Cestodoses de l’avifaune camarguaise. Rôle d’ Artemia (Crustacea, Anostraca) et stratégies de rencontre hôte-parasite

Abstract

In a previous study dealing with the population dynamics of Artemiain the salt marshes of Carmargue (France), 4.5% of the crustaceanswere found to be infected with cysticercoids of cyclophyllidean tapeworms.These cysticercoids were respectively identified as F. liguloides,F. caroli, F. flamingo and Gynandrotaenia stammeri parsites of theflamingo (Phoenicopterus ruber); Hymenolepis stellorae a parasiteof the gull (Larus ridibundus) and Eurycestus avoceti, the definitivehost of which is the avocet (Recurvirostra avosetta). For three species(H. stellorae, F. flamingo and G. stammeri) the intermediate hosthad not yet identified. The adults, except those of F. caroli werefound in the gut of flamingos and gulls. The morphological adaptationsof the eggs to the environment and the simultaneous infection ofArtemia towards the different species of cestodes which all are parasitesof birds are proposed as being an important meeting strategy betweenhosts and parasites. The presence of F. liguloides cysticercoidsis accompanied by changes in pigmentation associated with behaviouralmodifications of the parasitized host, Artemia. These modificationshave repercussions on the recruitment of different species of cestodes:-by a global increase in the vulnerability of Artemia infected byF. liguloides, -in the case of simultaneous parasitism by cysticercoidsof F. liguloides and of other uncommon cestode species, such as F.flamingo (A = 0.743.10-3), G. stammeri (A = 0.031.10-3), H. stellorae(A = 0.077.10-3) and E. avocetti: If the second species is the parasiteof the flamingo it will suffer the loss of a portion of its infestingstages that will not reach their definitive hosts. This loss maybe compensated by spatial partitioning by different bird speciesand by the existence of several intermediate host species. This studyhighlights both the complexity of interspecific relationships inthe colonization and exploitation of host populations by cestodesand the importance of resource partitioning by various bird speciesin the circulation of the parasites. Whatever the particular consequencesmay be for each parasite population, the modifications induced inArtemia by F. liguloides constitute a determining factor in the infestationstrategies of avian cestode parasites in Camargue.