Entropy and Fractal Techniques for Monitoring Fish Behaviour and Welfare in Aquacultural Precision Fish Farming—A Review

In a non-linear system, such as a biological system, the change of the output (e.g., behaviour) is not proportional to the change of the input (e.g., exposure to stressors). In addition, biological systems also change over time, i.e., they are dynamic. Non-linear dynamical analyses of biological systems have revealed hidden structures and patterns of behaviour that are not discernible by classical methods. Entropy analyses can quantify their degree of predictability and the directionality of individual interactions, while fractal dimension (FD) analyses can expose patterns of behaviour within apparently random ones. The incorporation of these techniques into the architecture of precision fish farming (PFF) and intelligent aquaculture (IA) is becoming increasingly necessary to understand and predict the evolution of the status of farmed fish. This review summarizes recent works on the application of entropy and FD techniques to selected individual and collective fish behaviours influenced by the number of fish, tagging, pain, preying/feed search, fear/anxiety (and its modulation) and positive emotional contagion (the social contagion of positive emotions). Furthermore, it presents an investigation of collective and individual interactions in shoals, an exposure of the dynamics of inter-individual relationships and hierarchies, and the identification of individuals in groups. While most of the works have been carried out using model species, we believe that they have clear applications in PFF. The review ends by describing some of the major challenges in the field, two of which are, unsurprisingly, the acquisition of high-quality, reliable raw data and the construction of large, reliable databases of non-linear behavioural data for different species and farming conditions.The work was supported by the Spanish MINECO (Grant RTC-2014–2837-2- “SELATUN: Minimización de la problemática del mercurio del atún y valorización del atún como alimento saludable, Programa Retos-Colaboración 2014”. The funding source had no involvement in the preparation of this manuscript

The Effect of Ethanol on Cellular Movements and Development in C. elegans

Neural tube development, which gives rise to the central nervous system, is vital to embryonic development. Neural tube defects, like spina bifida, are serious and common congenital defects which can result in life-long medical complications. Folic acid has been used as a preventative measure for neural tube defects and has appeared to decrease the occurrences of neural tube defects. However, the mechanism behind folic acid’s role in neural tube development is unclear. Furthermore, some evidence suggests that ethanol decreases the levels of folates and folate coenzymes in the fetal brain and downregulates folic acid metabolism genes. To better understand the connections between ethanol, folic acid, and neural tube defects, we are using the roundworm Caenorhabditis elegans as a model system. C. elegans are a good model system for this study because despite lacking a neural tube, cellular processes involved in neural tube development are conserved. Upon the introduction of ethanol to reproductive worms, my data indicate there was an increase in the embryonic lethality and a decrease in the brood sizes of the worms. We show that around the embryonic elongation stage some worm embryos born from worms exposed to ethanol cease development. We also provide evidence that in these ethanol exposed worms, cell migration of the endoderm may be affected but intestinal cell fate is not. Through studying the movements of the cells during development we hope to be able to uncover specific cellular events that are affected upon exposure to ethanol

Effects of Estrone and Temperature on the Predator-Prey Relationship Between Bluegill Sunfish and Fathead Minnows

Contaminants of emerging concern (CECs), for example estrone (E1), and their effects to aquatic organisms have been researched consistently, however little is known about how temperature can influence exposure effects of CECs. Chemical exposures and temperature have been shown to independently affect fish and their populations, but little is known about their impact on predator-prey relationships. Previous studies indicate that changes arise through behavioral and physiological changes in either predator or prey. To test the effects of E1 and temperature on predator-prey relationships, adult bluegills and larval fathead minnows were exposed to E1 (125, 625 ng/L) or an ethanol control for 30 days at four temperatures (15°C, 18°C, 21°C, 24°C) to reflect natural variation between seasons.Behavioral experiments were conducted to assess the effects of temperature and estrone exposure on minnows in the larval life stage (i.e., foraging and predator evasion). Significant differences due to water temperature were observed in body length, escape angle, and total escape response of predator evasion responses. On day 30 of exposure, predation trials were performed using one adult sunfish and a group of five control and five exposed (125 or 625ng/L) larvae. Exposed larvae (125ng/L: 49.2%; 625ng/L: 52.9%) displayed a concentration-dependent reduction in survival in comparison to the control minnows (74.2%) following predation from the sunfish predator. Additionally, the prey catching abilities of the sunfish may have been affected, potentially mitigating the predation effects on the minnows. In addition, a series of anatomical and physiological endpoints were explored to assess the independent and interactive effects of estrone exposure and temperature on plasma vitellogenin induction, blood glucose, histology, and morphometric indices on sunfish in the adult life stage. This study provides evidence that minnow populations may suffer due to impaired predator evasion performance and provides information for environmental agencies evaluating ecological effects of exogenous estrogens and climate change

Neurobehavioral and Gene Expression Effects of Early Embryonic Methylmercury Exposure in Yellow Perch (Perca flavescens) and Zebrafish (Danio rerio) Larvae

Methylmercury (MeHg) is a pervasive and persistent neurotoxic environmental pollutant known to affect the behavior of fish, birds and mammals. The present study addresses the neurobehavioral and gene expression effects of MeHg in yellow perch (Perca flavescens) and zebrafish (Danio rerio) embryos. The rationale for this study originated from an interest to understand the behavioral and molecular phenotypes of environmental MeHg exposure in the yellow perch, an ecologically and economically relevant species of the North American Great Lakes region. Both MeHg and the yellow perch coexist in a common ecosystem: the North American Great Lakes. However, the effects of this organism-contaminant interaction are poorly understood. The zebrafish was utilized here as a surrogate model for yellow perch, due to its ease of rearing, whole sequenced genome and its status as an NIH endorsed model organism. The objectives of this study were to understand the effects of MeHg on behaviors that are critical for survival both in yellow perch and zebrafish. Among the behavioral paradigms tested, this study addressed fundamental behaviors for the survival of young larval fish, namely swimming and prey capture. Furthermore, this study screened for gene expression alterations in the same cohorts of fish for which behavioral analysis was performed; this was done to gain insight into the gene pathways involved in MeHg-induced neurotoxicity, as well as to expand the knowledge about biomarkers of MeHg exposure in the yellow perch. Here, we have uncovered important differences and similarities between the effects of MeHg exposure in yellow perch and zebrafish larvae, both in terms of behavioral and molecular responses to MeHg. The findings of this study suggest that environmentally relevant MeHg exposure can adversely affect the behavior of yellow perch larvae and impair fundamental survival skills. Furthermore, this study determined that although it would be challenging to relate behavioral endpoints between yellow perch and zebrafish, molecular responses between these two species could be more conserved

ENGINEERING A HIGH-THROUGHPUT SCREENING PLATFORM FOR ASSESSING DEVELOPMENTAL NEUROTOXICITY THROUGHOUT HEAD- REGENERATION IN SCHMIDTEA MEDITERRANEA

The increase in commercially used chemicals that are inadequately evaluated for safety and risk to development has created a reticent threat to human health. Addressing these deficiencies is compounded by limited methodologies to determine the etiology of exposure-related developmental neurotoxicity (DNT). Current means of assessing DNT are largely retrospective and limited by the expensive, time-consuming, and labor-intensive use of laboratory animal models, thereby motivating a global research effort to produce alternative chemical screening assays. In this work, we have developed a novel high- throughput platform that serves as a new tool to evaluate the effects of exogenous chemical exposure on developmental processes in the non-vertebrate animal model, Schmidtea mediterranea (Smed). We demonstrate that light avoidance in Smed is a robust behavior that can be assayed throughout head regeneration and is temporally correlated to the anatomical development of central nervous system structure. Thus, reacquisition of this behavior serves as a surrogate measure of neurodevelopment that can be utilized to characterize exposure-related effects in DNT. Our high-throughput screening platform enables a more sensitive classification of these responses and assesses both endpoint and temporal effects of chemical exposure in DNT, which paves the way for more exhaustive and predictive chemical assessment to minimize the impact on human health

Modulation of Estrogenic Effects Via Temperature on Two Life Stages of Fathead Minnow

Human-mediated environmental impacts can induce changes in the expression of complex behaviors within individuals, and alter the outcomes of interactions between individuals. Although the independent effects of a number of important stressors on aquatic biota are well documented (e.g., exposure to environmental contaminants), fewer studies have examined how natural variation in the ambient environment modulates these effects. In this study, factorial experiments were conducted to assess the influences of temperature and estrogen concentration on two life stages of fathead minnow (Pimephales promelas). Larval and adult minnows were exposed for 21 or 30 days, respectively, to 3 concentrations of estrone (nominally at 25, 125, and 625 ng/L) or to an ethanol carrier control (0 ng/L), at four water temperatures (15, 18, 21, and 24 °C) reflecting natural seasonal variation. A series of behavioral experiments were conducted to assess the independent and interactive effects of temperature and estrogen exposure on intra- and interspecific interactions in three contexts with important fitness consequences (i.e., reproductive behavior, foraging, and predator evasion). In addition, a series of anatomical and physiological endpoints were explored to assess the independent and interactive effects of chemical exposure on plasma vitellogenin induction, blood glucose, hematocrit, histology, and morphometric indices. Evidence was obtained suggesting that thermal regime can modulate the effects of exposure on larval survival, larval predator-prey interactions, and adult physiological and anatomical endpoints, even within a relatively narrow range of ambient temperatures. These findings improve our understanding of the outcomes of interactions between anthropogenic stressors and natural abiotic environmental factors, and suggest that such interactions can have ecological and evolutionary implications for freshwater populations and communities

Distinct modes of floor plate induction in the chick embryo

To begin to reconcile models of floor plate formation in the vertebrate neural tube, we have performed experiments aimed at understanding the development of the early floor plate in the chick embryo. Using real-time analyses of cell behaviour, we provide evidence that the principal contributor to the early neural midline, the future anterior floor plate, exists as a separate population of floor plate precursor cells in the epiblast of the gastrula stage embryo, and does not share a lineage with axial mesoderm. Analysis of the tissue interactions associated with differentiation of these cells to a floor plate fate reveals a role for the nascent prechordal mesoderm, indicating that more than one inductive event is associated with floor plate formation along the length of the neuraxis. We show that Nr1, a chick nodal homologue, is expressed in the nascent prechordal mesoderm and we provide evidence that Nodal signalling can cooperate with Shh to induce the epiblast precursors to a floor-plate fate. These results indicate that a shared lineage with axial mesoderm cells is not a pre-requisite for floor plate differentiation and suggest parallels between the development of the floor plate in amniote and anamniote embryos

Polystyrene nanoplastics disrupt glucose metabolism and cortisol levels with a possible link to behavioural changes in larval zebrafish

Plastic nanoparticles originating from weathering plastic waste are emerging contaminants in aquatic environments, with unknown modes of action in aquatic organisms. Recent studies suggest that internalised nanoplastics may disrupt processes related to energy metabolism. Such disruption can be crucial for organisms during development and may ultimately lead to changes in behaviour. Here, we investigated the link between polystyrene nanoplastic (PSNP)-induced signalling events and behavioural changes. Larval zebrafish exhibited PSNP accumulation in the pancreas, which coincided with a decreased glucose level. By using hyperglycemic and glucocorticoid receptor (Gr) mutant larvae, we demonstrate that the PSNP-induced disruption in glucose homoeostasis coincided with increased cortisol secretion and hyperactivity in challenge phases. Our work sheds new light on a potential mechanism underlying nanoplastics toxicity in fish, suggesting that the adverse effect of PSNPs are at least in part mediated by Gr activation in response to disrupted glucose homeostasis, ultimately leading to aberrant locomotor activity