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Population outbreaks of the coral-eating crown-of-thorns starfish (CoTS) have resulted in extensive coral mortality on reefs in the Indo-Pacific region and is considered one of the major contributors of significant declines in coral cover in Australia's Great Barrier Reef (GBR). Effective management of CoTS outbreaks rely on improved understanding of the drivers of individual and population-level differences in reproductive patterns, particularly those factors that may contribute to step-changes in reproductive success, such as the timing and synchronicity of spawning. This study investigated gametogenesis and spawning patterns in a persistent population of CoTS at one reef within the putative initiation zone where outbreaks appear to start in the GBR. We examined variation in the progression of gametogenesis and spawning patterns over two distinct spawning seasons (2013-2014, 2014-2015), using a variety of methods: macroscopic examination of gonads, assessment of monthly changes in the gonadosomatic index, analysis of histological sections of ovaries and testes, and comparison of the size-frequency distribution of oocytes. These methods yielded consistent results, which revealed striking variation in the timing of maturation and gamete release between two summer spawning seasons, possibly depending on local environmental conditions. The optimal temperature for gametogenesis and spawning occurred when seawater temperature exceeded 28 â. Gradual increases in temperature (to > 28 â) over spawning months in 2013-2014 caused 'batch/dribble' spawning, while abrupt increases in temperature in 2014-2015 caused synchronous 'all-at-once' spawning. During more rapid warming events in the typical summer spawning period, CoTS may exhibit greater synchronicity in their reproductive capacity, which may help seed outbreaks. This work advances our understanding of the mechanisms surrounding periodic fluctuations in CoTS densities and improves predictions on how this corallivorous predator will respond to environmental perturbations due to climate change., Author(s): Ciemon Frank Caballes [sup.1] , Maria Byrne [sup.2] , Vanessa Messmer [sup.1] , Morgan S. Pratchett [sup.1] Author Affiliations: (1) grid.1011.1, 0000 0004 0474 1797, ARC Centre of Excellence [...]

Sexual reproduction of apicomplexan parasites in haematophagous arthropods requires that intracellular sexual stages of these protozoa escape vertebrate erythrocytes in the blood meal. Although cues that signal sexual stages of the human malaria parasite (Plasmodium falciparum Welch, 1897) to emerge from erythrocytes are well documented, such signals are poorly known for other blood-dwelling Apicomplexa. The objective of this comparative study was to investigate conditions required to induce in vitro emergence of sexual stages of Hepatozoon clamatae (Stebbins, 1905) from frog erythrocytes. Blood was drawn from Green Frogs (Rana clamitans Latreille in Sonnini de Manoncourt and Latreille, 1801 = Lithobates clamitans clamitans (Latreille in Sonnini de Manoncourt and Latreille, 1801)) infected with H. clamatae and treated with solutions of various concentrations of saline, pH, and xanthurenic acid at different temperatures. Hypertonic saline solutions of 200 and 222 mmol/L at pH 7.4 and 7.7 elicited emergence of nearly 100% of gamonts from frog erythrocytes, but at pH 8.0 resulted in decreased emergence. Solutions containing 1, 10, and 100 [xmol/L xanthurenic acid increased gamont emergence at saline concentrations of 156, 178, and 244 mmol/L, but decreased emergence at 200 and 222 mmol/L. Gamont emergence increased as incubation temperatures increased from 18 to 26 °C. These results suggest that conditions necessary for emergence of sexual stages of bloodstream Apicomplexa from erythrocytes vary among genera. Key words: Hepatozoon clamatae, Green Frog, Rana clamitans, gamont, mosquito, Culex territans, xanthurenic acid, malaria parasites, Plasmodium species, blood. La reproduction sexuee de parasites apicomplexes dans des arthropodes hematophages necessite que les stades sexues intracellulaires de ces protozoaires s'echappent des erythrocytes vertebres dans le repas de sang. Bien que des signaux qui indiquent aux stades sexues du parasite du paludisme humain (Plasmodium falciparum Welch, 1897) d'emerger des erythrocytes soient bien documentes, ce type de signaux demeure meconnu chez d'autres apicomplexes du sang. L'objectif de la presente etude comparative etait d'examiner les conditions requises pour provoquer l'emergence in vitro de stades sexues d'Hepatozoon clamatae (Stebbins, 1905) d'erythrocytes de grenouille. Du sang a ete preleve de grenouilles vertes (Rana clamitans Latreille in Sonnini de Manoncourt and Latreille, 1801 = Lithobates clamitans clamitans (Latreille in Sonnini de Manoncourt and Latreille, 1801)) infectees au H. clamatae puis traite avec des solutions de differentes concentrations de sel et d'acide xanthurenique a differents pH et a differentes temperatures. Des solutions salines hypertoniques de 200 et 222 mmol/L a des pH de 7,4 et 7,7 ont provoque l'emergence de pres de 100 % des gamontes des erythrocytes de grenouille, mais un pH de 8,0 s'est traduit pas une reduction du taux d'emergence. Des solutions contenant 1, 10 et 100 [xmol/L d'acide xanthurenique ont entrame une emergence accrue de gamontes pour des concentrations salines de 156, 178 et 244 mmol/L, mais une emergence reduite a 200 et 222 mmol/L. L'emergence de gamontes augmentait parallelement a l'augmentation de la temperature d'incubation de 18 a 26 °C. Ces resultats suggerent que les conditions necessaires a l'emergence de stades sexues d'apicomplexes du sang en dehors d'erythrocytes varient selon le genre. [Traduit par la Redaction] Mots-cles: Hepatozoon clamatae, grenouille verte, Rana clamitans, gamonte, moustique, Culex territans, acide xanthurenique, parasites du paludisme, espece de Plasmodium, sang., Introduction The phylum Apicomplexa contains species of many genera that parasitise the blood cells of vertebrates and use blood-feeding arthropods or annelids as definitive hosts. For all blood-dwelling Apicomplexa, with [...]

ABSTRACT A polyclonal antibody specific to an egg protein of the Suminoe oyster, Crassostrea ariakensis, was developed to assess reproductive effort. After 2 mo of immunization, rabbit antiserum showed strong [...]

We describe the first reproductive features of a chemosynthetic mussel collected at cold seeps from the eastern Mediterranean Sea. Idas modiolaeformis (Bivalvia, Mytilidae) is a hermaphroditic species in which production of male and female gametes likely alternates, a feature regarded as an adaptation to patchy and ephemeral habitats. By using fluorescent in situ hybridization, we demonstrate that bacterial symbionts, while present within the gills, are absent within acini that enclose female gametes and male gametes. This supports the hypothesis of environmental acquisition of symbionts in chemosynthetic mytilids. Prodissoconch I (PI) is relatively small compared to prodissoconch II (PII), suggesting a planktotrophic larval stage. Diameters of the two larval shells are in the range of sizes reported for mytilids, with a PII size between that of the shallow Mytilus edulis and that of the cold-seep mussel 'Bathymodiolus' childressi., Introduction Cold seeps, hydrothermal vents, and wood- and whale falls are reducing habitats that cover small areas and are typically dynamic and distant and isolated from one another. For these [...]

ABSTRACT Spat of Pacific oysters (Crassostrea gigas) were collected from Gamakman Bay, Korea, and raised in a spat hardening facility located in the low intertidal zone of the bay for [...]

ABSTRACT The gonadal organization and cytological characteristics of gametogenesis in a population of the freshwater clam Musculium argentinum (d'Orbigny, 1835) are described. Sections of the rather small gonad demonstrate the [...]

The reproductive cycle of the cared ark Anadara notabilis and its relationship with environmental factors was evaluated every 15 days between March 2004 and February 2005 at the northern part [...]

ABSTRACT The purpose of this study was to develop an oocyte maturation scale and to retrace the development of the oocyte cohorts in razor clam populations of Solen marginatus (Bivalvia: [...]

ABSTRACT The seasonal variations in biochemical composition and reproductive activity of the venus clam Cyelina sinensis (Gmelin) from the Yellow River delta in China were investigated from April 2007 to [...]

ABSTRACT We evaluated the development of metabolic capacities, immunocompetence, and growth patterns according to sex, age, and gametogenesis stages among scallops Placopecten magellanicus from the Magdalen Islands (Quebec, Canada). Our [...]

The leading cause of infertility in men and women is quantitative and qualitative defects in human germ-cell (oocyte and sperm) development. Yet, it has not been possible to examine the [...]

The Retinoblastoma (Rb) protein is a conserved repressor of cell proliferation. In animals and plants, deregulation of Rb protein causes hyperproliferation and perturbs cell differentiation to various degrees. However, the primary developmental impact of the loss of Rb protein has remained unclear. In this study we investigated the direct consequences of Rb protein knockout in the Arabidopsis male germline using cytological and molecular markers. The Arabidopsis germ line derives from the unequal division of the microspore, producing a small germ cell and a large terminally differentiated vegetative cell. A single division of the germ cell produces the 2 sperm cells. We observed that the loss of Rb protein does not have a major impact on microspore division but causes limited hyperproliferation of the vegetative cell and, to a lesser degree, of the sperm cells. In addition, cell fate is perturbed in a fraction of Rb-defective vegetative cells. These defects are rescued by preventing cell proliferation arising from down-regulation of cyclin-dependent kinase A1. Our results indicate that hyperproliferation caused by the loss of Rb protein prevents or delays cell determination during plant male gametogenesis, providing further evidence for a direct link between fate determination and cell proliferation. male germline | pollen | cell cycle

Abstract: Four different interspecific hybrids involving three different accessions of Aegilops longissima Schweinf. & Muschl. with high grain iron and zinc content and three Triticum turgidum L. subsp. durum (Desf.) [...]

Author(s): H. Diego Folco [1]; Venkata R. Chalamcharla [1]; Tomoyasu Sugiyama [1]; Gobi Thillainadesan [1]; Martin Zofall [1]; Vanivilasini Balachandran [1]; Jothy Dhakshnamoorthy [1]; Takeshi Mizuguchi [1]; Shiv I. S. [...]

We applied independent species concepts to clarify the phylogeographic structure of the ascidian Ciona intestinalis, a powerful model system in chordate biology and for comparative genomic studies. Intensive research with this marine invertebrate is based on the assumption that natural populations globally belong to a single species. Therefore, understanding the true taxonomic classification may have implications for experimental design and data management. Phylogenies inferred from mitochondrial and nuclear DNA markers accredit the existence of two cryptic species: C. intestinalis sp. A, genetically homogeneous, distributed in the Mediterranean, northeast Atlantic, and Pacific, and C. intestinalis sp. B, geographically structured and encountered in the North Atlantic. Species-level divergence is further entailed by cross-breeding estimates. C. intestinalis A and B from allopatric populations cross-fertilize, but hybrids remain infertile because of defective gametogenesis. Although anatomy illustrates an overall interspecific similarity lacking in diagnostic features, we provide consistent tools for in-field and in-laboratory species discrimination. Finding of two cryptic taxa in C. intestinalis raises interest in a new tunicate genome as a gateway to studies in speciation and ecological adaptation of chordates. anatomy | Ciona intestinalis | cryptic species I gamete compatibility | phylogenetics

We report a cross-species expression profiling analysis of the human, mouse, and rat male meiotic transcriptional program, using enriched germ cell populations, whole gonads, and high-density oligonucleotide microarrays (GeneChips). Among 35% of the protein-coding genes present in rodent and human genomes that were found to be differentially expressed between germ cells and somatic controls, a key group of 357 conserved core loci was identified that displays highly similar meiotic and postmeiotic patterns of transcriptional induction across all three species. Genes known to be important for sexual reproduction are significantly enriched among differentially expressed core loci and a smaller group of conserved genes not detected in 17 nontesticular somatic tissues, correlating transcriptional activation and essential function in the male germ line. Some genes implicated in the etiology of cancer are found to be strongly transcribed in testis, suggesting that these genes may play unexpected roles in sexual reproduction. Expression profiling data further identified numerous conserved genes of biological and clinical interest previously unassociated with the mammalian male germ line. bioinformatics | spermatogenesis | transcriptome

In Anopheles gambiae, the vector for the most deadly malaria parasite Plasmodium falciparum, xanthurenic acid (XA) plays a key role in parasite gametogenesis and fertility. In mosquitoes, XA is produced by transamination of 3-hydroxykynurenine (3-HK), a reaction that represents the main route to prevent the accumulation of the potentially toxic 3-HK excess. Interfering with XA metabolism in A. gambiae therefore appears an attractive avenue for the development of malaria transmission-blocking drugs and insecticides. We have determined the crystal structure of A. gambiae 3-HK transaminase in its pyridoxal 5'-phosphate form and in complex with a newly synthesized competitive enzyme inhibitor. Structural inspection of the enzyme active site reveals the key molecular determinants for ligand recognition and catalysis. Major contributions toward inhibitor binding are provided by a salt bridge between the inhibitor carboxylate and Arg-356 and by a remarkable hydrogen bond network involving the anthranilic moiety of the inhibitor and backbone atoms of residues Gly-25 and Asn-44. This study may be useful for the structurebased design of specific enzyme inhibitors of potential interest as antimalarial agents. kynurenine pathway | xanthurenic acid

Chromatin-remodeling factors regulate the establishment of transcriptional programs during plant development. Although 42 genes encoding members of the SWI2/SNF2 family have been identified in Arabidopsis thaliana, imitation of switch proteins | megagametophyte | RNA interference | seed development | functional megaspore

Pollen development and reproduction requires high secretory activity in another tissues and pollen, in flowering plants. With usage of Arabidopsis as a multicellular genetic model, it is identified that loss-of-function mutations in a gene belonging to the small P(sub 5) sub family of P-type ATPases is ubiquitous in eukaryotic organisms and also, single P(sub 5) ATPase is important in pollen development and male fertility.

The present study reports the gametogenic cycle of the common octopus, Octopus vulgaris Cuvier, 1797 in the Atlantic coast of Andalusia between May 2001 and May 2002. A total of 673 specimens of total weight ranging from 30 to 3,732 g were analysed. The gonad development was defined by means of histological methods and gonadosomatic indexes. Four gametogenic stages were identified in males (I immature, II maturing, III mature, IV spawning) and in females (I immature, II maturing, III pre-spawning, IV spawning). The sex ratio obtained was not significantly different from 1:1 (P > 0.01). Mature males were found during the whole year, September being the month when the highest rate of sexually active individuals occurred (48%). In females, the gametogenic cycle commenced in December and ended in November, and spawning occurred between April and October, with two maximum peaks in August and September (48% in each). Size at sexual maturity was 850 g of total body weight for males and 1,250 g of total body weight for females. Males mature earlier than females., Introduction Octopus vulgaris Cuvier, 1797 (Cephalopoda: Octopodidae) has a world-wide distribution in tropical, subtropical, and temperate waters of the Atlantic, Indian, and Pacific oceans; this species also lives in the [...]

The present study reports the gametogenic cycle of the common octopus, Octopus vulgaris Cuvier, 1797 in the Atlantic coast of Andalusia between May 2001 and May 2002. A total of 673 specimens of total weight ranging from 30 to 3,732 g were analysed. The gonad development was defined by means of histological methods and gonadosomatic indexes. Four gametogenic stages were identified in males (I immature, II maturing, 1II mature, IV spawning) and in females (I immature, II maturing, 1II pre-spawning, IV spawning). The sex ratio obtained was not significantly different from 1:1 (P>0.01). Mature males were found during the whole year, September being the month when the highest rate of sexually active individuals occurred (48%). In females, the gametogenic cycle commenced in December and ended in November, and spawning occurred between April and October, with two maximum peaks in August and September (48% in each). Size at sexual maturity was 850 g of total body weight for males and 1,250 g of total body weight for females. Males mature earlier than females.

Sexual and asexual reproduction of the fissiparous starfish Allostichaster capensis were examined for 24 months at Bahia Kaiser, Golfo Nuevo, Chubut, Argentina. Gonad indices revealed an annual reproductive cycle, with peak development occurring in late winter (August). Spawning occurred in spring (September). Pyloric caeca indices displayed a clear annual cycle and a reciprocal relationship with gonad indices, showing the storage function of pyloric caeca. The starfish population appears to be largely maintained by fission, as only two females were found. A. capensis also showed an annual cycle of fission, with the highest frequency in spring and summer (from November to January), just after spawning. Incidence of fission was correlated with environmental factors such as photoperiod, seawater temperature, and salinity., Introduction Asexual reproduction by fission is one of the reproductive methods of some starfish: they split their bodies into two or three parts. Each resulting part regenerates a complete individual, [...]

In an approach to study the evolutionary conservation of molecules of the Wnt signal transduction pathway, we analyzed the function of the major negative regulator of this pathway, GSK3 (glycogen synthase kinase 3), in the basal metazoan Hydra. Microinjection assays reveal that HyGSK3 inhibits [beta]-catenin in zebrafish embryos, indicating that the function of GSK3 in the canonical Wnt signaling pathway is evolutionarily conserved. In Hydra, HyGSK3 transcripts are strongly upregulated during gametogenesis. Treatment of female polyps with the GSK3 inhibitors lithium and alsterpaullone prevents the differentiation of nurse cells and subsequent oocyte formation. Our data indicate that GSK3 is required for the early induction of apoptosis in germline cells, which has been shown to be an initial step in Hydra gametogenesis. Our experiments show that main functions of GSK3 are evolutionarily conserved and unique to multicellular animals, a conclusion which is additionally supported by the presence of specific regulatory domains in the HyGSK3 protein. Keywords: Cnidaria; Hydra; GSK3; Wnt; Oogenesis; Gametogenesis; Apoptosis; Nurse cell

Reproduction of the ophiuroid Ophiactis resiliens Lyman 1879, a common species in the shallow waters around Australia, was examined over 1 year in two populations near Sydney, New South Wales. Gametogenesis was documented by histological examination of the gonads. Vitellogenesis in females and spermatocyte proliferation in males started in February and March. O. resiliens had an annual spawning period from May to September/October with peak gamete release from May to July. Thereafter, spawning occurred in some specimens through November. Gravid gonads were present for approximately 2 months longer in O. resiliens from Clovelly Bay than in those from Little Bay, At both sites spawning was episodic and gametogenesis continued through most of the spawning season. Most specimens (50-100%) collected from November to March had indeterminate/recovery stage gonads, the sex of which, could not be determined. The timing of gametogenic renewal during these months varied among individuals. O. resiliens has a 3-month planktonic stage and the presence of juveniles, 0.5-1.5 mm disk diameter, in the coralline algal turf at Little Bay from February to May, suggests that settlement occurs in summer and autumn at this site. In contrast, juveniles were rarely encountered in coralline turf at Clovelly.

Previous research on gametic incompatibility in marine invertebrates suggests that for highly dispersive marine invertebrate species, barriers to fertilization among closely related taxa are often incomplete and sometimes asymmetric. The nature of these barriers can dramatically affect the patterns of gene flow and genetic differentiation between species, and thus speciation. Blue mussels, in the genus Mytilus, are genetically distinct in allopatry yet hybrids are present wherever any two species within the group co-occur. The present study sampled M. edulis (L.) and M. trossulus (Gould) in May and June 2001 from the East Bay section of Cobscook Bay, Maine, USA (latitude 44[degrees]56'30'N; longitude 67[degrees]07'50'W), where the two species are sympatric. Gamete incompatibility was investigated in a series of laboratory fertilizations carried out in July 2001. The proportion of fertilized eggs typically exceeded 80% at sperm concentrations of [10.sup.3]-[10.sup.4] [ml.sup.-1] among intraspecific matings (n = 18), but was < 30% even at sperm concentrations in excess of [10.sup.5]-[10.sup.6] [ml.sup.-1] for interspecific matings (n = 13). Further analysis indicated that approximately 100- to 700-fold higher sperm concentrations were required to achieve 20% fertilization in interspecific matings relative to intraspecific matings, indicating strong barriers to interspecific fertilization. The proportion of fertilized eggs did not follow this general pattern in all matings, however. The eggs from two (out of five) M. edulis females were almost as receptive to M. trossulus sperm as they were to M. edulis sperm. In contrast, the eggs from all M. trossulus females (n = 3) were unreceptive to M. edulis sperm, suggesting that fertilization barriers between these species may be asymmetric. Given the experimental design employed in this study, the results are also consistent with a strong maternal or egg effect on the level of interspecific gamete compatibility in M. edulis.

In animals with internal fertilization, ovulation and female sperm storage are essential steps in reproduction. While these events are often required for successful fertilization, they remain poorly understood at the developmental and molecular levels in many species. Ovulation involves the regulated release of oocytes from the ovary. Female sperm storage consists of the movement of sperm into, maintenance within, and release from specific regions of the female reproductive tract. Both ovulation and sperm storage elicit important changes in gametes: in oocytes, ovulation can trigger changes in the egg envelopes and the resumption of meiosis; for sperm, storage is a step in their transition from being 'movers' to 'fertilizers.' Ovulation and sperm storage both consist of timed and directed cell movements within a morphologically and chemically complex environment (the female reproductive tract), culminating with gamete fusion. We review the processes of ovulation and sperm storage for Drosophila melanogaster, whose requirements for gamete maturation and sperm storage as well as powerful molecular genetics make it an excellent model organism for study of these processes. Within the female D. melanogaster, both processes are triggered by male factors during and after mating, including sperm and seminal fluid proteins. Therefore, an interplay of male and female factors coordinates the gametes for fertilization. Keywords: Oocyte; Egg; Sperm; Activation; Ovary; Sperm storage; Mating; Seminal fluid proteins; Accessory gland protein; Cell migration

Byline: Hilal Ilarslan (1), Harry T. Horner (2), Reid G. Palmer (3) Keywords: Confocal laser scanning microscopy Glycine max Megagametophyte Ovule abortion Partial sterility Abstract: Megagametogenesis of soybean, Glycine max (L.) Merr., cultivars Clark and Clark k2, and F1 hybrid of Clark (female parent) crossed with Clark k2 (male parent) were studied using stereo light microscopy and confocal scanning laser microscopy. Reproductive development in Clark and Clark k2 plants was compared to F1 hybrid plants. In mature pods, 6.4% of the ovules of Clark, 8.1% of the ovules of Clark k2, and 41.4% of the ovules of F1 hybrid plants were aborted. This female partial sterility was due to incomplete megagametophyte development: undeveloped polar nuclei--or developed but not in a position for fertilization increased megagametophyte wall thickness abnormal shape and/or premature degeneration of synergids and intact synergids throughout the life of the ovule egg cell not well-developed or absent and megagametophyte remaining uninucleate. Each of these abnormalities contributed to either lack of double fertilization or early megagametophyte abortion. Author Affiliation: (1) Department of Biology, Ankara University, 06100, Tandogan, Ankara, Turkey (2) Department of Botany and Bessey Microscopy Facility, Iowa State University, IA 50011-1020, Ames, USA (3) USDA ARS-CICGR and Departments of Agronomy and of Zoology/Genetics, G301 Agronomy, Iowa State University, IA 50011-1010, Ames, USA Article History: Received Date: 29/07/2002 Accepted Date: 20/12/2002 Article note: Electronic Publication

Over a 3-year period (1996-1998), reproduction of the commercial sea cucumber Holothuria scabra (Jaeger, 1833) was investigated in the Solomon Islands to determine the spawning pattern and whether gametogenesis is continuous or seasonal. The gonad consisted of a single cohort of tubules that developed uniformly. Macroscopic examination of the gonads revealed that mature gametes were present throughout the year. Individuals with gonads at different stages of maturity were present in most samples. Partly spawned gonads were prevalent in females, whereas mature gonads were prevalent in males. The time at which the peak gonad index was recorded differed among years. Although gametogenesis was continuous, with a potential for prolonged gamete release, a period of enhanced spawning occurred during the dry season, from September to December. Maximum gonad indices were reached prior to and during this period of enhanced spawning. Histology revealed that gametogenesis reinitiated in partly spawned gonads, resulting in the presence of gametes at different stages of development in the gonad. The uniform growth of gonad tubules indicated that H. scabra does not conform to the progressive tubule recruitment model described for holothurian oogenesis. Continuous reproduction in H. scabra and prolonged availability of mature gametes would facilitate use of this species for aquaculture.

Research has been conducted on the gametic disequilibrium between gene arrangements of the O chromosome and Acph, Lap and Pept-1 allozyme loci. The seasonal variation of this equilibrium has been examined in a natural population of Drosophila subobscura and the results are reported.

Reproduction of Holothuria fuscogilva (Selenka, 1867) in the Solomon Islands was investigated over a 4 yr period (1994 to 1998) by macroscopic and microscopic examination of the gonad tubules, the gonad index (GI) method, histological examination of gametogenesis, and spawning-induction trials. The gonad consisted of numerous tubules that dominated the coelom of gravid specimens. New tubules appeared in March, and grew in size and extent of branching until they reached their maximum size and maturity in August. Spawning occurred from August to October, with the majority of gametes released during October, although it was only partial in many individuals. After spawning, the tubules appeared wrinkled and resorbed into the gonad basis. A five-stage gonad maturity scale based on the macroscopic appearance of the gonad tubules corresponded with discrete stages of gametogenesis identified by histology. Gametogenesis was initiated in mid-March, with oogenesis and spermatogenesis occurring in parallel, followed by the growing stage (May to July) which was marked by active gamete development. Successful induction of spawning during the breeding period corroborated the GI and histological data. The uniform growth of gonad tubules indicated that H. fuscogilva in the Solomon Islands does not conform to the progressive tubule recruitment model described for other holothurians. An important application of this study is that the appearance of gonad tubules, removed by biopsy, can be used to determine the gonad condition of wild adults or captive broodstock.

Sabella spallanzanii (Gmelin) is one of the best known and widely distributed Mediterranean polychaetes, but available data on its general biology has been inferred mostly from populations recently introduced to Australia. In the present paper, data on gametogenesis and larval development of a Mediterranean population from the Gulf of Taranto (Ionian Sea, Italy) are reported. Histological and electron microscopical analysis of gametogenesis showed that oogenesis, a long process beginning soon after spawning in February, is of extraovarian type. By contrast spermatogenesis is a very fast process lasting from September to December, when the coelomic cavity is completely packed with mature gametes and almost devoid of coelomocytes. During the period of spawning, some experiments of in vitro fertilisation were performed, always without success, while some of the collected females naturally spawned fertilised eggs (100%). Particularly interesting was the discovery of a small percentage of eggs which appeared fertilised but unspawned within the coelomic cavity of female. Investigation of the S. spallanzanii life cycle, from the naturally spawned fertilised eggs to embryonic and juvenile stages, was performed by daily microscopical observations and by SEM. Despite the presence of large eggs giving rise to a lecithotrophic larva, a long pelagic phase was observed, the longest found among Sabellidae. The larval development pattern is also described. Settlement began after about 2 weeks; metamorphosis occurred 10 d after settlement, when mucus was secreted abundantly and an external tube was formed. The long larval pelagic period and the development pattern, suggesting a high potential for dispersal, support both the introduction and invasive behaviour of the species in Australian waters.

The ultrastructural features of gametogenesis have been described in the methane-seep mytilid bivalve Bathymodiolus childressi Gustafson, Turner, Lutz & Vrijenhoek, 1998 collected from the Gulf of Mexico in August 1995. This is the first ultrastructural description of gametogenesis in any methane-seep bivalve. B. childressi is gonochoric, and both the testis and ovary consist of acini surrounded by inter-acinal tissue composed of adipogranular cells that serve a nutrient storage function. Oocytes develop in close association with squamous follicle cells although the follicle cells do not appear to play a primary role in yolk synthesis. During the vitellogenic phase, biosynthesis of four types of organelles occurs, including lipid droplets, yolk granules, cortical granules, and unknown inclusions, which are exocytosed as part of egg envelope biogenesis. Vitello-genesis appears to be largely autosynthetic involving the Golgi complex and rough endoplasmic reticulum. Sperm differentiation resembles that reported in other mytilid bivalves and includes the differentiation of proacrosomal granules and a flagellum during the early stages of spermatogenesis. Mature sperm have a cap-like acrosome, substantial subacrosomal material, a bullet-shaped nucleus, and four to five mitochondria in the midpiece. The general features of gametogenesis closely resemble those reported in shallow-water, seasonally reproducing mytilids. Despite the relatively stable methane seep environment and presumed continuous availability of nutrients, reproduction parallels that of littoral mytilids, suggesting some phylogenetic constraints on the capacity for variability in gametogenic processes in the family Mytilidae.

The fundamental assumption of Mendelian genetics is that behavior of an allele is identical whether it arrives to a zygote through paternal or maternal germline pathway. Gametic imprinting phenomena discovered and studied in mammals show limitations of the classical view in special cases. Two sources of evidence were essential to describe gametic imprinting. The first approach based on genetic evidence demonstrated that some maternally and paternally derived regions of certain chromosomes were not equivalent. Paternal or maternal disomy of the regions containing particular genes caused significant effects on viability and development of progeny. The second set of data was obtained by nuclear transplantations and parthenogenetic activation of mammalian oocytes. These data suggested that the contribution of parental genomes was not equivalent and differential imprinting of nuclear genes during gametogenesis was very likely. The number of loci found in mice, which show gametic imprinting, is 34 and continues to grow. It is generally accepted that gametic imprinting is a mammalian invention and there are differences in imprinting pattern between species. Most hypotheses propose involvement of imprinted genes in the control of fetal growth and fetal-maternal interactions, thus keeping a balance between contradictory fetal and maternal requirements. Molecular mechanisms responsible for gametic imprinting still remain to be studied, but for several genes it was shown that imprinting marks are imposed by a parent-specific methylation process during gametogenesis. These marks are resistant to global demethylation during cleavage and to global de novo methylation after implantation and maintain different methylation patterns in paternal and maternal alleles of imprinted genes. About 20 to 25% of all transgene loci studied demonstrate similarities with imprinted genes. For instance, methylation of some transgenes is dependent on parental gametic pathway and reversible in the next generation. There are data indicating that selection of modifier genes may change the effects of gametic imprinting. It is possible that future selection and crossbreeding programs may take gametic imprinting into consideration. Key Words: Gametes, Epigenetics, Methylation, Development, Cloning

A PCR-based cDNA subtraction method was employed to determine the genes that are expressed as small cells of the centric diatom Thalassiosira weissflogi initiate gametogenesis. Three of the sexually induced genes, Sig1, Sig2 and Sig3, were sequenced to completion and are members of a unique gene family. The three polypeptides encoded by these genes have different molecular masses and charges but have many common characteristics. It was observed that the SIG polypeptides may play a role in sperm-egg recognition.

Research was conducted to examine the role of molecules in the mammalian fertilization process. Molecular involvement were observed in three steps including the binding of sperm to eggs, the fusion of sperm and eggs and the induction of the acrosome reaction by sperm. The mammalian fertilization process involves unique molecules such as ZP glycoproteins but the principles gained from somatic cells apply with respect to cellular adhesion, fusion and exocytosis.

Research was undertaken to examine the mode of reproduction in the scleractinian coral, Pocillopora verrucosa, influenced by morphological, habitat and environmental conditions along the KwaZulu-Natal coast in South Africa. Pocillopora verrucosa is a branching scleractinian mostly known as the 'knob-horned' coral and its reproductive strategy involved broadcast-spawning and simultaneous hermaphroditism. It was also revealed that the coral spawned during new moon and that depth did not affect the reproduction mode. Gametogenesis was affected by changes in sea temperature.

Although fertilization has been studied for more than a century, the cell surface proteins mediating the process are only now becoming known. Gamete interaction in animals appears to be molecularly complex. Although it is difficult to generalize at present, diversity of structure may be a recurring theme in the evolution of fertilization proteins. Examples of rapid evolution of fertilization proteins by positive selection are known, and concerted evolution can influence the differentiation of gamete recognition proteins between closely related species., Sexual reproduction, defined here as the fusion of two haploid cells during fertilization to form a diploid zygote, occurs in almost all eukaryotes. Fertilization is the bridge between generations. Although [...]

Allozyme variability has been studied in sexual and parthenogenetic freshwater planarians. Evidence of genotypic diversity suggests a polyphyletic origin of parthenogenetic lines in mixed populations via hybridization with coexisting sexuals. New, genetically distinct parthenogenetic lines may arise in natural populations through the hybridization of sympatric sexuals and parthenogens.

A study was conducted on the soft coral Anthelia glauca found on the reefs of KwaZulu-Natal, South Africa, to examine its reproductive process. Results showed that the female polyps produce many cycles of larvae during a breeding period ranging from four to five months. The fertilization and transfer of eggs occur during a full moon and mature larva are released after new moon. The A. glauca oocytes have no zooxanthellae, but zooxanthella starts during immature larval stage.

Male gametogenesis was cytologically analyzed in wheat lines homozygous or hemizygous for gametocidal (Gc) factors with different modes of action. The first and second meiotic divisions in all lines were cytologically normal. The postmeiotic mitoses were normal in the homozygous lines; however, chromosome fragments and bridges were observed in the mitoses of the hemizygous lines. The morphology of the chromosome fragments suggests that the Gc genes induce chromosome breaks in the [G.sub.1] phase prior to DNA synthesis of the first postmeiotic mitosis. The age of an anther was correlated with the frequency of aberrant second mitosis. Younger anthers contained a higher number of pollen undergoing normal second mitosis. This observation suggests that the arresting of the cell cycle occurs as the result of chromosome breaks during the first mitosis. Because chromosome bridges were more frequent than fragments in the second mitosis, breakage-fusion-bridge cycles possibly occurred during gametogenesis, which led to further chromosomal rearrangements. The Gc factors located on chromosomes 2S of Aegilops speltoides and [4S.sup.sh] of Ae. sharonensis induce severe chromosome breakage in pollen lacking them. However, the Gc factor on telosome 2[C.sup.c]L of Ae. cylindrica only induced chromosome breaks at a low frequency. The observed partial fertility of Gc lines is presumably due to cell cycle arrest and the competition among gametes with and without chromosome breakage.

Ovule and seed development is described for Lacandonia schismatica, a species whose androecium is surrounded by the gynoecium. The ovule in each carpel is basal, anatropous, tenuinucellate, and bitegmic. The female gametophyte is formed by the micropylar megaspore cell, after a coenocytic stage of the four megaspore nuclei. The mature female gametophyte has the normal complement of seven cells and eight nuclei. We propose a new type of female gametophyte development on the basis of the coenocytic stage of the tetrad, the cellularization of the tetrad, and the survival of the micropylar spore. At seed dispersal time, the embryo has [approximately]10-20 cells. Endosperm development is of the nuclear type. At maturity, endosperm cells show starch and protein inclusions as well as polysaccharides in their thick walls. The seed coat is formed from the outer integument; the inner one disappears. The exotesta contains tannin. The fruit (achene) wall is two-layered. The maturation of the fruits in a flower is synchronous, and they separate from the receptacle for dispersal. Key words: female gametophyte; Lacandonia; Lacandoniaceae; ovule; seed; Triuridaceae.

The role of A-myb in spermatogenesis and mammary gland development was established by utilizing genomic fragments cloned from a-myb homozygous mice. Results revealed that a-myb gene spliced mice develop to full term but exhibited defects in growth and male infertility due to arrested spermeiogenesis at the pachytene phase. Female adult a-myb gene spliced mice show underdeveloped lactating breast tissues.

Previous work identified a [Gamma]-tubulin gene, [Gamma]Tub23C, in Drosophila (Zheng et al., 1991). We now report identification of a second [Gamma]-tubulin gene, [Gamma]Tub37CD. Immunoblot analysis and immunolocalization show that [Gamma]Tub37CD and [Gamma]Tub23C are differentially expressed during gametogenesis and development. During oogenesis, [Gamma]Tub23C was detected at centrosomes and in the cytoplasm of mitotic germ cells, but was not detected in germ cells following completion of mitosis. Conversely, [Gamma]Tub37CD was not detected in proliferating germ cells, but appeared to accumulate in germ cells during egg chamber development. Neither [Gamma]-tubulin isoform was detected at the anterior or posterior poles of developing oocytes. During spermatogenesis, only [Gamma]Tub23C was detected at centrosomes, where it showed cell cycle- and differentiation-dependent organization. During the transition into the first meiotic division, [Gamma]Tub23C became organized as a corpuscular focus at centrioles until completion of meiosis II. During postmeiotic spermatid differentiation, [Gamma]Tub23C was detected first as a rod and then as a collar-like structure near the juncture of the nucleus and the elongating flagellum, but was not detected in bundles of mature sperm. The germline-specific CDC25 encoded by twine is required for organization of [Gamma]Tub23C into corpuscular focus in spermatocytes, but not for separation of centriole pairs in M-phase or postmeiotic organization of [Gamma]Tub23C at centrioles. Following reconstitution of a canonical centrosome at fertilization, only [Gamma]Tub37CD was detected at centrosomes in syncytial embryos, but both [Gamma]Tub37CD and [Gamma]Tub23C were detected at centrosomes in cellularized embryos. Colocalization of these two isoforms suggests that [Gamma]Tub23C and [Gamma]Tub37CD both contain structural features of [Gamma]-tubulins essential for localization to centrosomes.