Study On Population Ecology And Molecular Systematics Of Dactylogyrus On Gills Of Leuciscinae In Irtysh River, China

Dactylogyrus is a member of Monogenea, Carus, Dactylogyridae Bychowsky. Itis a class of parasites harmful to fishes. In this article, with conventional fishparasitology survey methods and modern molecular biology techniques, we studiedthe species composition and population dynamics of Dactylogyrus, fish parasites ofLeuciscinae in international river Irtysh and analyzed the phylogeny of some insectspecies. The main conclusions are as follows:(1) Through field surveys, seven dactylogyrus species in Leuciscinae werecollected and identified. Of them, one species was a new record of Monogenea inChina. We described the morphological features of the newly recorded insect speciesin detail and drew its characteristic figure.(2) The prevalence and infection intensity of Dactylogyrus wunderi in Abramisbrama orientalis varied different length groups. The distribution pattern in hosts ofdifferent length groups and different gill lamellae positions was mainly gatheringdistribution, and the gathering strengths were slightly different. The infectionintensities were not significantly different among different body length groups ofhosts. The infection rates of Dactylogyrus in the left and right gills were not verydifferent, indicating no apparent selectivity to right or left gill. The infection rate andinfection intensity were higher in the right gill in the large length groups, but thistrend was not obvious in the left gill. The infection rate and infection intensity wereminimum in the small body length group. The results were not significantly differentbetween the two gills of Dactylogyrus wunderi among different body length groups,indicating no strong selectivity.(3) We discovered three Dactylogyrus in Leuciscus idus, namely D. tuba, D.micracanthus and D. alatus. The total prevalence and infection intensity of them weredifferent in different body length groups. No infection was found in the L <10group. The distribution type of Dactylogyrus population is mainly clustered distribution indifferent host body length groups. The prevalences in the left and right gills weresimilar. The prevalence in the left gill (except gill I) was higher than right gill. Theaverage infection intensity outside dactylogyrus gill IV gills was larger than the leftand right cheek. The prevalences between body length groups were not significant,but were significantly different between the right gill lamellae.(4) Rutilus rutilus lacustris was infected by two Dactylogyrus species, namelyDactylogyrus vistulae and Dactylogyrus sphyra. Their total prevalence was22.22%and the average infection intensity was4.5(1-24). The mean infection intensity wasmaximized in the length group of16<L≤19, while infection rate and infectionintensity were minimized in body length group of19<L. The distribution type ofDactylogyrus host population in different length groups was gathered distribution,except19<L which is even distribution. The infection intensities were significantlydifferent between the body length groups of19<L and10<L≤13,3<L≤16and16<L≤19. The infection intensities were not significantly different among the rest bodylength groups.(5) We determined the18S-ITS1-5.8S rDNA sequences of four Dactylogyrusspecies by conventional molecular biology techniques and obtained their NCBIaccession numbers (KJ605444-KJ605447). The18S,5.8S rDNA sequences wereconservative throughout the sequence, and ITS1displayed relatively low similarity.However, there are also conserved regions. The genetic distance matrix andphylogenetic tree show that the distance between Dactylogyrus species was thesmallest, followed the distance between Dactylogyrus and Pseudodactylogyrus, whichis smaller than the distance between Dactylogyrus and Ancyrocephalus.