Sexual reproduction

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...

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.

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...

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.

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

 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.