Spiders: A Marvelously Designed Friend of Humans
The ubiquitous spiders are the unsung friends of humans. Although spiders are widely feared, very few species are dangerous to people. Spiders bite humans only in self-defense, and unless you are allergic to the venom, few spider bites cause stinging worse than a mosquito bite or even a bee-sting (Vetter, 2008). Spiders feed on our most-common indoor pests, including roaches, mosquitoes, flies, and moths. Only one type is a herbivore, the rest are carnivores. An estimated up-to-800-million tons of insect prey are annually consumed by the spider community, reducing the need for dangerous pesticides (Nyffeler and Birkhofer, 2017).
In my medical school Scanning Electron Microscopy (SEM) class, one of the creatures I examined was a spider. Its design absolutely amazed me.Spiders are the largest order of arachnids with 48,000 species that display a truly amazing variety. The smallest, the Patu digua, are smaller than a grain of sand. The largest and heaviest spiders, the tarantulas, have a body up to 90 mm (3.5 in) long and leg spans up to 250 mm (9.8 in). Their colors vary from the white Argiope to the black widow spider, and most every color in between including green to camouflage themselves. Many are multicolored. There are fishing spiders that catch insects near water, jumping spiders that jump to catch their pray, and hundreds of other kinds.
Mating season finds male spiders fighting until one gives up and the winner gets the female, which lives over twice as long as the male, up to 30 years! Males find females by picking up pheromones she uses to coat her web. After mating, the female lays her eggs on a newly spun silk sheet. Some spiders can lay as many as 2,000 eggs. When they hatch the spiderlings may chew their way out of the egg sac, which at times requires the mother’s help. Their offspring look like miniature adults most of which soon wander off to fend for themselves. Depending on the breed, some mothers feed their young with a form of milk. Others may carry their offspring around for a few days to allow them to mature before they venture out on their own.
The So-Called Primitive Spider is Actually Very Advanced
Spiders have no ears but its body is covered with hairs that can sense touch and even vibrations to the degree that they can sense a flying insect traveling in the air above them. Or it can taste by walking on various surfaces and allowing their feet to determine what is below. Its senses are so fine-tuned that it can pick up vibrations of an insect trapped in its web. It then knows it may need to wrap the prey in silk to preserve it until it is hungry. Spiders eat one or two large insects a week, more or less, depending on how much food is available and how hungry they are. If more food is available, they often eat more, if less, they adjust accordingly. Their smell and taste memory are so accurate that they can recognize their own silk which is to them easily distinguishable from that of other spiders (Brunetta and Craig, 2010).
One example of very advanced systems belonging to a so-called primitive creature is spider eyes. Most spiders have eight eyes, four pairs on the head’s top-front, arranged in patterns to enable them to concurrently see in several directions (Hamilton, 1986). Most arthropods can only detect the light’s direction by using a shadow cast on the walls of its eye cup. Arachnids are the only group of arthropods in which the main sight organs are camera-type eyes like humans, rather than simple compound eyes like most insects.
Each spider’s eye has a single lens like those of humans which are capable of forming images (Land, 1985). Their secondary eyes detect light reflected from the tapetum lucidum (a layer of cells behind the retina), which reflects visible light back to the retina, giving them superior night vision. Their tapetum lucidum also strongly plane-polarizes reflected light like polarizing sunglasses. The tapetum lucidum is what causes cats’ eyes to glow brightly when light is shone on them.
The Feared Tarantula
One of the most infamous spiders is the tarantula, a large “hairy” spider, common in horror films, but which is actually a shy creature whose bites are relatively harmless unless you are allergic to their venom (Williams and Goette, 1997, pp. 3-4). They are kept as pets, and usually only bite if they are threatened. They are very solitary animals and, like goldfish, are creatures to watch, not play with like a dog (Foelix,1982, pp. 45-46). About the only exception is during mating when they can be very aggressive (Williams and Goette, 1997).
Evolution of Spinnerets
The most well-known aspects of spiders are the incredible webs that most of them, but not all, spin. Spider silk is produced in their silk glands that open from spigots located on their spinnerets on their posterior (Donovan, 1994). Spinnerets secrete a liquid that is exuded, which then hardens on contact with the cool air. Many varieties of silk exist—the female garden-cross spider alone can produce at least seven different types of silk (Vollrath, 1992). Spider silk is as strong as steel, yet it can stretch as much as twice its length (Bishop, 2007, p. 20). It also serves as food if the spider is hungry enough.
The proteinaceous silk is effectively preserved in the fossil record—threads of spider silk Darwin-date back to mid-Tertiary, and one spider web is claimed to date from the Eocene (Codington, 1992). The fossil record traces spinnerets that Darwin-date all the way back to the Devonian and Carboniferous (Donovan, 1994, p. 211). A single web can use as much as 100 feet of silk thread, making it more likely to be preserved.
The earliest known spiders had a “nearly complete spinneret whose structure is very advanced” (Preston-Mafham, 1991, p. 13). The evolution of the spider silk glands and spinnerets necessary for making webs are explained by assuming that 180 million years ago spider silk was simply “excretory material deposited behind as the spider ran” (Kaston, 1966, p. 27). From this stage the silk evolved into a dragline, next into a trip wire and, finally, it formed a spider web. Another theory of spider-web evolution is that ancestral spiders used alpha keratin (a component of spider threads) to cover their eggs (Vollrath, 1992). Problems with both of these just-so stories include explaining how the spider survived until the spinneret and silk material formula was fully evolved, and the fact that the spinneret silk-producing organ is both irreducibly complex and an organ system separate from the anus.
Once the silk glands evolved, the brain program to produce a web must have simultaneously evolved—the silk is useless to capture food until the spider has the ability to construct a functional web, which requires a complex brain program to direct its construction (Williams, 1992, pp. 88-89). Furthermore, so-called “‘primitive’ webs are not structurally simpler or less complex than so-called ‘advanced’ webs” (Williams, 1988, p. 123).
The known evidence is that the earliest known spinnerets were fully developed, and no evidence exists of spinneret evolution—the theory that they evolved from a pair of legs, a common just-so story is not supported in the fossil record (Vollrath, 1992, p. 72). Arachnida found in amber appear very modern in all respects, even including fully-developed web threads (Poinar and Poinar, 1999, pp. 75-76).
Spiders are Evolution’s Worst Nightmare
Spiders are one of the best examples known that disprove evolution. And this is based on enormous evidence, including the almost 1,000 species that have been described from fossils (Dunlop, et al., 2008). Their tough arachnid exoskeleton aids in both preservation and identification. As a result, many spiders have been extremely well-preserved in the fossil record, especially in amber, and most are readily identifiable (Selden, and Shear, 2008). Amber has effectively preserved even those arthropods that lack tough exoskeletons.
Fossil spiders are claimed to date back to the Tertiary, and some as far back as the Upper Cretaceous or earlier, have been identified from the close to 60 different families found in only one amber type (Penny, 2002; Penney, 2001, pp. 987-1009; 2002, p. 709; Schawaller, 1983; Poinar, 2000). Evolutionists date spiders back to the time when Devonian monsters swam in the seas about 400 million Darwin-years ago. More than 200 spider species have been identified in Miocene amber from the Dominican Republic alone (Penney, 2001, p. 987).
Spiders are extraordinarily complex and well-designed for their role in helping to control the insect population. One amazing trick is, as young spiders, they can produce a long web streamer of silk which the wind catches, carrying them for a few yards or more, and sometimes as far as one hundred miles!
The large number of very ancient spiders uncovered do not document evolution, but rather stasis, meaning no change has been documented since spiders were originally created (Weygoldt, 1996). The evidence is clear, the first spider was a fully formed spider that had all of its complex equipment required to live built-in its body from the very beginning.
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