A snail prefers native over exotic freshwater plants: implications for the enemy release hypotheses

1. One of the most popular single‐factor hypotheses that have been proposed to explain the naturalization and spread of introduced species is the enemy release hypothesis (ERH). Most studies have considered how specialist consumers might affect the success of exotics, but the importance of generalist herbivores has received little attention 2. In this study, we compared the palatability of native and exotic freshwater plants in both phylogenetic pairings and in region‐wide assays, using a generalist consumer (the pond snail Radix swinhoei). 3. Our study indicated that, when plants were paired by taxonomic relatedness, the snail preferred native over exotic freshwater plants by a 2 : 1 ratio. The snail also preferred native over exotic plants when tested across 20 native and seven exotic species found growing in Liangzi Lake. 4. Snails consumed more biomass of native than exotic plants, providing support for the ERH and suggesting that exotic species have a potential advantage in most lakes of the middle and lower reaches of the Yangtze River in China, thus helping their invasion.     

Indirect Immunofluorescence Microscopy of Microtubular Structures in Male Germ Cells of Wildtype and l(3)pl (lethal-polyploid) Drosophila hydei

Tubulin-containing structures of the male germ cells of Drosophila hydei crossreact in indirect immu-nofluorescence microscopy with antibody directed against homogeneous porcine brain tubulin. There is no detectable difference in reactivity between germ cells of wildtype flies and the mutant l(3)pl (lethal-polyploid) which is characterized by microtubular abnormalities. However, the technique of indirect immunofluorescence microscopy allows the direct visualization of several abnormalities in the arrangement of the microtubular system of the mutant, particularly in the axonemal complex.     

Studies of Unequal Cleavage in Molluscs: I. Nuclear Behavior and Anchorage of a Spindle Pole to Cortex as Revealed by Isolation Technique

Unequal division of the eggs of Spisula solidissima was studied by isolating the nuclear elements. The isolation technique consists mainly of the use of Na-lauryl sulphate with occasional inverting of the container of alcohol-fixed eggs. The procedure was applied to the following stages. (1) germinal vesicles, (2) 1st maturation division, showing anchorage of a spindle pole to the cortex, (3) 2nd meiosis, (4) pronuclear encouter, (5) metaphase, (6) shifting of the metaphase spindle to one side of the cell and a contact with the cortex, (7) ana- and telophase of the 1st division.
Migration and "anchorage" of the spindle to the cortex by one pole is a common phenomenon in unequal divisions of polar body formation and of egg cleavage.     

Conservation of Aquatic Insects: Worldwide Crisis or Localized Threats?

An overview is presented on the current worldwide status ofaquatic insect conservation. Despite extensive habitat destructionor modification, aquatic insects as a whole do not appear tohave suffered as great a proportional loss of species over thelast century as members of other groups. In North America, forexample, only 204 species are considered at risk out of a totalfauna of over 10,000 species, and no species has been documentedas having gone extinct. Even so, aquatic insect diversity issubject to a broad spectrum of threats, including chemical pollutionof waters from industry and agriculture, physical destructionof habitat from impoundments or drainage, and introduction ofalien aquatic biota, primarily sport or aquarium fishes. Adequatelegislation exists in the United States and Europe to provideprotection to aquatic insect taxa at risk, but the implementationof this legislation is often hampered by a lack of taxonomicand distributional knowledge, and by a concentration of recoveryefforts on more highly visible vertebrate taxa. The case ofthe Ash Meadows Naucorid, the only aquatic species currentlyprotected under the Endangered Species Act, is examined in detail.It is concluded that the listing of this species has had nodiscernable effect in halting its population decline, partlydue to the fact that recovery efforts for endangered fisheshave proven deleterious to the insect. It is recommended thatfuture listing efforts be conducted in the context of nationalbiological surveys, and that an ecosystem rather than singlespecies approach be applied to aquatic conservation efforts.     

Importance of feeding ecology to the reproductive success of Blackbirds Turdus merula nesting in rural habitats

The feeding ecology of Blackbirds Turdus merula breeding in contiguous woodland and farmland habitats was studied over three years. The aim of the study was to investigate how reproductive success was influenced by nestling diet and the provisioning rates of parents feeding nestlings. Parental provisioning rates increased with brood size, and consequently individual nestlings were no lighter in larger broods. None of the environmental factors measured had strong effects on parental provisioning rate. The nestling diet was dominated by caterpillars and earthworms, the former occurring in a short period in the middle of the breeding season. The availability of earthworms was higher in woodland and was dependent on rainfall in farmland. Nestling mass and provisioning rates were marginally higher under predominantly earthworm diets. Nestling mass increased with rainfall in farmland only, and was higher in farmland than in woodland or woodland-edge, although it is doubtful whether this result is of any significance for fledgling survival. Overall, Blackbirds were able to provision their nestlings adequately throughout the breeding season across a range of conditions. There was no evidence to suggest that reproductive success was constrained by aspects of feeding ecology within the natural range of brood size.     

HORMONAL CONTROL OF ROOT GROWTH I

The growth of the primary root of a single gene dwarf mutantof Zea mays L., dwarf-1, is dependent upon gibberellic acidor one of its derivatives as a growth hormone. Moreover, forthe root to respond to gibberellin treatment both embryonicand mature tissues must contribute growth stimuli. ¹ This study was financed by the National Institute of Health,Grant GM 08706-03.     

Distribution and linkage disequilibrium analysis of polymorphisms of <Emphasis Type="Italic">GH1</Emphasis> gene in different populations of pigs associated with body size

Growth hormone (GH) has been considered as a candidate gene for growth and body size in pigs. In this study, polymorphisms of the GH1 gene were evaluated for associations with body size traits in 190 pig individuals. Seventeen single-nucleotide polymorphisms (SNPs) were identified in GH1 gene of the large pig breeds and miniature pig breeds using direct sequencing and genotyped by allele-specific PCR approach. Notably, six (g.237A>G, g.283T>C, g.309A>G, g.318A>G, g.540A>G and g.544A>G) of them were significantly associated with body size, of which three loci (g.283T>C, g.309A>G, g.318A>G) located in the signal-peptide coding region of GH1 gene compose a CGG haplotype for large pigs and TAA haplotype for miniature pigs (P< 0.001), two loci (g.540A>G and g.544A>G) located in the second intron of GH1 gene compose a GG haplotype for large pigs and AA haplotype for miniature pigs (P< 0.001). Our results demonstrate that these SNPs in GH1 gene are associated with the body size of pigs providing genetic basis for pig breeding with the improved economic benefits.