Food regulation of growth and maturation in a natural population of Aurelia aurita (L.)
In: Journal of Plankton Research. Oxford University Press: New York,. ISSN 0142-7873; e-ISSN 1464-3774, more
|   |
| Abstract |
Growth and maturity development of the moon jellyfish. Aurelia aurita, were recorded in Vågsbøpollen, a small and semi-enclosed bay on the Norwegian west coast, and compared to those of medusae transferred to excess food and starving conditions, respectively. Mesozooplankton were extremely scarce in Vågsbøpollen. The abundance and biomass of the medusae in the poll were higher than those typicallyfound in open waters, reaching a maximum of 22 ind. m-3 and 710 mg C m-3 in June. The average diameter of medusae in the p increased to 8 cm until the last part of June, with an instantaneous growth rate between 1.5 and 20% day-1, thereafter retarding somewhat, giving a negative growth rate of up to 2.6% day-1. Starving medusae showed a negative growth rate ofup to 13.4% day-1, and all the rnedusae were dead after 49 days. Well-fed medusae showed a very stable growth over a 56 day period, diverging from the pollpopulation from early June, and with a growth rate between 3.8 and 9.8% day-1. Medusae from the pollpopulation began carrying planulae on their oral arms when at least 5 cm in diameter, whereas not even the largest medusa of 15.6 cm diameter among those in the well-fed group produced any planulae. For the first time, it is thus explicitly shown that thesize and maturity of A.aurita are externally controlled through food availability. Scarcity of food reduces the growth rate, but also changes the energy allocation towards reproduction, which thus occurs at a smaller size than for well-fed rnedusae. Its plasticity makes it possible for this species to exploit environments with low advection of food and develop high abundance in such environments, without losing fecundity. |
|
