Hitching Pseudoxiphophorus bimaculatus
Description
We studied flatworm parasites of the genus Gyrodactylus associated with twospot livebearer Pseudoxiphophorus bimaculatus both in this host’s native distribution in the Gulf of Mexico (Atlantic Ocean) versant, as well as in its invasive range across the continental divide, on the Pacific Ocean watershed. We surveyed 12 river basins, six on each slope of the continent, and recorded strongly overdispersed parasite distributions, both in terms of localities within basins and on fish hosts. Six gyrodactylid species were previously known to infect this poeciliid host, and we add five taxa to the list, three known and two undescribed species. From the 11 parasite species we characterized molecularly (cox 2 mDNA and ITS rDNA 43 sequences), 9–10 were recorded in river basins draining into the Atlantic, and only four in rivers flowing into the Pacific. Only one species, Gyrodactylus takoke, was recorded frequently on both sides of the country, and cox 2 haplotype networks suggest that parasites co-translocated with their fish hosts originated from the central Gulf of Mexico slope and successfully invaded two river basins draining into the Pacific. Our preliminary data do not allow proper testing, but we hypothesize that following the translocation of P. bimaculatus across the continental divide of Mexico, different types of host-parasite interactions (enemy release, spill-over and spill-back) may involve particular parasite species, some of which are known to be pathogenic
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Steps to reproduce
Hosts were captured using a SAMUS 725MP electrofishing device. Individual worms were placed in tubes with 96% ethanol for DNA extraction. The process was performed using the DNeasy Blood & Tissue Kit (Qiagen, California, USA) following the manufacturer's instructions. The ITS region of monogeneans parasites was amplified using primers BD1 and BD2 (Bowles and McManus, 1993; Bowles et al., 1995),as well as a partial region of the cox 2 gene using the primer pairs COX2F1 and COX2R1 (Xavier et al. 2015) with the Taq Platinum PCR kit (Invitrogen Co.) and a T100 thermal cycler (BIORAD). PCR products were sequenced by Sanger sequencing at Macrogen Corp. The resulting sequences were edited and assembled using GENEIOUS v8.1. Sequence alignment was performed with MEGA 12, and phylogenetic reconstructions were carried out using IQ-TREE v2.2.0 and MrBayes v3.2.