The Highest Chromosome Number on A Velvet Worm (Onychophora)

The velvet worms (Onychophora) are poorly studied animals. The low morphological diversity in this group is an obstacle to its taxonomy and chromosomal analyses can be helpful. The chromosomal analyzes of one species of Epiperipatus from Mato Grosso do Sul, Brazil, showed 2n♂ = 73, the highest diploid number found in Onychophora up to now. Telomeric fluorescent in situ hybridization (FISH) marked the telomeric region of all elements and revealed one Interstitial Telomeric Site (ITS) on the proximal region of the long arm of the odd large submetacentric chromosome. The absence of male meiosis and female cell division did not allow us to define if the unpaired large submetacentric is a sex chromosome, which could lead to the description of a rare sex chromosome system (SCS) in Onychophora, or a case of fusion between autosomes. In either case, the presence of ITS is a clear indication of chromosomal fusion.

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