Low Hatchability Research Articles

Climate and geographic trends in hatch delay of the treehole mosquito, Aedes triseriatus Say (Diptera: Culicidae)

Eggs of Aedes triseriatus mosquitoes are stimulated to hatch when inundated with water, but only a small fraction of eggs from the same batch will hatch for any given stimulus. Similar hatching or germination patterns are observed in desert plants, copepods, rotifers, insects, and many other species. Bet hedging theory suggests that parents stagger offspring emergence into vulnerable life history stages in order to avoid catastrophic reproductive failures. For Ae. triseriatus, a treehole breeding mosquito, immediate hatching of an entire clutch leaves all of the parent's progeny vulnerable to extinction in the event of a severe drought. Natural selection has likely favored parents that pursued a bet hedging strategy where the risk of reproductive failure is distributed over time. Considering treehole mosquitoes, bet hedging theory could be used to predict that hatch delay would be positively correlated with the likelihood of drought. To test this prediction, we collected Ae. triseriatus from habitats that varied widely in mean annual precipitation and exposed them to several hatch stimuli in the laboratory. Here we report that, as predicted, Ae. triseriatus eggs from high precipitation regions showed less hatch delay than areas of low precipitation. This strategy probably allows Ae. triseriatus to cope with the wide variety of climatic conditions that it faces in its extensive geographical range.

Cadmium toxicity to embryonic–larval development and survival in red sea bream Pagrus major

At 18 °C and 33 psu, 24 and 48 h LC 50 values of cadmium (Cd) for red sea bream Pagrus major embryos were 9.8 and 6.6 mg l −1, respectively, while 24, 48, 72, and 96 h LC 50 values for larvae were 18.9, 16.2, 8.0, and 5.6 mg l −1, respectively, indicating that embryos were more sensitive to Cd toxicity than larvae. Cd concentrations at ≥0.8 mg l −1 led to low hatchability (0–90% in ≥0.8 mg l −1 solutions vs. 97–100% in lower ones), delay in time to hatch, high mortality (38–100% vs. 1–10%), morphological abnormality (42–100% vs. 1–10%), reduced length (3.55–3.60 vs. 3.71–3.72 mm) in the embryos and larvae. They were Cd concentration dependent and potential biological significant endpoints for assessing the risk of Cd to aquatic organisms. Heart beat and yolk absorption of the larvae were significantly inhibited at some high concentrations but they were not as sensitive as other endpoints to Cd exposure.

Hatching behaviour of Nematodirus filicollis in a flock co-infected with Nematodirus battus

The development and survival of larvae of Nematodirus filicollis, an important nematode parasite of ruminants, were extensively investigated in the laboratory for the first time, using eggs harvested from sheep grazing in the UK in winter. Third-stage larvae (L3s) developed within the eggs between 12 and 25 degrees C, with the proportion of eggs developing successfully being highest at the upper end of this range. Eggs required chilling below 10 degrees C before being able to hatch at all, and maximum hatch was observed only following chilling to 4 degrees C. Hatching occurred above 6 degrees C, and peaked at 13 degrees C, with the proportion of eggs hatching decreasing to 17-20 degrees C, which appears to form an upper threshold temperature for hatching. When fully developed eggs were placed at 11-13 degrees C, L3 emerged very rapidly with hatching being completed within 6 days. Mortality of emerged L3s increased with temperature, particularly above 20 degrees C. For this parasite, given the low minimum hatching thresholds and the rapid emergence of L3, the existence of an upper hatching threshold is likely to have limited impact on patterns of larval availability on pasture. The strict requirement for chilling is surprising, being at odds with both previous observations and the wide geographical distribution of this species. It is possible that the proportion of eggs requiring chilling is an adaptable trait, enabling early infection of naïve hosts in the face of competition from N. battus, yet also persistence in regions that do not provide good conditions for the chilling of eggs. Further study of selectable variation in this trait could help us to understand the contrasting geographical ranges and disease patterns within the genus, and how different species might respond to climate change.

Effects of Housing Systems on Growth Performance, Blood Plasma Constituents and Meat Fatty Acids in Broiler Chickens

A research was conducted to determine the influence of the conventional and the free-range broiler housing systems using female broiler chicks had low hatching weight on growth performance, breast meat characteristics and some blood plasma parameters. In the conventional (totally confined) housing system sixty one-day-old female Ross broiler chicks were placed in indoor floor pens with three replicates of 20 chicks. In the free-range (partly-confined) housing system, sixty one-day-old Ross broiler chicks were placed in indoor floor pens and also accessed to a grass paddock during 44 day experimental period after 7 days old. Birds of both systems were fed the same commercial broiler diet. The free-range housing system significantly decreased the total feed intake and body weight of broilers (p<0.05). The redness (a* color) and yellowness (b* color) in breast meat were affected by the housing systems (p<0.05). The housing systems had no affect on fatty acids composition of breast meat (p>0.05). The plasma triglyceride and VLDL levels of the conventional reared birds were significantly higher than those reared the free-range (p<0.05). In conclusion, longer growth period was necessary to the free-range reared broilers.

Maternal low-protein diet programmes offspring growth in association with alterations in yolk leptin deposition and gene expression in yolk-sac membrane, hypothalamus and muscle of developing Langshan chicken embryos

The present study was aimed to investigate the mechanism underlying the influence of maternal low-protein (LP) diet on offspring growth in the chicken. One hundred and twenty Chinese inbred Langshan breeder hens were allocated randomly into two groups fed diets containing low (10%, LP) or normal (15%) crude protein levels. Low dietary protein did not affect the body weight of hens, but significantly decreased the laying rate and egg weight. The yolk leptin content was significantly lower in eggs laid by LP hens, while no differences were detected for yolk contents of corticosterone, tri-iodothyronine (T3) or thyroxine. Despite significantly lower hatch weight, the LP offspring demonstrated obviously higher serum T3 concentration, which is in accordance with the faster post-hatch growth rate achieving significantly heavier body weight and pectoralis major muscle weight 4 weeks post-hatching. Expression of 20-hydroxysteroid dehydrogenase (20-HSD) mRNA in the yolk-sac membrane was significantly down-regulated at embryonic day 14, whereas that of transthyretin and leptin receptor (LepR) was not altered. Moreover, hypothalamic expression of 20-HSD, glucocorticoid receptors, thyrotropin-releasing hormone and LepR mRNA was significantly up-regulated in the LP group compared with their control counterparts. In the pectoralis major muscle, significantly higher expression of insulin-like growth factor (IGF)-I and IGF-I receptor mRNA was observed in LP embryos. The present study provides evidence that maternal LP diet programmes post-hatch growth of the offspring. The associated alterations in yolk leptin deposition as well as in yolk-sac membrane, fetal hypothalamus and muscle gene expression may be involved in mediating such programming effect in the chicken.

Influence of forage fish and dietary lipid supplements on egg quality and fry production in channel catfish (Ictalurus punctatus) × blue catfish (Ictalurus furcatus) hybridization

Hybrid catfish (channel catfish Ictalurus punctatus × blue catfish Ictalurus furcatus) display characteristics that are favourable to aquaculture production. Low hatch percentages are a principal reason this hybrid is not used widely in the catfish industry. This study was conducted to determine whether additional food source rich in lipids may lead to a higher quality egg production. A 10-week feed trial was conducted in ponds in Auburn, AL. A total of 219 female Kansas Select channel catfish were stocked into nine ponds, 0.04 ha in size. Three dietary treatments were randomly allocated to the ponds. Diet-1 was a standard 60 g kg−1 lipid floating catfish feed. Diet-2 was the same feed supplemented with forage fish at ∼28 kg ha−1. The third diet was the aforementioned catfish feed topcoated with 20 g kg−1 lipid [10 g kg−1 menhaden fish oil, 5 g kg−1 high docosahexaenoic acid (DHA) oil and 5 g kg−1 high arachidonic acid oil]. Results indicate that brood fish fed the high lipid diet spawned larger egg masses and had larger eggs both in weight and in diameter, with increased complements of fatty acids such as DHA, eicosapentaenoic acid and total n-3 fatty acids. The neutral and polar lipid fractions are also presented.

CHICKEN PERFORMANCE, FEEDING, MAJOR DISEASE INCIDENCE, AND HYGIENE IN TWO LOW-INPUT POULTRY PRODUCTION SYSTEMS IN THE RURAL SECTOR OF FAYOUM GOVERNORATE.

The current study covered a total of 121 households located in 12 villages within 6 districts in Fayoum governorate. The data was collected during the period from March to August, 2007 through semi-structured interviews with questionnaires. Tow systems were identified: 1) the traditional backyard (38% of the sample), and 2) the landless household (34% of the sample). In addition 28% of the sample was classified as small commercial farms. The recent paper discusses only the first two systems since the third system was found to be different in nature, objectives and management level. Most of the chickens (59 %) are dual-purpose, and were less than 6 months and aimed in general at meat production. Low performance is the major phenomenon in the rural poultry production systems where the local chickens attain maturity slowly and laying age is delayed in addition to low hatchability rate and high mortality rate of about 20 %. There was a significant difference (P< 0.01) infemale age at onset, male weight at sexual maturity, and the Length of production period between traditional and landless poultry production systems in advantage to the first. Household kitchen waste is the main type of feed given to chickens. Equal incidences of disease were observed between the two studied systems. Diarrhea was the major disease. The X2 test was significant (P< 0.05) only with regard to ways of chicken disposal, and incidence of respiratory diseases.

Comparative studies on some physiological and biochemical characters in white and brown cysts of Heterodera glycines race 4

AbstractPrevious research showed that the hatch of second-stage juveniles (J2) from white females (cysts) was significantly different from that of J2 from brown cysts, which indicated that there were differences in diapause between J2 in white and brown cysts. In order to find out the relationships between some biochemical characters and diapause of Heterodera glycines, hatch rate and biochemical indices (total carbohydrate, glycogen, trehalose, glycerol and protein, and activity of esterase and trehalase) in white and brown cysts of H. glycines race 4 were studied. The results suggested that hatch rate of J2 from brown cysts was significantly lower than that of J2 from white cysts. The glycogen and protein content and the activity of esterase in brown cysts were lower than in white cysts, whereas the total carbohydrate and trehalose content and the activity of trehalase in brown cysts were higher than in white cysts. Therefore, diapause in unhatched J2 in brown cysts was more extensive than that in J2 in white cysts, and active mutual transformation between trehalose and glycogen existed in brown cysts. SDS-PAGE patterns showed that there are 15 and 10 protein bands in white and brown cysts, respectively, and proteins of molecular masses 116.6, 79.1, 68.2, 64.3 and 60.5 kDa existed in white cysts, but were not present in brown cysts. There were three and six bands in patterns of esterase isoenzymes in white and brown cysts, respectively; EST0.63, EST0.75, EST0.81 of esterase isoenzymes occurred in brown cysts but not in white cysts. The result suggested that protein content declined and activity of esterase isoenzyme was enhanced during the transition from white to brown cyst. The low hatch rate of J2 from eggs in brown cysts might be related to these indices.

The relationship of embryonic development, mortality, hatching success, and larval quality to normal or abnormal early embryonic cleavage in Atlantic cod, Gadus morhua

A reliable method for assessing the viability of fertilized eggs early in development would be beneficial for the aquaculture industry, allowing egg batches with a high probability of low hatching success to be discarded before costly resources are devoted to their culture, and for recruitment models where egg viability is used predictively. During the last decade, the observation of cellular morphology during embryogenesis has received increased attention as a potential early indicator of embryo quality. However, most often, abnormally cleaving eggs are assessed en masse even though noticeable differences in cleavage patterns are generally present between individual eggs. We separated six egg batches of Atlantic cod, Gadus morhua Linnaeus, 1758, into normal and abnormal cleavage patterns, reared eggs individually in a temperature-controlled room, and recorded daily egg mortality until hatch, hatching success, larval deformation, and larval mortality. Seven abnormal cleavage patterns were readily distinguishable and all showed moderate variability in egg mortality. Both normal and abnormal eggs had similar mortality-rate trends, consisting of an initial high mortality that became asymptotic at about day 8 of development at 6.5 °C. Specific cleavage patterns showed variable mortality-rate trends. No significant differences in cumulative egg mortality were found between any abnormal cleavage patterns, but overall, abnormal eggs had significantly greater egg mortality than normal eggs. Hatching success was high in all groups and not significantly different between normal and abnormal eggs. Few larvae were deformed within any egg batch or pattern and no consistent trends were noted. A severity index was calculated and a suggested severity order determined as asymmetry < adhesions < margins ≤ inclusions < blastomere size.

Influences of Hypoxia on Hatching Performance in Chickens with Different Genetic Adaptation to High Altitude

The experiments were conducted to assess how hatching performance is affected by chicken breeds and environment of high altitude and to analyze the vital factor of the low hatchability at a 2,900-m altitude. Eggs of Tibetan and Dwarf chickens were incubated at conditions of normobaric normoxia, normobaric hypoxia, hypobaric hypoxia, and supplemental O2 at high altitude (hypobaric normoxia) during the whole incubation or at 0 to 7, 8 to 14, and 15 to 22 d of incubation, respectively. The results showed that the Tibetan chickens had greater hatchability (79.72%), lower water loss (12.90%), greater relative embryo weight (38.08%), and relative chick weight (68.41%) compared with the Dwarf chickens (31.69, 15.79, 30.71, and 65.21%, respectively) when both of them were incubated at a 2,900-m altitude. The hatchability was 71.60% in Tibetan chicken and 36.23% in Dwarf chicken under the normobaric hypoxia condition. The hatchability of chicken was efficiently increased with supplemental O2. The previous results indicated that the O2 deficit is the main factor resulting in the low hatchability and the poor chick quality of the lowland chicken breed when incubated at a 2,900-m altitude. Breeding chickens for adaptability to hypoxia and supplemental O2 is a good way to improve the hatchability and chick quality at that altitude.

Gene Segregation Effects on Fertility and Hatchability of Pure and Crossbred Chicken Genotypes in the Humid Tropics

This study was conducted to compare fertility and hatchability among pure and crossbred chicken genotypes. A total of three sires and thirty dams per genetic group were used in a study which was conducted over three months involving both direct and reciprocal crosses. A total number of 5804 eggs were set out of the total laid. Number of eggs fertile at first and second candling were significantly (P < 0.01) affected by both sire and dam strains. Similarly, number of eggs hatched, percentage fertility and hatchability were significantly (P < 0.01) affected by both sire and dam strains. There was also significant (P < 0.05) interaction effects between dam and sire strains on fertility and hatchability percentages. Matings involving pure strains of Naked Neck indigenous chicken resulted in lowest hatchability when compared to matings involving other pure and crossbred genotypes. Variations observed in percentage fertility and hatchability of eggs were attributed to segregation effects of genes in both pure and crossbred chicken genotypes used for the study.

Desiccation tolerance in embryonic stages of the tardigrade

AbstractDesiccation tolerance commonly found among tardigrades allows them to cope with temporal variation of available water. Although the long‐term survival of adults has been demonstrated in several species, desiccation tolerance of eggs and embryos is less well studied, however it is an important aspect from an ecological and evolutionary point of view. For the first time we evaluated the desiccation tolerance and subsequent hatching success of five different developmental stages of the tardigrade species Milnesium tardigradum, when rehydrated following drying at eight different humidity levels (10, 20, 31, 40, 54, 59, 72, 81%). Humidity level and developmental stage are significant factors in determining successful hatch rates. The results showed that the less developed stages were quite sensitive to desiccation. Low humidity levels during the first 3 days of development lead to a decrease in hatch rates following rehydration. Later developmental stages showed higher hatch rates than embryos dried at earlier stages. However, fast drying at low humidity levels resulted in delayed development and lower hatch rates following rehydration. In general, further developed embryos exhibit a better survival capacity compared with younger stages.

Inbreeding depression for various traits in two cultured populations of the American bay scallop, Argopecten irradians irradians Lamarck (1819) introduced into China

This paper examines the effect of inbreeding level of population on the magnitude of inbreeding depression expressed by comparing them between two cultured populations (A and B) in the hermaphroditic animal of the bay scallop Argopecten irradians irradians. Population A is expected to have less genetic variations and higher inbreeding level due to longer cultured history (20 generations) and less “ancestral” individuals (26 individuals) than population B due to shorter cultured history (4 generations) and more “ancestral” individuals (406 individuals). Two groups within each population were produced, one using self-fertilization and one using mass-mating within the same population. Selfed offspring (AS and BS) from two populations both had lower fitness components than their mass-mated counterparts (AM and BM) and exhibited inbreeding depression for all examined traits, e.g. lower hatching, less viability and slower growth, indicating that inbreeding depression is a common feature in this animal. Fitness components in all traits of offspring from population A significantly differed those from population B and the magnitude of inbreeding depression for all traits in population A with higher inbreeding level was significantly smaller than that in population B with lower inbreeding level, indicating that both fitness components and magnitude of inbreeding depression were significantly affected by inbreeding level of populations and genetic load harbored in population A may be partially purged through inbreeding. Moreover, the magnitude of inbreeding depression in the two populations both varied among traits and life history stages. The present results support the partial-dominance hypothesis of inbreeding depression.

The Torsin-family AAA+ Protein OOC-5 Contains a Critical Disulfide Adjacent to Sensor-II That Couples Redox State to Nucleotide Binding

A subgroup of the AAA+ proteins that reside in the endoplasmic reticulum and the nuclear envelope including human torsinA, a protein mutated in hereditary dystonia, is called the torsin family of AAA+ proteins. A multiple-sequence alignment of this family with Hsp100 proteins of known structure reveals a conserved cysteine in the C-terminus of torsin proteins within the Sensor-II motif. A structural model predicts this cysteine to be a part of an intramolecular disulfide bond, suggesting that it may function as a redox sensor to regulate ATPase activity. In vitro experiments with OOC-5, a torsinA homolog from Caenorhabditis elegans, demonstrate that redox changes that reduce this disulfide bond affect the binding of ATP and ADP and cause an attendant local conformational change detected by limited proteolysis. Transgenic worms expressing an ooc-5 gene with cysteine-to-serine mutations that disrupt the disulfide bond have a very low embryo hatch rate compared with wild-type controls, indicating these two cysteines are essential for OOC-5 function. We propose that the Sensor-II in torsin family proteins is a redox-regulated sensor. This regulatory mechanism may be central to the function of OOC-5 and human torsinA.

Density-dependent effects on hatching success of the olive ridley turtle, Lepidochelys olivacea

Historically, the olive ridley arribada at Playa Nancite, Costa Rica, was one of the largest olive ridley arribadas in the eastern Pacific with 70,000 nesting females in a year. Recently the Nancite arribada drastically declined. We hypothesized that the population decline at Playa Nancite could have been due to low hatching success as a result of the high density of nests on the beach, such that recruitment to the population was insufficient to balance losses. To test this hypothesis, we examined density-dependent effects on hatching success and their underlying mechanisms by experimentally manipulating nest densities in experimental plots on the nesting beach. We set up four nest-density treatments in five experimental blocks. We measured effects of density on hatching success, CO(2) and O(2) concentrations and temperature both within nests and in sand adjacent to nests frequently during incubation. Experimental nest densities affected hatching success with the highest density having the lowest hatching success. Higher nest density led to lower O(2) levels and higher CO(2) levels in the nest with greater changes in the latter part of the incubation. Highest temperatures occurred in high-density areas. Temperatures were lower in sand surrounding the nest than in the nest. Effects of density on temperature, CO(2) and O(2) were confirmed at a naturally high-density nesting beach, Playa La Flor, Nicaragua. Long-term failure in production of hatchlings due to historic high densities may have contributed to the decline of arribadas on Playa Nancite. Thus, density-dependent population control would have operated at the embryonic life stage in this population of olive ridley turtles.

Effects of dietary protein and energy levels on spawning performance of Nile tilapia (Oreochromis niloticus) broodstock in a recycling system

The effects of dietary protein and energy level on spawning performance of Nile tilapia broodstock and hatchability of their eggs were studied. Nine diets containing three protein (30, 35 and 40%) and three energy (14.6, 16.7 and 18.8 MJ GE/kg) levels were prepared. The diets were fed to duplicate groups of broodfish (average weight of 60.5±4.6 g for males and 39.4±3.1 g for females) at 2–3% of their body weight, twice a day, for 150 days. At low protein level (30%), time to first spawning was significantly longer than at 35 and 40% protein levels, and increased with increasing dietary energy (decreasing protein-to-energy (P/E) ratio). At 35 and 40% protein levels, time to first spawning was not affected by dietary energy. Inter-spawning intervals (ISI) showed irregular patterns in relation to dietary protein and energy, however, at 40% protein the females tended to spawn at shorter intervals, regardless of dietary energy. Spawning performances, including total number of spawnings per tank, number of spawnings per female, absolute fecundity and average number of eggs per spawn, were all significantly lower (P<0.05) at 30% CP than at higher protein levels. At all protein levels, increasing dietary energy from 14.6 to 18.8 MJ GE/kg (and decreasing P:E ratio) resulted in a significant decrease in fish fecundity. Egg size was not significantly affected by dietary protein and energy. At all energy levels, egg hatchability increased with increasing dietary protein levels (P<0.05). Eggs produced from broodstock fed 30 and 35% CP, exhibited significantly lower hatchability (P<0.05) and needed less time for hatching and yolk-sac absorption, and resulted in lower larval length than those fed a 40% protein diet. However, increasing energy level at each dietary protein level did not significantly affect these parameters. These results revealed that the best spawning performance of Nile tilapia broodstock reared in a recycling system was achieved at 40% dietary protein and 16.7 MJ GE/kg, with a P/E ratio of 23.6 g/MJ.

The effects of exposure and microbes on hatchability of eggs in open‐cup and cavity nests

Many avian species initiate incubation before clutch completion, resulting in an asynchronous hatch of their eggs. Several studies suggest that early laid eggs in birds that exhibit synchronous hatching may be more vulnerable to the negative impacts of ambient temperatures and/or trans‐shell infection by microbes. However, nearly all of these studies have exposed fertile eggs to environmental conditions in artificial cavity nests, and thus, the effects of exposure of eggs to environmental conditions in open‐cup nests remains largely unknown. Therefore, we directly compared hatchability and rates of trans‐shell infection in fertile domestic chicken eggs that were exposed for 1–5 days in either open‐cup or cavity nests. Eggs in open‐cup nests had significantly higher rates of trans‐shell infection and lower hatchability than those in cavity nests. These differences may result from different environmental conditions in open‐cup nests, as well as in rates of microbial colonization of eggs. Cavity nests maintained slightly higher temperatures than did open‐cup nests in the same location; thus, eggs in cavity nests were exposed for a longer period of time to temperatures ≥27°C, the temperature at which antibacterial enzymatic activity is initiated in the albumen. Moreover, microbial growth on eggs was much higher in open‐cup nests even when eggs in these nests were cleaned daily with alcohol. It may be that the increased exposure to rain events in open‐cup nests may facilitate microbial growth and egg infection. Thus, our data suggest that open‐cup nesters may face constraints on reproduction different from those that cavity nesters face, and therefore may make choices regarding incubation that reflect these challenges.

Factors affecting changes in grey partridge population dynamics in a French arable farmland over an eleven-year period

The grey partridge Perdix perdix is of conservation concern owing to habitat heterogeneity losses and the negative impact of other environmental factors, e.g., pesticide use, predators, weather or shooting pressure, which are known to be associated with population decline. By an 11-year-period study in an intensively cultivated farmland located in the Paris basin, we aimed to relate the changes in grey partridge population dynamics with the changes in agriculture, monthly rainfall and shooting pressure. Summer drought occurred at the middle time of the study period. At the start of our study, a new cultivation, winter-wheat broadcast in maize-stubble fields, was introduced that probably improved the habitat. But in the next years, there was a loss in habitat diversity due to the disappearance of pastures dedicated to sheep rearing, removal of non-cropped areas and field boundaries and increase in the mean field size. Shooting was annually adjusted to what the owner believed to be a wise harvest. In post-breeding coveys, both percentages of hens with young among total hens and young-to-successful hens ratios first increased and then decreased. The mean brood size was rather weak during the dryness incident. The number of pairs in a more heterogeneous sector was always greater than in a less one. In both sectors, spring abundance first increased and then decreased. In the second half of the study period, the shooting quotas were reduced, especially when the mean brood size fell down. Low hatching rates of clutches and low chick survival rates explain the population decline, as the results are convincing. To stop the population decline in intensive arable farmland, good breeding success is needed. This can be provided by favourable habitats for hens to nest and for chicks to feed.

IN VITRO CULTURE OF BOVINE EMBRYOS WITH A SERUM REPLACER IMPROVES SURVIVAL FOLLOWING VITRIFICATION AND WARMING

Use of fetal bovine serum during in vitro embryo culture is known to be detrimental to bovine embryo cryosurvival. Previously, a serum replacer (KNOCKOUT SR, Gibco) was shown to be beneficial for the in vitro culture of bovine embryos, so we tested whether this culture supplement could also improve survival of embryos following vitrification and warming. Cumulus oocyte complexes were retrieved by slashing 2–8 mm follicles on ovaries obtained from the abattoir. They were matured, fertilized (day 0), and then cultured for 3 days in KSOM. On day 3 postfertilization, embryos were divided into four treatments: 1) KSOM static culture (KNM; n = 533); 2) embryos moved to fresh KSOM (KD3; n = 537); 3) embryos moved to KSOM+SR (10%; n = 534); or 4) embryos moved to KSOM+FBS (10%; n = 534), and were cultured for the remainder of the 7 day culture period, in a humidified low oxygen environment (5/5/90). Embryos were then graded for stage and quality. Grade 1 and 2 blastocysts were vitrified in groups of 3–5 within treatments in a two step process, loaded into gel loading tips in 16.5% EG/16.5%DMSO/0.5M sucrose and quickly plunged into liquid nitrogen for storage. Upon warming and rehydration, embryos were cultured for an additional 48h under the same culture conditions by treatment listed above. Data were analyzed by ANOVA using SAS, and differences were determined using LSMeans, with significance deemed P < 0.05. Development to blastocyst on day 7 was highest for KSOM+SR (37%), but was not different from other treatments. The percentage of freezable quality blastocysts (grades 1 and 2) by treatment were 70, 60, 58 and 50% for KNM, KD3, KSOM+SR and KSOM+FBS, and differed between KNM and KSOM+FBS, and KNM and KSOM+SR (P < 0.05). Survival was defined as re-expansion and continued development with normal morphology in culture following vitrification and warming, and was significantly greater for KSOM+SR than all other treatments at 24h (64.7%, P < 0.05). At 48h post warming, KSOM+SR still had the highest survival, and was significantly greater than KSOM+FBS (46% vs. 19%, P < 0.05). KSOM+SR gave the highest percentage hatching/hatched blastocysts in culture post-warming, but was not different from the other treatments (P > 0.10). All treatments had significantly lower hatching in culture than non-vitrified controls cultured in fresh drops of KSOM+SR from day 7 to day 9 post-fertilization (90%, P < 0.05). These data suggest that culture with SR can improve the cryosurvival of in vitro produced and vitrified bovine embryos, but is still not comparable to non-vitrified controls. Future work will determine if SR can also replace FBS in vitrification solutions to get further improvements in bovine embryo cryosurvival. This project was supported by the Florida Agricultural Experiment Station. (poster)

Obligate symbiont involved in pest status of host insect.

The origin of specific insect genotypes that enable efficient use of agricultural plants is an important subject not only in applied fields like pest control and management but also in basic disciplines like evolutionary biology. Conventionally, it has been presupposed that such pest-related ecological traits are attributed to genes encoded in the insect genomes. Here, however, we report that pest status of an insect is principally determined by symbiont genotype rather than by insect genotype. A pest stinkbug species, Megacopta punctatissima, performed well on crop legumes, while a closely related non-pest species, Megacopta cribraria, suffered low egg hatch rate on the plants. When their obligate gut symbiotic bacteria were experimentally exchanged between the species, their performance on the crop legumes was, strikingly, completely reversed: the pest species suffered low egg hatch rate, whereas the non-pest species restored normal egg hatch rate and showed good performance. The low egg hatch rates were attributed to nymphal mortality before or upon hatching, which were associated with the symbiont from the non-pest stinkbug irrespective of the host insect species. Our finding sheds new light on the evolutionary origin of insect pests, potentially leading to novel approaches to pest control and management.