Allostasis and it's correlate vitality; measured with reflex action impairment and injury

Figure 1. Alternative models of regulation. Homeostasis describes mechanisms that hold constant a controlled variable by sensing its deviation from a “setpoint” and feeding back to correct the error. Allostasis describes mechanisms that change the controlled variable by predicting what level will be needed and then overriding local feedback to meet anticipated demand, Sterling (2003).

Physiological regulation is considered the cornerstone of animal survival and avoidance of death. Inability to regulate is indicated by vitality impairment and causes an animal to exceed its capacity for life. To understand and predict the causes for survival and death, we must be able to measure appropriate state and rate variables involved in regulation. The generally accepted model of physiological regulation is homeostasis, based on the concept of stability through constancy. However homeostasis is unable to explain accumulating medical evidence that physiological variables do not remain constant. Clearly a more comprehensive model of physiological regulation is needed.  

Allostasis is a model of physiological regulation based on the concept of stability through change (Sterling 2003). Allostasis is able to account for evidence that physiological variables are not constant. The allostasis model connects easily with modern concepts in sensory physiology, neural computation, and optimal design, to produce anticipatory regulation. Allostasis was developed with the recognition that the goal of regulation is not constancy, but rather fitness under natural selection, that implies preventing errors and minimizing costs. Both needs are best accomplished by using prior information to predict physiological demand and then adjusting all variables to meet it. In allostasis an unusual variable value is not a failure to maintain a setpoint, but is a response to some prediction made through perception or prior knowledge. Constancy is not a fundamental condition for life. A mean value need not imply a setpoint but rather the most frequent demand.

The brain has close access to essentially every somatic cell through nerve cell connections. The broad metabolic patterns over short and long time scales, and under mild as well as emergency conditions are controlled by the brain. In other words, the brain regulates both physiology and its supporting behavior (Sterling 2003). The use of reflex action impairment to measure vitality and predict survival and mortality is consistent with the allostatic model because it is representative of key elements of physiological regulation; including perception, behavior, and neural control of somatic cell function. Injury also measures vitality impairment because of its direct effects on neural and somatic cell function, hence allostasis. 

Reflex action impairment and injury can measure vitality and predict survival and mortality in taxa ranging from invertebrates to humans. Clearly the presence of higher brain function is not a necessary condition for the allostatic model. Instead, simple interactions of neural and somatic cells can produce allostasis regulation and its correlate, vitality. It remains to elucidate the comparative details of physiological regulation as it developed in new phyla through evolutionary time.

When studying the causes for death, shifting focus from measurement of lower level plasma variables (cortisol, lactate, glucose, O2, pH) to higher level variables (vitality in its various guises) would advance the assessment of physiological regulation and its role in survival and death. Particular values for plasma variables are of secondary importance, until reaching outer limits of operation. The interactions of plasma variables are of primary importance (Ellis and Del Giudice 2014). The homeostatic model fails to capture the importance of stability through change; how animals adapt and ultimately go beyond their physiological limits. The allostatic model addresses stability through change and invites adaption and evolutionary fitness.

Reflex action impairment is probably a biomarker for impairment of physiological regulation and this is why the RAMP curve is non-linear, reflecting the inflection point where physiological regulation is lost and death results. Addition of injury to RAMP adds details of direct injury effects on physiological functioning and regulation, e.g. compromising integument gatekeeping (skin, gut, gill, lung).

Measuring reflex action impairment in sole and plaice; preliminary steps to making RAMP

Collection of fish with beam trawl, Jochen Depestele

The beginning steps for measuring reflex action impairment and making a RAMP are detailed in “Calibration tests for identifying reflex action mortality predictor reflexes for sole (Solea solea) and plaice (Pleuronectes platessa): preliminary results” authored by Depestele, J. et al. 2014. Experiments were designed to collect sole and plaice using short hauls of a beam trawl, to test their reflex actions, and to identify consistent reflexes for making RAMP. These experiments followed steps for making RAMP.

A short video demonstrates testing plaice for reflex actions including righting, eye roll (vestibular-ocular response), evade, operculum, mouth, and tail grab. Fish are shown in a series of increasing impairment.

Conclusions from the study included:

Preliminary investigations have been undertaken on-board the RV Belgica to assess the potential presence of a range of reflexes in sole and plaice. A wide range of potential reflexes was investigated prior and during the sea trial, leading to a final selection of seven reflexes with a good potential of being consistently present in fish in a favorably vital condition. Fish in a “perfect” condition could not be retrieved, but 22 individuals of plaice and sole were selected from short hauls and their survival potential was evaluated during 70 hours in on-board holding facilities. Only one sole died, and indicated hence that the control fish for the calibration test serve purpose.

Holding tanks for fish on board RV Belgica, Jochen Depestele

The final selected reflex actions were very similar for sole and plaice, except for one. Forced opening of sole’s operculum did not reveal much resistance of the fish, while holding plaice by its head did not induce curling of the fish. The most consistent reflex actions for sole were called “stabilize, mouth, and tail grab”, followed by the “vestibular-ocular response”. Vital individuals seemingly dig into the sand or stabilize themselves onto the floor of the water-filled box. They also keep their mouth closed when trying to open it with a probe. When fish have stabilized, they respond clearly to grabbing their tail or even tickling it. The “head” reflex was easy to assess, though not always present. However, it is clear that vital soles curled around one’s hand when they had been in holding tanks. This was not that obvious for fish that were just released from the codend. Natural righting was observed regularly, although some individuals remained at their backs for >5 sec and did not return to their natural position at all or only after stimulating them. The consistency could thus be questioned, but good candidate reflexes were proposed for sole, and should be further evaluated. The most consistent reflexes of plaice were the turning of the eyes when the fish was turned around longitudinally. The resistance of plaice to forced opening of the operculum was a clear reaction as well. Not fully consistent, but nevertheless a good indication of the reflexes was the “evade” response and the “tail grab”. When the tail is touched or grabbed in a “good” way (which might require some practice), then the fish swim away, or at least the fins stimulate propulsion. The mouth of plaice was easily opened, but mostly the individuals tried to close it or seemingly opposed to the forced movement.

Our investigations confirmed that on-board holding facilities result in high survival of plaice and sole from very short hauls (<20min). Investigated individuals were non-randomly selected and thus it was not surprising that their physical injuries were limited. These individuals were suitable for developing the reflexes, although they were limited in number (22 for plaice and 22 for sole) and they also did not range over a wide variety of fish conditions (e.g. limited length variability). The seven reflexes from these preliminary investigations are therefore proposed as candidates for the development of a RAMP score for sole and plaice.

The tests of the reflexes were run directly after releasing fish from the codend. When examining the survival from fish that were accommodated for some time (e.g. 48 hours), we noted that they reacted more strongly and had much clearer responses to the reflex tests. In particular the tail grab worked very nicely for sole when their status (alive or dead) was tested. Therefore we suggest that the proposed reflexes are tested once more on surviving individuals of short hauls after an accommodation period of >24hours. Consistency of the outcome of the reflex tests is expected to be improved when the impairment from the catching process is accounting for. Other recommendations for follow-up tests relate to the registration of potential environmental and biological confounding factors.

Coho salmon, RAMP, knowledge-action boundary, and stakeholder conservation actions

Coho salmon, NOAA Fisheries

A paper entitled "Bycatch mortality of endangered coho salmon: impacts, solutions, and aboriginal perspectives" by Raby et al. 2014 introduces a new model approach for bycatch conservation research. The paper identifies the use of vitality assessment in the form of RAMP to inform stakeholder and manager decisions about bycatch handling and avoidance for coho salmon in the Fraser River, Canada.

“This paper demonstrates that fisheries science, biotelemetry, and human dimensions surveys can be combined to evaluate a conservation problem for an endangered population of salmon and inform resource managers and users. We consider this a model approach for conservation research, because it can help address the persistent challenge of generating science that “bridges the knowledge-action boundary” (Cook et al. 2013). A well-known barrier to transitioning from scientific knowledge to conservation action is the scientific structure that values publications and grant income but not engagement with stakeholders (Cook et al. 2013).”

“Abstract. We used biotelemetry and human dimensions surveys to explore potential solutions to migration mortality of an endangered population of coho salmon caught as bycatch in an aboriginal beach seine fishery. From 2009 to 2011, wild coho salmon caught as bycatch in the lower Fraser River (Canada) were radio-tagged and tracked as they attempted to complete their migrations to natal spawning areas over 300 km upstream. Failure to survive to reach terminal radio receiving stations averaged 39% over three years. This mortality estimate is low compared to those obtained from telemetry studies on other salmon fisheries in the Fraser River. However, this value is markedly higher than the mortality estimate currently used to manage the fishery’s impact. It is also in contrast to the perceptions of the majority of aboriginal fishers, who did not think survival of coho salmon is affected by capture and release from their fishery. Increased probability of survival was associated with lower reflex impairment which is consistent with previous findings. Reflex impairment was positively correlated with entanglement time, suggesting that greater efforts by the fishers to release bycatch from their nets quickly would minimize post-release mortality. Survey responses by aboriginal fishers also suggested that they are receptive to employing new bycatch handling methods if they are shown to increase post-release survival. However, attempts to facilitate revival of a subset of captured fish using cylindrical in-river recovery bags did not improve migration success. Fisheries managers could use the new information from this study to better quantify impacts and evaluate different harvest options. Since aboriginal fishers were receptive to using alternate handling methods, efforts to improve knowledge on minimizing reflex impairment through reductions in handling time could help increase bycatch survival. Such a direct integration of social science and applied ecology is a novel approach to understanding conservation issues that can better inform meaningful actions to promote species recovery.”