FrogLog 103 PDF here - Amphibian Specialist Group

estimates were 4.10 mg/l for 72-hrs
exposure in L. pipiens and 4.13, 3.51 and
2.95 mg/l for 24-, 48-, and 72-hrs exposure
in S. tropicalis. These data suggest that
exposure to NAs at environmentally
realized concentrations may negatively
affect tadpole populations.
S.D. Melvin, V.L. Trudeau, Environ. Pollut.
167, 178 (2012).
Embryos of Silurana tropicalis and Lithobates pipiens
(not shown) exposed to environmental concentrations
of naphthenic acid throughout early development
experience abdominal air bubbles and kinked tails.
Photo: Steven D. Melvin.
Oxidation of retinoic acids in
hepatic microsomes of wild
bullfrogs Lithobates catesbeianus
environmentally-exposed
to a gradient of agricultural
contamination
By Janik Thibodeau, Sébastien Filion, Philip
Spear, Joanne Paquin & Monique Boily
In the St. Lawrence River valley, high
incidences of deformed frogs have been
documented in agricultural areas. The
malformations observed in wild amphibians
are similar to deformities produced in
laboratory by experimental manipulation
of retinoids, namely retinoic acid (RA), one
Bullfrog in agricultural environment. Photo: Bullfrog
project, TOXEN-CIRÉ, UQAM.
of the biologically active form of vitamin
A. Earlier studies located in a highly
agricultural contaminated watershed
(Yamaska River, Québec, Canada) showed
unbalanced retinoids in bullfrogs with a high
concentration of RA metabolites in plasma.
In order to verify the influence of liver on
this metabolism, we set an in vitro method
to test the hepatic microsomal RA oxidation
in bullfrogs. Compared to other vertebrates,
the RA oxidation in bullfrogs was greater
when the substrate 13-cis-RA was used
instead of at-RA. While no relationship
was established between the contamination
and the RA metabolism in male bullfrogs,
the females showed an increased plasma
13cis-4-oxo-RA concentration, in step with
the sampling sites’ agricultural activity.
Additional studies will help clarify if a
high circulating 13cis-4-oxo-RA could
compromise the proportion of retinoids to
be deposited in the eggs, and consequently,
the normal development of the embryos. In
both sexes, the liver metabolism as well as
the isomerisation processes could influence
the circulating RA metabolites in bullfrogs
exposed to agricultural contaminants.
J. Thibodeau, S. Filion, P. Spear, J. Paquin,
M. Boily. Ecotoxicol. 21, 1358 (2012).
Cyanobacteria blooms produce
teratogenic retinoic acids
By Xiaoqin Wu, Jieqiong Jiang, Yi Wan, John P.
Giesy & Jianying Hu
Deformed amphibians have been
observed in eutrophic habitats, and
some clues point to the retinoic acids
(RAs) or RA mimics. However, RAs are
generally thought of as vertebrate-specific
hormones, and no evidence shows that RAs
exist in cyanobacteria or algae blooms. By
analyzing RAs and their analogues 4-oxo-
RAs in natural cyanobacteria blooms and
cultures of cyanobacteria and algae, we
showed that cyanobacteria blooms could
produce RAs, which were powerful animal
teratogens. Intracellular RAs and 4-oxo-
RAs with concentrations between 0.4 and
4.2×10 2 ng/L were detected in all bloom
materials and extracellular concentrations
as great as 2.0×10 ng/L were measured
in water from Taihu Lake, China, which
might pose a risk to wildlife through
chronic exposure. Further examination of
39 cyanobacteria and algae species revealed
that 32 species could produce RAs and
4-oxo-RAs (1.6-1.4×10 3 ng/g dry weight,
DW), and the dominant cyanobacteria
species in Taihu Lake, Microcystis flosaquae
and Microcystis aeruginosa,
produced high amounts of RAs and 4-oxo-
RAs with concentrations of 1.4×10 3 and
3.7×10 2 ng/g DW, respectively. Most
Retinoic acids in eutrophic water.
genera of cyanobacteria that can produce
RAs and 4-oxo-RAs such as Microcystis,
Anabaena and Aphanizomenon often occur
dominantly in natural blooms. Production
of RAs and 4-oxo-RAs by cyanobacteria
were associated with species, origin location
and growth stage. These results represent
the first conclusive demonstration of an
endogenous production of RAs in freshwater
cyanobacteria blooms. The observation
of teratogenic RAs in cyanobacteria is
evolutionarily and ecologically significant
because RAs are vertebrate-specific
hormones and cyanobacteria form extensive
and highly visible blooms in many aquatic
ecosystems.
X. Wu, J. Jiang, Y. Wan, J. P. Giesy, J.
Hu, Proc. Natl. Acad. Sci. USA. 109, 9477
(2012).
Field and Laboratory Studies of
the Susceptibility of the Green
Treefrog (Hyla cinerea) to
Batrachochytrium dendrobatidis
Infection
By Laura A. Brannelly, Matthew W. H. Chatfield
& Corinne L. Richards-Zawacki
Amphibians worldwide are experiencing
devastating declines, some of which
are due to the amphibian chytrid fungus
(Batrachochytrium dendrobatidis, Bd).
Populations in the southeastern United
States, however, have not been noticeably
affected by the pathogen. The Green
treefrog (Hyla cinerea) is abundant and
widespread in the southeastern United
States, but has not been documented to
harbor Bd infection. This study examined
the susceptibility of H. cinerea to two
strains of Bd in the lab and the prevalence of
infection in wild populations of this species
in southeastern Louisiana. Although we
were able to infect H. cinerea with Bd in the
lab, we did not observe any clinical signs of
chytridiomycosis. Furthermore, infection
FrogLog 20 (4) | Issue number 103 (July 2012) | 47