The trophic tissue of telotrophic ovarioles in polyphage coleoptera

Summary The trophic tissue of ovarioles of 32 species of polyphage Coleoptera was investigated by light and electron microscopy. Ovaries were compared according to the number of ovarioles, length, width, and volume of the terminal chambers, to the number, diameter, and volume of nurse cell nuclei, as well as to the structure of nurse cell cytoplasm and to the structure of interstitial cells. Mitosis of nurse cells or interstitial cells in fully developed ovarioles was never observed, but there is strong evidence for endomitosis in nurse cells. According to the different extent of reduction of nurse cell membranes in ovarioles of diverse species, three basic types of nurse cell organization could be established, representing tissues of a primary stage, transition stage, or secondary stage, respectively. These different forms of nurse cell organization are family-specific and correspond to ontogenetic stages of ovariole development ofBruchidius, which is a highly developed polyphage beetle. The distribution among the investigated families is consistent with the phylogenetic relationships among polyphage Coleoptera as far as they are known today. There is evidence that more highly organized nurse cell tissues have evolved independently from primary stage tissues in at least two cases. This investigation was supported in part by the Stiftung Volkswagenwerk