Morphology Of Gametes Research Articles

Analysis of the morphology of Sus scrofa domesticus oocyte-cumulus complexes exposed to low and ultra-low temperatures

Relevance. The priority task of reproductive technologies in animal husbandry is the development of effective storage protocols for female gametes. One way to preserve gametes is vitrification, which reduces damage to intracellular organelles by increasing viscosity upon cooling and minimizing crystallization.Methods. Various additives to cryoprotectants are used for optimization. In our work, titanium tetrapolyethylene glycolate was used in a 10-fold molar excess of polyethylene glycol (TTPEG*10PEG), the nature of the effect of which on cells was studied during short-term storage at low (5 °С) and ultra-low temperatures (-196 °С).The purpose of the study is a comprehensive analysis of the morphology of gametes and somatic cells (cumulus) of ovarian follicles of pigs after exposure to low and ultra-low temperatures (vitrification) when included in the TTPEG*10PEG low-temperature storage and vitrification protocol.Results. Exposure to TTPEG*10PEG at 5 °С caused an increase in the level of oocytes with subsequent morphological degenerations in points with control (from 13% to 5%, р = 0.005). After vitrification with TTPEG*10PEG: the level of gametes with low cumulus cells expansion increased to 35% in terms of the proportion of control gametes (23%); the proportion of denudated gametes was reduced to 50% compared to the control 65% (р < 0.05); the level of morphologically degenerated gametes corresponded to that of native oocytes (8% each) and was lower than in the control (17%), р < 0.005. The obtained data indicate the protective and cryoprotective effects of TTPEG*10PEG at a concentration of 2%, which suggests the possibility of its use in the technology of intraovarian vitrification of female reproductive cells.

Research Progress in the Establishment of Sterile Hosts and Their Usage in Conservation of Poultry Genetic Resources

Many local chicken breeds are rapidly declining and even facing extinction due to a variety of factors such as indiscriminate crossbreeding, climate fluctuations, epidemic outbreak, and environmental changes. Developing effective preservation strategies is important to address this situation. The special reproductive characteristics and gamete morphology of chickens pose challenges for preserving genetic heritage through the cryopreservation of genetic materials. Currently, gonad and primordial germ-cell cryopreservation and transplantation are the most promising approaches, especially for the genetic information in the W chromosome of female birds. The study of establishing sterile recipients is crucial for increasing the efficiency of the colonization of transplanted donor tissues and cells. Several classical methods, including ovariectomy and testectomy, busulfan, and irradiation, have been employed to deplete endogenous germ cells in recipient males before transplantation. These methods rely on the toxicity of chemical reagents and physical stimulation to kill germ cells. Recent advances in gene-editing technology have introduced sterile hosts via the knocking out of genes relevant to germ cells’ development. This review explores state-of-the-art technologies for preparing infertile avian recipients (mainly chickens) and aims to provide guidance for the conservation of poultry genetic material and breed restoration.

P-357 Exposure to bleomycin in vitro reduces biomarkers of human male gamete competence

Abstract Study question Does male human sperm exposure to bleomycin in vitro affect their aptitude to breed? Summary answer Bleomycin, an antitumor antibiotic, adversely impacts human male gamete morphology and functionality, thus potentially compromising male fertility. What is known already Bleomycin is a chemotherapeutic agent used to treat a number of tumors that affect males of reproductive age. Hitherto, its effect on human male reproductive capacity alone has not been previously shown. The little information available on this subject relates to in vivo animal studies and supports the feasibility of this study. Study design, size, duration Between November 2022 and June 2023, individuals of reproductive age were enrolled in this study and had their clinical semen analyzed. The remaining ejaculate was supplied by 45 participants with sperm concentration above the World Health Organization (WHO) threshold for scientific purposes. Sperm were isolated from seminal plasma in the ejaculate of each individual, diluted to a concentration of 16 X 106 sz/mL (raw). Participants/materials, setting, methods In vitro incubation was performed in sperm preparation medium (SPM; control) or bleomycin (100 µg/mL; exposed) augmented for two hours at 37oC and 5% CO2. The results of exposed group were compared to raw and control. To evaluate the competence of human sperm, markers such as acrosome and DNA integrity, mitochondrial membrane potential, sperm motility, vitality, and oxidative stress were evaluated. Ultrastructural data from transmission electron microscopy was also obtained and correlated with functional experiments. Main results and the role of chance The participants were all of reproductive age (median age of 36 years old). The raw sperm parameters fulfilled the normozoospermia threshold set by the WHO, 2021. Prior to the current trial, none of the participants had been diagnosed with cancer or had received chemotherapy, radiation therapy, or both. Bleomycin exposure for two hours in vitro significantly (P < 0.001) reduced sperm motility, vitality, and chromatin condensation as compared to raw and control sperm. Moreover, bleomycin significantly (P < 0.001) increased the percentage of sperm with DNA fragmentation (sDNAfrag) and low mitochondrial membrane potential (MMP). Broad strands were significantly (P < 0.001) attained by bleomycin-induced breaks in the sperm DNA (Head staining pattern), which were succeeded by histone-rich areas (PAR-post-acrossomic region staining pattern). Additionally, bleomycin significantly (P < 0.05) delayed the acrossomic response, but had no significantly influence on the generation of extracellular and intracellular reactive oxygen species or in its reconstitution. Modifications in ultrastructural morphology caused by bleomycin corroborate the results obtained by functional tests. Limitations, reasons for caution Bleomycin impact on male fertility competence in vivo remains crucial. Increased sample sizes, including prepubertal subjects, are needed to pinpoint the precise bleomycin’s mechanism to cause oxidative stress, apoptosis, and sDNAfrag. Long-term implications on fertility and reproductive health, besides methods to lessen or offset bleomycin’s effects, should also be pursued. Wider implications of the findings Bleomycin adversely affects male gamete competence in humans. Along with its accompanying lung toxicity, healthcare practitioners should actively monitor and further investigate bleomycin’s gonadotoxicity in males. It is advised that all cancer patients undergoing chemotherapy treatments that contain bleomycin be provided with a fertility preservation plan in the meantime. Trial registration number not applicable

Inhibition of Autophagy in Heat-Stressed Sperm of Adult Mice: A Possible Role of Catsper1, 2 Channel Proteins.

Various phenomena guarantee gamete maturation and formation at all stages of evolution, one of which is autophagy playing a critical role in the final morphology of gametes, particularly sperms. Autophagy is influenced by oxidative stress, disturbances of calcium homeostasis, and hyperthermia conditions. The current study aimed to assess the autophagy-related proteins along with the activity of sperm calcium channel (CatSper) proteins following the induction of heat stress (HS). The study sample includes two groups of adult mice: sham and HS groups. In the HS group, the right testis was transferred to the abdominal cavity for 120 hours and then returned to the scrotum where it remained for 7 days. After 7 days, the testis and epididymis were removed to conduct real-time, immunohistochemical studies, sperm parameter evaluation, and seminiferous tubule assessment. In this study, the expression and distribution of autophagy proteins were measured. Plus, CatSper1 and CatSper2 were evaluated as proteins of calcium channels. The results of the present study demonstrated that the expression intensity of autophagy indices in seminiferous tubules decreased significantly after HS induction, which was associated with a decrease in the distribution of CatSper proteins in the sperms. HS led to morphological changes in sperm, reduced motility and viability of sperm, and decreased spermatogenesis indices. In this study, following heat stress, the decrease in CatSper protein distribution may lead to the structural disorder of CatSper channels, which could strongly affect autophagic activity. Also, disruption of spermatogenesis and sperm parameters may be the consequence of decreased autophagy activity.

Особенности функциональной активности липидома в ооцитах Sus scrofa domesticus при интраовариальной витрификации

Abstract. The creation of a cryobank of reproductive cells and tissues opens up the possibility of intensifying the introduction of innovative cellular reproductive technologies into the practice of husbandry, biomedicine, and veterinary medicine. The aim of the study was to evaluate the effects of silicon dimethylglycerolate (SDMG) on the morphology of gametes and lipidome of porcine oocytes after intraovarian vitrification (IOV). Methods. Fragments (15 × 20 mm) of porcine ovaries were subjected to vitrification, which were exposed to cryoprotective agents (CPA1 and CPA2) for 25 minutes and 15 minutes. Composition: CPA1: 7.5 % ethylene glycol (EG), 7.5 % dimethyl sulfoxide (DMSO), 65 % PBS, with 2M bovine serum albumin (BSA) and CPA2 – 2.0% EG, 20 % DMSO, 60 % PBS, 1M BSA, 0.5 mol/l sucrose. The effectiveness of using SDMG at the studied concentrations on the cryopreservation of bio objects was assessed by: the morphology of gametes and indicators of the functional activity of the lipidome (morphology, localization and fluorescence intensity of lipid droplets visualized with Nile Red vital dye) in oocytes. Results. 0.2 % SDMG does not induce apoptotic processes in granulosa cells, reduces the level of naked cells. Addition of 2 % SDMG into the composition of cryoprotective media, the proportion of gametes with signs of morphological degeneration decreases (from 31 % to 13 %, P < 0.001). SDMG contributes to an increase in the level of gametes with positive indicators of the functioning of lipid droplets: the proportion of gametes with diffuse localization increases (from 58 % to 83 %, P < 0.001); the level of cells with low fluorescence intensity of the Nile red/lipid droplets complex (from 16 % to 29 %, P < 0.05) and the proportion of gametes with lipid granules (47 % vs. 68 %, P < 0.005) increased. Scientific novelty. For the first time, the effects of SDMG on the morphology of female gametes, apoptotic processes in the chromatin of granulosa cells and the functional activity of the lipidome of porcine oocytes under the influence of ultralow temperatures at IOV were identified. The media for IOV of oocyte-cumulus complexes were modernized with the addition of 0.2 % or 2 % SDMG.

Impact of gamete health on fertilization and embryo development

A genetically and functionally proficient gamete is essential for normal fertilization and embryonic development. Any change in gamete health affects fertilization and subsequent events, including embryonic development, implantation, and successful pregnancy. This present review focuses on the role of gamete health on fertilization and embryo development. Several conventional and advanced methods are used to evaluate the morphology and functions of gametes. The abnormal spermatozoa adversely affect fertilization events, which results in reduced cleavage/blastocyst/ implantation and pregnancy rate during assisted reproductive techniques. Poor oocyte quality is also one of the reasons for infertility, although the oocyte has an innate capacity to repair a certain amount of abnormality of both oocyte and spermatozoa. Therefore, oocyte health carries more responsibilities during fertilization events. The gamete, either spermatozoa or oocyte, should have optimum morphological and functional health to fertilize and develop a competent embryo successfully. Thus, it is of prime importance to consider the gamete health parameters while dealing with infertility.

Three new species of shell-boring Dipolydora (Annelida: Spionidae: Polydorini) from the South China Sea and the Gulf of Thailand, Vietnam, with comments on the modified spines in posterior notopodia and sperm morphology in polydorins.

Three species of tube-dwelling polydorins (Annelida: Spionidae: Polydorini) from China have been reported for the South China Sea to date. Three new species of shell-boring Dipolydora are described and illustrated in the present study based on new material collected in the Gulf of Thailand and Nha Trang Bay, Vietnam. Dipolydora echinata sp. nov. and D. spinosa sp. nov. have awl-like spines in addition to capillary chaetae in the posterior notopodia, and cup-shaped pygidia with only dorsal incision. Dipolydora vietnamita sp. nov. has only capillary chaetae in the posterior notopodia, and three-lobed pygidium with one ventral lobe and two smaller dorsal lobes. Gradual transformation of capillary chaetae along the body and the morphology of modified spines in the posterior notopodia of polydorin spionids are briefly discussed. Gamete morphology is considered an underestimated trait used for the identification of spionids.

P-186 Volumetric imaging provides insight into the 3D ultrastructural organization of maturing human oocytes

Abstract Study question Is volume electron microscopy suitable for high-resolution oocyte imaging in three dimensions (3D)? Summary answer Focused Ion Bean Scanning Electron Microscopy (FIB-SEM) allows 3D visualization and quantitative analysis of ultrastructural features in the large human oocyte volume. What is known already Transmission electron microscopy (TEM) has been traditionally used to study the fine morphology of female gametes. However, 2D micrographs provide only limited information about the topology of subcellular structures. Volumetric studies are needed to elucidate the 3D organization of complex oocyte cytoplasm. Study design, size, duration An academic study conducted in collaboration with an IVF clinic. Advanced 3D - ultrastructural analysis was performed on 9 human oocytes representing 3 stages of maturation (3 germinal vesicle (GV), 3 metaphase I (MI), 3 metaphase (MII) oocytes) collected from February 2018 to November 2019. Participants/materials, setting, methods Spare IVF oocytes, donated by 9 young egg donors (22-29 years), were cultured in vitro until they reached a defined developmental stage. Each oocytés meiotic status was determined based on the presence/absence of a prophase nucleus, a polar body, and a non-invasively detectable MI/MII spindle. Following standard TEM preparation, individual oocyte-containing resin blocks were coated with a thin carbon layer[JJ1] , mounted on the microscope stage, and subjected to FIB-SEM imaging. Main results and the role of chance FIB-SEM tomography provided an unprecedented view of the oocytés intracellular morphology. Automated serial scanning of newly exposed sample surface generated large stacks (120-1294 slices) of ultrastructural images with 40-100 nm z-resolution. The tomographic reconstruction of acquired datasets revealed the spatial arrangement of inner oocyteś structures. The imaging protocol was optimized to ensure sufficient image detail, minimal noisiness, and time-efficiency of large volume scanning. Comparison of oocytes fixed at different maturation stages confirmed previous TEM observations that the cortical region of GV oocytes is deprived of membraneous structures, and major organelle redistribution occurs during the MI phase. Semi-automated 3D image segmentation was employed to distinguish distinct organelle populations and evaluated their abundance. Subsequent quantitative analysis of volumetric data showed that the mitochondrion occupies ∼ 5.27 % of MII oocyte volume. In conclusion, the volumetric imaging, followed by advanced image analysis, maximizes the amount of morphological data obtained from a single human oocyte. Limitations, reasons for caution The imaging procedure was pioneered on a small number of hormonally-primed oocytes, which failed to complete development in vivo. There is a trade-off between resolution, the size of the 3D volume, and imaging time. Block-face ion milling during FIB-SEM imaging inevitably results in sample destruction. Wider implications of the findings This proof-of-concept study opens up new possibilities to study the delicate architecture of scarce human oocytes. Enhancing our knowledge of the spatial organization of ooplasm is pivotal for developing experimental and therapeutical strategies involving oocyte microsurgery. Trial registration number not applicable

P–186 Volumetric imaging provides insight into the 3D ultrastructural organization of maturing human oocytes

Abstract Study question Is volume electron microscopy suitable for high-resolution oocyte imaging in three dimensions (3D)? Summary answer Focused Ion Bean Scanning Electron Microscopy (FIB-SEM) allows 3D visualization and quantitative analysis of ultrastructural features in the large human oocyte volume. What is known already Transmission electron microscopy (TEM) has been traditionally used to study the fine morphology of female gametes. However, 2D micrographs provide only limited information about the topology of subcellular structures. Volumetric studies are needed to elucidate the 3D organization of complex oocyte cytoplasm. Study design, size, duration An academic study conducted in collaboration with an IVF clinic. Advanced 3D - ultrastructural analysis was performed on 9 human oocytes representing 3 stages of maturation (3 germinal vesicle (GV), 3 metaphase I (MI), 3 metaphase (MII) oocytes) collected from February 2018 to November 2019. Participants/materials, setting, methods Spare IVF oocytes, donated by 9 young egg donors (22–29 years), were cultured in vitro until they reached a defined developmental stage. Each oocytés meiotic status was determined based on the presence/absence of a prophase nucleus, a polar body, and a non-invasively detectable MI/MII spindle. Following standard TEM preparation, individual oocyte-containing resin blocks were coated with a thin carbon layer[JJ1] , mounted on the microscope stage, and subjected to FIB-SEM imaging. Main results and the role of chance FIB-SEM tomography provided an unprecedented view of the oocytés intracellular morphology. Automated serial scanning of newly exposed sample surface generated large stacks (120–1294 slices) of ultrastructural images with 40–100 nm z-resolution. The tomographic reconstruction of acquired datasets revealed the spatial arrangement of inner oocyteś structures. The imaging protocol was optimized to ensure sufficient image detail, minimal noisiness, and time-efficiency of large volume scanning. Comparison of oocytes fixed at different maturation stages confirmed previous TEM observations that the cortical region of GV oocytes is deprived of membraneous structures, and major organelle redistribution occurs during the MI phase. Semi-automated 3D image segmentation was employed to distinguish distinct organelle populations and evaluated their abundance. Subsequent quantitative analysis of volumetric data showed that the mitochondrion occupies ∼ 5.27% of MII oocyte volume. In conclusion, the volumetric imaging, followed by advanced image analysis, maximizes the amount of morphological data obtained from a single human oocyte. Limitations, reasons for caution The imaging procedure was pioneered on a small number of hormonally-primed oocytes, which failed to complete development in vivo. There is a trade-off between resolution, the size of the 3D volume, and imaging time. Block-face ion milling during FIB-SEM imaging inevitably results in sample destruction. Wider implications of the findings: This proof-of-concept study opens up new possibilities to study the delicate architecture of scarce human oocytes. Enhancing our knowledge of the spatial organization of ooplasm is pivotal for developing experimental and therapeutical strategies involving oocyte microsurgery. Trial registration number Not applicable

Scanning Probe Microscopies: Imaging and Biomechanics in Reproductive Medicine Research.

Basic and translational research in reproductive medicine can provide new insights with the application of scanning probe microscopies, such as atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). These microscopies, which provide images with spatial resolution well beyond the optical resolution limit, enable users to achieve detailed descriptions of cell topography, inner cellular structure organization, and arrangements of single or cluster membrane proteins. A peculiar characteristic of AFM operating in force spectroscopy mode is its inherent ability to measure the interaction forces between single proteins or cells, and to quantify the mechanical properties (i.e., elasticity, viscoelasticity, and viscosity) of cells and tissues. The knowledge of the cell ultrastructure, the macromolecule organization, the protein dynamics, the investigation of biological interaction forces, and the quantification of biomechanical features can be essential clues for identifying the molecular mechanisms that govern responses in living cells. This review highlights the main findings achieved by the use of AFM and SNOM in assisted reproductive research, such as the description of gamete morphology; the quantification of mechanical properties of gametes; the role of forces in embryo development; the significance of investigating single-molecule interaction forces; the characterization of disorders of the reproductive system; and the visualization of molecular organization. New perspectives of analysis opened up by applying these techniques and the translational impacts on reproductive medicine are discussed.

Cytoplasmic inheritance of mitochondria and chloroplasts in the anisogamous brown alga Mutimo cylindricus (Phaeophyceae).

Based on the morphology of gametes, sexual reproduction in brown algae is usually classified into three types: isogamy, anisogamy, and oogamy. In isogamy, chloroplasts and chloroplast DNA (chlDNA) in the sporophyte cells are inherited biparentally, while mitochondria (or mitochondrial DNA, mtDNA) is inherited maternally. In oogamy, chloroplasts and mitochondria are inherited maternally. However, the patterns of mitochondrial and chloroplast inheritance in anisogamy have not been clarified. Here, we examined derivation of mtDNA and chlDNA in the zygotes through strain-specific PCR analysis using primers based on single nucleotide polymorphism in the anisogamous brown alga Mutimo cylindricus. In 20-day-old sporophytes after fertilization, mtDNA and chlDNA derived from female gametes were detected, thus confirming the maternal inheritance of both organelles. Additionally, the behavior of mitochondria and chloroplasts in the zygotes was analyzed by examining the consecutive serial sections using transmission electron microscopy. Male mitochondria were isolated or compartmentalized by a double-membrane and then completely digested into a multivesicular structure 2h after fertilization. Meanwhile, male chloroplasts with eyespots were observed even in 4-day-old, seven-celled sporophytes. The final fate of male chloroplasts could not be traced. Organelle DNA copy number was also examined in female and male gametes. The DNA copy number per chloroplast and mitochondria in male gametes was lower compared with female organelles. The degree of difference is bigger in mtDNA. Thus, changes in different morphology and DNA amount indicate that maternal inheritance of mitochondria and chloroplasts in this species may be based on different processes and timing after fertilization.

The Sperm Ultrastructure and Some Reproductive Characteristics of the Chemosymbiotic Bivalve Calyptogena pacifica Dall, 1891 (Vesicomyidae: Pliocardiinae)

Pliocardiines (Bivalvia: Vesicomyidae: Pliocardiinae) are a chemosymbiotrophic group of bivalve mollusks that are obligate for reducing environments. These mollusks house endosymbiotic thioautotrophic bacteria in their gills, which provide nutrition for the host. The ultrastructure of spermatozoa and the state of the gonads in the pliocardiine bivalve Calyptogena pacifica in June 2016 were studied. Material was collected in the Bering Sea on the slopes of the Piip’s Volcano at a depth of 466 m. The condition of the gonads indicated a pre-spawning state. Active processes of spermatogenesis and oogenesis were noted in the gonads. The mature spermatozoon has an elongated bullet-shaped head with an average length of 4 ± 0.2 μm from the tip of the acrosome to the base of the mid-piece. The mid-piece was formed by a complex of four spherical mitochondria with a diameter of approximately 0.7 μm. An electron dense material of a lipid nature was observed in the distal region of the mid-piece of the sperm. C.pacifica mature eggs are approximately 200 μm in diameter. The results are discussed in the context of the available data on the morphology of pliocardiine gametes.

Early signs of toxicity in testes and sperm of rats exposed to low cadmium doses.

The cadmium (Cd) concentration in the environment has increased as a consequence of anthropogenic activity. The objective of this study was to determine early signs of Cd toxicity in testes and sperm as possible biomarkers. The dose orally administered to Wistar rats was within the range where chronic toxicity can appear. At the light microscopic level, gonads presented preserved cytoarchitecture throughout treatment; however, after the second month, transmission electron microscopy (TEM) revealed disruption of the blood-testis barrier. The study of sperm with light microscopy showed defects in gamete morphology after 2 months of treatment. Another parameter that revealed alteration was sperm motility after 3 months of treatment. TEM was used to analyze the flagellum, which in the midpiece showed aberrant mitochondria and displacement of outer dense fibers in relation to the central axoneme after 2 months. The data obtained were associated with Cd concentration in the testes, an increase in its levels being observed in a time-dependent manner. The results provided in this study demonstrated that early signs of Cd toxicity were observed in gonads and gametes during the second month of the treatment, generating morphological and functional alterations in the sperm that could lead to infertility.

Gamete activation: basic knowledge and clinical applications.

BackgroundThe first clues to the process of gamete activation date back to nearly 60 years ago. The mutual activation of gametes is a crucial event during fertilization. In the testis and ovaries, spermatozoa and oocytes are in a state of meiotic and metabolic quiescence and require reciprocal signals in order to undergo functional changes that lead to competence for fertilization. First, the oocyte activates sperm by triggering motility, chemoattraction, binding and the acrosome reaction, culminating with the fusion of the two plasma membranes. At the end of this cascade of events, collectively known as sperm capacitation, sperm-induced oocyte activation occurs, generating electrical, morphological and metabolic modifications in the oocyte.Objective and rationaleThe aim of this review is to provide the current state of knowledge regarding the entire process of gamete activation in selected specific animal models that have contributed to our understanding of fertilization in mammals, including humans. Here we describe in detail the reciprocal induction of the two activation processes, the molecules involved and the mechanisms of cell interaction and signal transduction that ultimately result in successful embryo development and creation of a new individual.Search methodsWe carried out a literature survey with no restrictions on publication date (from the early 1950s to March 2016) using PubMed/Medline, Google Scholar and Web of Knowledge by utilizing common keywords applied in the field of fertilization and embryo development. We also screened the complete list of references published in the most recent research articles and relevant reviews published in English (both animal and human studies) on the topics investigated.OutcomesLiterature on the principal animal models demonstrates that gamete activation is a pre-requisite for successful fertilization, and is a process common to all species studied to date. We provide a detailed description of the dramatic changes in gamete morphology and behavior, the regulatory molecules triggering gamete activation and the intracellular ions and second messengers involved in active metabolic pathways in different species. Recent scientific advances suggest that artificial gamete activation may represent a novel technique to improve human IVF outcomes, but this approach requires caution.Wider implicationsAlthough controversial, manipulation of gamete activation represents a promising tool for ameliorating the fertilization rate in assisted reproductive technologies. A better knowledge of mechanisms that transform the quiescent oocyte into a pluripotent cell may also provide new insights for the clinical use of stem cells.

Morphology of gametes, post-fertilization events and the effect of temperature on the embryonic development of Astyanax altiparanae (Teleostei, Characidae).

The aim of this study was to describe the morphology of gametes, post-fertilization events and subsequent temperature effects on the early developmental stages of the neotropical species Astyanax altiparanae. The sperm of this species presents a typical morphology of teleost sperm with a spherical head (diameter = 1.88 µm), midpiece (diameter = 0.75 µm) and a single flagellum (length = 18.67 µm). The extrusion of the second polar body and fusion of male and female pronucleus were reported for the first time in this species. Additionally, we observed the formation of the fertilization cone, which prevents polyspermic fertilization. Developmental stages at 22°C, 26°C and 30°C gave rise to fertilization rates at 91.12, 91.42 and 93.04% respectively. Hatching occurred at 25 hpf at 22°C, 16 hpf at 26°C and 11 hpf at 30°C and the hatching rates were 61.78%, 62.90% and 59.45%, respectively. At 22°C, the second polar body was extruded at ≈6 mpf and the male and female pronucleus fused at ≈10 mpf. This fundamental information is important for the field and opens up new possibilities in fish biotechnology, including micromanipulation and chromosome-set manipulation.

Is gamete morphology involved in hybridization in oysters?

Some pairs of oyster species in the genus Crassostrea can produce viable hybrids, and heterospecific fertilization may be symmetric, asymmetric, or very low. For example, with C. angulata and C. gigas, fertilization is equally successful whether the mature oocytes come from the first or the second species. Fertilization is asymmetric between C. ariakensis and C. virginica, i.e., it is higher when C. ariakensis is the source of the oocytes. Fertilization success is low between C. ariakensis and C. gigas. These differences probably relate chiefly to molecular mechanisms of gamete recognition, but the present study examines whether the size and certain aspects of gamete morphology may also play a role. Individuals of four species of the genus Crassostrea (Ostreidae: Bivalvia), collected from different geographic regions between 2006 and 2011, C. angulata (Penghu Island, Taiwan Strait), C. ariakensis (Nha Trang Bay, South China Sea), C. gigas (Peter the Great Bay, Sea of Japan), and C. virginica (Galveston Bay, Gulf of Mexico), were examined for conspecific relationships between the thickness of the vitelline envelope in mature oocytes and the size of the acrosome or subacrosomal spaces in spermatozoa. Thicker vitelline envelopes corresponded with bigger acrosomes and subacrosomal spaces in three of the four species. The exception was C. gigas, which has the thickest vitelline envelope, but the lytic compartments in its spermatozoa are not the largest. Moreover, sizes of acrosome, subacrosomal space, and vitelline envelope are similar between the species with symmetric heterospecific fertilization, while difference in sizes of these structures increases the possibility of asymmetric cross-fertilization or decreased fertilization rate.

Effects of Cadmium and Zinc on the Gamete Viability, Fertilization, and Embryonic Development of Tripneustes gratilla (Linnaeus).

Heavy metals are frequently reported for their mutagenic and teratogenic effects on benthic organisms. Thus, this study aimed to determine the toxicity of cadmium (Cd) and zinc (Zn) in the gametes of T. gratilla and to compare its fertilization and embryonic development under the highest nongametotoxic concentrations of these heavy metals. Gamete viability of T. gratilla under CdCl2 and ZnSO4 treatments was assayed through resazurin reduction test (RRT) and was confirmed through gamete morphology assay. ZnSO4 was more toxic to T. gratilla gametes than CdCl2 and egg cells were more sensitive to both than the sperm cells. Higher concentrations of CdCl2 and ZnSO4 induced gamete apoptosis and necrosis while highest nongametotoxic concentrations were determined at 1 × 10−3 M and 1 × 10−4 M, respectively, and were used in an in vitro fertilization and embryonic development experiment. ZnSO4 treatment inhibited fertilization more than CdCl2 and yielded more deformed embryos, while both induced abnormalities and hindered further embryonic development. This study gives the first report on the specific concentrations of Cd and Zn that are toxic to T. gratilla gametes and has confirmed the teratogenic effects of these heavy metals.

Pheromone signaling during sexual reproduction in algae

Algae are found in all aquatic and many terrestrial habitats. They are dominant in phytoplankton and biofilms thereby contributing massively to global primary production. Since algae comprise photosynthetic representatives of the various protoctist groups their physiology and appearance is highly diverse. This diversity is also mirrored in their characteristic life cycles that exhibit various facets of ploidy and duration of the asexual phase as well as gamete morphology. Nevertheless, sexual reproduction in unicellular and colonial algae usually has as common motive that two specialized, sexually compatible haploid gametes establish physical contact and fuse. To guarantee mating success, processes during sexual reproduction are highly synchronized and regulated. This review focuses on sex pheromones of algae that play a key role in these processes. Especially, the diversity of sexual strategies as well as of the compounds involved are the focus of this contribution. Discoveries connected to algal pheromone chemistry shed light on the role of key evolutionary processes, including endosymbiotic events and lateral gene transfer, speciation and adaptation at all phylogenetic levels. But progress in this field might also in the future provide valid tools for the manipulation of aquaculture and environmental processes.

Trioecy, a unique breeding strategy in the sea anemone Aiptasia diaphana and its association with sex steroids.

Reproductive development of anthozoans reveals wide range of breeding strategies. Here, we report the occurrence of trioecy in the sea anemone Aiptasia diaphana (co-occurrence of males, females, and hermaphrodites), which so far was well documented only in plants. Age-homogeneous populations were obtained from pedal lacerates (asexual propagules) and cultured under control conditions. Careful documentation of growth, gamete morphology, and vertebrate-like steroid (i.e., progesterone, testosterone, and estradiol) levels were carried out over a 9-wk period between 4 and 12 wk postlaceration (wpl). First phenotypic signs of gametes development were observed in 6-wk-old anemones, pointing to the differentiation of males and hermaphrodites. While the males exhibited cellular progression of spermatogenesis, the hermaphrodites underwent a process of sex allocation, giving rise to male, female, and hermaphrodite phenotypes. Testosterone levels were relatively high prior to gamete appearance (4 wpl) and later on during gamete maturation (10 wpl). Conversely, estradiol levels steadily increased from 6 to 10 wpl, reaching their peak concomitant with oocyte maturation. Interestingly, increased oocyte atresia incidences were recorded during 9-12 wpl, coinciding with declining levels of steroid hormones. These results point to a strong similarity between the activity of sex steroids in vertebrates and that of vertebrate-like sex steroids on critical stages of A. diaphana's sexual differentiation and gametogenic cycle. The reproductive characteristics of A. diaphana make this anthozoan an important model species for the study of evolutionary drivers and processes underlying sexual development.

Characterization of gametes in two phyllostomid bat species: Artibeus jamaicensis and Sturnira lilium

Morphology of gametes is used to understand the physiological processes in reproduction among domestic and wild animals. These gametes are used in assisted reproductive technology (ART) and conservation programs. In the case of Artibeus jamaicensis and Sturnira lilium, few studies have been conducted related to these issues. The aim of this study was to describe the structure of spermatozoa, semen characteristics and also the morphology and quality of cumulus oocyte complexes (COC) of A. jamaicensis and S. lilium. Semen characteristics were: A. jamaicensis had a sperm concentration of 4.26×106sperm/ml, progressive motility of 34.55%; viability of 73.23%; head, tail and mid-piece abnormalities of 12.50%. Head length was 6.26μm, mid-piece 18.61μm and tail 70.92μm. S. lilium, had a sperm concentration of 5.15×106sperm/ml, progressive motility of 60.00%, viability of 83.82%; abnormalities in head, tail and mid-piece of 13.77%. Head length was 7.01μm, mid-piece 20.33μm and tail 70.50μm. On average 12.8 of right ovarian oocytes and 9.9 of left ovarian oocytes of A. jamaicensis were recovered. For S. lilium on average 10.7 oocytes from the right ovary and 10.9 oocytes from the left ovary were recovered, ranging in quality from excellent to poor. Sperm morphology and quality of COC were similar to those for other domestic and wild animals. Bat gametes can be used for the study of reproductive biology, in conservation programs and assisted reproductive technology (ART) among domestic and wild animals.