Energy Allocation Patterns Research Articles

Interpopulation variation in prebreeding energy reserves of plateau brown frog (Rana kukunoris)

The energy storage plays a prominent part in the life histories of many animals inhabiting cold harsh environment, thus anuran amphibians rely on larger residual energy stores from post-hibernation to cope with unfavourable weather conditions before breeding. As the habitat conditions often change in different locations, selective pressure for energy storage could also vary. However, we still have limited knowledge on whether anurans living under different environmental backgrounds would adopt suitable strategies to cope with energy demands during reproduction. Here, we examined patterns of energy storage in spring (after hibernation and before reproduction) in seven plateau brown frog (Rana kukunoris) populations with different climatic conditions in the eastern Tibetan Plateau. After removing the effects of age and body size, liver weights of both sexes and fat body weights in males were negatively correlated with temperature, suggesting that these reserves were critical for this anuran to survive through harsh and extended dormancy period under uncertain environmental conditions. Additionally, reproductive investment in both sexes could partly explain the increase in post-hibernation energy stores with decreasing temperature. Males had relatively heavier liver and fat body weights than females, indicating that males store more energy reserves for breeding activity compared with females. Therefore, we suggest that both the variation of environmental conditions and sexual differentiation of reproductive roles play a prominent role in shaping the energy allocation and reserve patterns in the dormancy and breeding of amphibian species.

Research on Risk Evaluation of Hydropower Engineering EPC Project Based on Improved Fuzzy Evidence Reasoning Model

As clean renewable energy with strong advantages, hydropower plays an extremely important role in promoting green development and energy allocation patterns. Hydropower project construction is characterized by long duration, large scale, high cost, many participants, and complex construction conditions, and is closely related to the economy, society, and ecological environment, and its construction management mode and construction risk management have become the focus of extensive attention from all walks of life. In this paper, the risk evaluation index system of hydropower engineering EPC project is constructed, and the linear weighted combination method is introduced to determine the comprehensive weights based on the calculation of weights by sequential relationship method and entropy weight method, and the improved fuzzy normal distribution is introduced as the subordinate function distribution of fuzzy evaluation level based on DS evidence theory and fuzzy theory. The risk evaluation model of a hydropower engineering EPC project is also established. Meanwhile, the model was analyzed with hydropower project examples to verify the accuracy and practicality of the model, which can guide hydropower project stakeholders to manage hydropower project risks comprehensively, collaboratively, and efficiently, and provide decision support for hydropower project construction risk management.

Do changes in body mass alter white blood cell profiles and immune function in Australian cane toads (Rhinella marina)?

Variation in food resources can result in dramatic fluctuations in the body condition of animals dependent on those resources. Decreases in body mass can disrupt patterns of energy allocation and impose stress, thereby altering immune function. In this study, we investigated links between changes in body mass of captive cane toads (Rhinella marina), their circulating white blood cell populations, and their performance in immune assays. Captive toads that lost weight over a three-month period had increased levels of monocytes and heterophils and reduced levels of eosinophils. Basophil and lymphocyte levels were unrelated to changes in mass. Because individuals that lost mass had higher heterophil levels but stable lymphocyte levels, the ratio of these cell types was also higher, partially consistent with a stress response. Phagocytic ability of whole blood was higher in toads that lost mass, owing to increased circulating levels of phagocytic cells. Other measures of immune performance were unrelated to mass change. These results highlight the challenges faced by invasive species as they expand their range into novel environments which may impose substantial seasonal changes in food availability that were not present in the native range. Individuals facing energy restrictions may shift their immune function towards more economical and general avenues of combating pathogens. This article is part of the theme issue 'Amphibian immunity: stress, disease and ecoimmunology'.

Composite Multiple-Mode Orthogonal Frequency Division Multiplexing With Index Modulation

In this paper, we propose a composite multiple-mode orthogonal frequency division multiplexing with index modulation (C-MM-OFDM-IM) scheme to increase the spectral efficiency (SE) of OFDM-IM systems by extending the indexing to the energy and constellation domains. In C-MM-OFDM-IM, the information bits are mapped to not only the subcarrier activation patterns (SAPs) and modulation symbols, but also the energy allocation patterns (EAPs) and constellation activation patterns (CAPs). To cope with the practical situations, we propose a variant IM scheme named C-MM-OFDM-IM-II to build a new mapping rule between information bits and the increased CAPs, capable of further increasing the SE of C-MM-OFDM-IM. Upper-bounded bit error rate (BER) and lower-bounded achievable rate are both derived in closed-form to evaluate the performance of C-MM-OFDM-IM(-II). Moreover, we further propose two enhanced schemes, named generalized C-MM-OFDM-IM(-II) and C-MM-OFDM with in-phase/quadrature IM(-II), where the former jointly considers all SAPs, EAPs, CAPs and modulated symbols, while the latter expands the index implementation to the in-phase and quadrature constellation domains. Simulation results show that C-MM-OFDM-IM(-II) outperforms the conventional OFDM-IM related schemes, especially in the high signal-to-noise ratio (SNR) region, and verify the accuracy of the theoretical analysis for the upper-bounded BER and achievable rate.

Patterns of energy allocation during energetic scarcity; evolutionary insights from ultra-endurance events

Exercise physiologists and evolutionary biologists share a research interest in determining patterns of energy allocation during times of acute or chronic energetic scarcity. Within sport and exercise science, this information has important implications for athlete health and performance. For evolutionary biologists, this would shed new light on our adaptive capabilities as a phenotypically plastic species.In recent years, evolutionary biologists have begun recruiting athletes as study participants and using contemporary sports as a model for studying evolution. This approach, known as human athletic palaeobiology, has identified ultra-endurance events as a valuable experimental model to investigate patterns of energy allocation during conditions of elevated energy demand, which are generally accompanied by an energy deficit. This energetic stress provokes detectable functional trade-offs in energy allocation between physiological processes. Early results from this modelsuggest thatlimited resources are preferentially allocated to processes which could be considered to confer the greatest immediate survival advantage (including immune and cognitive function). This aligns with evolutionary perspectives regarding energetic trade-offs during periods of acute and chronic energetic scarcity.Here, we discuss energy allocation patterns during periods of energetic stress as an area of shared interest between exercise physiology and evolutionary biology. We propose that, by addressing the ultimate “why” questions, namely why certain traits were selected for during the human evolutionary journey, an evolutionary perspective can complement the exercise physiology literature and provide a deeper insight of the reasons underpinning the body's physiological response to conditions of energetic stress.

Oogonial proliferation and early oocyte dynamics during the reproductive cycle of two Clupeiform fish species.

Although oogonial proliferation continues in mature females in most teleosts, its dynamics and the transformation of oogonia to early meiotic oocytes during the reproductive cycle have received little attention. In the present study, early oogenesis was examined throughout the reproductive cycle in two Clupeiform fishes, the Mediterranean sardine, Sardina pilchardus, and the European anchovy, Engraulis encrasicolus. Observations using confocal laser scanning microscopy (CLSM) provided extensive information on markers of oogonial proliferation (mitotic divisions, oogonia nests) and meiotic prophase I divisions of oocyte nests (leptotene, zygotene, pachytene, diplotene) in ovaries of different reproductive phases. In sardine, oogonial proliferation persisted throughout the entire reproductive cycle, whereas in anchovy, it was more pronounced prior to (developing ovaries) and after (resting ovaries) the spawning period. Anchovy exhibited a higher rate of meiotic activity in developing ovaries, whereas sardine exhibited a higher rate in resting ovaries. The observed differences between the two species can potentially be attributed to different seasonal patterns of energy allocation to reproduction and the synchronization between feeding and the spawning season.

Energy utilization during ovarian development of the cichlid fish Oreochromis mossambicus (Peters) inhabiting a perennial lentic water body in Bangalore, India.

Mozambique tilapia Oreochromis mossambicus (Peters) is an invasive fish and a continuous breeder in inland waters of India. Present investigation highlights the distinct developmental stages of developing ovary and associated changes in the energy content. This investigation helps to understand the allocation of energy for development of eggs, prespawn and also oral brooding by the female. Although it is a continuous breeder, based on size of the ovary, number of eggs, their size and energy content, immature, early maturing, developing, prespawning and spawning stages are clearly noticed. Egg diameter during development of ovary varied between 0.31 mm (immature) and 2.21 mm (spawning). Energy content of ovary from immature to spawning stage ranged from 20.7515 kJ g-1 dry ovary to 31.1560 kJ g-1 dry ovary. Nearly 28.73% of energy content of ovary is expended for spawning. Similarly, yolk-sac fry utilized nearly 25.85% of energy of the fertilized egg for its development. Energy content of ovary of mouth-brooding female averaged 22.9528 kJ g-1 dry ovary, which is comparable to energy content of early maturing stage of ovary (24.5558 kJ g-1 dry ovary). A strong correlation between body weight and energy content of the developing ovary (P < 0.01), and between ovary weight and energy content of ovary (P < 0.01), was evident. During mouth-brooding, the fish continues to allocate energy to its developing ovary. Energy investment by the fish is the result of simultaneous processes associated with gonadal and somatic energy. As body size growth and gonadal development are interconnected, information on energy utilization by an iteroparous mouth-brooding fish could provide the pattern of energy allocation during ovarian developmental phase. Further details of energy utilization, as explained in this paper, could be used as one of the factors to predict the efficiency of fish production.

Metabolic Changes During Growth and Reproductive Phases in the Liver of Female Goldfish (Carassius auratus)

Hormones of the brain-pituitary-peripheral axis regulate metabolism, gonadal maturation, and growth in vertebrates. In fish, reproduction requires a significant energy investment to metabolically support the production of hundreds of eggs and billions of sperms in females and males, respectively. This study used an LC-MS-based metabolomics approach to investigate seasonally-related changes in metabolic profile and energy allocation patterns in female goldfish liver. We measured basal metabolic profile in female goldfish at three phases of the reproductive cycle, including 1) Maximum growth period in postovulatory regressed phase, 2) mid recrudescence in fish with developing follicles, and 3) late recrudescence when the ovary contains mature ovulatory follicles. We also investigated changes in the liver metabolism following acute treatments with GnRH and GnIH, known to be involved in controlling reproduction and growth in goldfish. Chemometrics combined with pathway-driven bioinformatics revealed significant changes in the basal and GnRH/GnIH-induced hepatic metabolic profile, indicating that metabolic energy allocation is regulated to support gonadal development and growth at different reproductive cycles. Overall, the findings support the hypothesis that hormonal control of reproduction involves accompanying metabolic changes to energetically support gonadotropic and somatotropic activities in goldfish and other oviparous vertebrates.

Environmental influence on life-history traits in male squid Uroteuthis edulis with alternative reproductive tactics

Squid are characterized by flexible life-history traits (LHTs) that change in response to changing oceanic parameters. Male alternative reproductive tactics (ARTs), characterized by large-sized ‘consorts’ versus small-sized ‘sneakers’, are commonly observed in loliginid species. This study reports on LHTs flexibility in male squids displaying ARTs. LHTs of consorts and sneakers in Uroteuthis edulis, including body size, age, growth rate and gonado-somatic energy allocation, were compared among seasonal and geographical groups from Japan and Taiwan. The ratio of consorts to sneakers was highest in the group spawning in the ‘Japan-warm’ season (June–November), followed by that of the ‘Japan-cold’ season (December–May), and lowest in Taiwan (spring and autumn). LHTs were compared among cohorts separated by hatching season and catch location (Jwarm, Jcold and Taiwan cohorts). Mean body size of consorts showed no difference among cohorts, although Taiwan consorts were relatively younger than Japan consorts. Mean size and age of sneakers decreased with increased water temperature at hatching. Growth rates of consorts and sneakers were slightly different among cohorts, in accordance with differences of statolith increment widths during their early life stage (50–150 days). Growth rates of both consorts and sneakers were highest in the Taiwan cohort, followed by the Jwarm cohort, with the Jcold cohort lowest. Sneakers invested more both in mantle and gonadal weights than consorts in all cohorts. Gonado-somatic energy allocation patterns of consorts and sneakers were consistent at different temperatures. LHTs of U. edulis consorts and sneakers were strongly influenced by temperature, with higher flexibility in sneakers than consorts.

Ecophysiological Effects of Waterborne Zinc on Ctenopharyngodon idellus

The juvenile Ctenopharyngodon idellus (19.68±0.17 g) were exposed to the solutions of zinc sulfate heptahydrate (ZnSO4.7H2O), to observe the toxic effects of waterborne Zn on this fish. The results showed that the median lethal concentration (LC50) over 96 h of waterborne Zn2+ was 5.00 mg/L. After 8 weeks of chronic exposure, the final weight and the specific weight growth rate of C. idellus decreased with the increasing Zn2+ concentration, and the differences were significant among the three groups (P &lt; 0.05). The content of ash in the high exposure group was significantly higher than those in the other two groups (P &lt; 0.05). The dry mass in the two exposure groups and the energy density in the low concentration group were significantly higher than those in the control group (P &lt; 0.05). The contents of Zn in the hepatopancreas, gill, intestine, muscle, and whole body in the high concentration group were significantly higher than those in the control group (P &lt; 0.05). The contents of Zn in hepatopancreas were significantly higher than those in other organs (P &lt; 0.05). There was no significant difference for the contents of Zn in the intestine and gill in the two Zn exposure groups, but those were significantly higher than those in other organs except hepatopancreas (P &lt; 0.05). The content of Zn in muscle was significantly lower than that in the other organs. It suggests that the pattern of energy allocation of the C. idellus is changed by the Zn exposure. Fat was preferentially used to provide extra energy for the detoxification under the Zn exposure, and the rates of the protein and energy deposited in the body were reduced. Therefore, the growth of the fish was depressed. The C. idellus mainly takes up Zn through the gill and distributes Zn to other tissues via blood circulation.

Latitudinal gradients in sexual dimorphism: Alternative hypotheses for variation in male traits.

Biological patterns across latitudinal gradients elucidate a number of striking natural clines from which numerous processes can be further explored. The trade‐off between reproduction and somatic maintenance and growth represents a suite of life‐history traits with variable energy allocation and potential latitudinal patterns. Specifically, male sexually dimorphic traits in female choice systems represent one such reproductive investment constrained by resource acquisition and subsequent allocation. Latitudinal variation in sexual dimorphism has been suggested although the relationship between dimorphic traits and latitude are conflicting. Here, we test alternative hypotheses regarding this pattern using two broadly distributed vertebrates exhibiting sexually dimorphic traits. We hypothesized that the exaggeration of dimorphic traits correlates with latitude, with males having exaggerated sexually dimorphic traits at either higher or lower latitudes. Results indicate that male sexually dimorphic traits are exaggerated at lower latitudes while relative gonopodium size in Poecilia latipinna was larger at higher latitudes. This pattern may be a result of lower latitude populations experiencing greater population densities and longer access to resources that could manifest in females more intensively selecting for higher quality males in lower latitudes. Experimental work should address this pattern and investigate mechanistic processes.

Prepeak energy evolution properties of sandstone subject to diametrical splitting with different loading rates

To understand the energy evolution properties during rock splitting under different loading rates, four groups of Brazilian test with a loading-unloading cycle corresponding to four orders of magnitude of controlled loading rate (10−1, 100, 101, 102 kN/min) were conducted on red sandstone using the MTS 322 testing system. The energy characteristics were interpreted by mathematically integrating the force-displacement responses of the tested rock specimens. It was found that at each loading rate, the input energy was a linear function as the elastic energy and dissipated energy, while these three types of energy nonlinearly grew with the unloading level. Importantly, the loading rate was found to exert an insignificant influence on the evolution of the linear energy properties (referring to the linear functions between the three types of energy); the energy storage coefficient (ESC) and/or energy dissipation coefficient (EDC) remained constant under various loading rates, exhibiting an approximate independency on loading rate. Based on this, a unified formula for describing the rate-independence of linear energy properties was presented in the tested loading rate range. It is also noted that rock mechanical parameters such as the peak force and peak displacement and the ESC and EDC are closely comparable versus the increasing loading rate, and hence the energy parameters are likely to be used to characterize the rock mechanical ones. Finally, the relevancy between energy allocation and rock failure patterns was discussed.

Soil fauna actively change their diet to survive stress

Animals are expected to choose foods that optimize their growth, reproduction and survival, but their dietary choice changes when suffering stress. Here, we provide the first report of nematode stress resulting from exposure to earthworm-produced cyclic peptides, and confirm that this stress changes the dietary choice of the model animal Caenorhabditis elegans and other soil-dwelling bacterial-feeding nematodes. When allowed free choice in a stress-free environment, nematodes prefer feeding on high-quality bacteria to support a higher reproduction and a shorter lifespan, supporting a reproduction-dominated energy allocation pattern. However, they feed less on preferred food (high-quality bacteria) and include more unpreferred food (low-quality bacteria) in the diet when stressed by the toxic cyclic peptides. Nematodes that eat more unpreferred bacteria appear to shift towards a survival-dominated energy allocation pattern. Specifically, limited resources obtained from low-quality bacteria are preferentially allocated to repair cyclic peptide-induced damage of their DNA and complete their lifespan, although at significantly reduced reproduction level. Our results demonstrate that nematodes can actively change their dietary strategy to maintain survival at the cost of reproduction when they experience acute stress. This stress-driven adjustment of dietary choice may be the key to understand feeding ecology and food web structure.

Seasonally related metabolic changes and energy allocation associated with growth and reproductive phases in the liver of male goldfish (Carassius auratus)

Reproduction and growth follow a seasonal pattern in many fish species involving changes in gonadal development, growth, and metabolism. Significant metabolic energy is needed during gametogenesis in both female and male to produce hundreds of eggs and billions of sperms. Seasonal variations are controlled by the hormones of brain-pituitary-peripheral axis and are accompanied by significant metabolic changes. There is evidence that GnRH and GnIH are among the key neurohormones that regulate the reciprocal control of growth and reproduction. The objective of this study was to investigate changes in metabolic profile and energy allocation patterns at different stages of reproduction, using goldfish as a model organism and LC-MS as analytical platform for metabolic analysis. Goldfish undergoes a clear seasonal cycle of growth and reproduction. In vivo experiments were conducted at three different time point of the annual cycle: regressed gonadal phase (peak growth phase), mid gametogenesis and late gametogenesis. Emphasis is placed on changes in liver metabolic pathways to energetically sustain the physiological processes related to growth and reproduction. Moreover, we tested the hypothesis that GnRH and GnIH may play a role in the regulation of metabolism by investigating acute effects of these peptides at different stages of reproductive cycle. SignificanceThe findings in this paper provide novel information on the seasonal changes in basal metabolism during different stages of reproductive cycle, and evidence for differential allocation of energy during reciprocal control of reproduction and growth in goldfish. Chemometrics combined with pathway-driven bioinformatics elucidated a shift in the metabolic profile, indicating distinct patterns of energy allocation in the reproductive and growth seasons. Furthermore, to our knowledge this is the first study to provide evidence for a possible regulatory role of GnRH and GnIH in liver metabolism and energy allocation patterns associated with growth and reproductive processes. Together our findings present a framework for better understanding of the hormonally induced changes in metabolism to energetically sustain growth and reproduction in fish and other oviparous species undergoing seasonal cycle.

Feet first: Adaptive growth in magellanic penguin chicks.

Growing animals should allocate their limited resources in ways that maximize survival. Seabird chicks must balance the growth of features and fat reserves needed to survive on land with those needed to successfully fledge and survive at sea. We used a large, 34‐year dataset to examine energy allocation in Magellanic penguin chicks. Based on the temporal trends in the selective pressures that chicks faced, we developed predictions relating to the timing of skeletal feature growth (Prediction 1), variation in skeletal feature size and shape (Prediction 2), and responses to periods of high energetic constraint (Prediction 3). We tested our predictions using descriptive statistics, generalized additive models, and principal component analysis. Nearly all of our predictions were supported. Chicks grew their feet first, then their flippers. They continued to grow their bill after fledging (Prediction 1). Variance in feature size increased in young chicks but declined before fledging; this variance was largely driven by overall size rather than by shape (Prediction 2). Chicks that died grew slower and varied more in feature size than those that fledged (Prediction 2). Skeletal features grew rapidly prior to thermoregulation and feet and flippers were 90% grown prior to juvenile feather growth; both thermoregulation and feather growth are energetically expensive (Prediction 3). To avoid starvation, chicks prioritized storing mass during the first 10 days after hatching; then, the body condition of chicks began to decline (Prediction 3). In contrast to our prediction of mass prioritization in young chicks, chicks that were relatively light for their age had high skeletal size to mass ratios. Chicks did not show evidence of reaching physiological growth limits (Prediction 3). By examining energy allocation patterns at fine temporal scales and in the context of detailed natural history data, we provide insight into the trade‐offs faced by growing animals.

Research progress in fecundity study of Coleoidea (Cephalopoda)

Cephalopods are characterized by fast growth, short generation replacement and high abundance. These species live in all oceans of the world with the exception of the Black Sea, not only playing an important role in the trophic webs of the marine ecosystem but also being one of the most important fishery resources in the world. It is important to well study the fecundity of cephalopods, which can improve our understandings of their life history, and more importantly can promote to realize their population dynamics and recruitment processes. Herein, the fecundity of Coleoidea (Cephalopoda) was summarized in details, including the definitions and their determination methodologies, the values of fecundity among species, and the changeable characteristics of fecundity in relation to species body size, egg diameter and living habitats. The potential fecundity was one of the most popular approaches to determine the reproductive value, and represented the theoretical value that one species could produce during its lifecycle. Other approaches such as actual realized fecundity, effective fecundity, and relative fecundity were also used to estimate the fecundity of cephalopod species. It showed that there was species-specific fecundity for Coleoida species. The maximum potential fecundity was reported for <italic>Dosidicus gigas</italic>, and the minimum was reported for <italic>Pareledone turqueti</italic>. The fecundity of Coleoidea was generally found a linear relation to adult body size, indicating a larger body size with a higher fecundity value. At the guild level, there was a significantly negative relationship between the fecundity and egg size for both Octopoda and Teuthoidea. In contrast, there was a slightly positive relationship between the fecundity and egg size for Sepioidea. Generally, species living at lower latitudes exhibited a relatively higher fecundity, and those living at higher latitudes had a relatively lower fecundity. Meanwhile, such fecundity characteristics were also detected at the species level. Water temperature and primary production appeared to be the most important environmental factors that influenced the latitudinal trend of fecundity among the species. It is worthy to note that Coleoida species is semelparous reproduction and the fecundity is associated with the pattern and amount of energy allocation to reproduction. The reproductive investment strategy would determine the actual fecundity of a species and subsequently the biomass of recruitment, and hence studies on the potential reproductive investment will be an important area for better understanding of the fecundity characteristics of cephalopods. Increasingly, the importance of cephalopods has been recognized not only in their ecological roles as trophic indicators but also in their high abundance supporting global fisheries. Therefore, it is necessary to deeply understand the fecundity characteristics of cephalopods, which will largely increase our knowledge about their ecological roles and also assist the sustainable exploitation and the policy-making of resource assessment and management.

A Novel Index of the Performance of Mytilus galloprovincialis to Improve Commercial Exploitation in Aquaculture

Estuarine environments are highly heterogeneous habitats where numerous organisms interact with each other. Aquaculture systems encompass such interactions, and the eventual yields depend on how the cultivated species respond to the environmental heterogeneity. Marine mussels are calcifying organisms that rely on calcium carbonate shell and byssus filaments secreted during their lifetime to protect soft vital tissues against aggressive, hydrodynamic environments and the actions of predators and competitors. Nevertheless, these protective structures can be energetically costly, depending on the environment, thus affecting the energy allocation patterns in the organism. Consequently, other important fitness parameters for the aquaculture industry, such as soft tissue condition and market value, may also be affected. Here, we present a spatial and temporal analysis of the protective and fitness responses in the mussel Mytilus galloprovincialis with the aim of obtaining a better understanding of the inter-location variability in survival and performance and the corresponding main environmental drivers. A novel, intuitive ecological index that measures the impact of both protective and fitness strategies was developed and is discussed in relation to cultivation timing. The data presented provides the basis for understanding the natural variability in energetic requirements for different vital tissues in bivalve mollusk that support survival and growth. We report the scientific basis for management actions aimed to shortening the cultivation cycle in the aquaculture sector. These actions are based on the combined use of the PROFIT index and other aquaculture practices (e.g. modifying density). PROFIT helps to identify when the quality of the product, understood as PROtection and FITness strategies, would be best suited for the market. Highlights: - PROFIT is a novel, simple eco-physiological index for use in the cultivation of marine mussels - Consideration of protective tissues and yield in cultivated marine bivalves is needed for better comprehension of energetic trade-offs during the life cycle - Innovations in aquaculture practices, here with the marine mussel Mytilus galloprovincialis as a case study, should consider new indicators like PROFIT (and others) for better management of the natural resource and for differentiating production areas or exploitation methods

Life histories of anadromous salmon males reveal a trade-off between primary and secondary sexual traits

Abstract The life-history trade-off between investment in somatic growth and gonadal tissue is caused by individual energy limitations and results in individuals that adopt specific tactics to achieve reproduction. Allocation in primary and secondary sexual traits in Atlantic salmon males was studied by assessing life history traits (smolt size, sea age, growth rate) based on back-calculation of scales, ejaculate energy content (sperm ATP content, mass and density) and the size of secondary sexual traits. We found that males investing less in secondary sexual traits produce ejaculates with a higher energy content. Differences were found in the investment into primary and secondary sexual traits between fish that spent one year in the sea before returning to their spawning grounds (grilse) and multi-sea-winter adults, suggesting that different energy allocation patterns in reproductive effort reflect alternative developmental pathways. These findings are consistent with the pattern where multi-sea-winter male ejaculate investment relies principally on the resource acquisition in the ocean, whereas grilse ejaculate investment relies chiefly on the resource allocation of available surplus energy, thus representing alternative male reproductive tactics.

Dynamic Energy Budget theory predicts smaller energy reserves in thyasirid bivalves that harbour symbionts

Dynamic Energy Budget (DEB) theory describes the ecophysiology of individuals and distinguishes between the biomass of an organism that functions as an energy reserve and as a structure. DEB theory offers a robust framework to infer and contrast energy allocation patterns, even in data-poor species. We used this approach to compare two thyasirid bivalves that have scarce data: Thyasira cf. gouldi and Parathyasira sp., which co-occur in a seasonal environment, show similar life history features, and are both particulate feeders. However, T. cf. gouldi hosts chemosymbiotic bacteria that are digested as an additional resource, and how this mixotrophy affects the energy budget of these chemosymbiotic thyasirids is unknown. We used allometric and life history data to parameterize a DEB model for each species and found that symbiotic T. cf. gouldi has a smaller fraction of its biomass as an energy reserve relative to Parathyasira. A smaller energy reserve, in turn, implies reduced energy assimilation and mobilization fluxes, lower somatic maintenance costs and growth rate, and larger energy allocation to maturity and reproduction in symbiotic T. cf. gouldi. For a thyasirid inhabiting an environment with seasonal forcing, these life history traits may represent an evolutionary strategy where the symbionts function as a partial energy reserve. Our results elucidate a potential role of the chemosymbiotic bacteria in the ecophysiology of a bivalve host, and highlight how the symbiotic association is likely to alter the energy budget of a mixotrophic thyasirid.

A full life cycle Dynamic Energy Budget (DEB) model for the green sea turtle (Chelonia mydas) fitted to data on embryonic development

The complex life history of sea turtles presents challenges for researchers. These slow-growing, long-lived reptiles occupy several habitats throughout their life cycle, including oceanic environments where they are difficult to study. Consequently, much research on sea turtle biology has focussed on the nesting environment. Yet, to effectively manage sea turtle populations, the documentation of processes such as growth, maturation and reproductive output is critical to understanding their population dynamics. Dynamic Energy Budget (DEB) theory provides a mechanistic framework for investigating such processes. Here we developed a full life cycle DEB model for a green turtle (Chelonia mydas) population from Western Australia, where the model was based primarily on data collected on the embryonic life stage. The model provided a good fit to empirical data, including the limited data on juvenile and adult growth, and suggested that it is practical to investigate full life cycle energetics based on embryonic data that are comparatively easy to collect. Maternal effects on embryonic development and patterns of energy allocation throughout the life cycle were inferred from the DEB model. This is the first DEB model developed for C. mydas, and its potential applications include demonstrating how maturation, maintenance and reproduction of wild individuals depend on food availability and temperature. Such applications are especially valuable for understanding future impacts of climate change, and how best to manage this iconic species that plays a key role in marine ecosystems across the globe.