Oocyte Size Research Articles

Половая структура поселений двустворчатого моллюска Macoma calcarea (Gmelin, 1791) в районах с разным гидрологическим режимом

The influence of changes in environmental conditions on the reproductive cycles of benthic organisms (sexual structure, size of puberty, stages of gonad maturity, oocyte size) of the bivalve mollusk Macoma calcarea in the western part of the Spitsbergen archipelago (Grenfjord Bay) and the eastern part of the Barents Sea (coastal archipelago) was studied New Earth). In a settlement of M. calcarea in the warmer waters of Grenfjord, intensive reproductive processes were observed. In this area, females reach sexual maturity with a shorter shell length than males and individuals from other areas of the Barents Sea; In terms of sex ratio, females dominate over males, and a large number of juveniles are noted. Females at the spawning stage were found only near Novaya Zemlya. The diameter of the oocytes varied from 30 to 200 µm depending on the stage of maturity. In the mollusks M. calcarea, the breeding season is extended in time in both study areas.

Tracking gonadal development in fish: An in vivo MRI study on polar cod, Boreogadus saida (Lepechin, 1774).

Magnetic resonance imaging (MRI) was applied to determine the sex of polar cod (Boreogadus saida Lepechin, 1774) (Actinopterygii: Gadidae) and to follow the gonadal development in individual animals over time. Individual unanaesthetised fish were transferred to a measurement chamber inside a preclinical 9.4T MRI scanner and continuously perfused with aerated seawater. A screening procedure at an average of 3.5h, consisting of a set of MRI scans of different orientations, was repeated every 4 weeks on the same set of reproducing B.saida (n= 10) with a body length of about 20 cm. Adapted multi-slice flow-compensated fast low-angle shot (FcFLASH) and rapid acquisition with relaxation enhancement (RARE) protocols with an in-plane resolution of 313 μm and an acquisition time of 2.5min were used to visualise the morphology of various organs, including the gonads within the field of view (FOV). The MR images provided high resolution, enabling specific sex determination, calculation of gonad volumes, and determination of oocyte sizes. Gonad maturation was followed over 4 months from November 2021 until shortly before spawning in February 2022. The gonad volume increased by 2.3-25.5% for males and by 11.5-760.7% for females during the observation period. From October to February, the oocyte diameter increased from 427 μm (n= 1) to 1346 ± 27 μm (n= 4). Interestingly, individual oocytes showed changes in MR contrast over time that can be attributed to the morphological development of the oocytes. The results fit well with previous literature data from classical invasive studies. The presented approach has great potential for various ecophysiological applications such as monitoring natural or delayed development of internal organs or sex determination under different environmental conditions.

Influence of nutrition during previtellogenesis on the follicular development in the Asian Tiger mosquito, Aedes albopictus (Skuse) (Diptera: Culicidae).

Dengue fever poses a global public health threat, with 2.5 billion people at risk of infection each year. Because the Aedes albopictus is the primary vector of dengue, it is closely monitored and handled. The efficiency of Dengue eradication is strongly dependent on understanding a female mosquito's physiological age. This study addresses key entomological issues about the impact of previtellogenic nutrition on egg production mechanisms. Ovarian development included two distinct periods: previtellogenesis and vitellogenesis. Sugar intake during previtellogenesis influences the size of the blood meal. The major parameter influencing the vitellogenesis process is the presence of a hematophagous feeding event following sugar concentration. Upon subjecting female mosquitoes to sucrose, the ovarian follicles entered the third phase of previtellogenesis. Once females feed on blood following sucrose, ovarian development enters the vitellogenesis, and the oocyte cytoplasm reveals that the yolk granules are organized in one or two rows like a crown, increasing oocyte size. Females fed 15% sucrose before a blood meal, have the largest vitellogenic growth, and follicular size, which is seven times greater than those fed water only. Fecundity increased by 78.7% by adding 7% sucrose to the diet. Mitochondria within oocytes increase, most likely due to their transportation from the nurse cells, where the yolk is synthesized. This study describes in detail the histological alterations detected in the ovaries during the previtellogenesis as well as those associated with yolk formation, suggesting that yolk protein deposition in the oocyte is associated with blood meal, independent of sucrose feeding. RESEARCH HIGHLIGHTS: Adult nutrition during previtellogenesis significantly impacts various biological parameters and the physiological age of adults of Aedes albopictus. Female mosquitoes experienced significant growth in vitellogenic development, vectorial capacity, and follicular size after consuming a diet with 15% sucrose before a blood meal.

Identification of ETH receptor and its possible roles in the mud crab Scylla paramamosain

Ecdysis-triggering hormone (ETH) is a neuropeptide hormone characterized by a conserved KxxKxxPRx amide structure widely identified in arthropods. While its involvement in the regulation of molting and reproduction in insects is well-established, its role in crustaceans has been overlooked. This study aimed to de-orphanise a receptor for ETH in the mud crab Scylla paramamosain and explore its potential impact on ovarian development. A 513-amino-acid G protein-coupled receptor for ETH (SpETHR) was identified in S. paramamosain, exhibiting a dose-dependent activation by SpETH with an EC50 value of 75.18 nM. Tissue distribution analysis revealed SpETH was in the cerebral ganglion and thoracic ganglion, while SpETHR was specifically expressed in the ovary, hepatopancreas, and Y-organ of female crabs. In vitro experiments demonstrated that synthetic SpETH (at a concentration of 10−8 M) significantly increased the expression of SpVgR in the ovary and induced ecdysone biosynthesis in the Y-organ. In vivo experiments showed a significant upregulation of SpEcR in the ovary and Disembodied and Shadow in the Y-organ after 12 h of SpETH injection. Furthermore, a 16-day administration of SpETH significantly increased 20E titers in hemolymph, gonadosomatic index (GSI) and oocyte size of S. paramamosain. In conclusion, our findings suggest that SpETH may play stimulatory roles in ovarian development and ecdysone biosynthesis by the Y-organ.

Multifunctional Laser-Induced Graphene-Based Microfluidic Chip for High-Performance Oocyte Cryopreservation with Low Concentration of Cryoprotectants.

Oocyte cryopreservation is essential in the field of assisted reproduction, but due to the large size and poor environmental tolerance of oocytes, cell freezing technology needs further improvement. Here, a Y-shaped microfluidic chip based on 3D graphene is ingeniously devised by combining laser-induced graphene (LIG) technology and fiber etching technology. The prepared LIG/PDMS microfluidic chip can effectively suppress ice crystal size and delay ice crystal freezing time by adjusting surface hydrophobicity. In addition, LIG endows the microfluidic chip with an outstanding photothermal effect, which allows to sharply increase its surface temperature from 25 to 71.8°C with 10s of low-power 808nm laser irradiation (0.4Wcm-2). Notably, the LIG/PDMS microfluidic chip not only replaces the traditional cryopreservation carriers, but also effectively reduces the dosage of cryoprotectants (CPAs) needed in mouse oocyte cryopreservation. Even when the concentration of CPAs is cut in half (final concentration of 7.5% ethylene glycol (EG) and 7.5% dimethyl sulfoxide (DMSO)), the survival rate of oocytes is still as high as 92.4%, significantly higher than the control group's 85.8%. Therefore, this work provides a novel design strategy to construct multifunctional microfluidic chips for high-performance oocytes cryopreservation.

Environmentally-driven variations in reproductive traits in a sandy beach bivalve throughout its geographic range

The yellow clam Amarilladesma mactroides (Reeve, 1854) inhabits the intertidal zone of sandy beaches along the temperate Atlantic coast from Brazil to Argentina (24°-41°S). Over the past decades, there has been a noticeable decline in its abundance, underscoring the importance of understanding their reproductive strategies and phenotypic plasticity for conservation efforts. This study explored large-scale variations in the size at first sexual maturity (SL50), the age at maturity (A50), the vitellogenic oocyte area (VOA), and a reproductive age index (RAI) that combines A50 and the lifespan of each clam population, in relation to local habitat characteristics (e.g., beach morphodynamics) and large-scale environmental variables, such as salinity, sea surface temperature (SST) and chlorophyll-a. Four sandy beach clam populations from Uruguay and Argentina (latitudinal range: 33°45′S - 38°56′S) were sampled monthly between June and August during the reproductive season. SL50 increased linearly with the mean and maximum SST (SSTmean, SSTmax), while VOA and RAI decreased with tidal range and width of intertidal zone, respectively. In beaches that had higher SSTmean and SSTmax, yellow clams reached maturity earlier and spent more than 70% of their lifespan in reproduction. The yellow clam population at the lowest latitude showed the largest oocyte sizes and a shorter lifespan of 3.5 years, while the population at the highest latitude had a longer lifespan (7 years) and the smallest VOA values. Populations at intermediate latitudes showed delayed sexual maturity, a 50–60% investment of their lifespan in reproduction, the longest lifespan (up to 9 years) and intermediate VOA values. The influence of the Rio de la Plata and Bahia Blanca estuaries modified the expected latitudinal gradient in reproductive traits, but local habitat conditions prevailed over large-scale environmental variables as explanatory factors of the reproductive strategy of the yellow clam. Therefore, the species displays phenotypic plasticity in its reproductive aspects to ensure population success.

Oocyte size, early development and hybridisation in two sympatric Chilean species of Fissurella (Mollusca: Vetigastropoda) under laboratory conditions

ABSTRACT Fissurella latimarginata and Fissurella cumingi are two sympatric species found along the southwestern coast of South America. We conducted a comparative analysis of oocyte size and their coats between these species and investigated early development using chemically activated gametes. Additionally, heterologous fertilizations were conducted to assess the presence of a reproductive isolation barrier between the species. The mean diameter of the oocyte and gelatinous coat did not show significant differences between species, but there were differences regarding the vitelline coat. However, the practical utility of this trait as taxonomic character for species discrimination is hindered by variance overlap. Chemical activation of gametes enabled homologous fertilizations, resulting in the production of healthy and viable trochophore larvae. Early development, from fertilisation to hatch of these larvae, takes 28.5–45.5 h in both species. Heterologous fertilizations were also successful, resulting in the hatching of trochophore hybrid larvae, indicating effective interactions between the gametes of both species and viable postzygotic larval development. However, further research should focus on determining if there is asymmetry in gametic compatibility, obtaining veliger larvae, or even more advanced ontogenetic stages.

Cat presumptive zygotes assessment in relation to their development

Abstract The evaluation of oocytes and zygotes, based on their size, shape and morphology, is a valuable tool for predicting subsequent embryo development. While this assessment is non-invasive and made possible with time-lapse monitoring systems, not all the assessment criteria used for zygotes with pale cytoplasm can be used for domestic cat zygotes, which have dark cytoplasm. In this study, feline presumptive zygotes were evaluated for shape, size, and morphology. Measurements were also made of the diameter of the entire zygote, its cytoplasm, and the zona pellucida. Differences in the dataset were assessed using the generalized linear model (GLM) procedure. While there was no relationship between a combination of the tested parameters with the potential for cleavage, blastocyst development, and hatching, the parameters of the shape and size of the entire oocyte, and of the zona pellucida, were related to the development potential. The results presented in this study indicate that the assessment procedure for human zygotes has to be adjusted to be used in the cat model, however the relationship between measurements of the diameter of presumptive feline zygotes and the thickness of zona pellucida with their developmental potential deserves further investigation to optimize assessment of cat presumptive zygotes.

Перебіг гаметогенезу у вузькопалих річкових раків (Astacus leptodactylus Eschscholtz, 1823) в умовах водойм Придніпров’я

Purpose. Detailed study of the stages of reproductive development (oogenesis and spermatogenesis) of crayfish using the example of the narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823 in reservoirs of the Dnieper region. Methodology. The study was conducted during the period of 2022-2023. The material for the study were individuals of the narrow-clayed crayfish A. leptodactilus. A morphometric analysis was performed, after which the crayfish were preserved in an alcohol solution (70% ethanol and 2% glycerol) for the slide of histological cross-sections. Histological slides of crayfish gonads were made in accordance with generally accepted histological methods. The analysis of the cross-sections was carried out using a microscope and a digital camera. Descriptions of the slides were made using atlases of histology of decapods. Findings. It has been found that the gonads exhibited an asynchronous development and were in stages C, D, E, F, with a significant number of oocytes in stage C. The diameter of oocytes in phase D mainly ranged from 195.72 ± 12.43 μm with an area of 38,21 μm². The nucleus had a diameter of 48.14 ± 1.44 μm. In phases E, the size of oocytes reached a diameter of 259.24 ± 76.18 μm and an area of 52,850 ± 5,760 μm². Throughout phase D, the diameter of vacuoles was 18.45 ± 0.86 μm. In phase E, the diameter of vacuoles increased to 26.55 ± 1.24 μm, and as soon as in the transitional phase E–F, vacuoles merged massively with individual non-merging vacuoles having a diameter of 25.22 ± 1.12 μm. At the terminal stage F, oocytes reached definitive sizes and were ready for ovulation. The average size of larvae was 2600 ± 0.093 μm in diameter. The course of spermatogenesis in crayfish males was characterized by synchronous development of gametes. The analysis of sections showed that the area of spermatocytes was 43.14 ± 0.74 μm with a diameter of 7.14 ± 0.23 μm². In turn, the nuclei of spermatocytes had dimensions of 21.64 ± 0.35 μm² and 5.24 ± 0.02 μm in diameter. Originality. A comprehensive analysis of crayfish gametogenesis was conducted for the first time in the zones of the reproductive range of the Dnieper reservoirs. Some features of the stages of oogenesis and spermatogenesis were identified and the impact of the ecological regime on the reproduction of crayfish was studied. Keywords: narrow-clawed crayfish, water bodies, reproduction, ecological state of water bodies, reservoir, eggs, gametogenesis.

Status of the reproductive system of anchovy sprat (Clupeonella engrauliformis, Borodin, 1904) in the Caspian sea

The impact of negative factors on the population of anchovy sprat (Clupeonella engrauliformis, Borodin, 1904) continues, and therefore in recent years there has been a steady downward trend in the abundance and density of the species. Research catches of anchovy sprat are declining. One of the conditions contributing to the population recovery is an optimal, without critical pathologies condition of reproductive system of individuals. The purpose of this work is to study the condition of testes and ovaries of anchovy sprat. According to the histological picture of germ cells it is possible to objectively assess the state of reproductive ability of individuals. The study was carried out using the methods of classical histology. The material was gonads of females and males sampled in the summer of 2023 in the Middle Caspian Sea. According to the results of histological study it was found that gonads have different stages of maturity (II–III, III, IV and V). The presence of direct correlations between maturity indices (gonad weight, gonadosomatic index, maturity coefficient) in individuals of both sexes was found. In females, the size of oocytes of different stages of maturity is described, and the absence of correlation between cell diameter and length and mass of the individual is revealed. Distinctive features of resorption of oocytes of III and IV stages of maturity by such characteristics as shape, color and transparency of the cell are given. The proportion of females with resorbed oocytes (67%) and the average proportion of cells with developmental abnormalities (24%) were noted. The results of this study may contribute to a better understanding of the processes occurring in the reproductive glands of male and female anchovy sprat, which is very important for fish reproduction.

Investigating temporal variability and influence of condition on fecundity and spawning of spotted wolffish (Anarhichas minor) in Icelandic waters

Spotted wolffish (Anarhichas minor) is a poorly understood species which is often captured as part of mixed demersal fisheries across its range. Abundance has declined in many regions and there is a need for greater knowledge on its biology. To improve our understanding of reproduction of A. minor, we investigated inter- and intra- annual differences in fecundity, the influence of condition on fecundity and time scale of ovary development. From 2006 to 2021, 150 females A. minor were sampled in Icelandic waters. Of these females, 73 were also used to estimate spawning time together with an additional 334 females from commercial catch and surveys from 2006 to 2023. Backwards extrapolation of oocyte size indicates that vitellogenesis begins in December and is likely completed after 8–10 months. There was no evidence of either intra- or inter-annual differences in fecundity, indicating that downregulation is minimal and that fecundity of A. minor is stable between years. A positive relationship between oocytes size and fish length was detected, while body condition and hepatosomatic index had only a small influence on fecundity in comparison with weight. There was a negative relationship between length and relative fecundity and the exponent of the fecundity–length relationship was lower than exponent of the weight–length relationship. Therefore, total egg production is likely not proportional to the spawning stock biomass of A. minor, and unusually, total egg production would decrease with increasing proportion of larger fish in the population. The spawning season was estimated to be from middle of August to middle of October with peak of spawning in September.

The Role of Cholesterol during the Ovarian Maturation and Lipid Metabolism of Female Chinese Mitten Crab (Eriocheir sinensis)

In previous study, we found that the cholesterol requirement of Eriocheir sinensis was 0.27%, to further investigate the effects of cholesterol on health status, ovarian maturation, and lipid metabolism of female Eriocheir sinensis broodstock. Two diets containing 0% and 0.25% (actually 0.05% and 0.27%) cholesterol were fed to the female crabs (average weight: 49.21 ± 0.11 g) for 4 months and sampled once a month. The results showed that the body weight (BW), survival rate (SR), meat yield (MY), condition factor (CF), hepatosomatic index (HSI), and gonadosomatic index (GSI) of Eriocheir sinensis were significantly affected by treatment time and compared with the cholesterol deficient group, supplementing cholesterol significantly increased BW, HSI, and GSI (P<0.05). In addition, long-term lack of cholesterol will lead to a significant decrease in the activity of ACP, AKP, and SOD and a significant increase in the content of MDA. The histological results showed that cholesterol significantly increased the volume of oocytes (P<0.05). Further studies found that 0.27% cholesterol significantly increased the transcription levels of vtg and vgr in hepatopancreas and ovaries, which may be the main reason for the increase of oocyte size (P<0.05). When fed with 0.27% cholesterol diet, the contents of nutrients in hepatopancreas and ovaries increased significantly, especially lipids and cholesterol (P<0.05). Through the analysis of mRNA expression level of genes related to lipid metabolism, it was found that cholesterol enhanced the transcription level of genes related to lipid synthesis and transport in hepatopancreas, thereby promoting the accumulation of lipid in the organism. Furthermore, compared with control group, the levels of juvenile hormone (JH), 17β-estradiol (E2), methyl farnesoate (MF), and ecdysone in the organism were significantly increased after feeding a diet with 0.27% cholesterol (P<0.05). In summary, supplementing an appropriate amount of cholesterol in the diet can improve the growth performance of Eriocheir sinensis broodstock, enhance the body’s antioxidant and immune system, and promote the accumulation of nutrients in the ovaries, thereby promoting ovarian maturation.

Exploring AMH levels, homeostasis parameters, and ovarian primordial follicle activation in pubertal infected sheep on a high-protein diet

“Exploring AMH Levels, Homeostasis and Primordial Follicle Activation in Pubertal Infected Sheep on a High Protein Diet “.The first activation wave of ovarian primordial follicles is part of the onset of puberty and fertility. Abomasal helminth infection may cause an undesirable delay in puberty manifestation. Helminth-infected animals demand a higher amount of protein in their diet to repair the damage caused by the parasite in sheep's tissues, replenish the blood losses, and build the host's immune response. Helminths become resistant to drug therapy shortly after being exposed to a new treatment. Besides, there is the possibility of contamination by anthelmintic drugs in ovine products, possibly affecting human health and the environment. This study's objective was to evaluate if ovarian and clinical parameters can be improved by supplementing their diet with protein, offering a more sustainable management approach than relying on anthelmintic usage. We used a 2 × 2 factorial model where eighteen ewe lambs (Ovis aries) between 6 and 7 months old - born to the same ram - were fed one of two diet protein levels (12% or 19%). After 35 days on this diet, they were infected or left uninfected with 10,000 Haemonchus contortus L3 larvae. We evaluated Anti-Mullerian Hormone serum levels, blood cells and biochemical parameters at four different time points. Following 42 days of infection and 77 days on the diet, the lambs had their left ovaries removed, and we examined ovarian morphometrics through histological analysis. The groups Supplemented Protein-Infected(n = 5), Control Protein- Infected(n = 5), Supplemented Protein-Not Infected (n = 4) and Control Protein-Not Infected (n = 4) did not differ in their bodyweight gain. In the factorial ANOVA analysis examining the relationship between plasma protein, diet, and infection, the protein level of the diet showed significance (p = 0.02). Primordial follicle size varied with the interaction between diet and infection (p < 0.05), and oocyte size was affected by the level of protein in the diet (p = 0.047). Additionally, to understand how all homeostasis parameters relate to the primordial follicle and oocyte size, we applied an explanatory linear mixed model. In conclusion, serum AMH levels remained stable despite the infection and variations in diet protein levels, indicating its reliability as a marker for ovarian reserve in pubertal sheep. The number of blood cells, biochemical parameters, and primordial follicle activation were affected by both diet and infection.

Background and common lesions in the female reproductive organs of giant anteaters (Myrmecophaga tridactyla).

The giant anteater (Myrmecophaga tridactyla) is a vulnerable species in South America and is considered endangered or near extinction in Central America. Therefore, studies describing the reproductive characteristics of this species are pivotal for its conservation. Thus, this study aimed to provide a morphological description of the female reproductive tissues of this species. We collected tissue samples from six female giant anteaters and performed gross, morphological, and histochemical analyses. Five adult subjects and one juvenile were included in the study. In the ovary, classifications were made according to the follicle and oocyte sizes: primordial, primary, secondary, early antral, or antral. Typical follicles with a single oocyte surrounded by a simple or stratified layer of cubic epithelium, atretic follicles, corpora lutea, corpora albicans, and ovarian cysts were also observed. No ovarian lesions were observed. By contrast, endometritis, metritis, mucometra, and endometrial cysts were identified in the uterus. Uterine alterations in these subjects were frequent and could affect reproduction.

Implications of big, old, fat, fecund, female fish (BOFFFFs) for the reproductive potential of a demersal teleost stock

The ‘big old fat fecund female fish’ (BOFFFF) hypothesis suggests that larger, older female fish contribute disproportionately more to the reproductive potential of a stock than smaller, younger female fish. As fishing typically differentially removes larger, mature fish, this can negatively impact reproductive potential and impair the recovery of a depleted stock. In this study, the BOFFFF hypothesis was explored quantitatively for the endemic West Australian dhufish (Glaucosoma hebraicum) by estimating the relationships between total length (TL) of females and spawning season duration, spawning frequency and oocyte size. The impacts of these size effects on estimates of reproductive potential of the G. hebraicum stock were also explored using a per-recruit analysis. Larger (900 mm TL), older mature female G. hebraicum were shown to spawn for a longer duration (six versus two months) and on more occasions (155 versus 60 times) than smaller (350 mm TL), younger mature fish, and thus these larger females have higher annual fecundity. Larger, older mature G. hebraicum also spawn, on average, significantly larger oocytes with greater estimated energy content (474.6 μm diameter and 0.234 J versus 379.9 μm and 0.140 J). Due to these size effects, reproductive output of G. hebraicum scales hyperallometrically with fish body mass, rather than isometrically. Not accounting for these size effects in per-recruit analysis resulted in higher estimates of stock reproductive potential and thus stock status. Such overestimates, if used to inform management, have the potential to result in harvest rates being set too high which, in turn, could thus affect stock sustainability.

Seasonal ovarian activity and oocyte size in ovarian follicles of sexually mature gilts

Seasonal ovarian activity and oocyte size in ovarian follicles of sexually mature gilts

Reproductive parameters of Oreochromis mossambicus in Laguna de Los Patos, Cumaná, Venezuela.

A total of 381 specimens of the tilapia Oreochromis mossambicus collected monthly from May 2017 to May 2018 in the Laguna de Los Patos, Cumaná, Venezuela, to evaluate reproductive parameters of this non-native species. Significant differences were found in relation to average height and weight between males and females, with the highest values in males. The sex ratio was 1:1.5 (males:females), which deviates significantly from the expected 1:1 ratio. The mean length of sexual maturity (Lm50) was 18.0 cm in females and 20.1 cm in males, reflecting that females mature at smaller sizes than males. The monthly variations of the gonadosomatic index (GSI) and the stages of sexual maturity show two reproductive peaks during the study, in October 2017 and April 2018, coinciding with the rainy and dry seasons in the region respectively. The condition factor (CF) showed significant differences between months, but not between sexes, with an average of 1.87 in females and 1.84 in males. The average absolute fecundity was 921 ± 604.6 eggs per fish, with a relative fecundity of 8.36 ± 3.09 eggs per gram of fish. Differences in oocyte size in mature females confirm that the species can spawn repeatedly over a period, which is considered an important factor for the establishment of tilapia in non-native environments.

Thermal stress-stimulated ZnO toxicity inhibits reproduction of freshwater crustacean Daphnia magna

Elevated temperatures due to climate change pose a variety of environmental risks to the freshwater ecosystem. At the same time, zinc oxide (ZnO) has become widely used and has entered the freshwater environment. As thermal stress may potentially impact the physicochemical properties of ZnO, its toxicity to freshwater organisms in the face of global warming is poorly understood. The potential effects on reproductive performances, including oogenesis, are of particular concern. In this study, we investigate the reproductive performances and related mRNA abundance of the zooplankton Daphnia magna under conditions of ZnO exposure and heat stress. The results revealed that ZnO and elevated temperature delayed maturity and juvenile production of D. magna. Histological observations indicated that oogenesis was inhibited, and the number and size of oocytes were reduced in the condition of ZnO exposure under heat stress. Eventual offspring in the same treatment exhibited decreased numbers, size, and quality. Congenital juvenile anomalies were increased, such as deformed eye, and impaired antenna and tail spine. Moreover, both ZnO and elevated temperature treatments inhibited expression levels of reproduction-related genes (vtg, EcR and VMO1) and induced the dmrt93b gene involved in the production of male offspring. Furthermore, we found that D. magna tried to cope with ZnO and thermal stress by upregulating hsp90, HIF-1α and HIF-1β. ZnO and heat stress inhibited the reproductive capacity of D. magna, produced deleterious effects on reproduction-associated physiological pathways, and damaged reproductive outcomes.

Condition, Reproductive Fitness, and Fluctuating Asymmetry in Brook Stickleback: Responses to Anthropogenic Runoff

Multiple indicators have been used to assess the degree of exposure of fish to anthropogenic chemicals in their stream habitats. We hypothesized that brook stickleback (Culaea inconstans) in a headwater stream receiving urban and agricultural runoff (South Fork Whitewater River, SFWR) would exhibit poorer condition, reduced reproductive fitness, and a greater left side to right side morphological asymmetry (i.e., fluctuating asymmetry or FA) than fish from a nearby headwater stream with a forested drainage basin (Garvin Brook). Male and female fish were collected from both streams just prior to spawning in 2013–2015. In 2013 and 2014, fish were assessed for overall condition (Fulton’s K), internal measures of condition (hepatosomatic index, HSI) and reproductive fitness (gonadosomatic index [GSI], total oocyte count, and oocyte mass). In 2015, measurements of head length, jaw length, eye diameter, pectoral fin length, and pelvic fin length were made on both sides of each fish for assessing degree of FA. We observed declining condition with fish size, increased liver size, and reduced oocyte counts and oocyte size in female brook stickleback in SFWR relative to those from Garvin Brook. SFWR females had significantly higher FA than Garvin females for all structures assessed, except pelvic fin length. FA also was slightly higher for all structures in SFWR males compared to Garvin males, but differences were not significant. A composite FA index combining all measurements from an individual fish into a single value displayed highly significant differences for female fish (SFWR FA &gt;&gt; Garvin FA), but not for male fish (SFWR FA = Garvin FA). Exposure of brook stickleback to reduced water quality in SFWR during early development appears to increase morphological asymmetry in female (but not male) fish, and continuing exposure to compromised water quality throughout life impacts both general condition and reproductive fitness of stickleback, especially older female fish, in SFWR.

Effects of neuropeptide F2 on female reproduction in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

AbstractRecently, neuropeptide F2 (NPF2) has been demonstrated to increase food consumption and body weight in the cotton bollworm, Helicoverpa armigera. This study evaluated the effect of NPF2 on the adult female reproductive system of H. armigera. Daily NPF2 injections increased oocyte size, ecdysteroid titre in ovaries and haemolymph and the expression level of ecdysone receptor (EcR), ultraspiracle (USP) and vitellogenin (Vg) genes. However, NPF2 injection had no effect on the expression level of hormone receptor 3 (HR3). Fecundity and fertility were increased after the injection of NPF2. The knockdown of the NPF2 gene using RNA interference (RNAi) had opposite effects compared to NPF2 injection. Overall, these results revealed that NPF2 has a regulatory role in the female reproduction of the cotton bollworm.