By Dr. Alexandre Arenzon – 06/27/23
Research in Brazil requires a certain level of creativity, if not a great deal. The Ecotoxicology Laboratory at UFRGS has been dedicated to several research projects to develop and enhance methods for assessing fish toxicity. Our projects encompass various aspects, from the embryonic development of zebrafish to conducting tests for lethality and behavioral effects in these organisms. However, to carry out these research endeavors successfully, in addition to achieving successful reproduction of the organisms, it is crucial to ensure a high larval survival rate. To accomplish this, we have implemented a fish cultivation system with water recirculation after treatment. But think of it as something other than a highly technological treatment system. Essentially, it comprises a series of aquariums connected to a mechanical, biological, and ultraviolet light filtration system (SUMP) that receives, treats, and returns water to the aquariums.
When maintained in the laboratory, zebrafish can achieve high survival rates since receiving appropriate food and water quality parameters, such as temperature, pH, oxygen, and ammonia levels, are maintained within acceptable ranges.
Typically, laboratories without expensive automated fish cultivation systems keep zebrafish larvae in beakers or other containers that require frequent, if not daily, complete or partial water changes. This excessive handling ultimately reduces the organisms’ survival.
After conducting several experiments, we have developed a system that ensures a survival rate of over 90% without larval handling. Our system consists of a series of “coffee filters” used as baskets to hold the larvae. This structure is connected to the laboratory’s filtration system, and continuous dripping within each basket ensures water quality. The water flow is only interrupted during feeding to ensure that the food (Paramecium) remains concentrated and available longer for the fish.
The fish are introduced into the system shortly after hatching and remain there until they are used in experiments (8 to 14 days) or transferred to grow-out tanks. Our data indicate that it is possible to maintain up to 200 larvae in each basket without reducing the survival rate.