                                                                                              Silvia Vendruscolo Milesi, Cristiane Biasi, Rozane Maria Restello e Luiz Ubiratan Hepp * Laboratório de Biomonitoramento, Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto Uruguai e das Missões, Av. Sete de Setembro, 1621, Cx. Postal 743, 99700-000, Erechim, Rio Grande do Sul, Brasil. *Autor para correspondência. E-mail: lhepp@uri.com.br      !   !  " #$  %&   "  " ’ (" " ""  "  )  *  + "   "  *  *    *! !  ,-.   (" "      " /, 0’"    * 1 -.   !" ,   2  .  "   ""   -3  "   "!   -3    *   " $ #$&  !4     $*"   " % #%&  !      "! ’   $*" 5*"  "  !   /,    "   "    " ’  -.  /   " !" "" $ / " % #$%#&% %!" "’’" ’ (" )&* +, -+. + !" "+! (+""" ((*+/ + "( + *!"+ $0 6* " ! * 7 8   * !! ! " #$  %&  * * " ""7 6* "  8 8  /7 8 " )  9 +  *   " ! 8 *7*  ! 7 ,   6*  ! " 7 0" *  * * 7 0 8  (    !   "   8  6*  *8 7  * "   * ""7 "    " $ *8 ! 7  $*" 7 % " !!  * * ""7  $*" 7 5 ! * "  !!  * " *  7 6*      ! * * ""7  *  !  /7 ! * " 1"/ 2, " $ " /7 %     :" 3   ,-.    .    *; !"   -3 4 / "!"  /    /" "    " /  -.           ;   *;   ; " #<"0    => ?"*    > 7  1* &  -3  "   " @ !   " / " "!-3     -.  "" #AB %B & C  " /  " ’ .  " !  "-.  ; " #<"0  =&   "  "-  /         #$7 $" &  -.   "  "    " @"    "   " " ; #C    +& " @       :*" 1  6* #(B8B  ?8 )& C  ; " $ #$&  % #%& 4" ;  /    " "  .  " !,  " "  ; 2   ;"  #?"*   > AB  %B &    #+&  0    / ;" /  0-.  " "  "  -3  , !  " !