| As an essential part of the animal evolution and phylogeny,the genus Dugesia,belonging to Turbellaria of Platyhelminthes,is a type of traditional experimental animals in cell biology,neurobiology,regenerative biology,genetics,and many other disciplines.However,the investigation into planaria started relatively later in China,and much relevant research urgently need to be pushed forward.In recent years,a cave-dwelling planarian was discovered during the investigation of cave animal diversity in the Xiaoxi National Nature Reserve,Xiangxi Tujia and Miao Nationalities Autonomous Prefecture,Hunan Province.In this paper,the identification and some eco-biological characteristics of this suspected new species were carried out.The main results were as follows:1.Paraffin section was used to observe the internal structure of sexual reproductive individuals of the cave planarians.The results indicated that there was a muscle bulge(HUMP)on the posterior and upper part of dorsal cystic tube of it and that the ejaculatory tube opened backward through the ventral opening in the middle of the mastoid process of male genitalia.Above these were the main diagnostic characteristics of this planarian.2.Molecular phylogenetic analysis was conducted based on 28 S r DNA,mt DNACOI and ITS-1 genes.The results showed that the length of 28 S r DNA,mt DNA CO1,ITS-1gene were 1528,450 and 721 bp,respectively.Based on 28 S r DNA,the genetic distances between 17 species and one outgroup of the genus were calculated.The closest genetic distance was the one between Dugesia japonica and this cave speceis,which is 0.027.In addition,based on ITS-1,the genetic distance between 28 species and one outgroup of the genus was also calculated.The results revealed that the closest genetic distance was that with D.Majuscule,0.050.The genetic distance calculation based on mt DNA COI gene between 8 oriental and Australian homologous species and an outgroup showed that the closest genetic distance was that with D.ruyuyuensis,0.119.Besides,phylogenetic trees were constructed using ML method,respectively.The tree constructed based on 28 S r DNA gene,17 intraspecific species and 1 outgroup showed that the closest relationships were D.umbonata and D.japonica.Also,based on the COI gene,combining data sets of 28 intraspecific species and 2 outgroups,the tree showed the most closely related species was D.majuscula from Hainan Island.Based on ITS-1,combining data sets of 28 intraspecific species and 1 outgroup,the tree showed that D.umbonata was most closely related.Based on morphological characteristics and molecular phylogenetic data analysis,the results showed that the planaria was a new species of the genus Dugesia,and named as Dugesia dongxuensis n.sp.,Liu & Ren,2022.It should be the sixth species of Dugesia in China.3.The karyotype analysis by Air Drying and Centrifugal Suspension Method on this planarian showed that its chromosome base was 8,mainly diploid,2n =16.The karyotype formula was 2n = 2x =16 =16m,all of which were middle centromere chromosomes.4.The regeneration ability of this planaria was also studied.The results showed that the survival rate of the planaria was 100% at 10～30℃.Under the condition of 15～30℃,the population showed positive growth.At 20 ℃,the planaria lived with highest population density,instantaneous growth rate and survival rate,as well as the regeneration cycle was the shortest(only 4～6 days).In conclusion,the 20℃ might be the optimum temperature for planarians to live and regenerate. |
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