G I A R D I A M U R I S A N D G I A R D I A D U O D E N A L I S G R O U P S : 
U L T R A S T R U C T U R A L D I F F E R E N C E S B E T W E E N T H E T R O P H O Z O I T E S 

Maria Inê s L . S O G A Y A R (1 ) &  E l is a Aparecid a G R E G Ó R I O (2 ) 

S U M M A R Y 

Trophozoites o f th e Giardi a muri s grou p fro m hamsters , domesti c rat s an d 
mice an d o f th e Giardi a duodenali s grou p fro m hamster s an d domesti c rat s wer e 
examined b y transmissio n electro n microscopy . Th e basi c ultrastructur e o f th e 
trophozoites wa s similar. Difference s were shown in the morphology o f th e ventro -
lateral flang e o f th e trophozoite s o f Giardi a muris an d Giardia duodenalis groups. 
Marginal plate s are less developed in the species of the Giardia duodenalis group. I n 
this group , th e dista l extremit y o f th e latera l flang e i s shor t an d thic k an d th e 
marginal plat e doe s no t penetrat e int o th e dista l extremit y o f th e flange . I n th e 
Giardia muris group, the ventro-latera l flang e is well developed and narrow an d the 
marginal plate penetrates the distal extremity o f the flange. The osmiophilic lamella , 
which accompanie s th e dorsa l surfac e o f th e margina l plat e i s see n onl y i n th e 
Giardia muri s group . 

K E Y W O R D S : Giardi a muris; Giardi a duodenalis; Trophozoite, Ultrastructure . 

I N T R O D U C T I O N 

Based o n th e media n bod y morpholog y 
and th e trophozoite' s siz e an d shap e one ca n 
differentiate Giardi a muri s an d Giardi a 
duodenalis b y ligh t microscopy 4. Th e dat a i n 
the literatur e abou t suc h differentiatio n b y 
electron microscop y ar e scarce. N E M A N I C et. 
a l . 1 2 wer e unabl e t o sho w difference s betwee n 
trophozoites o f Giardi a muri s fro m mic e an d 
those of Giardi a lamblia from man. 

Taking i n accoun t thes e result s an d since 
the morpholog y o f Giardi a from hamster s and 
domestic rat s ha d no t bee n describe d yet , w e 
decided t o stud y comparativel y th e 
ultrastructure o f Giardi a muri s an d Giardi a 
duodenalis trophozoite s foun d i n hamsters , 
domestic rat s and mice. 

M A T E R I A L A N D M E T H O D S 

Giardia specie s fro m naturall y infecte d 
animals wer e previousl y identifie d b y ligh t 
microscopy. Smear s o f faece s or mucos a were 
fixed wit h Schaudinn' s solutio n an d staine d 
with Heidenhain' s haematoxylin . Th e species 
of Giardi a wer e identifie d b y morphologica l 
features an d trophozoit e lengt h an d widt h 
measurements, at 1.00 0 x magnification . 

Trophozoites o f th e Giardi a muri s grou p 
from hamsters , domesti c rat s (Rattu s rattu s 
rattus) an d mice and Giardia duodenalis grou p 
from hamster s an d domesti c rat s wer e used . 
Fragments o f th e host' s mucos a were fixe d i n 
2.5% glutaraldehyd e buffere d a t p H 7. 3 wit h 

(1) Departmen t o f Paras i to logy , I B B , U N E S P , 1860 0 Botucatu , Sã o P a u l o, B raz i l . 

(2) Departmen t o f Morphology , I B B , U N E S P , 1860 0 Botucatu , Sã o Pau lo , B raz i l . 



0.1M phosphat e buffer, post-fixed i n 1 % osmic 
tetroxide i n th e sam e buffer an d embedde d i n 
Araldite. Th e ultrathi n section s wer e staine d 
with urany l acetat e an d lea d citrat e an d 
examined wit h a n E M 30 1 Philip s electro n 
microscope. 

R E S U L T S 

The basi c ultrastructur e o f th e tropho -
zoites o f Giardi a uiuri s grou p fro m hamsters , 
domestic rat N and mice and Giardia duodenalis 
group fro m hamsters and domestic rat s is simi-
lar. Th e trophozoite s hav e a  microtubuia r ad -
hesive disk surrounded b y an adjacent cytoplas -
mic flang e know n a s th e v  entro-lateral flang e 
and fou r pair s o f flageil a (Fig , 1 ) whose basa l 
bodies ar e located betwee n th e tw o nuclei . Os-
miophilic materia l i s seen nexi t o th e axonemes 
of th e flageil a an d vacuole s are presen t i n th e 
dorsal regio n o f th e trophozoite . Scattere d i n 
the cytoplasm , w e hav e notice d cytoplasmi c 
clefts withou t bein g envelope d b y membranes , 
with a  little dens e homogeneou s conten t (Fig . 
1), glycoge n an d fre e ribosomes . Tw o paralle l 
rows o f microtubule s (funis ) accompany the in-
tracyioplasmic trac k o f th e caudal flageila. The 
median bod y i s forme d b y microtubule s wi -

thout apparen t relationshi p t o othe r structures . 
Mitochondria, endoplasmi c reticulum an d Gol-
gi apparatu s ar e no t noticed . 

We have not observe d differences betwee n 
Giardia duodenali s grou p fro m hamster s an d 
domestic rat s o r amon g Giardi a muri s grou p 
from hamsters , domesti c rat s an d mice . 
Differences were , however , evidence d i n th e 
morphology o f th e ventrolatera l flang e o f 
trophozoites o f Giardi a muri s an d Giardi a 
duodenalis groups. 

In th e tw o group s studie d th e flang e i s 
arranged peripherall y t o th e striate d dis k 
presenting a  cytoplasmi c li p supporte d b y 
marginal plate. * whic h ar e associate d with on e 
of th e axoneme s of th e anterolatera l flageila . 

In the Giardia duodenalis group both from 
hamsters (Fig . 2) and from domesti c rat s (Fig. 
3), th e cytoplasmic lip that makes up the ventro -
lateral flang e i s shor t an d thick , an d doe s no t 
show electro n dens e materia l i n it s dista l 
extremity. Th e plate s tha t suppor t th e flang e 
are striated , littl e develope d an d ar e jus t 
associated wit h th e plasmi c membran e o f th e 
ventral surfac e o f th e ventrolatera l flange . I n 
this group , th e osmiophili c lamell a i s no t 
observed. 



In Giardi a muri s grou p fro m hamster s 
(Fig. 4) , domestic rat s (Fig . 5) and mice (Fig. 6) 
the dista l extremit y o f th e cytoplasmi c li p i s 
narrow an d developed , an d i t i s darkene d b y 
dense cytoplasm . Th e margina l plate s see m t o 
occupy the whole flang e extension. They extend 
from th e dorso-latera l surfac e o f th e striate d 
disk int o th e ventro-latera l flang e bein g 

associated wit h th e flang e plasmi c membran e 
either dorsall y o r ventrally . Thes e margina l 
plates sho w striation s an d penetrat e throug h 
the flange and become lost in the dense material 
of thei r dista l extremity . A  dens e lamell a o f 
osmiophilic materia l tha t accompanie s th e 

dorsal surface of th e plate i s noticed associated 
with the margina l plates . 

D I S C U S S I O N 

Giardia muri s an d Giardi a duodenali s 
groups fro m hamster s an d domesti c rats , 
described for th e first time in this paper, show a 
basic ultrastructura l similaritie s t o th e othe r 
species already described in th e literature , such 
as Giardi a muri s fro m mice 2 5 6  7 1 4 ; Giardi a 
lamblia fro m m a n 1 1 0 1 5 ; Giardi a duodenali s 
from rabbits 3 an d Giardia canis from dogs 1 3. 



Our result s show that Giardia belonging t o 
the sam e group (duodenali s o r muri s groups ) 
do no t presen t ultrastructura l differences whe n 
located in different animal s (hamsters-domestic 
rats an d hamsters-domesti c rats-mice , 
respectively). 

However, Giardi a belongin g t o differen t 

groups (muri s an d duodenalis ) fro m th e sam e 
host (hamste r o r domesti c rat ) sho w marke d 
differences i n th e ventro-latera l flang e 
ultrastructure regarding thei r size , arrangemen t 
of th e margina l plate s an d presenc e o f 
osmiophilic lamella . 



According t o H O L B E R T O N 7 , i t seem s 
that th e for m adopte d b y th e ventro-latera l 
flange ma y ac t o n th e attachmen t o r 
detachment o f th e hos t t o th e substrat e a s the 
magnitude o f th e suctio n forc e cause d by th e 
striated dis k depend s o n th e calibe r o f th e 
lateral channel s betwee n th e ventro-latera l 
flange an d th e substrate . Therefore , th e 
differences foun d betwee n muri s an d 
duodenalis group s i n relatio n t o th e 
ventro-lateral flang e sugges t tha t ther e i s some 
difference i n th e attachment o f thes e species t o 
the substrate . Th e fac t tha t th e flang e i s les s 
developed i n Giardi a duodenali s lead s u s t o 
believe tha t i t i s no t probabl e t o hav e th e 
formation o f latera l channel s i n thi s group . 
This woul d lea d th e specie s o f Giard i a 
duodenalis grou p t o attac h weakl y t o th e 
substrate. Suc h a  fact coul d explain the lack o f 
any mirror-imag e attachmen t o f th e striate d 
disk t o th e intestin e i n case s o f huma n 
biopsies11. 

Previous publication s di d no t provid e 
evidence o f ultrastructura l difference s betwee n 
Giard ia muri s an d Giard i u lambl i a 
t rophozoi tes 1 2 , althoug h K U L D A & 
N O R Y N K O V Á * i n a  revie w abou t Giardi a 
ultrastructure, hav e suggested that the marginal 
plates i n Giardi a intestinalis ar e les s developed 
than i n Giardi a muris. 

It i s wel l know n tha t th e taxonom y o f th e 
Giardia specie s i s stil l somewha t controversial . 

Three morphologica l differen t group s hav e 
been recognized among the species described by 
light microscope : Giardia agilis group whic h is 
found i n amphibians , Giardi a muri s an d 
Giardia duodenali s groups, which ar e found i n 
mammals, eac h havin g a  numbe r o f species 9. 
F I L I C E 4 define d thes e group s a s specie s bu t 
according t o K U L D A &  N O R Y N K O V Á * the y 
apparently represen t highe r tax . 

The ultrastructura l difference s betwee n 
Giardia muri s an d Giardi a duodenali s group s 
and th e similaritie s withi n eac h grou p o f 
Giardia, show n i n thi s paper , confir m thi s 
general tendenc y tha t poin t t o th e recognitio n 
of tw o morphologica l group s o f Giardi a i n 
mammals. Althoug h w e do  no t kno w i f thes e 
ultrastructural difference s hav e som e 
significance a t th e leve l o f species , w e can use 
the morphologica l feature  o f th e ventro-latera l 
flange as an auxiliaire morphologica l characte r 
to hel p a  differentia l diagnosi s among groups 
of Giardi a in favorabl e sections examined with 
electron microscope , even if th e host is infected 
by more  tha n on e type o f Giardia . 

The axeni c culture o f Giardi a duodenali s 
group obtaine d i n laborator y hav e permitte d 
the us e o f othe r method s beside s thos e 
morphological feature s t o stud y difference s o r 
similarities amon g isolate s o f Giardi a fro m 
different anima l species. However , these results 
have no t ye t bee n use d to systematiz e Giardia 
species9. 



R E S U M O 

Giardia muri s e  Giardia duodenalis : 
diferenças ultraestruturai s entre trofozoitos 

Neste trabalh o fo i analisada , atravé s d e 
Microscopia Eletrônic a d e Transmissão, a mor -
fologia d e trofozoitos de Giardia muri s obtido s 
de hamsters , rato s peridomiciliare s e  camun -
dongos, be m com o d e trofozoito s d e Giardi a 
duodenalis obtido s d e hamsters e  ratos perido -
miciliares. Basicament e a  ultraestrutur a do s 
trofozoitos estudado s fo i semelhante . Fora m 
observadas, no entanto, diferenças n a morfolo-
gia d a franj a ventro-latera l do s trofozoito s d e 
Giardia muri s quand o comparado s co m o s d e 
Giardia duodenalis , diferença s esta s relaciona-
das ao tamanho, arranj o da s lâminas marginai s 
e presença de lamel a osmiofílica . 

A C K N O W L E D G M E N T S 

This wor k wa s supported b y a  Grant fro m 
the Conselh o Naciona l d e Desenvolviment o 
Científico e  Tecnológic o ( C N P q , Proc . n ? 
403177/82) an d Fundaçã o d e Ampar o à 
Pesquisa do  Estad o d e Sã o Paul o ( F A P E S P , 
Proc. n ? 83/1428-7) . Th e authors ar e indebted 
to Prof . Fernand o Mott a d e Azeved o Corrê a 
for revisio n o f th e manuscrip t an d t o Mari a 
Aparecida M. Ramo s and Nivalde A . Bass o fo r 
technical assistance. 

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Recebido par a publ icaçã o e m 17 /2 /1989.