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Juvenile hormone control of development of selected tissues in the migratory grasshopper, Melanoplus sanguinipes (Fabr.) (Orthoptera:Acrididae)

University of British Columbia

Changes in total body weight and in dry weights of the internal organs indicated that male and female adults of Melanoplus sanguinipes undergo a biphasic growth pattern. Regression analyses indicated that the overall growth rates were comparable in the two sexes during the somatic growth phase but differed markedly during the reproductive phase. Reasons for these differences are discussed in light of the behavior and physiology of the sexes. Head width, tibia length, tegmina length, and dry weights of gonads, fat body, and flight muscles were highly correlated in normal adults. This indicated that growth patterns were highly coordinated within individual insects. Fluctuations in the dry weights of the fat body and flight muscles during reproductive development indicated that these tissues were a source of protein for the developing ovaries or accessory glands. The similarity in the pattern of changes in males and females indicated that development may be synchronized between the two sexes. Factors contributing to this apparent synchrony are discussed. Depending upon the time of application, both the anti-allatotropin, precocene II and the juvenile hormone analog (JHA), R-20458 have been shown to drastically alter the development of various tissues in M. sanguinipes. The present studies substantiate previous reports that JH regulates the development of the fat body and gonads. In addition, JH has been shown to regulate metamorphosis, somatic growth, coloration, wing length, and development of the flight muscles and fat body during the fifth instar. Precocene applied to fourth instars caused precocious metamorphosis and the production of diminutive adults. However, nearly normal development was produced in pxecocene-treated insects when R-20458 was applied 4 days later. Later JHA treatments resulted in the production of nymphal-adult intermediates. Intermediates were also produced when JHA alone was applied to fifth instars. However, specific effects depended upon precise application time. Supernumerary molting occurred only in insects treated with JH during the middle of the fifth instar stadium. Therefore, absence of JH at this precise time seems to be necessary to permit the imaginal molt. Green-colored and short-winged adults characteristic of locust solitarious phase, were produced when JHA was applied at certain times within the fifth instar. JHA application to fifth instars resulted in a significant reduction in wing length and in dry weight of the flight muscles. Flight muscles were sensitive to JHA throughout the fifth stadium whereas wing length was only significantly affected by JHA during certain periods of the stadium. Therefore, the flight muscles must be developing separately from the wings. JHA applications to precocious adultoids were too late to change the commitment of flight muscles in either sex, or of the male gonads. However, the fat body of males and females, and the female gonads were still susceptible to JHA at this time, and the precocene-induced sterility of females was reversed.

Text

2010-03-26

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http://hdl.handle.net/2429/22574

Plant Science

University of British Columbia

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