Pattern Of Oocyte Development Research Articles

Histological Investigation of the Female Gonads of Chiropsalmus quadrumanus (Cubozoa: Cnidaria) Suggests Iteroparous Reproduction

The box jellyfish Chiropsalmus quadrumanus (Chirodropida: Cubozoa: Cnidaria) is common in warm waters. Although it is assumed that external fertilization is a characteristic of Chirodropida, the life history of C. quadrumanus is not yet known since its reproductive behavior has never been described, nor has the polyp has been found in nature. As a result, in the absence of documentation of reproductive behavior, we sought to test the hypothesis of external fertilization through a histological analysis of the female gonads. Herein, we analyze ten females collected in São Paulo and Rio de Janeiro (Brazil) and describe the gonadal organization and pattern of oocyte development. The discovery of four distinct stages of oocyte differentiation augments the scant existing reports of the structural and functional maturation of sex cells in Cubozoa species. Furthermore, the gonads of mature females comprise both mature (average diameter of 122 µm) and immature oocytes, suggesting that C. quadrumanus is iteroparous and exhibits multiple reproductive cycles during its life. Medusa bell size was not found to correlate with maturity state as even small females possessed a high percentage of oocytes in late vitellogenesis, suggesting that sexual maturation occurs rapidly in C. quadrumanus females.

Yolked Oocyte Dynamics Support Agreement between Determinate- and Indeterminate-Method Estimates of Annual Fecundity for a Northeastern United States Population of American Shad.

Reports of American shad fecundity identify two important themes regarding egg production in fishes. First, geographic variation occurs and is biologically meaningful. Shad annual fecundity decreases with increasing latitude, but predicted lifetime fecundity does not, because of a counter-gradient of survival probability, all of which can explain the adaptive significance of natal homing. Second, the appropriate method of measuring fecundity depends on the pattern of oocyte development. Historically, the relatively simple determinate-fecundity method was used; however, a recent study in a Virginia river indicates that this method may be biased, requiring the more complicated indeterminate method. We address both themes with collections from the 2015 shad spawning run in the Connecticut River, USA. Criteria for using a determinate method were satisfied for this northern population: 1) a size gap evident in the oocyte size frequency distribution, indicating group-synchronous development of yolked oocytes; 2) a decline, early in spawning, in the standing stock of yolked oocytes; and 3) low levels of atresia at the end of spawning. The determinate-method estimate of American shad annual (2015) fecundity (303,000 ± 73,400; mean ± sd) overlapped historic estimates for this and a neighboring river. The indeterminate-method estimate of annual (2015) fecundity (311,500 ± 4,500 sd) was not significantly different from the determinate-method estimate (Student’s t-test, P > 0.05). In contrast, indeterminate-method estimates of annual fecundity for a Virginia population were twice as high as that measured by the determinate method in the past. This can all be explained by fundamentally different patterns of oogenesis (i.e., group synchrony versus asynchrony with respect to yolk development) at different latitudes. American shad, which is distributed within its native range from the Canadian maritimes to Florida, USA (50–30°N), may be particularly well suited to evaluate intra-specific variation in oocyte development, a relatively unexplored life history trait.

Reproductive biology and spawning aggregation fishing of the white-streaked grouper, Epinephelus ongus, associated with seasonal and lunar cycles

The reproductive biology of the white-streaked grouper Epinephelus ongus, which forms spawning aggregations in the Yaeyama Islands, Okinawa, was examined by gonadal histology and oocyte development analysis. Gonadal histology showed that the spawning season was determined from April to July, but there are two spawning periods associated with the specific lunar cycle, during the week after the last quarter moon in two consecutive months. The pattern of oocyte development indicated that individual females spawned more than once, but fecundity may be determinate within a single spawning period. Fecundity was correlated to body size and ranged from several hundred thousand to a million eggs. Detailed catch data analysis showed that the catches during the two spawning months accounted for about 40 % of the annual landings and the fluctuation of the catch data corresponded well to some reproductive activities related to spawning aggregation. The two stepwise increases and the peaks of the catches coincided with the occurrence of matured individuals and the onset of spawning at the last quarter moon, respectively. These findings suggest that the spawning of E. ongus was concentrated within a few days just after the last quarter moon and that aggregation fishing was also concentrated in the critical reproductive periods.

Plasma sex steroids and gonadosomatic index variations during ovarian development of female wild yellowfin seabream (Acanthopagrus latus)

The yellowfin seabream (Acanthopagrus latus) has a good potential for mariculture in Iran, so studies on various aspects of its culture has been carried out. In this study, the characteristic of reproduction in this species was investigated. The involvement of steroid hormones in the development of gonads was assayed by sampling blood and gonad tissue in 85 females of A. latus in fish caught from the Musa Creek, north-west Persian Gulf from October 2010 to May 2011. Gonadosomatic index (GSI) and hepatosomatic index (HSI) were recorded. Developmental stages were associated with changes in sex steroids, GSI and HSI. GSI and HSI began to increase in November (immature stage) and reached the highest value in March (ripe stage), decreasing sharply in April (spent stage). Plasma values of 17β-estradiol (E2) levels reached their highest levels in spawning females in March and then decreased in April. Progesterone levels were low through ovarian development, reached a maximum simultaneously with testosterone in February (mature stage) and then decreased in March (ripe stage). The seasonal changes observed in plasma steroid levels and GSI reflected the pattern of oocyte development and the spawning behavior of yellowfin seabream and were typical of the patterns described in most multiple spawners studied to date.

Reproductive biology and spawning strategy of the catadromous percichthyid, Macquaria colonorum (Günther, 1863)

The reproductive biology and spawning strategy of the iconic catadromous percichthyid, estuary perch Macquaria colonorum was examined from three coastal rivers of south-eastern (SE) Australia. Ovarian and testicular development followed a pattern similar to that of other percichthyids, world-wide. Females were collected in significantly larger sizes and greater numbers from all, and two of the three rivers, respectively. Mean size and age at maturity was greater for females (25.05 cm FL ± 0.85 and 3.75 yrs ± 0.08, respectively) than males (22.21 cm FL ± 0.50 and 3.28 yrs ± 0.08 respectively), with no significant difference between rivers. Trends in gonadosomatic indices indicated that M. colonorum spawn in the austral winter-spring in SE Australia. However, peak spawning occurred earlier (June-August) in the two most northern rivers (Hawkesbury and Clyde) compared with the Bemm River (September-November) further south. Ripe females were captured only in the lower reaches of estuaries throughout the spawning period in all three rivers. Mature M. colonorum females displayed a group synchronous pattern of oocyte development suggesting a multiple spawning strategy. Mean batch fecundity (FB) was 266 583 ± 17 821 oocytes per female and relative fecundity was 377 ± 10 oocytes.g-1 body weight. There were significant power relationships between FB and fork length (FL), weight and age. Similar to other percichthyids, M. colonorum are long-lived, highly fecund and exhibit a flexible spawning strategy which is attuned to the highly variable environments in which they are found.

Reproduction, age and growth ofSillago maculatain south-eastern Australia

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Reproductive biology of two co‐occurring mugilids, Liza argentea and Myxus elongatus, in south‐eastern Australia

The reproductive biology of Liza argentea and Myxus elongatus occurring in two estuaries (Lake Macquarie and St Georges Basin) was found to differ. Gonado‐somatic index values and macroscopic staging of gonads identified the peak spawning period of L. argentea occurred between March and November in Lake Macquarie and January and April in St Georges Basin. In contrast, peak spawning of M. elongatus was concentrated between January and March in both estuaries. Spawning of L. argentea probably occurred in the lower reaches of estuaries as well as in nearshore coastal waters, whereas evidence indicated M. elongatus spawned only in ocean waters. The mean fork length at maturity (LF50) was greater for females than males in both species, and it also occurred at a larger mean LF in M. elongatus (males = 230 mm and females = 255 mm) than L. argentea (males = 180 mm and females = 207 mm). Estimates of total potential fecundity were also greater for M. elongatus (425 484–1 157 029) compared to L. argentea (159 933–548 954). Both species had determinate fecundity and displayed a group synchronous pattern of oocyte development, with two distinct size classes of oocytes present in mature ovaries. Liza argentea probably release the larger class of oocytes in one spawning event, but this could not be established for M. elongatus.

Patterns of oocyte growth, vitellogenin and gonadal steroid concentrations in greenback flounder

The pattern of oocyte development in association with changes of plasma concentrations of vitellogenin (Vtg), 17β‐oestradiol (E2) and testosterone (T) was investigated in maturing female greenback flounder Rhombosolea tapirina over the first part of a reproductive season (February to June). Examination of oocyte size‐frequency distributions showed that the oocyte developmental pattern in R. tapirina is multiple group synchrony, and that reproductively mature fish were present at all sampling times. There were no significant temporal variations in the gonado‐somatic index (IG), hepato‐somatic index (IH), or plasma concentrations of Vtg, E2 and T during the sampling period, which indicates that reproductive development is not synchronized within the population. Significant increases in IG, IH and plasma concentrations of Vtg, E2 and T, however, were observed in vitellogenic fish, and in fish undergoing final maturation. A positive relationship was also found between the growth of oocytes and plasma concentrations of Vtg, E2 and T, although the patterns of increase were different for each variable. Plasma concentrations of Vtg and E2 rose steadily across oocyte sizes from 100 to 450 μm, but the rate of increase of plasma E2 was slower than that of Vtg, and both reached a saturated concentration at oocyte sizes of c. 450 μm. In contrast, plasma concentrations of T showed no marked increase until oocytes grew beyond 400 μm.

Pattern of oocyte development and batch fecundity in the Mediterranean sardine

In the present study, the pattern of oocyte development was investigated in the Mediterranean sardine ( Sardina pilchardus sardina) in order to examine whether non-hydrated females could be included in batch fecundity measurements. Gonad histology and frequency distributions of oocyte diameters demonstrated that the Mediterranean sardine exhibits group-synchronous type of oocyte development. The spawning batch begins to separate in size from the adjacent population of smaller oocytes at the secondary yolk globule stage and a well-developed size-hiatus is established at the tertiary yolk globule stage. The spawning batch could be clearly identified prior to hydration and batch fecundity-on-fish weight relationships did not differ significantly between hydrated females and females at the tertiary and migratory nucleus stages. Thus, apart from hydrated females, batch fecundity in the Mediterranean sardine may also be measured by the use of females at the tertiary and migratory nucleus stages. Relative fecundity was shown to be independent of body weight and its estimates during the respective peak spawning months for the Aegean Sea and Ionian Sea stocks were 360 eggs/g (December 2000) and 339 eggs/g (February 2001).

Spatial and temporal patterns in development of eggs in the vent crab Bythograea thermydron

In this paper we describe results of a study on the reproductive biology of the hydrother- mal vent crab Bythograea thermydron. At vent sites along the East Pacific Rise, histological analyses of gonads from adult female crabs collected in November 1997, May 1999 and May 2000 provide strong evidence that B. thermydron undergoes a seasonal cycle of reproductive activity, with egg hatching peaking in April-May. Females undergo a synchronous pattern of oocyte development, whereby one cohort of oocytes undergoes vitellogenesis, while a second cohort is present and remains immature until the initial cohort reaches full maturity and is extruded onto the pleopods. When mean oocyte-size-frequency distributions were compared across months, the 2 May samples were similar to each other, with a dominance of previtellogenic oocytes and a second, smaller group of vitellogenic oocytes also present. In contrast, the November sample exhibited a wide variety of oocyte sizes, with no one size class predominating. In addition, May samples from the vent periphery contained a high proportion of females that showed evidence of recent egg hatching, while females collected from the region near the vent orifice exhibited a wide range of the intermediate stages of gonadal development. This set of data suggests an annual cycle whereby a given cohort of oocytes is in a previtellogenic state in early spring (April-May), but has begun vitellogenesis by late autumn (November) and has developed to maximum maturity by the time the eggs are extruded the follow- ing spring. While the current clutch of eggs is being brooded, a second cohort of previtellogenic oocytes begins to develop in the ovary and the cycle is repeated. Superimposed on this annual cycle is a pattern of behavior whereby females with mature gonads migrate to the vent periphery where fertilized eggs are extruded, brooded, and hatched.

Oocyte development in summer flounder: seasonal changes and steroid correlates

Seven ovarian stages are described in summer flounder Paralichthys dentatus. In the prespawning season plasma oestradiol levels increased in maturing fish with lipidogenic oocytes and gonadosomatic index increased in fish undergoing vitellogenesis. Atretic oocytes present in the postspawning season indicated which individuals may have spawned. The pattern of oocyte development is similar to that of other flatfishes and some teleosts. The summer flounder was unusual in having a long lipid uptake phase (oocyte diameter up to 301 μm) prior to any indication of vitellogenin (yolk protein) uptake. This information will be useful in the construction of an updated maturity schedule for the wild population.

Seasonal Variations and Maturity Stages in Relation to Differences in Serum Levels of Gonadal Steroids, Vitellogenin, and Thyroid Hormones in the Common Dentex (Dentex dentex)

Seasonal variations in serum concentrations of 17β-estradiol (E2), vitellogenin (Vg), testosterone (T), 11 ketotestosterone (11-KT), and thyroid hormones (T4, l-thyroxine; and T3, 3,5,3′-triiodo-l-thyronine) were investigated during the first, second, and third reproductive cycles in intensively reared populations of common dentex, Dentex dentex, and correlated with gonadal development and spawning. In females, there were baseline E2 values (<0.10 ng/ml) and negligible Vg concentrations during the postspawning and pregametogenesis period (June to December), and these increased thereafter to peak during the spawning period. Maximum T3 and T4 serum concentrations were found around spawning. There was a positive correlation during vitellogenesis and final maturation between Vg and T3 (r2=0.366). In addition, Vg and T3 concentrations were statistically higher in the stages of vitellogenesis and final maturation than at the other stages (P<0.001). Minimum T3 and T4 concentrations (October) coincided with the decrease in water temperature and the associated decrease in the daily feeding rate and the specific growth rate. In males, as in females, seasonal changes in serum levels of T and 11-KT were well correlated with gonadal development. The presence of males in the stage of completed spermiogenesis in December coincided with the surge in both androgens and this increase lasted until the end of the spawning period. There were no significant differences in serum T3 and T4 levels among the maturity stages. The observed seasonal changes in serum gonadal steroids and Vg reflected the pattern of oocyte development and the spawning behavior of common dentex and were typical of the patterns described in most multiple spawners studied to date. Thyroid hormones may enhance early ovarian development and stimulate vitellogenesis in female dentex.

Maternal pineal gland participates in prepubertal rats' ovarian oocyte development

Sexual maturation is a very complex phenomenom that it is mediated by the ontogeny of the hypothalamus-pituitary-gonadal axis during intrauterine life. The maternal pineal gland can affect fetal development because the main pineal hormone, melatonin, crosses the placental barrier. We found that melatonin treatment during gestation in the rat produced delayed sexual maturation of the female offspring. The present work was undertaken to study the maturational stage of oocytes of prepubertal female rats when their mothers were either pinealectomized (PIN-X) or treated with melatonin (MEL) during pregnancy. Three groups of female Wistar rats were used: control, PIN-X, and those treated (250 micrograms/100 g body weight) with melatonin throughout pregnancy. Ovaries of 25-30- and 34-day-old female offspring were studied during the prepubertal phase. Morphometric studies of semithin sections (1 micron) of the ovaries were performed. Oocyte, nuclear, and nucleolar volumes were calculated by a computer-assisted program (M.I.P.) in an image analyzer Kontron. Regularity of the structures was determined by the frequency distributions of circular and regular form factors. Cytometric study of oocyte structure showed a frequency distribution of regular and circular form factors, with a high degree of regularity very close to unit. Cellular and nuclear volumes of follicular oocytes showed a transitory increase at 30 days of age in control rats. In the offspring of MEL-treated mother rats, a pattern of oocyte development showed significantly lower nuclear and nucleolar volumes at 30 days of age than at the other time points and significantly lower cellular volume at 34 days of age than at 25 days of age. In the offspring of PIN-X mother rats, no significant differences in oocyte cellular volumes were observed throughout prepubertal development, but we observed a significantly higher nuclear volume at 25 days of age and a significantly lower nucleolar volume at 30 days of age. These findings show that the maternal pineal gland participates in cellular and nuclear volumes of prepubertal oocyte development. Melatonin treatment during pregnancy resulted in a redirected postnatal oocyte development.

Pattern of sea bass oocyte development after ovarian stimulation by LHRHa

The cyclic pattern of oocyte development in the sea bass, Dicentrarchus labrax L., was studied after induction of spawning by two injections, 24 h apart, of a luteinizing hormone releasing‐hormone analog (LHRHa) administered at the end of vitellogenesis. The first difference in the developmental stage of the ovary and in the size‐frequency distribution of oocytes between the LHRHa treated group and the control group, was detected 32 h after the first injection, the LHRHa group showing a higher proportion of the 900 μm diameter oocyte class (maturing oocytes) (P&lt;0.01). At 48 h LHRHa‐treated females showed an increase in the 1000 and 1100 μm classes (maturing oocyte and ovulated eggs) (P&lt;0.01) and at 72 h these females exhibited a bimodal pattern, reaching the highest proportions in the 1100 (27.4%) and the 600 (14.7%) μm classes (ovulated eggs and advanced vitellogenic oocytes, respectively). Bimodal distributions were present in 80% of the LHRHa‐treated females. Once oocyte final maturation was triggered by LHRHa the time needed for ovulation was about 48 h and the interval between consecutive ovulations and spawnings seemed to be 48–72 h.

Biology of the western pygmy perch,Edelia vittata, and comparisons with two other teleost species endemic to south-western Australia

This paper provides data on the movements, spawning times and localities, size and age composition, growth and diet of the western pygmy perch,Edelia vittata, in a south-western Australian river. The results of this study are compared with those recorded previously for two other locally endemic species (Galaxias occidentalis andBostockia porosa) to ascertain the extent to which these three species utilise the same resources, and whether they are similarly adapted to the highly seasonal flow regime. A total of 3396Edelia vittata was collected with a 3 mm mesh seine net from the Collie River in south-western Australia at 3–6 week intervals over a period of 26 months. During the winter, fish moved from the river into either adjacent flood waters or tributary creeks. The trends shown by gonadosomatic indices, oocyte growth and prevalence of post-ovulatory follicles, demonstrate that spawning takes place between late winter and late spring (July–November). Sexual maturity was attained by both sexes at the end of the first year of life. Although 99% of the fish belonged to the 0+, 1+ and 2+ age classes, representatives of the 3+, 4+ and 5+ age classes were also caught. The respective von Bertalanffy growth curve parameters for L∞, K and t0 were 54.9, 1.178 and -0.210 for males and 57.9, 1.124 and -0.198 for females. At the end of the first and second years of life, the lengths predicted from the von Bertalanffy growth equations were 42 mm (≡ 0.8 g) and 51 mm (≡ 1.4 g) for males and 43 mm (≡ 0.9 g) and 53 mm (≡ 1.6 g) for females. The diet consisted of a wide range of small benthic invertebrates, especially dipteran larvae, ostracods and cyclopoid copepods. The peak time, duration and predominant locality of spawning, the time of day when maximum activity occurs and the diet ofEdelia vittata differs from those previously recorded forGalaxias occidentalis andBostockia porosa. These differences would be likely to minimize any potential competition amongst these three species. The growth rates, age at first sexual maturity and pattern of oocyte development also differ amongst the three species.

Aspects of the reproductive biology of the bass, Dicentrarchus labrax L. II. Fecundity and pattern of oocyte development

The European bass, Dicentrarchus labrax L., in common with most temperate marine teleosts, exhibits a distinct seasonal reproductive cycle. Its reproductive strategy is characterized by a high absolute fecundity (2‐25 × 105), both absolute and relative fecundity increasing with size and age. The cyclic pattern of oocyte development has been determined by histology and from oocyte size frequency analysis. Results show that the bass exhibits group‐synchronous oocyte development and is a ‘fractional spawner’, i.e. it spawns a number (3–4) of discrete clutches in quick succession, successive clutches containing fewer oocytes. All oocytes which are recruited into the secondary growth phase (&gt; 110 μrn) are either spawned that season or become atretic, i.e. no secondary oocytes are held over for the subsequent reproductive season.

Influence of the Cerebral Neuroendocrine System on Neutral Lipid Synthesis During Oogenesis inNereis diversicolor(Annelida Polychaeta)

Summary Addition of prostomia or brain secretions into the culture medium increases the synthesis of neutral lipids (NL) and especially of triglycerides by isolated oocytes of Nereis diversicolor. In parallel, after incorporation of 3H-glycerol, NL synthesis of oocytes from worms decerebrates 3 or 8 days previously is lower than in oocytes from control worms. This decrease is consistent whatever the incorporation lasts. In the discussion, we compare these results with those obtained in another species of Nereidae, Perinereis cultrifera, in which decerebration is not followed by a decrease in NL synthesis. These differences may be related to a different pattern of oocyte development under anhormonal conditions.

Studies on the mode of ovarian maturation and spawning of the landlocked ayu in Lake Biwa. III. On the ovarian maturation and spawning of the landlocked large type ayu Plecoglossus altivelis in Lake Biwa.

Aspects of the reproductive biology of the landlocked large type ayu Plecoglossus ahivelis in Lake Biwa, “ooayu”, were investigated from August to October in 1980. In more than half the number of ovaries after the first spawning, degeneration of developing eggs or collapse of the whole ovary was observed. Hence, after the first spawning, a small number of fish seemed to attain the second maturation. All the fish which attained the second maturation were skinny and half of them had lower gonadosomatic indexes and smaller number of mature eggs compared to those in the first maturation. No significant differences of egg diameter for various maturation stages of egg were indicated between the dwarf type ayu, “koayu”, and the ooayu. The pattern of oocyte development of ooayu showed the “trimodal twice spawning type”. Resting ocoytes in the peri-nucleolus stage which are usually present all the year round in the general serial spawners, were not observed in the ovary of ooayu after the second spawning. This fact suggests that ooayu have an inherent regulating mechanism of oocyte development adapted to the annual life of the fish, i.e. they discharge all oocytes in a single spawning season in spite of their serial spawning habit.