Hatching Size Research Articles

Optimizing Interfaces in Laser-Brazed Ceramic-Stainless Steel Joints for Hydrothermal Sensors through Finite-Element Modeling

The development of reliable joining techniques for ceramics and metals is crucial for energy applications, such as fuel cells, nuclear reactors, and high-temperature sensors, most especially for the sealing of hydrothermal sensors to study multiphase flows. However, during one-step active laser brazing it is a serious problem that a high thermal stress concentration can occur at the joint interfaces or on the ceramic side of the joint due to mismatches between the CTEs (coefficients of thermal expansion) and/or elastic constants. The uncontrolled thermal residual stress can lead to cracks and defects in the brazement. In the present work, an elastoplastic finite element method/numerical model was formulated to study the thermal residual stresses developed in the brazement between ceramics and austenitic stainless steel during cooling in active laser brazing. Calculations and comparison experiments were conducted to validate the simulated stress distribution in un-patterned ceramics. Stress analyses were conducted for planar and cylindrical specimen geometries (lab joints) relevant for miniaturized energy sensors. Laser interface patterning was employed to create micro-scale features on ceramic interfaces that reduce thermal stress concentrations. The optimization of the interface designing parameters including hatch size, structure width, pattern depth and metal/ceramic thickness ratio was performed using the Taguchi method with orthogonal arrays. The study suggests that laser interface structuring can modify thermal residual stresses in ceramic-to-metal brazements, thereby increasing the reliability of active brazing joints.

Embryonic encapsulated development of the gastropod Acanthina monodon is impacted by future environmental changes of temperature and pCO2

Egg capsules of the gastropod Acanthina monodon were maintained during the entire period of encapsulated development at three temperatures (10, 15, 20 °C) and two pCO2 levels (400, 1200 μatm). Embryos per capsule, size at hatching, time to hatching, embryonic metabolic rates, and the resistance of juveniles to shell breakage were quantified. No embryos maintained at 20 °C developed to hatching. The combination of temperature and pCO2 levels had synergistic effects on hatching time and developmental success, antagonistic effects on number of hatchlings per capsule, resistance to juvenile shell cracking and metabolism, and additive effect on hatching size. Juveniles hatched significantly sooner at 15 °C, independent of the pCO2 level that they had been exposed to, while individuals hatched at significantly smaller sizes if they had been held under 15 °C/1200 μatm rather than at 10 °C/low pCO2. Embryos held at the higher pCO2 had a significantly greater percentage of abnormalities. For capsules maintained at low pCO2 and 15 °C, emerging juveniles had less resistance to shell breakage. Embryonic metabolism was significantly higher at 15 °C than at 10 °C, independent of pCO2 level. The lower metabolism occurred in embryos maintained at the higher pCO2 level. Thus, in this study, temperature was the factor that had the greatest effect on the encapsulated development of A. monodon, increasing the metabolism of the embryos and consequently accelerating development, which was expressed in a shorter intracapsular development time, but with smaller individuals at hatching and a lower resistance of their shells to breakage. On the other hand, the high pCO2 level suppressed metabolism, prolonged intracapsular development, and promoted more incomplete development of the embryos. However, the combination of the two factors can mitigate--to some extent--the adverse effects of both incomplete development and lower resistance to shell breakage.

Relationships between female size, egg size, clutch size, and hatchling size in Morelet’s crocodile

Resources are limited by the environment in which an individual is found and can be influenced by natural selection. Evolutionary trade-offs in the reptilian reproductive effort literature have focused on optimal egg size. The objective of this study was to test egg size, clutch size, female size and hatching size in Morelet’s Crocodile (Crocodylus moreletii). Thirteen nests, 13 post-oviposition females, and 434 eggs were evaluated, from which 292 (67.2%) neonates hatched. No correlation was found between clutch size and egg size; however, the Gaussian model best explained the relationship between egg volume and mass. The relationship between TL of the female and egg size may be explained in that the size of the egg has a defined limit even when the female continues to increase in TL. Other factors may influence clutch size, such as environmental factors, reproductive adult quality, diet, the of the females, and captive conditions.

Timing of parental breeding shapes sensitivity to nitrate pollution in the common frog Rana temporaria

Climate change is expected to increase mean temperatures and the frequency of extreme weather events, that can lead to earlier/extended breeding seasons in temperate taxa. As a consequence, many organisms that show climate-induced phenological shifts might be exposed to environmental conditions they are not well adapted to while breeding, and their ability to cope with stressful conditions might be influenced. Here, we investigated how parental breeding time shapes the sensitivity to nitrate exposure at three consecutive life stages (embryonic, larval, juvenile) in the European common frog (Rana temporaria). We compared hatching success and life-stage specific survival, growth, standard metabolic rate, body condition, and acute thermal sensitivity of offspring from an earlier-breeding parental cohort (early cohort) vs. a later-breeding parental cohort (late cohort) exposed to a range of environmentally relevant concentrations of nitrate (0–100 mg/L). We also investigated whether nitrate exposure experienced during the embryonic and larval stages affects physiological performance in later life stages (after metamorphosis). Our study reveals that parental breeding time affects the sensitivity to nitrate pollution at three consecutive life stages in Rana temporaria. Breeding later in spring reduced hatching size and survival at high nitrate exposure, but also induced compensatory growth of the offspring. In both early and late cohorts, exposure to nitrate pollution reduced developmental rate and led to larger, but older larvae at the onset of metamorphosis with a greater sensitivity to warmer environmental temperatures. Standard metabolic rate, on the contrary, was neither affected by parental breeding time nor by exposure to nitrate. Exposure to nitrate pollution during embryonic and larval development led to carry-over in juvenile froglets as their sensitivity to temperature was higher. In a world highly impacted by humans, it is thus essential to give stressors a more holistic approach in order to better predict their consequences on species subjected to them.

Effects of Shape Factors on Rotating Bending Fatigue Property of Al Alloys Fabricated by Metal Additive Manufacturing Technology

Metal additive manufacturing technology can easily produce metal parts with complex shapes and is being considered for application in a variety of fields. However, it is known that the fatigue strength of products manufactured using this technology is low due to internal porosity and surface roughness generated during fabrication. In this study, the effect of stress concentration sources on the rotating bending fatigue strength of aluminum alloys, AlSi10Mg alloys, which is expected to be applied to lightweight components, it was examined by changing the hatch size. The results of tests using a quadruple rotating bending fatigue tester showed that surface treatment to remove stress concentration sources significantly improved fatigue strength. Furthermore, it was considered that the variation in the size of near-surface defects in the smoothed specimens may affect the variation in fatigue life.

Ecological and behavioural drivers of offspring size in marine teleost fishes

AbstractAimOur aim was to evaluate the role of ecological and life‐history factors in shaping global variation in offspring size in a marine clade with a diverse range of parental care behaviours.LocationGlobal.Time periodData sourced from literature published from 1953 until 2019.Major taxa studiedMarine teleost fishes.MethodsWe compiled a species‐level dataset of egg and hatch size for 1,639 species of marine fish across 45 orders. We used Bayesian phylogenetic mixed models to evaluate the relationship between offspring size and environmental factors (i.e., mean temperature, chlorophyll‐a and dissolved oxygen content together with their annual variation), as well as latitude, reproductive strategy, parental body size and fecundity. We also tested long‐standing hypotheses about the co‐evolution of offspring size and the presence of parental care in BayesTraits.ResultsAfter controlling for parental body size and phylogenetic history, we find that increased egg size is associated with colder and oxygen‐rich waters, while hatch size further depends on food supply and the reproductive strategy exhibited by the species. Irrespective of the initial investment in egg size, species with parental care or demersal egg development yield larger hatchlings compared to pelagic spawners. We also demonstrate that hatch size has co‐evolved with advanced forms of care in association with parental body but fail to find a relationship with other types of care.Main conclusionsOur study shows that parental care behaviours, together with environmental context, influence the evolution of classic life‐history trade‐offs on a global scale. While the initial investment in eggs is driven primarily by temperature and oxygen content, hatch size also reflects the impact of care an offspring has received throughout development. In support of the ‘offspring‐first’ hypothesis, we find that an increase in hatch size drives the evolution of advanced care provision.

Maternal Temperature, Corticosterone, and Body Condition as Mediators of Maternal Effects in Jacky Dragons (Amphibolurus muricatus).

AbstractTemperature is a crucial environmental component that imposes physiological constraints and ultimately produces variation in life-history traits. Temperatures experienced by mothers can influence offspring phenotypes, including growth and sex ratios, especially in ectothermic species. However, mechanisms by which thermal information can be passed onto offspring have been underexplored. Here, we investigated corticosterone as a potential mediator of thermal maternal effects. We held female jacky dragons (Amphibolurus muricatus) in two different thermal regimes (short [7 h] or long [11 h] basking treatments), then quantified plasma corticosterone levels and tested for correlations between the resulting corticosterone levels and reproductive outputs. Lizards in the long-bask treatment had significantly higher corticosterone levels than those in the short-bask treatment. Maternal corticosterone, in turn, had sex-dependent effects on offspring hatching size but was not associated with maternal reproductive effort or offspring sex or growth. In contrast, maternal body condition was strongly positively related to both reproductive output (including clutch size and total number of eggs) and offspring size at hatching but had no effect on offspring growth. Basking treatment also interacted with condition and corticosterone to affect egg mass and hatchling snout-vent length, respectively. When we tested for relationships between corticosterone levels and body condition, we found corticosterone to be negatively related to condition in long-bask lizards but only in the postbreeding season. These findings indicate that thermal opportunity alters physiology, with potential consequences for fitness. Moreover, the results suggest interactive influences of temperature, corticosterone, and condition as mediators of maternal effects.

Chamber volume development, metabolic rates, and selective extinction in cephalopods

Reconstructing the physiology of extinct organisms is key to understanding mechanisms of selective extinction during biotic crises. Soft tissues of extinct organisms are rarely preserved and, therefore, a proxy for physiological aspects is needed. Here, we examine whether cephalopod conchs yield information about their physiology by assessing how the formation of chambers respond to external stimuli such as environmental changes. We measured chamber volume through ontogeny to detect differences in the pattern of chamber volume development in nautilids, coleoids, and ammonoids. Results reveal that the differences between ontogenetic trajectories of these cephalopods involve the presence or absence of abrupt decreases of chamber volume. Accepting the link between metabolic rate and growth, we assume that this difference is rooted in metabolic rates that differ between cephalopod clades. High metabolic rates combined with small hatching size in ammonoids as opposed to lower metabolic rates and much larger hatchlings in most nautilids may explain the selective extinction of ammonoids as a consequence of low food availability at the end of the Cretaceous.

Rapid larval growth is costly for post-metamorphic thermal performance in a Great Barrier Reef fish

Most marine fish species disperse during a planktonic larval stage where individuals exhibit variation in pelagic duration, growth rate and settlement size. Extreme predation risk is predicted to select for rapid growth rates and decreased pelagic duration as a strategy for increasing survival to settlement. How larval traits affect post-metamorphic performance, however, has been a contentious topic over the past 50 yrs. Some studies suggest that larval traits have carry-over effects to later life stages, where larval traits can be positively or negatively correlated with post-metamorphic performance. For example, individuals with rapid larval growth rates may settle at larger sizes and have faster post-metamorphic locomotion than slow-growing individuals. Alternatively, trade-offs between life stages might exist, where rapid larval growth rate may be negatively correlated with post-metamorphic locomotion, potentially due to energetic resource allocation trade-offs. In addition, other studies suggest that larval traits are decoupled from later life stages to allow for a transition in morphology and habitat. We tested how Bathygobius cocosensis hatch size, larval growth rates, settlement size and pelagic duration correlated with post-metamorphic thermal performance of burst swimming speed, routine metabolic rate and critical thermal maximum. We found that larval growth rate was negatively correlated with juvenile routine metabolic rate and burst swimming speed across a range of test temperatures. That is, fast-growing larvae had slower burst swimming speeds and lower routine metabolic rates across temperature as juveniles compared to slower-growing larvae. We also found that hatch size and pelagic larval duration were not correlated with post-metamorphic performance. Thus, we provide evidence both for larval traits having carry-over effects on later life stages and also for larval traits being decoupled with thermal performance post-metamorphosis. This is the first study to show that rapid larval growth rate is costly for post-metamorphic thermal performance.

Threshold temperature constraints on reproduction of the banded killifish (Fundulus diaphanus)

Banded killifish (Fundulus diaphanus) are a small, freshwater fish that have a wide distribution in eastern North America and are considered a species-at-risk on the island of Newfoundland. We posit that because Newfoundland’s summer climate is much cooler than other locations at similar latitudes, there may be different constraints on banded killifish reproduction. We measured embryonic development under four temperatures (10, 16, 22, and 28 °C) and two conductivities (0.6 and 1.2 mS/cm). Warmer temperatures led to more developed embryos prior to death in embryos that ultimately did not hatch, higher hatch success, faster hatch time, and fewer thermal units to hatch. Conductivity and temperature interacted to affect hatch size. Therefore, banded killifish are likely challenged by the low temperature and conductivity conditions in Newfoundland which may result in reproductive constraints, and perhaps complete cohort failures in relatively cool summers.

Pre-hatching development in the intertidal zone negatively affects juvenile survival and physiology in the muricid gastropod Acanthina monodon

Encapsulated development in the intertidal environment can potentially expose developing embryos to environmental stresses, particularly during low tides. Such stresses can affect juvenile performance after hatching. Capsules-containing advanced pre-hatching stages of the snail Acanthina monodon were collected during July–August 2017 from rocks in the intertidal and subtidal environments along the coast of Valdivia, Chile (Calfuco beach, 39°79′27″S; 73°39′27″W) and brought to the laboratory, where hatching of the juveniles took place. The number of embryos per capsule in relationship to capsule size was determined for capsules from the two environments, as were the juvenile hatching size and the number of juveniles hatching from each capsule. Survival and respiratory performance were also monitored for juveniles from the two locations. Neither embryonic packaging nor the number of juveniles hatched per capsule, nor the hatching size of the juveniles evidenced any differences for capsules that were collected in the two different environments. In general, juvenile survival was low (< 10% at 4 week post-hatching) regardless of capsule origin. However, survival and standardized rates of oxygen consumption were substantially higher for juveniles from subtidal capsules. This suggests that environmental stressors had a detrimental effect on embryos from intertidal capsules.

Stressful conditions affect reproducing cuttlefish (Sepia officinalis), reducing egg output and quality

Abstract Stress has profound effects on animals, particularly if it occurs during reproduction or embryonic development. The cuttlefish Sepia officinalis is an economically and scientifically important species that is often cultured in captivity. The effects of stressors applied to reproducing females and developing embryos were investigated and compared by measuring the number and quality of eggs produced by females in a typical captive setting with females subjected to stress during egg-laying (confined space and repeated removal from the water) as well as comparing the hatching size and success of embryos subjected to naturally occurring (predator cues) and artificial (random bouts of bright LED light) stressors. Stressed females produced significantly fewer eggs and fewer of those eggs hatched. In addition, nearly a quarter of stressed mothers laid mostly white eggs lacking the dark pigment typical of this species. In contrast to maternal stress, stressors applied directly to embryos had no effect on hatching rate and neither maternal nor embryonic stress was associated with differences in hatching size. Our results suggest that reducing stress during egg-laying can increase aquacultural egg yields in S. officinalis and that the presence of pigment-less (white) eggs is a sign of maternal stress during egg-laying.

You Better Repeat It: Complex CO2 × Temperature Effects in Atlantic Silverside Offspring Revealed by Serial Experimentation

Concurrent ocean warming and acidification demand experimental approaches that assess biological sensitivities to combined effects of these potential stressors. Here, we summarize five CO2 × temperature experiments on wild Atlantic silverside, Menidia menidia, offspring that were reared under factorial combinations of CO2 (nominal: 400, 2200, 4000, and 6000 µatm) and temperature (17, 20, 24, and 28 °C) to quantify the temperature-dependence of CO2 effects in early life growth and survival. Across experiments and temperature treatments, we found few significant CO2 effects on response traits. Survival effects were limited to a single experiment, where elevated CO2 exposure reduced embryo survival at 17 and 24 °C. Hatch length displayed CO2 × temperature interactions due largely to reduced hatch size at 24 °C in one experiment but increased length at 28 °C in another. We found no overall influence of CO2 on larval growth or survival to 9, 10, 15 and 13–22 days post-hatch, at 28, 24, 20, and 17 °C, respectively. Importantly, exposure to cooler (17 °C) and warmer (28 °C) than optimal rearing temperatures (24 °C) in this species did not appear to increase CO2 sensitivity. Repeated experimentation documented substantial inter- and intra-experiment variability, highlighting the need for experimental replication to more robustly constrain inherently variable responses. Taken together, these results demonstrate that the early life stages of this ecologically important forage fish appear largely tolerate to even extreme levels of CO2 across a broad thermal regime.

Larval traits show temporally consistent constraints, but are decoupled from postsettlement juvenile growth, in an intertidal fish

Complex life cycles may evolve to dissociate distinct developmental phases in an organism's lifetime. However, genetic or environmental factors may restrict trait independence across life stages, constraining ontogenetic trajectories. Quantifying covariance across life stages and their temporal variability is fundamental in understanding life-history phenotypes and potential distributions and consequences for selection. We studied developmental constraints in an intertidal fish (Bathygobius cocosensis: Gobiidae) with a discrete pelagic larval phase and benthic juvenile phase. We tested whether traits occurring earlier in life affected those expressed later, and whether larval traits were decoupled from postsettlement juvenile traits. Sampling distinct cohorts from three annual breeding seasons afforded tests of temporally variability in trait covariance. From otoliths (fish ear stones), we measured hatch size, larval duration, pelagic growth (larval traits) and early postsettlement growth (juvenile trait) in 124 juvenile B.cocoensis. We used path analyses to model trait relationships with respect to their chronological expression, comparing models among seasons. We also modelled the effect of season and hatch date on each individual trait to quantify their inherent variability. Our path analyses demonstrated a decoupling of larval traits on juvenile growth. Within the larval phase, longer larval durations resulted in greater pelagic growth, and larger size-at-settlement. There was also evidence that larger hatch size might reduce larval durations, but this effect was only marginally significant. Although pelagic and postsettlement growth were decoupled, pelagic growth had postsettlement consequences: individuals with high pelagic growth were among the largest fish at settlement, and remained among the largest early postsettlement. We observed no evidence that trait relationships varied among breeding seasons, but larval duration differed among breeding seasons, and was shorter for larvae hatching later within each season. Overall, we demonstrate mixed support for the expectation that traits in different life stages are independent. While postsettlement growth was decoupled from larval traits, pelagic development had consequences for the size of newly settled juveniles. Temporal consistency in trait covariances implies that genetic and/or environmental factors influencing them were stable over our three-year study. Our work highlights the importance of individual developmental experiences and temporal variability in understanding population distributions of life-history traits.

Characterization of igf1 and igf2 genes during maraena whitefish (Coregonus maraena) ontogeny and the effect of temperature on embryogenesis and igf expression

The insulin-like growth factors IGF-1 and IGF-2 play important roles in the growth, development, and metabolism of teleost fish. We isolated cDNA sequences of igf1, and igf2 genes from maraena whitefish. We quantified the mRNA and protein expressions of IGFs in different tissues of marketable juvenile maraena whitefish. Moreover, we analyzed the gene expression profiles during maraena whitefish development from unfertilized egg to fingerling and examined the effect of incubation temperature on igf1, and igf2 gene expression during embryonic and early larval development.Transcripts encoding IGF-1 or IGF-2 were detected in all tested tissues, with the greatest abundance in the liver. We measured higher igf2 than igf1 copy numbers in all tissues and at all developmental stages examined, even at advanced juvenile stages. Using the Western blot technique, we demonstrated that several isoforms of IGF-1 are expressed in the liver and gills but not in muscle tissue, indicating tissue-specific protein expression of IGF-1. We observed an accelerated embryonic development with increasing temperature, resulting in shortened hatching periods. Out of the three tested temperatures, we observed the highest hatching rate, larval hatching size, and larval growth at 6 °C. At 9 °C, hatching rate, larval hatching size and larval growth were reduced compared to the values we observed at 4 °C and 6 °C, since incubation temperature might have exceeded the optimum. To our knowledge, our data show for the first time that both igf1 and igf2 expression were upregulated due to elevated incubation temperature within embryonic development of fish. Further, we found significantly higher igf expression for the best-developing larvae (6 °C group) at specific life stages of maraena whitefish.

Negative Allometry for Egg Size in Ladybeetles (Coleoptera:Coccinellidae):Trade-Off between Egg Hatch Time and Size

Negative Allometry for Egg Size in Ladybeetles (Coleoptera:Coccinellidae):Trade-Off between Egg Hatch Time and Size

Shell ornament, systematic position and hatching size of Epicymatoceras vaelsense (Nautilida): New insights based on specimens in mould preservation from the Upper Cretaceous of Poland

The fossil record of Nautilida in carbonate facies is skewed towards moulds (steinkerns) in various states of preservation, which complicates assessment of the original shell ornament of many taxa. As a remarkable exception, moulds of Epicymatoceras vaelsense from upper Campanian and lower Maastrichtian (Upper Cretaceous) siliceous limestones (opoka) in Poland retain details of the original shell ornament, allowing conclusions on the original structure of the shell wall, systematic position and hatching size of this nautilid to be drawn. Both external and internal moulds are present in the material studied, which are referred to as taphomorph 1 and 2, respectively. Based on morphology and inferred taphonomy, it is proposed that the external ribbing of E. vaelsense was originally composed of overlapping, tile-shaped lamellae of the outer prismatic layer, a character recently suggested to be a synapomorphy for the cymatoceratid clade. The diameter of the embryonic conch of E. vaelsense is estimated to have been around 30 mm, which is near the maximum range of hatching size recorded for Cretaceous and younger nautilids. On the basis of the inferred shell structure of E. vaelsense, it is speculated that living individuals of this nautilid were covered by a dense periostracal cover similar to that of Recent Allonautilus scrobiculatus. This study demonstrates that nautilid moulds may provide a better source of palaeontological data than conventionally accepted.

The potential effects of pre-settlement processes on post-settlement growth and survival of juvenile northern rock sole (Lepidopsetta polyxystra) in Gulf of Alaska nursery habitats

Early life history traits in marine fish such as growth, size, and timing of life history transitions often vary in response to environmental conditions. Identifying the potential effects of trait variation across life history stages is critical to understanding growth, recruitment, and survival. Juvenile northern rock sole (Lepidopsetta polyxystra) were collected (2005, 2007, 2009–2011) from two coastal nurseries in the Gulf of Alaska during the early post-settlement period (July–August) to examine variation in early life history traits in relation to water temperature and juvenile densities in nurseries as well as to evaluate the potential for carry-over effects. Size-at-hatch, larval growth, metamorphosis size and timing, and post-metamorphic and recent growth of juveniles were quantified using otolith structural analysis and compared across years and sites. Additionally, traits of fish caught in July and August were compared for evidence of selective mortality. Post-metamorphic and recent growth were related to temperatures in nurseries as well as temperatures during the larval period, indicating a direct influence of concurrent nursery temperatures and a potential indirect effect of thermal conditions experienced by larvae. Correlations between metamorphic traits and fish size at capture demonstrated that interannual variation in size persisted across life history stages regardless of post-settlement growth patterns. No evidence of density-dependent growth or growth-selective mortality were detected during the early post-settlement period; however, differences in hatch size and metamorphosis timing between fish collected in July and August indicate a selective loss of individuals although the pattern varied across years. Overall, variation in size acquired early in life and temperature effects on the phenology of metamorphosis may influence the direction of selection and survival of northern rock sole.

Relationship of egg and hatchling size to incubation temperature in the multiple-spawning fish Gnathopogon caerulescens (Honmoroko)

Egg size affects larval size, growth rate, survival and fecundity with maternal fitness being maximized by a trade-off between egg size and fecundity. Production of a small number of large eggs maximizes female fitness under poor food conditions, as does a large number of small eggs under rich food conditions. Gnathopogon caerulescens (Honmoroko) spawns over a wide range of water temperature from spring to summer. Thus, we determined whether or not egg size varied with water temperature and how egg size influenced hatchling size at different water temperature. Changes in egg size strongly correlated with seasonal changes in water temperature around the lake, regardless of time and area. An experiment using eggs from the lake indicated that hatchling size has a significant positive relationship with egg size in water temperatures of 24 °C. On the other hand, a lower incubation temperature, similar to that likely to be encountered at the beginning of the spawning season, resulted in a smaller hatchling size, eggs requiring a longer time to hatch. At the beginning of the spawning season, therefore, egg size may have a lesser impact on hatching size in the natural environment of Honmoroko because of the relatively lower temperatures. Although fish larvae below a certain threshold of effective body size are generally not expected to have a high early survival rate due to, for example, a lower competitive ability or a high susceptibility to predation, seasonal egg size variation in Honmoroko may be adaptive so as to enhance the likehood of early survival by establishing an effective body size under changing water temperature conditions.

Water salinity effects on embryogenesis of the lesser sandeel, Ammodytes tobianus (Linnaeus, 1758)

Abstract Effects of water salinity (3.0–9.0 PSU) on the duration and outcome of embryogenesis in the lesser sandeel (Ammodytes tobianus (L.) as well as on survival, size, and malformation rate of the newly hatched larvae were followed, based on observations involving equipment consisting of a microscope and still and digital cameras. The images obtained and measurements of egg and larval dimensions were analyzed using the NIS elements Br. computer software package. The lowest salinity tested (3.0 PSU), similar to that in the inshore Baltic Sea waters native for the species studied, produced a lower fertilization rate and resulted in extended embryogenesis, reduced embryo survival, changes in the hatch size, and increased larval malformation rate. The high-end salinity (7.5–9.0 PSU), higher than that prevailing in the species’s spawning grounds in the Baltic Sea, resulted — similarly to the low-end salinity — in disturbed development and growth of the embryos.