NO HARMFUL EFFECTS OF A SELFISH B-CHROMOSOME ON SEVERAL MORPHOLOGICALAND PHYSIOLOGICAL TRAITS IN LOCUSTA-MIGRATORIA (ORTHOPTERA, ACRIDIDAE)

Effects of B chromosomes on a number of morphological and physiologica l traits were analysed in 33 controlled crosses performed with Locusta migratoria specimens collected in a natural population close to Grana da (Spain). The results show highly significant differences among fami lies, but the absence of any significant effect of Bs on the individua ls carrying them. There was, however, a slightly negative relationship between body size, somatic weight and somatic condition of the progen y and the presence of a high number of Bs in the parents, mostly in th e mother. This suggests a possible harmful effect of these B chromosom es on egg allocation of substances regulating the initial stages of de velopment. The implications of these findings are discussed in relatio n to the present understanding of the selfish theory of B chromosome e volution. It is proposed that selfishness and parasitism are two diffe rent properties of B chromosomes that should be considered separately.