Karyotype, meiosis and sperm formation in the red palm weevil Rhynchophorus ferrugineus.
Rhynchophorus ferrugineus is considered one of the most dangerous and destructive insects to the date palm tree in the Kingdom of Saudi Arabia. Therefore, karyotype, meiosis and sperm formation were investigated in this weevil, which was collected from different farms of Riyadh, the capital city of Saudi Arabia. The chromosome number is n=11 and 2n=22. In the karyotype analysis, the somatic chromosomes were categorized into two groups; five pairs of metacentric and five pairs of submetacentric. The sex chromosomes include one acrocentric X chromosome and one dot-shaped Y chromosome that form a parachute system type (Xyp). The lengths of the chromosomes vary between 1.11 and 4.44 µm, and the Y chromosome is the shortest. The fundamental number (the number of arms) of the chromosomes is 42, while the number of arms for the somatic chromosomes is only 40. Several stages of the first and second meiotic cell divisions were observed and described.