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
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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?
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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
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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
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UNSATURATED NEUTRAL LIPIDS
Energetic metabolism
- long term alimentary use
- reproduction
- thermic isolation
= mostly triglycerides
Context of the study
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Context of the study
LIPOFUSCIN GRANULES
= Intracellular granulous pigments(in secondary lysosomes)
Fast accumulation : pathogenic
Oxydative catabolism of : - lipids- proteins- ascorbic acid- polyenic compounds
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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.)
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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
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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
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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
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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
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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
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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
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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
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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
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ConclusionConclusion
Parasitism = confounding factor ? Yes
But it depends of :
- parasite species
- infection intensity
- host gender
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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.