BACKGROUND: The risks of fish-borne zoonotic trematodes (FZT) to human health constitute an important problem in Vietnam. The infection of humans with these trematodes, such as small liver trematodes (Clonorchis sinensis and Opisthorchis viverrini), intestinal trematodes (Heterophyidae) and others is often thought to be linked to fish culture in areas where the habit of eating raw fish is common. Juvenile fish produced in nurseries are often heavily infected with FZT and since fishes are sold to aquaculture facilities for growth, control of FZT in these fishes should be given priority. Controlling the first intermediate host (i.e., freshwater gastropods), would be an attractive approach, if feasible. The black carp, Mylopharyngodon piceus, is a well-known predator of freshwater snails and is already used successfully for biological control of snails in various parts of the world including Vietnam. Here we report the first trials using it for biological control of intermediate host snails in nursery ponds stocked with 1-week old fry (10–12 mm in length) of Indian carp, Labeo rohita. METHODS: Semi-field and field experiments were set up to test the effect of black carp on snail populations. In the semi-field experiment a known quantity of snails was initially introduced into a pond which was subsequently stocked with black carp. In the field trial in nursery ponds, density of snails was estimated prior to a nursing cycle and at the end of the cycle (after 9 weeks). RESULTS: The results showed that black carp affect the density of snail populations in both semi-field and field conditions. The standing crop of snails in nursery ponds, however, was too high for 2 specimens to greatly reduce snail density within the relatively short nursing cycle. CONCLUSIONS: We conclude that the black carp can be used in nursery ponds in Northern Vietnam for snail control. Juvenile black carp weighing 100 - 200g should be used because this size primarily prey on intermediate hosts of FZT and other studies have shown that it does not prey on fish fry of other species. It may be necessary to use a high stocking density of black carp or to reduce snail density in the nursery ponds using other measures (e.g. mud removal) prior to stocking fry in order for the black carp to keep the density of intermediate host snails at a very low level.
Both endotherms and ectotherms (e.g., fish) increase their body temperature to limit pathogen infection. Ectotherms do so by moving to warmer places, hence the term “behavioral fever.” We studied the manifestation of behavioral fever in the common carp infected by cyprinid herpesvirus 3, a native carp pathogen. Carp maintained at 24°C died from the infection, whereas those housed in multi-chamber tanks encompassing a 24°C-32°C gradient migrated transiently to the warmest compartment and survived as a consequence. Behavioral fever manifested only at advanced stages of infection. Consistent with this, expression of CyHV-3 ORF12, encoding a soluble decoy receptor for TNF-α, delayed the manifestation of behavioral fever and promoted CyHV-3 replication in the context of a temperature gradient. Injection of anti-TNF-α neutralizing antibodies suppressed behavioral fever, and decreased fish survival in response to infection. This study provides a unique example of how viruses have evolved to alter host behavior to increase fitness.
Jatropha curcas seeds are rich in oil and protein. The oil is used for biodiesel production. Jatropha seed cake (JSC) obtained after oil extraction is rich in protein; however, it is toxic (phorbol esters content 1.3 mg/g) and consists of 50-60% shells, which are indigestible. The principle of isoelectric precipitation was used to obtain Jatropha protein isolate (JPI) from JSC and it was detoxified (DJPI). Carp (n = 45, 20.3 ± 0.13 g) were randomly distributed into five groups with three replicates and for 12-week fed iso-nitrogenous diets (crude protein 38%): Control [fishmeal (FM)-based protein]; J(50) and J(75) (50% and 75% of FM protein replaced by DJPI); S(50) and S(75) (50% and 75% of FM protein replaced by soy protein isolate). Growth performance and nutrient utilisation parameters were highest in S(75) group and not significantly different to those in J(50) and S(50) groups but were significantly higher than those for all other groups. Similar trend was observed for protein and energy digestibilities of experimental diets, whereas opposite trend was observed for the feed to gain ratio. Activities of intestinal digestive enzymes did not different significantly between the five groups. In conclusion, DJPI is a good quality protein source for carp.
Objective To evaluate the physiological effect and response to noxious stimulation at five concentrations of MS-222 in koi (Cyprinus carpio). Study design Prospective experimental study. Animals Twenty-one healthy adult unknown sex koi fish weighing mean 450 ± SD 120 g. Methods Each fish was exposed to five different concentrations of MS-222 (50, 70, 110, 150 and 190 mg L(-1) ) in a random sequence during the same anaesthetic event. For each concentration of MS-222, vital functions such as heart rate (HR) (via Doppler) and opercular rate (OpR) were recorded after a standardized induction period. Response to two noxious stimuli in the form of haemostat clamp pressure applied on the tail and the lip was evaluated, and blood was drawn to measure biochemical and blood gas values. Results Decrease in response to noxious stimulation with an increase of MS-222 concentration both for the lip (p = 0.0027) and the tail (p < 0.0001) stimulus was observed. Biochemical values were unaffected by the concentration of MS-222 with the exception of lactate concentration which was weakly correlated with the duration of anaesthesia (r = 0.31, p < 0.001) and the number of times the fish was clamped or bled prior to sampling (r = 0.23, p < 0.001). Opercular rate decreased with the increase in anaesthetic concentration, and HR was not affected. Conclusions and clinical relevance Our results indicated a decrease in response to stimulus and a decrease in OpR that were associated with increased concentrations of MS-222. This may assist in establishing anaesthetic protocols using MS-222 in fish and supports the use of supramaximal pressure stimuli to teleost fish under variable MS-222 concentrations as a model for future studies.
Silver carp, Hypopthalmichthys molitrix is one of the most economically valuable fish species in Bangladesh. However, its production is often hindered by parasite-induced mortality. The present study reports the intensity of parasitic infestation in 216 specimens of H. molitrix collected from different fish markets in Rajshahi City, Bangladesh. Nine different parasite species (Trichodina pediculatus, Dactylogyrus vastator, Ichthyophthirius multifilis, Gyrodactylus elegans, Lernaea sp., Apiosoma sp., Myxobolus rohitae, Camallanus ophiocephali, and Pallisentis ophiocephali) were recovered from the gill, skin, stomach, and intestine of host fish. The highest level of infection was observed for host skin, while lower levels were observed for host gill, stomach, and intestine. The results also revealed that the intensity of parasite infection in different organs of H. molitrix varied with the season. In particular, the highest levels of infection were recorded during the winter period (November-February), when fish are most susceptible to parasites. The findings of the study will help in the management and conservation of H. molitrix.
Abstract Spring viremia of carp virus (SVCV) causes a highly contagious and serious disease of freshwater cyprinid fishes, generating significant economic and ecological impacts throughout the world. The SVCV is therefore listed as a notifiable pathogen by the International Organization for Animal Health. In June 2011, a significant mortality event of wild common carp Cyprinus carpio occurred in Minnehaha Creek near its confluence with Mississippi River Pool 2 in Minneapolis, Minnesota. Clinical signs of moribund fish included hemorrhagic lesions in the skin, eyes, and internal adipose tissue. The SVCV was isolated from pooled kidney and spleen of the fish. Rhabdovirus particles were seen upon examination of infected cell culture fluid by electron microscopy. The virus was confirmed to be SVCV subtype Ia by reverse transcription PCR and sequencing. This is the first report of SVCV within the state of Minnesota and the ninth documented case in North America. Received March 27, 2012; accepted July 2, 2012.
Iberian Leuciscinae have been used in many studies as models to explore topics such as hybridization, allopolyploidy, modes of reproduction, and evolution. This article focuses on the contribution of cytogenomics to foster research in this group of cyprinid fish. Conventional and molecular banding results were reviewed, facilitating comparative analysis between nase and chub taxa inhabiting Portuguese freshwaters. Hybridization is known to occur within both Chondrostoma s.l. and Squalius genera although polyploidy has only been reported in the latter; the reasons behind such differential genome flexibility remain unidentified. FISH tools allowed recognizing additional chromosome markers, confirming NOR polymorphism and distinguishing species and their hybrids. Recombination and genome instability were detected in homoploid and polyploid hybrid genomes supporting active NOR transposition. However, the multiplication of rDNAs in these species does not seem to be associated with Rex3 retroelement, though hybrids were not surveyed. CGH and GISH allowed reaffirming the hybrid origin of S. alburnoides and confirming that the conservative karyotype patterns within Iberian leuciscines are restricted to the macrostructure. Current data also support the usefulness of mapping repetitive DNAs, especially for nonmodel compact genomes with less variable karyotypes and sequence data resources unavailable, like in many cyprinid lineages. © 2013 S. Karger AG, Basel.
Human activities reduce biodiversity but may also drive diversification by modifying selection. Urbanization alters stream hydrology by increasing peak water velocities, which should in turn alter selection on the body morphology of aquatic species. Here, we show how urbanization can generate evolutionary divergence in the body morphology of two species of stream fish, western blacknose dace (Rhinichthys obtusus) and creek chub (Semotilus atromaculatus). We predicted that fish should evolve more streamlined body shapes within urbanized streams. We found that in urban streams, dace consistently exhibited more streamlined bodies while chub consistently showed deeper bodies. Comparing modern creek chub populations with historical museum collections spanning 50 years, we found that creek chub (1) rapidly became deeper bodied in streams that experienced increasing urbanization over time, (2) had already achieved deepened bodies 50 years ago in streams that were then already urban (and showed no additional deepening over time), and (3) remained relatively shallow bodied in streams that stayed rural over time. By raising creek chub from five populations under common conditions in the laboratory, we found that morphological differences largely reflected genetically based differences, not velocity-induced phenotypic plasticity. We suggest that urbanization can drive rapid, adaptive evolutionary responses to disturbance, and that these responses may vary unpredictably in different species.
Members of Candidia, Nipponcrysis, Parazacco, Opsariichthys, and Zacco are a group of East Asian freshwater fishes, and these five genera form a monophyletic group within the subfamily Oxygastrinae (Cypriniformes: Cyprinidae). In this study, we first determined complete mitogenomes of Candidia pingtungensis, Opsariichthys acutipinnis, O. chengtui, and Zacco acanthogenys. The four mitogenomes with the length of 16 611-16 615 bp displayed the same patterns in gene arrangements and the use of start and stop codons for protein-coding genes. Our phylogeny divided Candidia, Nipponcrysis, Parazacco, Opsariichthys, and Zacco into two major groups that the former three genera consisted of a group and the latter two genera formed another group. The phylogeny also revealed that C. pingtungensis was nested within Nipponcrysis. Our findings indicate that the taxonomy status of Candidia and Nipponcrysis is still needed to be confirmed.
Preservation of the genetic diversity of a local common carp in the agricultural heritage rice-fish system
- Proceedings of the National Academy of Sciences of the United States of America
- Published 8 months ago
We examined how traditional farmers preserve the genetic diversity of a local common carp (Cyprinus carpio), which is locally referred to as “paddy field carp” (PF-carp), in a “globally important agricultural heritage system” (GIAHS), i.e., the 1,200-y-old rice-fish coculture system in Zhejiang Province, China. Our molecular and morphological analysis showed that the PF-carp has changed into a distinct local population with higher genetic diversity and diverse color types. Within this GIAHS region, PF-carps exist as a continuous metapopulation, although three genetic groups could be identified by microsatellite markers. Thousands of small farmer households interdependently obtained fry and parental carps for their own rice-fish production, resulting in a high gene flow and large numbers of parent carps distributing in a mosaic pattern in the region. Landscape genetic analysis indicated that farmers' connectivity was one of the major factors that shaped this genetic pattern. Population viability analysis further revealed that the numbers of these interconnected small farmer households and their connection intensity affect the carps' inherent genetic diversity. The practice of mixed culturing of carps with diverse color types helped to preserve a wide range of genetic resources in the paddy field. This widespread traditional practice increases fish yield and resource use, which, in return, encourages famers to continue their practice of selecting and conserving diverse color types of PF-carp. Our results suggested that traditional farmers secure the genetic diversity of PF-carp and its viability over generations in this region through interdependently incubating and mixed-culturing practices within the rice-fish system.