Production Of Viable Eggs Research Articles

A New Method for Feeding Laboratory-Reared Aedes aegypti (Diptera: Culicidae) Adult Females1

Abstract The mosquito Aedes aegypti (L.) (Diptera: Culicidae) transmits arboviruses including the causative agent for yellow fever and threatens human health in tropical and subtropical areas. To reduce the incidence of infection, a variety of tactics is being developed to keep the population density of this vector mosquito as low as possible. Laboratory research directed to this end requires maintaining laboratory colonies of the insect, which, in this case, requires providing immobilized live animals to A. aegypti adult females for a source of blood for production of viable eggs. Using live animals for this procedure is costly, time consuming, and requires rearing mammalian species in the laboratoy. This study evaluated the impact of supplying the adult females with blood from a domestic pig (Sus scrofa domestica L.) mixed with an anticoagulant (7 ml of heparin per liter of blood) on the oviposition rate of A. aegypti. Feeding A. aegypti females with pig blood obtained from a slaughter facility and mixed with heparin produced more eggs (6,994 ± 168) than those allowed to feed on a living hamster as a source of blood (5,483 ± 171). Thus, this methodology is more efficient and economical than the current use of live animals to feed females of A. aegypti.

Asymmetrical reproductive interference between Aedes aegypti and Aedes albopictus: Implications for coexistence.

Aedes aegypti and Aedes albopictus are two sympatric mosquito species that compete with each other for resources when their breeding habitats overlap. This study examines what happens when sympatric Ae. aegypti and Ae. albopictus mosquitoes' mate with each other and other species by looking at insemination rates, fecundity, and hatchability rate. We performed controlled mating experiments in laboratory setting, assessing both conspecific and interspecific crosses. We measured insemination rates, egg numbers, and hatching success to examine the reproductive interference dynamics between these two distinct mosquito species. In the context of conspecific mating, it was observed that both female Ae. aegypti and Ae. albopictus exhibited high insemination rates, with percentages of 98% and 94% respectively. However, interspecific mating exhibited interesting asymmetries: Ae. albopictus males achieved a notable insemination success rate of 28% when mating with Ae. aegypti females, while Ae. aegypti males achieved only an 8% insemination success with Ae. albopictus females. Additionally, females that mated with interspecific males had reduced production of viable eggs compared to conspecific mating. Most notably, interspecific mating resulted in the production of infertile eggs, while conspecific mating led to successful hatching. The study reveals that Ae. aegypti and Ae. albopictus can asymmetrically interfere with each other's reproduction, causing a 'satyr' effect. This understanding of interspecific competition and reproductive interference in these mosquito species could impact their coexistence in shared breeding habitats.

Influence of climatic factors on the life stages of Aedes mosquitoes and vectorial transmission: A review.

Aedes aegypti and Aedes albopictus are two sympatric mosquito species that compete with each other for resources when their breeding habitats overlap. This study examines what happens when sympatric Aedes aegypti and Aedes albopictus mosquitoes' mate with each other and other species by looking at insemination rates, fecundity, and hatchability rate. We performed controlled mating experiments in laboratory setting, assessing both conspecific and interspecific crosses. We measured insemination rates, egg numbers, and hatching success to examine the reproductive interference dynamics between these two distinct mosquito species. In the context of conspecific mating, it was observed that both female Ae. aegypti and Ae. albopictus exhibited high insemination rates, with percentages of 98% and 94%, respectively. However, interspecific mating exhibited interesting asymmetries: Ae. albopictus males achieved a notable insemination success rate of 28% when mating with Ae. aegypti females, while Ae. aegypti males achieved only 8% insemination success with Ae. albopictus females. Additionally, females that mated with interspecific males had reduced production of viable eggs compared to conspecific mating. Most notably, interspecific mating resulted in the production of infertile eggs, while conspecific mating led to successful hatching. The study reveals that, Ae. aegypti and Ae. albopictus can asymmetrically interfere with each other's reproduction, causing a 'satyr' effect. This understanding of interspecific competition and reproductive interference in these mosquito species could impact their coexistence in shared breeding habitats.

Deficiency of Brummer lipase disturbs lipid mobilization and locomotion, and impairs reproduction due to defects in the eggshell ultrastructure in the insect vector Rhodnius prolixus

Rhodnius prolixus is a hematophagous insect, which feeds on large and infrequent blood meals, and is a vector of trypanosomatids that cause Chagas disease. After feeding, lipids derived from blood meal are stored in the fat body as triacylglycerol, which is recruited under conditions of energy demand by lipolysis, where the first step is catalyzed by the Brummer lipase (Bmm), whose orthologue in mammals is the adipose triglyceride lipase (ATGL). Here, we investigated the roles of Bmm in adult Rhodnius prolixus under starvation, and after feeding. Its gene (RhoprBmm) was expressed in all the analyzed insect organs, and its transcript levels in the fat body were not altered by nutritional status. RNAi-mediated knockdown of RhoprBmm caused triacylglycerol retention in the fat body during starvation, resulting in larger lipid droplets and lower ATP levels compared to control females. The silenced females showed decreased flight capacity and locomotor activity. When RhoprBmm knockdown occurred before the blood meal and the insects were fed, the females laid fewer eggs, which collapsed and showed low hatching rates. Their hemolymph had reduced diacylglycerol content and vitellogenin concentration. The chorion (eggshell) of their eggs had no difference in hydrocarbon amounts or in dityrosine crosslinking levels compared to control eggs. However, it showed ultrastructural defects. These results demonstrated that Bmm activity is important not only to guarantee lipid mobilization to maintain energy homeostasis during starvation, but also for the production of viable eggs after a blood meal, by somehow contributing to the right formation of the egg chorion.

Natural spawning of the leopard grouper (Mycteroperca rosacea) in captivity in La Paz, Mexico

Natural spawning of the leopard grouper (Mycteroperca rosacea) was studied in captivity from 2004 to 2008 under natural photoperiod conditions. Fish spawned naturally in 2006, but only 90,000 unfertilized eggs were collected. A total of 43 and 27 spawning days were observed in 2007 and 2008, respectively. Spawning season began in March and lasted until May–June and was related to an increase in water temperature from 21.1 to 23.8 °C. The mean (SE) number of eggs released each day was 101,705 (13,876) in 2007 and 40,510 (7,874) in 2008, and the total number of eggs collected in 2007 and 2008 was 4.37 × 106 and 1.07 × 106, respectively. The number of eggs collected per month was not significantly different within each year (P > 0.05), although a significant difference was observed between 2007 and 2008 (P < 0.05). The annual relative number of eggs released was 288,750 eggs·kg–1 in 2007 and 72,919 eggs·kg–1 in 2008, and viable egg production was 184,800 eggs kg–1 in 2007 and 25,375 eggs kg–1 in 2008. The fertilization rate (%) of the eggs collected daily differed significantly throughout the spawning season of 2007 (P < 0.05). The fertilization rate also differed (P < 0.05) between 2007 (61.10%) and 2008 (32.30%). Statistical analysis of the 2 consecutive spawning seasons indicated no correlation between the fertilization rate and fecundity. The effect of the moon phase on spawning was also considered. The fish spawned at dusk before total darkness. Mean (SD) egg diameter was 864.0 ± 22.0 μm.

Analysis of Trace Metal Bioaccumulation in Fish and Man; Health Risk Impact

Trace metals occur during natural processes and are also obtained during anthropogenic activities. Streams, lakes and rivers surrounded by farmlands engaged in the use of Trace metal-enriched fertilizers have shown a possible and positive correlation to the rise of Trace metals in the use of chemical, organic and water-soluble fertilizers for a long period. there is a tendency for high correlations of trace metals in source waters. Furthermore, the increasing level of trace metals in fish is alarming and has spurred scientists to make research on the dangers caused by the trace metals resulting in trace metal accumulation and bioaccumulation of life cells. This study aims at assessing the possible sources of trace metals in the aquatic environment, the impact of Trace metals in the aquatic environment, their bioaccumulation in fish and human health risk impact, negative effects in fish have been attributed to the accumulation of trace metals such as irritation of the gastrointestinal mucosa, nephritis, necrosis, neurological and behavioural disorders and death amongst others). The ingestion, absorption and uptake of trace metals in fish are usually toxic and result in harmful damage to the fish and fish life. Since most of the metals taken up are non-biodegradable, such metals can bioaccumulate and bio-magnify. Over time, the accumulated metals affect the growth and development stages of fish from the production of viable eggs, hatchability laval, fingerlings and juvenile life stages. This is so because the early life stages are more sensitive than during maturing and adulthood. In conclusion, negative results of the presence of trace metals and the effect of bioaccumulation and bio-magnification have been reviewed in this paper. This study recommends that the proper assessment and treatment of all forms of wastewater, agricultural waste, sewage, and industrial effluents be carried out before their discharge into the environment.

Drosophila melanogaster females prioritise dietary sterols for producing viable eggs

Limiting calories or specific nutrients without malnutrition, otherwise known as dietary restriction (DR), has been shown to extend lifespan and reduce reproduction across a broad range of taxa. Our recent findings in Drosophila melanogaster show that supplementing flies on macronutrient-rich diets with additional cholesterol can extend lifespan to the same extent as DR, while also sustaining high egg production. Thus, DR may be beneficial for lifespan because it reduces egg production which in turn reduces the mother’s demand for sterols, thus supporting longer lifespan. It is also possible that mothers live longer and lay more eggs on high sterol diets because the diet triggers enhanced somatic maintenance and promotes egg production, but at the cost of diminished egg quality. To test this, we measured the viability of eggs and development of offspring from mothers fed either cholesterol-sufficient or cholesterol-limiting diets. We found that even when the mother’s diet was completely devoid of cholesterol, viable egg production persisted for ∼10 days. Furthermore, we show that sterol-supplemented flies with long lives lay eggs that have high viability and the same developmental potential as those laid by shorter lived mothers on sterol limiting diets. These findings suggest that offspring viability is not a hidden cost of lifespan extension seen in response to dietary sterol supplementation.

In vitro production of viable eggs from isolated mouse primary follicles by successive culture.

To produce viable eggs from single primary follicles in vitro, primary follicles containing oocytes (average 39.0 ± 0.2 µm in diameter) were isolated from the ovaries of 1-week-old mice, and cultured in combination with culture membranes for the first 8 days up to the secondary follicle stage, followed by the next 12 days to the later stages. After culture with a combination of first and second culture membranes using high and low adhesion characteristics, the average oocyte diameters of the surviving follicles increased by almost two-fold in all four groups. Further, the oocyte maturation rate was the highest (74.1%) in the culture group with low adhesion with collagenase and high adhesion. In this culture group, when the O2 concentration was changed from 20% in the first culture to 5% in the second culture, the cleavage rate increased to 47.5%, which was comparable to the level of the in vivo control (34.6%). Finally, 39 embryos at the 2- to 8-cell stages were transferred into the oviducts of three pseudopregnant females, and eight live pups (20.5%) were obtained. Of the eight pups, six survived for at least six months and were fertile. The present study shows successive in vitro cultures of single isolated primary follicles for the production of viable eggs. We believe that this culture system, with a combination of culture membranes under controlled O2 conditions, is applicable to other mammalian species, including humans.

Spawning substrate preference and spawning behavior of chocolate mahseer, Neolissochilus hexagonolepis

Captive breeding programs for Neolissochilus hexagonolepis are essential for population restoration. To develop an efficacious method for enhancing N. hexagonolepis spawning in captivity, there was examination of: (1) different types of spawning substrate and (2) area of spawning in the substrate. The study was conducted to describe spawning behavior of males and females. There was a choice of three substrates in which to spawn: gravel, small cobble, and coarse sand. There was preferential choosing of gravel followed by cobble with there being no use of sand for spawning. Behavior of N. hexagonolepis included preparation of a spawning pit by females, a behavior that has not been previously ascertained for cyprinids. Males expressed courting behaviors, including chasing, nudging, and quivering. Courting males expressed aggressive behaviors towards other males. Results from the present study are the first on the volitional spawning of N. hexagonolepis in captivity using spawning substrate. It was further revealed that using a gravel substrate tray would also be a feasible approach for egg production. Mean total eggs per female and mean fertilized eggs collected were less when there was siphoning used for egg collections in the preference study. Hence, stripping was implemented to increase the egg collection when spawning behaviors were observed. Total eggs collected were 40,540 with 3685 eggs per female, 90.3% fertilization rate, 82.8% hatching rate, and 97.4% free-swimming larvae survival rate. The implications of this study could be beneficial for enhancing the natural population through environmental management and developing a viable egg production technique in captivity.

The effect of fs800 on female egg production in Schistosoma mansoni

During schistosomiasis, the paired Schistosoma mansoni female produces about 300 eggs each day. These eggs are responsible for the clinical picture and the transmission of the disease. During female development and egg production, fs800 is expressed only in female vitelline cells. Blast search of fs800 did not show similarities with any published sequences by NCBI. We hypothesize that the product of this gene plays a role in S. mansoni egg production. By using RNA interference to knockdown fs800 and quantitative PCR to measure the gene expression in the female schistosomes, we were able to demonstrate that fs800 product is crucial for viable egg production, it has no effect on worm health or male-female pairing. Our data suggest fs800 inhibition as a potential target to prevent transmission and pathology of schistosomiasis.

Influence of Genetic Selection for Growth and Broodstock Diet n-3 LC-PUFA Levels on Reproductive Performance of Gilthead Seabream, Sparus aurata.

Simple SummaryGilthead seabream (GSB) broodstock were genetically selected based on their growth trait either high growth (HG) or low growth (LG) to evaluate the reproductive performance of these both traits under either fish oil (FO) or vegetable oil (VO) based diets feeding regime. The egg and larval quality were significantly improved by the broodstock selected for HG trait fed under FO based diet. This indicates that broodstock selected with HG trait has positive influence on the improving sperm, egg and larval quality in gilthead seabream.Genetic selection in gilthead seabream (GSB), Sparus aurata, has been undertaken to improve the growth, feed efficiency, fillet quality, skeletal deformities and disease resistance, but no study is available to delineate the effect of genetic selection for growth trait on GSB reproductive performance under mass spawning condition. In this study, high growth (HG) or low growth (LG) GSB broodstock were selected to evaluate the sex steroid hormones, sperm, egg quality and reproductive performance under different feeding regime of commercial diet or experimental broodstock diet containing either fish oil (FO) or vegetable oil (VO) based diet. Under commercial diet feeding phase, broodstock selected for either high growth or low growth did not show any significant changes in the egg production per kg female whereas egg viability percentage was positively (p = 0.014) improved by the high growth trait broodstock group. The experimental diet feeding results revealed that both growth trait and dietary fatty acid composition influenced the reproductive performance of GSB broodstock. In the experimental diet feeding phase, we observed high growth trait GSB males produced a higher number of sperm cells (p < 0.001) and also showed a higher sperm motility (p = 0.048) percentage. The viable egg and larval production per spawn per kg female were significantly improved by the broodstock selected for high growth trait and fed with fish oil-based diet. This present study results signifies that gilthead seabream broodstock selected on growth trait could have positive role in improvement of sperm and egg quality to produce viable progeny.

Reproductive interference between Aedes albopictus and Aedes flavopictus at a place of their origin.

Aedes (Stegomyia) albopictus and Aedes (Stegomyia) flavopictus are related species that have overlapping distributions from southern to central Japan. To understand how they interact, we studied reproductive interference between them, particularly focusing on the body size difference between the mating pair. Here, we examined the effects of conspecific, heterospecific and double mating (i.e. heterospecific mating followed by conspecific mating) on copulation duration, egg production and hatchability of eggs using mosquitoes that varied in body size. Females mated only with heterospecific males produced few viable eggs, indicating that post-mating isolation is almost complete. When mated with heterospecific males before conspecific mating, the production of viable eggs was lower than when mated only with conspecific males, revealing the occurrence of reproductive interference. The degree of reproductive interference was larger in Ae. flavopictus than in Ae. albopictus when the female size was small but did not differ between them when the female size was large. Aedes albopictus females appear to be able to distinguish Ae. flavopictus males from conspecific males and larger females are more successful in the rejection of heterospecific males. On the other hand, Ae. flavopictus were not able to discriminate between conspecific and heterospecific males.

Design and Operation of Egg Collectors for Pelagic Spawning Marine Fishes

As aquaculture production techniques streamline, interest in captive breeding for marine fish species increases. The food, ornamental, and bait industries all benefit from expanding the development of aquaculture techniques for desirable marine fish species. A significant limitation in developing aquaculture protocols for marine fish species is an adequate understanding of viable egg production and larval development. The first step in that process is to efficiently collect fertilized embryos, usually referred to as eggs, for examination and further development. This 6-page fact sheet written by Cortney Ohs, John Marcellus, Eric Cassiano, and Jason Broach and published by the UF/IFAS Program in Fisheries and Aquatic Sciences of the School of Forest Resources and Conservation includes directions for construction and operation of two types of pelagic egg collectors: pre-filter and floating airlift. http://edis.ifas.ufl.edu/fa211

Identification and characterization of a mosquito-specific eggshell organizing factor in Aedes aegypti mosquitoes.

Mosquito-borne diseases are responsible for several million human deaths annually around the world. One approach to controlling mosquito populations is to disrupt molecular processes or antagonize novel metabolic targets required for the production of viable eggs. To this end, we focused our efforts on identifying proteins required for completion of embryonic development that are mosquito selective and represent potential targets for vector control. We performed bioinformatic analyses to identify putative protein-coding sequences that are specific to mosquito genomes. Systematic RNA interference (RNAi) screening of 40 mosquito-specific genes was performed by injecting double-stranded RNA (dsRNA) into female Aedes aegypti mosquitoes. This experimental approach led to the identification of eggshell organizing factor 1 (EOF1, AAEL012336), which plays an essential role in the formation and melanization of the eggshell. Eggs deposited by EOF1-deficient mosquitoes have nonmelanized fragile eggshells, and all embryos are nonviable. Scanning electron microscopy (SEM) analysis identified that exochorionic eggshell structures are strongly affected in EOF1-deficient mosquitoes. EOF1 is a potential novel target, to our knowledge, for exploring the identification and development of mosquito-selective and biosafe small-molecule inhibitors.

EMBRYO YIELD OF COWS-DONORS AND FUNCTIONAL ASYMETRY OF THE OVARIES

In recent years, experiments aimed at studying the structural asymmetry of paired organs have been conducted increasingly in veterinary medicine. The main factor, which prompted this interest, was extensive use of reproductive biotechnology methods to solve the problems of infertility. In experiments on laboratory animals and in clinical medicine, several authors have found that the nature of pathological processes in paired organs had some differences. Parameters of species functional asymmetry at the level of systems and organs are considered in terms of enantiomorphousness as a trait of adaptive evolution. The study of structural features of physiological and pathological processes in paired gonads of cows will increase the efficiency of biotechnological methods of folliculogenesis stimulation and production of more viable eggs. On the other side, it will reduce the cost of expensive drugs and working time due to more efficient pre-selection of animals for producing embryos.&#x0D; The aim of the research was to study structure and pattern of functional asymmetry of ovaries of high-producing cows and its influence on the level of quality embryos formation.&#x0D; Material and methods of research. The researches were carried out during 2011-2012 at two dairy breeding farms – "Agro-Soyuz" JSC (Dnipropetrovsk region) and "RVD-Agro" PE (Cherkasy region). Two groups of high-producing cows were formed of milking breeding stock, yields of which during the best lactation exceeded the average of the herd by 20-60%&#x0D; The animals were tested during the phased comprehensive research on suitability to removing embryos from them and use of the selected cows in the group of regular donors of embryos, in accordance with applicable requirements of embryo transplantation technology for cattle. During the selection and preparation of cows-donors, washing embryos and their morphological evaluation, we simultaneously performed collecting and analysing data on the activity of functional entities of the left and the right ovaries during luteal phase by palpation according to the advanced approaches. The comparison was performed during cows’ induced cycles using injections of synthetic analogues of F2α prostaglandin on standard procedures and after hormonally induced polyovulation in donors using follicle stimulating hormone drugs and on the standard and prolonged procedures.&#x0D; Results. Pattern of relationship between functional asymmetry of ovaries of high-producing cows-donors and their level of embryo yield was found. Palpation revealed that at cows with sufficient technology and high embryo yield after hormonally induced superovulation, ratio of the number of corpora luteal of the left ovary to the right had a tendency to approach the universal proportion of 38%:62% which is typical for luteogenes of cows in the induced and spontaneous cycles. In group of cows with low yields of high-quality embryos, the ratio of ovarian corpora luteal L: R was significantly different. The observed indicator of functional ovarian asymmetry needs to be researched more and it can be used as a criterion for resource-raising effect at selection of stable donors of embryos at high-yielding herds in the future. The significant change of functional asymmetry of donors-cows’ ovaries after hormone stimulation of polyovulation was shown, including the found phenomenon of inversion of dominant activity of gonads. It was experimentally stated that the high level of producing qualitative embryos for transplantation (9,50-9,86 per washing) was characterized for the cows with sufficient functional asymmetry of ovaries after polyovulation.&#x0D; Conclusions. Based on the fact that high-quality embryos from high-producing cows of different breeds will have breeding, biological and economic values in the world market of genetic resources in the next years, it is necessary to step up scientific research to study the patterns of functional asymmetry of the cows’ reproductive system as one of important biological factors influencing on effectiveness of embryo transplantation technology.

Development and physiological effects of an artificial diet for Wolbachia-infected Aedes aegypti

The endosymbiotic bacterium Wolbachia spreads rapidly through populations of Aedes aegypti mosquitoes, and strongly inhibits infection with key human pathogens including the dengue and Zika viruses. Mosquito control programs aimed at limiting transmission of these viruses are ongoing in multiple countries, yet there is a dearth of mass rearing infrastructure specific to Wolbachia-infected mosquitoes. One example is the lack of a blood meal substitute, which accounts for the Wolbachia-specific physiological changes in infected mosquitoes, that allows the bacterium to spread, and block viral infections. To that end, we have developed a blood meal substitute specifically for mosquitoes infected with the wMel Wolbachia strain. This diet, ADM, contains milk protein, and infant formula, dissolved in a mixture of bovine red blood cells and Aedes physiological saline, with ATP as a phagostimulant. Feeding with ADM leads to high levels of viable egg production, but also does not affect key Wolbachia parameters including, bacterial density, cytoplasmic incompatibility, or resistance to infection with Zika virus. ADM represents an effective substitute for human blood, which could potentially be used for the mass rearing of wMel-infected A. aegypti, and could easily be optimized in the future to improve performance.

Research Article: Effects of endocrine-disrupting chemical exposure on zebrafish ovarian follicles

The process of oocyte maturation involves both nuclear and cytoplasmic events that are essential for the production of viable eggs and subsequent fertilization in sexually reproducing animals. In zebrafish, oocyte nuclear maturation (meiotic resumption) is marked by a transition from opaque to translucent ovarian follicles. This transition is called clearing and results from germinal vesicle breakdown (GVBD) and the transformation of vitellogenin into yolk proteins. Oocyte maturation can be perturbed by endocrine-disrupting chemicals (EDCs). These EDCs have been broadly shown to interfere with reproductive development. Many herbicides and pesticides used agriculturally act as EDCs. These chemicals can enter aquatic ecosystems via runoff and erosion. To evaluate the effects of EDCs on zebrafish oocyte maturation, zebrafish ovarian follicles were cultured and exposed to various concentrations of either atrazine, 2,4-D, or diazinon. Follicles were evaluated at 2, 3, and 4 hours for size and viability, but clearing was assessed only at 4 hours post-exposure. Atrazine and diazinon significantly reduced follicle clearing at the tested concentrations. No effect was observed with 2,4-D exposure. At low enough concentrations, none of the chemicals produced endocrine-disrupting effects. The results suggest that at or above environmentally relevant concentrations, some EDCs impair oocyte maturation in exposed zebrafish follicles. The results support the need to monitor EDC exposure to prevent harmful effects not only on aquatic organisms, but also on humans and wildlife that are also exposed to these contaminants.

Physical characteristics and reproductive performance in Aedes (Diptera: Culicidae)

Body size is a physical factor of crucial importance underlying important traits of the reproductive dynamics of both sexes in mosquitoes. Most studies on the influence of body size in mating success of dengue vectors addressed sperm transfer to females and did not consider egg production, a prerequisite for population maintenance; male body size impact on reproduction has attracted little research interest with respect to sterile insect technique. In experiments involving differently sized adults, we examined whether the body size of the mates is a source of variation in reproductive outcome in &lt;em&gt;Aedes aegypti&lt;/em&gt;. In the absence of male partners, large females (LF) showed better fecundity than small females (SF). In intraclass mating trials, egg production was much greater in largesized than smallsized pairs. There were comparable fecundities in large females mated with small males and large pairs. [SF•SM] and [SF•LM] pairs showed equivalent fecundity. Nonmating did not result in the production of viable eggs by either small or large females. We also observed that eggs produced by largesized females mated with small males had better hatching success than those from either small or large pairs. Mating between small females and large males resulted in poor egg viability.

Effectiveness of African catfish pituitary extracts, dagin and water flow for optimising egg production, fertilisation and hatchability in artificial spawning of Barbus altianalis

Fish inducing hormones are widely used in commercial aquaculture to facilitate continuous supply of sufficient seed required on regular basis by the farmers. The objective of this study was to optimise production of viable eggs for improved hatchability during artificial spawning in Barbus altianalis. Two experiments were conducted, namely (i) experiment I evaluated the efficiency of using catfish pituitary extracts in spawning of second generation broodstocks compared to that of Dagin and water flow. (ii) experiment II examined ripe running females facilitated to spawn by running water only. Fish treated with pituitary extracts performed much better than those treated by Dagin with respect to fertilisation rates at 80.27 ± 39.57% (U = 66.5, p &lt; 0.001) and working fecundity at 2314.40 ± 882.04 (U = 59.5, p &lt; 0.05). However, the difference in hatchability was not significant (p &gt; 0.05). In experiment II, hatchability and working fecundity were significantly higher when fish were striped after 4 hours (100 degree hours at 25 oC) of running water than those striped after 10 hrs (250 degree hours) but fertilization rates were not different. The findings indicate that catfish pituitary extracts are more effective in inducing B. altianalis to spawn than those treated with Dagin. However, the observations made on ripe running females in both experiments suggest that they should not be induced with any hormone. Hence, the cost of spawning could further be reduced using running water, especially in wet seasons when the majority are ripe.Key words: Eggs, hatchability, hormone, spawning

Ontogeny and growth of early life stages of captive-bred European eel

Captive breeding of European eel, Anguilla anguilla is challenged by the complex hormonal control of Anguillid eel reproduction and the distinctive ontogeny of the leptocephalus larvae that are unique to the Elopomorph superorder. Recent experimental research has succeeded in the production of viable eggs and larvae of European eel, providing the basis for studies on early life stages of this species in captivity. In this study, we describe and illustrate morphological characteristics of eggs, embryos, and larvae from fertilization to termination of the yolk sac stage and provide a comparison with additional commercially important eel species. Furthermore, we model growth during the critical first phase in larval ontogeny, i.e. the yolk sac stage, and test for maternal effects. The eggs of A. anguilla typically have numerous oil droplets that coalesce into a single large oil droplet, while the zygote forms a large perivitelline space, reaching an egg diameter of 1.45±0.12mm at 3.0 to 3.5h post fertilization. Embryonic development from fertilization to larval hatch lasted ~46–48h at 20°C with the larvae emerging in a relatively undeveloped stage with a protuberant yolk sac. During the period of yolk and oil absorption, the larvae undertook significant changes in head and body morphology. At the completion of yolk sac absorption, the largely transparent larvae had a set of protruding teeth, pigmented eyes and tail, and a simple alimentary tract. Larvae appeared capable of feeding at ~12days post hatch at 20°C, and were able to survive another ~10days without feeding. Larval length approached an asymptotic maximum of 6.8mm around day 10 in non-fed larvae. Larval batches from different maternal origins varied in yolk sac size and the extent of yolk sac resources influenced larval size at the end of the yolk sac stage. The ontogenetic description presented here fills a gap in knowledge about the yet undiscovered early life stages of native European eel, which can provide a framework of reference for the development of hatchery technology. Such progress is urgently needed for a self-sustained aquaculture of this high-value and critically endangered species. Statement of relevanceEuropean eel is a high-value species in aquaculture, however, production is presently hampered by reliance on wild caught fry. Captive production of glass eels will reopen markets in Europe and Asia, benefiting European eel producers. The results presented here document recent progress within assisted reproduction and larval culture of this species in aquaculture and aid establishing hatchery technology of this species.