Growth, production, and demography of Moina micrura in brackish tropical fishponds (Layo, Ivory Coast)

Abstract

Sampling and experiments were performed in brackish fishponds, located near the Ebrie Lagoon, Ivory Coast. Moina developed here at salinities up to about 4 g -1. Mean embryonic and juvenile development times in experimental conditions were 0.82 and 0.80 day, respectively, with 2 juvenile stages at 30 C (salinity of 3 g l-1; 29 ytg chlorophyll-a 1-1) and 1.22 and 1.37, with 2 stages for most individuals and 3 or 4 stages for some of them at 26 C (2 g l-1 and 36 yug 1-1). The corresponding Q o for embryonic development was relatively high (2.7). Growth rates in weight at 30 C were 2.11 and 1.37 bg /xg-g d-, respectively, for the embryonic and juvenile stages, 0.21 for mean somatic growth of the five first female adult stages, and 1.00 for primipara, summed for somatic growth, production of eggs, and embryonic growth. Consequently, differences in growth rates between young and adults were small. M. micrura also was a high fecundity species according to its size, fecundity in nature varying from 2.2 to 7.7 eggs per adult female. Rates of population increase evaluated for some sequences of parthenogenetic growing periods, reached up to 0.9. Most of the daily P/B evaluated by the cumulative growth method reached values above 1.0 (28 to 31 C), minima being about 0.7 for lower temperatures (approximatively 26 °C ). Populations were also characterized by low juvenile to adult ratios (down to 0.9) and high daily birth rates (up to 1.2). Overall, M. micrura is a highly productive, opportunistic species, well adapted to the low salinities that occur during part of the year in the ponds.Biological and population characteristics of this species, and literature data on regulation mechanisms, possible use for aquaculture, and on size in tropical species are discussed. CLA ROT COP '2 M J J A S 0 N 0 J F M Fig.

Zooplankton succession on seasonal floodplains: surfing on a wave of food

“…The rapid burst of M. micrura is consistent with previous reports (Saint-Jean & Bonou, 1994;Høberg et al, 2002), and hatching time of this species is apparently particular short (Kalk, 1979). Rzoska (1961) found M. micrura in rain pools within 48 h of their establishment in Sudan.…”

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

“…At the lower tested densities (33-100 ind l À1 ), we found that the M. micrura strain used here was able to produce males in all treatments, since we did not test other clones we do not know if this effect is clone specific. The largest sex ratio (0.58), obtained with the D 2 V 1 treatment, was lower than that obtained by Saint-Jean & Bonou, (1994) and Bonou & Saint-Jean (1998), who recorded up to 0.82, but at larger population densities.…”

“…From this observation, we can assume that crowding was not a primary factor in promoting male production, but the encounter rate and the physical interaction among individuals (which was higher in the largest culture volume, even at the lowest density) were apparently important inducers for male production from the first brood on. Saint-Jean & Bonou (1994) and Bonou & SaintJean (1998) stated that densities of 300 to 500 ind l À1 are necessary for a change to occur in the type of reproduction in M. micrura, and that the production of males increases at densities of ca. 1 ind ml À1 .…”

Distribution and faunal richness of Cladocera in western Uganda crater lakes

“…At the other extreme, Karualona iberica, Moina micrura and Macrothrix triserialis did not exhibit clear responses to any of the measured environmental variables, indicating that these species are rather eurytopic in nature. Indeed, Moina micrura is considered by some to be the most successful cladoceran in tropical Africa for its widespread distribution and fast adaptation to local changes in ecological conditions (Saint-Jean & Bonou, 1994). In this study, we found this species in a wide diversity of lakes, ranging from shallow, eutrophic lakes with abundant macrophytes to very deep, oligotrophic lakes without significant littoral zone.…”