INVESTIGADORES
ZAGARESE Horacio Ernesto
artículos
Título:
Effects of ultraviolet radiation on the eggs of landlocked Galaxias maculatus (Galaxidae, Pisces) in Northwestern Patagonia
Autor/es:
MIGUEL BATTINI,; VANINA ROCCO,; MARIANA LOZADA,; HORACIO ZAGARESE
Revista:
FRESHWATER BIOLOGY (PRINT)
Referencias:
Año: 2000 vol. 44 p. 547 - 552
ISSN:
0046-5070
Resumen:
1) Ultraviolet radiation (UVR) damages early life stages of several
fish species. Galaxias maculatus is a small catadromous fish, with
landlocked forms occurring in many lakes within the Nahuel Huapi National Park
(Patagonia, Argentina). In this work, the vulnerability
of G. maculatus eggs exposed to both natural and artificial UVR was
investigated in relation to water transparency.
2) Field experiments were performed in two lakes differing in UVR
attenuation. Galaxias maculatus
eggs were exposed to in situ levels of UVR in quartz tubes incubated at
various depths. For laboratory
experiments, the eggs were exposed to five levels of artificial UVB radiation.
3)
Exposure to natural UVR causes
various degrees of egg mortality depending on water transparency and incubation
depth. In the less transparent lake (Kd320
= 3.08 m-1), almost complete mortality was observed near the
surface. At a depth of 43 cm the
observed mortality was only 22%, but was still significantly different from the
dark control. In the most transparent
lake (Kd320 = 0.438 m-1), almost total mortality was
observed in tubes incubated at 2.56 m or shallower. A gradual decline in mortality was recorded
from that depth to 3.78 m where the values approached those in the dark control
treatments.
4)
A monotonic relationship
between mortality and UV exposure could be observed both in field and
laboratory experiments. Using the
results from field incubations, a LD50 of 2.5 J cm-2 nm-1
was estimated. In a few mountain lakes,
this value would be exceeded even if the eggs were laid at the maximum depth of
the lake. Thus UVR seems a sufficient cause to explain the absence of G.
maculatus populations in some mountain lakes. For most lakes, however, UVR
is probably one of several important environmental factors, which together
determine the habitat suitability.