Developmental Changes of Ecdysteroids in the Eggs of the Silkworm, Bombyx mori

Ecdysteroids were studied in relation to embryonic development and diapause of the silkworm, Bombyx mori . The majority of the ecdysteroids was found to be in the conjugated form, and minor part, in the free form. In the developing eggs, 2-deoxyecdysone, 2-deoxy-20-hydroxy-ecdysone and 3-epi-ecdysone were found to have the free ecdysteroid form as well as the conjugated ecdysteroid form. Ecdysone and 20-hydroxyecdysone almost exclusively had the conjugated form. The concentration of ecdysteroids in the embryo was higher than that in yolkplasm in the early embryonic stages. During the embryonic diapause, the concentration of free ecdysteroids decreased to a low level while the conjugated form maintained the original level.     

Effects of forest loss and fragmentation on pollen diets and provision mass of the mason bee,Osmia cornifrons,in central Japan

1. Habitat loss and fragmentation potentially affect the performance of bees that forage nectar and pollen of plants in their habitats. In forest landscapes, silvicultural conifer plantations often have reduced and fragmented natural broadleaf forests, which seem to provide more floral resources for bees than do the plantations. 2. This study evaluated the effects of forest characteristics (i.e. elevation, area, edge length, and tree size of natural forests) on pollen diets (plant taxa assemblages of pollen grains in provisions) and total provision mass in oviposited chambers in nests made by a standardised number of Osmia cornifrons bees at 14 sites in a forestry area in central Japan. 3. From April to May, the numbers of nests and chambers per nest increased, and the provision mass per chamber decreased. Main pollen sources were Prunus at higher elevations in April and Wisteria at lower elevations in May, foraging on which increased the numbers of nests and chambers per nest. The provision mass per chamber was smaller at higher elevations in more fragmented natural forests. Decreases in the area of natural forests within the foraging range (400‐m radii) of O. cornifrons increased the utilisation of Rubus pollen and decreased the total provision mass. 4. These findings suggest that the loss and fragmentation of natural broadleaf forests change pollen diets and reduce the provision mass of mason bees, which may reduce the number and size of their offspring.     

MORPHOLOGICAL OBSERVATIONS ON THE SPERMATOZOA OF ECHINOTHURID SEA URCHINS*

The morphology of the spermatozoa of three species of echinothurid sea urchins, Asthenosoma ijimai, Araeosoma owstoni, Hapalosoma gemmiferum, was investigated by means of transmission and scanning electron microscopy. The spermatozoa of these three species of echinothurid sea urchins have similar fine structure, but they differ in several features from the more familiar regular sea urchins. 1) The external anatomy of the head region of the echinothurid spermatozoon is diagnostic in that it has a highly elongated head. 2) The spermatozoon of echinothurid sea urchins has a very long slender nucleus, protruding on its proximal end, so that the shape of the nucleus resembles a sperhead. 3) The acrosomal granule in the acrosomal vesicle of the echinothurid spermatozoon is not a mass of homogenous particulate material but an electron opaque rod condensed in the central part of the acrosomal vesicle. Scanning electron microscopic examination revealed that echinothurid spermatozoa form acrosomal processes similar to those of other regular sea urchins. 4) The basal body is situated just beneath the middle of the posterior protrusion of the nucleus. The distal centriole is located beside the basal body almost in contact with it. The axis of the distal centriole is almost but not quite parallel to that of the basal body. A satellite complex can be recognized around the posterior part of the proximal centriole.     

Community‐wide effects of below‐ground rhizobia on above‐ground arthropods

1. Plants take nutrients for their growth and reproduction from not only soil but also symbiotic microbes in the rhizosphere, and therefore below‐ground microbes may indirectly influence the above‐ground arthropod community through changes in the quality and quantity of plants. 2. Rhizobia are root‐nodulating bacteria that provide NH₄⁺ to legume plants. We examined bottom‐up effects of rhizobia on the community properties of the arthropods on host plants, using a root‐nodulating soybean strain (R+) and a non‐nodulating strain (R?) in a common garden. 3. R+ plants grew larger and produced a greater number of leaves than R? plants. We observed 28 species of herbivores and three taxonomic groups of predators on R+ and R? plants. The herbivorous species were classified into sap feeders (12 species) and chewers (16 species). 4. The species richness of overall herbivores, sap feeders, and chewers on R+ plants was greater than that on R? plants. Rhizobia positively affected the abundance of chewers. 5. The community composition of herbivores was significantly different between R? and R+ plants, although species diversity and evenness did not differ. 6. Rhizobia‐induced bottom‐up effects were transmitted to the third trophic level. The abundance, taxonomic richness, and diversity of the predators on R+ plants were greater but evenness was lower than those on R? plants. The community composition of predators was not affected by rhizobia. 7. These results indicate that the below‐ground microbes initiated bottom‐up effects on above‐ground herbivores and predators through trophic levels.     

DUAL INNERVATION OF THE FOLIATE PAPILLAE OF THE RAT: AN ELECTROPHYSIOLOGICAL STUDY

The dual innervation of the foliate papillae of the rat by thechorda tympani and the glossopharyngeal nerves was determinedin this electrophysiological study. The magnitude of the chordatympani response to the chemical stimulation of the foliatepapillae was small and variable in different animals. Summatedresponses of both the chorda tympani and the glossopharyngealnerves to the stimulation of the foliate papillae showed similarpatterns such as long latencies, slowly rising responses afteronset of stimulation and slow declines by water ringing. Therelative responsiveness to 5 different chemicals applied tothe foliate papillae were almost the same for the chorda tympaniand the glossopharyngeal nerves. However, these 2 nerves produceddifferent patterns of response to various chemicals appliedto the fungiform, foliate and circumvallate papillae.     

Three Groups of Teratocarcinoma Antigens Co-Expressed in the Visceral Endoderm are Located in Mutually Exclusive Sites in the Adult Kidney

Monoclonal rat antibodies were prepared against glycoproteins isolated from murine teratocarcinoma OTT6050 by affinity chromatography on Ricinus communis agglutinin (RCA). These antibodies defined three distinct groups of antigens (OR antigens) commonly expressed in teratocarcinoma cells and in restricted sites of the kidney. OR 17 antigen was a new glycoprotein antigen and the biochemical properties were different from any membrane glycoprotiens or matrix glycoproteins so far described in teratocarcinoma cells. In the kidney, the antigen was found in the glomerular basement membrane, and to lesser extent in the endothelium of the glomerulus and blood vessels. On the other hand, OR 8 antigen corresponded to "brushin" defined by conventional antibodies, while OR 4 and 19 antigens were carbohydrate antigens resembling "TC antigen". OR 8 antigen was detected in the tubular brush border and the epithelium of Bowman's capsule. OR 4 antigen was present in the collecting tubules and the thin loop of Henle. Although OR 19 antigen showed distribution similar to OR 4 antigen, there were genetic differences in the expression of the former antigen. All of the antigens were present in early postimplantation embryos of the mouse, notably in the visceral endoderm. These antigens are interesting subjects to study the mechanism of differentiation-dependent control of gene expression, since antigenic distribution is specialized as the result of differentiation.     

INHIBITORY EFFECT OF RABBIT SERUM FACTOR ON IN VITRO OOCYTE MATURATION OF THE TELEOST FISH,ORYZIAS LATIPES*

The present study indicates that a factor in rabbit serum inhibits the in vitro steroid- and gonadotropin-induced maturation of oocytes of the teleost fish, Oryzias latipes. Such inhibitory activity could not be recognized in the serum of this fish or in the fluids from mammalian follicles. Passage of the serum inhibitor through a cellulose membrane indicated that it has a molecular weight of less than 3,500. The inhibitory activity on steroid-induced oocyte maturation was not destroyed by heating, by repeated freezing and thawing or by treatment with proteolytic enzymes, lipase or amylases. However, its activity could be removed by extraction with charcoal but not with ethyl ether or toluene. The inhibitory action of the heat-stable and dialyzable serum factor was reversible. The factor appears to exert its inhibitory effect upon the oocyte itself in an early step of maturation, rather than upon the follicle cells.