It is incredibly fitting that my January blog post is on the concept of “acclimation” — because we are all acclimitizing to the new year and a new semester.
This post speaks to another often overlooked sentence that is frequently seen in published articles – variations of “–organism– were acclimated to –experimental setup– for –time–” (fill in the organism, experimental setup, and time).
But where does that duration of time come from? The more familiar students get with the literature, the more they realize that this time can be 5 minutes, 5 hours, 5 days.
The simple answer, as with most things: it depends. The bottom line, in my personal scientific opinion, is that the time you choose must be scientifically grounded and justifiable.
So, what does it depend upon? What do we look at to start establishing this scientifically-grounded justification? [take a deep breath, and keep in mind this list is no exhautive – I am human, after all]:
- Water chemistry and water flow/movement
- Lighting (level and cycle)
- Population density/presence (or absence) of conspecifics
- The presence of visual stimuli
Once we have developed an understanding of what is changing physically (or chemically) within the environment, we have to then turn to the organism to determine how we know when they have “acclimated” to those changes.
So, what can we measure to justify acclimation?….you guessed it, it depends.
A [non-exhaustive] list of suggestions:
- Cortisol levels
- Erratic swimming behaviour/darting/velocity metrics
- Edge-seeking behaviour
- Vertical water column placement
- Interaction with conspecifics
- Respiration rate
- Burrowing
- Nest building
- Egg laying/reproductive displays
Regardless of which behaviour is best-suited for your organism and situation of interest, you are looking for a plateau. That is the justification – the respiration rate stabilizes, the velocity remains constant, organisms burrow and surface in consistent time intervals. It can take multiple tries to get your behavioural thresholds figured out and to establish what that plateau looks like.
…and sometimes individuals still won’t acclimate before you run out of logistical time (i.e., you can’t acclimate an organism for its entire life stage, if you need to analyze that stage!).
When you are considering the findings of a behavioural paper, check their acclimation – search for that justification and if you can’t find it, consider that in how you interpret the results.