tions in the days before the sampling, together with the
lack of relevant hydrodynamics in the lake, other active
factors may have played a role in determining the
uneven distribution of specimens, such as feeding activity
(Boothroyd et al. 2002). Where present, medusae
were preferentially located between a depth of 50 cm
and 2 m. However, we cannot exclude the presence of
specimens at depths greater than the transparency of
water (about 4 m) because massive vertical migrations
have been recorded, with a higher density at the surface
only during the night (Spadinger & Maier 1999). The
average umbrella/bell diameter was 13.2 mm (11.0-
16.0), a value smaller than that reported in the literature,
which includes a diameter up to 25 mm (Spadinger &
Maier 1999; Jankowski 2001; Pérez-Bote et al. 2006).
The observation of gonads did not reveal the presence
of either eggs or sperm, indicating that all of the specimens
were still immature, a finding that is consistent
with their small dimension. Sexual maturity is reached
after 5-6 weeks from their metamorphosis (Acker &
Muscat 1976), and the bloom was probably in its initial
phases at the time of sampling.