Influence of environmental factors on Argulus japonicus occurrence of Guangdong province, China

Argulus japonicus: A Concerning Health Issue for Channa punctata in Southwestern Bangladesh

OBJECTIVES

The prevalence and impact of the branchiuran copepod parasite Argulus japonicus on the snakehead fish Channa punctata were investigated in the southwestern region of Bangladesh.

METHODS

Parasitic infestation was examined to determine parasitological indexes including prevalence (%), mean intensity (MI), abundance (A), and index of infestation (IOI). Haematological parameters were also determined, along with morphological identification, clinical signs, and size grading of A. japonicus. In addition, histological alterations in the liver, kidneys, gills, and skin of C. punctata were examined.

RESULTS

Among 140 C. punctata individuals, 85 were found to be infested with a total of 245 A. japonicus parasites. Most of the parasites were located on the gill surfaces, around the eyes, and on the external parts of the body. The main physical features of A. japonicus were identified and documented during the observations. The haematological parameters showed variation across different experimental sites, and several clinical signs of infestation were observed. Four treatment methods for the elimination of A. japonicus were tested. Heat treatment (T3) was found to be the most effective method of the four.

CONCLUSION

This study highlights the serious health problems caused by A. japonicus infestation in C. punctata in southwestern Bangladesh.

Ornamental fish mortality reveals an old parasite introduction: A case study of Koi carp and fish louse

Koi carp are globally known for their colors and cultural significance. The introduction of these fish to new environments poses a threat to local biodiversity, in addition to releasing parasites, such as argulid ectoparasites. This study presents a record of Argulus japonicus infecting carp in an artificial lake in Southern Brazil using morphological and molecular methods, with a 100% prevalence (n = 3) and a mean intensity of 21.6 parasites per host, distributed over the body surface. The invasion history of hosts in the study locality indicates that the introduction of A. japonicus occurred decades before its first formal record in Brazil.

Complete Mitogenome sequencing of the fish louse Argulus japonicus (Crustacea: Branchiura): Comparative analyses and phylogenetic implications

The fish louse Argulus japonicus, a branchiuran crustacean of the Argulidae family, is attracting increasing attention because of its parasitic tendencies and significant health threats to global fish farming. The mitogenomes can yield a foundation for studying epidemiology, genetic diversity, and molecular ecology and therefore may be used to assist in the surveillance and control of A. japonicus. In this study, we sequenced and assembled the complete mitogenome of A. japonicus to shed light on its genetic and evolutionary blueprint. Our investigation indicated that the 15,045-bp circular genome of A. japonicus encodes 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), and 2 ribosomal RNAs (rRNAs) with significant AT and GC skews. Comparative genomics provided an evolutionary scenario for the genetic diversity of 13 PCGs: all were under purifying selection, with cox1 and nad6 having the lowest and highest evolutionary rates, respectively. Genome-wide phylogenetic trees established a close relationship between species of the families Argulidae (Arguloida) and Armilliferidae (Porocephalida) within Crustacea, and further, A. japonicus and Argulus americanus were determined to be more closely related to each other than to others within the family Argulidae. Single PCG-based phylogenies supported nad1 and nad6 as the best genetic markers for evolutionary and phylogenetic studies for branchiuran crustaceans due to their similar phylogenetic topologies with those of genome-based phylogenetic analyses. To sum up, these comprehensive mitogenomic data of A. japonicus and related species refine valuable marker resources and should contribute to molecular diagnostic methods, epidemiological investigations, and ecological studies of the fish ectoparasites in Crustacea.

Ecological study of Carassotrema schistorchis in wild silver carp, Hypophthalmichthys molitrix

Carassotrema schistorchis is a digenea parasite whose juvenile and adult stages parasitize the intestinal tract of definitive host fish. There is no available ecological information about this parasitic infection in wild host fish. The present work aimed to investigate the infection rate and distribution of C. schistorchis in wild silver carp, Hypophthalmichthys molitrix, and to assess the influence of environmental factors on infection by the parasite. From October 2016 to May 2019, a total of 554 wild silver carp were collected from two reservoirs. These collected fish were weighed, measured, and dissected to observe the presence of C. schistorchis following standard methodology. Ecological analysis results showed that the frequency distribution of C. schistorchis in the host population was aggregated distribution. The abundance of C. schistorchis exhibited a positive correlation with the host age and condition factor of silver carp, but it showed no relationship with water temperature, pH or DO. The condition factor value of infected fish was significantly higher than that of uninfected fish. These results indicated that food intake, not environmental factors, directly determined infection by the parasite in the host, indicating that an increased food intake would increase the risk of infection. Thus, the number of parasites could be used as an indirect biological marker for assessing the effectiveness of silver carp in filter-feeding on plankton. The following analysis indicated that silver carp with a body length of 50-55 cm showed the highest efficiency in controlling phytoplankton biomass. This study provides important information for understanding the ecology of C. schistorchis in wild silver carp.

Low levels of crustacean parasite infestation in fish species from the Matapi River in the state of Amapá, Brazil

Abstract This first study investigated the crustacean parasite fauna in 66 species of fish from the Matapi River basin, state of Amapá (Brazil). Fish were collected every two months between March 2012 and August 2013, encompassing dry and rainy seasons. Among the 66 species examined (corresponding to 722 fish specimens) only 11 species were parasitized. The infestation prevalence was 2.2%, and a total of 48 specimens of parasites were distributed between three different parasite groups. These included Argulus elongatus, Dolops reperta and Argulus multicolor (Branchiura), Ergasilus xinguensis and Gamidactylus sp. (Copepoda), and Isopoda (Braga patagonica), but branchiuran species were predominant. This was the first report of these parasite species for Leporinus fasciatus, Astyanax bimaculatus, Curimata incompta, Pygocentrus nattereri, Crenicichla cincta, Crenicichla johanna, Geophagus camopiensis, Pterophyllum scalare, Plagioscion squamosissimus, Hypostomus plecostomus and Propimelodus eigenmanni. Lastly, this study expands the range of occurrence of these six parasite species to the Matapi River basin in eastern Amazon.