Effect of food density on male appearance and ephippia production in a tropical cladoceran, Moina micrura Kurz, 1874

Abstract

A study was conducted to investigate the effects of different food concentrations consisting of Nannochloropsis oculata (4×102, 4×104, 4×106cellsml-1 and control) on male and ephippia production in a tropical cladoceran, Moina micrura. The highest number of males (186.7±13.4 malesl-1) was produced in cultures fed with 4×102cellsml-1 of N. oculata (FC 3) when the population density reached>1600 individualsl-1. Similarly, the highest total mean number of ephippia (160.0±0.0 ephippial-1) was achieved in M. micrura culture supplied with 4×102cellsml-1 of N. oculata (FC 3). The second highest ephippia density was found in M. micrura cultures fed with 4×104cellsml-1 of N. oculata (FC 2) which produced a mean total of 93.3±13.4 ephippial-1 in a population density of >3000 individualsl-1. However, with a population density of>4000 individualsl-1, but fed with the highest food concentration of 4×106cellsml-1N. oculata (FC 1), no ephippia was produced although males were present in the culture. This study illustrates that ephippia were produced in high density cultures with the presence of males and insufficient food supply. Crowding could trigger the production of males, but was not an adequate stress factor for inducing the formation of ephippia. Similarly, food limitation alone did not induce the production of males and ephippia without crowding. © 2013 Elsevier B.V.