Histological changes in the endocrine system of Locusta migratoria L. associated with the growth of the adult under different temperature regimes

Abstract

Studies have been made on the endocrine system of 6-day-old adult locusts kept under the temperature régimes: 30±0·5, 15±0·5, and 45±0·5°C; and on 16-day-old adults kept under the fluctuating temperature régimes: 30±0·25, 30±10, and 30±15°C. No differences which could be co-related with the temperature treatments were found in the medial neurosecretory cells of the protocerebrum. Under the régime 15±0·5°C, there was relatively less ‘A’ material present in the anterior lobes of the corpora cardiaca, while under the régime 30±15°C the nervi corporis cardiaci I and the corpora cardiaca were almost or completely empty of ‘A’ material. In the other régimes normal amounts of ‘A’ material were present throughout the system. Considerable differences were found in the corpora allata. At 15°C the gland was shrunken, the nuclei distorted, and their response to methyl green/pyronin staining variable, the gland clearly being in a pathological condition. At 45°C the nuclei also showed different staining reactions to methyl green/pyronin stain compared to that at 30°C, also the nuclei were close to the gland margin, giving the appearance of an epithelium which is not seen in the normal gland. At 30±10°C the allatum showed more vacuoles and the peripheral nuclei lying closer to the gland margin than at 30±0·25°C. At 30±15°C these differences are exaggerated, the peripheral nuclei being pressed close to the gland margin and many large, partially empty vacuoles appearing in the gland. The significance of these changes is discussed, and it is concluded that the changes in the endocrine system under fluctuating conditions are of the same nature as Selye's ‘general adaptation syndrome’. This does not mean that the response elicited by these changes in the endocrine system is not specific to the temperature régime imposed.