Inferring functional traits in a deep-sea wood-boring bivalve using dynamic energy budget theory

For species in the deep sea, there is a knowledge gap related to their functional traits at all stages of their life cycles. Dynamic energy budget (DEB) theory has been proven to be an efficient framework for estimating functional traits throughout a life cycle using simulation modelling. An abj-DEB model, which compared with the standard DEB model includes an extra juvenile stage between the embryo and the usual juvenile stages, has been successfully implemented for the deep-sea Atlantic woodeater Xylonora atlantica. Most of the core and primary parameter values of the model were in the range of those found for shallow marine bivalve species; however, in comparison to shallow marine bivalves, X. atlantica required less energy conductance and energy to reach the puberty stage for the same range of body sizes, and its maximum reserve capacity was higher. Consequently, its size at first reproduction was small, and better survival under starvation conditions was expected. A series of functional traits were simulated according to different scenarios of food density and temperature. The results showed a weak cumulative number of oocytes, a low growth rate and a small maximum body size but an extended pelagic larval duration under deep-sea environmental conditions. Moreover, DEB modelling helped explain that some male X. atlantica individuals remain dwarfs while still reproducing by changing their energy allocation during their ontogenetic development in favour of reproduction. The estimation of functional traits using DEB modelling will be useful in further deep-sea studies on the connectivity and resilience of populations.

Changes in Adolescents’ Dietary Intake Following the Initiation of an 8-Week Exercise Program

Purpose: To assess changes in dietary intake of adolescents following an 8-week aerobic exercise program. Methods: Twenty-six adolescents (14–18 years) participated in an 8-week aerobic exercise program on cycle ergometer at their high school in Quebec, Canada. Twenty-four hour recalls were collected pre- and post-intervention. A two-way repeated measures ANOVA and paired sample t-tests were used to assess differences in energy and dietary intake parameters (food quantity, diet quality, eating patterns) between pre- and postintervention. Results: A decrease in total daily energy intake (–287.8 kcal, P = 0.007), in meal size at lunch (–110.1 g, P = 0.02) and dinner (–143.7 g, P = 0.03), in food density at breakfast (–1.8 kcal/g, P = 0.04), in daily carbohydrate intake (–56.1 g, P = 0.005), and in percentage of energy intake consumed at school (–5.1%, P = 0.04) were observed following initiation of an aerobic exercise program. No change in healthy eating index scores or percentage of energy from processed foods was observed. Conclusions: Changes in energy intake, food quantity, and eating pattern but not diet quality (Healthy Eating Index or food processing scores) were observed following the initiation of an aerobic exercise program. Nutrition interventions may be needed, in addition to an exercise program, to target diet quality and promote healthy eating habits in adolescents.

SAFETY OF VEGETABLE RAW MATERIALS USED IN FOOD SYSTEMS

The developed fortified products contain ingredients that are widely studied for a strictly defined set of macro-and micro-components that are deficient for the human body. However, the presence of additional unregulated elements in the enriching raw materials is not fully studied. In this context, the issue of a comprehensive study of not only the nutritional value, but also the element composition of raw materials that increase the nutritional density of the enriched product is relevant. The aim of the research was to study the safety and chemical composition of plant raw materials used to increase the nutrient density of food systems. Freeze-dried ground apples produced by PJSC Sibirsky gostinets (Pskov region, Moglino village) and Brazil nut kernels produced by Comservice LLC (Moscow region, Mytishchi) were used as research objects. It is established that the studied plant materials are safe for human health in terms of their elemental composition and microbiological indicators. The study of food density showed that ground apples did not correspond to the declared levels of protein and fat by 45,2 and 96,2%, respectively. However, Apple powder has a relatively high content of mineral elements Mo, Na, Si, Ga, B, sugar, starch, dietary fiber and organic acids, Brazil nut kernels-Mg, Se, Cu, P, CA, Mn, Zn, Fe, Co, Ni, Al, protein and lipids.

Kleptoparasitic Hawk-Dove Games

The Hawk-Dove game is a classical game-theoretical model of potentially aggressive animal conflicts. In this paper, we apply game theory to a population of foraging animals that may engage in stealing food from one another. We assume that the population is composed of two types of individuals, Hawks and Doves. Hawks try to escalate encounters into aggressive contests while Doves engage in non-aggressive displays between themselves or concede to aggressive Hawks. The fitness of each type depends upon various natural parameters, such as food density, the mean handling time of a food item, as well as the mean times of conflicts over the food. We find the Evolutionarily Stable States (ESSs) for all parameter combinations and show that there are two possible ESSs, pure Hawks, or a mixed population of Hawks and Doves. We demonstrate that for any set of parameter values there is exactly one ESS.

Modelling mussel (<i>Mytilus spp.</i>) microplastic accumulation

Microplastics (MPs) are a contaminant of growing concern due to their widespread distribution and interactions with marine species, such as filter feeders. To investigate the MPs accumulation in wild and cultured mussels, a dynamic energy budget (DEB) model was developed and validated with the available field data of Mytilus edulis (M. edulis, wild) from the North Sea and Mytilus galloprovincialis (M. galloprovincialis, cultured) from the northern Ionian Sea. Towards a generic DEB model, the site-specific model parameter, half-saturation coefficient (Xk), was applied as a power function of food density for the cultured mussel, while for the wild mussel it was calibrated to a constant value. The DEB-accumulation model simulated the uptake and excretion rate of MPs, taking into account environmental characteristics (temperature and chlorophyll a). An accumulation of MPs equal to 0.53 particles per individual (fresh tissue mass 1.9 g) and 0.91 particles per individual (fresh tissue mass 3.3 g) was simulated for the wild and cultured mussel after 4 and 1 years respectively, in agreement with the field data. The inverse experiments investigating the depuration time of the wild and cultured mussel in a clean-from-MPs environment showed a 90 % removal of MPs load after 2.5 and 12 d respectively. Furthermore, sensitivity tests on model parameters and forcing functions highlighted that besides MPs concentration, the accumulation is highly dependent on temperature and chlorophyll a of the surrounding environment. For this reason, an empirical equation was found, directly relating the environmental concentration of MPs, with the seawater temperature, chlorophyll a, and the mussel's soft tissue MPs load.

Global generalized solutions to a forager–exploiter model with superlinear degradation and their eventual regularity properties

In this paper, we consider a cascaded taxis model for two proliferating and degrading species which thrive on the same nutrient but orient their movement according to different schemes. In particular, we assume the first group, the foragers, to orient their movement directly along an increasing gradient of the food density, while the second group, the exploiters, instead track higher densities of the forager group. Specifically, we will investigate an initial boundary-value problem for a prototypical forager–exploiter model of the form [Formula: see text] in a smoothly bounded domain [Formula: see text], where [Formula: see text], [Formula: see text] is nonnegative and the functions [Formula: see text] are assumed to satisfy [Formula: see text], [Formula: see text] as well as [Formula: see text] respectively, with constants [Formula: see text], [Formula: see text] and [Formula: see text] and [Formula: see text]. Assuming that [Formula: see text], [Formula: see text] and that [Formula: see text] satisfies certain structural conditions, we establish the global solvability of this system with respect to a suitable generalized solution concept and then, for the more restrictive case of [Formula: see text] and [Formula: see text], investigate an eventual regularity effect driven by the decay of the nutrient density [Formula: see text].

Do Geese Facilitate or Compete with Wintering Hooded Cranes (Grus monacha) for Forage Resources?

Foraging is the key behavior of waterbirds, which profoundly affects the survival of their population, and it is affected by interspecific interaction. At Shengjin Lake in China, owing to the reduced availability of suitable habitats for a large population of migratory waterbirds (especially wild geese) over winter, mixed species foraging inevitably occurs. This study aimed to investigate whether mixed-species foraging affects the foraging of hooded cranes (Grus monacha). Fields surveys were carried out at Shengjin Lake from November 2018 to March 2019. Mixed-species foraging was surveyed between the flocks of hooded cranes and three species of geese, greater white-fronted geese (Anser albifrons), lesser white-fronted geese (Anser erythropus) and bean geese (Anser fabalis). Instantaneous scanning and focal animal methods were used to collect behavioral samples of hooded cranes. The quadrat method was used to survey the food density in three habitats: meadows, mudflats, and paddy fields. The results showed that the foraging success rate of hooded cranes was not significantly correlated with food density and the relative flock size in the mixed-species foraging flock in meadows, but a significant negative correlation with the relative flock size in mudflats. However in paddy fields it was a significant positive correlation with the relative flock size. Foraging efforts of hooded cranes were negatively correlated with food density and positively correlated with the relative flock size in meadows. In mudflats, foraging efforts of hooded cranes had a significant positively correlation with the relative flock size, however, there was a significant negative correlation with the relative flock size in paddy fields. To sum up, larger numbers of geese mixed with hooded cranes has a favorable effect on the foraging of hooded cranes in meadows and mudflats, however, the reverse was observed in the paddy fields.

Modelling mussel (<i>Mytilus</i> spp.) microplastic accumulation

Microplastics (MPs) are a contaminant of growing concern due to their widespread distribution and interactions with marine species, such as filter feeders. To investigate the MPs accumulation by wild and cultured mussels, a Dynamic Energy Budget (DEB) model was developed and validated with the available field data of Mytilus edulis (wild) from the North Sea and Mytilus galloprovincialis (cultured) from the North Ionian Sea. Towards a generic DEB model, the site-specific model parameter, half saturation coefficient (Xk) was applied as a power function of food density for the cultured mussel, while for the wild it was calibrated to a constant value. The DEB-accumulation model simulated the uptake and excretion rate of MPs, taking into account environmental characteristics (temperature and chlorophyll-a). An accumulation of MPs equal to 0.64 particles individual−1 (fresh tissue mass 1.9 g) and 0.91 particles individual−1 (fresh tissue mass 3.4 g) was found for the wild and cultured mussel respectively, in agreement with the field data. The inverse experiments investigating the depuration time of the wild and cultured mussel in a clean from MPs environment showed a 90 % removal of MPs load after 3 and 14 days, respectively. Furthermore, sensitivity tests on model parameters and forcing functions highlighted that besides MPs concentration, the accumulation is highly depended on temperature and chlorophyll-a of the surrounding environment. For this reason, an empirical equation was found relating directly the concentration of MPs in seawater, with MPs accumulation in mussel’s soft tissue, temperature and chlorophyll-a.