From a host to the other: the critical role of the short cercariae stage

Transcription

1 Programmes : PNEC TAIPAMOR, Carlsberg Fundation From a to the other: the critical role of the short cercariae stage de MONTAUDOUIN 1 X., DESCLAUX 1 C., JENSEN 2 K.T. 1 Laboratoire d'océanographie Biologique, UMR 585 Université Bordeaux 1 - CNRS, 2 Rue du Prof. Jolyet, F-3312 Arcachon, FRANCE 2 Department of Marine Ecology, Institute of Biological Sciences, University of Aarhus, Finlandsgade 14, DK-82 Aarhus, DENMARK Himasthla quissetensis Nassarius reticulatus Cerastoderma edule

2 DIGENEAN PARASITE LIFE CYCLE : Example of Himasthla quissetensis 2 nd intermediate 1 st intermediate Free-larvae stage Predation Free-larvae stage Cercariae Adult Final Miracidia Fèces Metacercariae

3 CONDiTIONS FOR INFECTION 1 st intermediate Presence of the upstream 2 nd intermediate

4 Presence of the upstream % infected snails % infected snails 2 % 1 5 % 1 % 5 % % 2 % 1 5 % 1 % 5 % % ARGUIN A r g u i n O c t N o v D e c J a n F e b M a r A p r M a y J u n H. quissetensislepocreadiidae Microphallidae Schistosomatidae sporocysts Zoogonidae 1 % prevalence for adult cockles 3 median parasite abundance in cockles CANELETTE C a n e l e t t e O c t N o v D e c J a n F e b M a r A p r M a y J u n 1 % prevalence for adult cockles 9 median parasite abundance in cockles

5 Cercarial dispersion potentiality d=1 m U=6 cm s -1 u * =.3 cm s -1 3 x 3 15 Cockle infection after 2 hrs run : Still water,d=m: 94 % prevalence, 63 % encysted cerc. cockle -1 Run. water,d=1m: 93 % prevalence, 59 % encysted cerc. cockle -1

6 1 st intermediate Presence of the upstream Life span of cercariae? 2 nd intermediate Spatial discontinuity resolved by dispersion capacity

7 2 C 25 C Infection success (%) 15 C 2 C 25 C ho 1 ra ut 15 C Survivorship (%) 1 ho riz at io n Cercarial lifespan (and potential of infectivity) 8 ta ut 8 ith ou 6 in at e w 4 se m Time (hr) is Time (hr) o no td 2 D 6 5% mortality in 3 h Max. infectivity: 2 C, <1h

8 1 st intermediate Presence of the upstream Conditions for cercariae emission: temperature and light? Spatial discontinuity resolved by dispersion Infectivity tidal cycle duration (12 hours) 2 nd intermediate Role of temperature (max around 2 C)

9 In laboratory Light Darkness Controlled temperature Time (h) focus Emitted cercariae/ h

10 In laboratory light darkness 15 C 17 C 19 C 2 C 22 C 23 C 26 C Mean number of emitted cercariae / h T1 T2 T3 T4 T5 T6 T7 T8 T9 T1 T11 T12 T13 T14 T15 T16 T17 T18 T19 T2 T21 T22 T23 T24 Maximum emission: 19-2 C Emission occurs during night, when snails are active and at the surface of the sediment

11 24 juillet 9 juin 25 avril 11 mars 25 janvier 11 décembre 27 octobre 12 septembre 29 juillet 14 juin 8 in at se m 6 is 1 e ra ut ho ut ta ou ith w avril 4 td mars 2 no 14 3 janvier o D décembre 1 novembre Mean number of H. quissetensis cercariae per cockle Abondance d'infestation moyenne en H. quissetensis (+ES) ho riz at io n In the field January: 15 stained cockles, free of parasites, are transplanted in a site where infection is known

12 at io n In the field ra ut ho riz Sieves in at e w Pump ith ou ta ut ho Colonne d eau filtrée td is se m Colonne d eau D o no Vacuum cleaner Aspiration Filtration 3 µm sédiment

13 In the field 1 1 1,1 1 Arguin TIME Mean number of cercariae / 1L eau Emersion Light intensity (mv) 17:24 17:4 19:26 21:25 21:45 22:25 23:2 23:29 :18 1:15 1:23 2:19 3:17 3: :24 17:4 19:26 21:25 21:45 22:25 23:2 23:29 :18 1:15 1:23 2:19 3:17 3:27 14:4 14:5 16:2 17:4 17:5 18:15 19:4 19:5 21:15 22:5 23: :35 1:4 1:5 2:2 2:45 2:55 3:2 3:45 3: La Canelette TIME Water T ( C) :4 14:5 16:2 17:4 17:5 18:15 19:4 19:5 21:15 22:5 23: :35 1:4 1:5 2:2 2:45 2:55 3:2 3:45 3:55 TIME Emersion TIME Luminosité Température de l eau de mer Microphallidae /1L H. quissetensis /1L

14 1 st intermediate Presence of the upstream Conditions for cercariae emission: temperature and light Spatial discontinuity resolved by dispersion Infectivity tidal cycle duration (12 hours) Role of temperature (max around 2 C) 2 nd intermediate Role of temperature (max around 2 C) Shell length (age)

15 Parasite abundance Theory Himasthla quissetensis No data Shell length (age) Age Experimental infection , Cockle size (mm)

16 Aug Aug Nov Dec Jan Feb Mar Apr May Oct Sep Jul Jul Old cohort young cohort Nov Dec Jan Feb Mar Apr May Oct young cohort Old cohort Sep Mean abundance per cockle Shell length mm Shell length: Infection: x4

17 Conclusions and perspectives Several factors are involved in the transmission of digenean parasites between the first and the second intermediate. Although temperature seems to be a primary controlling factor, it is possible that the metabolism of s in relation with environmental factors is the real key-factor (Poster p99 Parasite communities in cockles (Cerastoderma edule) along a latitudinal gradient (North Africa to Scandinavia): pattern and processes ) Macroparasites are not the only pathogen agents and interaction with microparasites are probable (Posters: P1 Coinfection of two sympatric bivalves, the manila clam (Ruditapes philippinarum) and the cockle (Cerastoderma edule) along a latitudinal gradient P12 Cockle s parasitism by digenean trematods and bacteria: a possible interaction ) These studies are part of the Carlsberg project and the PNEC project: Transversal Action : Impact of Parasitism on Marine Organisms, modulation by environmental factors (TAIPAMOR). Coord.: Ch. Paillard