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Development and disease: How
susceptibility to an emerging
pathogen changes through anuran
development
By Nathan A. Haislip, Matthew J. Gray, Jason T.
Hoverman, and Debra L. Miller
Ranaviruses have caused die-offs of
amphibians across the globe. In
North America, these pathogens cause
more amphibian mortality events than
greater than realized due to the greater
difficulty of detecting morbid hatchlings
and larvae compared to metamorphs.
Full article: Haislip, NA, MJ Gray,
JT Hoverman, and DL Miller.
2011. Development and disease:
How susceptibility to an emerging
pathogen changes through anuran
development. PLoS ONE 6(7):
e22307. doi:10.1371/journal.
pone.0022307.
dependent and selenium-independent).
Additionally, lipoperoxidation (LPO)
was also assessed in the same tissues via
thiobarbituric acid reactive substances
(TBARS) assay and lactate dehydrogenase
(LDH) activity was determined in muscle.
Furthermore we analyzed the physical and
chemical parameters of M and REF water
as well as their metal content. Our results
revealed that the majority of metals were
in higher concentrations in tissues of M
organisms. This trend was especially evident
for U whose content reached a difference of
1350 fold between REF and M organisms.
None of the organs tested for antioxidant
defenses revealed LPO, nonetheless, with
exception for liver, all organs from the
M frogs presented increased total GPx
activity and selenium-dependent GPx.
This response was only significant for lung,
probably as a consequence of the significant
inhibition of CAT upstream and in order to
cope with the subsequent increase in H 2
O 2
.
Lungs were the organs displaying greater
responsiveness of the anti-oxidant stress
system in frogs from the uranium mine area.
In amphibian larvae, gross lesions indicative of ranavirus infection include erythema at the base of the gills,
ventrum, and legs, and swelling of the legs, body, and gular region. This image shows severe body swelling in
an American bullfrog tadpole (Rana catesbeiana) that was experimentally infected with ranavirus. An uninfected
tadpole is shown for comparison. Photo: Nathan A. Haislip
any other pathogen. Field observations
suggest that ranavirus epizootics in
amphibian communities are common
during metamorphosis, presumably due
to changes in immune function. However,
few controlled studies have compared the
relative susceptibility of amphibians to
ranaviruses across life stages. Our objectives
were to measure differences in mortality and
infection prevalence following exposure to
ranavirus at four developmental stages and
determine whether the differences were
consistent among seven anuran species.
Based on previous studies, we hypothesized
that susceptibility to ranavirus would be
greatest at metamorphosis. Our results did
not support this hypothesis, as four of the
species were most susceptible to ranavirus
during the larval or hatchling stages. The
embryo stage had the lowest susceptibility
among species probably due to the protective
membranous layers of the egg. Our results
indicate that generalizations should be made
cautiously about patterns of susceptibility
to ranaviruses among amphibian
developmental stages and species. Further,
if early developmental stages of amphibians
are susceptible to ranaviruses, the impact
of ranavirus epizootic events may be
Antioxidant response and metal
accumulation in tissues of Iberian
green frogs (Pelophylax perezi)
inhabiting a deactivated uranium
mine
By Sérgio M. Marques, Sara C. Antunes, Bruno
Nunes, Fernando Gonçalves & Ruth Pereira
Mining activities frequently create
deeply impacted areas. These areas
usually remain contaminated for large
periods, originating extreme habitats
where metal rich effluents with acidic pH
are easily formed. Such is the case of the
deactivated uranium mine in the village
of Cunha Baixa (Portugal). In this work
we determined metal accumulation and
antioxidant response of Iberian green frogs
(Pelophylax perezi) inhabiting the effluent
pond in this mine (M) and compared the
results with frogs from a reference site
(REF). Metal accumulation was studied in
liver, kidney, bones, muscle and skin of P.
perezi and enzymatic activity was studied in
liver, kidney, lung and heart by determining
glutathione-S-transferases (GSTs), catalase
(CAT), glutathione reductase (Gred), and
glutathione peroxidase (GPx; both selenium-
Full article: Marques et al. (2011).
Antioxidant response and metal
accumulation in tissues of Iberian
green frogs (Pelophylax perezi)
inhabiting a deactivated uranium
mine. Ecotoxicology 20; 1315-1327.
(s.reis.marques@gmail.com)
Species-level correlates
of susceptibility to the
pathogenic amphibian fungus
Batrachochytrium dendrobatidis in
the United States
By Betsy A. Bancroft, Barbara A. Han, Catherine
L. Searle, Lindsay M. Biga, Deanna H. Olson,
Lee B. Kats, Joshua J. Lawler, & Andrew R.
Blaustein
Disease is often implicated as a factor
in population declines of wildlife and
plants. Understanding the characteristics
that may predispose a species to infection
by a particular pathogen can help direct
conservation efforts. Recent declines
in amphibian populations world-wide
are a major conservation issue and may
be caused in part by a fungal pathogen,
Batrachochytrium dendrobatidis (Bd).
We used Random Forest, a machine
learning approach, to identify specieslevel
characteristics that may be related to
susceptibility to Bd. Our results suggest that
body size at maturity, aspects of egg laying
behavior, taxonomic order and family,
and reliance on water are good predictors
of documented infection for species in
the continental United States. These
results suggest that, whereas local-scale
environmental variables are important to the
46 | FrogLog Vol. 98 | September 2011