Insecticidal effect of high carbon dioxide atmospheres on thrips eggs oviposited in plant tissue

Thrips are damaging crop pests, but their eggs are difficult to detect for farmers and agricultural inspectors. We investigated the insecticidal effects of an elevated carbon dioxide atmosphere on thrips eggs oviposited within plant tissues. Percent mortality of Frankliniella occidentalis (Pergande), Frankliniella intonsa (Trybom), Thrips tabaci Lindeman, and Thrips palmi Karny exposed to 60?% CO₂ was evaluated at different temperatures (20, 25, 30, and 34?°C) and durations. Egg mortality of all four species increased with CO₂ exposure duration at each temperature, and the time required to achieve 100?% mortality decreased as the temperature increased between 20?C30?°C. Exposure to 60?% CO₂ at 30?°C for 12?h is considered to be 100?% lethal to most thrips pests of fresh agricultural produce. Our findings suggested that CO₂ treatment could be used to propagate thrips-free plants in horticultural nurseries.     

Mating behavior,egg laying,and embryonic development in the South American apple snail Asolene pulchella (Ampullariidae,Caenogastropoda)

Asolene pulchella is a dioecious freshwater snail from the La Plata basin, belonging to the Ampullariidae family. Our aim was to study the reproductive biology, including mating behavior, egg laying, and embryonic development under laboratory conditions. Copulations occurred underwater and lasted 2.66?h on average. The males produce fusiform paraspermatic cells (with seven to nine flagella) in addition to euspermatic cells with a corkscrew head, straight middle piece and long flagellum. Females stored sperm for up to 169?days. The egg masses (containing 98.1 eggs on average) are deposited underwater and are composed of many gelatinous packs of 1–4 eggs; the jelly matrix presented numerous calcite microcrystals. The spheroidal egg capsules measured 2.25?mm and contained a yellowish perivitellus of rubbery consistence. The embryonic development extends for 10.8?days on average. Hatchlings measured 1.4?mm and remained on the egg mass, feeding on the jelly. They resemble miniature adults but only began to feed on senescent plant material in their third week of age and begin aerial lung respiration after 8–10?weeks. The details of the structure of the egg masses and development constitute a rich source of traits for comparative and taxonomic studies in the Ampullariidae.     

Mating modifies female life history in a haplodiploid spider mite

Mating usually modifies females' resource allocation pattern, often as a result of conflicts between male and female partners. Can such a switch occur even in the absence of sexual conflicts? We addressed this issue in the haplodiploid spider mite Tetranychus urticae, whose biology and population structure considerably reduce conflicts between males and females over reproductive decisions. Comparing virgin and mated females, we tested the hypothesis that mated females modify their allocation pattern so as to maximize their probability of producing daughters. Mated females produced fewer but larger eggs, resulting in an overall similar reproductive effort but an increased probability of producing daughters, since in this species larger eggs are more likely to be fertilized and thus to become female. Moreover, mated females concentrated their reproduction early in life. Again, this might be a way to produce more daughters, since sperm is more abundant early in life. For virgins, spreading reproductive investment might be a way to save resources to extend life span, thus increasing their probability of encountering a sexual partner. Females with multiple opportunities for mating produced fewer eggs and a less female-biased sex ratio than once-mated females, raising the question of why multiple mating often occurs in this species.     

Maturation and hatching of eggs from silkworm ovaries preserved in liquid nitrogen

Ovarian imaginal discs prepared from fifth-instar larvae of the silkworm, Bombyx mori were treated with graded concentrations of glycerol, cooled at a rate of 1°C/min to ?35°C and preserved in liquid nitrogen for 2 days or more and then rapidly thawed (500°C/min). The frozen and thawed ovaries were transplanted into fifth-instar female larvae, in which more than 20% of the ovaries developed to produce mature eggs with a chorion according to the state of host development. By parthenogenetic activation, the mature eggs started embryogenesis and hatched to produce larvae. About 50% hatching occurred in the eggs developed in a C 108 × Cambodge host, and about 10% in a C 108 × Aojuku host. The hatched larvae completed post-embryonic development as did the normal larvae.     

Abundance and age of viable resting eggs of the calanoid copepod Boeckella poppei Mrázek in sediments: evidence of egg banks in two Antarctic maritime lakes

The existence of egg banks not only ensures the survival of zooplankton through harsh periods, but could also affect microevolutionary dynamics. Whether zooplankton at high latitudes can build up an egg bank in sediments, as occurs at lower latitudes, is still unknown. The distribution and age of viable resting eggs of the calanoid copepod Boeckella poppei Mrázek in sediments of two small freshwater lakes on King George Island were determined by slicing sediment cores at 1-cm intervals. Most viable resting eggs were found near the sediment surface, with abundance sharply declining to very low values at the depth of 5?cm, although eggs were present as deep as 9?cm in the sediments of Yanouhu Lake. The egg abundances in Xihu Lake and Yanouhu Lake were estimated to be 9.2?×?10⁴ and 7.2?×?10⁴?eggs?m^?2, respectively. ²¹⁰Pb dating indicated a relatively constant sedimentation rate (0.023?cm?year^?1) in Xihu Lake, which was used to estimate the mean age (46.8?year), the maximum age (195.7?year), and the mortality rate (1.64?% year^?1) of resting eggs of B. poppei in Xihu Lake. The accumulation of resting eggs with long-term viability in sediments provided the first evidence for the existence of egg banks in two Antarctic maritime lakes. An egg bank may serve as an overwintering strategy for B. poppei in Antarctica, enhance their ability to cope with random extreme changes, and contribute to their broad distribution.     

Mate provisioning, nutritional requirements for egg production, and primary reproductive effort of female Common Terns Sterna hirundo

We assessed the nutritional importance of mate provisioning to females during egg production and its effects on clutch parameters (egg size, length of the laying period) in Common Terns Sterna hirundo: (1) we estimated the costs of egg production by modeling the daily protein, lipid, and energy requirements of laying females, and (2) compared these costs to both the amount, and the timing, of the male's contribution via mate provisioning. Net lipid, net protein, and gross energy requirements for a three‐egg clutch were estimated to be 5.4 g, 8.6 g, and 569 kJ respectively. Peak protein and lipid requirements occurred one (day ?1) and two (day ?2) days before laying, respectively. Peak energy requirement occurred on day ?1; a cost of 127% to 157% above maintenance. Variation in male provisioning effort (in terms of energy and nutrients delivered) paralleled variation in predicted female requirements for egg production at the level of individual pairs. Males delivered protein in excess of the female's requirements on all days investigated. Male lipid delivery accounted for 45% of female net requirement on the day when demand was greatest (day ?2), but exceeded requirements on all other days. However, the proportion of the female's total energy budget (egg production, maintenance, and activity costs) that was supplied by her mate rose from an average of 29% on day ?2 to 76% during the interval between second and third eggs. Paradoxically, females that were fed at higher rates during the interval between first and second eggs produced clutches with lower total volumes, smaller last‐laid eggs, and clutches with a greater egg‐size hierarchy than conspecifics receiving less food from their mates. Also, females fed at higher rates during the interval between second and third eggs took longer to produce their clutch. These negative relationships between mate provisioning and clutch parameters contrast with previous studies in this and other species.     

The role of adult feeding in egg production and population dynamics of the checkerspot butterfly Euphydryas editha

Carbohydrate intake increases longevity, body weight maintenance and egg production in female Euphydryas editha. Amino acid intake leads to heavier eggs, larvae from which are more likely to survive. Females fed nectar produce more eggs in later masses than females which are not fed. During years of normal and below normal precipitation, larvae emerging from these later eggs are unlikely to reach obligatory size for diapause before their food dries up. On Jasper Ridge, where mortality is density-independent, nectar plays an important role increasing production of late egg masses during years of greater than normal rainfall when larvae from these masses are likely to reach diapause. The resulting large population increases, though infrequent, are probably important in maintaining population sizes large enough to reduce the chances of extinction during dry years.     

Egg size,postembryonic yolk,and survival ability

Summary Neonates of many species are dependent upon a post-embryonic yolk (PEY), a residual of the energy reserve of the developing embryo. Offspring hatching from large eggs have relatively more PEY than offspring from small eggs. Among daphniid Cladocera, large species produce larger eggs than smaller species. We have found that the proportional amount of energy reserve in eggs of five species of Cladocera is similar, but neonates of the larger Cladocera are born with a greater relative amount of postembryonic yolk, as triacylglycerol, than small species. Apparently, more of the reserve is metabolized by embryos of small species. This is correlated with the higher unitweight metabolic rates of smaller animals. It has been argued that animals should produce relatively larger eggs when exposed to low or unpredictable food conditions to increase the survivorship of their offspring. The physiological constraint of greater relative energy requirements of small embryos may limit PEY and explain why offspring of larger eggs survive better in low or unpredictable food resource environments.     

A simple rule reduces costs of extragroup parasitism in a communally breeding bird

How do cooperatively breeding groups resist invasion by parasitic "cheaters," which dump their eggs in the communal nest but provide no parental care [1,2]? Here I show that Greater Anis (Crotophaga major), Neotropical cuckoos that?nest in social groups containing several breeding females [3], use a simple rule based on the timing of laying to recognize and reject eggs laid by extragroup parasites. I experimentally confirmed that Greater Anis cannot recognize parasitic eggs based on the appearance of host egg phenotypes or on the number of eggs in the clutch. However, they can discriminate between freshly laid eggs and those that have already been incubated, and they accordingly eject asynchronous eggs. This mechanism is reliable in naturally parasitized nests, because group members typically lay their?eggs in tight synchrony, whereas the majority of parasitic eggs are laid several days later. Rejection of asynchronous eggs therefore provides a rare empirical example of a complex, group-level behavior that arises through relatively simple "rules of thumb" without requiring advanced cognitive mechanisms such as learning, counting, or individual recognition.     

Oviposition deterrents of Callosobruchus maculatus (Coleoptera: Bruchidae)

Abstract Many bruchids distribute their eggs uniformly among the host seeds available to them and tend to avoid adding eggs to seeds bearing any eggs if pristine seeds remain. Several authors have postulated that the adult cowpea seed beetles, Callosobruchus maculatus (F.) (Coleoptera: Bruchidae), produce pheromones inhibiting oviposition by females exposed to them. It is shown that both sexes produce compounds which can be washed from glass surfaces in a variety of organic solvents which do not deter oviposition as such, but seeds coated with such washings are avoided by ovipositing females when they are selecting seeds for egg-laying and uncoated seeds are available. Some components, at least, of the products persist for at least 30 days, longer than the normal development time of insects in the seeds. The compounds affect the distribution of eggs among the available seeds. At least three different biotypes of the species produce, recognize, and respond in the same way to each other's products. It is emphasized that the eggs themselves may not be the site of the product produced by females but that the physical presence of eggs cannot be overlooked in any discussion of the possible role of pheromones in oviposition and egg distribution by bruchids.     

Genetic caste determination in Pogonomyrmex harvester ants imposes costs during colony founding

Some populations of Pogonomyrmex harvester ants comprise genetically differentiated pairs of interbreeding lineages. Queens mate with males of their own and of the alternate lineage and produce pure-lineage offspring which develop into queens and inter-lineage offspring which develop into workers. Here we tested whether such genetic caste determination is associated with costs in terms of the ability to optimally allocate resources to the production of queens and workers. During the stage of colony founding, when only workers are produced, queens laid a high proportion of pure-lineage eggs but the large majority of these eggs failed to develop. As a consequence, the number of offspring produced by incipient colonies decreased linearly with the proportion of pure-lineage eggs laid by queens. Moreover, queens of the lineage most commonly represented in a given mating flight produced more pure-lineage eggs, in line with the view that they mate randomly with the two types of males and indiscriminately use their sperm. Altogether these results predict frequency-dependent selection on pairs of lineages because queens of the more common lineage will produce more pure-lineage eggs and their colonies be less successful during the stage of colony founding, which may be an important force maintaining the coexistence of pairs of lineages within populations.     

Do Acartia tonsa (Dana) eggs regulate their volume and osmolality as salinity changes?

Subitaneous eggs from an euryhaline calanoid copepod Acartia tonsa were challenged by changes in salinity within the range from full strength salinity, down to zero and up to >70?psu. Egg volume changed immediately, increasing from 2.8?×?10(5)?μm(3) at full strength salinity (35?psu) to 3.8?×?10(5)?μm(3) at 0?psu and back to its initial volume when gradually being returned to full strength salinity. Egg osmolality followed the molality of the surrounding water when challenged within a salinity range from 2 to 50?psu. Egg respiration was not affected when eggs kept at 35?psu was exposed to low salinity (2?psu). These results suggest that eggs are unable to regulate their volume or osmolality when challenged with changes in salinity. Gradual changes in salinity from 35 to 2?psu and back did not harm the eggs (embryos), since the hatching success remained unaffected by such changes in salinity. In contrast, extreme hyper-saline conditions (76?psu) made the eggs implode and killed the embryo. We propose that the embryo is protected from salinity stress by its plasma membrane and that water exchange driven by osmosis is restricted to the perivitelline space of the egg, which acts as a perfect osmometer in the salinity range of 5-35?psu. We hypothesize further that the embryo is able to keep its volume and osmolality constant due to the impermeability of the inner plasma membrane of the egg or by a combination of osmoregulation and reduced permeability of the inner plasma membrane.     

Delayed selfing in relation to the availability of a mating partner in the cestode Schistocephalus solidus

Abstract A hermaphroditic individual that prefers to outbreed but that has the potential of selfing faces a dilemma: in the absence of a partner, should it wait for one to arrive or should it produce offspring by selfing? Recent theory on this question suggests that the evolutionary solution is to find an optimal delay of reproduction that balances the potential benefit of outcrossing and the cost of delaying the onset of reproduction. Assuming that resources retained from breeding can be reallocated to future reproduction, isolated individuals, compared with individuals with available mates, are predicted to delay their age at first reproduction to wait for future outcrossing. Here, I present empirical support for this idea with experimental data from the hermaphroditic cestode Schistocephalus solidus. I show that individuals breeding alone delay their reproduction and initially produce their eggs at a slow rate relative to cestodes breeding in pairs. This delay is partly compensated for by a later higher egg production, although singly breeding cestodes still pay a cost of overall lower egg production.     

Impact of short‐term exposure to low subzero temperatures on egg hatch in the hemlock looper,Lambdina fiscellaria

The frequency of extreme events, such as cold spells, is expected to increase under global warming. Therefore, the ability of insects to survive rapid changes in temperature is an important aspect to investigate in current population ecology. The hemlock looper (HL), Lambdina fiscellaria (Guenée) (Lepidoptera: Geometridae), a defoliator of boreal balsam fir forests in eastern Canada, overwinters at the egg stage on tree trunks and branches where eggs can be exposed to very low subzero air temperatures. Using eggs from the island of Newfoundland (NL) and Quebec mainland (QC), we undertook field and laboratory experiments to determine: (1) their supercooling point (SCP) in mid‐January and mid‐February; (2) overwintering mortality; (3) cold tolerance to various combinations of subzero temperatures (?25, ?30, ?33, ?35, or ?37 °C) and exposure durations (2, 4, 8, 12, or 16 h); and (4) potential causes of death at subzero temperatures above the SCP. Regardless of population or sampling date, eggs supercooled on average at ?40.1 °C. In the field, 59% of eggs from either population that overwintered in Sainte‐Foy (QC) and Corner Brook (NL) hatched successfully, whereas none did in Armagh (QC) or Epaule (QC). In the laboratory, 50% of eggs survived after 4 h at ?34.4 °C or after 14 h at ?32.9 °C. In contrast, regardless of exposure duration, >50% of eggs hatched at temperatures ≥?33 °C, but <50% did so at ≤?35 °C, suggesting high pre‐freeze mortality. However, when eggs were attached to thermocouples and exposed to temperatures ranging from ?25 to ?37 °C for 16 h, 69% froze at temperatures of ?35 to ?37 °C, but only 2% did at ?25 or ?30 °C. Time to freeze decreased as subzero temperatures declined, and this was more evident in island eggs than in mainland eggs. Overall, eggs can freeze after a brief exposure to subzero temperatures higher than the standard SCP, and are thus highly vulnerable to cold spells.     

Patterns of parental investment,dispersal and size among coral-reef fishes

Synopsis Coral-reef fishes have been selected to produce propagules for dispersal because they live in a patchy environment, and the adults cannot migrate between patches. For large species (>100 mm SL) and widely separated patches, numerous propagules are needed, often with specialized pelagic intervals. Individuals of small species are confined to portions of the reef. They are unable to produce enough eggs for effective longrange dispersal, and so they keep their vulnerable eggs and young out of the plankton until they are well developed enough to seek out and settle onto the appropriate habitat before dispersing.Guarded demersal eggs, requiring a greater individual investment by the small short-lived species, further reduces their individual fecundity. These costs to fecundity, and the reduction in vagile young appear to account for the lack of postzygotic investment in larger longlived species.All coral-reef fishes are selected to disperse, usually with a young planktonic propagule interval. Both large and small species produce a mixed outcome, with some propagules returned to, or retained at the home reef, while others disperse more widely. The smaller the species the greater the proportion of propagules retained.     

Effects of maternal care on the lifetime reproductive success of females in a neotropical harvestman

1. Few studies have experimentally quantified the costs and benefits of female egg-guarding behaviour in arthropods under field conditions. Moreover, there is also a lack of studies assessing separately the survival and fecundity costs associated with this behavioural trait. 2. Here we employ field experimental manipulations and capture-mark-recapture methods to identify and quantify the costs and benefits of egg-guarding behaviour for females of the harvestman Acutisoma proximum Mello-Leit?o, a maternal species from south-eastern Brazil. 3. In a female removal experiment that lasted 14 days, eggs left unattended under natural conditions survived 75.6% less than guarded eggs, revealing the importance of female presence preventing egg predation. 4. By monitoring females' reproductive success for 2 years, we show that females experimentally prevented from guarding their eggs produced new clutches more frequently and had mean lifetime fecundity 18% higher than that of control guarding females. 5. Regarding survival, our capture-mark-recapture study does not show any difference between the survival rates of females prevented from caring and that of control guarding females. 6. We found that experimentally females prevented from guarding their eggs have a greater probability to produce another clutch (0.41) than females that cared for the offspring (0.34), regardless of their probability of surviving long enough to do that. 7. Our approach isolates the ecological costs of egg-guarding that would affect survival, such as increased risk of predation, and suggests that maternal egg-guarding also constrains fecundity through physiological costs of egg production. 8. Weighting costs and benefits of egg-guarding we demonstrate that the female's decision to desert would imply an average reduction of 73.3% in their lifetime fitness. Despite the verified fecundity costs of egg-guarding, this behaviour increases female fitness due to the crucial importance of female presence aimed to prevent egg predation.     

Associations between reproduction and work in workers of the Asian hive bee Apis cerana

If a honey bee (Apis spp.) colony becomes queenless, about 1/3 of young workers activate their ovaries and produce haploid male-producing eggs. In doing so queenless workers maximize their inclusive fitness because the normal option of vicarious production of relatives via their queen’s eggs is no longer available. But if many workers are engaged in reproduction, how does a queenless colony continue to feed its brood and forage? Here we show that in the Asian hive bee Apis cerana hypopharyngeal gland (HPG) size is larger in queenless workers than in queenright workers and that bees undertaking brood-rearing tasks have larger HPG than same-aged bees that are foraging. In queenless colonies, workers with a smaller number of ovarioles are more likely to have activated ovaries. This reinforces the puzzling observation that a large number of ovarioles reduces reproductive success in queenless A. cerana. It further suggests that reproductive workers either avoid foraging or transition to foraging later in life than non-reproductive workers. Finally, our study also showed that ovary activation and larger-than-average numbers of ovarioles had no statistically detectable influence on foraging specialization for pollen or nectar.     

Endogenous regulation of environmentally induced sexuality in a rotifer: a multigenerational parental effect induced by fertilisation

SUMMARY 1. Sexual reproduction in the heterogonic life cycle of many rotifers occurs when amictic females, which produce diploid eggs developing parthenogenetically into females, are environmentally induced to produce mictic females. Mictic females produce haploid eggs which develop parthenogenetically into males or, if fertilised, into resting eggs – encysted embryos which develop into amictic females after an obligatory diapause. 2. A Florida strain of Brachionus calyciflorus was used to test the prediction that amictic females hatching from resting eggs (Generation 1), and those from the next few parthenogenetic generations, have a lower propensity to produce mictic daughters in response to crowding than those from later parthenogenetic generations. In 10 replicate clones, populations initiated by amictic females from generations 1, 5, 8, 12 and 18 were exposed to a standardised crowding stimulus, and the proportion of mictic females in the populations was determined. These proportions varied significantly across generations and clones. They were very low in the early generations and gradually increased to a mean of about 0.5 at Generation 12. 3. The mechanism for the transgenerational plasticity in response to crowding is not known. One possibility is that resting eggs contain an agent from their fertilised mictic mother's yolk gland that prevents development into mictic females and is transmitted in increasingly low concentrations through successive parthenogenetic generations of amictic females. 4. This parental effect may contribute to clonal fitness by ensuring that a clone developing from a resting egg will attain a higher population size through female parthenogenesis before maximising its commitment to sexual reproduction, even in the presence of a crowding stimulus from a high population density of other clones. Therefore, the number of resting eggs to which a clone contributes its genes should be maximised. 5. The clonal variation in propensity to produce mictic females in this strain indicates genetic variation in the trade‐off between maximising population growth via female parthenogenesis and increasing the probability of producing at least some resting eggs before local extinction from the plankton.     

Demographic correlates of variable egg survival for a tropical lizard

Summary Anolis limifrons is a small iguanid lizard that is found in lowland rainforest in Central America. Important life attributes include early maturity (3–4 mo), multiple clutches of a single egg per breeding season, and low survival. Population turnover is essentially annual as less than 5% adults live more than one year. My objectives were to resolve the following specific questions: 1) Where are eggs laid? 2) Does survival differ among different types of oviposition site? 3) How is the survival of eggs related to the density and age distribution of lizards at different areas? Most eggs are laid beneath litter on the ground. Eggs laid aboveground are placed in accumulations of soil and litter in stumps, crevices in buttressed trees and vines, holes in trees, and on the tops of logs. Eggs were found in aboveground sites in proportion to the abundance of those sites. The major cause of mortality was predation by Solenopsis ants. Judging by the ratio of eggs known to have hatched to those that were predated, survival did not differ among the various types of oviposition site. Study areas with high egg survival in the middle of the wet season had relatively more young (<4–6 mo old) lizards at the end of the wet season than areas with low egg survival. The strong correlation between the relative number of young individuals and egg survival is a consequence of the seasonal cycle of growth and reproduction. Most eggs are laid in the wet season (May–December). Hatchlings complete growth during the dry season (January–April) and become reproductive adults in their second wet season. However, because hatchlings can grow to reproductive size in approximately 3 months, individuals that hatch early in the wet season may themselves produce offspring that will be <4–6 mo old in the late wet season. The relative survival of juveniles (eggs) and adults is an important datum for many theories of life history evolution. For A. limifrons, survival of eggs was two to three times more variable than survival of lizards on both temporal and spatial scales. Comparative data for reptiles are not available to put this information into an evolutionary prespective.     

Spawning habitat and early development of Luciogobius ryukyuensis (Gobiidae)

Egg masses of Luciogobius ryukyuensis were found in spawning grounds around the lowest reach of the adult??s habitat in the tidally influenced area of streams on Okinawa Island. The eggs were attached to the underside of stones and were cared for by a solitary male fish. The number of eggs within an egg mass was 191?C1368. The eggs were elliptical, measuring 2.0?C2.6?mm in length, and 0.6?C0.8?mm in width. Early development of L. ryukyuensis was described from laboratory-reared specimens. Newly hatched larvae, measuring 2.8?C3.3?mm in body length, had an open mouth, pigmented eyes, pectoral fin buds, an orange-colored yolk sac, and characteristic melanophores along the dorsal and ventral midlines of the body. The yolk was completely absorbed at days 2?C3. Notochord flexion began at day 10 and was completed at day 15. The fish started settling on the bottom of the tank at day 34 (14.1?mm in body length) when the body surface started to be covered by intense pigmentation. The eggs and newly hatched larvae of L. ryukyuensis were of standard size of the genus and their morphologies closely resemble those of L. guttatus.