De novo evolution of macroscopic multicellularity.

While early multicellular lineages necessarily started out as relatively simple groups of cells, little is known about how they became Darwinian entities capable of sustained multicellular evolution1-3. Here we investigate this with a multicellularity long-term evolution experiment, selecting for larger group size in the snowflake yeast (Saccharomyces cerevisiae) model system. Given the historical importance of oxygen limitation4, our ongoing experiment consists of three metabolic treatments5-anaerobic, obligately aerobic and mixotrophic yeast. After 600 rounds of selection, snowflake yeast in the anaerobic treatment group evolved to be macroscopic, becoming around 2 × 104 times larger (approximately mm scale) and about 104-fold more biophysically tough, while retaining a clonal multicellular life cycle. This occurred through biophysical adaptation-evolution of increasingly elongate cells that initially reduced the strain of cellular packing and then facilitated branch entanglements that enabled groups of cells to stay together even after many cellular bonds fracture. By contrast, snowflake yeast competing for low oxygen5 remained microscopic, evolving to be only around sixfold larger, underscoring the critical role of oxygen levels in the evolution of multicellular size. Together, this research provides unique insights into an ongoing evolutionary transition in individuality, showing how simple groups of cells overcome fundamental biophysical limitations through gradual, yet sustained, multicellular evolution.

Good practice recommendations on add-ons in reproductive medicine†.

STUDY QUESTION: Which add-ons are safe and effective to be used in ART treatment? SUMMARY ANSWER: Forty-two recommendations were formulated on the use of add-ons in the diagnosis of fertility problems, the IVF laboratory and clinical management of IVF treatment. WHAT IS KNOWN ALREADY: The innovative nature of ART combined with the extremely high motivation of the patients has opened the door to the wide application of what has become known as 'add-ons' in reproductive medicine. These supplementary options are available to patients in addition to standard fertility procedures, typically incurring an additional cost. A diverse array of supplementary options is made available, encompassing tests, drugs, equipment, complementary or alternative therapies, laboratory procedures, and surgical interventions. These options share the common aim of stating to enhance pregnancy or live birth rates, mitigate the risk of miscarriage, or expedite the time to achieving pregnancy. STUDY DESIGN, SIZE, DURATION: ESHRE aimed to develop clinically relevant and evidence-based recommendations focusing on the safety and efficacy of add-ons currently used in fertility procedures in order to improve the quality of care for patients with infertility. PARTICIPANTS/MATERIALS, SETTING, METHODS: ESHRE appointed a European multidisciplinary working group consisting of practising clinicians, embryologists, and researchers who have demonstrated leadership and expertise in the care and research of infertility. Patient representatives were included in the working group. To ensure that the guidelines are evidence-based, the literature identified from a systematic search was reviewed and critically appraised. In the absence of any clear scientific evidence, recommendations were based on the professional experience and consensus of the working group. The guidelines are thus based on the best available evidence and expert agreement. Prior to publication, the guidelines were reviewed by 46 independent international reviewers. A total of 272 comments were received and incorporated where relevant. MAIN RESULTS AND THE ROLE OF CHANCE: The multidisciplinary working group formulated 42 recommendations in three sections; diagnosis and diagnostic tests, laboratory tests and interventions, and clinical management. LIMITATIONS, REASONS FOR CAUTION: Of the 42 recommendations, none could be based on high-quality evidence and only four could be based on moderate-quality evidence, implicating that 95% of the recommendations are supported only by low-quality randomized controlled trials, observational data, professional experience, or consensus of the development group. WIDER IMPLICATIONS OF THE FINDINGS: These guidelines offer valuable direction for healthcare professionals who are responsible for the care of patients undergoing ART treatment for infertility. Their purpose is to promote safe and effective ART treatment, enabling patients to make informed decisions based on realistic expectations. The guidelines aim to ensure that patients are fully informed about the various treatment options available to them and the likelihood of any additional treatment or test to improve the chance of achieving a live birth. STUDY FUNDING/COMPETING INTEREST(S): All costs relating to the development process were covered from ESHRE funds. There was no external funding of the development process or manuscript production. K.L. reports speakers fees from Merck and was part of a research study by Vitrolife (unpaid). T.E. reports consulting fees from Gynemed, speakers fees from Gynemed and is part of the scientific advisory board of Hamilton Thorne. N.P.P. reports grants from Merck Serono, Ferring Pharmaceutical, Theramex, Gedeon Richter, Organon, Roche, IBSA and Besins Healthcare, speakers fees from Merck Serono, Ferring Pharmaceutical, Theramex, Gedeon Richter, Organon, Roche, IBSA and Besins Healthcare. S.R.H. declares being managing director of Fertility Europe, a not-for-profit organization receiving financial support from ESHRE. I.S. is a scientific advisor for and has stock options from Alife Health, is co-founder of IVFvision LTD (unpaid) and received speakers' fee from the 2023 ART Young Leader Prestige workshop in China. A.P. reports grants from Gedeon Richter, Ferring Pharmaceuticals and Merck A/S, consulting fees from Preglem, Novo Nordisk, Ferring Pharmaceuticals, Gedeon Richter, Cryos and Merck A/S, speakers fees from Gedeon Richter, Ferring Pharmaceuticals, Merck A/S, Theramex and Organon, travel fees from Gedeon Richter. The other authors disclosed no conflicts of interest. DISCLAIMER: This Good Practice Recommendations (GPRs) document represents the views of ESHRE, which are the result of consensus between the relevant ESHRE stakeholders and are based on the scientific evidence available at the time of preparation.ESHRE GPRs should be used for information and educational purposes. They should not be interpreted as setting a standard of care or bedeemedinclusive of all proper methods of care, or be exclusive of other methods of care reasonably directed to obtaining the same results.Theydo not replace the need for application of clinical judgement to each individual presentation, or variations based on locality and facility type.Furthermore, ESHRE GPRs do not constitute or imply the endorsement, or favouring, of any of the included technologies by ESHRE.

Can endometrial compaction predict live birth rates in assisted reproductive technology cycles? A systematic review and meta-analysis.

PURPOSE: Endometrial compaction (EC) is defined as the difference in endometrial thickness from the end of the follicular phase to the day of embryo transfer (ET). We aimed to determine the role of EC in predicting assisted reproductive technology (ART) success by conducting a meta-analysis of studies reporting the association between EC and clinical outcomes of ART. METHODS: MEDLINE via PubMed, Web of Science, Scopus, and the Cochrane Central Register of Controlled Trials (CENTRAL) were searched from the date of inception to May 19, 2023. The primary outcome was live birth rate (LBR) per ET. Secondary outcomes were live birth or ongoing pregnancy per ET, ongoing pregnancy per ET, clinical pregnancy per ET, and miscarriage per clinical pregnancy. RESULTS: Fifteen studies were included. When data from all studies reporting live birth were pooled, overall LBR rates were comparable in cycles showing EC or not [RR = 0.97, 95%CI = 0.92 to 1.02; 10 studies, 11,710 transfer cycles]. In a subgroup of studies that included euploid ET cycles, a similar LBR for patients with and without EC was noted [RR = 0.99, 95%CI = 0.86 to 1.13, 4 studies, 1172 cycles]. The miscarriage rate did not seem to be affected by the presence or absence of EC [RR = 1.06, 95%CI = 0.90 to 1.24; 12 studies]. CONCLUSION: The predictive value of EC in determining LBR is limited, and assessment of EC may no longer be necessary, given these findings. TRIAL REGISTRATION: PROSPERO CRD42023410389.

Association between methylenetetrahydrofolate reductase (MTHFR) gene promoter hypermethylation and the risk of idiopathic male infertility.

Epigenetics has become a major field of reproductive medicine after the epigenetic regulation of gene expression was discovered. The aim of this study was to find out whether or not methylenetetrahydrofolate reductase (MTHFR) gene promoter hypermethylation in the spermatozoa of men who were offered assisted reproduction is associated with idiopathic male infertility. Sperm DNAs from 40 idiopathic infertile men with normozoospermia and 40 controls consisting of healthy fertile men were isolated. Following the modification of DNAs by sodium bisulphite, the methylation status of the MTHFR gene promoter was quantified by pyrosequencing. No significant differences were observed between the clinical characteristics of patients and controls. The percentage of MTHFR promoter methylation in infertile men with normozoospermia (11%) was significantly higher than that in the healthy control (4.3%) group (p = .01). A 9.5% of methylation level was determined via receiver operator characteristic (ROC) analysis as the cut-off value. There were 21 (53%) hypermethylated men among the infertile men and 2 (5%) in the control group (p = .0001). The intragroup analysis of the infertile group did not reveal any statistically significant differences in terms of overall clinical characteristics between hyper- and normo-methylated infertile men. Our results suggest that epigenetic silencing (hypermethylation) of MTHFR could result in an elevated risk of male infertility.

Revisiting serum beta-human chorionic gonadotropin concentrations as a predictor for dizygotic twinning after in vitro fertilization.

PURPOSE OF INVESTIGATION: To determine a cut-off value for beta-human chorionic gonadotropin (ß-hCG) concentrations to predict dizygotic twinning after in vitro fertilization (IVF) and double embryo transfer (DET). MATERIALS AND METHODS: This retrospective cohort study included 233 women who conceived after DET at IVF center, Hacettepe University Faculty of Medicine. Patients with serum P-hCG concentration 25 IU/l assayed on day 14 after oocyte retrieval were included into the study. RESULTS: Lower serum ß-hCG concentrations were observed in non-viable pregnancy when compared to their viable counterparts. In addition, twins exhibited higher 0- hCG concentrations than singletons did. Receiver operator characteristic (ROC) curve analysis showed a significant relationship between serum ßhCG concentrations and the occurrence of twin pregnancy (area under the curve = 0.85, 95% confidence interval = 0.79-0.91, p < 0.001). For twin pregnancy, when ß-hCG ≥ 175 IU/l, sensitivity was 77.3%, specificity was 80.0%, positive predictive value (PPV) was 48.2%, and negative predictive value (NPV) was 93.8%. CONCLUSION: P-hCG > 175 IU/I might be used as a new cut-off value for early prediction of viable dizygotic twins following IVF-DET treatment cycles.

Histopathology of ipsilateral and contralateral ovaries and plasma interleukin 6 levels after unilateral ovarian torsion.

OBJECTIVE: The aim of the present study was to evaluate the time-dependent histopathologic changes in both ovaries and to determine the time-dependent levels of plasma interleukin 6 (IL-6) after unilateral ovarian torsion. MATERIALS AND METHODS: An experimental animal study included 48 female Sprague-Dawley rats which were distributed to six groups: control group (Group 1), sham-operated control group (Group 2), and four unilateral ovarian torsion groups with torsion duration of three, six, 12, and 24 hours (Group 3, 4, 5, and 6, respectively). Histopathologic criteria (follicular degeneration, vascular congestion, hemorrhage, inflammatory cell infiltration, and total tissue damage score) were evaluated in both ovaries, and plasma IL-6 levels were measured. RESULTS: At 24 hours after torsion began, mean total tissue damage score was similar between ovaries that had torsion and contralateral ovaries. Mean plasma IL-6 level did not change during the 24 hours after torsion began (p = 0.584). CONCLUSIONS: In addition to ovaries that had torsion, histopathologic abnormalities also occurred in contralateral ovaries. These results suggest that contralateral ovaries are not quiescent after unilateral ovarian torsion. Plasma IL-6 levels did not change significantly during the 24 hours after ovarian torsion began, resulting in a limitation of its diagnostic use in the early course of the disease.

Luteal-long GnRH agonist versus flexible-multidose GnRH antagonist protocols for overweight and obese patients who underwent ICSI.

A total of 413 consecutive infertile patients (572 cycles) with a body mass index (BMI) of ≥ 25 kg/m(2) were enrolled into the study. The luteal-long GnRH agonist group (Group I) constituted 211 patients (300 cycles) and the flexible-multidose GnRH antagonist group (Group II) constituted 202 patients (272 cycles). The duration of stimulation (d) (10.1 ± 2.5 vs. 9.2 ± 2.0; p < 0.01); the total dose of gonadotrophin used (IU) (3,099.4 ± 2,885.0 vs. 2,684.0 ± 1,046.4; p < 0.05) and the E2 level on the day of hCG (pg/ml) (2,375.8 ± 1,554.6 vs. 1,905.6 ± 1,598.8; p < 0.01) were significantly lower in Group II when compared with Group I. However, the ongoing pregnancy per embryo transfer (37.0% vs. 25.7%; p < 0.05) and the implantation rate (25.7% vs. 15.6%; p < 0.01) were significantly lower in Group II when compared with Group I. In conclusion, we noted that the luteal-long GnRH agonist protocol produced higher implantation rates and higher clinical-ongoing pregnancy rates in overweight and obese patients when compared with the flexible-multidose GnRH antagonist protocol.

Live birth after transfer of vitrified-warmed blastocyst derived from ICSI with frozen-thawed sperm: case report.

OBJECTIVE: A live birth after transfer of vitrified-warmed blastocyst derived from intracytoplasmic sperm injection (ICSI) with frozen-thawed sperm of a male cancer patient is described. MATERIALS AND METHODS: A case report from a tertiary center for assisted reproductive technologies. The 35-year-old male patient had been diagnosed with testicular tumor nine years ago. He had unilateral orchiectomy operation after the diagnosis. Four years after the first operation, he was diagnosed with another testicular tumor in the other testis. He admitted to our center with the demand of sperm preservation before the second surgery. The sperm samples were cryopreserved and stored in liquid nitrogen until required. The patient had no chemotherapy or radiotherapy after the operations. After he completed his oncologic follow up, ICSI was decided with his frozen samples. Although the couple failed to conceive with the fresh cycle, the remaining embryos were frozen and revealed a pregnancy in the subsequent frozen-thawed cycle. RESULTS: A healthy female infant with a birth weight of 3,700 g was born by cesarean section at 38th weeks of the gestation. CONCLUSION: Giving detailed information about fertility-saving management in male patients is important in those who wish to bear children. However, both the patients and physicians should be cautious that preservation should be performed before surgery and/or adjuvant therapy. In this respect, assited reproductive technology (ART) and related facilities yield chance of pregnancy in such population.

The genetics of a putative social trait in natural populations of yeast.

The sharing of secreted invertase by yeast cells is a well-established laboratory model for cooperation, but the only evidence that such cooperation occurs in nature is that the SUC loci, which encode invertase, vary in number and functionality. Genotypes that do not produce invertase can act as 'cheats' in laboratory experiments, growing on the glucose that is released when invertase producers, or 'cooperators', digest sucrose. However, genetic variation for invertase production might instead be explained by adaptation of different populations to different local availabilities of sucrose, the substrate for invertase. Here we find that 110 wild yeast strains isolated from natural habitats, and all contained a single SUC locus and produced invertase; none were 'cheats'. The only genetic variants we found were three strains isolated instead from sucrose-rich nectar, which produced higher levels of invertase from three additional SUC loci at their subtelomeres. We argue that the pattern of SUC gene variation is better explained by local adaptation than by social conflict.

Manual versus computer-automated semen analysis.

OBJECTIVE: To evaluate agreement of conventional sperm analysis with computer-aided semen analysis (CASA) regarding concentration, motility, and morphology using samples from infertile men. MATERIALS AND METHODS: In this study a total of 195 male partners of couples who underwent evaluation of infertility were included. All semen samples were examined by conventional method and CASA in terms of morphology, motility, and concentration. Pearson correlation analysis and the Bland-Altman method were used to assess correlation and agreement between conventional semen analysis and CASA measurements. RESULTS: When the two methods were compared in terms of concentration, motility, and morphology, there was a statistically significant correlation in all variables. The best correlation was obtained for sperm concentration. However, there was a poor correlation for sperm morphology between conventional method and CASA. Sperm concentration and morphology obtained by CASA were 14% and 87% lower, respectively; motility was 21% higher than the conventional method. CONCLUSION: Although CASA systems are objective and rapid, they should be evaluated in terms of cost-effectiveness, however they may be useful in over-loaded assisted reproductive technique (ART) clinics.

Can combination of Day 3 and Day 5 embryo morphology be useful to predict pregnancy in in-vitro fertilization cycles?

OBJECTIVE: To determine whether embryos having all top qualified both on Day 3 and Day 5 have higher pregnancy rates than the oth- ers. MATERIALS AND METHODS: The study included 143 consecutive cycles were recruited in which Day 5 embryo transfer was available. Cleavage stage embryos were graded according to 1 to 4 scoring system, based on fragmentation, cell symmetry, and blastomere num- ber. Among cleavage stage embryos, Grade 1 and Grade 2a/2b were further stratified as 'top quality' embryos to be transferred, others were defined as control group. Blastocyst stage embryos were graded from 1 to 6 according to intracellular mass (ICM) and trophec- toderm (TE). Day 5 fresh embryo transfer was performed in all cases using soft catheter. Positive pregnancy test was accepted when serum beta-human chorionic gonadotrophin (1-hCG) exceeded 20 mIU/ml. RESULTS: On the cleavage stage, top quality embryo was available in 47 of 143(32.9%) cases. Of the 47 embryos, the number of cases reaching any Grade 4, 3 quality, and early blastocyst on Day 5 were 22 (46.8%), 15 (31.9%), and 10 (21.3%). The respective figures on the control group (n = 96) were 33 (34.4%), 37 (38.5%), and 26 (27.1%) (p > 0.05). The pregnancy rates were also similar. CONCLUSION: All top qualified embryos both on Day 3 and 5 did not reveal higher pregnancy rate than the others.

Metabolically-driven flows enable exponential growth in macroscopic multicellular yeast.

The ecological and evolutionary success of multicellular lineages is due in no small part to their increased size relative to unicellular ancestors. However, large size also poses biophysical challenges, especially regarding the transport of nutrients to all cells; these constraints are typically overcome through multicellular innovations (e.g., a circulatory system). Here we show that an emergent biophysical mechanism - spontaneous fluid flows arising from metabolically-generated density gradients - can alleviate constraints on nutrient transport, enabling exponential growth in nascent multicellular clusters of yeast lacking any multicellular adaptations for nutrient transport or fluid flow. Surprisingly, beyond a threshold size, the metabolic activity of experimentally-evolved snowflake yeast clusters drives large-scale fluid flows that transport nutrients throughout the cluster at speeds comparable to those generated by the cilia of extant multicellular organisms. These flows support exponential growth at macroscopic sizes that theory predicts should be diffusion limited. This work demonstrates how simple physical mechanisms can act as a 'biophysical scaffold' to support the evolution of multicellularity by opening up phenotypic possibilities prior to genetically-encoded innovations. More broadly, our findings highlight how co-option of conserved physical processes is a crucial but underappreciated facet of evolutionary innovation across scales.

Proteostatic tuning underpins the evolution of novel multicellular traits.

The evolution of multicellularity paved the way for the origin of complex life on Earth, but little is known about the mechanistic basis of early multicellular evolution. Here, we examine the molecular basis of multicellular adaptation in the Multicellularity Long Term Evolution Experiment (MuLTEE). We demonstrate that cellular elongation, a key adaptation underpinning increased biophysical toughness and organismal size, is convergently driven by downregulation of the chaperone Hsp90. Mechanistically, Hsp90-mediated morphogenesis operates by destabilizing the cyclin-dependent kinase Cdc28, resulting in delayed mitosis and prolonged polarized growth. Reinstatement of Hsp90 or Cdc28 expression resulted in shortened cells that formed smaller groups with reduced multicellular fitness. Together, our results show how ancient protein folding systems can be tuned to drive rapid evolution at a new level of biological individuality by revealing novel developmental phenotypes.

Proteostatic tuning underpins the evolution of novel multicellular traits.

The evolution of multicellularity paved the way for the origin of complex life on Earth, but little is known about the mechanistic basis of early multicellular evolution. Here, we examine the molecular basis of multicellular adaptation in the multicellularity long-term evolution experiment (MuLTEE). We demonstrate that cellular elongation, a key adaptation underpinning increased biophysical toughness and organismal size, is convergently driven by down-regulation of the chaperone Hsp90. Mechanistically, Hsp90-mediated morphogenesis operates by destabilizing the cyclin-dependent kinase Cdc28, resulting in delayed mitosis and prolonged polarized growth. Reinstatement of Hsp90 or Cdc28 expression resulted in shortened cells that formed smaller groups with reduced multicellular fitness. Together, our results show how ancient protein folding systems can be tuned to drive rapid evolution at a new level of biological individuality by revealing novel developmental phenotypes.

Chapter 5: Major Biological Innovations in the History of Life on Earth.

All organisms living on Earth descended from a single, common ancestral population of cells, known as LUCA-the last universal common ancestor. Since its emergence, the diversity and complexity of life have increased dramatically. This chapter focuses on four key biological innovations throughout Earth's history that had a significant impact on the expansion of phylogenetic diversity, organismal complexity, and ecospace habitation. First is the emergence of the last universal common ancestor, LUCA, which laid the foundation for all life-forms on Earth. Second is the evolution of oxygenic photosynthesis, which resulted in global geochemical and biological transformations. Third is the appearance of a new type of cell-the eukaryotic cell-which led to the origin of a new domain of life and the basis for complex multicellularity. Fourth is the multiple independent origins of multicellularity, resulting in the emergence of a new level of complex individuality. A discussion of these four key events will improve our understanding of the intertwined history of our planet and its inhabitants and better inform the extent to which we can expect life at different degrees of diversity and complexity elsewhere.

Emergence and maintenance of stable coexistence during a long-term multicellular evolution experiment.

The evolution of multicellular life spurred evolutionary radiations, fundamentally changing many of Earth's ecosystems. Yet little is known about how early steps in the evolution of multicellularity affect eco-evolutionary dynamics. Through long-term experimental evolution, we observed niche partitioning and the adaptive divergence of two specialized lineages from a single multicellular ancestor. Over 715 daily transfers, snowflake yeast were subjected to selection for rapid growth, followed by selection favouring larger group size. Small and large cluster-forming lineages evolved from a monomorphic ancestor, coexisting for over ~4,300 generations, specializing on divergent aspects of a trade-off between growth rate and survival. Through modelling and experimentation, we demonstrate that coexistence is maintained by a trade-off between organismal size and competitiveness for dissolved oxygen. Taken together, this work shows how the evolution of a new level of biological individuality can rapidly drive adaptive diversification and the expansion of a nascent multicellular niche, one of the most historically impactful emergent properties of this evolutionary transition.

Whole-genome duplication in the Multicellularity Long Term Evolution Experiment.

Whole-genome duplication (WGD) is widespread across eukaryotes and can promote adaptive evolution1-4. However, given the instability of newly-formed polyploid genomes5-7, understanding how WGDs arise in a population, persist, and underpin adaptations remains a challenge. Using our ongoing Multicellularity Long Term Evolution Experiment (MuLTEE)8, we show that diploid snowflake yeast (Saccharomyces cerevisiae) under selection for larger multicellular size rapidly undergo spontaneous WGD. From its origin within the first 50 days of the experiment, tetraploids persist for the next 950 days (nearly 5,000 generations, the current leading edge of our experiment) in ten replicate populations, despite being genomically unstable. Using synthetic reconstruction, biophysical modeling, and counter-selection experiments, we found that tetraploidy evolved because it confers immediate fitness benefits in this environment, by producing larger, longer cells that yield larger clusters. The same selective benefit also maintained tetraploidy over long evolutionary timescales, inhibiting the reversion to diploidy that is typically seen in laboratory evolution experiments. Once established, tetraploidy facilitated novel genetic routes for adaptation, playing a key role in the evolution of macroscopic multicellular size via the origin of evolutionarily conserved aneuploidy. These results provide unique empirical insights into the evolutionary dynamics and impacts of WGD, showing how it can initially arise due to its immediate adaptive benefits, be maintained by selection, and fuel long-term innovations by creating additional dimensions of heritable genetic variation.

Chapter 1: The Astrobiology Primer 3.0.

The Astrobiology Primer 3.0 (ABP3.0) is a concise introduction to the field of astrobiology for students and others who are new to the field of astrobiology. It provides an entry into the broader materials in this supplementary issue of Astrobiology and an overview of the investigations and driving hypotheses that make up this interdisciplinary field. The content of this chapter was adapted from the other 10 articles in this supplementary issue and thus represents the contribution of all the authors who worked on these introductory articles. The content of this chapter is not exhaustive and represents the topics that the authors found to be the most important and compelling in a dynamic and changing field.

Emergence and maintenance of stable coexistence during a long-term multicellular evolution experiment.

The evolution of multicellular life spurred evolutionary radiations, fundamentally changing many of Earth’s ecosystems. Yet little is known about how early steps in the evolution of multicellularity transform eco-evolutionary dynamics, e.g., via niche expansion processes that may facilitate coexistence. Using long-term experimental evolution in the snowflake yeast model system, we show that the evolution of multicellularity drove niche partitioning and the adaptive divergence of two distinct, specialized lineages from a single multicellular ancestor. Over 715 daily transfers, snowflake yeast were subject to selection for rapid growth in rich media, followed by selection favoring larger group size. Both small and large cluster-forming lineages evolved from a monomorphic ancestor, coexisting for over ~4,300 generations. These small and large sized snowflake yeast lineages specialized on divergent aspects of a trade-off between growth rate and survival, mirroring predictions from ecological theory. Through modeling and experimentation, we demonstrate that coexistence is maintained by a trade-off between organismal size and competitiveness for dissolved oxygen. Taken together, this work shows how the evolution of a new level of biological individuality can rapidly drive adaptive diversification and the expansion of a nascent multicellular niche, one of the most historically-impactful emergent properties of this evolutionary transition.

ICSI cycle outcomes in oligozoospermia.

AIM: The aim of this study was to evaluate the sole effect of sperm concentration on fertilization, embryo quality and pregnancy rates in patients undergoing ICSI cycles. MATERIALS AND METHODS: 560 ICSI cycles performed for male factor infertility were divided into four groups according to sperm concentration retrospectively. Group 1 consisted of 86 couples whose sperm concentration was less than 1x10(6), group 2 consisted of 169 couples whose sperm concentration ranged between 1x10(6) and 5x10(6), group 3 consisted of 95 couples whose sperm concentration ranged between 5x10(6) and 10x10(6) and group 4 consisted of 210 couples whose sperm concentration ranged between 10x10(6) and 20x10(6). RESULTS: Fertilization rate was significantly lower in the first three groups compared to the last group (p<0.05). The first three groups were comparable with each other. There were no differences according to ovarian response to stimulation, embryo quality and clinical pregnancy rates between the four groups. CONCLUSION: Lower sperm concentration has detrimental effects on the outcomes of ICSI cycles. This situation is more evident in men with severe and extremely severe oligozoospermia.