鱼类三代虫研究进展

三代虫是一类常见的鱼类体表寄生虫,广泛寄生于各种鱼类,其危害近年有加剧之势,对鱼类养殖业造成较大威胁。本文从三代虫的分类方法、种群动态和引起寄主免疫反应等方面综述了鱼类三代虫研究现状及发展趋势。     

鱼类三代虫分子生物学的研究进展

三代虫是一类常见的鱼类体外寄生虫,绝大多数种类寄生于鱼类的体表和鳃,大量寄生可导致苗种甚至成鱼大批死亡,或引起其他病原感染而致继发性鱼病,造成严重的经济损失.本文从三代虫目前的分类学概况、DNA分类学和条形码技术、核糖体基因及线粒体基因的研究等方面概述了鱼类三代虫分子生物学的研究现状,为三代虫及扁形动物的分子生物学研究及其应用提供有用的资料.     

Development of tea tree oil-loaded liposomal formulation using response surface methodology

Abstract

The aim of this study is to prepare tea tree oil liposome (TTOL) and optimize the preparation condition by single factor experiment and statistical design. TTOL was prepared using a thin-film hydration with the combination of sonication method and the preparation conditions of TTOL were optimized with response surface methodology (RSM). The optimal preparation conditions for TTOL by response surface methodology were as follows: the mass ratio of PC and Cho 5.51, TTO concentration 1.21% (v/v) and Tween 80 concentration 0.79% (v/v). The response surface analysis showed that the significant (p?<?0.05) second-order polynomial regression equations successfully fitted for all dependent variables with no significant (p?>?0.05) lack of fit for the reduced models. Furthermore, the interaction of the mass ratio of PC/Cho and TTO concentration had a significant effect. The amounts of Tween 80 required were also reduced with RSM. Under these conditions, the experimental encapsulation efficiency of TTOL was 97.81?±?0.33%, which was close with the predicted value. Therefore, the optimized preparation condition was very reliable. The increased entrapment efficiency would significantly improve the TTO stability and bioavailability.     

Two new species of Gyrodactylus von Nordmann, 1832 (Monogenea: Gyrodactylidae) parasitizing Girardinichthys multiradiatus (Cyprinodontiformes: Goodeidae), an endemic freshwater fish from central Mexico

Gyrodactylus mexicanus n. sp. and Gyrodactylus lamothei n. sp. are described from the fins and skin of Girardinichthys multiradiatus, an endemic freshwater fish from central Mexico. Gyrodactylus mexicanus is compared to other Gyrodactylus species that parasitize Fundulus spp., the phylogenetically closest group to the Goodeidae from North America. Gyrodactylus mexicanus is distinguished by having large anchors with well-developed superficial roots, enlarged hooks with a proximally disrupted shank (ligament), and a ventral bar with 2 poorly developed anterolateral projections and a small medial process. Gyrodactylus lamothei is distinguished from G. mexicanus and from other species of Gyrodactylus on the North American continent by having anchors with a sclerite on the superficial root and robust hooks with a straight shaft and a recurved point.     

Feeding complementarity versus redundancy among herbivorous fishes on a Caribbean reef

Herbivory is an important driver of community structure on coral reefs. Adequate understanding of herbivory will mandate better knowledge of how specific herbivores impact reef communities and the redundancy versus complementarity of their ecological roles. We used algal communities generated by herbivore manipulations to assess such roles among Caribbean herbivorous fishes. We created large enclosures on a 16- to 18-m-deep reef to create treatments grazed for 10 months by: (1) only Sparisoma aurofrenatum, (2) only Acanthurus bahianus, (3) no large herbivorous fishes, or (4) natural densities of all reef fishes. After 10 months, we removed cages and filmed how free-ranging reef fishes fed among these treatments that differed in algal community structure. In general, Acanthurus spp. and Scarus spp. rapidly grazed exclosure and Sparisoma-only treatments, while Sparisoma spp. preferentially grazed exclosure and Acanthurus-only treatments. These patterns suggest complementarity between Sparisoma spp. and both Acanthurus spp. and Scarus spp. but redundancy between Acanthurus spp. and Scarus spp. Despite these generalities, there was also within-genera variance in response to the different treatments. For example, large Scarus spp., such as Scarus guacamaia, fed more similarly to Sparisoma spp., particularly Sparisoma viride, than to other Scarus spp. Moreover, the three common Sparisoma species differed considerably in the macroalgae to which they exhibited positive or negative relationships. Thus, herbivorous reef fishes vary considerably in their response to different algal communities and exhibit complex patterns of compensatory feeding and functional redundancy that are poorly predicted by taxonomy alone.     

Parasitic infections in freshwater ornamental fish in Sri Lanka

A total of 1520 ornamental fish of 13 species from 26 export farms in Sri Lanka were collected between October 1999 and March 2000 and examined for parasites. Fish species examined were guppy Poecilia reticulata, goldfish Carassius auratus, platy Xiphophorus maculatus, molly Poecilia sphenops, angel Pterophyllum scalare, swordtail Xiphophorus helleri, tetras Hyphessobrycon species, barbs Capeota and Puntius spp., gourami Colisa sp., carp Cyprinus carpio, fighters Betta spelendens and others (Brachydanio and Astronotus spp.). Nine species of monogenean trematodes (Dactylogyrus extensus, Dactylogyrus cf. extensus, D. vastator, Dactylogyrus cf. vastator Dactylogyrus spp., Gyrodactylus turnbulli, G. katherineri, Gyrodactylus cf. katherineri, Gyrodactylus spp.), 7 protozoan species (Trichodina nigra, Trichodina spp., Tetrahymena corlissi, T. pyriformis, Ichthyophthirius multifiliis, Ichthyobodo necator, Piscinoodinium spp.), 3 species of copepod arthropods (Lernaea cyprinacea, Ergasilus ceylonensis, Argulus foliaceus), 1 metacercarial stage of a digenean trematode (Centrocestus spp.) and 1 nematode (Capillaria spp.) were identified. Parasites were found in fish from 23 of the 26 farms with an overall prevalence of parasitism in 45.3% of fish. The variation in farm prevalence among different parasites was significant (p < 0.01). Fish infection rates with monogenean trematodes, protozoans, copepod crustaceans, digenean trematodes and nematodes were 28.3, 18.4, 4.8, 0.8 and 0.4%, respectively. In all, 50 out of 590 (50/590) guppies were infected with Tetrahymena, compared with 13/930 for all other species, which is a statistically significant result (p < 0.01). Similarly, 13/44 and 18/44 carp were infected with Argulus foliaceus and Lernaea cyprinacea, compared with 7/1476 and 15/1476, respectively, for all other species combined (p < 0.01). Capillaria spp. was found only in guppies (4/590) and angel fish (3/92) while Centrocestus spp. was found in goldfish (12/153) only.     

Shrimps remove ectoparasites from fishes in temperate waters

We have found that two very common species of North Atlantic shallow water shrimp, Palaemon adspersus and Palaemon elegans, remove and feed on ectoparasites on plaice (Pleuronectes platessa L.). The relationship could be mutualistic, as we did not observe any attempts by the fishes to feed on the shrimps. The ectoparasites removed included monogenean worms (Gyrodactylus sp.) and sea lice (Lepeophtheirus pectoralis). An experiment showed that there were 65% more Gyrodactylus parasites on the fishes that had been apart from compared with those that had been together with shrimps for 48h. Shrimps on coral reefs are known for cleaning fishes, but that shrimps in temperate waters show parasite-cleaning behaviour is, to our knowledge, a new observation.     

Infections of Gyrodactylus bullatarudis and Gyrodactylus turnbulli on guppies (Poecilia reticulata) in Trinidad.

Gyrodactylus bullatarudis Turnbull, 1956, and Gyrodactylus turnbulli Harris, 1986, are recorded from guppies (Poecilia reticulata) from the northern mountains of Trinidad. Mixed infections of the 2 species were found at 9 localities. Gyrodactylus turnbulli had a predominantly posterior distribution on the fishes, whereas G. bullatarudis was more anteriorly distributed. This is the first record of these species from guppies collected from within their original range.     

Susceptibility of Baltic and East Atlantic salmon Salmo salar stocks to Gyrodactylus salaris (Monogenea)

The susceptibility of a Baltic salmon stock Salmo salar (Indals?lv, central Sweden) to Norwegian Gyrodactylus salaris (Figga strain, central Norway) was experimentally tested and compared with previously obtained results on East Atlantic salmon (Lierelva, SE Norway). Contrary to expectation, the Baltic salmon, which had no prior exposure to this parasite strain, appeared almost as susceptible as the Norwegian salmon parr that naturally experience G. salaris-induced mortality. Individually isolated salmon of both stocks sustained G. salaris infections with little evidence of innate resistance. A few individuals of the Indals?lv stock controlled their infection from the beginning, but overall there was considerable heterogeneity in the course of infection in both stocks. On individual hosts, G. salaris growth rates declined steadily throughout the infection, a trend which was particularly marked amongst the Lierelva stock. On shoaling Lierelva fish, there was some evidence of reduced parasite population growth towards the end of the infection; this was not apparent in Indals?lv fishes. These results reflect a growing awareness that not all Baltic salmon may be resistant to Norwegian G. salaris, and that Norwegian and Baltic G. salaris strains may differ in virulence. Consequently, management decisions concerning this parasite-host system should be based upon the actual, and tested, susceptibility of stocks under consideration and not upon identification of stocks as either Atlantic or Baltic.     

The stimulatory effects of surfactants on composting of waste rich in cellulose

The chemical surfactant Tween 80 and biosurfactant rhamnolipid were respectively added to the composting substrate, a mixture of rice straw and bran, and their effects on the composting process were investigated. Samples were analysed for microbial communities of bacteria, actinomycetes and fungi, carboxymethylcellulose hydrolysis (CMCase) and xylanase activities, cellulose and hemicellulose fractions, water-soluble carbon (WSC) contents in the substrates, organic matter contents and pH values during the composting process. The results showed that both Tween 80 and rhamnolipid had slight stimulatory effects on the microbial populations of bacteria, actinomycetes and fungi. In addition, rhamnolipid increased the peak xylanase activity 15% higher than that of the control, while Tween 80 increased the maximum CMCase activity 35% higher than that of the control. As a result of the increased enzyme activities, treatments with Tween 80 and rhamnolipid were of higher WSC contents than the control during the whole composting process. Accordingly, the composting process was accelerated by the surfactants, since the organic matter was decomposed more quickly and the breakdown of cellulose and hemicellulose was better in the treatments with Tween 80 and rhamnolipid.     

Comparison of treatments for the in vitro detachment of cellulolytic bacteria from ruminal digesta samples

Four treatments were applied to ruminal digesta samples in a randomized complete block design experiment to evaluate their effect on the extent of detachment of ruminal cellulolytic bacteria. The treatments were: blending with anaerobic dilution solution (ADS), blending with ADS after a 6-h cold incubation, blending with ADS+Tween 80, and blending with ADS +Tween 80 after a 6-h cold incubation. Compared with blending in ADs alone, significant increases (p<0.2) of 10% and 12% in the number of cellulolytic bacteria were observed with the 6-h cold and the 6-h cold plus Tween 80 treatments, respectively. Tween 80 had no effect on the number of cellulolytic bacteria released from ruminal digesta samples irrespective of chilling. It was concluded that these additional treatments afforded little value over blending in buffer alone in detaching cellulolytic bacteria from ruminal digesta.     

High Endemicity with Clonorchis sinensis Metacercariae in Fish from Yongjeon-cheon (Stream) in Cheongsong-gun,Gyeongsangbuk-do,Korea

The infection status with Clonorchis sinensis metacercariae (CsMc) was examined in freshwater fishes from Yongjeon-cheon (a branch of Nakdong-gang) located in Cheongsong-gun, Gyeongsangbuk-do, the Republic of Korea (Korea). A total of 750 fishes in 19 species were examined by the artificial digestion method for 2 years (2019 and 2020). CsMc were detected in 378 (51.4%) out of 735 fishes in 14 species (73.7%), and the infection intensity was 666 per fish infected. In 2019, CsMc were found in 172 (68.0%) out of 253 fishes in 10 species, and the infection intensity was 565 per fish infected. In 2020, CsMc were detected in 206 (62.2%) out of 331 fishes in 10 species, and the infection intensity was 751 per fish infected. The other zoonotic trematode, ie. Metagonimus spp., Centrocestus armatus, Echinostoma spp. and Clinostomum complanatum, metacercariae were also detected in fishes from the survey streams, but their endemicities were relatively low. Conclusively, it was first confirmed that CsMc are highly endemic in fishes from Yongjeon-cheon in Cheongsong-gun, Gyeongsangbuk-do, Korea.     

A new gyrodactylid species from Cobitis granoei (Rendahl) (Cobitidae) in central China

Gyrodactylus granoei n. sp. (Monogenea: Gyrodactylidae) is described from the fins and body surface of the spine loach, Cobitis granoei (Rendahl) (Cobitidae), in central China. It resembles a suite of species from cyprinid and cobitid fishes that have short, compact hamuli, a ventral bar with no obvious anterolateral projections, a linguiform posterior membrane, a male copulatory organ with small hooks in multiple rows, a simple cylindrical dorsal bar, and short marginal hooks, with an expanded sickle heel. Of these, the new species resembles most closely Gyrodactylus micracanthus Hukuda, 1940 from Misgurnus anguillicaudatus (Cantor) (Cobitidae), but it is identified by the length of the hamuli and the morphology of dorsal and ventral bars. When searched using BLAST, sequence data (829 bp) spanning the ITS1, 5.8s, and ITS2 region did not return an identical match; close similarity (82-88%) was found with sequenced members of the subgenus Gyrodactylus. It is suggested that the new species is part of a freshwater lineage that has radiated successfully among cyprinid fishes in North America, Europe, and Asia, and some of their predator and amphibian neighbors.     

Molecular faunistics of accidental infections of <Emphasis Type="Italic">Gyrodactylus</Emphasis> Nordmann, 1832 (Monogenea) parasitic on salmon <Emphasis Type="Italic">Salmo salar</Emphasis> L. and brown trout <Emphasis Type="Italic">Salmo trutta</Emphasis> L. in NW Russia

Salmon Salmo salar L. and brown trout S. trutta L. juveniles were examined for the presence of accidental monogenean ectoparasitic species of Gyrodactylus Nordmann, 1832 in the Baltic and White Sea basins of Russian Karelia in order to estimate the frequency of host-switching attempts on an ecological timescale. To collect phylogeographical information and for exact species identification, the parasites were characterised by nuclear internal transcribed spacer sequences of rDNA (ITS) and, for some species, also by their mitochondrial DNA (CO1 gene) sequences. Four accidental Gyrodactylus species were observed on salmon and brown trout. A few specimens of G. aphyae Malmberg, 1957, the normal host of which is the Eurasian minnow Phoxinus phoxinus (L.), were observed on lake salmon from the Rivers Kurzhma (Lake Kuito, White Sea basin) and Vidlitsa (Lake Ladoga, Baltic basin). G. lucii Kulakovskaya, 1952, a parasite of the northern pike Esox lucius L., was observed on salmon in the Kurzhma. In the River Vidlitsa, two specimens of G. papernai Ergens & Bychowsky, 1967, normally on stone loach Barbatula barbatula (L.), were found on salmon. On anadromous White Sea salmon in the River Pulonga in Chupa Bay, a few salmon parr carried small colonies of G. arcuatus Bychowsky, 1933, which were shown to have originated from the local three-spined stickleback Gasterosteus aculeatus L. consumed as prey. No specimens of Gyrodactylus salaris Malmberg, 1957 were observed, although the Pulonga is the nearest salmon spawning river to the River Keret', which is heavily infected with introduced G. salaris. In the River Satulinoja, Lake Ladoga, three specimens of G. lotae Gusev, 1953, from burbot Lota lota (L.), were collected from a single brown trout S. trutta. All nonspecific gyrodactylid infections on salmonids were judged to be temporary, because only a few specimens were observed on each of the small number of infected fishes. The prevalence of endemic G. salaris was also low, only 1% (Nfish = 296) in Lake Onega and 0.7% (Nfish = 255) in Lake Ladoga, while brown trout specific Gyrodactylus species were not observed on any of the 429 trout examined from the Ladoga basin. The host-specific and unspecific burden of Gyrodactylus spp. on these 'glacial relict' populations of salmon and brown trout was very low, suggesting a generalised resistance against the co-evolved freshwater parasite community, or some kind of 'vaccination' effect. These hypotheses deserve further testing.     

Influence of tea tree oil (Melaleuca alternifolia) on the cattle tick Rhipicephalus microplus

The aim of this study was to verify the influence of tea tree oil (TTO) (Melaleuca alternifolia) tested in its pure and nanostructured (TTO nanoparticles) forms on the reproduction of female Rhipicephalus microplus. For our purpose, female ticks were collected from naturally infected animals and treated in vitro with TTO (1, 5, and 10 %) and TTO nanoparticles (0.075, 0.375, and 0.75 %). In order to validate the tests, they were performed in triplicate using positive (amitraz) and negative (untreated) controls. It was possible to observe that pure TTO (5 and 10 %) and TTO nanoparticles (0.375 and 0.75 %) showed 100 % reproductive inhibition on female ticks. Additionally, pure TTO (1 %) also showed an acaricide effect (70 %), similarly to the positive control (78.3 %). This is the first study demonstrating the activity of pure TTO and TTO nanoparticles on female ticks. Therefore, based on these results, we were able to show that both forms and all concentrations of M. alternifolia affected tick reproduction by inhibiting egg laying and hatching. We were also able to show that TTO nanoparticles potentiated the inhibitor effect of pure TTO on the reproduction of R. microplus.     

A novel actinomycete derived from wheat heads degrades deoxynivalenol in the grain of wheat and barley affected by Fusarium head blight

Deoxynivalenol (DON) is a hazardous and globally prevalent mycotoxin in cereals. It commonly accumulates in the grain of wheat, barley and other small grain cereals affected by Fusarium head blight (caused by several Fusarium species). The concept of reducing DON in naturally contaminated grain of wheat or barley using a DON-degrading bacterium is promising but has not been accomplished. In this study, we isolated a novel DON-utilising actinomycete, Marmoricola sp. strain MIM116, from wheat heads through a novel isolation procedure including an in situ plant enrichment step. Strain MIM116 had background degradation activity, and the activity was enhanced twofold by the consumption of DON. Among Tween 20, Triton X-100 and Tween 80, we selected Tween 80 as a spreading agent of strain MIM116 because it promoted DON degradation and the growth of strain MIM116 in the presence of DON. The inoculation of MIM116 cell suspension plus 0.01% Tween 80 into 1,000 harvested kernels of wheat and barley resulted in a DON decrease from approximately 3 mg kg^?1 to less than 1 mg kg^?1 of dry kernels, even when cells had only basal levels of DON-degrading activity. To the best of our knowledge, this is the first report that describes (1) the isolation of a DON-degrading bacterium from wheat heads, (2) the effects of surfactants on the biodegradation of DON and (3) the decrease of DON levels in naturally contaminated wheat and barley grain using a DON-degrading bacterium.     

Infestations by Gyrodactylus sp. of Atlantic salmon, Salmo salar L., in Norwegian rivers

Young Atlantic salmon, Salmo salar , brown trout, Salmo trutta , and Arctic char, Salvelinus alpinus , from eight rivers in North and Mid Norway were examined for Gyrodactylus. The fish were collected from 1975 to 1980. A Gyrodactylus salaris type was observed infecting salmon from six of these rivers. No trout or char were infected. A high frequency and intensity of infection of salmon were observed in all but one of the rivers surveyed. In the Saltdalselva, only one specimen of Gyrodactylus infecting one fish was observed. No subsequent mortality of salmon was observed in this river while there were signs of a high mortality of salmon in the other rivers. The salmon parr were more frequently attacked than the fry, the mortality of salmon seemed to have happened in most of the rivers one year after the first observations of Gyrodactylus were made. The mortality of salmon and the high infection rate of Gyrodactylus in these rivers appears unique, and as far as known to the authors there are no other described cases of mortality due to Gyodactylus in Atlantic salmon in natural waters. The reasons for the outbreak of Gyrodactylus in these rivers are not known. Two theories are discussed: one that the fish were weakened by environmental factors and the other that Gyrodactylus was introduced from some of the infected salmon hatcheries in Scandinavia.     

Prevalence and Infection Intensity of Zoonotic Trematode Metacercariae in Fish from Soyang-cheon (Stream), in Wanju-gun,Jeollabuk-do,Korea

We surveyed on the infection status of zoonotic trematode metacercariae (ZTM) in freshwater fishes from Soyang-cheon (a branch stream of Mangyeong-gang) in Wanju-gun, Jeollabuk-do, the Republic of Korea. A total of 927 fishes were individually examined with the artificial digestion method during 2013–2015 (462 fish in 15 spp.) and 2018–2019 (465 fish in 25 spp.). Clonorchis sinensis metacercariae were detected in 207 (31.4%) out of 659 fishes in 14 positive fish species (PFS), and their mean intensity was 114 per fish infected (PFI). Metagonimus spp. metacercariae were found in 302 (37.4%) out of 808 fishes in 21 PFS, and their mean intensity was 12 PFI. Centrocestus armatus metacercariae were detected in 222 (59.0%) out of 376 fishes in 12 PFS, and their mean intensity was 383 PFI. Echinostoma spp. metacercariae were found in 139 (22.1%) out of 628 fishes in 10 PFS, and their mean intensity was 7 PFI. Clinostomum complanatum metacercariae were detected in 14 (6.5%) out of 214 fishes in 4 PFS, and their mean intensity was 2.4 PFI. Metorchis orientalis metacercariae were detected in 36 (13.5%) out of 267 fishes in 5 PFS, and their mean intensity was 4.3 PFI. Conclusively, the prevalence and infection intensity of ZTM is generally not so high in fishes from Soyang-cheon. However, those of C. sinensis metacercariae are more or less higher in 2 fish species, Pungtungia herzi and Sarcocheilichthys variegatus wakiyae.     

The anticonvulsant activity of cannabidiol and cannabinol

The anticonvulsant activity of delta-9-tetrahydrocannabinol was compared with that of two other naturally occurring cannabinoids, cannabidiol and cannabinol, in a maximal electroshock test in mice. The drugs were administered as an emulsion of sesame seed oil, Tween 80 and saline to mice i.p. The results indicate that all three cannabinoids are effective anticonvulsants. The time for peak effect is about 2 hr. In terms of relative potencies, cannabidiol and delta-9-THC are similar but both of them are more active than cannabinol.