Temporal And Spatial Distribution Of Two Third-generation Larvae Of Red-tailed Horseshoe Mistletoe

In recent years,with the rapid development of molecular biology,the complete mitochondrial genomes of the Homatula variegate Dabry de Thiersant,1874,Gyrodactylus variegatus(new species,in press)and Paragyrodactylus variegatus You,King,Ye et Cone,2014 have been sequenced.Through the analysis morphological identification and phylogenetic tree,it is found that the two parasites of G.variegatus(Gyrodactylidae:Gyrodactylus)and P.variegatus(Gyrodactylidae:Paragyrodactylus)are parasitic viviparous genera infected H.vriegate.The study was found that the two parasites are only recorded on H.variegate.Which is indicated that the G.variegatus and P.variegatus have strongly host specificity.Two kinds of parasites which are belonged to the homologous family but not the same genus on the identical host compete with each other limited space and resources and eventually keep dynamic state of competition-coexist.The study had scanned the H.variegate from Xunyangba(33.33°N,108.33°E)region of Ningshan County in Shaanxi province.That was counted the quantity and infection rate of G variegatus and P.variegatus on various fins and analyzed the factors that affect the infection rate,in order to reveal the features of spatial and temporal distribution of G.variegatus and P.variegatus.In addition to,it can be provided regulation for the corresponding ecological prevention and control measures,meanwhile,methods which are provided with the biological control and forecast the dynamic changes of the other fish parasites.Following are the main results and conclusion:1.The G.variegatus and P.variegatus occur varied preferences in different length hosts:G variegatus prefer parasitized on the small host more than the large and medium host in size;while P.variegatus dislikes parasite most on the large host.There are no selective difference between the small and medium-sized host.2.The infection rate of G.variegatus and P.variegatus decline trend from March to May,then ascending from May to June,decline from June to August,rising again from August to September,the curve shows as the type of "W".The highest mean infection intensity of G variegatus and P.variegatus are different among the months:the highest mean infection intensity of G variegatus occur in April,while the P.variegatus occur in June.3.The mean infection intensity of G variegatus and P.variegatus were not significantly different on March and April,but very significantly different among the other months.4.The spatial distribution patterns of G.variegatus and P.variegatus population are aggregated among different months.The degree of aggregation of the G.variegatus and P.variegatus is biggest in August and March,respectively.5.The highest infection rate and mean infection intensity of G.variegatus and P.variegatus is on the dorsal and caudal fin in their host,while,the lowest is on the right side of pelvic fin and dorsal fin,respectively.The G.variegatus prefer to colonize on the dorsal fin,while,the P.variegatus prefer to inhabit on the caudal fin and mostly dislike to parasitize on dorsal fin.6.The mean infection intensity between G.variegatus and P.variegatus on the two sides of pelvic fins is significant positive correlation and very significant positive correlation on the other fins.7.The spatial distribution patterns of G.variegatus and P.variegatu are aggregated on each fins of host.That is to say,the most fins of hosts infect a small amount or not,while a large number of parasites inhabit merely on several fins.8.The infection rates of the G.variegatus was the highest on dorsal fin in March,April,May,July and September,on right side of the pectoral fin in June and on the caudal fin in August.While infection rates of the P.variegatu is the highest on caudal fin in March,May,June,July and September,and on the right side of the pectoral fin in April and August.9.The G.variegatus transfers from dorsal fin to the right side of pectoral fin while the water temperature at 21? in June and from dorsal fin to caudal fin at 17? in August.But,the P.variegatus transfers from caudal fin to the right side of pectoral fin at 17? in August and 13? in April.10.The spatial distribution patterns of G.variegatus and P.variegatus are uniform on the left side of pectoral fins in May and the two fins(pectoral fin and dorsal fin)in April.While,the aggregate distribution on each fins in the rest months.11.In general,infection and mean intensity of G.variegatus were higher than that of P.variegatus.These results suggested that the propagation of G.variegatus population was more successful than that of the P.variegatus population.