Life history, population dynamics, standing biomass and production of Bosminopsis
deitersi (Cladocera) in a shallow tropical reservoir
MELÃO1,3, M.G.G. & ROCHA2,3, O.
1 Universidade Federal de São Carlos (UFSCar), Dep. Hidrobiologia, Lab. Plâncton, P.O. Box 676, Zip code 13.565-905, São Carlos, SP, Brazil.
e-mail: dmgm@power.ufscar.br
2 UFSCar, Dep. Ecologia e Biologia Evolutiva, P.O. Box 676, Zip code 13.565-905, São Carlos, SP, Brazil.
e-mail: doro@power.ufscar.br
3 Programa de Pós-Graduação em Ecologia e Recursos Naturais, UFSCar.
ABSTRACT: Reproductive performance, life history parameters (duration of embryonic and post-embryonic development and longevity) and stage-specific length and weight values were measured for a planktonic tropical cladoceran species, Bosminopsis deitersi, from a shallow Brazilian reservoir (Lagoa Dourada). This species was reared in laboratory under 20oC and 25oC and fed ad libitum on natural seston enriched with algae from laboratory cultures at 105 cells mL-1. Laboratory data on the duration of development and biomass, together with population dynamics data obtained in the field, were used to estimate summer and winter standing stock and production of B. deitersi in Lagoa Dourada reservoir. Development times were mainly temperature dependent, once food was not limiting, with shorter periods of embryonic and post-embryonic development and decreased longevity at 25oC. Mean weights of neonates, juveniles and adults were 0.23, 0.55 and 0.80mg, respectively. B. deitersi showed better reproductive performance in laboratory cultures with higher mean clutch-size (1.47 and 1.60 eggs per female at 20oC and 25oC, respectively) than field populations (1.12 and 1.11 eggs per female in winter and summer, respectively). Maximum production rate of B. deitersi in the field, attained during summer, was 5.08mgDW m-3 day-1 and the highest daily production: biomass (P:B) ratio was 0.35. Over short-time intervals (every other day) there was great variability on species’ production rates. Although this is the very first experimental study undertaken on this species, B. deitersi production rates were low compared to values reported in the literature for other cladocerans, from both tropical and subtropical regions.
Key-words: secondary production, growth, reproduction, seasonal variation, tropical cladoceran.