focused on the end point of accumulation deficiency effects of Ca in the body, while investigations into the kinetics of Ca passage through the intestine were limited 10,13,55.…”