Ch. Lucas et S. Lawes, SEXUAL REPRODUCTION OF THE SCYPHOMEDUSA-AURELIA AURITA IN RELATION TOTEMPERATURE AND VARIABLE FOOD-SUPPLY, Marine Biology, 131(4), 1998, pp. 629-638
The effects of food availability and temperature on sexual maturation
and female reproductive output of the scyphomedusa Aurelia aurita was
examined in two populations from the contrasting environments of South
ampton Water and Horsea Lake, England. Trends in oogenesis and subsequ
ent reproductive output differed markedly between the two populations.
In Southampton Water, the onset of sexual maturation occurred earlies
t in the larger medusae, but eventually all females became ripe, the s
mallest being 45 mm bell diameter (BD). The decrease in minimum size a
t maturity was correlated with increasing temperature. In A. aurita fr
om Horsea Lake, size at maturity varied on a seasonal basis, with the
smallest ripe female being only 19 to 20 mm ED. There were spring and
autumn periods of sexual maturation in this population. During the aut
umn period, it is likely that food limitation was playing a more criti
cal role in determining medusa size, with decreasing temperature indir
ectly affecting A. aurita by limiting primary and secondary production
. In similar-sized ripe medusae, fecundity was greater in Southampton
Water, but the planula larvae produced were significantly smaller than
those in Horsea Lake. It is suggested that in Horsea Lake, the qualit
y of the larvae are greater in terms of biochemical content to ensure
survival of the few gametes produced (i.e. K-strategy). Comparison of
the reproductive effort of the two A. aurita populations revealed that
medusae from Southampton Water, which experience greater food availab
ility, are able to direct more energy to reproduction than Horsea Lake
medusae. Tn the latter, A. aurita medusae appear to partition the ava
ilable food resources into either somatic growth (and therefore increa
sed future fecundity) when food is abundant, or reproductive growth wh
en food is scarce.