What is it that so attracts us to animals?  Is it animal magnetism?  Some animals do have magnetic senses that can guide them across oceans.  The more we learn about animals, the more we should admire their high-tech equipment.  Here are some recent examples of amazing animals, some of them suitable for Halloween decorations.

Eensy weensy wonder spider:  After cockroaches, spiders are the second most vibration-sensitive creatures, reported PhysOrg.  Researchers at the University of Vienna used scanning white light interferometry and micro-force measurements to measure the strain sensors on a species of wandering spider that detects vibrations on leaves to detect prey.  Strain sensors?  Yes.  Here’s how they work: “Team member Friedrich G. Barth explained that the spider has over 3,000 strain sensors in its body, mostly on the legs and in vibration receptors located near the leg joints,” the article said.  “Each strain sensor comprises a series of arrays of tiny parallel slits in the compound lyriform [lyre-shaped] slit sense organs that detect vibrations and movements. When forces are applied the slits are compressed and stimulated.”  And that’s not all: spiders can see in the dark and sense odors on their antennae.  Remember that when you see spider decorations for Halloween.

Giant spider webs:  Some spiders can cross rivers with their giant webs.  The species Caerostris darwini, endemic to Madagascar, builds “the largest known orb webs utilizing the toughest known silk.”  PLoS ONE reported findings of a team who studied the web-building activity of these spiders that were just discovered last year (9/24/2010).  The webs of C. darwini are made of silk combining strength and great elasticity such that it outperforms all other known spider silks, and even most synthetic fibers, in terms of toughness (work required to fracture the silk),” the researchers said; “Furthermore, capture areas of C. darwini webs regularly exceed 1 m in diameter and are suspended on bridge lines that often exceed 10 meters, while the largest capture areas reach almost 2 meters in diameter and are suspended on bridge lines up to 25 meters in length.”  The team wanted to know how the spiders manage to bridge such large distances, and whether the silk toughness co-evolved with this ability.  They watched 32 spiders in action.  The spider starts by spinning a “bridging silk” that consists of several strands that catch the wind then recombine within 24 seconds into a line that gets tangled in vegetation across the stream.  The spider then “reels in” the bridging line, from which it can travel out and start constructing its large orb web above the water.  It drops a vertical line in the center, forming a T structure, from which it creates diagonals up to the bridge line, resulting in a triangular web.  Within hours, the web is complete.  Curious readers may wish to visit the open-source paper for details how the spiders build their world-record webs.  The authors could not do more than speculate on how their specific adaptations evolved.  Citation: Gregorič M, Agnarsson I, Blackledge TA, Kuntner M, 2011. How Did the Spider Cross the River? Behavioral Adaptations for River-Bridging Webs in Caerostris darwini (Araneae: Araneidae). PLoS ONE 6(10): e26847. doi:10.1371/journal.pone.0026847….

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