Proportion Of Hermaphrodites Research Articles

Low Concentrations of Silver Nanoparticles Inhibit Spore Germination and Disturb Gender Differentiation of Ceratopteris thalictroides (L.) Brongn

Because of their excellent antibacterial properties, silver nanoparticles (AgNPs) are widely used in all walks of life, which has caused them to be discharged into aquatic environments with possible negative effects on aquatic plants. In the present study, we used an aquatic fern, Ceratopteris thalictroides, as a model to investigate the effects of AgNPs on its spore germination, gametophytes, sex differentiation, and growth. The results demonstrated that AgNPs significantly inhibited spore germination of C. thalictroides at a AgNP concentration higher than 0.02 mg/L. Additionally, we found sex-dependent effects of AgNPs on the development and growth of the gametophyte of C. thalictroides. The proportion of hermaphrodites in the gametophytes and the area of gametophytes significantly decreased under AgNP treatment, while no significant effect was observed in the male gametophytes. Using the AgNP filtrate (without nanoparticles) and AgNPs plus cysteine (Ag+ chelator), we found that the release of Ag+ from nanoparticles was not the cause of the toxicity of AgNPs on C. thalictroides. The EC50 of AgNPs on spore germination was 0.0492 mg/L, thus indicating an ecological risk of AgNPs on this species even at concentrations lower than the Ag element concentration of the WHO guidelines for drinking-water quality.

The Effect of Macronutrient Availability on Pomegranate Reproductive Development

Pomegranate cultivation has expanded significantly in the last two decades. However, there is limited information on its fertilization requirements and the effect of macronutrient availability on its reproductive development. Two commercial pomegranate cultivars—“Wonderful” and “Emek”—were grown in 500-L containers for 3 years, using a fertigation system. Development and reproduction indices were measured to explore the trees’ responses to elevated levels of nitrogen (N), phosphorus (P) and potassium (K) in the irrigation solution. Andromonoecy rate was affected by nutrient levels only in the first year of the experiment, with higher levels of N and P leading to a greater proportion of hermaphrodites out of total flowers. P level had a positive effect on the total number of hermaphrodites per tree in both varieties. Differences recorded between hermaphroditic and staminate flowers included nutrient concentrations and dry weight. Fruit set and aril number were positively affected by N concentration in the irrigation solution. We conclude that only a severe deficiency of N and P affects the andromonoecy trait, and that at the levels examined in this study, K hardly influences pomegranate reproduction.

Sexual System and Ecological Links of Flowering Plants in Changbai Mountain

We studied 1,403 species, 102 families and 473 species of flowering plants in Changbai Mountain Nature Reserve. Based on the data and field investigation, the plant sexual form, life form, flower characteristics, pollination type and fruit type were recorded. The pattern of plant sexual system of flowering plants was inspected, and the relationships between biological and ecological characteristics of flowering plants and plant sexual system were investigated. The results showed that the monoecious, dioecious, and hermaphroditic species accounted for 13.26, 2.13, and 81.61%, respectively. The proportion of hermaphrodites and monoecious plants was higher, and the plant sexual system was related to species richness and phylogeny. Most of the monoecious plants were tree species, and the dioecious plants were mostly trees, shrubs and lianas, and the hermaphroditism was mostly herbaceous plants. The morphological characteristics of flowers were significantly related to the sexual system. The monoecious and dioecious plants were mostly actinomorphic, yellow-green and green-brown small flowers. However, the hermaphroditism flowers were mostly zygomorphic and medium and large sizes with white, blue-purple and pink colors. The dioecious plants were related to generalist entomophily and anemophily, while the hermaphroditism was mainly generalist and specialist entomophily. The plant sexual system was also correlated with plant fruit types. The monoecious and dioecious plants always had dry fruit and the hermaphroditism had fleshy fruit.

Patterns of flowering and sex-ratio variation in the Mediterranean shrub Phillyrea angustifolia (Oleaceae): implications for the maintenance of males with hermaphrodites

The Mediterranean shrub Phillyrea angustifolia is one of the few plants that display androdioecy, a rare breeding system in which males co-occur with hermaphrodites. However, it has been difficult to account for male frequencies previously documented for this species, which have frequently been higher than 0.5. Here we present sex-ratio data from 13 sites in Spain and Portugal that throw further light on the maintenance of androdioecy in P. angustifolia. The inferred proportion of males in these populations was around 0.3, substantially lower that 0.5 and concurring with theoretical predictions for androdioecy. Differences in the proportion of hermaphrodites in flower between “stressed” and “nonstressed” sites suggest the existence of an important life-history trade-off between fruit production and the rate at which plants recover from recurrent disturbances such as fire. The reduced frequency of flowering by hermaphrodites relative to males may help to explain the maintenance of androdioecy in this long-lived, woody species.

Environmental factors affecting sexual differentiation in the entomopathogenic nematode Heterorhabditis bacteriophora

The present study was aimed at determining the influence of various environmental factors on sex differentiation (SD) in the entomopathogenic nematode Heterorhabditis bacteriophora HP88 strain, under in vivo and in vitro culture conditions. Injection of individual nematodes into last instars of Galleria mellonella resulted in development of a similar number of females and hermaphrodites (35–40%) and 20–25% males. Increasing the number of nematodes injected into the insect did not change these proportions. In smaller insects (0.7–1.5 cm long), an increase in the proportion of hermaphrodites was recorded as compared with larger size cadavers (2.4–2.7 cm long). When individual hermaphrodites were placed on NGM, the proportion of hermaphrodites, females and male progeny was 63%, 31%, and 6%, respectively. Rearing on richer medium (“Dog-food” agar) resulted in reduction in the proportion of hermaphrodites. Nematodes introduced to the symbiotic bacterium obtained from other nematode strains (IS-5 and IS-33) developed similarly to the culture reared on the HP88 bacteria. Rearing the nematodes at a temperature range between 21°C to 30°C also did not have a significant effect on the sexual differentiation among nematodes cultured on NGM. The proportion of hermaphrodites increased as the starvation period of hatching nematode juveniles lengthened (>6 hr). The data obtained in the present study strongly suggest that the main factor affecting sex differentiation in H. bacteriophora is the nutrition source. The practical and biological implications of the results are discussed. J. Exp. Zool. 287:158–166, 2000. © 2000 Wiley-Liss, Inc.

Environmental factors affecting sexual differentiation in the entomopathogenic nematodeHeterorhabditis bacteriophora

The present study was aimed at determining the influence of various environmental factors on sex differentiation (SD) in the entomopathogenic nematode Heterorhabditis bacteriophora HP88 strain, under in vivo and in vitro culture conditions. Injection of individual nematodes into last instars of Galleria mellonella resulted in development of a similar number of females and hermaphrodites (35-40%) and 20-25% males. Increasing the number of nematodes injected into the insect did not change these proportions. In smaller insects (0.7-1.5 cm long), an increase in the proportion of hermaphrodites was recorded as compared with larger size cadavers (2.4-2.7 cm long). When individual hermaphrodites were placed on NGM, the proportion of hermaphrodites, females and male progeny was 63%, 31%, and 6%, respectively. Rearing on richer medium ("Dog-food" agar) resulted in reduction in the proportion of hermaphrodites. Nematodes introduced to the symbiotic bacterium obtained from other nematode strains (IS-5 and IS-33) developed similarly to the culture reared on the HP88 bacteria. Rearing the nematodes at a temperature range between 21 degrees C to 30 degrees C also did not have a significant effect on the sexual differentiation among nematodes cultured on NGM. The proportion of hermaphrodites increased as the starvation period of hatching nematode juveniles lengthened (>6 hr). The data obtained in the present study strongly suggest that the main factor affecting sex differentiation in H. bacteriophora is the nutrition source. The practical and biological implications of the results are discussed.

Growth and reproductive characteristics in artificially formed clonal gametophytes ofDryopteris filix-mas (Dryopteridaceae)

Artificially formed clonal gametophytes ofDryopteris filix-mas (L.)Schott were able to grow and reproduce, although growth rates, proportions of hermaphrodites and reproductive efforts were low. Variable density and nutrient levels appeared to affect gametophytic life histories and they continued to influence the viability of the developing sporophyte generation. Differences between populations and sporophytes were discovered in life histories. Hermaphroditic gametophytes were considerably larger and possessed higher viability than did males. Clear differences between clones in the level of phenotypic plasticity in gametophyte size were observed. No neighbor effect on gametophyte sex expression was detected with the densities and nutrient levels used.

FUNCTIONAL DIOECISM IN THE MALPIGHIACEAE: THE BREEDING SYSTEM OF SPACHEA MEMBRANACEA CUATR

The breeding system of Spachea membranacea (Malpighiaceae), an understory tropical rain forest tree, was studied on Barro Colorado Island in central Panama. Two types of trees were found, those with hermaphroditic flowers and those with female flowers. Crossing experiments indicated that morphological hermaphrodites normally function as males but may be induced to set fruit if emasculated prior to cross‐pollination. Thus, although morphologically gynodioecious, S. membranacea is functionally dioecious. This is the first experimental evidence for functional dioecism in the Malpighiaceae. The proportions of hermaphrodites (functional males) in the three populations examined were 44.7% (N = 47), 60.0% (N = 10), and 87.5% (N = 17). The distribution of hermaphrodites and females in size classes was quite similar, suggesting that sexual expression is not influenced by the age of the individual. Flowers are visited and presumably pollinated primarily by bees of the genera Paratetrapedia (Anthophoridae) and Trigona (Apidae).

THE EFFECT OF LOW DENSITY ON THE DEVELOPMENT OF SIMULTANEOUS HERMAPHRODITISM IN MALECAPITELLASPECIES I (POLYCHAETA)

ABSTit@crr In this study it was shown that male Capitella species I may develop into si multaneous hermaphrodites ifreared in isolation or at low densities in the laboratory. Since hermaphroditic development is rare in high density non-inbred cultures but becomes frequent in inbred lines which have been selected for high male sex ratios, the ability to become hermaphroditic seems to have a genetic basis. It is also suggested that low density may trigger the hermaphroditic development of males through the absence of animals with female gonads. Excess food resources which could be assim ilated at low density and may be directed into the development of a second set of reproductive structures and female gametes, could also be a factor in the male-to hermaphrodite switch. Capitella sp. I has an opportunistic lifestyle which could ac commodate such a sexual adaption. The larvae are widely dispersed which would often cause adults to be at low density where the advantage of being hermaphroditic is well known. IrsrrRoDUcrION Much ofthe scientific interest in the genus Capitella stems from its “?�opportunistic” life history (Grassle and Grassle, 1974) which has made it an important indicator of environmental disturbance in the benthos (Henrikkson, 1969;Pearson and Rosenberg, 1978; Sanders et a!., 1980). Formerly known as Capitella capitata, electrophoresis has shown it to be a complex of at least ten sibling species (Grassle and Grassle, 1976, 1977; Grassle, 1980). The different species are morphologically similar but differ in life histories and reproductive strategies. The most opportunistic species, which is distinguished by larvae which remain in the planktonic stage for several hours, is Capitella species I. This species is the main one under consideration here. Males, females, and hermaphrodites are found in natural populations or Capitella sp. I. Hermaphrodites are found only infrequently, appearing when mature males develop female gonads. Families raised in the laboratory from individual eggcases have extremely variable sex ratios and successful selection can be made for inbred lines with a high proportion of males and females (Grassle, 1980). Both facts suggest that there may be a polygenic sex determining mechanism (Kossig, 1964). If selection is made for a highly male sex ratio, the proportion of hermaphrodites that develop will also increase. The discovery that motivated this research was that young non inbred males of species I and II developed female gonads, thus becoming hermaph rodites, if reared in isolation. Previously, hermaphrodites were observed to develop in old, high density, non-inbred laboratory cultures only. Hermaphrodites are never