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
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
CONDiTIONS FOR INFECTION 1 st intermediate Presence of the upstream 2 nd intermediate
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
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
1 st intermediate Presence of the upstream Life span of cercariae? 2 nd intermediate Spatial discontinuity resolved by dispersion capacity
2 C 25 C Infection success (%) 15 C 2 C 25 C 2 25 3 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 2 6 8 Time (hr) is 4 1 4 2 12 5 1 15 Time (hr) o no td 2 D 6 5% mortality in 3 h Max. infectivity: 2 C, <1h
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)
In laboratory Light Darkness Controlled temperature 1 2 3. 12 21 22 23 24 Time (h) focus Emitted cercariae/ h
In laboratory 7 6 5 4 3 2 1 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
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 1998 1999 2 21 22 3 avril 4 td 12 16 mars 2 no 14 3 janvier o D 16 16 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
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
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 3:27 6 5 4 3 2 1 23 22 21 2 3 25 2 15 1 5 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 3:27 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 3:55 14 12 1 8 6 4 2 La Canelette TIME Water T ( C) 26 25 24 23 22 21 2 19 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 3:55 TIME Emersion TIME Luminosité Température de l eau de mer Microphallidae /1L H. quissetensis /1L
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)
Parasite abundance Theory Himasthla quissetensis No data Shell length (age) Age Experimental infection 25 2 15 1 5 1,5 2 4 6 8 1 12 14 Cockle size (mm)
Aug Aug Nov Dec Jan Feb Mar Apr May Oct Sep Jul Jul 35 3 25 2 15 1 5 3 25 2 15 1 5 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
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