les interactions hôte-parasite en écotoxicologie : l’exemple des parasites de la dreissène en...
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Les interactions hôte-parasite en écotoxicologie : l’exemple des
parasites de la dreissène en tant que facteur confondant
Laëtitia MINGUEZ, Laure GIAMBERINI
LIEBE – Laboratoire Interactions Ecotoxicologie Biodiversité Ecosystèmes
CNRS UMR 7146
Journées ZAM10 et 11 Mai 2010
Context of the studyContext of the study
Ecotoxicology / Aquatic Ecology Parasitology
Environmental Parasitology
Important to determine combined effects of pollution and parasitism in ecotoxicological studies
Two questions: (1) Could parasites be indicators of environmental quality? (2) Could parasites modify biological responses of their hosts and interfere with bioindication procedures?
Could parasites modify biological responses of their hosts and interfere with bioindication procedures?
Test organism: The zebra mussel (Dreissena polymorpha)
Sentinel organism – more than 30 symbionts described
3 streams in France :
3 cellular biomarkers:
- the structural changes of the digestive lysosomal system
- the accumulation of neutral lipids
- the accumulation of lipofuscin granules
Context of the study
+ Condition and Gonadal indexes
Villaine
Moselle
Meuse
THE LYSOSOMAL SYSTEM
= Group of organelles (acid hydrolases)
- Intracellular digestion, reproduction, immune response, embryogenesis, cellular turnover, …
- Sequestration / accumulation of xenobiotics
Unspecific response to pollution
Context of the study
UNSATURATED NEUTRAL LIPIDS
Energetic metabolism
- long term alimentary use
- reproduction
- thermic isolation
= mostly triglycerides
Context of the study
Context of the study
LIPOFUSCIN GRANULES
= Intracellular granulous pigments(in secondary lysosomes)
Fast accumulation : pathogenic
Oxydative catabolism of : - lipids- proteins- ascorbic acid- polyenic compounds
MethodsMethods
Remaining tissuesDigestive gland excision
Cryosections -27°C (8µm)
Histochemical staining
Image analysis (5 fields / ind.)
Stereological parameters
Lysosomal β-glucuronidase (Cajaraville et al., 1991)
Unsaturated Neutral Lipids (Moore, 1988)
Lipofuscin granules (Moore, 1988)
Lysosomal: VvL, SvL, NvL, S/VL
Neutral lipids: SvNL
Lipofuscines: SvLF
Biomarker revelation
sections (5µm)
Hematoxylin/Eosin staining
Inventory of parasites + Gonadal index
Prevalence, Mean Intensity
Observation (30-40 sections / ind.)
Results and DiscussionResults and Discussion
Focus on bacteria and ciliates:
Rickettsiale-like organisms (RLO)
Ophryoglena spp.
-Intracellular bacteria-Digestive gland
-Ciliates-Digestive gland
Could it be sources of distortion in ecotoxicological studies ?
Previous study : Meuse vs Moselle (Sierck-les-Bains) (Minguez et al., 2009)
Study on the Moselle River: up- and downstream WSTP of Metz
Results - Discussion
Infection status = infected or not
Only station discrimination
Parasite species (Downstream)
Lysosomal system
Experimental groups: at least 5 organisms, gender
Ratio BM response infected / non-infected
-Differences between ♂ and ♀
-Coinfection: synergism between parasite species
♂ : synergism –
♀ : synergism +
The primary parasite in the study site turns biological responses (i.e. RLOs)
* : significant
RLOs and Ophryoglena
-80%
-60%
-40%
-20%
0%
20%
40%
60%
80%
oph M oph F rlo M rlo F oph-rlo M oph-rlo F
Lyso
som
al v
olum
e de
nsity
/con
trol
* *
*
*CoinfectionBacteriaCiliates
Phyllodistomum folium
Focus on two pathogenic trematodes:
Could it be sources of distortion in ecotoxicological studies ?
Bucephalus polymorphus
Molloy et al., 19975 mm
Results - Discussion
- Digenea
- ZM = the only intermediate host
- Gills Deformation
- Digenea
- ZM = 1st intermediate host
- Gonade Castration
Sporocyst
Vv L
(10
-4 µ
m3/µ
m3)
2
3
4
5
6
7
8
9
NI M NI F P. folium M P. folium F
a a
b
ab
Phyllodistomum folium
LYSOSOMAL SYSTEM and NEUTRAL LIPIDS
-♂ : no significant differences (trends)
-♀ : infection more developped lysosomal system and more lipid reserves
LIPOFUSCIN GRANULES
- Differences between ♂ and ♀
Results - Discussion
Sampling : Meuse river Prevalence rate = 4.8% (564 dissected mussels)-Males = 2 times more infected
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
NI M NI F P. folium M P. folium F
Sv L
F (
10-4 µ
m2 /
µm
3 )
a a
bb
♂ : oxidative stress
Vv L
(10
-4 µ
m3/µ
m3)
0
1
2
3
4
5
6
7
8
9
0 + ++ +++
Results - Discussion
Infection:
- Delay in gonad development (gonadal index: NI > I)
- Condition index: NI > I
and the infection intensity ??
+ : ≤ 5 sporocysts ++ : 5 < sporocysts ≤ 10 +++ : gills covered by sporocysts
Only for males
LYSOSOMAL SYSTEM
Tendency : Negative correlation between infection intensity and lysosomal system responses (lysosomes more and more numerous and smaller)
5 mm
Confounding factor in ecotoxicological monitoring
sensibility to environmental
conditions
Results – Discussion
Males:Females:
lysosome system,
lipidic reserves,
lipofuscin granules
lysosome system lipidic reserves lipofuscin granules
Better defenses More sensitive
( infection prevalence)
Parasite development or
Host’s eating behaviour modification( food intake)
Oxidative stress:Inflammatory processes
and/or antioxidant enzyme activities
vs
Bucephalus polymorphus
Sampling : Villaine river Prevalence rate = 1.9% (905 dissected mussels)
Studied Compartments : Lysosomes, Lipids, Lipofuscins
No significant differences between infected and non-infected organisms
Condition index: FW/(L*H*W)
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
NI B. polymorphus
Con
ditio
n in
dex
a
b
CI: Non-infected < Infected
Infection :
speed weight intake
Parasite = beneficial ??
Results – Discussion
FW: Fresh Weight L: shell Length
H: shell Height W: shell Width
Reproduction Reproduction
P. FoliumIn males
B. polymorphus
Results - Discussion
ReproductionParasite
DevelopmentGrowth MaintenanceGrowth MaintenanceGrowth Maintenance
Modification of the host’s energetic metabolism
Energy for reproduction used for parasite development
STRESS NO STRESS
Confounding factor Confounding factor
ConclusionConclusion
Parasitism = confounding factor ? Yes
But it depends of :
- parasite species
- infection intensity
- host gender
AcknowledgementsAcknowledgements
Studies supported by an EC2CO program and the CPER Lorraine- ZAM
ReferencesReferencesCajaraville, M.P., Marigómez, J.A., Angulo, E., 1991. Arch. Environ. Contam. Toxicol. 21, 395-400.Minguez, L., Meyer, A., Molloy, D.P., Giambérini, L., 2009. Environ. Res. 109, 843-850.Moore, M.N., 1988. Mar. Ecol. – Prog. Ser. 46, 81-89.