"The lessons for the spider is not for the fly"
Henri Michaux - Poet (1899-1984)
Oh Aging! Oh, all functional changes gradually diminishing our abilities! How to understand yourself? How to study yourself? How to better tame yourself?
These are questions that many people ask themselves. Most people want to live long, healthy, and have a fully capable life. But is it possible? All the creams or even dietary supplements do not seem to fight time. With the global aging of populations, it is more than urgent to understand aging in order to make it as peaceful as possible. But how?
What if the answer was to study spider webs?
A spider's web consists of rays and a capture spiral formed by a succession of silk thread segments joined together by successive rays. The whole, forms a regular geometrical structure, the realization of which is achieved by a complex succession of stereotyped behaviors repeated over time. Changes in the structure of the web, in the absence of external factors, can then be likened to direct reflections of the spider's behavioral changes.
What if a spider could serve as an experimental model for studying aging? This is what Mylène Anotaux proposes in her thesis entitled "Studying a behavioral model of aging: web construction in an Orb-weaver spider."
The subject is brought up gradually by the author who follows a simple and effective narrative thread. The introduction allows us to understand the set of issues raised with logic as well as to discover the subject of aging and the use of model organisms in research.
The proposed method is interesting as well as innovative and is sure to change the reader's view of spider webs forever. The discussion elaborates on all of the author's observations by putting them in perspective with the literature in a fluid and coherent manner. It enables the readers to grasp the significance, interest, and possible perspectives of the proposed research work.
The Razor's Edge
"Aging is a natural, obligatory and irreversible phenomenon, often associated with a decline in body performance and function. Although behaviors tell us about the physiological and neurological state of the body, very few studies have focused on the relationship between age and behaviors. The search for new models to understand this relationship could therefore be of prime importance. In orbital spiders, the web is a complex geometric structure of apparent regularity. Its construction results from a succession of organized and repeated behaviors and each variation in the web structure can be interpreted as a behavioral variation of the spider during construction.
The objective of this study was to highlight structural variations in the web geometry of the spider Zygiella x-notata that could be correlated with spider aging and to find out how aging acted on the spider's mobility during its construction and when capturing prey.
Our results show that aging affected the web geometrical characteristics, construction behavior and capture behavior of the spider. Our study validated the relevance of using orbiting spiders and their geometric webs as innovative models to study the relationship between aging and behavior."
As We Age
Mylène Anotaux captured a number of relevant results during her thesis. One of them is the influence of aging on the structure of the spider web. This result is a direct extension of previous studies on the evolution of web structure with age.
From the juvenile to the adult stage, it is shown that the number of spirals, rays, as well as the spacing between spirals increases. In this transition, the web becomes asymmetric due to an extension of the lower part. The size and weight of the spider increase between these stages, so does the amount of silk invested in the webs, leading to an increase in web size. These web evolutions occur without observing or noting any significant variation in apparent regularity.
But What Happens as the Spider Ages?
The author seems to show that the variation in the structure of the spider's web is a consequence of the effect of aging on the behavior that the spider adopts in its construction. Thus, we discover that after adulthood, the quantity of silk that the spider invests in its web decreases; its regularity of construction is lost; and it makes more and more mistakes. The frequency of these irregularities tends to increase with age and seems to correspond to a form of "normal" aging in these spiders.
By comparing different species, the author shows that the increase in the number of structural anomalies in the web seems to concern older spiders belonging to a species with a short life span.
These structural variations in the web could be the consequence of a decrease in the production capacity, quality, or even the recycling capacity of the silk necessary for its realization. The spider would then adapt to these phenomena by adjusting its web design plan.
When Our Lives Hang by a Thread
The subject of this thesis may seem a little confusing at first. But by following the narrative thread finely woven by Mylène Anotaux, we can fully understand the meaning of her work. Aging is an unavoidable phenomenon, often associated with a decline in performance and function of the organism leading to a decrease in well-being and autonomy. Few organizations allow us to study the evolution of behaviors during aging. Mylène Anotaux proposes a model that allows us to study the physiological and neurological state as well as the behavioral changes associated with age.
We do not weave webs yet and we do not have eight legs, but we now know that it may be relevant to take a closer look at the webs of orbital spiders to better understand what lies ahead for all of us...
And you, then, what shape does your web take?
Thesis presented and defended on December 14, 2012. Work carried out at the Unité de Recherches Animal et Fonctionnalités des Produits Animaux (URAFPA) within the doctoral school Biology-Health-Environment (BioSE) : ED 266 (University of Lorraine) (Nancy and Metz).
Mylène Anotaux. Étude d'un modèle comportemental du vieillissement : la construction de la toile chez une araignée orbitèle
Médecine humaine et pathologie. Université de Lorraine, 2012. Français. ⟨NNT: 2012LORR0309⟩. ⟨tel-01749655⟩
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