Spiders and Stress

[The Snark]

It seems to me this is something many people on AB could contribute to.

Stress can be very serious and all too often overlooked problem with animals but especially with animals that exhibit little or no symptoms. Spiders often display no visible outward signs of being stressed unless the keeper is not only highly experienced but has a wide frame of reference to compare to.

In humans, stress can be very difficult to diagnose. Often extensive interviews and subtle physiological alterations are all the experts have to go on in diagnosing stress. PTSD is a typical example, with diagnostics still in their infancy.

With spiders, if a keeper doesn't know the animal and it's habits under many circumstances, conditions and habitats, stress may be entirely over-looked.
We have recently had a dramatic increase in the wild population of Nephila in the surrounding area and only by comparing numerous individual spiders have I been able to identify stress or potential stress conditions. This has been a rather startling eye opener for me. Nephila Pilipes typifies and exemplifies this problem.

The young adult Pilipes will triple to quadruple it's size within 1 month under ideal conditions. From about 1/2" in body length to nearly 2 inches. For many experienced keepers, those who really know Nephila, this may seem to be extremely unusual but has become a fact in my studying them. I have the advantage of having one lovely lady right outside my wife's office I have been closely observing that is serving as a control - ideal conditions. Pesticides are banned from the premises, her web is in a very stable location, and right next to a stagnant water canal, food is in abundance. I first noticed her, a typical nearing maturity juvenile, the second week of December. Yesterday I spent a half hour carefully estimating her size. She is exemplary of the Pilipes population here. We have another in our back yard displaying similar growth but she is out over the river and I need wings if I want to closely observe her.

So let's examine stress causes.
-Temperature
-Humidity
-Environment stability
Three obvious basics. But not enough to base a hypothesis on.
-Diurnal/nocturnal cycles
-Presence of competitors
-Correct food in correct quantities
-Toxins in the environment
-Toxins in the food
-Over feeding
And I'm sure experienced keepers could add to this list. And they all can have an effect.

Think an ideal envelope. You have a spider, it matures, lives out an uneventful life then eventually dies. How do you know it lived under ideal circumstances? Ordinarily the only indicator we have to go by is age. But age can be very deceptive. In the case of Pilipes they live one year. But is that one year spent fully thriving or just barely hanging on? With our local Pilipes, going by individual size, it appears only one out of about 10 put on a major growth spurt and will spend the majority of it's life span as a full sized adult. Most of the individuals I see around here barely get more than 1 inch in length.

So how can we tell the difference between just surviving and living their lives to the max? Thoughts?

 

[CJJon]

I really think you have to separate out psychological stress and environmental stressors in relation to failure to thrive. Spiders don't get PTSD or feel anything akin to stress. You really can't compare it to what humans normally think of as stress and you certainly can't directly measure spider "stress".

Perhaps reproduction would be something to measure. If an individual successfully matures, mates and reproduces then I would call that a successful existence and the conditions it lived under adequate. If you looked at enough samples you could plot out all the successes and get a general idea of what environmental factors are "ideal" for the majority of the samples. Then you could compare an individual's environment to the ideal derived from the study to estimate it's chances of a nominal existence.

 

[The Snark]

I really think you have to separate out psychological stress and environmental stressors in relation to failure to thrive.

A good point. Stress is undefined in my first post. Spiders don't have psychological issues, at least nothing we could measure.

However, stress. Anything that taxes bodily functions in any form. So it can run the gamut from burning more calories than normal in building and maintaining a web in a certain location as opposed to more salubrious accommodations to multiple suitors present to a form of food the animal isn't adapted to to coping with a debility to the drain on system resources in the presence of a disease and on and on. Life limiting factors. Stress may be any circumstance that is not beneficial to the animal, or it could be beneficial in some manner that is not obvious.

Other considerations: Various conditions that animals have evolved in/under, that have made it to what it is today. I would point at the various subtle alterations where rat liver RNA exceeded the normal predictable under accelerated life conditions in the raceway in a laboratory. Most of these test runs received the label Not Sustainable. Ideal performance was achieved, but this would inevitably cause some biological imbalance later in the animals time frame, possibly several generations down the road. So stress can be beneficial or detrimental.

The envelope. A spider in a controlled environment, a containment, enjoys the perfect temperature range, the perfect humidity, the minimal amount of calories burned during it's nutrient intake. Artificial lighting that is unchanging year round. No competition for food, no predators. The middle of the ideal envelope with all factors. Is it healthier? Will it live longer? Or will this set of ideals actually combine and contribute towards weaker genetics and a shorter life span?

Animals without evolved cerebral cortexes operate by triggers. Circumstances that can cause it to operate outside the ideal envelope. It is possible, even likely, that some of these triggers are short term detrimental but longer term beneficial. Bottom line: without extensive study over generations of a given type of animal, we don't know.

Stress, pro or con? :
Life in a mud wallow. For four to six months each year this H Minax lives well outside the ideal envelope. During the rainy season it's hole is flooded about half the time. Right now, during the cold season, it is active but has only webbed over it's hole once since October.

The above chap fathered these slings.

Would the mother of those slings have been healthier if she didn't have to clean the leaves and debris out of her hole on almost a daily basis?

The answer to how stress affects the animal may not be found in any piece of literature. Only by comparative long term observation can we make informed decisions.

Is the ideal containment truly ideal? Is the life span of the animal really the best indicator for judging the best circumstances for the animal?