Cycle Synchrony Research Articles

Geospatial characteristics of measles transmission in China during 2005-2014.

Measles is a highly contagious and severe disease. Despite mass vaccination, it remains a leading cause of death in children in developing regions, killing 114,900 globally in 2014. In 2006, China committed to eliminating measles by 2012; to this end, the country enhanced its mandatory vaccination programs and achieved vaccination rates reported above 95% by 2008. However, in spite of these efforts, during the last 3 years (2013–2015) China documented 27,695, 52,656, and 42,874 confirmed measles cases. How measles manages to spread in China—the world’s largest population—in the mass vaccination era remains poorly understood. To address this conundrum and provide insights for future public health efforts, we analyze the geospatial pattern of measles transmission across China during 2005–2014. We map measles incidence and incidence rates for each of the 344 cities in mainland China, identify the key socioeconomic and demographic features associated with high disease burden, and identify transmission clusters based on the synchrony of outbreak cycles. Using hierarchical cluster analysis, we identify 21 epidemic clusters, of which 12 were cross-regional. The cross-regional clusters included more underdeveloped cities with large numbers of emigrants than would be expected by chance (p = 0.011; bootstrap sampling), indicating that cities in these clusters were likely linked by internal worker migration in response to uneven economic development. In contrast, cities in regional clusters were more likely to have high rates of minorities and high natural growth rates than would be expected by chance (p = 0.074; bootstrap sampling). Our findings suggest that multiple highly connected foci of measles transmission coexist in China and that migrant workers likely facilitate the transmission of measles across regions. This complex connection renders eradication of measles challenging in China despite its high overall vaccination coverage. Future immunization programs should therefore target these transmission foci simultaneously.

Women Living Together Have a Higher Frequency of Menstrual Migraine.

Menstrual migraine is a highly prevalent disorder among adult women, resulting in disability and loss of quality of life. Some studies have reported menstrual cycle synchrony among women living together. No study has reported whether there may also be a higher prevalence of menstrual migraine among these women. Thus, they reported here the prevalence of menstrual migraine in a group of women living together compared with a control group of women living alone, and discussed the possible factors involved. The study was conducted on female university students aged 18-30 years with a diagnosis of migraine according to the criteria of the International Classification of Headache Disorders III, beta appendix criteria. The subjects were divided into a group of women who lived together with two or more other students and a control group of age-matched students who lived alone, interviewed with a specific questionnaire and assessed for 3 months by means of a paper pain diary. The data evaluated included frequency of headache, presence of menstrual migraine, intensity of headache, medications used including contraceptives, and triggering factors such as diet, sleep deprivation, and stress. The menstrual data and data related to migraine were also investigated in the roommates. A higher occurrence of menstrual migraine among women living together (9, 50%) compared with women living alone (3, 16.7%) (P = .03) was detected. After binary logistic regression analysis, this finding was not related to the main influencing factors detected, that is, use of a contraceptive, test stress, or sleep deprivation (P = .03, adjusted odds ratio: 7.87; 1.23-50.36). These women also showed menstrual cycle synchrony with their roommates (8, 44.4%) and the presence of headache crises during the menstruation of their colleagues (11, 61.1%). The present study detected a higher occurrence of menstrual migraine among women who lived together. Since there was no previous description of this topic in the literature, it was believed that the present study could represent a step toward more elaborate investigations of this complex topic.

Synchronization of Yeast.

The budding yeast Saccharomyces cerevisiae and fission yeast Schizosaccharomyces pombe are amongst the simplest and most powerful model systems for studying the genetics of cell cycle control. Because yeast grows very rapidly in a simple and economical media, large numbers of cells can easily be obtained for genetic, molecular, and biochemical studies of the cell cycle. The use of synchronized cultures greatly aids in the ease and interpretation of cell cycle studies. In principle, there are two general methods for obtaining synchronized yeast populations. Block-and-release methods can be used to induce cell cycle synchrony. Alternatively, centrifugal elutriation can be used to select synchronous populations. Because each method has innate advantages and disadvantages, the use of multiple approaches helps in generalizing results. An overview of the most commonly used methods to generate synchronized yeast cultures is presented along with working Notes: a section that includes practical comments, experimental considerations and observations, and hints regarding the pros and cons innate to each approach.

Flow Analysis and Sorting of Plant Chromosomes.

Analysis and sorting of plant chromosomes (plant flow cytogenetics) is a special application of flow cytometry in plant genomics and its success depends critically on sample quality. This unit describes the methodology in a stepwise manner, starting with the induction of cell cycle synchrony and accumulation of dividing cells in mitotic metaphase, and continues with the preparation of suspensions of intact mitotic chromosomes, flow analysis and sorting of chromosomes, and finally processing of the sorted chromosomes. Each step of the protocol is described in detail as some procedures have not been used widely. Supporting histograms are presented as well as hints on dealing with plant material; the utility of sorted chromosomes for plant genomics is also discussed. © 2016 by John Wiley & Sons, Inc.

Does in vitro maturation (IVM) have an impact on morphokinetic parameters in comparison with IVF?

Polycystic ovarian syndrome (PCOS) patients are at higher risk of ovarian hyper stimulation syndrome (OHSS) due to the high dose of gonadotropin in IVF. To avoid the possibility of OHSS, IVM techniques have been developed and employed in clinical settings. However, IVM delivers lower pregnancy rates and birth rates than IVF. The objective of this study was to assess whether IVM treatment affects embryo development events together with morphokinetic parameters compared with IVF, and to identify the morphokinetic parameters specific to embryos that were suitable for implantation in IVM cycles. Retrospective study. The subjects were 41 couples who underwent 50 cycles of IVM at our clinic, from May, 2013 to Nov., 2015. After the failure of IVM treatment, 12 couples underwent standard IVF treatment. We assessed 194 embryos derived from IVM-ICSI and 48 embryos derived from IVF-ICSI. Their treatment outcomes were analyzed with morphokinetic events (cell division and interval of cell cleavage) by Primovision (vitrolife Sweden), and rate of clinical outcome. Moreover in IVM cycles, these time points were also compared between transferred embryos that implanted or did not implant. IVM zygotes showed significantly lower good quality embryo on day3, blastocyst formation, and good blastocyst rates compared with IVF. There were no differences in time points of cell division (tPNa to t8), pregnancy and abortion rates between the two groups. However, there were significant differences in synchrony of the second cell cycles (t4-t3:S2) (S2:4.5±5.0h vs. 1.4±2.3h, P=0.0002), and the rate of direct cleavage of one to three, or there to five cells was significantly higher in the IVM group (90/194 46.4% vs. 9/48 18.8%, P=0.0016). In the IVM group, there were no differences in development time points between implanted and non-implanted embryos. IVM zygotes showed increased abnormal cleavage compared with IVF; however, there were no significant differences in pregnancy rate or abortion rate between IVM and IVF. We rejected these abnormal cleaved embryos for transfer, indicating that in order to improve the pregnancy rate it is important to exclude the abnormal cleaved embryo, such as direct cleavage, from embryo transfer in IVM treatment.

Testing socially mediated estrous synchrony or asynchrony in wild baboons

Social structure of animal groups is affected by the spatial and temporal distribution of females. In particular, the extent to which fertile periods of females are temporally overlapped has been deemed as a crucial factor to determine the structure of social groups in primate species. Dominant males are less able to monopolize fertile females when there are more females being in estrous simultaneously. This provides a potential opportunity for females to manipulate their defensibility by dominant males by modifying the level of estrous overlap. Previous studies that have attempted to detect socially mediated synchrony or asynchrony of estrous cycles have produced mixed results, some of which have been questioned on methodological grounds. Here, we address this issue using an exceptionally large dataset of daily reproductive states in four troops of wild anubis baboons (Papio anubis) over 14 to 24 years (77 troop-years). We compare observed levels of estrous synchrony with null distributions obtained by a randomization procedure under the assumption that estrous cycles are mutually independent among females in the same troop. We do not find any evidence supporting synchrony or asynchrony of estrous cycles. Based on our result and those of previous studies in other species of baboons, we conclude that socially mediated synchrony or asynchrony is unlikely to play a significant role in structuring social groups in baboons. In addition, our analysis points out that care should be taken when applying randomization procedures to a dataset with missing observations. Females in some animal species have been suggested to synchronize or desynchronize their estrus cycles. This phenomenon may have a significant impact on the structure of animal societies because when there are more females simultaneously in estrus, even a dominant male is less able to defend them from other males. Previous attempts to detect non-random estrous cycles in primates have produced mixed results, and some of them have been criticized on the methodological grounds. We investigate whether wild female anubis baboons exhibit non-random estrous cycles using a larger dataset than previous studies. For a statistical analysis, we use a randomization procedure, taking a biasing effect of missing observations into consideration. Consistent with earlier studies on other species of baboons, our analysis does not find any evidence supporting estrous synchrony or asynchrony in anubis baboons.

Life cycles of dominant mayflies (Ephemeroptera) on a torrent of the high Bolivian Andes

The mayflies of the temperate and cold zones have well-synchronized life cycles, distinct cohorts, short emergence and flight periods. In contrast, aquatic insects from the tropical zones are characterized by multivoltine life cycles, “non-discernible cohorts” and extended flight periods throughout the year. This report is the first observation of life cycle patterns made of two species of mayflies on a torrent in the high elevation Bolivian Andes. The samples were taken from four sites and four periods during a hydrological season. The life cycle of each species was examined using size-class frequency analysis and a monthly modal progression model (von Bertalanffy’s model) to infer the life cycle synchrony type. These first observations showed a moderately synchronized univoltine life cycle for Andesiops peruvianus (Ulmer, 1920), whereas Meridialaris tintinnabula Pescador and Peters (1987), had an unsynchronized multivoltine life cycle. These results showed that the generalization of all aquatic insects as unsynchronized multivoltine species in the Andean region may not be entirely accurate since there is still a need to further clarify the life cycle patterns of the wide variety of aquatic insects living in this high elevation tropical environment.

Migraine and menstrual cycle synchrony in females: is there a relationship? Case report

BACKGROUND AND OBJECTIVES: Migraine is a highly prevalent disorder among adult females, being that very often these patients have crises during the menstrual cycle. On the other hand, some studies have described menstrual cycle synchrony in females living together. No study has described whether there would also be migraine crisis synchrony among these females. This study aimed at reporting the case of a patient with migraine episodes synchronized with the menstrual cycle of her companion, discussing possible involved triggering factors. CASE REPORT: Female patient, 50 years old, menopausal for at least one year, with history of migraine without aura according to International Headache Society’s criteria, with typically migraine headache crises during her companion’s menstrual cycle. Patient was evaluated for 3 months by the pain diary, including frequency of headache crises, intensity of crises, drug doses and triggering factors for crises, in addition to follicle exfoliating hormone and estradiol dosing in different periods of the month. Patient had headache crises during her companion’s menstrual cycle with no evidence of other associated factors (diet, sleep deprivation, stress). Patient’s level of stimulating follicle hormone varied throughout the month, according to companion’s menstrual cycle. CONCLUSION: There is no consensus with regard to menstrual cycle synchrony among females. However, we believe that this report could be a step further for the development of further studies on such a complex subject.

A note on the onset of synchrony in avian ovulation cycles

Spontaneous oscillator synchrony occurs when populations of interacting oscillators begin cycling together in the absence of environmental forcing. Synchrony has been documented in many physical and biological systems, including oestrus/menstrual cycles in rats and humans. In previous work we showed that Glaucous-winged Gulls (Larus glaucescens) can lay eggs synchronously on an every-other-day schedule, and that synchrony increases with colony density. Here we pose a discrete-time model of avian ovulation to study the dynamics of synchronization. We prove the existence and uniqueness of an equilibrium solution which bifurcates to increasingly synchronous cycles as colony density increases.

Correction: Nonlinear Effect of Dispersal Rate on Spatial Synchrony of Predator-Prey Cycles

The name of the second author was given incorrectly. The correct name is: Geoffrey Legault.

An earlier uterine environment favors the in vivo development of fresh pig morulae and blastocysts transferred by a nonsurgical deep-uterine method.

This study aimed to evaluate the effect of recipient-donor estrous cycle synchrony on recipient reproductive performance after nonsurgical deep-uterine (NsDU) embryo transfer (ET). The transfers (N=132) were conducted in recipients sows that started estrus 24 h before (–24 h; N=9) or 0 h (synchronous; N=31), 24 h (+24 h; N=74) or 48 h (+48 h; N=18) after the donors. A total of 30 day 5 morulae or day 6 blastocysts (day 0=onset of estrus) were transferred per recipient. The highest farrowing rates (FRs) were achieved when estrus appeared in recipients 24 h later than that in the donors (81.1%), regardless of the embryonic stage used for the transfers. The FR notably decreased (P<0.05) when recipients were –24 h asynchronous (0%), synchronous (61.3%) or +48 h asynchronous (50%) relative to the donors. No differences in litter size (LS) and piglet birth weights were observed among the synchronous and +24 h or +48 h asynchronous groups. While a +24 h asynchronous recipient was suitable for transfers performed with either morulae (FR, 74.3%; LS, 9.2 ± 0.6 piglets) or blastocysts (FR, 84.6%; LS, 9.8 ± 0.6 piglets), a + 48 h asynchronous recipient was adequate for blastocysts (FR, 87.5%; LS, 10.4 ± 0.7 piglets) but not for morulae (FR, 30.0%; LS, 7.3 ± 2.3 piglets). In conclusion, this study confirms the effectiveness of the NsDU-ET technology and shows that porcine embryos tolerate better a less advanced uterine environment if they are nonsurgically transferred deep into the uterine horn.

Analyzing G1-S transcriptional control.

G1-S transcriptional control involves the coordination of the expression of a large set of co-regulated genes as a function of cell cycle progression (Bertoli et al., Nat Rev Mol Cell Biol 14:518-528, 2013). Confining transcription to the G1 phase of the cell cycle requires the regulation of specific transcription factor activity through either co-factors or regulation of promoter DNA binding. Therefore, the analysis of G1-S transcriptional control involves cell cycle synchronization and monitoring cell cycle synchrony, in order to establish DNA binding of G1-S transcription factors to G1-S promoters and to investigate changes in gene expression during the different phases of the cell cycle. Here, we describe a cell cycle synchrony method and ways to monitor synchrony. We also describe a chromatin immunoprecipitation (ChIP) method to locate G1-S transcription factor components to promoters and a quantitative PCR (qPCR) protocol to determine gene expression. Defining the binding dynamics of G1-S transcription factors and changes in gene expression during the cell cycle should provide new insights into the mechanism that control G1-S transcription and will allow for investigation of the biological relevance of confining gene expression to G1.

Nonlinear effect of dispersal rate on spatial synchrony of predator-prey cycles.

Spatially-separated populations often exhibit positively correlated fluctuations in abundance and other population variables, a phenomenon known as spatial synchrony. Generation and maintenance of synchrony requires forces that rapidly restore synchrony in the face of desynchronizing forces such as demographic and environmental stochasticity. One such force is dispersal, which couples local populations together, thereby synchronizing them. Theory predicts that average spatial synchrony can be a nonlinear function of dispersal rate, but the form of the dispersal rate-synchrony relationship has never been quantified for any system. Theory also predicts that in the presence of demographic and environmental stochasticity, realized levels of synchrony can exhibit high variability around the average, so that ecologically-identical metapopulations might exhibit very different levels of synchrony. We quantified the dispersal rate-synchrony relationship using a model system of protist predator-prey cycles in pairs of laboratory microcosms linked by different rates of dispersal. Paired predator-prey cycles initially were anti-synchronous, and were subject to demographic stochasticity and spatially-uncorrelated temperature fluctuations, challenging the ability of dispersal to rapidly synchronize them. Mean synchrony of prey cycles was a nonlinear, saturating function of dispersal rate. Even extremely low rates of dispersal (<0.4% per prey generation) were capable of rapidly bringing initially anti-synchronous cycles into synchrony. Consistent with theory, ecologically-identical replicates exhibited very different levels of prey synchrony, especially at low to intermediate dispersal rates. Our results suggest that even the very low rates of dispersal observed in many natural systems are sufficient to generate and maintain synchrony of cyclic population dynamics, at least when environments are not too spatially heterogeneous.

Months of Asynchrony in Offspring Production but Synchronous Adult Emergence: The Role of Diapause in an Ectoparasite's Life Cycle

Off-host stages of temperate zone ectoparasites must overcome two challenges: coping with unfavorable seasons and synchronizing their life cycles with host availability. In general, little is known about the seasonal cycles of insect ectoparasites of warm-blooded animals. The current study investigates the unusual phenology of a viviparous hippoboscid fly, the deer ked (Lipoptena cervi L.), that parasitizes boreal cervids. Despite months of asynchrony in offspring production, the adults emerge synchronously in mid-August across the northern boreal zone. We examined the role of diapause variation in the synchronization of life cycles by testing adult emergence success and time in relation to offspring birth month (October to April) and with respect to chilling time and photoperiod. Unexpectedly, we found that photoperiod had no role in regulating the life cycle, but diapause was maintained as long as pupae were exposed to cold. Pupae born before February needed a slightly longer exposure to high temperatures to terminate diapause if the cold period was short. Despite the apparent importance of a long period of chilling for life cycle synchrony, it was not required to terminate diapause. This finding of cold mainly preventing, rather than promoting, diapause termination is not novel among temperate insects, but it is rare. Slow diapause termination as a response to exceptionally long exposure to high, not low, temperatures seems to be a cornerstone for synchronizing the life cycle in the deer ked.

The sensitivity of wood production to seasonal and interannual variations in climate in a lowland Amazonian rainforest

Understanding climatic controls on tropical forest productivity is key to developing more reliable models for predicting how tropical biomes may respond to climate change. Currently there is no consensus on which factors control seasonal changes in tropical forest tree growth. This study reports the first comprehensive plot-level description of the seasonality of growth in a Peruvian tropical forest. We test whether seasonal and interannual variations in climate are correlated with changes in biomass increment, and whether such relationships differ among trees with different functional traits. We found that biomass increments, measured every 3 months on the two plots, were reduced by between 40 and 55% in the peak dry season (July-September) relative to peak wet season (January-March). The seasonal patterns of biomass accumulation are significantly (p < 0.01) associated with seasonal patterns of rainfall and soil water content; however, this may reflect a synchrony of seasonal cycles rather than direct physiological controls on tree growth rates. The strength of the growth seasonality response among trees is significantly correlated to functional traits: consistent with a hypothesised trade-off between maximum potential growth rate and hydraulic safety, tall and fast-growing trees with broad stems had the most strongly seasonal biomass accumulation, suggesting that they are more productive in the wet season, but more vulnerable to water limitation in the dry season.

Hormonal manipulations in the 5-day timed artificial insemination protocol to optimize estrous cycle synchrony and fertility in dairy heifers

Objectives were to determine the effects of GnRH at the initiation of the 5-d timed artificial insemination (AI) program combined with 2 injections of PGF2α on ovarian responses and pregnancy per AI (P/AI) in dairy heifers, and the role of progesterone concentrations on LH release and ovulation in response to GnRH. In study 1, heifers received a controlled internal drug release (CIDR) insert containing 1.38g of progesterone on d 0, an injection of 25 mg of PGF2α and CIDR removal on d 5, and an injection of 100μg GnRH concurrently with AI on d 8. Heifers were assigned to receive no additional treatment (control; n=559) or an injection of GnRH on d 0 and a second injection of PGF2α on d 6 (G2P; n=547). In study 2, all heifers were treated as described for the control in study 1, and were allocated to receive no additional treatment (control; n=723), an injection of PGF2α on d 6 (NG2P; n=703), or an injection of GnRH on d 0 and an injection of PGF2α on d 6 (G2P; n=718). In study 3, heifers received a CIDR on d 7 after ovulation and were assigned randomly to a low-progesterone (LP; n=6) treatment in which 2 injections of 25 mg of PGF2α each were administered 12h apart, on d 7 and 7.5 after ovulation, or to a high-progesterone (HP; n=12) treatment in which no PGF2α was administered. On d 8, heifers received 100μg of GnRH and blood was sampled at every 15min from −30 to 180min relative to the GnRH for assessment of LH concentrations. Additionally, 94 heifers were assigned to LP or HP and ovulation in response to GnRH was evaluated. In study 1, P/AI was greater for G2P than for the control on d 32 (59.4 vs. 53.5%) and 60 after AI (56.6 vs. 51.3%). In study 2, administration of GnRH on d 0 increased the proportion of heifers with a new corpus luteum on d 5 (control=21.9 vs. NG2P=20.1 vs. G2P=34.4%). Administration of a second PGF2α increased the proportion of heifers with progesterone <0.5 ng/mL at AI (control=83.1 vs. NG2P=93.0 and G2P=87.2%). Pregnancy per AI was greater for G2P than for control and NG2P on d 32 (control=52.9 vs. NG2P=55.0 vs. G2P=61.7%) and 60 (control=49.0 vs. NG2P=51.6 vs. G2P=59.1%). In study 3, HP attenuated LH release and reduced ovulation (19.0 vs. 48.4%) in response to GnRH compared with LP. Combining GnRH and 2 doses of PGF2α in the 5-d timed AI protocol improved follicle turnover, luteolysis, and P/AI in heifers. Elevated concentrations of progesterone suppressed LH release and are linked with the low ovulatory response to the initial GnRH treatment of the protocol.

Cell Cycle Synchrony of Propagated and Recycled Lager Yeast and Its Impact on Lag Phase in Fermenter

A rapid fluorescence measurement based on resazurin reduction was developed and applied for the detection of toxicants/inhibitors to anaerobic digestion metabolism. By initially using a pure facultative anaerobic strain, Enterococcus faecalis as a model organism, this technique proved to be fast and sensitive when detecting the model toxicant, pentachlorophenol (PCP). The technique revealed significant metabolic changes in Enterococcus faecalis with a PCP spike ranging from 0.05 to 100 mg/L, and could detect PCP's toxicity to E. faecalis at a concentration of only 0.05 mg/L in 8 min. Furthermore, by extending this technique to a mixed anaerobic sludge, not only could the effect of 0.05–100 mg/L PCP be determined on anaerobic digestion metabolism within 10 min, but also its rate of biogas production. These results suggest that a resazurin-based fluorescence measurement can potentially be incorporated into a microfluidic system to develop a biosensor for the real-time monitoring, control and early warning of toxicant/inhibitor loads in the influent to an anaerobic digestion system.

Synchronized swimming: coordination of pelvic and pectoral fins during augmented punting by the freshwater stingray Potamotrygon orbignyi

Benthic animals live at the juncture of fluid and solid environments, an interface that shapes many aspects of their behavior, including their means of locomotion. Aquatic walking and similar substrate-dependent forms of underwater propulsion have evolved multiple times in benthic invertebrate and vertebrate taxa, including batoid elasmobranchs. Skates (Rajidae) use the pelvic fins to punt across the substrate, keeping the pectoral fin disc still. Other batoids combine pelvic fin motions with pectoral fin undulation in augmented punting, but the coordination of these two modes has not been described. In this study of an augmented punter, the freshwater stingray Potamotrygon orbignyi, we demonstrate the synchrony of pelvic and pectoral fin cycles. The punt begins as the pelvic fins, held in an anterior position, are planted into the substrate and used to push the body forward. Meanwhile, a wave of pectoral fin undulation begins, increasing to maximum height just before the cycle's halfway point, when the pelvic fins reach their furthest posterior extension. The pectoral fin wave subsides as the pelvic fins return to their starting position for subsequent punts. Despite definitive links between pectoral and pelvic fin activity, we find no significant relationship between pectoral fin kinematics (frequency, wave height, and wave speed) and punt performance. However, slip calculations indicate that pectoral undulation can produce thrust and augment punting. Pelvic fin kinematics (frequency and duty factor) have significant effects, suggesting that while both sets of fins contribute to thrust generation, the pelvic fins likely determine punt performance.

Comparative gene expression between two yeast species

BackgroundComparative genomics brings insight into sequence evolution, but even more may be learned by coupling sequence analyses with experimental tests of gene function and regulation. However, the reliability of such comparisons is often limited by biased sampling of expression conditions and incomplete knowledge of gene functions across species. To address these challenges, we previously systematically generated expression profiles in Saccharomyces bayanus to maximize functional coverage as compared to an existing Saccharomyces cerevisiae data repository.ResultsIn this paper, we take advantage of these two data repositories to compare patterns of ortholog expression in a wide variety of conditions. First, we developed a scalable metric for expression divergence that enabled us to detect a significant correlation between sequence and expression conservation on the global level, which previous smaller-scale expression studies failed to detect. Despite this global conservation trend, between-species gene expression neighborhoods were less well-conserved than within-species comparisons across different environmental perturbations, and approximately 4% of orthologs exhibited a significant change in co-expression partners. Furthermore, our analysis of matched perturbations collected in both species (such as diauxic shift and cell cycle synchrony) demonstrated that approximately a quarter of orthologs exhibit condition-specific expression pattern differences.ConclusionsTaken together, these analyses provide a global view of gene expression patterns between two species, both in terms of the conditions and timing of a gene's expression as well as co-expression partners. Our results provide testable hypotheses that will direct future experiments to determine how these changes may be specified in the genome.

Ciclo gametogênico e comportamento reprodutivo de Iphigenia brasiliana (Mollusca, Bivalvia, Donacidae) no estuário do rio Subaé, Baía de Todos os Santos, Bahia, Brasil

Este estudo teve como objetivos descrever o ciclo gametogênico e o comportamento reprodutivo da população de Iphigenia brasiliana (Lamarck,1818) no estuário do rio Subaé, Baía de Todos os Santos, Bahia. Os bivalves foram coletados de novembro de 2001 a novembro de 2002. Um total de 244 espécimes foi medido (eixo anteroposterior), eviscerado, fixado, desidratado e incluído em parafina. O estudo histológico das gônadas foi realizado através de cortes seriados do tecido gonadal, de 5 mm de espessura, e corados pela HE. O tamanho médio mínimo da primeira maturação sexual (Lpm) foi estimado a partir da distribuição das frequências relativas de jovens e adultos, por classe de comprimento dos indivíduos. As frequências relativas dos sexos em cada estádio de desenvolvimento foram consideradas conjuntamente para a análise do comportamento reprodutivo da população, e, em separado, para avaliar a sincronia do ciclo sexual entre machos e fêmeas. Foi observada uma variação de tamanhos entre 9,1 e 66,6 mm, com comprimento médio de 50,2 mm. O estudo não demonstrou diferença significativa entre os tamanhos de machos e fêmeas. Não foi possível observar a diferenciação de sexos em 2,1% dos indivíduos analisados. 51,6% dos indivíduos foram identificados como machos (M) e 46,3% como fêmeas (F), não sendo constatadas diferenças significativas entre o número médio de machos e fêmeas, resultando numa proporção de M:F de 1,1:1. O Lpm foi estimado em 11,4 mm, mas apenas ao alcançarem comprimento médio de 34,4 mm, todos os indivíduos foram considerados adultos. Foram caracterizados quatro estádios de evolução do desenvolvimento gonadal em fêmeas e machos. A análise dos diferentes estádios permitiu a observação dos fenômenos de atresia e inversão sexual em fêmeas. O ciclo reprodutivo apresentou eliminação contínua de gametas, com maiores intensidades reprodutivas nos meses de novembro de 2001 a abril de 2002 e, também, no mês de outubro de 2002.