Cytological basis of the B chromosome accumulation mechanism in the grasshopper Heteracris littoralis (Ramb).

An accumulation mechanism of the standard B chromosome of the grasshopper Heteracris littoralis has been studied in a natural population located in El Saler (Valencia) by two different methods: (i) the karyological analysis of the offspring from wild females and (ii) cytological observations of male and female meiosis. The transmission rate of the accessory through females obtained from crosses (0.61) was slightly lower than that obtained from direct meiotic observations of secondary oocytes (0.71). The B chromosome is transmitted at a rate of about 0.5 through 1B males, the value expected from mendelian segregation. The implications of these findings are discussed and the parasitic nature of the B is proposed.