title: Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory.
abstract: Hydras, the most representative freshwater Cnidaria, are of common occurrence in bodies of water in every continent except Antarctica. This study was planned with the aim of maintaining a population of Hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. The organisms were maintained in reconstituted water at 20 +/- 2 degrees C, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran Ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). The individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 +/- 1.5 days on average. The hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 +/- 2.63 days. Hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. It is thus a promising candidate test-organism for ecotoxicological studies.
authors.affiliation: Programa de Pós-Graduação em Ciências da Engenharia Ambiental, Escola de Engenharia de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil. fe_massaro@yahoo.com.br
authors.forename: F  C
authors.initials: F
authors.lastname: Massaro
authors.forename: O
authors.initials: O
authors.lastname: Rocha
mesh_terms: D000818:Animals; D006829:Hydra / Q000145:classification / Q000254:growth & development / Q000502:physiology*; D007753:Laboratories; D011158:Population Growth; D013997:Time Factors