Description
by GUY BRUGEROLLE and JOHN J. LEE Diplomonads are small (less than 30 ~ m) unicellular heterotrophic flagellates which are free-living or parasitic in animals (Fig. 1). They are anaerobic or microaerophilic , and the cell has no mitochondria and although there may be Golgi function , there is no Golgi apparatus (dictyosome). The cell basically has a flagellar (mastigont) system with four basal bodies and flagella closely associated with one nucleus forming one karyomastigont in "monozoic forms" (Enteromonadinae) or two karyomastigonts in "diplozoic forms" (Diplomonadinae) (Fig. 1) . In each karyomastigont one flagellum is always directed backward and is generally associated with a ventral cytostome. The four basal bodies are arranged in two pairs and one basal body is generally located near a cup-like depression on the nucleus (Fig. 2a) . Three microtubular fibers originating from the basal body periphery have 11 2 6 DIPLOMONADIDA been distinguished : the supra-nuclear fiber above the nucleus, the infra-nuclear fiber under the nucleus and the cytostomal fiber 1. Cells with one or t along the recurrent flagellum. In genera forming with 1-4 flagell the Diplomonadinae such as Trepomonas, flagellum. Hexamita, Spironucleus, Octomitus, Giardia , the 2. Cells with two kary cell has two karyomastigonts arranged in an axia l forms") organized in a binary symmetry (Fig . 2b) . In these "diplozoic 3. Cup-like depression forms" the cell is like a double organism with two front of one basal bod nuclei , two sets of four flagella , two cytostomal associated microtubula apparatuses. They reproduce by longitudinal infra-nuclear, and binary fission and the mitosis is of the semi- fiber. opened type , the nuclear envelope persists and the 4. No Golgi , mitochon two hemi-spindles are extranuclear with axostyle . kinetochore microtubules penetrating into the nucleus by pores (Brugerolle, 1974) . They KEY TO SUB form resistant cysts which ensure the SUBFAMIL transmission in parasitic species . General description could be found in Grasse (1952) for light microscopy, Kulda and Nohynkova ( 1 9 7 8) for parasitic species of vertebrates and in 1. Monozoic organism ( Vickerman (1990) and Brugerolle (1991 a) for electron microscopy. mastigont) .... .... . .......... ...... .Fam The free-living species are found in water sites 1'. Diplozoic organism rich in organic matter and deficient in oxygen mastigonts) ... .... . such as sediments , stagnant reservoirs , marshes , ... ... ....... ...... water treatment plants , and also in brackish or salt water . They swim actively and feed on 2. With four flagella bacteria and also on dead cells of other protists , 2'. With three or less plants , and animals which are engulfed by the cytostomal apparatus. Information can be found 3. With three flagella in Klebs (1892) , Lemmerman (191 0) , Klug anterior flagella) ... (1936) , Grasse (1952) , Skuja (1956), Hanel 3' . With one flagellu (1979) , Brugerolle (1991 b) , Mylnikov (1985) , 1991 . 4. With two posterior The parasitic species are mostly found i n .. ...... .... .. .. . vertebrate intestine and cloaca, but they can 4'. With two posterior invade other organs and sometimes the blood . 4." No posterior oral Some species live in invertebrates such as . ... .... ..... . molluscs or insects . Most of them are endocommensal ; they generally feed on bacteria 5. Oral grooves con and on food digested by the host. Some are flagella .. . .. pathogenic such as Hexamita nelsoni in oysters 5'. Oral grooves with (Schlicht and Mackin , 1968) , Hexamita salmonis ..... ... ... ... in salmonid fishes (Becker, 1977) , Spironucleus 5" . Oral grooves with muris for mice , S. meleagridis in turkeys , or ..... .... ..... Giardia intestinalis in man . Species parasitic in vertebrates are dealt with by Kulda and 6. Flagella inserted o Nohynkova 1978. nuclei , endoplasm the cytostomal can Two suborders : the Enteromonadina with one 6'. Flagella inserted karyomastigont and the Diplomonadina with two no endoplasmic ret karyomastigonts arranged in axial binary canals .. .... .. symmetry (Fig . 1). Key Characters wo karyomastigonts , each a including a recurrent omastigonts ("diplozoic xial binary symmetry . on the nucleus surface in y and three basal body- r fibers : supra-nuclear , cytostomal or recurrent dria , hydrogenosomes, or ORDERS, FAMILIES, IES AND GENERA b 9<9 with a single karyo- . .......... Suborder Enteromonadina ily Enteromonadidae .... ...... .... ... 2 s (with two karyo- . ..... ... Suborder Diplomonadina ... . .. ... .... Family Hexamitidae .. .... .... .... .4 :.... .............. . Enteromonas flagella ...... ........ ..... ...... .. .. 3 (one recurrent and two .... ............... .......... .. Trimitus m ..... ...... .. .. ....... Caviomonas oral grooves (cytostomes) ....... ... .. ... ... ... ......... ... .. .. ..... .. ... .......... ... .5 cytostomal canals ... .... .... 6 groove or cytostomal pocket ... ....... ....... ..... ... ....... ........ .. .. ... .... ...... .7 taining three recurrent . .. . . .. . .. . . .. .. . .. .. . .. .. . .. .. .. Trepomonas only two flagella .. .... ... .. .. .. ... ..... ... .... ... ... .. ... .. ... Trigonomonas only one flagellum ... .. .. . . ... .............. ....... ..... .. ...... . Gyromonas n the external side of the ic reticulum associated with als .......... ..... ..... Hexamita at the apex , S-shaped nuclei , iculum associated with the ... ................ ........... Spironucleus DIPLOMON Hexamiti Trep omonas DIPLOMONADINA' Hexami '-.., -------- -- - - ----- ENTEROMONA CI NA 1999) one pole of the nucleus which presents a cup-like depressi mi crotubular fibers: supranuclear (s) , intranuclear (i), the cytostomal membrane . Fig . 2b . Organization of the t to the nuclei in "diplozoic" forms of diplomonads such as traverse the ce ll in two canals opened DIPLOMONAOIOA nae Giardii nae t a . . Qctom1tus ' Spi,onucleus/ I, ~ -------- ~~ ---------- ionary relationships of diplomonads (from Bruge ro ll e, rangement of the four basal bodies in two pairs close to on . The basal bodies are associated with three and cytostomal fiber (cy) ; a dense lamina (I) reinforces wo sets of basal bodies and associated fibers in relation Hexamita , where the two recurrent flagella (R,R') posteriorly . (fro m G. Brugerolle , 1991 a) 1128 DIPLOMONADI genera. Fig . 3a. Enteromonas : basal bodies at one pole of the nucleus (N) , base of the cytostoma l ridge (C) with the recurrent flagellum (R) . Fig. 3b. Trepomonas : cross section of the two opposed cytostomal pockets (C-C') containing three flagella. external face of the nuclei (N ,N') and recurrent flagella into cana ls (C ,C') lined by microtubular fibers (arrow) and endoplasmic reticulum (Er) . Fig. 3e,f. DA Spironucleus: flagella inserted near the anterior knob of the S-shaped nucleus (N). Recurrent flagella into cytostomal canals {C ,C') between the two nuclei (N ,N'). Fig . 3g . Octomitus : central axis with two recurrent axonemes , microtubular fibers , and endoplasmic reticulum. Fig . 3h. Giardia: cross section of the ventral disk (D) axoneme , and flagella (F) between the nuclei (N ,N') and median body (B) . Bars=1 J..lm. (from G. Brugerolle) DIPLOMO 7. Central axis formed by two recurrent axonemes, microtubular fibers endoplasmic reticulum : .......... .... .. Octomitus 7' . With a ventral disk: ..... ... ... ..... ... ... ...... G
Type species
Figures
No linked figures.
Raw text
by
GUY BRUGEROLLE and JOHN J. LEE
Diplomonads are small (less than 30 ~ m)
unicellular heterotrophic flagellates which are
free-living or parasitic in animals (Fig. 1).
They are anaerobic or microaerophilic , and the
cell has no mitochondria and although there may
be Golgi function , there is no Golgi apparatus
(dictyosome).
The cell basically has a flagellar (mastigont)
system with four basal bodies and flagella
closely associated with one nucleus forming one
karyomastigont in "monozoic forms"
(Enteromonadinae) or two karyomastigonts in
"diplozoic forms" (Diplomonadinae) (Fig. 1) .
In each karyomastigont one flagellum is always
directed backward and is generally associated
with a ventral cytostome. The four basal bodies
are arranged in two pairs and one basal body is
generally located near a cup-like depression on
the nucleus (Fig. 2a) . Three microtubular fibers
originating from the basal body periphery have
11 2 6 DIPLOMONADIDA
been distinguished : the supra-nuclear fiber
above the nucleus, the infra-nuclear fiber
under the nucleus and the cytostomal fiber 1. Cells with one or t
along the recurrent flagellum. In genera forming with 1-4 flagell
the Diplomonadinae such as Trepomonas, flagellum.
Hexamita, Spironucleus, Octomitus, Giardia , the 2. Cells with two kary
cell has two karyomastigonts arranged in an axia l forms") organized in a
binary symmetry (Fig . 2b) . In these "diplozoic 3. Cup-like depression
forms" the cell is like a double organism with two front of one basal bod
nuclei , two sets of four flagella , two cytostomal associated microtubula
apparatuses. They reproduce by longitudinal infra-nuclear, and
binary fission and the mitosis is of the semi- fiber.
opened type , the nuclear envelope persists and the 4. No Golgi , mitochon
two hemi-spindles are extranuclear with axostyle .
kinetochore microtubules penetrating into the
nucleus by pores (Brugerolle, 1974) . They KEY TO SUB
form resistant cysts which ensure the SUBFAMIL
transmission in parasitic species . General
description could be found in Grasse (1952) for
light microscopy, Kulda and Nohynkova ( 1 9 7 8)
for parasitic species of vertebrates and in
1. Monozoic organism (
Vickerman (1990) and Brugerolle (1991 a) for
electron microscopy. mastigont) .... .... .
.......... ...... .Fam
The free-living species are found in water sites 1'. Diplozoic organism
rich in organic matter and deficient in oxygen mastigonts) ... .... .
such as sediments , stagnant reservoirs , marshes , ... ... ....... ......
water treatment plants , and also in brackish or
salt water . They swim actively and feed on 2. With four flagella
bacteria and also on dead cells of other protists , 2'. With three or less
plants , and animals which are engulfed by the
cytostomal apparatus. Information can be found 3. With three flagella
in Klebs (1892) , Lemmerman (191 0) , Klug anterior flagella) ...
(1936) , Grasse (1952) , Skuja (1956), Hanel 3' . With one flagellu
(1979) , Brugerolle (1991 b) , Mylnikov
(1985) , 1991 .
4. With two posterior
The parasitic species are mostly found i n .. ...... .... .. .. .
vertebrate intestine and cloaca, but they can 4'. With two posterior
invade other organs and sometimes the blood . 4." No posterior oral
Some species live in invertebrates such as . ... .... ..... .
molluscs or insects . Most of them are
endocommensal ; they generally feed on bacteria 5. Oral grooves con
and on food digested by the host. Some are flagella .. . ..
pathogenic such as Hexamita nelsoni in oysters 5'. Oral grooves with
(Schlicht and Mackin , 1968) , Hexamita salmonis ..... ... ... ...
in salmonid fishes (Becker, 1977) , Spironucleus 5" . Oral grooves with
muris for mice , S. meleagridis in turkeys , or ..... .... .....
Giardia intestinalis in man . Species parasitic in
vertebrates are dealt with by Kulda and 6. Flagella inserted o
Nohynkova 1978. nuclei , endoplasm
the cytostomal can
Two suborders : the Enteromonadina with one 6'. Flagella inserted
karyomastigont and the Diplomonadina with two no endoplasmic ret
karyomastigonts arranged in axial binary canals .. .... ..
symmetry (Fig . 1).
Key Characters
wo karyomastigonts , each
a including a recurrent
omastigonts ("diplozoic
xial binary symmetry .
on the nucleus surface in
y and three basal body-
r fibers : supra-nuclear ,
cytostomal or recurrent
dria , hydrogenosomes, or
ORDERS, FAMILIES,
IES AND GENERA
b
9<9
with a single karyo-
. .......... Suborder Enteromonadina
ily Enteromonadidae .... ...... .... ... 2
s (with two karyo-
. ..... ... Suborder Diplomonadina ... .
.. ... .... Family Hexamitidae .. .... .... .... .4
:.... .............. . Enteromonas
flagella ...... ........ ..... ...... .. .. 3
(one recurrent and two
.... ............... .......... .. Trimitus
m ..... ...... .. .. ....... Caviomonas
oral grooves (cytostomes)
....... ... .. ... ... ... ......... ... .. .. ..... .. ... .......... ... .5
cytostomal canals ... .... .... 6
groove or cytostomal pocket
... ....... ....... ..... ... ....... ........ .. .. ... .... ...... .7
taining three recurrent
. .. . . .. . .. . . .. .. . .. .. . .. .. . .. .. .. Trepomonas
only two flagella .. .... ... .. ..
.. ... ..... ... .... ... ... .. ... .. ... Trigonomonas
only one flagellum ... .. .. . .
... .............. ....... ..... .. ...... . Gyromonas
n the external side of the
ic reticulum associated with
als .......... ..... ..... Hexamita
at the apex , S-shaped nuclei ,
iculum associated with the
... ................ ........... Spironucleus
DIPLOMON
Hexamiti
Trep omonas
DIPLOMONADINA' Hexami
'-..,
-------- -- - - -----
ENTEROMONA CI NA
1999)
one pole of the nucleus which presents a cup-like depressi
mi crotubular fibers: supranuclear (s) , intranuclear (i),
the cytostomal membrane . Fig . 2b . Organization of the t
to the nuclei in "diplozoic" forms of diplomonads such as
traverse the ce ll in two canals opened
DIPLOMONAOIOA
nae Giardii nae
t a .
. Qctom1tus
' Spi,onucleus/ I,
~ -------- ~~ ----------
ionary relationships of diplomonads (from Bruge ro ll e,
rangement of the four basal bodies in two pairs close to
on . The basal bodies are associated with three
and cytostomal fiber (cy) ; a dense lamina (I) reinforces
wo sets of basal bodies and associated fibers in relation
Hexamita , where the two recurrent flagella (R,R')
posteriorly . (fro m G. Brugerolle , 1991 a)
1128 DIPLOMONADI
genera. Fig . 3a. Enteromonas : basal bodies at one
pole of the nucleus (N) , base of the cytostoma l ridge
(C) with the recurrent flagellum (R) . Fig. 3b.
Trepomonas : cross section of the two opposed
cytostomal pockets (C-C') containing three flagella.
external face of the nuclei (N ,N') and recurrent
flagella into cana ls (C ,C') lined by microtubular fibers
(arrow) and endoplasmic reticulum (Er) . Fig. 3e,f.
DA
Spironucleus: flagella inserted near the anterior knob
of the S-shaped nucleus (N). Recurrent flagella into
cytostomal canals {C ,C') between the two nuclei
(N ,N'). Fig . 3g . Octomitus : central axis with two
recurrent axonemes , microtubular fibers , and
endoplasmic reticulum. Fig . 3h. Giardia: cross
section of the ventral disk (D) axoneme , and flagella
(F) between the nuclei (N ,N') and median body (B) .
Bars=1 J..lm. (from G. Brugerolle)
DIPLOMO
7. Central axis formed by two recurrent
axonemes, microtubular fibers
endoplasmic reticulum : .......... .... .. Octomitus
7' . With a ventral disk: ..... ... ... ..... ... ... ...... G