New species of Gyrodactylus von Nordmann, 1832 (Monogenoidea: Gyrodactylidae) from Gymnodiptychus dybowskii (Kessler, 1874) (Schizothoracinae) in the Kunes River (Yili River basin), China

Yili River system hosts a diverse fauna of fishes and parasites. Gymnodiptychus dybowskii is a rare and endangered aboriginal cold-water fish inhabit in the Yili river system. Our research identified a new species Gyrodactylus gymnodiptychi n. sp. isolated from G. dybowskii in the Kunes River (Yili River, China). Morphological comparison revealed identifiable differences between the new species and other parasites, including Gyrodactylus aksuensis, and Gyrodactylus tokobaevi, which are two known parasites living in G. dybowskii inhabit in the Aksu River west of Frunze (Kyrgyzstan), as well as Gyrodactylus montanus living in Shizothorax intermedius inhabited in the Tadzhikistan or Uzbekistan. Especially, the dorsal bar of G. gymnodiptychi n. sp. was raised at both ends with a hollow, and its hamulus roots were curved inward. The BLASTN search of GenBank did not detect any other ITS1-5.8S-ITS2 rDNA sequences same as G. gymnodiptychi's. Using the Bayesian Information and Maximum Likelihood methods to analyze the ITS1-5.8S-ITS2 rDNA gene sequences, we constructed phylogenetic trees for G. gymnodiptychi n. sp. Accordingly, our morphological and molecular research indicated that G. gymnodiptychi n. sp. was not only a new species of parasites but also the first Gyrodactylus member identified in the Yili River in China.

Neotropical sisterhood: new species of Gyrodactylus von Nordmann, 1832 (Platyhelminthes: Monogenea) infecting Rhamdia guatemalensis and Rhamdia laticauda (Siluriformes: Heptapteridae) in Mexico

We describe two new species of monogenean parasites of the genus Gyrodactylus von Nordmann, 1832 infecting Neotropical catfishes (Siluriformes) in southern Mexico: Gyrodactylus chulini n. sp. from 'chulín', Rhamdia laticauda collected in Oaxaca; and Gyrodactylus juili n. sp. from 'juil', Rhamdia guatemalensis from Veracruz. Morphologically, both new taxa are similar to Gyrodactylus spp. infecting catfishes (Siluriformes) in South America. Sequences of the internal transcribed spacers (ITS1-5.8S-ITS2 rDNA), the D2+D3 domains of the large ribosomal subunit (28S rDNA) and the cytochrome oxidase II (COII) gene were obtained from multiple parasite specimens and analysed using Bayesian inference. Phylogenetic hypotheses using ITS rDNA and COII genes, recovered two new Gyrodactylus species from Rhamdia spp.: G. chulini n. sp.; and Gyrodactylus juili n. sp., which are sister species to Gyrodactylus lilianae, a parasite of Rhamdia quelen in Brazil, and show strong affinity to other gyrodactytlids infecting Neotropical catfishes. This suggests that these new taxa, the first gyrodactylids described from Rhamdia spp. in Mexico, co-migrated to Tropical Middle America with their Neotropical catfish hosts, after the emergence of the Isthmus of Panama.

Transmission dynamics of ectoparasitic gyrodactylids (Platyhelminthes, Monogenea): An integrative review

Parasite transmission is the ability of pathogens to move between hosts. As a key component of the interaction between hosts and parasites, it has crucial implications for the fitness of both. Here, we review the transmission dynamics of Gyrodactylus species, which are monogenean ectoparasites of teleost fishes and a prominent model for studies of parasite transmission. Particularly, we focus on the most studied host–parasite system within this genus: guppies, Poecilia reticulata, and G. turnbulli/G. bullatarudis. Through an integrative literature examination, we identify the main variables affecting Gyrodactylus spread between hosts, and the potential factors that enhance their transmission. Previous research indicates that Gyrodactylids spread when their current conditions are unsuitable. Transmission depends on abiotic factors like temperature, and biotic variables such as gyrodactylid biology, host heterogeneity, and their interaction. Variation in the degree of social contact between hosts and sexes might also result in distinct dynamics. Our review highlights a lack of mathematical models that could help predict the dynamics of gyrodactylids, and there is also a bias to study only a few species. Future research may usefully focus on how gyrodactylid reproductive traits and host heterogeneity promote transmission and should incorporate the feedbacks between host behaviour and parasite transmission.

Species delimitation of Gyrodactylus (Monogenea: Gyrodactylidae) infecting the southernmost cyprinids (Actinopterygii: Cyprinidae) in the New World

The genus Gyrodactylus von Nordmann, 1832 represents one of the most diverse and widespread taxa within Monogenea, with approximately 500 species described worldwide. Thirty-three species of Gyrodactylus have been recorded in Mexico, and in the last two decades, at least 26 new species have been described mainly from freshwater fish families such as poeciliids, goodeids, profundulids, characids, and cichlids. In this study, we describe two new species of Gyrodactylus infecting freshwater cyprinids based on morphological and molecular characteristics. Gyrodactylus ticuchi n. sp. and Gyrodactylus tobala n. sp. were recovered from Notropis moralesi de Buen and N. imeldae Cortés, respectively, captured in five localities from the State of Oaxaca, Mexico. The new species differ slightly from their congeners in the morphology of the haptoral hard parts and the male copulatory organ. Sequences of the Internal Transcribed Spacers rDNA (ITS1-5.8S-ITS2), cytochrome oxidase subunit I (cox1), and the D2 + D3 domains of the large subunit (28S rDNA) were obtained from multiple specimens and analyzed using Maximum Likelihood (ML) and Bayesian Inference (BI). Phylogenetic hypotheses using ITS rDNA, cox1, and 28S rDNA genes recovered two new species of Gyrodactylus from N. moralesi and N. imeldae; we briefly discuss their phylogenetic relationship with other congeners. These gyrodactylids represent the first species described in species of Notropis from southern Mexico, the cyprinids exhibiting the southernmost distribution in the New World.

New Species of Gyrodactylus von Nordmann, 1832 from Native Fish from Chiapas, Mexico, Studied by Morphology and Molecular Analyses

BACKGROUND

Three new species of Gyrodactylus von Nordmann, 1832 are described from Poeciliopsis hnilickai and Tlaloc labialis (syn. Profundulus candalarius and Profundulus labialis) from the state of Chiapas, Mexico. Gyrodactylus chiapaneco n. sp. is described from T. labialis. Gyrodactylus guatopotei n. sp. was found to infect P. hnilickai. Gyrodactylus tlaloci n. sp. is described from T. labialis. The new species were characterised morphologically (haptoral hooks) and molecularly (sequences of the Internal Transcribed Spacer region (ITS1-5.8S-ITS2) of rDNA).

PURPOSE

During a survey in March 2017 in the state of Chiapas, individuals of Tlaloc labialis were collected by electrofishing from Arroyo Ojo de Agua and from Río Hondo, Ixtapa, Río Las Lajas and Poeciliopsis hnilickai from Río Hondo, Ixtapa and Río Cacao. Three new species of Gyrodactylus were found and are described herein based on morphological and genetic analysis.

METHODS

Attachment hooks were excised and partially digested with a proteolytic solution to remove tissue enclosing the haptoral armature. Measurements and pictures of the haptoral hard structures were taken and were compared with other Gyrodactylus species found on poeciliids and profundulids. The bodies from which haptoral hook were removed were stored individually in 95% ethanol at - 20 °C for molecular analyses. Sequences of the Internal Transcribed Spacer region of rDNA were obtained for each species and were compared with 26 Gyrodactylus spp. The genetic divergence among species of Gyrodactylus was estimated using uncorrected "p" distances with the program MEGA.

RESULTS

The haptoral hook of Gyrodactylus chiapaneco n. sp. are similar to G. poeciliae from Venezuela; those from Gyrodactylus guatopotei n. sp. resemble the sclerites of G. turnbulli from Singapore and G. pictae from Trinidad, and the haptoral hooks of Gyrodactylus tlaloci n. sp. are comparable to those of G. pseudobullatarudis and G. zapoteco from Mexico; most of these parasites were described from poeciliid fishes, except G. zapoteco which was recently described from Profundulus oxacae from Oxaca, Mexico. The sequences of the three new species were aligned with sequences of 26 other Gyrodactylus spp. Maximum likelihood and Bayesian inference analyses indicated that the three new taxa are members with well-supported lineages-the new taxa are the first species of Gyrodactylus to be described from Poeciliopsis hnilickai and Tlaloc labialis from Chiapas.

CONCLUSION

Gyrodactylus chiapaneco n. sp., Gyrodactylus guatopotei n. sp. and Gyrodactylus tlaloci n. sp. are described based on morphological and molecular analyses. Two of the three new species of Gyrodactylus described here, and both roughly fall morphologically and molecularly into the group of parasites harbouring slender marginal hooks: G. chiapaneco n. sp. and G. tlaloci n. sp. both possess marginal sclerites with slim shafts and group phylogenetically with other gyrodactylids of similar marginal hook morphology. Gyrodactylus guatopotei n. sp. groups with gyrodactylids possessing marginal hooks with quite elongated shafts, most of which have been found infecting poeciliids in the Antilles (e.g. G. pictae and G. turnbulli). Poeciliid, profundulid and goodeid fishes are morphologically and ecologically similar and nowadays live in sympatry or close geographical distance in Mesoamerica.