Behavioural analysis of web building anomalies in the orb-weaving spiderZygiella x-notata(Araneae, Araneidae)

Abstract

Among animal constructions, spider's orb webs represent regular geometrical architecture models. Their construction is the result of successive, simple and reproducible behavioural patterns, often considered as stereotyped. It has recently been shown that spider's building behaviours vary, which can alter web regularity. The final capture spiral results from the laying of successive threads between two radii, here termed 'spiral units' . We defined a theoretical normal web, as a web in which each turn of the final spiral should be parallel to the preceding one. Weaving of the spiral units sometimes leads to anomalies in the orb web. Anomalies were identified and analysed in the orb-weaving spider Zygiella x-notata (Clerck, 1757). From video recordings of web construction, we noted the displacements of the legs and of the abdomen of the spider. We compared the frequency of displacements, and their duration, between the construction of spiral units that produce a normal turn and ones that produce an anomalous turn. The position of the legs on the web's threads was also analysed. Results showed that anomalies were not the consequences of a modification in activity but more likely the result of the position on the radii of the fourth leg. These results suggest that spiders use local information to build the final capture spiral.

Influence of aging on brain and web characteristics of an orb web spider

“…The orb web is the result of coordinated and stereotyped behaviors, and anomalies in the structure of the web result from behavioral errors during web building (Eberhard 2010, 2011; Toscani et al 2012); these behavioral errors also increase with aging (Anotaux et al 2012, 2015). In general, orb web design can vary due to environmental or internal factors (Herberstein 2011; Eberhard and Hesselberg 2012).…”

Imperfections in perfect architecture: The orb web of spiders

“…When building its web, a spider has to change frequently the orientation of the axis of its body relative to the position (vertical or horizontal) of the deposited thread. Even if we had not observed the building behaviour of spiders during the construction of the different parts of webs, we know that during the laying of the spiral units, some behavioural errors may occur (Toscani et al, 2012). By studying the building behaviour and recording the incidence of anomalies, such as two threads stuck together and non-parallel threads, this author found that these two behavioural errors were directly linked to the position of the fourth leg and of the abdomen.…”

“…On the other hand, anomalies resulting from behavioural errors (i.e. Toscani et al, 2012) such as holes, discontinuities in the spiral threads, two or more spiral units stuck together, may indicate some neural dysfunction. For example, different studies showed that several substances (i.e.…”

“…Its structure may be affected by gravity (Witt et al, , 1977Vollrath & Mohren, 1985), by drugs (Witt & Reed, 1965;Hesselberg & Vollrath, 2004) or a morphological disability (missing or a shorter leg) (Vollrath, 1987;Pasquet et al, 2011). Moreover, web characteristics vary at the intraspecific and intra-individual levels Heiling & Herberstein, 2000) and are a direct reflection of spider behaviour (Zschokke & Vollrath, 1995;Eberhard & Hesselberg, 2012;Toscani et al, 2012).…”

“…during the construction of the sticky spiral, the position of each thread depends on information perceived by the movements of the first pair of legs (L1) (Vollrath, 1987), and anomalies in web structure are associated with abnormal leg positions (Eberhard & Hesselberg, 2012). There are several descriptions of stereotyped and repetitive behaviours, which can be translated into simple algorithms (Vollrath, 1992;Vollrath et al, 1997;Krink & Vollrath, 1997), but if spiders functioned like mathematical models, webs should have a perfect geometry and should vary in structure little at all and, any web defect may be ascribable to behavioural variation during construction (Quesada et al, 2011;Eberhard & Hesselberg, 2012;Toscani et al, 2012).…”