Isolation and characterization of 49 polymorphic microsatellite loci in the ayu,Plecoglossus altivelis

A total of 49 novel polymorphic microsatellite markers in the ayu fish, Plecoglossus altivelis, were successfully isolated and characterized. The number of alleles per locus, observed heterozygosity, and expected heterozygosity ranged from two to 25 (11.3 on average), from 0.125 to 1.000 (0.648 on average), and from 0.123 to 0.957 (0.751 on average), respectively. These microsatellite markers will be useful for both studying population structure and identifying quantitative trait loci that control evolutionarily and economically important traits of ayu.     

Morphological and genetic analysis of fish of a Carassius complex (Cyprinidae) in Lake Kasumigaura with reference to the taxonomic status of two all-female triploid morphs

The classification of the Carassius complex (Cyprinidae) including all-female triploids, called ginbuna in Japanese, is so confused that three sympatric morphs of crucian carp in Lake Kasumigaura are categorized into two different subspecies within a species. We examined them in order to explain the coexistence of more than one subspecies and determine the founder of the triploid lineages in the crucian carp fauna in the lake. Principal component analysis proved that the three sympatric morphs had a morphometric basis distinguishable from each other. Ploidy was determined by flow cytometry which showed triploids in two morphs and diploids in the other morph. Stepwise discriminant analysis using only meristic characteristics could separate the diploids from the triploids. Phylogenetic analysis using mitochondrial DNA inferred two lineages in which one was composed of a triploid morph and the other was a diploid–triploid mixture. Disagreement between the taxonomic status and the phylogenetic status is explicable by assuming that the triploids in the Carassius complex had independent origins leading to the different subspecies. C. auratus langsdorfii appears to show genetic complexities that traditional taxonomic classification can not unravel.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 351–357.     

NUTRITIONAL STUDIES OF A YEAST

The present work deals with essential growth factor requirementsof a haploid strain of Saccharamyces sp., strain 19861, whichexhibits requirements for lysine, arginine and histidine.

1. The strain requires Ca-pantothenate, biotin and thiamine inaddition to the three amino acids.
2. In a synthetic medium containingthese amino acids and the threevitamins, tryptophan could replacehistidine completely.
3. Pyridoxine, leucine, isoleucine andvaline, as a group, couldreplace thiamine in the presence ofinositol.
4. In the above substitution, leucine could be removedwhen excessivevaline was added, the optimal ratio of isoleucineto valinebeing about 1:3 in the presence of tryptophan, insteadof histidine.
5. In a isoleucine-deficient medium, flocculationoccurred in fiveor more days.

(Received March 3, 1961; )     

Control of Aphis gossypii and Myzus persicae (Hemiptera: Aphididae) by a flightless strain of Harmonia axyridis (Coleoptera: Coccinellidae) on green pepper plants in open fields

The cotton aphid Aphis gossypii Glover and the green peach aphid Myzus persicae (Sulzer) are economically important pests with a worldwide distribution. We evaluated the efficacy of releasing a flightless adult strain of the multicolored Asian lady beetle Harmonia axyridis (Pallas) as a control measure against these aphids on green pepper plants in open fields. Flightless H. axyridis adults were observed on the green pepper plants in the releasing plots throughout the experimental period and were found to be effective biocontrol agents, markedly decreasing the numbers of aphids. These results suggest that adults of this flightless strain of H. axyridis are effective in controlling aphids on green pepper plants in open fields.     

A seed parasitoid wasp prevents berries from changing their colour,reducing their attractiveness to frugivorous birds

1. Frugivorous and seed‐feeding insects may alter the traits of fruits, such as shape and size, which may influence fruit attractiveness to frugivorous birds. Consequently, trait‐mediated interactions may occur in systems where plants, seed‐dispersing frugivorous vertebrates, and frugivorous or seed‐feeding insects interact. We investigated colour manipulation in Ilex integra Thunb. berries caused by the seed parasitoid wasp Macrodasyceras hirsutum Kamijo and how that manipulation relates to fruit attractiveness for frugivorous birds. 2. In winter, the colour of I. integra berries varied from green to red, but most berries were greenish, indicating that the berries were immature. Berry dissection indicated that the number of live parasitoid larvae present within each berry was closely related to berry colour – the greater the number of live larvae, more intense is the green colour of the berry. However, the wasp larvae did not modify the shape or size of the berries. More than 98% of berries that were protected from the insects by gauze bags ripened and turned red. In the present study, berries with unfertilised seeds alone turned red. Field‐feeding preference tests showed that the brown‐eared bulbul Hypsipetes amaurotis Temminck preferred red berries to green berries. 3. We demonstrated that the seed parasitoid wasp manipulates the berry colour, but not its shape or size, in a density‐dependent manner. Because green berries suffered less from bird foraging, we believe that this colour manipulation helps the wasps to avoid being killed by the birds. The present study indicates that manipulation by wasps may reduce the level of mutualism between the tree and seed‐dispersing birds.     

Impact of indigenous egg eaters on the early survival of exotic smallmouth bass

Exotic species become invasive aliens when they have an adverse effect on the community of the recipient ecosystem, and their spread among closed water systems is of recent concern for the conservation of native biodiversity in Japan. Smallmouth bass (Micropterus dolomieu Lacepède) is recognized as one of the worst 100 alien species, being undesirable because of its trophic level as a top predator. Smallmouth bass that have been illegally introduced into Lake Aoki, central Japan, in the 1990s for the purpose of sports fishing have seriously affected the lower trophic levels in the lake including fisheries resources, while a strong effort to remove them has proved to be limited in usefulness. We intended to identify indigenous agents that have a potential to control smallmouth bass in the lake. Snorkeling observations in the daytime revealed that Japanese dace (Tribolodon hakonensis Günther) intruded into smallmouth bass spawning nest as a school and were able to consume the eggs while the male bass was guarding the nest. Consequently, the proportion of lost eggs owing to the predation reached 92.4% per clutch on average, proving that native cyprinids are able to function as an efficient egg predator that reduces the survival of smallmouth bass. We consider that employing the indigenous egg predator can be a practical means to eradicate exotic smallmouth bass, combined with the removal of stones on the nest as a subsidiary step to expose smallmouth bass eggs to predation by Japanese dace.     

MITOTIC ACTIVITY OF VAGINAL EPITHELIAL CELLS FOLLOWING NEONATAL INJECTIONS OF DIFFERENT DOSES OF ESTROGEN IN MICE

In C57Black/Tw mice given injections of 1 μg estradiol-17β (E) for 5 days beginning on the day of birth, and killed a few days after the treatment, the vaginal epithelium showed estrogen-dependent proliferation and parakeratosis. In contrast, in the mice treated neonatally with 30 μg E for 5 days, the vaginal epithelium exhibited estrogen-independent proliferation and cornification or parakeratosis. Two peaks occurred in the mitotic rate in vaginal epithelial cells in the proximal and middle vaginae of the 1 μgE-treated mice, at 1 and 5 days of age, respectively, while the first peak was lacking in the distal vagina. The mitotic activity in 1 μgE-treated mice declined to the control level at 60 days. In the 30 μgE-treated animals also, 2 peaks were found in the mitotic rate at 1 and 7 days in both the proximal and middle vaginae. In contrast to the 1 μgE-treated mice, although the rate dropped once at 10 days, it increased again at 20 days and remained high thereafter. The second peak at 7 days of age coincided with the active proliferation of nodules appearing in the 30 μgE-treated mice. In the distal vagina, a peak occurred in the mitotic rate at 7 days without a preceding peak like that observed in the other parts of the vagina following the first injection of E on the day of birth.     

Difference in parasite load and nonspecific immune reaction between sexual and gynogenetic forms of Carassius auratus

For coexistence, the sexual form in sexual/asexual complexes needs short-term advantages that can compensate for the two-fold disadvantage of sex. Higher mortality in the asexual form due to a higher parasite load will provide an advantage to the sexual form. In Lake Suwa, Japan, the parasite load (Metagonnimus sp.; Trematoda) of triploid gynogenetic females of Carassius auratus was significantly higher than that of diploid sexual females. In an immunoassay using healthy wild fish that were conditioned for 1 month in laboratory tanks, the nitroblue tetrazolium (NBT) immune reaction of sexual females was significantly higher than that of gynogenetic females. The NBT activity indicates the abundance of oxygen radicals from phagocytes, and hence the level of immune activity of the phagocytes. We suggest that the higher parasite load of the gynogenetic form is in part due to the lower immune activity of the phagocytes (nonspecific immune reaction) in the gynogenetic form compared to the sexual form.