Chromosomal Features of the Endemic Pill Millipedes (Arthrosphaera: Sphaerotheriidae, Diplopoda) from Western Ghats, India

Abstract

Chromosome features and karyotypes of male meiosis of 2 species of pill millipedes belonging to the genus Arthrosphaera (Arthrosphaera dalyi and Arthrosphaera sp.) endemic to the Western Ghats revealed interesting facts. The Arthrosphaera dalyi has diploid chromosome number (2n) 30 with relative lengths ranging from 39–195. It showed 3–4 distinct subtelocentric chromosome pairs with discernible short arms and the rest are acrocentrics and/or telocentrics. In Arthrosphaera sp. the diploid chromosome number (2n) is 26 and all chromosomes are telocentrics with relative lengths ranging from 36–178. The first pair of chromosome is the largest of all the chromosomes in both the species and is homomorphic in Arthrosphaera sp. and hetromorphic in A. dalyi, wherein one of the chromosomes is the largest and subtelocentric with a clear short arm and the other homologue is a telocentric chromosome. The sex determination mechanism is XX/XY type. A synopsis of the diplopod chromosomes is presented, compared and the possible evolutionary significance have been discussed.