A Chromosomal Investigation Of The Chinese Panorpidae (Mecoptera)

Panorpidae are the most species-rich family in Mecoptera, with over420describedspecies assigned to six genera. Genera Panorpa Linnaeus and Neopanorpa Weele composedabout95%of the species of Panorpidae. Compared with other insects, the cytogenetic studiesof Mecoptera are fairly limited. To date，no research literature about this subject has beenpublished in China. In this study, we investigated the meiotic chromosomes of spermatocytesof10species of Panorpidae mainly using conventional squashing procedures.We found that Neopanorpa lui, Chou&Ran,1981, P. dubia, Panorpa dubia Chou&Wang,1981, Panorpa sp1and Panorpa sp2all possess XO sex chromosomes, and that theyhave20,19,23and19pairs of autosome respectively. Dicerapanorpa magna Chou,1981,Panorpa byersi Hua&Huang,2007, P. biclada Zhang&Hua,2012, P. fulvastra Chou,1981,P. emarginata Cheng,1948and P. qinlingensis Chou&Ran,1981all have about20pairs ofautosome.We found that only one tip of some bivalents were stained deeply in pachytene ofspermatocytes in many species. Two such deeply stained tips often associated with each other.We also found that the meiosis of N. lui, P. dubia, Panorpa sp1, Panorpa sp2and P. byersilack typical diplotene and diakinesis. After pachytene, accompanying the shortening andcondensing of the bivalents, homologous chromosomes of each bivalent retain parallel in aline and show no evidence of crossing-over. Additionally, the parallel-arranged homologouschromosomes of many bivalents could be seen during metaphase I of the spermatocytes ofPanorpa sp1..We could not assert the achismatic meiosis in P. Biclada, P. fulvastra, P. magna, P.emarginata and P. qinlingensis, because we have not obtained the spermatocytes in the stagefrom pachytene to metaphase I.In this study I also tried to locate the18S rDNA in meiotic chromosomes of these speciesof Panorpidae using fluorescence in situ hybridization, but I did not detect the hybridizationsignal at last. I only obtained the18S rDNA probes marked with DIG using nick translationmethod.The evolutionary trend of chromosome numbers and the evolutionary process of sexchromosome in Mecoptera as well as the achiasmatic meiosis in Panorpidae were briefly discussed.