From a stimulus-response (S-R) point of view, or even with an intermediate step, involving cognition (S-O-R), the existence of behavioral variablity in organisms, even under tightly controlled experimental conditions, suggests that 1) the relevant inputs to the system have not been fully characterized, 2) even the most minute difference in system inputs can produce vastly variable behavioral output, or 3) that behavior is fundamentally variable. Any of these possibilities leads to the conclusion that precise behavioral prediction, at any given moment, is virtually impossible. One can, however, re-conceptualize the challenge of understanding behavior such that it involves not what the organism will do from moment to moment, but what the characteristics of the system that governs the behavior of the organism are. In this paper, I outline a closed-loop cybernetic approach to understanding behavior, for which behavioral variability is actually a requirement. Findings are presented from a series of experiments across species, and using computer simulations, that support a cybernetic interpretation of behavior. I argue that behavioral variability provides adaptive advantages to organisms – regardless of whether that variability is produced by noise, or is actively generated by nervous systems. Finally, I discuss some ideas from embodied cognition that impose constraints on the variability of behavior.

In late 2019, at multiple hatcheries in California’s Central Valley (CCV), offspring of recently spawned fall-run Chinook salmon (Oncorhynchus tshawytscha) exhibited abnormalities in swimming, lethargy, and high early life-stage mortality; the combination of these symptoms is commonly referred to as thiamine deficiency complex (TDC). The cause of thiamine deficiency in Pacific salmonids is hypothesized to be due to a lack of diet heterogeneity and reliance on northern anchovies (Engraulis mordax), containing high levels of thiaminase, a thiamine-cleaving enzyme. Of CCV’s four runs, the endangered Sacramento River winter-run Chinook salmon (WRCS) is perhaps the most vulnerable to thiamine deficiency as any additional stressor will exacerbate current threats to survival. The goal of this study was to evaluate the effect of thiamine supplementation in pre-spawn WRCS females on their offspring egg thiamine concentrations, survival, prevalence of TDC-related symptoms, and physiological performance and behavioral traits. Sixty female WRCS at Livingston Stone National Fish Hatchery were randomly administered either a thiamine injection (n=33; 500 mg/ml thiamine hydrochloride) at a dose of 50 mg/kg body weight or a sham injection (n=27; sterile saline solution) at a volume of 0.127 ml/kg body weight. After spawn, a subset of fertilized eggs from each female were analyzed for thiamine concentration. Eyed embryos were transferred to the University of California, Davis and kept for observations of TDC, survival, and to assess the effects of maternal thiamine treatments on offspring physiology and behavior. Upper thermal tolerance, routine metabolic rate, spontaneous swimming activity, boldness, and anti-predator responses were evaluated in swim-up fry. On average, total egg thiamine concentrations were 5.02 and 34.91 nmol/g for untreated (n=27) and thiamine treated (n=33) females, respectively. Mortality rate of offspring from untreated females averaged 32.97 ± 0.33 %, with rates ranging from 0 to 100%, while offspring from thiamine treated females had a mean mortality rate of less than 1%. Using a binomial logistic regression model, we predicted that a mean total egg thiamine concentration of ~5 nmol/g supports 95% survival within a family (EC95). There were no statistically significant effects of maternal treatment on any of the physiological or behavioral metrics assessed in this study. Overall, we recommend the administration of supplemental thiamine to increase thiamine concentrations past the threshold at which TDC symptoms are commonly observed; however, additional research should be conducted to further examine potential latent effects of thiamine deficiency in Pacific salmonids.

Background

Results

Conclusion