Sexual reproduction Research Papers - Academia.edu (original) (raw)

To increase the quality of cryopreserved sperm in white rhinoceros, the liquid nitrogen vapour (LN vapour) freezing and the multithermal gradient directional freezing methods were compared. Sixteen white rhinoceros (Ceratotherium simum sp.) were electroejaculated. Semen samples were diluted with cryoextender (Tris, lactose, egg-yolk, DMSO) and aliquoted into straws for LN vapour freezing, and glass hollow tubes for directional freezing. The sperm quality was evaluated before and after freezing by assessing the following parameters: motility, morphologic state, acrosomal integrity and plasma membrane function and integrity (i.e. sperm viability) as defined by the hypo-osmotic swelling. Directional freezing improved the sperm viability by 5.6% ( p < 0.005), progressive motility score by 34.7% and sperm motility index (SMI) by 8.1% ( p < 0.005) versus LN vapour freezing. When data was categorized into groups of low (<19%), moderate (20-39%) and high (>40%) percentages of morphologically normal, directional freezing (DF) resulted in 31.4% less abnormal acrosomes for the low quality group as well as 18.7% increase in intact acrosomes and 10.9% increase in motility for the high quality group compared to LN vapour freezing (LN) ( p < 0.01, p < 0.03, p < 0.01, respectively). LN showed a significant reduction in sperm head volume (5.7%, p < 0.05) compared to the prefreeze; whereas, no significant reduction in head volume was demonstrated after DF. Several additives (xanthenuric acid, cytochalasin D, potassium, EDTA) to the basic cryoextender provided no significant improvement in spermatozoal survival after directional freezing. In conclusion, directional freezing proved to facilitate higher gamete survival compared to LN vapour freezing. This is especially effective in ejaculates of low sperm quality and is important in endangered species where high quality semen donors are often not accessible. These results suggest that directional freezing could be valuable particularly for species with limited freezability of spermatozoa. #

- by and +1
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- Reproduction, Cryopreservation, Endangered Species, Theriogenology

The plant disease Apple Scab, caused by the ascomycete fungus Venturia inaequalis (Cke.) Wint. (anamorph Spilocea pomi Fr.), is the single most important disease of cultivated apple (Malus domestica Borkh.) worldwide. Severe apple crop losses can result when appropriate control measures are not taken, especially when the spring and early summer seasons are moist and cool. The fungal pathogen has a pronounced low temperature requirement for the initiation of the sexual or pseudothecial stage. In temperate apple growing regions of the world, this temperature requirement is met only after leaf fall, on the orchard floor, where, in winter months, low temperatures trigger the development of pseudothecia. In the spring, overwintered pseudothecia time their production of ascospores to precisely coincide with the emergence of new leaves, thus initiating a new cycle of disease.

- by Stanley Freeman
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- Seasonality, Primer design, Life Cycle, Fungal Pathogens

Although stony corals are most frequently studied on high-relief reef structures, many coral species occur in a wide variety of nearshore tropical habitats, including mangrove creeks, seagrass beds and rocky platforms. This study estimated overall population size, potential reproductive output, and population structure for several species across sandy-bottom, hard-bottom, and patch reef habitats. The density of coral colonies, area of available habitat, and size distribution of resident Siderastrea radians, Favia fragum, and Diploria clivosa colonies were recorded for several island bank systems across habitat types in the central Bahamas. Nearshore patch reefs generally exhibited larger population sizes and higher density of colonies, and contained more larger or older colonies. Nearshore hardbar communities had smaller population sizes and a lower density of colonies, and supported more small colonies, which may either be recruits or asexual clones. High numbers of larger colony s...

- by Kathleen Sullivan Sealey
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- Population structure, Habitat Selection, Population Size, Banking system

A novel species in the genus Candida was obtained from deep-sea hydrothermal fields on the Mid-Atlantic Ridge. Strains Mo39, MARY089 and CBS 5307, respectively, isolated from an unidentified deep-sea coral collected near Rainbow hydrothermal vent, from water samples near Menez Gwen hydrothermal field and from the stomach of a marine fish are considered as a novel taxon. Sequence similarities in the D1/D2 region of the 26S rRNA gene indicated that strains Mo39, MARY089 and CBS 5307 have for closest neighbors Candida spencermartinsiae, Candida taylorii, Candida atmosphaerica and Candida atlantica. The strains, respectively, differ from C. spencermartinsiae, C. taylorii, C. atmosphaerica andCandida atlantica by 4, 4.3, 4.3 and 4.7% in the D1/D2 domain. Strains Mo39, MARY089 and CBS 5307 were differentiated from others by differences in the ability to assimilate d-Gluconate and in the ability to grow at relatively high temperature. Only strain Mo39 displays an optimal growth at 3% sea salts, indicating that this strain is clearly adapted to live in marine conditions. Sequence similarities between strains Mo39, MARY089 and CBS 5307 and related species and differences in the ability to utilize specific carbon compounds revealed that these strains represent a hitherto unknown species. Sexual reproduction was not observed in strains Mo39, MARY089 and CBS 5307. An anamorphic name Candida oceani sp. nov. is proposed for the type strain Mo39T (= CBS 11857T = DSM 23777T) and the two other strains MARY089 and CBS 5307. To our knowledge, this is the first description of a micro-eukaryotic organism including a strain isolated from a deep-sea coral near a hydrothermal ecosystem.

- by Gaëtan Burgaud
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- Microbiology, Medical Microbiology, Phylogeny, Anthozoa

Carob (Ceratonia siliqua L.) is a caesalpinoid legume tree showing labile sex expression. With the main aims of identifying flower-expressed genes and of developing specific markers, 1,056 clones from a complementary DNA library of carob flowers were bidirectionally sequenced. A total of 1,377 high-quality expressed sequence tags were clustered into 1,096 unigenes. Basic Local Alignment Search Tool and Gene Ontology functional annotation allowed to identify several agronomically important genes, such as those involved in flower development and sexual reproduction, response to stress, galactomannan synthesis, and hormone pathways. Genes involved in the ethylene biosynthesis and response were quantified in developing flowers of three sex genotypes (male, female, and hermaphrodite) using quantitative reverse transcription polymerase chain reaction. The transcript levels of 1-aminocyclopropane-1-carboxylic acid oxidase, acting downstream in ethylene pathway, and Ethylene Insensitive 3 (EIN3)-like, a transcription factor involved in ethylene signaling, were directly correlated with maleness, indicating a possible role of ethylene in carob sex expression. Furthermore, the first set of carob genic microsatellites was developed, which might be useful for genotyping and genetic diversity analysis.

- by Alessandra Gentile and +1
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- Genetics, Flower Development, Agricultural Biotechnology, Genetic Diversity

We investigated the effects of fire on population growth rate and invasive spread of the perennial tussock grass Molinia caerulea. During the last decades, this species has invaded heathland communities in Western Europe, replacing typical heathland species such as Calluna vulgaris and Erica tetralix. M. caerulea is considered a major threat to heathland conservation. In 1996, a large and unintended fire destroyed almost one-third of the Kalmthoutse Heide, a large heathland area in northern Belgium. To study the impact of this fire on the population dynamics and invasive spread of M. caerulea, permanent monitoring plots were established both in burned and unburned heathland. The fate of each M. caerulea individual in these plots was monitored over four years (1997)(1998)(1999)(2000). Patterns of seed dispersal were inferred from a seed germination experiment using soil cores sampled one month after seed rain at different distances from seed-producing plants. Based on these measures, we calculated projected rates of spread for M. caerulea in burned and unburned heathland. Elasticity and sensitivity analyses were used to determine vital rates that contributed most to population growth rate, and invasion speed. Invasion speed was, on average, three times larger in burned compared to unburned plots. Dispersal distances on the other hand, were not significantly different between burned and unburned plots indicating that differences in invasive spread were mainly due to differences in demography. Elasticities for fecundity and growth of seedlings and juveniles were higher for burned than for unburned plots, whereas elasticities for survival were higher in unburned plots. Finally, a life table response experiment (LTRE) analysis revealed that the effect of fire was mainly contributed by increases in sexual reproduction (seed production and germination) and growth of seedlings and juveniles. Our results clearly showed increased invasive spread of M. caerulea after fire, and call for active management guidelines to prevent further encroachment of the species and to reduce the probability of large, accidental fires in the future. Mowing of resprouted plants before flowering is the obvious management tactic to halt massive invasive spread of the species after fire.

- by Rein Brys
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- Western Europe, Seed Dispersal, Fire, Seed germination

Using microsatellites we show evolution of asexual reproduction in the bladder wrack promoting population persistence in the brackish water Baltic Sea (< 6 psu). Here a dwarf morph of Fucus vesiculosus is dominated by a single clone but clonal reproduction is also present in the common form of the species. We describe a possible mechanism for vegetative reproduction of attached algae, and conclude that clonality plays an important role in persistence and dispersal of these marginal populations, in which sexual reproduction is impaired by low salinity.

- by Lena Bergström and +1
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- Population Genetics, Brackish Water, Population Dynamics, Molecular Ecology

The effects of jasmonic acid (JA), I-aminocyclopropane carboxylic acid (ACC) and 2-cholorethyl phosphonic acid (ethephon) on pollen germination were investigated in strawberry cv. Tufts. ACC and ethephon stimulated pollen germination while JA was inhibitory. Pollen germination was decreased by 0.5 mM JA from 42.5 to 5.8% compared with the control after 4 h of incubation. On the other hand, ACC and ethephon (0.5 mM) increased the pollen germination percentage to 55.6 and 60.7%, respectively. In addition, both ethephon and ACC relieved the inhibition of pollen germination by JA.

- by Kenan Yıldız
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- Plant Biology, Strawberry, POLLEN GERMINATION, Plant Growth Regulation

An electrophoretic survey of allozyme variation revealed substantial genetic differentiation within the eastern Australian population of Actinia tenebrosa. This differentiation appears to reflect the effects of both asexual reproduction and limited gene flow among local populations separated by up to 1050 km. Variation was assessed within groups of 27 to 55 adults sampled between September 1985 and December 1988 collected from small areas of shore within each of 24 local populations. All individuals were collected from stable rock platforms, with the exception of Boulder Bay, where some sea anemones were removed from small mobile boulders. High levels of variability were detected for each of seven enzyme-encoding loci. The patterns of genotypic variation detected imply that local populations are maintained by predominantly asexually generated recruitment. Levels of multi-locus genotypic diversity within samples were consistently less than 50 % of the level expected for sexual reproduction with free recombination. This was reflected by the detection of relatively low numbers of multi-locus genotypes and significant departures from expectations for single-locus Hardy-Weinberg equilibria within 17 of the 24 local populations. Standardised genetic variances (Fsr), calculated from the genotypes of all individual adults were typically much greater than those expected for marine organisms with widely dispersed larvae. The former values were reduced, but were still extremely large when "clonal" genotype frequencies were substituted into the calculation. These data imply that although widely dispersed larvae may be an important source of initial colonists, levels of gene flow among established local populations are low. Furthermore, cluster analysis revealed a clear subdivision of the population into northern and southern groups. However, this subdivision was largely explained by strong clinal variation at a GPIencoding locus. For this locus, allele frequencies ranged from fixation of the A allele in samples from the 12 most northern sites to near fixation of the alternative B allele * Contribution No. 78 from the Ecology and Genetics Group of the University of Wollongong in southern samples. Subdivision of the eastern Australian population is consistent with the predicted offshore movement of the Eastern Australian Current close to the border between Victoria and New South Wales. However, the split into northern and southern regions, as evidenced by the variation for Gpi, could reflect patterns of gene flow and/or other factors such as natural selection or the recent patterns of colonisation.

- by David Ayre
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- Genetics, Marine Biology, Gene Flow, Natural Selection

Although the floral traits of Parkia conform to the bat-pollination syndrome, many visitors other than bats have been observed at their flowers. Some chiropterophilous plants are also pollinated by other animals; the syndrome is therefore best regarded as a hypothesis for which field observations and pollination experiments are required. The present study aimed, for the first time, to determine the breeding system of the economically important canopy trees, Parkia speciosa and P. timoriana, and to identify their pollinators. Pollination experiments carried out in Trang and Songkhla Provinces, in 28 trees of P. speciosa and four P. timoriana indicated that they are self incompatible. Open pollination resulted in the highest fruit set (average 60-67% of inflorescences per tree) although this was not significantly different from hand-crossed pollination (48-60%). Insect pollination resulted in fruit set in only 12% of P. speciosa inflorescences. Fruit bats, mainly Eonycteris spelaea, visit flowering plants continuously from dusk till after midnight. Nocturnal and diurnal insects (moths and stingless bees respectively) visit capitula, mostly at the nectar zone. Nectarivorous bats are the most effective pollinator for P. speciosa and P. timoriana. The fact that populations of E. spelaea appear to be declining throughout their distribution is therefore a matter of increasing concern.

- by SARA BUMRUNGSRI
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- Tropical Ecology, Ecology, Sexual reproduction

The intertidal sea anemone Oulactis muscosa (Drayton) is dioecious and most individuals are sexually mature throughout the year. Biochemical genetic evidence was used to determine the genetic structure of populations and to infer the relative contributions of sexual and asexual reproduction to recruitment. Data were collected for six enzyme-encoding loci from local populations spread along 735 km of the south east coast of Australia. The genetic structure of each of the nine local populations studied was consistent with recruitment by sexually produced individuals. In almost all cases, the observed single-locus genotypic frequencies closely matched those expected for Hardy-Weinberg equilibria, however, consistent deficits of heterozygotes were detected for all loci. No apparent subdivision of the population was detected within the sampling area. Low levels of genetic differentiation were found between local populations and standardised variance (Fsr) values were similar to those for other species with widespread planktonic dispersal of larvae.

- by David Ayre
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- Genetics, Marine Biology, Reproduction, Biological Sciences

As the sea anemones, Entacmaea quadricolor and Heteractis crispa, provide essential habitat for obligate symbiotic anemonefish, knowledge of their reproductive biology is crucial to their effective management and conservation. This paper provides the first detailed information on the spawning times, behaviour and mode of gamete release for these host anemone species. Anemones were collected from subtropical reefs in the Solitary Islands Marine Park, eastern Australia, and monitored in outdoor flow-through seawater tanks from 2003 to 2005. Sexually reproductive anemones were either male or female, releasing their gametes into the water column for external fertilisation and development. Spawning of both sexes was predominately synchronous and was restricted to a few nights each year during the austral summer and autumn. Males generally began to release gametes prior to females, suggesting that sperm or some associated product may trigger the females to spawn. Sperm were commonly released in milky white streams or clouds, whereas eggs were released singly or in large masses. Reproductive seasonality and synchrony of gamete release suggests that spawning in both species is coordinated by similar responses of individuals to a range of environmental factors such as seawater temperature, photoperiod and lunar cycles. Incorporating knowledge of the sexual reproductive biology of host sea anemones into management and conservation programs could help ensure the viability of their populations and their resident anemonefish.

- by Anna Scott
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- Zoology, Life Sciences, Reproductive Biology, Seasonality

In this historical text, Wendy Kline considers how key women's health issues (including contraception, abortion, and childbirth) were approached during the second wave of the feminist revolution. The first chapter, 'Transforming Knowledge', deals with the ways in which second wave feminism came into health care in the 1970s, focusing on the seminal text Our Bodies, Ourselves and looking at how the original book came into being and developments in subsequent editions. Kline

- by Abigail Locke
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- Psychology, Cognitive Science, Health Psychology, Curriculum and Pedagogy

Parma violets are reputed for their double, fragrant flowers and have been cultivated for centuries in Europe. However, due to a rather atypical morphology their taxonomic affinity has not been clarified. Authors have proposed an origin from three possible species, Viola alba, V. odorata, or V. suavis, or a hybrid origin. Using both ITS sequence variation and allozyme variation in 14 putative loci, we showed that the Parma violet cultivars have their origin within Viola alba and that they are best included in the Mediterranean subsp. dehnhardtii. There is no trace of interspecific hybridization. However, the cultivars appear to have a single origin in a wide hybrid within V. alba, involving parental plants from the eastern and western Mediterranean region; historical literature sources seem to indicate Turkey and Italy, respectively. The Parma violet cultivars possess high levels of allozyme heterozygosity and to some extent also within-individual ITS sequence variation. Losses of heterozygosity and within-individual ITS sequence variation in some of the cultivars indicate subsequent rare events of sexual reproduction, presumably through cleistogamous seed set. We unambiguously identify the closest wild relative of this group of cultivars, allowing growers to develop new selection procedures, and show a peculiar molecular process associated with human selection.

- by Roxana Yockteng
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- Botany, Evolutionary Biology, Plant Biology, Ecology

The diplobiontic-haplodiplontic life cycle with alternating isomorphic generations in Stigeoclonium tenue (C. Agardh) Kütz. is described for the first time. Sporophytes (2n = 10) arise from tetraflagellate zoospores that are produced by meiosis. Sporic meiosis might be inferred from the cruciform divisions formed during zoosporogenesis and is confirmed through observations of prophase I substages. Zoospores do not germinate directly but produce a haploid cyst that germinates to give rise to a gametophyte (n = 5). Gametophytes produce biflagellate isogametes, which fuse to produce zygotes that germinate by mitosis into the sporophytic stage. Gametophytes and sporophytes reproduce asexually both via mitotic tetraflagellate zoospores and by thallus fragmentation. Results from this study indicate that both the cosmopolitan distribution and dominance of S. tenue in many periphytic communities might be due to its multiple reproductive strategies.

- by Patricia Leonardi
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- Phycology, Plant Biology, Life Cycle, Karyology

Molecular sequencing has helped resolve the phylogenetic relationships amongst the diverse groups of algal, fungal-like and protist organisms that constitute the Chromalveolate "superkingdom" clade. It is thought that the whole clade evolved from a photosynthetic ancestor and that there have been at least three independent plastid losses during their evolutionary history. The fungal-like oomycetes and hyphochytrids, together with the marine flagellates Pirsonia and Developayella, form part of the clade defined by Cavalier-Smith and Chao (2006) as the phylum "Pseudofungi", which is a sister to the photosynthetic chromistan algae (phylum Ochrophyta). Within the oomycetes, a number of predominantly marine holocarpic genera appear to diverge before the main "saprolegnian" and "peronosporalean" lines, into which all oomycetes had been traditionally placed. It is now clear that oomycetes have their evolutionary roots in the sea. The earliest diverging oomycete genera so far documented, Eurychasma and Haptoglossa, are both obligate parasites that show a high degree of complexity and sophistication in their host parasite interactions and infection structures. Key morpho-logical and cytological features of the oomycetes will be reviewed in the context of our revised understanding of their likely phylogeny. Recent genomic studies have revealed a number of intriguing similarities in hostpathogen interactions between the oomycetes with their distant apicocomplexan cousins. Therefore, the earlier view that oomycetes evolved from the largely saprotrophic "saprolegnian line" is not supported and current evidence shows these organisms evolved from simple holocarpic marine parasites. Both the hyphal-like pattern of growth and the acquisition of oogamous sexual reproduction probably developed largely after the migration of these organisms from the sea to land.

- by Gordon Beakes
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- Electron Microscopy, Molecular Evolution, Plant Biology, Mitochondria
- by Bente Jessen Graae and +3
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- Climate Change, Forest Ecology And Management, Forest Ecology, Seed production

Pollination effectiveness was evaluated for pollen (pollinia) from two Dendrobium hybrids, ‘Sena Red’ and ‘Mini WRL’, submitted to cryopreservation using a vitrification protocol. Parameters evaluated included pollinia exposure to a previtrification solution (PVS2) under ice (0 °C) or room (27 ± 2 °C) temperatures from 1 to 4 hours before cryopreservation (LN). On removal from cryopreservation, pollinia were used to pollinate flowers of the same hybrids to verify viability and germination. All pollinia showed high percentages of germination (greater than 80%) after crosses were performed, except for pollinia from Dendrobium ‘Sena Red’ submitted to 3 hours of precooling (0 °C) in PVS2 followed by LN (60%) and for pollinia submitted to PVS2 for 3 hours at room temperature with no precooling (70%). Capsules were formed for both hybrids and seeds were successfully produced. The seed viability test revealed high viability (90% to 95%) for all treatments for both hybrids. Seeds observed u...

- by Wagner Vendrame
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- Biology, Pollination, Cryopreservation, SHELF LIFE

Although tardigrades can reproduce only through gametes they have exploited several modes of reproduction, which may be determined by their environment. Marine species (mainly heterotardigrades) are gonochoristic; hermaphroditism is only cited once, and parthenogenesis is unknown. In many cases females mature one egg at a time throughout adult life, whereas males are semelparous. Gonochorism is still present in limno-terrestrial species, while sporadic hermaphroditism occurs in several eutardigrade families. Thelytoky is the most common mode of reproduction in non-marine Tardigrada. Females are iteroparous, laying groups of eggs (free or in the exuvium), while males are semelparous (in a limnic species) or iteroparous with a continuous or cyclical maturation of the spermatozoa (in species from moss and leaf litter). Self-fertilisation appears to characterise hermaphroditic species, found in freshwater, mosses, leaf litter and soil. Egg maturation in these species is similar to that of the gonochoristic species, while spermatozoa mature in appreciable numbers before the oocytes, subsequently maturing continuously but in small numbers over the life of the animal. Parthenogenesis in limno-terrestrial tardigrades always appears continuous. In many species only females occur, but morpho-species populations may be found with both bisexual amphimictic (diploid) and unisexual thelytokous (often but not always polyploid) cytotypes. We can hypothesise that with the evolution of cryptobiosis and passive dispersal unstable and isolated habitats may favour parthenogenesis and self-fertilisation, as both reproductive modes allow colonisation of a new territory by a single individual. Parthenogenesis and hermaphroditism do not occur in the same species, and we can surmise that self-fertilisation will only evolve where parthenogenesis has never occurred.

- by R. Bertolani
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- Zoology, Leaf Litter, Sexual reproduction

Nets in traditional Porphyra mariculture are seeded with conchospores derived from the conchocelis phase, and spend a nursery period in culture tanks or calm coastal waters until they reach several centimeters in length. Some species of Porphyra can regenerate the foliose phase directly through asexual reproduction, which suggests that the time, infrastructure, and costs associated with conchocelis culture might be

- by Charles Yarish and +1
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- Zoology, Aquaculture, Reproductive Biology, Seasonality

BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and... more

- by Jay Stachowicz
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- Plant Ecology, Community Ecology, Coevolution, Biology
- by imogen tyler
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- New Media, Feminist Media Studies, Social Class, Regional Variation

From simple beginnings, the life cycles of parasitic helminths have evolved into complex sequences of improbable events. Both adaptive scenarios and evolutionary contingencies are often invoked to explain the complexity of their life cycles . For example, if a new type of predator evolves, the parasite of the prey might add a developmental stage to their life cycle inside the predator. Alternatively, transmission from prey host to predator host could serve to concentrate conspecific parasites and facilitate cross-fertilization . Whatever the origin of complex life cycles, they have imposed new selective pressures on parasites by being so difficult to complete.

- by Thomas Cribb
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- Reproduction, Biological Sciences, Phylogeny, Trematoda
- by Jean-christophe Simon and +1
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- Genetics, Sexuality, Ecology, Evolution

In 1858, two naturalists, Charles Darwin and Alfred Russel Wallace, independently proposed natural selection as the basic mechanism responsible for the origin of new phenotypic variants and, ultimately, new species. A large body of evidence for this hypothesis was published in Darwin's Origin of Species one year later, the appearance of which provoked other leading scientists like August Weismann to adopt and amplify Darwin's perspective. Weismann's neo-Darwinian theory of evolution was further elaborated, most notably in a series of books by Theodosius Dobzhansky, Ernst Mayr, Julian Huxley and others. In this article we first summarize the history of life on Earth and provide recent evidence demonstrating that Darwin's dilemma (the apparent missing Precambrian record of life) has been resolved. Next, the historical development and structure of the "modern synthesis" is described within the context of the following topics: paleobiology and rates of evolution, mass extinctions and species selection, macroevolution and punctuated equilibrium, sexual reproduction and recombination, sexual selection and altruism, endosymbiosis and eukaryotic cell evolution, evolutionary developmental biology, phenotypic plasticity, epigenetic inheritance and molecular evolution, experimental bacterial evolution, and computer simulations (in silico evolution of digital organisms). In addition, we discuss the expansion of the modern synthesis, embracing all branches of scientific disciplines. It is concluded that the basic tenets of the synthetic theory have survived, but in modified form. These sub-theories require continued elaboration, particularly in light of molecular biology, to answer openended questions concerning the mechanisms of evolution in all five kingdoms of life. Dedicated to Prof. Dr. Dr. hc mult. Ernst Mayr on the occasion of his 100th birthday U. Kutschera ( ) )

As the oldest extant lineages of land plants, bryophytes provide a living laboratory in which to evaluate morphological adaptations associated with early land existence. In this paper we examine reproductive and structural innovations in the gametophyte and sporophyte generations of hornworts, liverworts, mosses and basal pteridophytes. Reproductive features relating to spermatogenesis and the architecture of motile male gametes are overviewed and evaluated from an evolutionary perspective. Phylogenetic analyses of a data set derived from spermatogenesis and one derived from comprehensive morphogenetic data are compared with a molecular analysis of nuclear and mitochondrial small subunit rDNA sequences.

- by R. Joel Duff
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- Biological Sciences, Phylogenetic analysis, Indexation, Vegetation Structure

Advances in Biochemical Engineering/Biotechnology reviews actual trends in modern biotechnology. Its aim is to cover all aspects of this interdisciplinary technology where knowledge, methods and expertise are required for chemistry, biochemistry, micro-biology, genetics, chemical engineering and computer science. Special volumes are dedicated to selected topics which focus on new biotechnological products and new processes for their synthesis and purification. They give the state-of-the-art of a topic in a comprehensive way thus being a valuable source for the next 3-5 years.

- by Nils Arrigo
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- Genetics, Gene Flow, Ecology, Risk assessment

Garlic (Allium sativum L.) genotypes differ considerably in scape length, flowering ability, and seed production. In bolting clones reproductive processes are facilitated by a combination of specific temperature and photoperiod regimes. However, it is yet unclear whether the phase-specific photoperiod effect on florogenesis is universal for all garlic genotypes. We investigated the effect of ambient day length interruption by 10 or 30 days of long photoperiod in ten garlic accessions belonging to four bio-morphological groups. It was evident that garlic genotypes vary significantly in response to long photoperiod, and that in some clones the treatment enhances florogenesis, flower stalk elongation and bulbing. The competition for resources by the simultaneously developing bulb and inflorescence sinks differentially determines the fate of stalk elongation and flower development in the investigated genotypes. It is concluded that florogenesis in garlic can be promoted by exposure to proper environmental stimuli, during pre-planting storage and sprouting to the later growth stages. The genetic variability acquired from sexual reproduction and vegetatively preserved collections can serve in genetic and physiological studies as well as in breeding programs.

- by Deepu Mathew
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- Botany, Genetics, Physiology, Plant Ecology

The great taxonomic diversity of the Orchidaceae is often attributed to adaptive radiation for specific pollinators driven by selection for outcrossing. However, when one looks beyond the product to the process, the evidence for selection is less than overwhelming. We explore this problem by discussing relevant aspects of orchid biology and asking which aspects of reproduction explain the intricate pollination mechanisms and diversification of this family. We reaffirm that orchids are primarily pollination limited, the severity of which is affected by resource constraints. Fruit set is higher in temperate than in tropical species, and in species which offer pollinator rewards than those that do not. Reproductive success is skewed towards few individuals in a population and effective population sizes are often small. Population structure, reproductive success and gene flow among populations suggest that in many situations genetic drift may be as important as selection in fostering genetic and morphological variation in this family. Although there is some evidence for a gradualist model of evolutionary change, we believe that the great diversity in this family is largely a consequence of sequential and rapid interplay between drift and natural selection.

- by Raymond L Tremblay
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- Speciation, Genetic Drift, Gene Flow, Natural Selection

The rice (Oryza sativa) genome contains 18 copies of genes of the ARGONAUTE (AGO) family. Although AGO members play important roles in RNA-mediated silencing during plant development, a family member that is specifically involved in sexual reproduction has not been identified in plants. We identified the rice AGO gene MEIOSIS ARRESTED AT LEPTOTENE1 (MEL1) from the analysis of seed-sterile mutants. In the mel1 mutant, chromosome condensation was arrested at early meiotic stages and irregularly sized, multinucleated, and vacuolated pollen mother cells (PMCs) frequently appeared in developing anthers. In addition, histone H3 lysine-9 dimethylation of pericentromeres was rarely reduced and modification of the nucleolarorganizing region was altered in mel1 mutant PMCs. The mutation also affected female germ cell development. These results indicate that the germ cell-specific rice MEL1 gene regulates the cell division of premeiotic germ cells, the proper modification of meiotic chromosomes, and the faithful progression of meiosis, probably via small RNA-mediated gene silencing, but not the initiation and establishment of germ cells themselves.

- by Nori Kurata
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- Genetics, Gene regulation, Plant Biology, Gene Silencing

- by Jess Zimmerman
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- Speciation, Genetic Drift, Gene Flow, Natural Selection
- by William Johnson
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- Genetics, Marine Biology, Biological Sciences, Male Reproduction Health

Animals have evolved a fascinating array of mechanisms for conducting sexual reproduction. These include producing the sex-specific gametes, as well as mechanisms for attracting a mate, courting a mate, and getting the gametes together. These processes require that males and females take on dramatically different forms (sexual dimorphism). Here, we will explore the problem of how sex is determined in Drosophila, and pay particular attention to how information about sexual identity is used to instruct males and females to develop differently. Along the way, we will highlight new work that challenges some of the traditional views about sex determination. In Drosophila, it is commonly thought that every cell decides its own sex based on its sex chromosome constitution (XX vs. XY). However, we now know that many cell types undergo nonautonomous sex determination, where they are told what sex to be through signals from surrounding cells, independent of their own chromosomal content. Further, it now appears that not all cells even “know” their sex, since key members of the sex determination pathway are not expressed in all cells. Thus, our understanding of how sex is determined, and how sexual identity is used to create sexual dimorphism, has changed considerably.

- by Cale Whitworth
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- Sexual dimorphism, Drosophila, Sex Determination, Sex Differentiation

During the past two decades we have gained much insight into the factors that regulate the productivity of seagrass dominated ecosystems, especially those at low latitudes. Here, we review and reassess the importance of plant-herbivore interactions in seagrass meadows, focusing on recent studies that have examined: 1) grazing on live seagrass leaves; 2) consumption of epiphytic algae growing on seagrass leaves; and 3) consumption of planktonic algae from the waters surrounding seagrass meadows. The major conclusion is that, in contrast to what has been reported in much of the literature on food webs in seagrass meadows, a diverse grazing pathway continues to represent an important conduit for the transfer of energy from the primary producers to higher order consumers. This remains true, although in many areas consumption of seagrasses is reduced in an historical context, owing to the overharvesting of many large species of herbivorous waterfowl, turtles and mammals.

- by John F Valentine
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- Food webs, Biological Sciences, Higher Order Thinking, Environmental Sciences

The olive tree (Olea europaea L.), like many other woody plants, has a long juvenile period in which the plant is not able to produce flowers. Knowledge of the moment when the plant is capable of flowering is important for breeding programs and also for determining the physiological basis for sexual reproductive behavior, but currently the only indicator of that moment is the actual flowering. In many species, the juvenile-to-adult phase shift includes changes in leaf structure known as heteroblasty, that is, varied form of successive leaves on the same plant. Some differences have been observed between juvenile and adult olive leaves, particularly in size and form, but to our knowledge, no complete systematic study has been carried out. In this research, we measured size, morphology and anatomy for juvenile and adult leaves of olive plants grown from seeds. Differences were found in most of the parameters studied, including leaf size, form, mesophyll thickness, layers of palisade parenchyma and quantity of peltate trichomes, which were generally significant but overlapping between the two leaf types. The most consistent and striking difference was the presence of an organized layer of subepidermal cells only in the abaxial mesophyll of adult leaves. This characteristic could be a simple and effective criterion of phase change in the olive tree.

- by Raul de la Rosa
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- Plant Biology, Morphology, Plant Morphology, Plant Anatomy

The floral biology and pollination ecology of durian, Durio zibethinus, were determined in eight semi-wild trees in mixed-fruit orchards in southern Thailand during April-May 2003 and 2005. Flowers open fully at 16h00-16h30 and most androecia drop around 01h00. Anthers dehisce at 19h30-20h00 when the stigmata are already receptive. In a series of pollination experiments, fruit was set in all treatments within 10 d. The greatest pollination success occurred after hand-crossed (76.6%), open (54.4%) and emasculation pollination (53.3%). Consistently, hand-crossed (12.2%), emasculation (8.7%) and open pollination (5.1%) yielded a substantial fruit set 2 mo after the pollination experiments. Very low pollination success in facilitated autogamy suggests that most durian trees are highly self incompatible. No mature fruit was found after insect pollination and automatic autogamy. Fruit bats, especially Eonycteris spelaea, are the major pollinators of this durian although the giant honey bee (Apis dorsata) was the most frequent visitor to the flowers. Bats visited durian flowers at the rate of 26.1 (SD = 20.7) visits per inflorescence per night. Since this semi-wild durian depends on fruit bats as its pollinator, protecting fruit bat populations and their roosts is vital for the production of the durian fruit crop.

- by SARA BUMRUNGSRI
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- Tropical Ecology, Ecology, Tropical, Sexual reproduction

The photoperiodic response of 56 parthenogenetic lineages of Aphis gossypii Glover was examined by rearing the aphids for three generations under short day conditions (SD, L10:D14) and 17 °C. The lineages were derived from aphid samples collected in cen- tral and northern Greece from various crops and uncultivated plants of the families Asteraceae (chrysanthemum Chrysanthemum sp., smooth sow-thistle Sonchus oleraceus

- by John Tsitsipis
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- Zoology, Life Cycle, Watermelon, Citrullus lanatus

Single-locus microsatellite variation correlated perfectly with chromosome number in Sitobion miscanthi aphids. The microsatellites were highly heterozygous, with up to 10 alleles per locus in this species. Despite this considerable allelic variation, only seven different S. miscanthi genotypes were discovered in 555 individuals collected from a wide range of locations, hosts and sampling periods. Relatedness between genotypes suggests only two successful colonizations of Australia. There was no evidence for genetic recombination in 555 S. miscanthi so the occurrence of recent sexual reproduction must be near zero. Thus diversification is by mutation and chromosomal rearrangement alone. Since the aphids showed no sexual recombination, microsatellites can mutate without meiosis. Five of seven microsatellite differences were a single repeat unit, and one larger jump is likely. The minimum numbers of changes between karyotypes corresponded roughly one-to-one with microsatellite allele changes, which suggests very rapid chromosomal evolution. A chromosomal fission occurred in a cultured line, and a previously unknown chromosomal race was detected. All 121 diverse S. nearfragariaewere heterozygous but revealed only one genotype. This species too must have a low rate of sexual reproduction and few colonizations of Australia.

- by Andrea Taylor and +1
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- Genetics, Chromosome Evolution, Sexual reproduction, Aphid

Cork oak (Quercus suber L.) is a monoecious wind-pollinated species with a protandrous system to ensure cross-pollination. To the best of our knowledge, this report provides the first insight into the sexual reproduction cycle in this species. The cork oak flowering season extends from April until the end of May. Our results show that, at anthesis, the pistillate flower is not completely formed and ovules are just starting to develop. Pollen reaching the dry stigmatic surface adheres to the receptive cells, germinates and penetrates the epidermis in aproximately 24 h, and grows through the intercellular spaces of a solid transmitting tissue. In cross-pollination, a sequential arrest of pollen tubes was observed along the style, providing preliminary evidence for a pollen tube competition mechanism. As a consequence, few pollen tubes reach the basal portion of the style. Furthermore, pollen tube growth is a discontinuous process since tubes are arrested in the basal portion of the style about 10–12 days after pollination. While tubes are latent, the ovarian loculus starts to develop from an emerging mass of sporogeneous cells which later will differentiate into the placenta and ovules. One and a half months after pollination ovules complete their differentiation, tubes resume growth and fertilisation occurs. Ovular abortion is frequent at this stage, and only one ovule will successfully mature during autumn into a monospermic seed.

- by Leonor Boavida
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- Kinetics, Plant Biology, Seed production, Sexual Plant Reproduction

Cassava (Manihot esculenta Crantz) is a clonally propagated crop that was introduced into the South Pacific archipelago of Vanuatu in the 1850s. Based on a survey conducted in 10 different villages throughout the archipelago, we present here a study of its diversity. Farmers' knowledge about cultivation cycle and sexual reproduction of cassava was recorded during group interviews in each village. Using a set of 11 SSR markers, we genotyped the 104 landraces collected and 60 supplementary accessions from a within-landrace study (12 landraces Â 5 plants). Out of the 104 landraces collected, we discovered 77 different multilocus genotypes and the within-landrace study identified several polyclonal landraces. Our data suggest a number of hypotheses about the dynamics of diversity of cassava in Vanuatu.

- by Manu Vincent
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- Genetics, Reproduction, Molecular Evolution, Breeding

Asexual organisms that naturally coexist with sexual relatives may hold the key to understanding the maintenance of sex and recombination, a long-standing problem in evolutionary biology. This situation applies to the peach-potato aphid, Myzus persicae , in southeastern Australia where cyclical parthenogens form mixed populations with obligate parthenogens. We collected M. persicae from several areas across Victoria, genotyped them at seven microsatellite loci and experimentally determined their reproductive mode. The geographic distribution of reproductive modes was correlated with two environmental variables that differentially affect obligate and cyclical parthenogens; obligate parthenogens were less frequent in areas with cold winters because they cannot produce frost-resistant eggs while cyclical parthenogens were limited by the availability of their primary host, peach, on which sexual reproduction takes place. Clonal diversity increased with the proportion of cyclical parthenogens in a sample because they tended to have unique microsatellite genotypes, whereas many obligate parthenogens were copies of the same genotype. Two obligately asexual genotypes stood out as being very abundant and widespread, one constituting 24% and the other 17.4% of the entire collection. Both of these highly successful genotypes were present in the majority of all collection sites. Genetic population structure was weak, albeit significant, with a multilocus F ST of only 0.021 when samples were reduced to only one representative of each genotype. Interestingly, obligate parthenogens were, on average, more heterozygous and exhibited larger allele size differences between the two alleles at individual loci than cyclical parthenogens. This striking pattern could result from hybridization, for which we have no evidence, or may reflect the previously proposed model of biased mutational divergence of microsatellite alleles within asexual aphid lineages.

- by Melanie Lancaster and +1
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- Evolutionary Biology, Geography, Population Genetics, Australia

The reproductive ecology of the hermaphroditic broadcast spawning scleractinian reef coral Platygyra daedalea was studied on lagoonal reefs in Kenya. While single annual gametogenic cycles occurred in 84% of colonies, biannual gametogenic cycles were recorded in 16% of colonies and these patterns occurred in two morphotypes. In colonies with a single annual cycle, oogenesis occurred for 6-7 months from September to March and spermatogenesis for 5 months from November to March. In biannually spawning colonies, oogenic cycles overlapped for at least 2 months prior to gamete release. The major spawning period occurred in February and March, with minor spawning also occurring in August-October in biannually spawning colonies. Reproductive effort was lower during the minor winter compared to the major summer spawning, with fewer colonies reproducing (12.5-19.2%), not all mesenteries producing oocytes (32.5%) and less than half of the mesenteries with mature oocytes had associated spermaries (48.1%).

- by Sangeeta Mangubhai
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- Earth Sciences, Coral Reefs, Kenya, Reproductive Ecology
- by Jennifer Keiser and +1
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- Microbiology, Clinical Trial, Medical Microbiology, Schistosomiasis

Over the last decade, our understanding of the environmental controls on Pseudo-nitzschia blooms and domoic acid (DA) production has matured. Pseudo-nitzschia have been found along most of the world's coastlines, while the impacts of its toxin, DA, are most persistent and detrimental in upwelling systems. However, Pseudo-nitzschia and DA have recently been detected in the open ocean's high-nitrate, lowchlorophyll regions, in addition to fjords, gulfs and bays, showing their presence in diverse environments. The toxin has been measured in zooplankton, shellfish, crustaceans, echinoderms, worms, marine mammals and birds, as well as in sediments, demonstrating its stable transfer through the marine food web and abiotically to the benthos. The linkage of DA production to nitrogenous nutrient physiology, trace metal acquisition, and even salinity, suggests that the control of toxin production is complex and likely influenced by a suite of environmental factors that may be unique to a particular region. Advances in our knowledge of Pseudo-nitzschia sexual reproduction, also in field populations, illustrate its importance in bloom dynamics and toxicity. The combination of careful taxonomy and powerful new molecular methods now allow for the complete characterization of Pseudo-nitzschia populations and how they respond to environmental changes. Here we summarize research that represents our increased knowledge over the last decade of Pseudo-nitzschia and its production of DA, including changes in worldwide range, phylogeny, physiology, ecology, monitoring and public health impacts.

- by Vera Trainer
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- Trace Metals, Public Health, Ecosystem health, Diatoms

The eVect of temperature on the development and hatching of resting eggs of the Ponto-Caspian Cercopagis pengoi was studied experimentally in the Gulf of Finland, Baltic Sea. Morphological changes were monitored as the development of the resting eggs proceeded. Sexual reproduction of the C. pengoi population in the Gulf of Finland was evaluated by combining the data from hatching experiments and resting egg abundances in the sediment. Development time of resting eggs was dependent on temperature: increase in the temperature shortened the time needed until hatching. Hatching success was also dependent on incubation temperature. Almost sixfold increase in hatching success was detected when temperature increased two degrees above the storage temperature. Average resting egg abundances varied between 0.16 and 0.49 eggs cm ¡3 in the 0-6 cm sediment layer.

- by S. Sopanen
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- Marine Biology, Biological Sciences, Environmental Sciences, Gulf of Finland

Although considerable work has been done investigating the factors that underlie species trait assemblages in emblematic groups such as plants and vertebrates, more remains to be done in belowground invertebrate species. For this group, in particular, relationships between species traits and habitat preferences are still a matter of debate. To eludicate upon the relationships, springtails were sampled in a heterogeneous landscape centered on the Sénart forest, near Paris (northern France), which represented the largest possible array of five environmental gradients (humus forms, vegetation, moisture, vertical strata, and seasons) over which Collembola are known to be distributed. The distance between samples varied from a few cm to several km. Canonical correspondence analysis using species (128) as observations and species trait attributes (30) and habitat indicators (82) as dependent and independent variables, respectively, allowed us to discern whether species habitats and species trait assemblages were related and which trends could be found in trait/environment relationships. It was concluded that, within the studied area, species habitats were significantly associated with species trait assemblages. The main gradient explaining the distribution of species traits combined the vertical distribution of habitats (from the mineral soil to plant aerial parts), and the openness of the environment, suggesting that a complex of many ecological factors is at play. For the ecological traits of Collembola, this gradient corresponded to an increasing contribution of sensory and locomotory organs, bright color patterns, size and sexual reproduction, all attributes associated with aboveground life under herbaceous cover. Another important, although secondary contrast concerned traits associated with habitats far from soil but that were concealed (corticolous vs. all other habitats). Soil acidity and water did not contribute significantly to trait distribution, at least within the limits of our database.

- by Sandrine Salmon
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- Plant Biology, Seasonality, Collembola, Habitats

Sexual reproduction is documented for the first time in field populations of the pennate diatoms Pseudo-nitzschia australis Freng. and P. pungens (Grunow ex Cleve) Hasle (var. cingulata Villac and hybrids between var. cingulata and var. pungens). A bloom dominated by these species began on June 26, 2006, along Kalaloch Beach, Washington, USA, coincident with a drop in the Si(OH) 4 :NO 3 ratio to below two. Multimodal size distributions were detected for both species, and synchronous auxosporulation occurred within the smallest size class during a 3-week window. Auxospores and initial cells created a new class of large cells, and cells in the intermediate size classes increased in abundance during auxosporulation. Mating cells of both species were attached to colonies of surf-zone diatoms. Paired gametangia, gametes, zygotes, auxospores, and large initial cells were found. Auxosporulation began first for P. pungens (June 30), apparently once a critical, high cell concentration was reached, followed by P. australis (July 5), when the total Pseudonitzschia cell concentration reached 929,000 cells AE L )1 . Low frequencies of auxosporulation occurred throughout the bloom but increased 4-fold for P. australis and 3-fold for P. pungens when macronutrients were reduced to low levels on July 11. A 2-year life cycle was estimated for P. australis and 3 years for P. pungens, both with annual auxosporulation. Domoic acid (DA) in razor clams reached a maximum of 38 lg DA AE g )1 on July 18. A significant relationship existed between the percent of cells within the new size range and DA concentrations in razor clams on the same beach.

- by Stephen S. Bates
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- Phycology, Plant Biology, Sexual reproduction

The water flea Daphnia magna (Crustacea, Cladocera) is a cyclical parthenogen, which can reproduce both by parthenogenesis and by sexual reproduction. With its ease of handling in the laboratory, several testing methods using D. magna exist for regulatory toxicity testing. Recently, several studies revealed that one of the major hormone groups in insects and crustaceans, juvenile hormones, are involved in the shift of reproductive mode from parthenogenesis to sexual reproduction (production of male neonates). Using offspring sex ratio as a new endpoint has made it possible to identify chemicals with juvenile hormonelike effects on crustaceans. The testing method using D. magna, in which offspring sex ratio is incorporated as a new endpoint, is now being proposed to the OECD as an enhanced version of the existing OECD Test Guideline 211: Daphnia magna reproduction test. No other clear-cut endpoint for identifying juvenilehormone disrupting effects has ever been found in crustaceans than the induction of male neonates production in cladocerans. In this regard, it is expected that testing methods using D. magna are suitable for screening and risk assessment of chemicals with juvenile-hormone disrupting effects.

- by Norihisa Tatarazako
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- Ecotoxicology, Reproduction, Risk assessment, Daphnia

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- by Manuel PLANTEGENEST
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- Genetics, Demography, Gene Flow, Population Genetics