Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory

• Published in: Brazilian Journal of Biology
• Main Authors: FC. Massaro, O. Rocha
• Format: Article in Journal/Newspaper
• Language: English
• Published: Instituto Internacional de Ecologia
• Subjects: freshwater Cnidaria; individual growth; population growth; culture of hydras; Hydra viridissima; Science; Q; Biology (General); QH301-705.5; Zoology; QL1-991; Botany; QK1-989; Antarc*; Antarctica
• Online Access: https://doi.org/10.1590/S1519-69842008000200020; https://doaj.org/article/0376c211d759459bb5b3125c81ebc2ca

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 °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.