Attractive males have faster sperm in three-spined sticklebacks Gasterosteus aculeatus

Recent studies have revealed that sexually selected traits may signal sperm quality and hence male fertilisation ability. There is also evidence that the expression of male sexual ornamentation and associated sperm characteristics depend on an indi- vidual＇s ability to cope with oxidative stress. Carotenoids are known for their antioxidant properties and carotenoid-based orna- ments might represent honest signals as these pigments can be traded offbetween the investment in sexual ornamentation, sperm function as well as immune response. In this study, we examined the relationship between sexual ornamentation （breeding colo- ration） and sperm characteristics （e.g., velocity and morphology） in the three-spined stickleback Gasterosteus aeuleatus, an ex- ternally fertilising fish species, in which sperm competition commonly occurs. During the breeding season males are sperm limi- ted and develop a conspicuous carotenoid-based coloration, which is under strong pre-copulatory sexual selection due to female mate choice and male-male competition. The results of the present study show that the expression of stickleback male breeding coloration is significantly positively associated with the linearity of sperm movement, whereas sperm morphology （head length to tail length ratio） is significantly negatively related to the trajectory of sperm movement. Moreover, there is some support for the phenotype-linked fertility hypothesis as the intensity of male red breeding coloration is significantly positively correlated with sperm velocity, which is supposed to be an important determinant of fertilisation success in external fertilisers, indicating the honesty of the sexually selected nuptial red coloration.     

Structural and functional characterization of a novel, host penetration-related pectate lyase from the potato cyst nematode Globodera rostochiensis

The cell wall, a strong extraprotoplasmic layer surrounding plant cells that mainly consists of a variety of polysaccharides, constitutes a major barrier for potential parasites. Plant-parasitic nematodes are well equipped to overcome this barrier as they produce and secrete cell-wall-degrading enzymes. Expression profiling of various life stages of the potato cyst nematode Globodera rostochiensis revealed a novel pectate lyase gene ( Gr-pel2 , 759 bp). The Gr-PEL2 protein showed highest similarity to pectate lyases from the facultative plant-parasitic nematodes Bursaphelenchus mucronatus and B. xylophilus and the soil-inhabiting saprophytic Streptomyces and Frankia species (i.e. 40–42% identity and 58–60% similarity), whereas only a remote relatedness to the previously identified Gr-PEL1 was observed (i.e. 28% identity and 43% similarity). Transient expression of Gr-pel2 in leaves of Nicotiana benthamiana resulted in severe malformations of the infiltrated tissues, not relating to maceration and soft rot symptoms. Ca²⁺ is known to be essential for pectate lyase activity, and the most likely calcium-binding site was identified in the Gr-PEL2 protein by combining homology modelling of the three-dimensional structure, site-directed mutagenesis and transient expression in leaves. A highly charged cleft in Gr-PEL2, which is likely to be involved in substrate binding and which is also significantly more hydrophobic in Gr-PEL1, was shown to be essential for protein activity. Our results underline the broad spectrum of pectate lyases and cell-wall-degrading enzymes necessary for successful parasitism by cyst nematodes.     

How to analyse host discrimination

Abstract. 1. Two usual definitions of host discrimination are presented. The first is 'the ability of a parasite to distinguish unparasitized from parasitized hosts and to lay eggs in the former'. This definition is not useful and even confusing since it does not include the ability of a parasite to distinguish hosts containing different numbers of parasite eggs and to lay preferably only in those with the lowest numbers.
2. The second definition is 'the ability of a parasite to distribute its eggs in a non-random, regular way among its hosts'. It is argued that most field data are insufficient to permit any conclusions about host discriminative ability on the basis of this definition. An example is given of an apparent random distribution by parasites that are perfectly able to discriminate.
3. Arguments are given for studying the behaviour of the parasite in order to answer the question of host discrimination. Five examples of parasites are presented that would erroneously have been classified as non-discriminators on the basis of the first definition, since they all superparasitize.
4. It is suggested that the meaning of the term 'host discrimination' be extended to include the ability of a parasite to distinguish hosts with different numbers of eggs.     

Rearing conditions determine offspring survival independent of egg quality: a cross-foster experiment with Oystercatchers Haematopus ostralegus

Variation in rearing conditions, due either to parental or to environmental quality, can result in offspring of different quality (e.g. body condition, immune function). However, evidence is accumulating that egg size and composition can also affect offspring quality. In Oystercatchers Haematopus ostralegus , high-quality rearing conditions result in a higher quantity as well as quality of offspring. This is thought to be caused by increased parental food provisioning to the chicks in high-quality environments. However, variation in egg quality between rearing conditions could also affect the quantity and quality of offspring. Determining the mechanism and ontogeny of quality differences is important in unravelling the causes of variation in reproductive success. To disentangle the effects of egg quality, and quality of the rearing conditions, on the future survival of offspring, we cross-fostered complete clutches between nests. When reared under conditions of similar environmental quality, chicks originating from eggs laid in low-quality environments survived as well as chicks originating from eggs laid in a high-quality environment. However, chicks reared in high-quality environments survived twice as long as chicks reared in low-quality environments, independent of the environmental quality in which the eggs were laid. This suggests that variation in the future survival of offspring is primarily caused by differences in environmental and/or parental quality, with no clear effect of egg quality (size).     

EVIDENCE THAT SALIVARY PROTEINS ARE INVOLVED IN ASTRINGENCY

Proteins in saliva samples taken from twelve subjects immediately before and immediately after tasting astringent solutions were analyzed by high performance liquid chromatography. Although considerable variation in both the qualitative and quantitative protein pattern was observed among individuals, three peaks appeared to be common to the majority of the chromatograms. The tasting of the astringent solutions resulted in detectable changes in the protein profile of the saliva samples, observed in all the chromatograms examined, and attributed to the interactions of the saliva proteins with the astringent phenolic compounds. The appearance of a major peak at 8 min after the tasting of the astringent compounds common to most of the saliva chromatograms was attributed to the formation of soluble protein-phenol complexes.     

Ultrastructure and Development of Oil Idioblasts in Annona muricata L.

The ultrastructure and development of oil idioblasts in theshoot apex and leaves in Annona muricata L. are described, andthree arbitrary developmental stages are distinguished: cellsin which no additional cell wall layers have been depositedagainst the initial primary cell wall, possessing an electron-translucentcytoplasm and distinct plastids which lack thylakoids (stage1); cells in which a suberized layer has been deposited againstthe primary wall (stage 2, the cytoplasm resembles that of thepreceding stage), and cells in which an additional inner walllayer has been deposited against the suberized layer, whichincreases in thickness with development (stage 3). In this stagean oil cavity is formed, surrounded by the plasmalemma, andattached to a bell-like protrusion of the inner wall layer,the cupule. A complex membranous structure occurs next to thecupule. Smooth tubular endoplasmic reticulum (ER), appearingas linearly arranged tubules, and groups of crystalline bodieswith an almost hexagonal outline are present. The final stagewas further subdivided into three subgroups (a, b, c) basedon the extent of the oil cavity, its contents, and the compositionof the cytoplasm, and increasing thickness of the inner walllayer. The oil is probably synthesized in the plastids, releasedinto the cytoplasm, and then passed through the plasmalemmasurrounding the oil cavity. Oil idioblasts, Annona muricata L., suberized layer, inner wall layer, oil cavity, cupule, smooth tubular ER, crystalline bodies     

Changes in the sexual tendency accompanying selection for aggressiveness in the three-spined stickleback,Gasterosteus aculeatus L.*

Independent selection experiments for reduced juvenile and reduced territorial aggression levels in male three-spined sticklebacks both resulted in reduced courtship aggression levels. In the low juvenile aggression line this is accompanied by an enhanced sexual activity, but in the low territorial aggression line males display a reduced sexual activity. These results are consistent with a mutually inhibitory relationship between the aggressive and sexual tendencies, if selection for juvenile aggressiveness has only affected the aggressive tendency while selection for territorial aggressiveness has simultaneously affected the aggressive and sexual tendencies in the same direction. This is in agreement with the hormonal changes (pituitary-gonadal axis) suggested by the selection studies.     

Effects of contrasting omnivorous fish on submerged macrophyte biomass in temperate lakes: a mesocosm experiment

1. Freshwater fish can affect aquatic vegetation directly by consuming macrophytes or indirectly by changing water quality. However, most fish in the temperate climate zone have an omnivorous diet. The impact of fish as aquatic herbivores in temperate climates therefore remains unclear and depends on their dietary flexibility. 2. We tested the effects of a flexible omnivore and an herbivore on aquatic vegetation by comparing the effects of rudd (Scardinius erythrophthalmus, the most herbivorous fish in temperate climates) with grass carp (Ctenopharyngodon idella) in a mesocosm pond study. Exclosures distinguished herbivorous effects of fish on submerged macrophytes from indirect effects through changes in water quality, whereas stable isotope food‐web analysis provided information on fish diets. 3. We hypothesised that rudd, with its flexible diet and preference for animal food items, would only indirectly affect macrophytes, whereas grass carp, with its inflexible herbivorous diet, would directly affect macrophyte biomass. 4. Only grass carp significantly reduced macrophyte biomass through consumption. Rudd had no effect. Food‐web analysis indicated that rudd predominantly consumed animal prey, whereas grass carp included more plants in their diet, although they also consumed animal prey. Grass carp significantly affected water quality, resulting in lowered pH and increased N‐NH₄ concentrations, whereas more periphyton growth was observed in the presence of rudd. However, the indirect non‐herbivorous effects of both fish species had no effect on macrophyte biomass. 5. Both fish species should be considered as omnivores. Despite the fact that rudd is the most herbivorous fish in the western European climate zone, its effect on submerged macrophyte biomass is not substantial at natural densities and current temperatures.