The Highest Chromosome Number and First Chromosome Fluorescent insitu Hybridization in the velvet worms of the familyPeripatidae

摘要

The diversity of Onychophora is poorly studied, despite there being nearly 200 describedspecies divided in two families: Peripatidae and Peripatopsidae. Peripatid velvet wormsare found mainly in the Neotropical region. The low morphological diversity in Peripatidaeis an obstacle to determining its taxonomy, and chromosomal analyses can help clarifythis. The aim of this work was to chromosomally analyze one species of from Mato Grosso do Sul, Brazil. Conventional staining andtelomeric fluorescent hybridization (FISH) were performed withthe gonads of three males of sp. The specimens showed 2n♂ =73, the largest diploid number found in Onychophora to date, with the majority ofchromosomes acro/telocentrics and the largest element submetacentric. The FISH marked thetelomeric region of all elements and revealed one Interstitial Telomeric Site (ITS) on theproximal region of the long arm large submetacentric chromosome. The absence of malemeiosis and female cell division in the analyzed specimens prevented us from determiningwhether the unpaired large submetacentric is a sex chromosome, which could lead to thedescription of a rare sex chromosome system (SCS) in Onychophora, or a case of fusionbetween autosomes. In either case, the presence of ITS is a clear indication ofchromosomal fusion.