Abiotic conditions rather than resource availability cues determine aerial dispersal behaviour in spiderlings of Dolomedes triton (Araneae: Pisauridae)

Many species respond to risks and benefits of dispersal that vary over the short term through condition-dependent dispersal. We used wind tunnels to investigate how abiotic factors, spiderling age, and indicators of environmental quality affect aerial dispersal behaviour of spiderlings in Dolomedes triton (Walckenaer) (Araneae: Pisauridae), a denizen of temporary habitats. More than half of all spiderlings exhibited preballooning, ballooning, or spanning behaviours. Warm temperatures (>22.5 °C) and low wind speeds (<2.0 m/second) increased aerial dispersal. Aerial dispersal behaviour increased significantly until 5 days after hatch, after which it decreased, coinciding with the onset of active hunting by spiderlings. In contrast, cues about ambient food availability (egg sac number and food limitation of the mother) and potential resource competition or risk of cannibalism (conspecific density) did not affect aerial dispersal propensity. Offspring from different females ballooned in different proportions, except at the peak of dispersal, but a female's reproductive output and propensity of her offspring to balloon were uncorrelated. Thus, it appears that spiderlings of D. triton adopt a fixed strategy of high dispersal rate under optimal abiotic conditions, rather than reducing dispersal in response to cues about local food availability or conspecific density.

Energy Efficient Sensor Configuration by Fishing Spider Inspired Mechanism

Wireless sensor networks have inherent characteristics that differ from other wireless networks. Therefore, topology configuration and routing methods in WSNs must address these characteristics. In this paper, we propose an energy efficient clustering model. This model was inspired by the behaviors and capabilities of the six-spotted fishing spider, Dolomedes triton. The suggested model performs cluster-heads selection and clustering in self-organized ways. In order to determine the cluster-heads and the cluster-members, each sensor node uses the local information and simple rules that have been inspired by the Dolomedes triton. We compared our model with a well-known cluster-based routing protocol that uses random fairness for the selection of sensor node cluster-heads. In our computational experiments, we have showed that the energy efficiency and lifetimes of our bio-inspired model exceeds those of the comparison protocol by only using simple bio-inspired mechanism. We also demonstrate our model’s good performance in terms of scalability, which is one of the important indicators of performance for self-organized wireless sensor networks.

Phenology and life-cycle regulation of the fishing spider Dolomedes triton Walckenaer (Araneae, Pisauridae) in central Alberta

Dolomedes triton Walckenaer, a widespread and common fishing spider in North America, has a semivoltine life cycle in central Alberta, Canada. Juvenile spiders hibernate twice. According to evidence from laboratory rearings and patterns in field collections, the main overwintering stages are instars 3-5 and 9-11. After the second overwintering period, large juveniles moult once or twice to reach the reproductive adult stage. Juveniles grow rapidly between May and August but during overwintering between September and April, virtually no growth (measured as maximum carapace width of individuals) was observed in field populations. Dolomedes triton has a variable number of juvenile stages, ranging from 10 to 15 in males and from 9 to 15 in females. Both overwintering phases are facultative even though most individuals overwinter twice in central Alberta: at high temperatures (24-25°C) and under long-day conditions (either 18 h light : 6 h dark or 19 h light : 5 h dark) juveniles can develop directly to adults. Short-day photoperiods did not prolong stage durations, but warm periods, when experienced late in development only, were associated with extra moults, and may thus delay maturation until the following spring. Although the second overwintering period is a quiescence regulated strictly by temperature, regulation of the first overwintering period is more complex, including probable preconditioning through interaction of temperature and photoperiod.