Biological Invasion of Fish Parasite Neoergasilus japonicus (Harada, 1930) (Copepoda: Ergasilidae) in Lake Grand Laoucien, France: A Field Study on Life Cycle Parameters and Reasons for Unusual High Population Density

The fish parasite, Neoergasilus japonicus (Harada, 1930), native to Eastern Siberia and the Amur River catchment area, invaded European water bodies in the middle of the last century, possibly due to the human-mediated distribution of fish in the Amur complex (i.e., the genera Hypophthalmichthys and Ctenopharyngodon). In the deep karst lake, Grand Laoucien (Marseille area, France), this species had an unusually high population density (from 1000 ind./ m3 in zooplankton to 4000 ind./ m3 in the nearshore area) during the free-living period of its life cycle. The annual cycle of N. japonicus includes a 5-month overwintering of fertilized females attached to fish fins and, following this, a five- to six-generation chain from March to November, when the free-living stages in the population alternate with parasite females which attach to their hosts for breeding. The population density of the parasites in zooplankton increased exponentially from spring to autumn, which positively correlated with temperature. We found a strong correlation between N. japonicus density and the community development of microphytobenthos, but not between N. japonicus and phyto- or zooplankton dynamics. The local contributing factors included a seasonal three-fold decrease in water levels and the development of anoxia in profundal waters, which led to a high ambient fish density and thus susceptibility to the parasite. Although the free-living parasite represented only 1% of zooplankton production, it consumed up to 25% of small invertebrate productivity. The maximum intensity of infection reached 140 parasites per fish, or 4.14 per g of weight. The high infection of fish with this parasite, in our opinion, indicated the danger it poses to the local ichthyofauna, which first encountered this new parasite.

ZOOPLANCTON (CLADOCERA Y COPEPODA) DE LA LAGUNA DE CAJITITLÁN

Cladocerans and copepods are the main zooplankton formers in freshwaters. The actual state of pollution faced by the lagoon of Cajititlán restricts the amount of species able to habit this water body, and with it, the functionality of the ecosystem due to their role as phytoplankton consumers and as the principal food source for fishes and other organisms. Until now, there was very little knowledge about these groups in the lagoon, which is because of the lack of specialists in the occidental region of Mexico and the inherent difficulties with respect to the manipulation of these organisms (their size round between 0.2 to 4 mm, besides, manual dissections must be done in order to observe taxonomic characters). In this study, we analyze the composition and abundance of the zooplankton in Cajititlán Lagoon focused in both groups (Cladocera and Copepoda). To achieve this objective, five sites within the lagoon were chosen based on their position with respect to the principal human populations. Samples were collected using a plankton net of 63 μm mesh light with one horizontal tow-in each site monthly. The analyzed period comprehends from May 2015 to April 2016, completing an annual cycle. Each sample was fixed using 4 % formaldehyde. Organisms were first identified the species level and their abundance was calculated with manual counts using a Bogorov chamber. Six species were recorded: Daphnia ambigua and Diaphanosoma birgei (Cladocera) and Arctodiaptomus dorsalis, Leptodiaptomus siciloides, Mesocyclops edax and Neoergasilus japonicus (Copepoda). The most abundant and frequent species was A. dorsalis, followed by M. edax and D. ambigua. Leptodiaptomus siciloides and N. japonicus appeared to be rare species, but L. siciloides was very abundant in March and April. The most abundant species was A. dorsalis, occurring nearly in 77 % of the samples and an average of 5 organisms per liter (up to 60 org/l), while the most frequent was M. edax, with up to 87 % of occurrences and an average of 3 org/l (up to 80 org/l). The general abundance of both groups in this water body was below and the species composition corresponds to the expected in an eutrophicated waterbody.

Metazoan parasite communities of three endemic cichlid fish species from the upper Grijalva River, Chiapas, Mexico

SummaryWe recorded the metazoan parasite communities in three endemic cichlids (Chiapaheros grammodes, Vieja breidohri and V. hartwegi) collected between November 2008 and July 2009 in the upper Grijalva River Basin (GRB), Chiapas, Mexico. In total, 6,287 individual parasites belonging to 18 taxa (1 monogenean, 6 digeneans, 1 cestode, 4 nematodes, 2 acanthocephalans, 1 hirudinean, 2 copepods and 1 pentastomid) were found. Eleven metazoans were adult forms and 7 larvae; moreover, 14 were endoparasites and 4 ectoparasites. Sixteen parasite taxa represent new geographical and host records. The helminth community in the three cichlids was characterized by higher number of generalists than specialists, as well as a higher proportion of autogenics than allogenics. The metazoan parasites showed prevalence and mean abundances moderate to high. The infracommunities and component community of metazoan parasites had low diversity, richness, and number of individuals and are similar to those reported for other cichlids in Southeastern Mexico, characterized by the presence of typical parasites of cichlids, with a high number of digeneans and generalist parasites. We report the introduced Asian parasitic copepod Neoergasilus japonicus parasitizing endangered or threatened endemic cichlids in the upper GRB. This copepod have been widespread in other freshwater fish species, mainly in Asia (China, India, Japan, Russia, Taiwan), Europe (France, Hungary, Italy, Turkey), and America (Cuba, Mexico, Peru, United States).

A Study of Parasitic Copepod Infesting Two Freshwater Fish Populations (Cyprinus carpio and Abramis brama) from Beni-Haroun Dam (Mila) North-East of Algeria

Copepods are one of the main fish ectoparasites, commonly known among the parasitism world, due either to their special adaptive capacity or to induce stress in aquatic organisms, as well as the parasitism result is overall a physiological rate affecting the survival of host. This study was, therefore, aimed to investigate the ectoparasite copepods, infesting 277 fishes including 135 of Cyprinus carpio (Linnaeus, 1758) and 142 of Abramis brama (Linnaeus,1758), collected from Beni-Haroun dam (Mila, northeast Algeria). The fishes were subjected to some morphometric measurements and gill dissections and the harvested parasites were afterwards stored and identified. The parasitic indices were determined to examine the effect of size, sex, season and microhabitat on the parasitic infestation by using χ2 test. The gill examination of individuals of the two host fishes led to harvest 135 copepods, including 127 individuals from Cyprinus carpio belonging to five species (Ergasilus sieboldi, Ergasilus briani, Neoergasilus japonicus, Neoergasilus longispinosis and Lernaea cyprinacae) and 8 individuals from Abramis brama belonging to the two species: Ergasilus sieboldi and Ergasilus briani, and hence Cyprinus carpio is the most infested species than Abramis brama. This study also revealed that the parasitic index values were high in C. carpio (P=53.00%; A=3.7; I=6.93) compared to A. brama (P=12,0.5%, A=0.12, I=1.00) during autumn, since no effect on infestation was noticed during winter. The statistical analysis has revealed the effect of season on parasitic copepod infestation in the two fish species (χ2Obs =30,959 > χ20.05 = 7,815, ddl =3), Since there was no effect due to the microhabitat and sex.

FIRST RECORD OF Neoergasilus japonicus (HARADA, 1930) (COPEPODA: CYCLOPOIDA) INFECTING A FISH SPECIES IN SOUTH AMERICA

The parasitic copepod Neoergasilus japonicus (Harada, 1930), native to eastern Asia, was collected from Colossoma macropomum (Cuvier, 1818) cultivated in a fish pound in the department of San Martin, Peru in July 2017. The parasite specimens were found attached to the base of the dorsal fin. Neoergasilus japonicus is widespread in different fish species across the world, being in this study recorded for the first time parasitizing a fish in South America. It is probably that exotic fish hosts associated with the fish-culture industry, such us the tilapia, is the responsible for the transportation and introduction into this part of the world.