Overripe Eggs Research Articles

Fertilization strategies for Sea Bass Dicentrarchus labrax (Linnaeus, 1758): effects of pre-incubation and duration of egg receptivity in seawater

Studying gamete biology can provide important information about a species fertilization strategy as well as their reproductive ecology. Currently, there is a lack of knowledge about how long sea bass Dicentrarchus labrax eggs can remain viable after being activated in seawater. The objectives of this study were to understand the effects of pre-incubation of fresh and overripe sea bass eggs in seawater and to determine the duration of egg receptivity. Pooled eggs (fresh and overripe) from four females were pre-incubated in seawater for 0 min (control), 0.5 min, 1 min, 3 min, 10 min and 30 min and then fertilized by pooled sperm from four males. The fresh eggs had a higher fertilization success than overripe eggs. Our results revealed a significant effect of pre-incubation time for both the fresh (P < 0.01) and overripe eggs (P < 0.01). Fertilization success of eggs significantly declined for both these treatments after 3 min of pre-incubation, which clearly indicates that sea bass eggs are able to be fertilized by sperm for up to 3 min after release into seawater. This study has particular importance for understanding fertilization strategies, reproductive potential, as well as reproductive ecology of sea bass.

Studies on gonadosomatic index, fecundity and hatchability of domesticated stock of asala Schizothorax richardsonii (Gray) from Nallu River of Lalitpur District

The present work embodies studies on the reproductive capacity of captive stock of asala Schizothorax richardsonii collected from Nallu River of Lalitpur district. Gonadosomatic index (GSI) estimates ranged from 3.08±0.9% in May to 26.55±1.8% in November. Positive correlation (r=0.667) was found between egg size and GSI. The egg size (2.7 to 2.9 mm) in October and November was significantly (P&lt;0.01) larger than the eggs measured in other months. Based on peak GSI level, S. richardsonii spawned by manual stripping in two breeding season i.e. winter (October-November) and summer (Mach-April) in Godawari (1500 masl). Mean incubation period of fertilized eggs was 259 h and 248 h during winter and summer season at 14.2 to17.5 oC and 14.5 to15.5 oC water temperature, respectively. Percent hatching rates of eggs ranged between 38 to 90% and were not significantly different (P&gt;0.05) between breeding seasons. Overripe eggs obtained during winter season breeding (16.5%) were significantly higher (P&lt;0.01) than the summer season breeding (3.6%). This suggests that more frequent observation of the spawner is necessary during winter season for recognizing their appropriateness to ovulation. DOI: http://dx.doi.org/10.3126/on.v12i1.12253Our Nature (2014), 12(1): 19-27

Fertilization and hatching rates and larval performance in captive common barbel (Barbus barbus L.) throughout the spawning season

The aim of this study was to investigate changes in reproductive success including fertilization and hatching rates and larval performance as indicated by body weight and resistance to osmotic stress in captive common barbel (Barbus barbus L.) throughout the reproductive season. Spawning of B. barbus broodstock in captivity proceeded from February 01 to June 21 during 2006. Within the spawning period, fertilization and hatching rates and larval performance (body weight and resistance to osmotic stress) were studied at 7-day intervals. The average number of spawnings for each female was 2.8. Average fecundity was 1650 ± 460 eggs per spawning. A high proportion of females delivered poor egg quality (overripe eggs) during the spawning season from 57% on February 15 to 38% on May 31. The lowest fertilization and hatching rates were observed at the beginning (February 1, 18.5 ± 2.5% and 5 ± 2.5%, respectively) and the end (June 21, 25 ± 7% and 5.5 ± 2.5%, respectively) of the spawning period. While the highest values of both rates were found in period from March 22 (72.5 ± 5%) to May 10 (68 ± 4%) and from April 19 (53.8 ± 10%) to May 17 (50.5 ± 5%), respectively. The lowest larval body weight and resistance to osmotic stress were found at the beginning (8.0 ± 0.7 mg and 0 ± 0%, respectively) and the end of the spawning period (8.0 ± 0.7 mg and 25.2 ± 5%, respectively). The highest larval body weight and resistance to osmotic stress were recorded from March 15 (11.3 ± 0.9 mg) to May 31 (11.0 ± 0.7 mg) and from May 10 (93.5 ± 5%) to May 31 (90.7 ± 8%), respectively.

Artificial maturation and reproduction of European silver eel: Development of oocytes during final maturation

Attempts on artificial maturation of European eel ( Anguilla anguilla) have largely been unsuccessful. The moment of stimulation of final maturation and ovulation is mainly based on weight increase related to the hydration response of the oocytes, which, in the European eel, is irregular. In contrast to Japanese eel, European eels show wide individual variability and much slower response to hormonal stimulation. In this study, the oocyte development of wild European silver eels was followed during final maturation. We describe 7 developmental stages based on 6 parameters: transparency, position and visibility of the nucleus, diameter of the oocyte, and diameter and number of oil droplets. Together, these parameters describe unidirectional changes from immature to over-ripe eggs. The developmental status of the gonads can thus be determined from biopsies. Of 23 female eels, 14 ovulated and were stripped, and 9 gave eggs that could be fertilised. Oocytes mature asynchronously, but this seems to be an artefact since fertility dropped with every new generation. As the timing of ovulation is crucial for fertility of the eggs, our developmental index of oocytes may result in more successful maturation protocols.

Lack of Correlation between Chinook Salmon Spawn Survival and the Number of Overripe Eggs as Determined by Digital Imagery

AbstractThe number of overripe eggs in spawn of landlocked fall Chinook salmon Oncorhynchus tshawytscha was determined quantitatively from digital images recorded prior to fertilization. The percentage of overripe eggs recorded from the digital images was not significantly correlated with survival at egg eye‐up, fry hatch, or swim‐up but was significantly correlated with the visually estimated number of overripe eggs (r 2 = 0.914, P &lt; 0.001). There was also no significant difference between the percentages of overripe eggs determined by the two methods. Neither the digital image nor visual‐estimation techniques for assessing overripe eggs are reliable predictors of egg survival, but the digital imagery validated the use of visual estimates.

Potential Indicators of Egg Viability in Landlocked Fall Chinook Salmon Spawn with or without the Presence of Overripe Eggs

Abstract Selected reproductive characteristics obtained during the spawning of landlocked fall chinook salmon Oncorhynchus tshawytscha from Lake Oahe, South Dakota, were evaluated for their use as predictors of embryo survival to the eyed egg stage. Spawn was categorized according to the presence or absence of observable overripe eggs. No significant differences in female length, female weight, the number of eggs per female, egg size, the amount of ovarian fluid released during spawning, and ovarian fluid specific gravity, pH, and conductivity were observed between spawn containing overripe eggs and spawn without overripe eggs. Conductivity was significantly positively correlated to embryo survival only in spawn without overripe eggs, while the total number of eggs per female was only positively correlated to embryo survival in spawn with overripe eggs. Spawning female weight, the number of eggs per female, and egg size were significantly different in spawn containing overripe eggs where no embryo surviva...

Viability of Inland Fall Chinook Salmon Spawn Containing Overripe Eggs and the Reliability of Egg Viability Estimates

Abstract Egg survival to the eyed stage from female inland fall chinook salmon Oncorhynchus tshawytscha that released no apparent overripe eggs was compared with egg survival from the spawn of females with varying percentages of overripe eggs. Use of the estimated number of initially overripe eggs as a predictor of egg survival to the eyed stage was also evaluated. No significant differences in female total length, number of eggs per female, or egg size were observed between the two groups of females. Percent egg survival to the eyed stage of development differed significantly between groups. Females with noticeably overripe eggs produced eggs that had a 30.0% mean survival to the eyed stage versus 50.6% for the eggs from females with no overripe eggs in their spawn. However, visual estimation of the initial number of overripe eggs was not an accurate predictor of egg survival to the eyed stage.

Overripening as the cause of low survival to hatch in Lake Erie coho salmon (Oncorhynchus kisutch) embryos

We investigated the cause of the low survival to hatch of embryos of coho salmon (Oncorhynchus kisutch) from the Fairview, Pennsylvania, stock in Lake Erie. In 1988, survival to hatch of this stock was only 42%, whereas another Great Lakes coho salmon stock of similar genetic origin had an 84% survival to hatch. Laboratory cross-fertilization studies between the Fairview stock and a reference Lake Erie stock from Simcoe, Ontario, showed that eggs from the Fairview stock were the probable source of the low fertility. The presence of overripe eggs in Fairview females was associated with poor fertilization and low survival to hatch. Plasma gonadotropin II levels were similar in preovulatory females taken from the Fairview and Simcoe stocks, but testosterone and 17α, 20β-dihydroxy-4-pregnen-3-one levels were significantly lower in the Fairview females. Increasing the triiodo-L-thyronine (T3) content of the eggs by the administration of T3 to the preovulatory females did not enhance egg fertility. We propose that the low survival to hatch of the Fairview embryos is due to delayed oocyte maturation and ovulation and vent maturation, which may have been caused by exposure of the Fairview salmon to warmer water during the period of late ovarian maturation and migration.

Volitional Tank Spawning of Female Striped Bass with Male White Bass Produces Hybrid Offspring

We report the first volitional tank spawning of female striped bass Morone saxatilis with male white bass M. chrysops. The female striped bass were reared for 6 or 8 years from larvae to mature adults in captivity. The wild-caught male white bass were acclimated to captivity 1 year before spawning trials. The fish were induced to mature with implanted pellets containing synthetic analogue of mammalian gonadotropinreleasing hormone, [D-Ala6-Pro9-NEt]-LHRH, at 10 μg/ kg body weight in a cholesterol and cellulose matrix. Males later received an additional injection of human chorionic gonadotropin at 500 IU/kg body weight to maintain spenniation. At hormone implantation, females were in an advanced state of maturity with oocyte diameters ranging from 650 to 1,000 μm and males were producing milt. Eight females were placed in tanks with three or six males for spawning. Three females did not release eggs within 14 d. The remaining five females spawned, but only two produced fertilized eggs and hybrid offspring. All spawnings had large numbers of overripe eggs, which suggests that striped bass females had a behavioral aversion to spawning with white bass males.

Reproduction of striped bass, Morone saxatilis (Walbaum), broodstock: monitoring maturation and hormonal induction of spawning

Levels of gonadal steroid hormones were quantified in an adult striped bass, Morone saxatilis (Walbaum), broodstock during their gametogenic cycle. Blood plasma concentrations of Estradiol (E2) and testosterone in females, or 11-ketotestosterone(11-KT) and testosterone (T) in males, were used as indicators of maturation. In both sexes, hormone levels were low in summer but increased significantly by late October to intermediate levels which were then maintained until late January. They then increased again rapidly to maximum pre-spawning values attained in late February or March, and subsequently decreased during the spawning period (April and May) with an increased incidence of spent fish with low hormone levels. The changes in blood hormone concentrations coincided with annual changes in photoperiod and water temperature that may be useful landmarks for maturation in captive broodstock. Mature females were implanted with pellets containing a dose of approximately 20 μg/kg body weight of [D-Ala6-Pro9-Net]-LHRH (GnRHa) in a matrix of cholesterol (CH) and cellulose. In April, they had not yet begun final oocyte maturation (FOM) and were too immature for conventional induction of spawning by injection with human chorionic gonadotropin (hCG). In early April, females given two 95% CH (slow hormone-release) GnRHa pellets (95/95) or females given one 80% CH (fast hormone-release) GnRHa pellet and one 95% CH GnRHa pellet (80/95) spawned within 13 days treatment (n= 4) with good egg fertility (76 ± 7% of total) and hatch rates (62 ± 15% of fertile). Females given dual fast-release GnRHa pellets (80/80) or control (Sham) pellets did not spawn or show evidence of increased oocyte diameter or development. In late April, four of six females given the 80/95 GnRHa pellet combination spawned within 9 days. Three fish produced fertile eggs (54 ± 18%). one spawned overripe eggs, and the remaining two increased oocyte diameter and maturation. Three corresponding controls did not spawn, and two of these showed clear signs of atresia within 11 days. In early May, some females were undergoing early FOM and were mature enough to be spawned by hCG injection. Three were given a single 80% CH GnRHa pellet and spawned within 6 days of treatment to produce fertile eggs (44 ± 6%). Of two other females given dual 80% CH GnRHa pellets, one spawned infertile eggs and the other failed to spawn within 9 days. GnRHa implants show promise as a technique for inducing spawning of captive striped bass broodstock although the optimum hormone delivery systems, dosages and release rates should be verified for fish at specific maturational stages.

Biochemical changes associated with overripening of the eggs of rainbow trout Salmo gairdneri Richardson

This study of the biochemical composition of mature unfertilised eggs of rainbow trout was undertaken to investigate normal intraspecific variation in egg composition between parent females, and to describe the biochemical changes which occur after ovulation during overripening in the parental abdominal cavity. The following aspects of egg composition were measured: wet and dry weight, chorion weight, free and bound lipid, protein phosphorus, lipid phosphorus, precipitable protein, calcium, and iron. All these were determined on single eggs, and six eggs were examined from each female. Ripe eggs, defined as those stripped within 3 days of ovulation, were obtained from 7 females. Overripe eggs, defined as those stripped 30 or more days after ovulation were obtained from 8 females. Results were expressed in absolute terms (mg or μg of component per egg) and relative terms (percentage of egg dry weight). In ripe eggs, there was significant variation between females in all these aspects of egg composition when expressed absolutely, and in all except lipid phosphorus when expressed relatively. In overripe eggs, there was significant variation in all these aspects between females when egg composition was expressed either absolutely or relatively. Comparison of ripe and overripe eggs showed that overripening was accompanied by the following significant changes expressed absolutely: increase in water content, free lipid, iron, calcium; decrease in bound lipid, precipitable protein, protein phosphorus, lipid phosphorus, total lipid and chorion weight; when expressed relatively there were increases in water content, free lipid, iron, calcium, total lipid and chorion weight, and decreases in bound lipid, precipitable protein, protein phosphorus and lipid phosphorus.

Effects of 11-desoxycorticosterone-acetate and carp pituitary suspension on follicle maturation in the ovaries of the African catfish, Clarias lazera (C. & V.)

Administration of 11-desoxycorticosterone-acetate (DOCA) or carp pituitary suspension (CPS) to broodfish of the African catfish Clarias lazera leads to maturation of postvitellogenic oocytes. CPS also causes ovulation, but not oviposition. After DOCA injection, ovulation and oviposition of mature oocytes can be evoked mechanically by stripping. Only postvitellogenic oocytes measuring more than 1 mm in diameter undergo maturation, and only eggs that have passed through all stages of maturation develop into normal fry upon fertilization. The time required for postvitellogenic oocytes to give the highest hatching percentages and the lowest fractions of deformed fry is 11–14 h for CPS and about 14 h for DOCA at 25°C. By producing an eosinophilic material, the granulosa cells of atretic follicles and postovulatory follicles contribute to the disintegration and clearance of degenerating oocytes and over-ripe eggs.

Overripe eggs and postovulatory corpora lutea in the threespine stickleback, Gasterosteus aculeatus L., form trachurus

Threespine sticklebacks (Gasterosteus aculeatus L., form trachurus) with overripe, ovulated eggs have a hard 'berried' abdomen, easily distinguishable from the soft, smoothly distended abdomen of fish with normal ovulated eggs. The 'berried' fish weigh less and have a smaller GSI than 'nonberried' ovulated fish but the percentage water of their whole ovaries is the same. In contrast with 'nonberried' fish, 'berried' fish do not respond to male courtship. Overripe eggs are typical of those in other species with aggregation of cytoplasm and oil droplets at the animal pole. However, in contrast with normal ovulated eggs, they are larger, more transparent, and have a higher percentage water content although surrounded by much less fluid within the ovarian cavity. Overripe eggs do not appear to form a perivitelline space in fresh water. In 'berried' fish both the postovulatory corpora lutea (follicles) and ovarian epithelium (lining of the ovarian cavity) show histological signs of regression, in contrast with the histologically active condition of these tissues in fish with normal ovulated eggs. It is suggested that postovulatory corpora lutea play a role in maintenance of ovulated eggs in the ovarian cavity through secretion of steroid(s) which in turn stimulate the ovarian epithelium to secrete the bathing fluid of the eggs.

Chromosomal aberrations in embryos from overripe eggs

Overripeness in eggs of Rana pipiens was obtained by keeping postovulatory females at room temperature and delaying fertilization 3–5 days. In Xenopus laevis similar results were attained by delaying ovulation. About 80 crippled embryos, issued from overripe eggs that were used for chromosomal studies, had reached prefeeding stages ranging from 20 to 24. By this time the most severely abnormal individuals had already died, but also the majority of those studied would probably not have been able to survive until metamorphosis. Some malformed embryos still have normal chromosome complements, but the majority show deviations which are classified as meiotic, ploidic, and cleavage types. It is concluded that overripeness of the egg is an important cause of chromosomal nondisjunction in meiotic and in mitotic divisions. No definite relationship between the type of chromosomal deviation and the morphologic character of malformations has been established, so far.

Growth of transplanted tissues derived from normal and overripe frog's eggs.

Growth of transplanted tissues derived from normal and overripe frog's eggs.

Appearance of Accessory "Organizers" in Overripe Eggs of the Frog.

The author has described1 the condition of overripeness that develops in frog eggs if fertilization is delayed 3 to 5 days after ovulation. Among the abnormalities of embryonic development that follow, one of the most striking is the frequent appearance of reduplications. In the early gastrulation stage instead of the normal upper blastopore lip of limited extent and regular curvature there often appear long and irregular clefts and folds in the equatorial region. Attempts at gastrulation become visible not only on one side but all around the whole circumference of the embryo. As time progresses multiple blastopores and multiple gastrulation lead to the development of twin embryos. As we have pointed out previously,1 this effect indicates that overripeness has brought about 2 concomitant changes in the embryos. First, the physiological correlations by which an embryo develops as a balanced organism are impaired. These correlations largely rest on inhibitory functions by which established “organizers” (ind...

Experimentally Produced Neoplasms in the Frog.

It has been known that the frog egg on the stage of the second polar spindle-metaphase passes into a resting period, awaiting fertilization. Under natural conditions this lasts for only a few hours, but can be delayed up to 3 days without impairing perceptibly the vigor of the egg. After a further delay of 2 days, however, the eggs are dead. In the interval the eggs gradually lose their capacity to develop into normal embryos. The abnormality of these overripe eggs becomes manifest in the following features.1. The mechanism of control protecting normal eggs against polyspermy is impaired. As a consequence a high percentage of the overripe eggs show multiple segmentation. 2. In monosperm eggs the animal blastomeres are reduced in size, which effect seems to be due to a change in viscosity of the ovoplasm. 3. In the later development a marked tendency to produce axial duplications and supernumerary appendages is observed. These monstrosities as well as the polyspermy indicate a lack of control and coordinat...