Reproductive traits of the small Patagonian octopus Octopus tehuelchus

This study evaluated the reproductive features of Octopus tehuelchus in three coastal environments of San Matías Gulf (Patagonia). Monthly samples of O. tehuelchus were used to estimate size at maturity, compare seasonal changes in oocyte size frequency distributions between sites as well as oocyte number and size between female maturity stage and sites. Females in Islote Lobos had a smaller size at maturity than females in San Antonio Bay and El Fuerte, probably as a consequence of a generally smaller body size. Males in San Antonio Bay were smaller at maturity than females. O. tehuelchus is a simultaneous terminal spawner. Fecundity (expressed as number of vitellogenic oocytes in ovary) was lower in Islote Lobos, and an increase in oocyte number in relation to female total weight was found. Females in San Antonio Bay had the largest oocytes, which may indicate higher energy reserves for the embryo and therefore higher juvenile survival. There was a close relationship between reproduction, growth and condition, represented as size at maturity, number and size of vitellogenic oocytes and period of maturity and spawning. Given the local variation in some reproductive features of O. tehuelchus, studies should focus on the environmental factors, which bring about this variation, and on how it affects the dynamics of local populations.     

Variations in Fecundity and Egg Size of Female Nile Tilapia, Oreochromis niloticus, from Man-made Lakes of Côte D'Ivoire

Fecundity and oocyte size of Oreochromis niloticus females were studied over a period of two annual cycles in six small agropastoral and three large hydroelectric reservoirs of Côte d'Ivoire. Important differences in fecundity and oocyte size were observed among populations and within the same population between successive years. An inverse correlation was found between size and number of oocytes produced by females. This inverse relationship occurred for a constant spawn weight during the first year of study, but not during the second year. Monthly mean residuals of regressions between fecundity and female body weight have shown a seasonal variation in fecundity. The peak of fecundity corresponded with the maximum resource availability and the flooding eminence, which may have a great impact on parents and offspring fitness.     

Relationships between broodstock condition,oocyte quality,and 24 h D-larval survival during the spawning season of the pullet carpet shell Venerupis corrugata (Gmelin, 1791)

Abstract

Venerupis corrugata is commercially exploited in Europe. Over-fishing and recruitment failure is causing the decline of its populations and stock sustainability. Knowledge of this species reproduction is paramount to establish hatchery production of juveniles for restoring natural beds. This work aimed to find a relationship between broodstock condition, oocyte quality, and viability of 24 h D-larvae. Adult specimens were induced to spawn by thermal stimulation. From each female, oocytes were taken for biochemical analyses (proteins, total lipids, and carbohydrates), and the remaining oocytes were fertilized. The 24 h D-larval yield was calculated after embryo incubation. Spawning in the hatchery with ‘wild’ broodstock was possible for a long period, however, subsequent larval viability varied according to oocyte quality. Two distinct periods of spawning were recorded: in January/March, with a higher number of oocytes released, and in June/July with a lower response to the spawning stimulation, however with greater success in 24 h D-larval survival. The condition index of broodstock and the total lipids of oocytes released can be used as benchmarks for estimating the success of D veliger larvae.     

Reproduction mode of European Bitterling (Rhodeus amarus,Bloch, 1782) determined through rapid oocyte counts and size determination using digital imaging

This study focuses on assessing the reproduction mode of an important model species for evolutionary and behavioural ecology by using digital image analysis: the European bitterling Rhodeus amarus (Bloch, 1782). Specifications of mode of reproduction were determined using oocyte size distribution, seasonal dynamics in mean oocyte diameter and total number of oocytes in ovary samples gained from April to July 2007. The rapid oocyte count was enabled by using lucia image analysis software, which also provided measurement and colour estimations of oocytes. Bitterling ovaries showed features typical for indeterminate spawners, i.e. a continuous distribution of oocyte size over the reproductive season and recruitment of new pre‐vitelogenic oocytes in the second half of the reproductive season. These results are consistent with the view that the European bitterling is a batch spawning fish with indeterminate fecundity.     

The effect of oocytic atresia on fecundity estimates of the rabbit fishSiganus sutor (Pisces: Siganidae) of Kenyan marine inshore waters

In the strongly group-synchronized oocyte development ofSiganus sutor (Valenciennes, 1835) the group of oocytes to be released in the following spawning, is identified. The smallest size of oocyte belonging to this group was identified by the presence of cytoplasmic vacuoles in oocytes in histological sections. These vacuolated oocytes corresponded to oocytes of 150 µm diameter obtained by treatment with Gilson's fixative. The mean number of such oocytes in stage 4 (late developing) ovaries was found to be 638 000. The proportion of these oocytes removed by atresia before spawning was determined on histological sections to be 5%. The corrected estimate of mean fecundity was thus 606 000 oocytes per spawning.     

Reproductive effort,fecundity and energy allocation in Marphysa sanguinea (Polychaeta: Eunicidae)

Summary

Reproductive effort in terms of fecundity and energy allocation was studied in the iteroparous and long lived polychaete Marphysa sanguinea. Both measures show great variability. Fecundity varied from 8500 to 24300 oocytes; no linear relationship was found between oocyte number and jaw length whereas a direct relationship was established between oocyte number and wet body weight. The energy content of germinal and somatic tissues was determined by differential scanning calorimeter (DSC). The reproductive effort for a single reproductive event was calculated according to the formula: RE = E_G/(E_G + E_S) where E_Gis the total energy of the germinal tissues and E_S is the total energy of the somatic tissues. The lack of correlation between reproductive effort and size index strongly suggests that reproductive allocation does not increase with age. The reproductive effort ranged from 0.04 to 0.19 with a mean value of 0.120.     

Effects of Ration on Growth and Reproductive Investment from Larva to Sexual Maturity in the Female Cyprinid Minnow,Tanichthys albonubes

Somatic growth and reproductive investment in female Tanichthys albonubes (Cyprinidae) individually cultured at the laboratory from larva to sexual maturity were examined under low, medium, and satiation food rations. All the 72‐day post‐hatch fish reached sexual maturity under all rations. The standard length, wet body mass, dry ovarian mass, dry liver mass, condition factor, energy content, and number of vitellogenic oocytes were all increased with ration levels. However, food conversion efficiency decreased with ration. There were no significant differences in total number of oocytes per female between rations. The species is a continuous batch‐spawner. The size‐frequency distributions of oocyte diameters showed a continuous pattern, ranging from 0.03 to 0.70 mm, at different rations. The proportion of energy intake allocated to growth decreased with ration levels. Only 3.29–4.60% of energy intake was stored in the ovary. These biological and energetic characteristics allow this fish to reach first maturity with low food intake, although it produced fewer vitellogenic oocytes at lower rations. This property enables T. albonubes survive in its native habitats where food is not only scarce, but also variable temporally and spatially. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Surface alterations of the bovine oocyte and its investments during and after maturation and fertilization in vitro

Surface characteristics of the bovine oocyte and its investments before, during, and after maturation, and fertilization in vitro were evaluated by scanning electron microscopy (SEM). Oocyte diameters were also measured during SEM analysis of the oocyte. The cumulus cells manifested a compact structure with minimal intercellular spaces among them in the immature oocytes. These became fully expanded with increased intercellular spaces after maturation in vitro, but contracted again after fertilization. The zona pellucida (ZP) showed a fibrous, open mesh-like structure in the maturing and matured oocytes. The size and number of meshes on the ZP decreased dramatically after fertilization. The vitelline surface of immature oocytes was characterized by distribution of tongue-shaped protrusions (TSPs) varying in density. After 10 and 22 hr of maturation incubation, oocyte surface microvilli (MV) increased to become the predominant surface structure, and TSPs decreased substantially. The vitelline surface of fertilized oocytes (at 6 and 20 hr) was similar to that of the matured oocytes, but unfertilized oocytes had less dense MV than did fertilized oocytes (at 20 hr). The diameter of the oocytes decreased from 99 to 80 μm during maturation and increased to 106 μm after insemination (P < 0.05). Membrane maturation was characterized by surface changes from a TSP-predominant pattern to a MV-predominant pattern. Thus, the bovine oocyte maturation process was found to involve the expansion of cumulus cells and the maturation of the ZP, which changes dramatically upon fertilization. Also, volumetric changes occurred in ooplasm processed for SEM following oocyte maturation and insemination. © 1994 Wiley-Liss, Inc.     

Effects of culturing bovine oocytes either singly or in groups on development to blastocysts

In vitro maturation, fertilization and culture (IVM/IVF/IVC) of cattle oocytes from individual cows requires adapting existing culture protocols so that small numbers of oocytes can be cultured. The culture of single oocytes is desirable for correlating the relationship between follicular properties with oocyte developmental competence or for facilitating ovum pick-up procedures. In Experiment 1 we compared group and single culture under cell-free conditions on embryo development; significantly higher (P<0.001) rates of cleavage (66.4 vs 47.6%) and blastocyst formation (7.5 vs 0.5%) were observed in the group cultured oocytes. In Experiment 2 we compared group and single oocyte co-culture with granulosa cells. Although there was no effect of oocyte number on the percentage cleaving (73.1 vs 66.6%), there were significantly higher blastocyst yields (37.4 vs 10.1%) and blastocyst cell numbers (91.6 vs 66.2) in group-cultured oocytes. In Experiment 3 we examined the effect of group size (1, 5, 10, 20 and 40 oocytes) in a co-culture system using granulosa cell monolayers. The results show a difference in cleavage rates between the single cultured oocytes (66.8%) and each group of cultured oocytes, with the highest cleavage rate (81.5%) obtained in the 20-oocyte group. The blastocyst yield from both cleaved and total oocytes showed that group culture of 20 or 40 oocytes resulted in the highest number of blastocysts (32.5%), with smaller group sizes yielding significantly (P<0.05) fewer blastocysts. In Experiment 4 we examined the effects of co-culture on the development of single vs group-cultured oocytes. The results showed no significant difference (P>0.05) in the cleavage rate between single and group culture systems. No blastocysts were formed with single oocytes cultured without monolayers, while the blastocyst formation rate for those co-cultured with granulosa cells was 12.4%. Blastocyst formation was significantly higher (P < 0.006) in group co-culture on monolayers (24.2 vs 8.5%). These data indicate that oocytes cultured in groups are developmentally more competent and suggest that for optimum development oocytes need some undefined paracrine activity that is absent from the culture medium in addition to coculture with granulosa cells, which enhances development to the blastocyst stage of both group and singly cultured oocytes.     

Reproductive development of northern and southern strains of plum curculio (Coleoptera: Curculionidae)

Laboratory-reared southern and field-collected northern strains of plum curculio, Conotrachelles nenuphar (Herbst), were sampled to examine the relationship between degree-day (DD) accumulation and female reproductive development, as measured by mating status, oocyte size, and number of oocytes. The overall goal was to generate an objective degree-day model for predicting damage potential that could be applied to various host commodities rather than relying on separate biofix models for each crop. Adult beetles were dissected to measure mating status, maximum oocyte size, and number of oocytes. Southern strain beetles reared at 25 degrees C initiated mating 9 d after eclosion and did not require mating to induce oocyte development. By 20 d posteclosion, unmated females had significantly higher egg loads compared with mated females of the same age. Logistic regression analysis suggests that southern and northern strain beetles had a stable maximum oocyte length of 62 and 72 microm, respectively. Northern strain females mated after overwintering; with approximately 95% of the female population mated after 134 DD (base 10 degrees C), which is before fruit set in many host crops. Oocyte size was the only measured parameter of field reproductive progress that could be linked with confidence to degree-day accumulation. The other two parameters do not share an exclusive relationship with degree-days. Rapid assessment of field-caught female reproductive status could assist in determining the potential for plum curculio damage in high-value commodities and allow for more informed control decisions.     

Oocyte retrieval and histological studies of follicular population in buffalo ovaries

Ovaries (N = 250) from slaughtered buffaloes were collected to study follicular population and compare methods of oocyte retrieval. The number and size of surface follicles were recorded and grouped into different categories. Different sized follicles in relation to oocyte diameter were studied histologically. Yield of oocytes per ovary were less (P < 0.05) from ovaries bearing a corpus luteum (CL). Techniques used for oocyte recovery included slicing, follicle puncture and aspiration. The oocyte recovery rate was greatest (P < 0.05) using slicing. The average number of visible surface follicles was 5.20 ± 0.97 with mean numbers of 2.5, 1.2, 0.82 and 0.62 per ovary for follicles sized 4, 8, 12 and 12 mm respectively. Histological studies revealed large numbers of primordial follicles in prepubertal and atretic follicles in senile buffaloes. They also established a biphasic relationship of growth between oocyte diameter and follicular size.     

The ploidy of in vitro matured bovine oocytes is related to the diameter

The aim of the present study was to investigate a possible relationship between bovine oocyte diameter and the ploidy after maturation in vitro. The cumulus-oocyte-complexes (COCs) were collected by slicing slaughterhouse ovaries and were matured in vitro in standard conditions. Oocytes were collected separately from each ovary and then processed in groups according to their origin. After maturation, the inside zona pellucida diameter of each cell was measured and cytogenetic slides were made. Four size categories were distinguished: <110, 110-115, 115-120 and >120 microm. Altogether, 600 oocytes derived from single ovaries of 50 donors were measured and cytogenetically analyzed. The diploid chromosome number (2MII) was found for 8.4% of oocytes (36/427) and for 44% of donors (22/50). The observed number of 2MII cells varied between 1 and 6 per donor. The size of secondary oocytes with unreduced chromosome numbers was significantly smaller (P < 0.01) than the haploid ones. We conclude that bigger oocytes underwent normal meiotic division, whereas their smaller counterparts tended to follow an abnormal path of maturation.     

Metabolism of glucose,pyruvate, and glutamine during the maturation of oocytes derived from pre‐pubertal and adult cows

The aim of the study was to compare the energy metabolism of oocytes from pre‐pubertal (2 to 3 months) and adult cows during maturation, to identify the cause of poor developmental potential in many pre‐pubertal oocytes. The metabolism of [5‐³H] glucose, [2‐¹⁴C] pyruvate, and [G‐³H] glutamine was measured at 0 hr, 12 hr, and 24 hr maturation. Oxidative metabolism was important during maturation of oocytes from both pre‐pubertal and adult cows, with pyruvate metabolism peaking at 12 hr and glutamine metabolism increasing linearly and peaking at 24 hr. Peak oxidative metabolism was significantly lower in oocytes from pre‐pubertal animals, for both pyruvate and glutamine (P < 0.05). Glucose metabolism increased significantly during oocyte maturation in both groups (0hr to 24 hr). Glucose metabolism was significantly lower in oocytes from pre‐pubertal cows at 12 hr (P < 0.05). Oocytes from pre‐pubertal animals were significantly smaller than oocytes from adult cows at 0 hr, 12 hr, and 24 hr maturation (P < 0.05). When metabolic rates were corrected for oocyte volume, there were no significant differences in substrate metabolism between oocytes from pre‐pubertal and adult cows. There was however, a delay in the increase in glucose metabolism in pre‐pubertal oocytes 0 hr to 12 hr maturation. Germinal vesicle breakdown was slower in oocytes from pre‐pubertal animals with more oocytes still at the germinal vesicle stage approximately 5 hr post‐aspiration, compared to oocytes from adult cows (P < 0.05). By 24 hr, development to metaphase II was equivalent for pre‐pubertal and adult oocytes. This study identified differences in energy metabolism, oocyte size, and meiotic progression between the oocytes from pre‐pubertal and adult cows that may account for the poor developmental potential of many pre‐pubertal oocytes. Mol. Reprod. Dev. 54:92–101, 1999. © 1999 Wiley‐Liss, Inc.     

Influence of follicle size on the penetrability of immature pig oocytes for homologous in vitro penetration assay

In order to improve the performance of homologous in vitro penetration (hIVP) assays using immature oocytes to assess the penetrating ability of boar sperm, the present study was designed to evaluate the influence of oocyte and follicle size on the penetrability of immature pig oocytes obtained from slaughterhouse ovaries. Nonatretic antral follicles were isolated, measured with a computerized image analysis system and grouped according to their diameter: Group 1 (0.40-0.99 mm), Group 2 (1.00-2.19 mm), Group 3 (2.20-2.79 mm), and Group 4 (2.80-6.50 mm). After sperm coincubation and before penetrability evaluation, the immature oocytes were classified into four size categories according to their diameter excluding zona pellucida: <105, 105-109, 110-114, and > or =115 microm. As regards follicle size, the highest viability and penetrability were obtained with oocytes from follicles >2.20 mm (P>0.05). Regarding oocyte size, significant differences (P<0.05) were observed for all parameters evaluated between oocytes with a diameter above or below 110 microm. However, our results revealed that such differences were due to follicle size rather than oocyte diameter, since oocytes with the same diameter but from different follicle size groups showed different penetration rates. With increasing follicle size, the percentage of penetrated oocytes increased (P<0.05). Finally, our results showed that the greater penetrability of immature oocytes from larger follicles is not due to variations in the thickness of the zona pellucida. There were no significant differences in zona pellucida thickness between oocytes from the four follicular size groups. In summary, these results indicate that follicle size directly affects the penetrability of immature pig oocytes used in hIVP.     

Release of sICAM-1 in Oocytes and In Vitro Fertilized Human Embryos

Background

During the last years, several studies have reported the significant relationship between the production of soluble HLA-G molecules (sHLA-G) by 48–72 hours early embryos and an increased implantation rate in IVF protocols. As consequence, the detection of HLA-G modulation was suggested as a marker to identify the best embryos to be transferred. On the opposite, no suitable markers are available for the oocyte selection.

Methodology/Principal Findings

The major finding of the present paper is that the release of ICAM-1 might be predictive of oocyte maturation. The results obtained are confirmed using three independent methodologies, such as ELISA, Bio-Plex assay and Western blotting. The sICAM-1 release is very high in immature oocytes, decrease in mature oocytes and become even lower in in vitro fertilized embryos. No significant differences were observed in the levels of sICAM-1 release between immature oocytes with different morphological characteristics. On the contrary, when the mature oocytes were subdivided accordingly to morphological criteria, the mean sICAM-I levels in grade 1 oocytes were significantly decreased when compared to grade 2 and 3 oocytes.

Conclusions/Significance

The reduction of the number of fertilized oocytes and transferred embryos represents the main target of assisted reproductive medicine. We propose sICAM-1 as a biochemical marker for oocyte maturation and grading, with a possible interesting rebound in assisted reproduction techniques.     

Gamete number and size correlate with adult size in the egg parasitoid Trichogramma euproctidis

In parasitoids, the size of the adult is influenced by the size and quality of the host in which it develops. Body size is generally positively correlated with several adult fitness proxies (fecundity, longevity, and mating capacity). The initial resources available to an individual can influence gamete production (sperm and oocytes), and the number and quality of gametes produced directly influence the expected fitness of both males and females. Gamete production in relation to adult body size was quantified in Trichogramma euproctidis (Girault) (Hymenoptera: Trichogrammatidae), a short‐lived egg parasitoid of lepidopteran species. To avoid host quality variation, male and female parasitoids of different body sizes were produced using superparasitism by allowing mated and virgin female parasitoids to oviposit on Trichoplusia ni Hübner (Lepidoptera: Noctuidae) eggs. Seminal vesicles and ovaries of their offspring were dissected to count oocytes and to measure sperm length and oocytes volume. Tibia length was also measured to estimate body size. The number of oocytes, volume of oocytes, maternal investment index [= (number of oocytes × mean volume of oocytes)/10 000] and sperm length were all significantly positively correlated to body size. These results show that initial resources acquired during larval stage induce phenotypic plasticity in gamete production in both male and female T. euproctidis. Whereas number of sperm and oocytes can influence the fitness of males and females through increased mating capacity and fecundity, variation in gamete size (sperm length and oocyte volume) could also affect the fitness of an individual through sperm and larval competition.     

Fecundity regulation by atresia in turbot Scophthalmus maximus in the Baltic Sea

Down‐regulation of fecundity through oocyte resorption was assessed in Baltic Sea turbot Scophthalmus maximus at three locations in the period from late vitellogenesis in April to spawning during June to July. The mean ± s.d . total length of the sampled fish was 32·7 ± 3·1 cm and mean ± s.d . age was 6·2 ± 1·5 years. Measurements of atresia were performed using the ‘profile method’ with the intensity of atresia adjusted according to the ‘dissector method’ (10·6% adjustment; coefficient of determination was 0·675 between methods). Both prevalence (portion of fish with atresia) and intensity (calculated as the average proportion of atretic cells in fish displaying atresia) of atresia were low in prespawning fish, but high from onset of spawning throughout the spawning period. Atretic oocytes categorized as in early alpha and in late alpha state occurred irrespective of maturity stage from late prespawning individuals up to late spawning fish, showing that oocytes may become atretic throughout the spawning period. Observed prevalence of atresia throughout the spawning period was almost 40% with an intensity of c. 20%. This indicates extensive down‐regulation, i.e. considerably lower realized (number of eggs spawned) v. potential fecundity (number of developing oocytes), suggesting significant variability in reproductive potential. The extent of fecundity regulation in relation to fish condition (Fulton's condition factor) is discussed, suggesting an association between levels of atresia and fish condition.     

Morphologic comparison of ovulated and in vitro–matured porcine oocytes,with particular reference to polyspermy after in vitro fertilization

This study was conducted to evaluate morphologic differences in pig oocytes matured in vivo and in vitro, with particular reference to the potential relationship between oocyte morphology and the occurrence of polyspermy after in vitro fertilization (IVF). In vivo–matured oocytes were surgically recovered from the oviducts of gilts with ovulated follicles on day 2 of estrus, and in vitro–matured oocytes were obtained by culturing follicular oocytes in a oocyte maturation system that has resulted previously in production of live offspring following IVF. Comparisons were made of the cytoplasm density, the diameter of oocytes with or without zona pellucida (ZP), the thickness of the ZP, the size of the perivitelline space (PVS), ZP dissolution time, and cortical granule (CG) distribution before IVF, and CG exocytosis and polyspermic penetration after IVF. Oviductal oocytes have clear areas in the cytoplasm cortex, while in vitro–matured oocytes have very dense cortex. The diameter of ovulated oocytes with ZPs was significantly (P < 0.001) greater than that of in vitro–matured oocytes. However, no difference was observed in the diameter of the oocyte proper. Significantly (P < 0.001) thicker ZPs and wider PVSs were observed in the ovulated oocytes. The ZPs of ovulated oocytes were not dissolved by exposure to 0.1% pronase within 2 hr, but the ZPs of in vitro–matured oocytes were dissolved within 131.7 ± 7.6 sec. The ZPs of ovulated oocytes, but not of in vitro–matured oocytes, were strongly labeled by a lectin from archis hypogaea that is specific for β-D-Gal(1–3)-D-GalNAc. Polyspermy rate was significantly (P < 0.01) higher for in vitro–matured oocytes (65%) than for ovulated oocytes (28%). CGs of oviductal oocytes appeared more aggregated than those of in vitro–matured oocytes. Most of CGs were released from both groups of oocytes 6 hr after IVF regardless of whether they were polyspermic or monospermic oocytes. These results indicate that in vitro–matured and in vivo–matured pig oocytes possess equal ability to release CGs on sperm penetration. Unknown changes in the extracellular matrix and/or cytoplasm of the oocytes while in the oviduct may play an important role(s) in the establishment of a functional block to polyspermy in pig oocytes. Mol. Reprod. Dev. 49:308–316, 1998. © 1998 Wiley-Liss, Inc.