2018 年 13 巻 4 号 p. 163-172
The freshwater calanoid copepod Mongolodiaptomus malaindosinensis is an endemic species of the lower Mekong basin, including Malaysia. The relationships between environmental factors and life history traits have been reported for many copepods, while they have never been assessed in this tropical species. Post-embryonic development time (post-EDT), body size and survival rate of M. malaindosinensis were determined under different algal concentrations of Chlamydomonas reinhardtii and Cryptomonas tetrapyrenoidosa at 25°C, to clarify the effects of algal species and carbon supply on their somatic growth and survival. Post-EDT until adult in M. malaindosinensis decreased with increasing food carbon supply regardless of the algal species tested. Although naupliar developments were the shortest at 104 cells mL−1 of C. reinhardtii, food shortage delayed the development time and also induced high mortality during the copepodid stages. The highest survival rate of 93% was obtained in the copepods fed on C. tetrapyrenoidosa at 5×104 cells mL−1, whereas the survival rates in the remaining lower carbon supply were <23%. The most sensitive stages were the 1st copepodid stage, as indicated by high stage-specific mortalities, because of large morphological and physiological changes in this transitional stage. Prosome length of adult M. malaindosinensis positively correlated with food carbon supplies, though females were larger than males. Somatic growth rate exponentially increased with increasing food carbon supplies with a threshold at around 4.0 mgC L−1. These results suggest that tropical copepods may be adapted to higher food quantities due to their high metabolic rates under high temperature conditions.
