جستجوی مقالات مرتبط با کلیدواژه « داکتیلوژیروس » در نشریات گروه « دامپزشکی »

Dactylogyrus is one of the most common external parasites on  the gills of Cyprind fish. These parasites are highly host specific and many species only have a specific host.

Since there are reports of silver carp specific Dactylogyrus species isolated from big head carp and vice versa, the investigation of Dactylogyrids have been done in these two fish species.

81 silver carp and 82 big head carp were caught from 10 fish farms in Guilan province and after preparing wet mounts of body surface Dactylogyrus parasites divided and fixed by glycerin jelly. In order to perform morphometric assessments on captured images, Image J software was used for 7 point to point distances. Drawing of parasites was done by drawing tube and then compared by identification keys and parasites identified. For molecular investigation the genomic DNA was extracted from one parasite specimen and 28S rDNA region of Dactylogyrus specimens were amplified by related primers in PCR.

Sequences were deposited in GenBank with accession numbers MG825611 and MG825765 respectively for D. hypophthalmichthys and D. suchengtaii isolated from Hypophthalmichthys molitrix, and also MH023397 and MH023399 respectively for D. aristichthys and D. nobilis isolated from Hypophthalmichthys nobilis. The phylogenetic tree shows the genetic affinity of isolated parasites from these two fish.

It seems hybrid fish are sometimes produced accidentally in fish reproduction centers of Iran. Racial impurity of silver carp and big head carp is not only the reason of poorer breeding efficiency in fish farms but also these hybrid fish are hosts of more parasitic species.

Dactylogyrus spp. are monogenean worms found mostly as ectoparasites on the gills of several fish species, including carp and goldfish. These parasites are commonly detected by microscopic analysis of the gill lamellae, but this is time-consuming and technically difficult. In contrast to this conventional method, molecular techniques provide specific, sensitive and safe detection of parasites. In the present study, polymerase chain reaction (PCR) and subsequent DNA sequencing were used to detect Dactylogyrus spp. Specific common primers were designed to amplify the ITS-1 region of the rRNA gene of Dactylogyrus spp. Dactylogyrus worms were collected from 100 goldfishes and identified using a dissection microscope. Then, single worms were used for DNA extraction. To evaluate the PCR, a single parasite was added to a parasite-free gill, which then had its DNA extracted. Subsequently, the PCR products were purified and sequenced. Comparison of the nucleotide sequences of the PCR products with GenBank sequences showed that there was 100% homology with sequences from two Dactylogyrus spp., namely Dactylogyrus vastator and Dactylogyrus dulkeiti (registered under accession numbers AJ 564159 and AJ 564126, respectively). The results obtained from sequence analyses were consistent with species identification by microscopy. Therefore, the results show that it is possible to develop a sensitive and precise PCR method for the detection of Dactylogyrus-infected fish using DNA extracted from the whole gill.

In the present study, we reported infection with eighteen species of the genus Dactylogyrus, belong to the family Dactylogyridae from five breeder fish species, including common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), big head carp (Hypophthalmichthys nobilis) and black carp (Myelopharyngodon piceus) which introduced and imported to Iranian freshwaters from Russia, Romania, Hungary and China over the last 40 years. The infection was also found in Carassius auratus gibelio, it is not known when this fish species was introduced into the country. The Dactylogyrus spp. were as follows: Dactylogyrus achmerovi, D. anchoratus, D. aristichthys, D. baueri, D. dulikeity, D. ctenopharyngodonis, D. extensus, D. hypophthalmichthys, D. intermedius, D. intermedioides, D. lamellatus, D. magnihamotus, D. nobilis, D. sahuensis, D. suchengtaii, D. taihuensis, D. vastator and D. wegeneri. Among these, D. vastator and D. anchoratus infecting common carp and D. lamellatus infecting grass carp are very harmful and were responsible for high mortalities observed in fry and fingerling production in Iran. Uncontrolled import of live fish into the country can lead to transmission of pathogenic monogeneans or other group of parasites to native fishes, causing a great economical and ecological threat to valuable native fishes. For example, transmission of D. anchoratus from common carp to Barbus sharpeyi, an important native fish species, despite of the high host-specificity of monogeneans, indicates the possibility of transmission of exotic monogenean parasites to native hosts. It is strongly suggested that the risk of introducing exotic pathogens along with importing fish or any other living organism to the country, should be assessed well in advance, in order to protect native species and the ecosystem.