Recent results from biochemical and molecular genetic studies of the accessory gland proteins in male Drosophila are reviewed. The most prominent feature is the species-specific variability. However, the analysis of the sex peptide in D. melanogaster shows that there is a strong homology in the molecular structure to the closely related sibling species, and that divergence increases with increasing phylogenetic distance. For this reason the sex peptide, after being transferred to the female genital tract during copulation, reduces receptivity and increases oviposition only in virgin females belonging to the same species group and subgroup. Even though studies were hitherto limited to a small number of the secretory components, it is evident that the accessory gland proteins play a key role in reproductive success of the fruit fly by changing female sexual behavior, supporting sperm transfer, storage and displacement. Thus, genes encoding the accessory gland proteins are apparently under strong evolutionary selection.

By using the automatic amino acid analyzer (model 120 B, Beckman) the free ninhydrin-positive components in the methanol extracts of Drosophila melanogaster were fractionated. Compared to the conventional paper partition chromatography the great advantage of this technique is the distinct separation of such amino acids like leucine, isoleucine, phenylalanine, valine, methionine, γ-amino-butyric acid as well as the basic components ornithine, lysine, histidine and arginine. Furthermore, the occurrence of phosphoserine, tyrosine phosphate, ethanolamine, phosphoethanolamine and glycerophosphoethanolamine was identified. The metabolic significance of these substances is discussed.

Summary. Experiments designed to analyze the lethality and hybridogenesis in the European green frog complex have yielded the following results: 1. As a rule the inter-se cross ofRana esculenta is lethal, but several crosses have produced fully viable progeny. The frequency of such 'break-through' crosses appears to be related to parental population structure. 2. Parabiotic joining of lethal to viable embryos indicates that manifestation of the lethal effect is autonomous. There is, however, a 16-18% increase in the life span of the lethal partner. 3. Studies of LDH isozyme patterns revealed that the lessonae-specific alleles coding for the B a and B c subunits can be passed to the Fi progeny from a parental female or male of the esculenta phenotype. This demonstrates that there is no total elimination of the lessonae genome in the esculenta germ cells. 4. Immunologically, offspring from the inter-se cross ofR. esculenta show a closer relationship to the ridibunda than to the esculenta phenotype. Variations of antigenic protein patterns suggest the possibility of chromosomal recombination between lessonae and ridibunda in the esculenta hybrid. These results are confirmed by two-dimensional electrophoretic analysis of proteins in the oocytes of the three frog phenotypes. IntroductionRecent morphological and biochemical investigations of the 3 types of European green frogs indicate clearly that Rana lessonae (les) and Rana ridibunda (rid) are 2 distinct species, while Rana esculenta (esc) represents their hybrid (see references in a review by Berger2). Our previous studies on the genetic control of lactate dehydrogenase (LDH) isozymes are in agreement with such a conclusion 3,4. However, the problem is by far not so simple, since R. esculenta inter-se crosses show abnormal meiosis 5,6, reduced fertility 5 and high lethality 7,8. Yet the presence of R. lessonae is sufficient for the reproduction ofR. esculenta, as crosses between these 2 phenotypes yield always viable esculenta progeny. In order to gain more insight into this complex phenomenon further hybridization experiments have been carried out by us and special emphasis has been laid on the analysis of the lethal cross esculentaxesculenta by developmental, biochemical and immunological approaches.

The spermatophore of the silkmoth,Bombyx mori, is a reactor with a specific energy-yielding system for sperm maturation, the arginine degradation cascade. On mating, the highly viscous secretions from various glands in the male reproductive tract, which contain many enzymes and their substrates, are transferred to the female bursa (b.) copulatrix to form the spermatophore. In the spermatophore, transferred arginine-rich proteins are digested by initiatorin, an Arg-C endopeptidase of serine-protease type, and a carboxypeptidase. The produced free arginine is then hydrolyzed to urea and ornithine by arginase. Ornithine is metabolized to glutamate, follwed by forming alanine and 2-oxoglutarate. The latter, as a member of TCA-cycle, is a preferred respiratory substrate for spermatozoa and accelerates the post-testicular sperm maturation.In contrast toBombyx mori, Drosophila melanogaster produces only eupyrene spermatozoa and does not form the spermatophore. The sperm of this dipteran insect acquire motility in the v. seminalis of males. As reported forDrosophila, a high glutamate-pyruvate aminotransferase activity was found in the spermatophore as well as the v. seminalis of the silkmoth. The value in the latter organ reaches 58.3% of the whole male reproductive tract that participates in transfer of the seminal fluid.In the male reproductive system ofDrosophila, the concentration of arginine is low, whereas those of urea and ammonia are high. The accessory gland secretion contains much phosphoserine. Theses substances are transferred to female uterus with spermatozoa during mating. Most amino acids increase distinctly at 30 min after the termination of mating (ATM) and then decline, suggesting active degradation of transferred proteins in the uterus. As found inBombyx, urea increases at the post-mating period, while ornithine shows a rather low concentration. Ornithine must be converted to glutamate. In this connection, it is notable that alanine rises markedly at 30 min following mating. As in the silkmoth, the energy metabolism of the fruit fly spermatozoa involves also arginine, ornithine, urea, and proline. These findings suggest that the occurrence of the arginine degradation cascade or related metabolic pathway in this insect.

Four small nuclear RNAs (snRNAs) have been isolated from Drosophila melanogaster flies. They have been characterized by base analysis, fingerprinting, and injection into Axolotl oocytes. The size of the molecules and the modified base composition suggest that the following correlations can be made: snRNAl-U2-snRNA; snRNA2-U3-snRNA; snRNA3 -U4-snRNA; snRNA4 -U6-snRNA. The snRNAs injected into Axolotl oocytes move into the nuclei, where they are protected from degradation. The genes coding for these snRNAs have been localized by "in situ" hybridization of 125-I-snRNAs to salivary gland chromosomes. Most of the snRNAs hybridize to different regions of the genome: snRNAl to the cytological regions 39B and 40AB; snRNA2 to 22A, 82E, and 95C; snRNA3 to 14B, 23D, 34A, 35EF, 39B, and 63A; snRNA4 to 96A. The estimated gene numbers (Southern-blot analysis) are: snRNAl : 3; snRNA2 : 7; snRNA3 : 7; snRNA4 : 1-3. The gene numbers correspond to the number of sites labeled on the polytene salivary gland chromosomes.