Effect of culture density and volume on Moina micrura (Kurz, 1874) reproduction, and sex ratio in the progeny

Abstract

Moina micrura is a cosmopolitan, cyclic parthenogenetic, cladoceran with ample morphological and ecological plasticity that inhabits temperate, tropical, and subtropical regions of the world. Sexual reproduction in cladocerans is a phenomenon induced by environmental factors, mainly associated with adverse conditions, including crowding. In this study we have assessed the effects of population density combined with the volume available for individual development, on the number of newborns and on the sex ratio in the progeny. Three parthenogenetic female densities (D 1 = 33 ind l À1 , D 2 = 66 ind l À1 , D 3 = 100 ind l À1 ) were assayed in combination with three culture volumes (V 1 = 30 ml, V 2 = 60 ml, V 3 = 120 ml), at 21°C. Once the reproduction began, progeny was isolated daily and counted, identifying female and male neonates. Culture volume was the only factor that had a significant effect on the total progeny, as well as on the number of males in the progeny; the highest sex ratio was recorded in D 2 V 1 (0.58), whereas the lowest was for D 1 V 3 (0.06).Female density had no significant effect on the number of sexual M. micrura. We hypothesize that male production (quantity and frequency) was higher in the lowest tested volume because of a reduction in the space available per individual, but not necessarily associated with the physical interaction related with a high encounter rate in more crowded conditions.

Impacts of male and food density on female performance in the brackish cladoceran Daphniopsis australis

“…This contradicts the notion that male presence could trigger females to switch from asexual to sexual reproduction (Innes, 1997). Martinez-Jeronimo et al (2007) reported that the number of males that trigger the sexual reproduction accounted for 6-56% in a cladoceran population, a result consistent with the proportion of males (50%) observed in this study. Despite the lack of switch in reproductive mode, we found that parthenogenetic females showed higher egg abortion at high food density in the presence of a male than that without the male.…”

“…Besides food availability, changes in photoperiod, temperature and population density also trigger the switch from asexual to sexual reproduction (Banta et al, 1939;Berner et al, 1991;Kleiven et al, 1992). Among these proximate factors, the initiation of sexual reproduction seems to be more responsive to the changes in population density (Innes, 1997) and food availability than other factors (Gibson et al, 1998;Martinez-Jeronimo et al, 2007). Nevertheless, despite the fact that the male is the key element in sexual reproduction, little is still known on its role in regulating cladoceran reproduction.…”

Increases of Chamber Height and Base Diameter Have Contrasting Effects on Grazing Rate of Two Cladoceran Species: Implications for Microcosm Studies

“…Comparing experimental results between different microcosm volumes may reveal the scale effect on behavior, growth and reproduction, and population dynamics of phytoplankton-zooplankton systems [ 1 , 6 , 8 ]. For example, significant scale effects on zooplankton behavior have been found in studies with chamber volumes ranging from 10 mL to more than 500 mL [ 2 , 8 – 12 ]; similar effects have been observed in sex ratio and reproduction of the cladocaran species ( Moina micrura ) when the culture volume increased from 30 to 120 ml [ 13 ].…”

“…Importantly, increasing microcosm volume can be achieved by increasing either chamber height, or base area, or both. Among the previous studies addressing effects of spatial scale on phytoplankton-zooplankton interactions, some examined the effects of increasing chamber height [ 6 ], and some others examined the effect of base area [ 14 ] or both [ 1 , 5 , 13 ]. To the best of our knowledge, however, few studies have explicitly distinguished the effects of increasing chamber height and base area, and hence it is not clear whether increasing height has the same effect on the ecological processes as increasing base area, i.e., whether the effect of the shape of such a three-dimensional space on species interactions should be determined.…”

Zooplancton de ambientes acuáticos de la cuenca del río Salado (Buenos Aires): estudio de las relaciones interespecíficas y principales factores de control mediante experiencias de laboratorio y microcosmos

“…Asimismo, debe destacarse que se le brindó su alimento preferido (Martínez, 2000;Martínez & Montecino, 2000). Debe destacarse que a pesar de que el volumen de los recipientes era reducido no hubo producción de machos como lo señalado por Martínez Jerónimo et al (2007), quienes postulan que la falta de espacio promueve dicha producción al impedir los desplazamientos o la obtención del alimento y no la vinculan al hacinamiento.…”