The influence of phosphorus concentration on the population dynamics and resting egg formation of two cladocerans

Abstract

Laboratory experiments were conducted to evaluate the effects of food phosphorus (P) concentrations on the population dynamics, ephippium production, and resting egg formation of two cladocerans, Moina irrasa and Daphnia similoides, fed on Chlorella vulgaris that were cultured in five different P concentrations (0.05, 0.1, 1, 5, and 10 mg/L). The body length at the first pregnancy of M. irrasa and D. similoides significantly increased with higher P concentration, whereas the maturation time significantly decreased. The maximum population density of M. irrasa (mean AE SD, 6220 AE 1129 ind/L) and D. similoides (1816.5 AE 63.5 ind/L) appeared in the 5 and 10 mg P/L groups, respectively. The maximum male density of M. irrasa (150 AE 113.0 ind/L) appeared in the low P concentration of 0.05 mg/L, whereas it was in the higher P concentrations for D. similoides. The maximum cumulative ephippia number of M. irrasa (51/female) and D. similoides (6.2/female) appeared in the 0.05 and 1 mg P/L groups, respectively. The maximum percentage of ephippia containing resting eggs of M. irrasa (69.3%) appeared in the lowest P concentration. The percentage of ephippia containing resting eggs of D. similoides increased gradually with higher P concentration, and the ratio was above 70% in higher P concentrations (5-10 mg P/L). Our results suggest that low P can advance and induce the production of ephippium in two cladocerans and that higher male density promotes the resting egg formation of cladocerans.

Feasibility of planctomycetes as a nutritional or supplementary food source forDaphniaspp

“…Daphnia reproduces asexually under optimal conditions, and the first reproductive event is usually observed around 8-10 days after birth, with new broods being produced every 3-4 days (Ebert, 2005). Daphnia are commonly reared in the laboratory using unialgal cultures as a single food source (e.g., Antunes et al, 2004;Bukovinszky et al, 2012;Meng et al, 2014). Because they are fed with a single carbon source, culture performance becomes excessively dependent on the food source (microalga), which sometimes leads to fluctuations in survivability and reproductive output and occasional culture crashes (Baird et al, 1989b;Sterner et al, 1993).…”