Kreisel Jellyfish Tank
We have an exciting new addition to our Centre from 29 March… a Kreisel tank for displaying jellyfish! It now sits proudly in the main floor space, all thanks to the Red-fin team – Chris’s professional installation and Toshi’s informative training.
For the past few months, we have been growing-on various species of jellyfish in our Fish Lab, to be displayed in our new tank. At first, many of the jellies acclimatised quickly to their new aquarium home and seemed to thrive. However, we suddenly started to see some casualties, as certain species were found to be more sensitive to changes in various aquatic parameters. When the health of our Sea Nettle jellyfish (Chrysaora quinquecirrha) started to deteriorate, we increased the frequency of water cycling and subsequent feeding, but this made no difference, so we released them back into the ocean. (It’s possible that micro-bubbles of air caused the jellyfish to become stressed.)
Currently, we are growing juvenile stages (ephyra and polyps) of 62 specimens of ‘Common jellyfish’ (Aurelia aurita) in our small closed-system Kreisel tank.
The first month of rearing our Aurelia jellyfish specimens was an exciting and educational process. It was remarkable to observe the anatomical developments and morphological advancements from the 0.02cm ephyrae to the 8.5cm juvenile medusae. Despite the simplicity of their function and lifestyle, being comprised of 95% water (and 5% protein) means that jellyfish are very sensitive to environmental parameters.
We expected the average bell diameter would increase over time as the jellyfish grew, but it was the rate of growth that was of particular interest. We found that sudden increases in water temperature had a negative impact on the jellyfish metabolism, slowing the rate of growth (days 6-10 and 16-20 in the graph). When the temperature went down again (optimally to 23-25°C), growth rates increased.
We can deduce that fluctuations in water temperature were not beneficial to jellyfish health, and that future tank parameters will need to be maintained within a close range to allow for optimal acclimation and reduced stress.
Based on one month’s growth data, we can predict that a steady temperature of 23°C should enable the jellyfish to grow to 10cm in diameter (population average), reaching adult status after 3 months.