Molecular Phylogeny of Congeneric Monogenean Parasites (Dactylogyrus): A Case of Intrahost Speciation

Abstract

Dactylogyrus species (Dactylogyridae: Monogenea) are a group of monogenean gill parasites that are highly specific to freshwater fish of the family Cyprinidae. Dactylogyrus species were sampled from 19 cyprinids and one percid collected in Europe. Using partial 18S rDNA and ITS1 sequences, a phylogeny of 51 Dactylogyrus species was reconstructed to investigate the patterns of parasite speciation and diversification. Three main Dactylogyrus lineages were recognized from all phylogenetic trees, that is, analysis of 18S rDNA alone and combined 18SrDNA and ITS1. The first lineage associates the Dactylogyrus species of Cyprinus carpio and Carassius auratus of the Cyprininae; the second associates Dactylogyrus species of the Gobioninae, Pseudorasbora parva of the Rasborinae, and Ctenopharyngodon idella of the Cyprininae; and the third associates Dactylogyrus species of the Leuciscinae and Alburninae and Barbus barbus of the Cyprininae. Our results suggest that the genus Dactylogyrus is of quite recent origin and that these three lineages separated from each other in a very short period of time. Host subfamily mapping onto the parasite tree inferred from analysis of the combined dataset showed that the Cyprininae could be plesiomorphic hosts for Dactylogyrus. Dactylogyrus parasites would have secondarily colonized the Percidae and representatives of the Leuciscinae, Alburninae, Gobioninae, and Rasborinae. Comparison of host and parasite phylogenetic relationships indicated that a very high number of parasite duplications occurred within two of the three Dactylogyrus lineages. Dactylogyrus diversification can be mainly explained by sympatric intrahost speciation events that seem to be correlated to strict host specificity. Moreover, the present study shows that the congeneric parasites speciating within one host tend to occupy niches within hosts differing at least in one niche parameter.

Reduced host-specificity in a parasite infecting non-littoral Lake Tanganyika cichlids evidenced by intraspecific morphological and genetic diversity

“…Genetic species identification of parasites was performed using three nuclear markers (28 S rDNA, 18 S rDNA, ITS-1) generally considered as suitable for monogenean species level determination5859. The length of the successfully sequenced 28 S rDNA fragment ranged from 641 to 747 base pairs (bp).…”

“…Phenotypic changes of haptoral sclerites have already been described in many previous studies and are supposed to be influenced by a combination of host characteristics7273 geographical origin74 and other environmental factors7778. While some researchers prefer the haptoral region for reconstructing evolutionary history2858, other investigations devote more attention to the reproductive organs7980. We found significant intraspecific differences in certain parts of the male copulatory organ between parasites collected from different host species.…”

Morphological and Molecular Evolution Are Not Linked in Lamellodiscus (Plathyhelminthes, Monogenea)

“…Within Platyhelminthes, which share a common origin of the parasitic lifestyle, the Monogenea is the only group in which an adaptive evolutionary radiation has occurred [51]. Because of their small body size and direct life cycle, monogeneans have an important potential for diversification [28]. Finally, the genus Lamellodiscus appears to be composed of more species with a wide host range than any other monogenean genera, which has been suggested to add some molecular variability [8] and potential for speciation [6], [52]–[54].…”

“…The 18S-ITS1 fragment was amplified in one round with primers L7 (forward, 5′-TGATTTGTCTGGTTTATTCCGAT-3′) and IR8 (reverse, 5′-GCTAGCTGCGTTCTTCATCGA-3′) as designed by Verneau and colleagues [27] and Šimková and colleagues [28] while COI was amplified with primers LCO1P (forward, 5′-TTTTTTGGGCATCCTGAGGTTTAT-3′) and HCox1P2 (reverse, 5′-TAAAGAAAGAACATAATGAAAATG-3′), after Littlewood and colleagues [29]. PCR were performed using the following cycles: 6 minutes at 95°C, then 35 cycles as follows: 1 minute at 95°C, 1 minute at 48°C, and 2 minutes at 72°C.…”

Co-Speciation of the Ectoparasite Gyrodactylus teuchis (Monogenea, Platyhelminthes) and Its Salmonid Hosts

“…a parasite species partly or fully switches to another host species, (ii) duplication, i.e. parasite speciation without host speciation (sometimes also referred to as intra-host speciation [7]), and (iii) lineage sorting, i.e. the extinction or the absence of a parasite lineage in the founding population of a new host species (“missing the boat”).…”