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Mature Eggs (mature + egg)
Selected AbstractsDevelopmental stages, larval and post-larval growth of angelwing clam Pholas orientalisAQUACULTURE RESEARCH, Issue 7 2009Beewah Ng Abstract Angelwing clam were induced to spawn by thermal stimulation. Mature eggs measured 50 ,m in diameter. Cell division occurred within 36 min after fertilization. Mobile trochophore larvae were seen after 12 h and larvae developed within 18 h. Reared on a diet of Isochrysis galbana the larvae reached the umbo stage in 6,7 days. On day 10 the foot could be seen and settlement occurred if a suitable substrate was present. The larvae completed metamorphosis into juveniles within 20 days after settling. [source] Cytological studies on induced meiogynogenesis in Japanese flounder Paralichthys olivaceus (Temminck et Schlegel)AQUACULTURE RESEARCH, Issue 6 2009Jilun Hou Abstract The cytological process of induced gynogenetic development and subsequent chromosome duplication by a cold shock treatment was observed in Japanese flounder Paralichthys olivaceus (Temminck et Schlegel). Mature eggs were at the metaphase of the second meiosis when inseminated with ultraviolet (UV)-irradiated sperm of red sea bream Pagrus major. After the beginning of cold shock treatment, the previously visible spindle became invisible, probably due to the side effect caused by cold shock treatment. The chromosomes at the centre of the metaphase plate were condensed. This condition continued during the duration of the cold shock treatment and several minutes after it. The release of the second polar body was blocked and it developed into a female-like pronucleus. Then, it fused with the female pronucleus to generate a diploid zygotic nucleus, and the egg exhibited the first mitosis. Consequently, the haploid female chromosome set of the egg was doubled by the inhibition of the second polar body release. There was a significant delay in developmental time in the gynogenetic eggs when compared with that in the normal eggs. From the time of insemination to early cleavage, the UV-irradiated heterospecific sperm nucleus remained condensed. [source] Formation of the Fertilization Pore during Oogenesis of the Fern Ceratopteris thalictroidesJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2010Jian-Guo Cao The development of the fertilization pore during oogenesis of the fern Ceratopteris thalictroides was followed using transmission electron microscopy. The newly formed egg is appressed closely to the adjacent cells. There are well-developed plasmodesmata between the egg and the ventral canal cell, but none between the egg and the jacket cells of the archegonium. During maturation, a separation cavity is formed around the egg. However, a pore region persistently connects the egg and the ventral canal cell. The extra egg membrane is formed by deposition of sheets of endoplasmic reticulum (ER), but no ER is deposited on the inner surface of the pore region. Thus, a fertilization pore, covered by a layer of plasmalemma, is formed. The ventral canal cell undoubtedly participates the formation of the fertilization pore, probably by absorbing the sheets of ER beneath the pore region. The functional significance of the ventral canal cell in formation of the fertilization pore is discussed. The features of the mature egg include that abundant concentric membranes and osmiophilic vesicles occur in the cytoplasm of the mature egg. The initial, round nucleus of the egg eventually becomes cup-shaped. This investigation gives some new insights about the cells participating oogenesis in ferns. [source] The effect of travel time on oviposition behavior and spatial egg aggregation: experiments with DrosophilaENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2007Kazuo H. Takahashi Abstract A higher degree of spatial egg aggregation is often observed in environments where resource patches are more sparsely distributed. This suggests a higher probability of species coexistence when resource distribution is sparse. However, it is still unclear how the degree of spatial egg aggregation increases. I propose a model to explain this phenomenon, which assumes that (i) egg load (the number of mature eggs in ovaries) increases in the travel period between resource patches and (ii) the retention of eggs in the ovaries is harmful (egg load pressure). With these assumptions, a female would lay accumulated eggs on arrival at a new resource patch, resulting in a higher degree of spatial egg aggregation. Laboratory experiments with three drosophilid species, Drosophila simulans Surtevant, Drosophila auraria Peng, and Drosophila immigrans Sturtevant, support the model. This study provides evidence that host availability affects the spatial egg aggregation via egg load. [source] Effects of sugar feeding on carbohydrate and lipid metabolism in a parasitoid waspPHYSIOLOGICAL ENTOMOLOGY, Issue 1 2000D.A.W.N. M. Olson Summary Lifetime patterns of carbohydrate and lipid metabolism were compared in starved and sucrose-fed adults of the parasitoid Macrocentrus grandii (Goidanich) (Hymenoptera: Braconidae). As expected, sucrose-fed individuals lived longer than did starved individuals. Macrocentrus grandii males and females eclosed with levels of simple storage sugars (presumably primarily trehalose) and glycogen that were below maximum levels recorded from sucrose-fed parasitoids. Both of these nutrients dropped to very low levels in starved individuals within 4 days post-emergence and were maintained at high levels in sucrose-fed individuals throughout their lives. Lipid reserves at emergence represented the highest lipid levels for both sexes in the two diet treatments, with levels declining over the lifetimes of males and females from both diet treatments. Our results therefore suggest that dietary sucrose is used to synthesize trehalose and glycogen, but not lipids in M. grandii. Also, in contrast to the patterns observed for the simple sugars and glycogen, lipid levels in starved individuals did not drop below levels observed in sugar-fed individuals. The average number of mature eggs carried by females at emergence was 33 and increased to approximately 85 in sucrose-fed and 130 in starved females by the age of 5 d in the absence of hosts. The egg maturation rate was therefore higher in starved than in sugar-fed females. Potential explanations for this unexpected result are discussed. [source] | ||||||||||