ISSN:
1432-0886
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Medicine
Notes:
Summary Locusts generally alternate between a grasshopper or solitaria phase and a swarming, migrating gregaria phase. The chromosome complements of three locusts have been compared for size relationships and frequency of chiasmata in various strains. The species are the Desert locust Schistocerca gregaria, the African migratory locust Locusta migratoria migratoriodes, and the Brown locust Locustana pardalina. The first two were represented by strains from the invasion territory and outbreak region respectively, as well as by strains from South Africa and Tanganyika. The Brown locust is found only in an outbreak region in South Africa. 1. The chromosome complements of the three species are very alike in being composed of three long, five medium and three short chromosomes, plus one X in the male. The individual sizes of the long and medium chromosomes are alike in the species when represented as percentages of the longest chromosome. 2. In these species chiasma frequency is not in simple relationship to chromosome length. 3. In the 3S chromosomes of all three species and their strains the chiasma frequency is almost invariably one per bivalent. 4. The Desert locust, living in invasion territories, in both northern and southern strains, is characterized by high chiasma frequencies in the 3L and 5M chromosomes. 5. The African migratory locust, in the northern strain, has relatively low chiasma frequencies but in strains in what are assumed to be invasion territories, the chiasma frequencies in both the 3L and 5M chromosomes are relatively higher. A dominance relationship is indicated between low and high frequencies. 6. The Brown locust, which is at present undergoing an outbreak cycle, shows significant increases in chiasma frequency in populations which have gregarized in the outbreak region. These increases are more or less proportional to the history of the population, i.e. to the amount of gregarization which is indicated by the number of generations of congregation and swarming. The higher chiasma frequencies are transmitted to laboratory offspring in which the frequencies have risen to what are surmised to be maxima. 7. A working hypothesis is discussed on the possible relationships between increased genetic recombination and swarming in locusts.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00368138
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