Open literature Review Summary

Chemical Name: Atrazine

CAS No: 1912-24-9

ECOTOX Reference Number and Citation: 161314 Paetow LJ; McLaughlin JD; Pauli BD; Marcogliese DJ. 2013. Mortality of American Bullfrog Tadpoles Lithobates catesbeianus Infected by Gyrodactylus jennyae and Experimentally Exposed

to Batrachochytrium dendrobatidis . J. Aquat. Anim. Health 25(1): 15-26.

Purpose of Review: Registration Review

Date of Assessment: 4/6/2015

Brief Summary of Study Findings: This study investigated the e ffects of atrazine on larval American bullfrogs ( Lithobates catesbeianus ) experimentally exposed to Bd. After the start of the experiment, the sample population was found to be infected with gyrodactylus jennyae leading to mild to severe skin erosions in th e experimental population. Increased mortality was observed between control groups and Bd and Bd + atrazine groups, but no difference was found
between Bd and Bd + atrazine groups. The relationship between the co-infections and the severity of skin lesions was correlate d with their influence on survival.

Methods: 102 bullfrog tadpoles ((Gosner stages 26–37) were obtained from an Environment Canada laboratory located in Moncton, New Brunswick 

### ( originally purchased from a commercial source in the United States). A virulent strain of Bd was used (JEL423) provided by J.E. Longcore (University of Maine, Orono). Tadpoles were ra ndomly selected for each treatment group.

Four experimental treatment and control groups were established: (1) a group of tadpoles acutely exposed to two doses of Bd zoospores (2) a group exposed for 14 d to atrazine, followed by two acute doses of zoospores (3) a group exposed for 14 d to glyphosate, followed by two acute doses of zoospores and (4) a group that received no experimental exposures. There were four replicates for each group, except for the control group, which had five; each replicate consisted of six tadpoles. Nominal chemical exposure concentrations were 21 ʅ g of atrazine, and 1.5 mg acid equivalents (a.e.) of glyphosate, per liter of water. In the herbicide exposed animals, the two acute exposures to Bd occurred at 14 and 16 d after the start of the pesticide exposures, and each Bd exposure lasted 24 h.

Each replicate group was maintained in a 33-L aquarium containing 8 L of aerated, dechlorinated water. Three-quarters of the water in each tank was changed every 3 d. During the pesticide exposure phase, the herbicides were replenished with each water change. Water volume was maintained at 1.3 L per tadpole and reduced by 1 L with each tadpole’s death, to a minimum of 4 L. At day 45, all surviving tadpoles were killed by immersion in a 0.8% solution of MS-222 (tricaine methanesulfonate). Tadpol es that died or were killed we re immediately fixed in Bouin’s solution, in a 70% solution of ethanol, or in a 10 % solution of buffered formalin (two tadpoles in each solution per aquarium).At day 0, a stock solution of each herbicide was prepared. During the pesticide exposure phase of the study, each liter of water that was siph oned from the exposure tanks every third day was replaced with 1 mL of pesticide stock solution. At two time points (at 12 h after herbicide addition and at day 14), water samples were drawn directly from two randomly selected pesticide-containing aquariums (one containing atrazine and one containing glyphosate) to compare the actual and nominal concentrations.

The concentrations of glyphosate measured at 12 h and at 14 d post addition of the pesticides to the aquariums were both 2.1 mg/L a.e., which was 1.4 times higher than the nominal concentration of 1.5 mg/L a.e. The concentrations of atrazine measured on the same days were

140 ʅ g/L and 77 ʅ g/L, respectively, which were 6.7 times and 3.7 times higher than the
nominal concentration of 21 ʅ g/L.

Results: By day 30 of the experiment, a consiste nt pattern of dermal depigmentation was observed around the eyes and at the base of the tail of tadpoles in every group, including the control group. At days 30 and 31, two tadpoles that displayed severe depigmentation (each from the group exposed to both glyphosate and Bd ) were removed from the experiment for examination. Depigmentation was found to be the result of skin erosion caused by the tadpoles’ infection by the monogenean ectoparasite G. je nnyae. Further examination revealed that G. jennyae was present in each aquarium.

Increased mortality was observed between control groups and Bd and Bd + atrazine groups, but
no difference was found between Bd and Bd + atrazine groups. Increased susceptibility to Bd due to atrazine exposure was not demonstrated in the study.

Description of Use in Document: Qualitative. This study is of su fficient quality for inclusion in risk assessment, but with limited utility.

Rationale for Use: The study provides information on effects of Bd on survival and the effects of co-infection of tadpoles with monogenean ectoparasite G. jennyae . However, effects due to
atrazine alone could not be discerned from those due to Bd alone.

Limitations of the Study: The presence of the co-infection in all experimental animals with the monogenean ectoparasite G. jennyae confounded interpretation of results.

There is uncertainty in the concentrations of atrazine based on the measured concentrations (14 ug/L and 77 ug/L) as compared to the nominal concentration of 21 ug/L.

Water quality parameters not reported in study.

Reviewer: Colleen M. Rossmeisl, DVM; ERB3, Environmental Fate and Effects Division 

### COLLEEN
ROSSMEISL Digitally signed by COLLEEN ROSSMEISL DN: c=US, o=U.S. Government, ou=USEPA, ou=Staff, cn=COLLEEN ROSSMEISL, dnQualifier=0000069649
Date: 2016.04.07 17:20:44 -04'00'