Parasite communities in eels of the Island of Reunion (Indian Ocean): a lesson in parasite introduction

Abstract

Eel populations from the small rivers on the Island of Reunion (French Overseas Department in the Indian Ocean) were investigated with respect to the occurrence and abundance of helminths during the autumn of 2005. The native species Anguilla marmorata (n = 80), Anguilla bicolor (n = 23), and Anguilla mossambica (n = 15) were studied. Six species of helminths were identified, four of them having a definitely nonnative status. Furthermore, unidentified intra-intestinal juvenile cestodes and extra-intestinal encapsulated anisakid nematode larvae were present in a few eels. We found that the invasive swim bladder nematode Anguillicoloides (Anguillicola) crassus had been introduced into the island. Six specimens were collected, four from A. marmorata, one from A. bicolor and one from A. mossambica. The maximum intensity of infection was two worms. The other helminths also showed a low abundance. These species were the monogenean gill worms Pseudodactylogyrus anguillae and Pseudodactylogyrus bini and the intestinal parasites Bothriocephalus claviceps (Cestodes), Paraquimperia africana (Nematodes), and the acanthocephalan Acanthocephalus reunionensis Warner, Sasal, and Taraschewski, 2007. The latter species, found as intra-intestinal immatures, is thought to utilize amphibians as required hosts; its status, introduced or native, could not be determined. P. africana was described from A. mossambica in South Africa and has not been recorded outside Africa. The other species are known from populations of European and American eels. However, A. crassus and the two Pseudodactylogyrus species originate from East Asia, where they are indigenous parasites of Anguilla japonica. Both an assignment test based on seven specific microsatellite loci and subsequent sequencing of mitochondrial haplotypes of a partial fragment of cytochrome c oxidase 1 strongly suggest that the A. crassus may originated around the Baltic Sea. According to the results presented here, populations of the indigenous eel species from Reunion can be considered to harbor extremely isolationist alien parasite communities. Our findings support the hypothesis that during the present time of global biological change, invasion by a nonnative species into a target island is more likely to reflect the political affiliation of the colonized environment and the pathways of trade and tourism than geographic proximity between donor and recipient areas or other natural circumstances.

Effects of metamorphosis timing and the larval growth rate on the latitudinal distribution of sympatric freshwater eels, Anguilla japonica and A. marmorata, in the western North Pacific

“…In the past three decades, dramatic declines in glass eel recruitment of temperate species like the American (Anguilla rostrata), European (Anguilla anguilla), Japanese (Anguil la japonica), and Australian (Anguilla australis) eels have raised concerns (Jellyman et al 2000;Hoyle and Jellyman 2002;Tatsukawa 2003;Dekker 2008;Richkus and Whalen 2000). The reasons for the declines are unclear but are probably due to reductions in spawning stocks Winter et al 2007;Clevestam et al 2011), overfishing Moriarty and Dekker 1997;Jellyman et al 2000;Hoyle and Jellyman 2002;Briand et al 2003;Chisnall et al 2003;Dekker 2003;Lin et al 2010), growth habitat and access reductions (Busch et al 1998;Haro et al 2000;McCleave 2001;McCleave and Jellyman 2004;Verreault et al 2004;Graynoth et al 2008), pollution (Amiard-Triquet et al 1988;Robinet and Feunteun 2002;Palstra et al 2006;van Ginneken et al 2009), swim bladder and gill parasites and viral infections (Haenen et al 2002;Szekely et al 2002;Kirk 2003;Sures and Knopf 2004;van Ginniken et al 2005;Han et al 2008Han et al , 2009aSasal et al 2008;Parker et al 2011), global climate change (Castonguay et al 1994;Kimura et al 2001;…”

Three new species of Pseudodactylogyrus (Monogenea: Pseudodactylogyridae) from Australian eels

“…Once the Pseudodactylogyrus infection became established in some parts of Europe, commercial movements of infected A. anguilla became another source of parasite invasion within other parts of Europe and elsewhere. There are also some unconfirmed sources of origin like P. anguillae infection of A. mossambica in South Africa (Christison and Baker 2007), P. bini and P. anguillae infection of A. mossambica and A. marmorata in the Island of Reunion (Sasal et al 2008), and P. anguillae infection of A. bicolor McClelland in Indonesia (K. Buchmann, Univ. of Copenhagen, Frederiksberg C, Denmark -pers.…”

Effects of Anguillicola novaezelandiae on the levels of cortisol and hsp70 in the European eel

“…It has quickly spread throughout the population of the European eel and is a much more invasive parasite than its congener A. novaezelandiae. It is currently known to be an alien parasite in five eel species (Anguilla anguilla, Anguilla rostrata, Anguilla bicolor, Anguilla marmorata, Anguilla mossambica; Johnson et al 1995;Moravec 2006;Neumann 1985;Sasal et al 2008). In Europe, A. crassus has a higher virulence and reaches significantly higher infection rates in terms of intensities and prevalence in its new host, the European eel, compared to the original host, the Japanese eel (Egusa 1979;Kennedy 2007).…”