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Bioenergetics of the planktonic copepod Acartia tonsa: relation between feeding, egg production and respiration, and composition of specific dynamic action
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... Under sufficient food supply, water temperature assumes a pivotal role in governing the seasonal dynamics of copepod populations [28], exerting influence over individual growth time, egg production, and survival rate [29][30][31]. Concurrently, food availability stands as another influencing factors shaping the life history of zooplankton [32], correlating with growth time, egg production, and body size [30,[33][34][35]. Notably, in the specific case of E. japonicus, experiments by Liu et al. [24] underscore that the impact of insufficient food becomes more pronounced at elevated temperatures. ...
The seasonal fluctuations of the copepod Eodiaptomus japonicus, which dominates the zooplankton community of Lake Biwa, have been disrupted several times over the past 45 years. The aim of this study was to clarify the primary environmental factor that caused the disrupted seasonal cycle in population density of E. japonicus. Here, we tested the hypothesis that the disruption in their seasonal cycle was due to the impacts of water temperature, food conditions, and predator pressure, using an individual-based model (IBM). Based on the experimental data from the literature, we described the growth and reproduction of E. japonicus using temperature- and food-dependent functions. Previously, the developmental time of this species was expressed using Bělehrádek’s equation. In this study, we applied the Kontodimas equation, which successfully reproduced the effects of food scarcity at higher temperatures. Additionally, the influence of predators was incorporated into the survival rate of adult individuals. The long-term data set of Lake Biwa was input into the developed model to simulate the population fluctuations during the disruption period (1975–1979) and stable period (1995–1999) of their seasonal cycle. The combination of environmental data to be input was (1) water temperature, food availability, and predators; (2) water temperature and food availability; and (3) water temperature and predators. Disruptions in the seasonal cycle of the population were only observed in scenario (1) during the disruption period simulation, suggesting that the disrupted seasonal cycle of this species in Lake Biwa may have been caused by the effects of both food condition and predators. The results of simulation scenarios (2) and (3) indicated that predators have a stronger impact on the population than food availability. This time, we used common and simple indicators to describe food conditions and predators, but the model can be improved to be more complex and accurate as more data become available. Such models are important tools for understanding the relationship between environmental factors and the dynamics of diaptomid copepod populations.
... Do vậy, các nghiên cứu trước đã cho biết việc đáp ứng đủ và cân đối các thành phần dinh dưỡng trong thức ăn cho Copepoda là cơ sở thiết lập các mức thí nghiệm [27,28,31,40]. Số lượng trứng của Copepoda cái tăng lên khi tăng lượng thức ăn đến mức tối ưu [6,22].Trong nghiên cứu này, các mức thí nghiệm kế thừa kết quả nghiên cứu của Doan et al. (2018) [8]. Nghiên cứu này đã cho A. royi ăn vi tảo I. galbana với 3 mức mật độ. ...
Nghiên cứu được thực hiện để đánh giá ảnh hưởng của mật độ vi tảo Isochrysis galbana đến sức sinh sản và tỷ lệ nở thành công của loài Copepoda Apocyclops royi. Thí nghiệm được tiến hành với 3 nghiệm thức mật độ vi tảo làm thức ăn cho Copepoda được quy về đơn vị μg C là: 160; 800 và 1600μg C/L. Mỗi nghiệm thức được lặp lại 10 lần. Copepoda A. royi được cho ăn vi tảo theo 3 nghiệm thức trên từ giai đoạn Nauplius 3 đến khi trưởng thành. Khi A. royi trưởng thành, sức sinh sản của chúng được xác định dựa trên số trứng trung bình của 30 con Copepoda cái thu được ở mỗi nghiệm thức. Tỷ lệ nở thành công được xác định dựa trên tỷ lệ nở của trứng của 10 cá thể cái với mỗi nghiệm thức. Kết quả cho thấy sức sinh sản của A. royi cao nhất ở nghiệm thức 1600μg C/L và thấp nhất ở 160μg C/L. Tỷ lệ nở thành công cao nhất ở nghiệm thức 800μg C/L, tiếp đến là 1600μg C/L và thấp nhất ở 160μg C/L (P < 0,05). Nghiên cứu này cung cấp thông tin về chế độ cho ăn ảnh hưởng đến sức sinh sản và tỷ lệ nở thành công của A. royi, góp phần phát triển kỹ thuật nuôi sinh khối giáp xác chân chèo phục vụ cho ương nuôi giống hải sản.
... During our respirometry experiments, incubations did not contain any food, and therefore, copepods may have fasted during the 6-8 h experiments. Studies on the gut content of copepods indicate that small species may respond rapidly (within hours) to changing food conditions (e.g., Kiørboe et al. 1985) and, so, affecting their MRs. The larger-sized C. patagoniensis may perhaps not respond so rapidly to starving conditions compared to the smaller A. tonsa and P. cf. indicus, providing more stored energy to satisfy metabolic demands. ...
Ongoing ocean deoxygenation is threatening marine organisms globally. In eastern boundary upwelling systems, planktonic copepods dominate the epipelagic zooplankton, being crucial in the marine food web. Yet, they must cope with severe hypoxia caused by shoaling of the oxygen minimum zone. Based on laboratory experiments during 2021, we found differential responses in the metabolic rate (MR) and critical oxygen partial pressure of three abundant copepods. Calanoides patagoniensis doubled its MR during the upwelling season, so better exploiting the spring phytoplankton bloom for feeding and reproduction while maintaining their critical oxygen partial pressure unchanged between seasons. Contrastingly, Paracalanus cf. indicus and Acartia tonsa, maintained their MRs throughout seasons, but significantly increased their critical oxygen partial pressure during the upwelling period, becoming less tolerant to hypoxia. Field observations showed that oxygen levels equal to or lower than the critical oxygen partial pressure is a common condition (70% of occurrence) that copepods encounter during the year in the upper 50 m layer. These findings suggest a species‐dependent trade‐off between the MR and the critical oxygen partial pressure, where some species can maintain the latter despite fluctuations in their MR (improved hypoxia tolerance) or maintain their MR at the expenses of a larger critical oxygen partial pressure (improved energy expenditures). These adaptive responses, under oxygen levels equal to or lower than the critical oxygen partial pressure, suggest that exacerbated hypoxia, driven by ocean deoxygenation and increased upwelling, will alter copepod distribution and cause higher copepod mortality, with potentially drastic consequences for marine food webs.
... In this study, therefore, the crowding-mediated reduction of metabolic rate in D. magna may be related to the reduction of ingestion rate due to physical interference, even under conditions of excess food conditions. This effect could be explained by a lowering of specific dynamic action (SDA), which refers to the additional energy expenditure in an animal for processing ingested food, digesting, distributing, and absorbing nutrients, and synthesis of new tissues (Ikeda 1977, Kiørboe et al. 1985, Urabe and Watanabe 1990. Further investigation into assimilation efficiency and SDA under crowded conditions could provide insights into the metabolic adjustments of zooplankton in response to high population densities. ...
... At the end of the experiments, the spawned eggs were counted and egg size was measured on a batch of eggs. Weight-specifi c egg production (SEP) was calculated from individual female carbon content according to Hirche & Mumm (1992) assuming a body carbon:dry weight ratio of 0.6 (Eilertsen et al., 1989), and an egg carbon content of 0.14 pg C µm -3 (Kiørboe et al., 1985). The egg production and SEP of egg-carrying Oithona spp. was calculated according to the equations in Nielsen et al. (2002). ...
An annual carbon budget of the pelagic food web is constructed for a 36 m deep station in Young Sound. Data were collected during a 2-week mid-summer sea-ice covered period in 1999, during the open-water period of 1996, 2003, 2004, 2005 and during winters of 1997 and 2003. The measurements revealed that during sea-ice cover the water column of outer Young Sound was strongly heterotrophic and sustained by organic material advected into the fjord from the open sea. The pelagic community thus originated from the marginal ice zone at the entrance to the fjord. No succession was observed in the plankton community during this period, and the grazing pressure of the dominating zooplankton groups (ciliates, heterotrophic dinoflagellates, meroplankton and copepods) was 10 times higher than primary production, while the bacterial carbon demand was three times higher than primary production. During the open-water period, the grazing community was completely dominated by copepods, which were capable of grazing down the entire primary production. This contrasts with several other investigated Arctic marine pelagic ecosystems further south, where the protozooplankton community is quantitatively more important than copepods. In Young Sound, both zooplankton groups are present simultaneously, and copepods thus act both as competitors for food and as predators in relation to the protozooplankton. On an annual basis, the carbon budget was unbalanced; the total carbon need of the grazers equaled primary production, leaving no room for the estimated bacterial carbon demand, which was of the same size as the carbon demand of the grazers. Thus, Young Sound is a net heterotrophic system relying on import of organic material from the open sea or possibly from land.
... Consequently, respiration in this experiment included the need to cover energy expenditure for food processing, the specific dynamic action (SDA; Secor 2009). SDA for N. integer is not reported in the literature, but was estimated to be 18% of the assimilated food for another mysid of the Baltic Sea, Mysis mixta (Rudstam 1989) based on literature data of other plankton crustaceans (Kiørboe et al. 1985;Lampert 1986). However, SDA might differ among mysid species and ingested prey categories. ...
Animals face strong environmental variability even on short time scales particularly in shallow coastal habitats, forcing them to permanently adjust their metabolism. Respiration rates of aquatic ectotherms are directly influenced by water temperature, whereas ingestion rates might additionally be influenced by behavior. We aim to understand how respiration and ingestion rates of an aquatic invertebrate respond to changing temperature during a diurnal thermal fluctuation cycle and how both processes are related. We studied the benthopelagic mysid Neomysis integer as an important food web component of coastal ecosystems. Mysids were collected at the southern Baltic Sea coast and exposed in the laboratory to either constant temperature of 15°C or daily temperature fluctuation of 15 ± 5°C. Short-term (1–2 h) respiration and ingestion rates were measured at four equidistant time points within 24 h and did not differ among time points at constant temperature, but differed among time points in the fluctuating treatment. Respiration was highest at the thermal maximum and lowest at the thermal minimum. Ingestion rates showed the opposite pattern under fluctuation, likely due to differences in underlying thermal performance curves. When temperature transited the average, the direction of temperature change influenced the animals' response in respiration and ingestion rates differently. Our results suggest that respiration is not only instantaneously affected by temperature, but also influenced by the previously experienced direction of thermal change. Our experiment, using an important non-model organism, delivered new insights on the relationship between the crucial organismal processes ingestion and respiration under thermal variability.
Maternal effect plays important role in adaptive evolution and population dynamics. Methylparaben (Mep) is a common organic pollutant exerting diverse impacts on aquatic organisms. However, the impact of maternal Mep exposure on offspring remains poorly understood. This study was designed to explore whether maternal Mep exposure can affect the offspring’s population performance, either by amictic mothers in parthenogenesis phase, or by mictic mothers in sexual reproduction phase of the rotifer Brachionus calyciflorus. Here, we exposed either amictic or mictic mothers from one clonal laboratory population to 20 mg/L Mep (T environment) until the offspring or resting eggs were collected. A parallel control group without Mep (C environment) was also set. Thereafter, offspring from amictic mothers or stem female from resting eggs of mictic mothers were treated similarly in T or C environment. Population growth, life history traits and antioxidant indices of the offspring were examined. The results demonstrated that maternal Mep exposure inhibited population performance of offspring in both life history phases, while the negative effects were markedly buffered in sexual reproduction phase. This study clarifies toxicity of Mep on rotifers and highlights the different response patterns of maternal Mep exposure in different life history phase.
Zooplankton undergo a diel vertical migration (DVM) which exposes them to gradients of light, temperature, oxygen, and food availability on a predictable daily schedule. Disentangling the co‐varying and potentially synergistic interactions on metabolic rates has proven difficult, despite the importance of this migration for the delivery of metabolic waste products to the distinctly different daytime (deep) and nighttime (surface) habitats. This study examines the transcriptomic and proteomic profiles of the circumglobal migratory copepod, Pleuromamma xiphias , over the diel cycle. The transcriptome showed that 96% of differentially expressed genes were upregulated during the middle of the day – the period often considered to be of lowest zooplankton activity. The changes in protein abundance were more spread out over time, peaking (42% of comparisons) in the early evening. Between 9:00 and 15:00, both the transcriptome and proteome datasets showed increased expression related to chitin synthesis and degradation. Additionally, at 09:00 and 22:00, there were increases in myosin and vitellogenin proteins, potentially linked to the stress of migration and/or reproductive investment. Based on protein abundances detected, there is an inferred switch in broad metabolic processes, shifting from electron transport system in the day to glycolysis and glycogen mobilization in the afternoon/evening. These observations provide evidence of the diel impact of DVM on transcriptomic and proteomic pathways that likely influence metabolic processes and subsequent excretion products, and clarify how this behaviour results in the direct rapid transport of waste metabolites from the surface to the deep ocean.
Ingestion rate, gut clearance rate and gut content were measured in the laboratory in adult females of the planktonic copepod Centropages hamatus fed the centric diatom Ditylum brightwelli. Ingestion rate increased with algal concentration approaching a maximum rate equal to 85 % body C · d−1 at 15 °C. Within the temperature interval studied (1–15 °C), maximum ingestion rate increased with temperature with a Q10 of 3.9. Gut clearance rate was estimated by following the exponential decrease in the gut content of plant pigments (measured fluoremetrically) with time after feeding, and showed approximately the same temperature dependence (Q10 = 3.3) as ingestion rate. The relationship between gut content and algal concentration was described by an equation similar to that relating ingestion rate to algal concentration. Gut content multiplied with gut clearance rate, which can be considered an estimate of ingestion rate, yielded values similar to ingestion rates actually measured. This implies that in situ algal ingestion rates may be estimated from measurements of the content of plant pigments in the guts of freshly caught copepods.
Historically, scientific consideration of the energetics of intestinal Na+-dependent transport systems has evolved through five distinct conceptual stages (see Table 1). The earliest stage involved recognition of a mechanistic role for Na+ (Riklis and Quastel 1958, Crane et al. 1961), Characterization of its kinetic effects (Crane et al. 1965, Curran et al. 1967, Goldner et al. 1969) and proposal of transport models which considered flow of Na+ down a gradient of chemical potential as the means of energy input to the transport system (for a review see Schultz and Curran 1970). These models typically involved membrane components with binding sites for both Na+ and an organic solute.
The population dynamics and energetics of two populations of Diaptomus gracilis have been studied in two Thames Valley reservoirs. The seasonal changes in the standing crop biomass varied from a low of 0.3 Cal/m^2 to a high of 7 Cal/m^2. Although the population overwintered primarily as adults, reproduction was continuous throughout the year. From the mortality rate the production has been estimated to be 52 and 48 Cal/m^2 for the Queen Elizabeth II and King George VI reservoirs, respectively. Feeding and respiratory rates of D. gracilis were measured both in the laboratory and in the field simultaneously with the population dynamics in the reservoir. The feeding rate and the rate of assimilation varied with the species of phytoplankton used as food. Filtering rates varied from 0.1 ml copepod^-^1 day^-^1 on bacteria to a high of 2.54 on Diplosphaeria, the latter also having an assimilation efficiency of 78% by D. gracilis. Respiratory rates varied with the season. When the metabolic rate was plotted against body weight, evidence of three regression lines during the year was found, the lowest slope in the winter and the highest in the late spring and early summer. When the regression of oxygen consumption on weight and temperature was calculated, it was necessary to calculate two lines, one for the fall-winter period and one for the spring-summer.
Adult female and stage V Calanus pacificus were fed ¹⁴ C‐labeled phytoplankton in the laboratory in the form of monospecific cultures and natural populations. A carbon budget was constructed by following the ¹⁴ C activity and the specific activity, over 48 h, in the phytoplankton, copepod, dissolved organic, dissolved inorganic, and fecal carbon compartments.
The average incorporation of carbon into the copepod’s body was 45% of the phytoplankton carbon available. Of the phytoplankton carbon, 27% appeared as dissolved organic carbon, 24% as dissolved inorganic carbon, and 3–4% in the form of fecal pellets. All of the tracer was recovered at the end of the experiments. The specific activity of the phytoplankton compartment was constant throughout each experiment. The other compartments had initial specific activities of zero, or close to zero, and increased throughout the experiment. In most experiments, the copepod specific activity equalled that of the phytoplankton at the end of 48 h, while the dissolved organic carbon, dissolved inorganic carbon, and fecal specific activities remained well below that of the phytoplankton.
A technique, based on quantitative conversion of chlorophyll a to pheophorbide during digestion, is described for determination of assimilation efficiencies of particle-feeding zooplankton. Calanus pacificus had assimilation efficiencies ranging from 68.5 to 85.4% for carbon and 73.9 to 92.5% for nitrogen. Assimilation efficiencies for copepods first acclimated to different food concentrations of Thalassiosira weissflogii and then fed at the same food level varied systematically, with animals acclimated to low food having higher efficiencies than animals acclimated to high food.
ABSTRACT When,adult,females,of Calanus,pacificus,are,fed,on,monospecific,cultures,of,centric diatoms which grow as single cells, a predictive relationship is found between feeding behavior,of the,copepods,and,size,and,concentration,of,food,particles.,Ingestion,rate of copepods increases linearly with cell concentration up to a maximal,rate. This maximal ingestion rate, expressed as carbon, is the same for copepods feeding on diatoms ranging in diameter from 11-87 P. As the size of food particles increases, the carbon,concentration,at,which,this,ingestion,rate,is achieved,decreases.,Thus,females ofpacificus can,obtain,their maximal,daily,ration at relatively,low,carbon,concentrations of large cells, INTRODUCTIOS In oceanic food webs, Calanoid copepods