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Some insect species have been proposed as a sustainable alternative to traditional animal‐based food and feed sources. Optimisation of insect production can generally be achieved using two main approaches: optimising environmental conditions and improving traits of interest through selective breeding. These avenues are not inseparable as performance of a genotype might differ between environments due to phenotypic plasticity and because genotypes can respond differently to environmental changes, that is genotype‐by‐environment interactions (G × E). In insect production, diets can be of variable quality and consist of waste‐ and by‐products of low nutritional value, which might result in decreased performance and/or increased trait variability within a population. Therefore, it is of interest to investigate how genotypes perform across various diets. Here, we investigated plasticity and G × E for mean performance and trait variation, which we define as the ability of a genotype to produce consistent phenotypes within and across environments. We did this by rearing 190 full‐sib families of house fly larvae, Musca domestica L. (Diptera: Muscidae), on two diets based on either alfalfa, Medicago sativa L. (Fabales: Fabaceae), or deproteinated grass. Four larval traits were assessed: egg‐to‐larva viability, surface area, dry weight and relative lipid content. Reaction norms were used to investigate the effects of diet on full‐sib family mean and trait variation within and across environments. We found that families reared on the grass‐based diet had higher performance across all investigated traits than families reared on the alfalfa‐based diet. For both mean performance and trait variation, we found G × E for all investigated traits. These findings suggest that there is genetic variation for plasticity (slope of reaction norms) for both trait mean and trait variation, and thus that there is a potential to breed for genotypes with high performance as well as for genotypes with low trait variation within and across diets. [ABSTRACT FROM AUTHOR]

As a factor controlling the vertical distribution of larvae, changes in phototaxis, geotaxis, and sinking velocity concerning larval development in the snow crab (Chionoecetes opilio), a relatively shallower water species, and red snow crab (Chionoecetes japonicus), a relatively deeper water species, were investigated using laboratory-raised individuals. We also measured carapace width and carapace length in all larval stages and the length of the spines seen in the zoeal stages. The phototaxis of the zoeae of both species was strongly positive immediately after hatching, but it gradually changed to neutral. Megalopal phototaxis changed from strongly negative to neutral. The geotaxis of both species was strongly negative only for a few days after hatching, and the red snow crab exhibited stronger negative geotaxis than the snow crab. The sinking velocity of the red snow crab was slower than the snow crab just after hatching but faster in the megalopal stage. Red snow crab showed a greater tendency to float immediately after hatching (stronger negative geotaxis, slower sinking rate), compared to snow crab, and sink more easily in the megalopal stage (faster sinking speed). This might be because the red snow crab hatches and settles at deeper areas than the snow crab. Red snow crab larvae had larger carapace sizes and shorter spine lengths (at the zoeal stages) than the snow crab, which is indicative of adaptations that increase starvation tolerance for longer larval periods and reduce the energy costs of swimming for longer distances (i.e., greater hatching depth) after hatching. [ABSTRACT FROM AUTHOR]

Maternal effects on offspring viability significantly contribute to the productivity and resilience of exploited marine fish populations. The temporal trend of biomass of chub mackerel (Scomber japonicus) in the western North Pacific showed cyclic fluctuation patterns, but it has been rapidly increasing since 2011. Although there are several assumptions regarding the mechanisms of the population dynamics of this species in these waters, there is a contradiction in the effects of thermal environmental conditions on recruitment success. We explored the effects of maternal age and/or previous spawning experience on egg and offspring traits of captive chub mackerel in response to thermal conditions. Moreover, from the relationship between the growth rate and temperature experienced by captive fish, the experienced temperatures of wild specimens were assessed. The sizes of eggs spawned from females aged 1–3 years were negatively correlated with temperature, but the effects of maternal age on egg size and nutrition were significant with larger and nutrient-rich eggs spawned from 2- or 3-year-old females (repeat spawners) than those from 1-year-old females (first-time spawners) at a given temperature. Such temperature- and maternal-age-dependent egg traits reflected the standard length of first-feeding larvae. The effects of maternal age on the starvation tolerance of larvae after hatching and body sizes of first-feeding larvae were also evident in larvae derived from 3-year-old females showing longer starvation tolerance and larger body heights than those from 1-year-old females. Further, larvae derived from 3-year-old females grew significantly faster than those from 1-year-old females at the tested temperatures. The process of ontogenetic development and growth rate of captive specimens until age 25 days were positively correlated with temperature. Meanwhile, the estimated temperatures experienced by wild specimens until age 25 days ranged from 18.0 to 20.3°C. These findings suggested that there were opposing thermal responses between maternal and offspring traits of chub mackerel, but the temperatures experienced by the main recruit fish may be restricted within the range of temperatures available for spawning. We discuss the mechanisms of reproductive success of this species in accordance with the maternal spawning experience and thermal effects on life history traits.

We studied the influences of female pikeperch (Sander lucioperca) length and growth (i.e., maternal effects) on the length of hatched and starved larvae as well as on larval starvation resistance in two different temperature conditions (mean temperatures 13.2 and 17.9°C). The data included fertilised eggs and reared larvae from 21 individuals caught during the spawning season from eutrophic Lake Pyhäjärvi in Finland. The length of the hatching larvae was dependent on female size but also on water temperature and on the potential energy the female had invested on reproduction. Maternal effects seemed to also influence the timing of larvae growth, and larvae that were large at hatching grew less on mere yolk sac reserves, and vice versa. Female length had a positive effect on the larval starvation resistance but only under cold conditions. The results suggest that higher temperature might reduce the advantage the larvae from large females get for starvation resistance. [ABSTRACT FROM AUTHOR]

Metabolism is linked with the pace‐of‐life, co‐varying with survival, growth, and reproduction. Metabolic rates should therefore be under strong selection and, if heritable, become less variable over time. Yet intraspecific variation in metabolic rates is ubiquitous, even after accounting for body mass and temperature. Theory predicts variable selection maintains trait variation, but field estimates of how selection on metabolism varies are rare. We use a model marine invertebrate to estimate selection on metabolic rates in the wild under different competitive environments. Fitness landscapes varied among environments separated by a few centimeters: interspecific competition selected for higher metabolism, and a faster pace‐of‐life, relative to competition‐free environments. Populations experience a mosaic of competitive regimes; we find metabolism mediates a competition‐colonization trade‐off across these regimes. Although high metabolic phenotypes possess greater competitive ability, in the absence of competitors, low metabolic phenotypes are better colonizers. Spatial heterogeneity and the variable selection on metabolic rates that it generates is likely to maintain variation in metabolic rate, despite strong selection in any single environment. [ABSTRACT FROM AUTHOR]

Offspring sizes vary within populations but the reasons are unclear. Game‐theoretic models predict that selection will maintain offspring‐size variation when large offspring are superior competitors (i.e., competition is asymmetric), but small offspring are superior colonizers. Empirical tests are equivocal, however, and typically rely on interspecific comparisons, whereas explicit intraspecific tests are rare. In a field study, we test whether offspring size affects competitive asymmetries using the sessile marine invertebrate, Bugula neritina. Surprisingly, we show that offspring size determines whether interactions are competitive or facilitative—large neighbors strongly facilitated small offspring, but also strongly competed with large offspring. These findings contradict the assumptions of classic theory—that is, large offspring were not superior competitors. Instead, smaller offspring actually benefit from interactions with large offspring—suggesting that asymmetric facilitation, rather than asymmetric competition, operates in our system. We argue that facilitation of small offspring may be more widespread than currently appreciated, and may maintain variation in offspring size via negative frequency‐dependent selection. Offspring size theory has classically viewed offspring interactions through the lens of competition alone, yet our results and those of others suggest that theory should accommodate positive interactions in explorations of offspring‐size variation. [ABSTRACT FROM AUTHOR]

Swimming propagules (embryos and larvae) are a critical component of the life histories of benthic marine animals. Larvae that feed (planktotrophic) have been assumed to swim faster, disperse farther and have more complex behavioural patterns than non-feeding (lecithotrophic) larvae. However, a number of recent studies challenge these early assumptions, suggesting a need to revisit them more formally. The current review presents a quantitative analysis of swimming speed and body size in planktotrophic and lecithotrophic propagules across five major marine phyla (Porifera, Cnidaria, Annelida, Mollusca and Echinodermata). Results of the comparative study showed that swimming speed differences among ciliated propagules can be driven by taxonomy, adult mobility (motile vs sessile) and/or larval nutritional mode. On a phylogenetic level, distinct patterns emerge across phyla and life stages, whereby planktotrophic propagules swim faster in some of them, and lecithotrophic propagules swim faster in others. Interestingly, adults with sessile and sedentary lifestyles produce propagules that swam faster than the propagules produced by motile adults. Understanding similarities and differences among marine propagules associated with different reproductive strategies and adult lifestyles are significant from ecological, evolutionary and applied perspectives. Patterns of swimming can directly impact the dispersal/recruitment potential with incidence on the design of larval rearing methods and marine protected areas. [ABSTRACT FROM AUTHOR]

Synthesis of four decades of Gulf of Alaska ichthyoplankton data indicates that species diversity and total abundance peaks during spring, a common pattern in temperate and sub-arctic ocean regions due to synchrony with the spring peak in plankton production. Nevertheless, fish larvae occur in the plankton at all times of year and peak abundance periods vary significantly by species and habitat. Larval size at hatching and at transformation to the juvenile stage is also highly variable and associated with a variety of larval durations and temporal supply of larval cohorts to pelagic habitats. This phenological diversity represents variability in exposure and adaptation to seasonal cycles in the ocean. Water temperature, winds and currents, and availability of suitable zooplankton prey vary significantly on a seasonal scale affecting degrees of synchrony among larval species with optimal environmental conditions for growth, transport and survival. This synchrony is also affected by interannual shifts in the oceanographic environment, and different early life phenologies among species generate different sensitivities to such interannual variability. Early life history strategies and synchronies are evaluated here and environmental sensitivities are proposed for the numerically dominant species of fish larvae occurring in Gulf of Alaska plankton, including commercially and ecologically important species. For winter to early spring spawners, cold temperatures are an advantage in terms of slowing development so that larvae do not use up all their lipid reserves prior to optimal availability of suitable larval zooplankton prey. Interannual variability in winter temperature may therefore be a good indicator of survival outcomes, especially as influenced by the timing of the switch to exogenous feeding. Variability in temperature-influenced larval growth during late spring and summer months may be less consequential in maintaining synchrony with larval food availability for spring-summer spawners. Rapid growth in association with warm summer conditions facilitates access to a wide size range of prey organisms and minimizes critical periods of vulnerability to trophic mismatch. The Gulf of Alaska is a highly advective environment; storms and alongshore winds promote onshore advection of surface waters. This onshore Ekman transport is strongest during winter and spring when deep water spawned larvae are most abundant over the slope and require access to the shelf. Enhanced shoreward transport of larvae in the canyons intersecting the slope is also an important mechanism. Interannual variability in such transport mechanisms may be critical in determining early ontogeny survival for these species. During all seasons, but especially spring and summer, there are species of larvae for which retention nearshore is vital for survival and mesoscale oceanographic features as well as larval behavioral abilities may be crucial. Annual patterns in phytoplankton and zooplankton production and abundance indicate high-amplitude variation in the composition of prey fields available to larvae, including variability in abundance and the size spectrum of organisms that larvae might encounter and consume. Food limitation seems less likely for larval species that are most abundant in spring-summer than for species with peak abundance in winter-spring. It is probable that the more selective a species is in terms of zooplankton prey, the more susceptible that species is to a trophic mismatch. Species-specific intrinsic rates and morphological development during early ontogeny also influence the interaction of larvae with their environment, and larval growth trajectories can be quite different even among species with identical early life phenology. This insight clearly indicates that although phenology is critical, timing is not everything and all fish larvae are not equal. For the 23 species and two genera of fish in this study, a synoptic overview is provided of their early ontogeny environmental synchronies and proposed sensitivities. This ecological synthesis of phenologies helps us characterize vulnerability and resilience factors for intervals of the planktonic phase in the pelagic environment. It also identifies environmental signals that could be tested as species-specific ecosystem indicators of population trends for fish stocks in the Gulf of Alaska. Further, understanding seasonal dynamics in the ichthyoplankton is considered important for gauging food availability and energy flow more broadly in this and other pelagic ecosystems, as well as to understanding environmental forcing on the fish populations themselves. [ABSTRACT FROM AUTHOR]

A shift in the relative arrival of offspring, for example a shift in hatching time, can affect competition at the intraspecific level through size‐mediated priority effects, where the larger individuals gain more resources. These priority effects are likely to be affected by climate warming and the rate of intraspecific predation, that is cannibalism.In a laboratory experiment, we examined size‐mediated priority effects in larvae of the univoltine damselfly, Lestes sponsa, at two different temperatures (21 and 23°C). We created three size groups of larvae by manipulating hatching time: early hatched with a large size (extra‐advanced), intermediate hatched with an intermediate size (advanced) and late hatched with a small size (non‐advanced). Thereafter, we reared the larvae from these groups in non‐mixed and mixed groups of 12 larvae.We found strong priority and temperature effects. First, extra‐advanced larvae most often had higher survival, growth and development rates than non‐advanced larvae in mixed groups, compared to groups that consisted of only extra‐advanced larvae. Second, temperature increased growth and development rates and cannibalism.However, the strength of priority effects did not differ between the two experimental temperatures, because there was no statistical interaction between temperature and treatments. That is, the mixed and non‐mixed groups of non‐advanced, advanced and extra‐advanced larvae showed the same relative change in life‐history traits across the two temperatures.Non‐advanced and advanced larvae had similar or higher growth rate and mass in mixed groups compared to non‐mixed groups, suggesting that predation from advanced larvae in the mixed group released resources for the non‐advanced and advanced larvae that survived despite cannibalism risk. Thus, a thinning effect occurred due to cannibalism caused by priority effects.The results suggest that a shift in the relative arrival of offspring can cause temperature‐dependent priority effects, mediated through cannibalism, growth and development, which may change the size distribution and abundance of emerging aquatic insects. Shifts in the relative hatching of offspring can lead size‐mediated priority effects. This study shows that such priority effects have a twofold advantage in early‐hatching individuals: higher growth and higher cannibalism on early‐hatching individuals. In addition, a two‐degree higher temperature increased growth and cannibalism. [ABSTRACT FROM AUTHOR]

Temperature often affects maternal investment in offspring. Across and within species, mothers in colder environments generally produce larger offspring than mothers in warmer environments, but the underlying drivers of this relationship remain unresolved. We formally evaluated the ubiquity of the temperature–offspring size relationship and found strong support for a negative relationship across a wide variety of ectotherms. We then tested an explanation for this relationship that formally links life‐history and metabolic theories. We estimated the costs of development across temperatures using a series of laboratory experiments on model organisms, and a meta‐analysis across 72 species of ectotherms spanning five phyla. We found that both metabolic and developmental rates increase with temperature, but developmental rate is more temperature sensitive than metabolic rate, such that the overall costs of development decrease with temperature. Hence, within a species' natural temperature range, development at relatively cooler temperatures requires mothers to produce larger, better provisioned offspring. [ABSTRACT FROM AUTHOR]

Abstract Background Anopheles mosquito life-history parameters and population dynamics strongly influence malaria transmission, and environmental factors, particularly temperature, strongly affect these parameters. There are currently some studies on how temperature affects Anopheles gambiae s.s. survival but very few exist examining other life-history traits. We investigate here the effect of temperature on population dynamics parameters. Methods Anopheles gambiae s.s. immatures were reared individually at 23 ± 1 °C, 27 ± 1 °C, 31 ± 1 °C, and 35 ± 1 °C, and adults were held at their larval temperature or at one of the other temperatures. Larvae were checked every 24 h for development to the next stage and measured for size; wing length was measured as a proxy for adult size. Females were blood fed three times, and the number of females feeding and laying eggs was counted. The numbers of eggs and percentage of eggs hatched were recorded. Results Increasing temperatures during the larval stages resulted in significantly smaller larvae (p = 0.005) and smaller adults (p

Early post-settlement mortality is difficult to measure in mobile benthic taxa such as mussels. Field studies typically employ settlement collectors that often contain empty shells of dead individuals, which are usually disregarded. Here, empty shells of pediveligers, i.e. recent settlers that died before beginning to grow as juveniles, were used to assess temporal and spatial patterns of early mortality in mussels, whether size at settlement determined mortality, and whether mortality was density-dependent. This study took place at two intertidal sites in a large harbour in central New Zealand where monthly cohorts of mussels were collected over a 2-year period. Monthly mortality varied substantially, ranging from 0% to 42.6%, but not across the two sites that were 27 km apart. Although there was no density-dependent mortality evident within cohorts, the proportion of pediveligers which were dead on collection was highly positively correlated across sites. Live settlers were on average larger than dead settlers, and the size distribution of dead settlers was shifted toward smaller sizes compared to live settlers. At the extremes, of all settlers with shell length of 260 µm or less, 72% were dead on collection. By contrast, for settlers 310 µm or greater in length, 6% were dead. Together, these results (1) suggest that in this system size at settlement may be an important determinant of very early, peri-metamorphic mortality in mussels, with smaller settlers at higher risk, and (2) demonstrate the value in evaluating dead pediveligers for assessing natural early post-settlement mortality in mussels. [ABSTRACT FROM AUTHOR]

In fisheries science, stock density is one of the fundamental factors that affect growth and condition. However, reproductive traits like fecundity and also the size and quality of offspring (via maternal effects) can be modified by stock density. In the short-living freshwater fish species vendace ( Coregonus albula ), the impact of stock density via maternal condition on quantity and quality of eggs and larvae was often proposed as a driver of population fluctuations, but such mechanisms have only rarely been evaluated. We systematically analysed growth, female condition and reproductive traits (fecundity, egg size, hatching rate and size of hatchlings) of vendace in relation to stock density across three lakes over two years. Across populations of contrasting density, length at first maturity, female condition and relative fecundity strongly reflected the difference in stock density, while size of eggs and larvae and hatching success at artificial breeding were not correlated with stock density. Our results indicate that density-dependent female spawner traits do not alter reproductive success, but vendace maintain egg size and hatching rate at the expense of egg quantity even at low per-capita resource availability. Accordingly, the reproductive potential of vendace stocks is primarily driven by spawning stock biomass and relative fecundity. We conclude that besides spawning stock biomass and relative fecundity, the additional inclusion of spawner condition into stock assessment has little potential to improve vendace fisheries management. [ABSTRACT FROM AUTHOR]

Fish differentially provision resources to eggs and larvae to optimise survival during the critical early life-history period. Resource allocation is limited by a trade-off between egg size and fecundity, and the optimal strategy varies with habitat type. This study examines the consequences of egg size differences for the early life-histories of four closely related galaxiid species which occur in contrasting habitat types on the South Island, New Zealand. Headwater species had substantially larger water-hardened eggs, longer incubation times, and newly hatched larvae were on average up to 41% longer than lower catchment species. Significant interspecific differences in gape diameter, eye diameter and myomere depth were also observed. Swimming ability was positively associated with larval length at hatch. Interspecific differences in length and swimming ability were generally maintained throughout the larval period, despite larvae being reared under relatively benign conditions where many other studies suggest initial differences should disappear. These results demonstrate the consequences of differential maternal provisioning to the egg for larval traits. The larger larvae of headwater species are likely to be more resistant to starvation and have improved foraging ability compared to lower catchment species; traits which are likely to confer them survival advantages in the low productivity, food-scarce environments they occupy. The smaller larvae of lower catchment species are likely to be a consequence of females investing in fecundity in these relatively resource-rich streams. [ABSTRACT FROM AUTHOR]

Little experimental evidence of multiple generations of inbreeding depression is available for marine invertebrates. Here, we report that two generations of inbreeding significantly reduced larval growth and metamorphosis, but did not significantly impact fertilization and hatching in the sea urchin Strongylocentrotus intermedius . A higher inbreeding coefficient had significantly more negative impacts on some traits of S. intermedius larvae (for example, larval length) but not all. Maternal effects of inbreeding depression probably appear in the eight-arm stage and metamorphosis of S. intermedius . The present study provides convincing evidence of inbreeding depression on larval growth and metamorphosis in S. intermedius and highlights the importance of avoiding multiple generations of inbreeding in sea urchin aquaculture. Statement of relevance Multiple inbreeding dramatically impacts aquaculture of marine species. Here, we investigated effects of second generation of inbreeding on fertilization, hatching, larval growth and metamorphosis in sea urchins. The present study provides the convincing evidence on the inbreeding depression of larval growth and metamorphosis in sea urchins and highlights the importance of avoiding multiple generation of inbreeding in sea urchin aquaculture. [ABSTRACT FROM AUTHOR]

Background: Anopheles mosquito life-history parameters and population dynamics strongly influence malaria transmission, and environmental factors, particularly temperature, strongly affect these parameters. There are currently some studies on how temperature affects Anopheles gambiae s.s. survival but very few exist examining other life-history traits. We investigate here the effect of temperature on population dynamics parameters. Methods: Anopheles gambiae s.s. immatures were reared individually at 23 ± 1 °C, 27 ± 1 °C, 31 ± 1 °C, and 35 ± 1 °C, and adults were held at their larval temperature or at one of the other temperatures. Larvae were checked every 24 h for development to the next stage and measured for size; wing length was measured as a proxy for adult size. Females were blood fed three times, and the number of females feeding and laying eggs was counted. The numbers of eggs and percentage of eggs hatched were recorded. Results: Increasing temperatures during the larval stages resulted in significantly smaller larvae (p = 0.005) and smaller adults (p < 0.001). Adult temperature had no effect on the time to egg laying, and the larval temperature of adults only affected the incubation period of the first egg batch. Temperature influenced the time to hatching of eggs, as well as the time to development at every stage. The number of eggs laid was highest when adults were kept at 27 °C, and lowest at 31 °C, and higher adult temperatures decreased the proportion of eggs hatching after the second and third blood meal. Higher adult temperatures significantly decreased the probability of blood feeding, but the larval temperature of adults had no influence on the probability of taking a blood meal. Differences were observed between the first, second, and third blood meal in the times to egg laying and hatching, number of eggs laid, and probabilities of feeding and laying eggs. Conclusions: Our study shows that environmental temperature during the larval stages as well as during the adult stages affects Anopheles life-history parameters. Data on how temperature and other climatic factors affect vector life-history parameters are necessary to parameterise more reliably models predicting how global warming may influence malaria transmission. [ABSTRACT FROM AUTHOR]

Free-spawning species of chitons produce eggs enclosed in a coating known as the hull. In Chitonida, several studies have shown that the hull helps to direct sperm to specific areas of the egg surface, facilitating fertilization. One study has found evidence that this structure also serves to reduce the sinking rates of the eggs. To clarify how the presence of the hull modifies sinking rates in chiton eggs, here we compare sinking speeds and densities of eggs of Mopalia kennerleyi with and without the hull. Sinking rates of eggs with the hull were approximately one-third of those without it. This structure acts as a flotation device because it has a density very close to that of seawater, and it increases the effective diameter and therefore the drag on the negatively buoyant egg. Since there is limited knowledge about morphology and behavior of chiton larvae, we also analyzed changes during ontogeny in behavior, swimming speeds, and body shape of larvae of M. kennerleyi. Over time, the larvae decreased their upward swimming tendency and preferred to stay near the bottom, and their bodies became elongated and dorso-ventrally compressed. These changes may be related to preparation for settlement and metamorphosis. Further studies of these subjects are required in chitons, since movement of early stages, as eggs/embryos sinking or larvae swimming in the water column, may affect their survival. [ABSTRACT FROM AUTHOR]

In this study, 11 wild male brood fish were used and their mean ages were 15.08 ± 1.66. The luteinizing hormone-releasing hormone analogue (LH-RH-A2) was used to stimulate twice in few days interval (3-7 days) and then semen samples were stripped. The results showed that there was significant difference among the percentage of motile spermatozoa, sperm density and spermatocrit during two strippings ( P < 0.05). The duration of sperm motility in first and second stripping was 315/83 ± 162.16 and 212.5 ± 110.53 s respectively. Also, sperm pH was 8.41 ± 0.53 and 8.05 ± 0.33 in first and second stripping respectively. There was significant differences between hatching rate, as well as larvae size significantly changed in both hatching and initiation of active feeding ( P < 0.05). [ABSTRACT FROM AUTHOR]

Black flies are ubiquitous and important members of lotic ecosystems. Size is known to affect many aspects of their life in the aquatic larval stage, including intraspecific competition for feeding sites. As filter feeders, flow affects their ability to feed and reach sufficiently fast flow. This, in turn, can lead to risky fluid-mediated dispersal behavior in search of better conditions. It is surprising, therefore, that little information is available regarding how physiological and environmental factors combine to affect larval growth rates. The present study determines the relative growth rates of small (0.6 mm) and large (approximately 4 mm) larvae in laboratory flumes designed to produce spatially homogeneous and temporally consistent flow regimes at ecologically relevant velocities (44 and 64 cm/s). Our results indicate that size and flow both influence growth rates and that the 2 interact significantly. Young larvae exhibit faster growth rates and a greater positive response to increased flow speed. This result might help explain why smaller larvae have a greater propensity to disperse than larger larvae: the benefit of increased growth rate that they receive from relocating to faster flow might balance the risks inherent in dispersal. [ABSTRACT FROM AUTHOR]

. 1. Today, forest fragmentation is one of the major threats to biodiversity worldwide. In this context, fragmented populations of specialised forest organisms face an increasing risk of extinction because of factors such as local food scarcity. Nonetheless, the role of food availability may differ depending on organism size, which is expected to determine the energy requirements and mobility between fragments. 2. A field study was carried out on Curculio elephas, a forest beetle with low dispersal potential, whose larval development takes place in oak Quercus spp. acorns. 3. For a similar seed crop per tree, acorn size was larger in isolated oaks than in trees located in forest patches. Thus, fragmentation increased local food availability for C. elephas. Larger acorns enabled larval size to increase, a key fitness proxy associated with individual survival, adult size, and potential female fecundity. Indeed, the number of both adults and larvae was higher in isolated trees than in forest patches. 4. In the current scenario of increasing forest fragmentation, the survival likelihood of specialist insects may strongly depend on their ability to adapt to altered environmental conditions. To the best of our knowledge, this is the first study to report on how some forest insects may take advantage of fragmentation-mediated changes to survive in isolated trees. 5. From a conservation perspective, management policies should preserve isolated trees as a source of seeds and fauna for the natural regeneration of forest ecosystems after unproductive farmlands have been abandoned. [ABSTRACT FROM AUTHOR]

1. Mothers must balance the fecundity costs of increasing propagule size with the fitness benefits of increased propagule performance, and the propagule size-performance relationship is crucial for determining this trade-off. 2. While many studies have examined the propagule size-performance relationship in individual life-history stages, very few have examined the relationship between propagule size and performance across multiple life-history stages despite the ubiquity of complex life cycles. 3. We examined the consistency of the propagule size-performance relationship across several life-history stages in the marine invertebrate Microcosmus squamiger (Ascidiacea). 4. Propagule size had effects in some life-history stages and not others: larger propagules hatched sooner as larvae and grew more as juveniles in the field. On the other hand, propagule size had no effect on cell cleavage rates, larval swimming time or post-metamorphic survival in the field. 5. The effects of propagule size on juvenile size were persistent – juveniles that came from larger propagules were still larger than juveniles that came from smaller propagules after 11 weeks in the field. 6. We found no evidence of conflicting selection pressures on propagule size among life-history stages. Rather, in this species at least, the selection on propagule size at both the larval and juvenile stage appeared to favour the production of larger propagules. Nevertheless, the slope of the relationship between propagule size and performance was highly variable among life-history stages. 7. The effects of propagule size across multiple life-history stages are determined by the strength of selection pressures, which can be highly variable in organisms with complex life-cycles. [ABSTRACT FROM AUTHOR]

Replenishment of many marine populations occurs through the entry of juveniles to adult populations following a pelagic larval stage. Because mortality during the pelagic stage is thought to be high and density independent, larval abundance and traits of individual larvae should have strong effects on overall population dynamics in marine organisms. Surprisingly, few experiments have tested how localized interactions among breeding adults affect the quantity and phenotypic traits of larvae they produce. Here I experimentally test for the influence of food competition, mate limitation, and population density on somatic growth, fecundity, and offspring provisioning (larval length and energy reserves) in a planktivorous, territorial coral reef damselfish, Stegastes partitus. I manipulated food supply and adult S. part itus density on isolated patch reefs in the Bahamas and also made behavioral observations of S. partitus occurring on nearby natural reefs at a range of population densities. On the experimental reefs, females experienced density-dependent growth and fecundity; male reproductive success was density dependent, but male growth was not. Density-dependent growth and reproduction were not moderated by food supplementation, and density-dependent reproduction was not influenced by mate availability. On natural reefs, the frequency of aggressive interactions, particularly involving females, increased with population density, implicating aggression-related energetic costs as the source of both forms of density dependence in the experiments. Food supplementation increased female somatic growth and larval energy reserves, suggesting that females allocated surplus energy to future reproductive potential and enhanced offspring quality. Neither experimental treatment affected larval length. By altering patterns of reproduction, the interplay between spatial variation in food availability and population density may drive population dynamics in a broad range of benthic marine organisms. [ABSTRACT FROM AUTHOR]

This study examined the correlation between egg size and a number of variables in the subsequent larval stages of the Persian sturgeon Acipenser persicus. Nineteen female sturgeons were fertilized and the eggs were harvested. The results showed that there were positive, significant correlations (p < 0.05) between egg size and several dependent variables including larval weight and duration of hatching time as well as the volume of the yolk sac and the hatching time. The weight of larvae at 2, 4, 6 and 8 days post hatching showed positive and significant correlation (p < 0.05) with egg size. Total length of larvae at 2, 4, 6, 8 and 10 days post hatching had significant correlation (p < 0.05) with egg size in all cases. During yolk sac absorption at 2, 4, 6, 8 and 10 days after hatching correlations gradually decreased. There was no significant correlation between egg size and mortality during the yolk sac absorption period (r = -0.24, p = 0.314) or the first feeding stage (r = -0.05, p = 0.840). [ABSTRACT FROM AUTHOR]

Abstract: The Amazon River prawn, Macrobrachium amazonicum (Heller, 1862), is a target species for regional fisheries in Brazil and a candidate for aquaculture. Under controlled laboratory conditions (29 °C, 10‰), the larval phase of this species shows variability in the morphology and number of successive stages (mostly 9–10, occasionally 8 to >12). In the most commonly observed developmental pathway (9 stages, taking approximately 20–22 days from hatching to the first juvenile stage), we studied patterns of larval growth in terms of total body length (TL), carapace length (CL), dry mass (W), and elemental composition (carbon, hydrogen, nitrogen; collectively CHN). At hatching, about 12% of late embryonic W, 15–18% of C and H, but only 7% of N were lost, indicating higher losses of lipids and/or carbohydrates than proteins. Significant variability was observed in the initial biomass and elemental composition of newly hatched larvae from 20 different egg batches. This may cause variation in the endotrophic potential of the early stages, as the zoea I of this species is a non-feeding stage, and also the zoea II may still utilize internal energy stores remaining from the egg yolk. Lacking or low larval feeding activity from hatching through stage II coincided with low initial growth. Concomitantly, the proportions of C and H (in % of W) as well as the C:N ratio decreased from hatching through stage IV, indicating a utilization of stored lipids. The percentage of N showed an opposite pattern, reflecting protein synthesis associated with morphogenesis. Size growth showed maximum increments per moult in the late zoeal stages (III–VI), followed by lower increments in the subsequent decapodid stages (VII–IX). This sigmoidal growth pattern may reflect ontogenetic changes in morphometric relationships. Biomass showed exponential patterns of increase from zoeal stage III throughout later larval development and in the first two juvenile stages. Furthermore, patterns of larval growth in M. amazonicum are characterized as linear relationships between larval W in stage n and that in stage n +1 (Hiatt diagram), between larval size (CL) and biomass (W, C), and between W and either C or N. Using CHN data, we also provide estimates of the protein and lipid contents of larval biomass (ca. 38–46% and 10–12% of W, respectively). High survival, rapid development, and predictable patterns of larval growth support the assumption that M. amazonicum should be a suitable species for production in aquaculture. [Copyright &y& Elsevier]

1. The abscission of seeds infested by insects is common in many plants and has been proposed as a defensive mechanism, although its negative consequences for insects have rarely been assessed. 2. We assessed the consequences of seed abscission studying the interactions between the holm oak Quercus ilex and the chestnut weevil Curculio elephas, its main pre-dispersal seed predator. Female weevils oviposit into the acorns and the larvae must complete their development inside a single acorn feeding on the cotyledons. The growth of the infested acorns is suppressed because they are prematurely abscised. 3. Female weevils oviposit along the acorn growing period; hence, the size of the infested acorns increased with date. The growth of the larvae inside the smaller, early infested, acorns was constrained because food (i.e. cotyledons) was frequently depleted. Larval size increased with the date along with the size of the infested acorns, but it declined slightly in the latest dates as a result of the higher conspecific competition provoked by the larger number of larvae per acorn. 4. The present results demonstrate that premature seed abscission by Q. ilex had negative consequences for C. elephas, as a smaller acorn size reduced food availability and constrained larval size, a key insect life history trait. At the same time, it is suggested that the growth suppression of infested acorns may condition the oviposition phenology of these insects according to their body size. These results need to be considered in further research in the context of the evolutionary significance of premature seed abscission as a defensive mechanism. [ABSTRACT FROM AUTHOR]

Predaceous larvae of the water scavenger beetle Tropisternus setiger (Germar) are common inhabitants of variable environments in which prey availability may vary widely. We conducted laboratory experiments to assess the effect of prey density on developmental times and survivorship of the preimaginal stages of T. setiger. We also examined the effect of the number of consumed prey on the larval size of instar III. Four different prey densities (one, two, four, and eight preys a day) were tested and both developmental time and survivorship differed significantly among them. Larvae fed one or two preys daily showed a longer developmental time and a lower survivorship than larvae fed four or eight preys a day. Moreover the consumption of four preys a day increased larval developmental success, and to consume one prey a day affected survivorship through the larval period. On the other hand, prey density had no effect on the final larval size. [ABSTRACT FROM AUTHOR]

Most marine populations are sustained by the entry of juveniles that have survived the larval phase, during which time most die. The number of survivors depends strongly on the quality of the eggs produced by spawning females, but it is not known how the social conditions under which breeding occurs influence the quality of larvae produced. Here I show that the density of females interacting with breeding mothers directly influences the size of larvae produced, through a stress-related mechanism. On the Great Barrier Reef of Australia, breeding pairs of a damselfish, Pomacentrus amboinensis, were isolated on habitat patches, and additional females that could not access the spawning site were added at four densities (0, 1, 3, or 6 females). Additional females increased aggressive interactions by mothers and increased the levels of the stress hormone, cortisol, in their ovaries, leading to reduced larval size. Neither egg output nor yolk size of the larvae was influenced by female density. Pairs breeding in isolation produced the largest larvae; current theory suggests that these larvae should contribute most to subsequent population replenishment events. This social mechanism may influence which females effectively contribute to the next generation and may promote resilience in patchy or isolated populations. [ABSTRACT FROM AUTHOR]

Abstract: We assessed batch fecundity of the swimming cab Portunus trituberculatus for the purpose of seed production. Oocyte number and number and body size of first zoeas were examined for females collected from natural habitats in the Seto Inland Sea of Japan. The relationships between carapace width (CW) of females and batch fecundity were analyzed using a power function. Oocyte number was examined for the overwintering females. Size and number of first zoeas were determined for ovigerous females collected from May to August. Oocyte number increased with increasing female body size and predicted estimates ranged between 0.8 and 4.5 million for CW of 130–240 mm. Size of first zoeas (distance between tips of dorsal and rostral spines of the carapace) ranged between 1.22 and 1.62 mm and tended to linearly decrease with advancing hatching date, i.e., increasing hatching temperatures. Number of first zoeas increased with female body size and showed no fluctuation throughout the breeding season in females of the same size. Predicted numbers of first zoeas ranged between 0.7 and 3.8 million for CW of 130–240 mm. Number of first zoeas being less than the oocyte number for females of the same size, it is suggested that egg loss occurred from oviposition to hatching. [Copyright &y& Elsevier]

1. In libellulids, egg size differs between species and populations. There are also size differences within egg clutches of individual females. 2. Past experiments suggest that there are two different types of egg clutches in libellulids. Egg size decreases significantly during oviposition in species that perform non-contact guarding during oviposition. In contrast, in species ovipositing in tandem, egg size is randomly distributed. 3. This study deals with the possible consequences of egg size variation within the different egg clutch types. The study examined whether there is a correlation between egg development time, offspring sex or larval size and egg size. 4. The current experiments were conducted in Namibia and Germany. Five non-contact guarding and four tandem guarding libellulid species were used. 5. In some species larger eggs needed more time to develop, in some species no correlation between egg size and egg development time could be found, whereas in other species larger eggs developed faster. 6. The sex ratio was biased towards females in Leucorrhinia dubia and in Sympetrum striolatum and egg size was not associated with gender. 7. In both egg clutch types larger eggs resulted in larger larvae. In this study, evidence was found that the effects of egg size diminished with progressing larval development under good conditions. However, it is possible that the effects may have a greater influence under harsh circumstances. [ABSTRACT FROM AUTHOR]

The effect of turbulence, light level, and ontogeny on herring larva''s attack rate and swimming activity was tested in a previous study. However, during larval seasons (spring and autumn), water clarity is frequently impaired by alga blooms, which also most probably will affect larva feeding rate. Therefore, this study was to investigate the effects of turbidity, turbulence, and ontogeny on the attack rate and swimming activity of herring larvae. By adding diatomaceous earth (DE) to the water, three turbidity levels were established: 0, 35, and 80 Jackson Turbidity Unit [JTU; which coincide with a beam attenuation (c) of 0.1, 2.5, and 4.8 m-1, respectively]. An unfavourable (8×10-6 W/kg) and a favourable turbulence level (1×10-6 W/kg) were chosen based on results from the earlier study. The results show that intermediate turbidity (35 JTU) has a positive effect on the attack rate of smaller larvae (20 mm), while high turbidity (80 JTU) has a negative effect on attack rate of all tested larvae size groups. In general, attack rate was lower at the highest turbulence compared to the low level, independent of turbidity level. However, there was one exception, when turbidity was at the highest, the largest larvae (29 mm) seemed to gain from feeding in the highest turbulence level. The overall activity level was higher in the presented study than in the earlier study without turbidity. The favourable turbidity level (35 JTU) coincides with turbidity levels normally found at the equivalent depth during spring and autumn blooms in the area of where the experimental larvae originate. In addition, turbidity''s effect on light absorbtion and how it influences the maximum feeding depth of the larva are discussed. [Copyright &y& Elsevier]