Monthly Archives: February 2013

Arachnids: Amblypygids

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Arachnids.

Yes, arachnids; our eight-legged “friends” that cling to the shadowy, forgotten corners of our homes, under the damp seal of a rock, to the harsh, hot crust of the desert, and to their feathery webs, crafted overnight in our gardens. Arachnids, as a group, are not at all unfamiliar to us humans, and while, overall, the relationship between ourselves and these ubiquitous invertebrates is a bit complex, by and large in Western culture, arachnids are feared and reviled. The most familiar groups of arachnids, spiders, scorpions, ticks, and mites, have earned reputations as some of the most terror-inducing, retch-provoking, and spine-shuddering animals we encounter in our day-to-day lives. We cringe at the thought of ticks embedded in our skin, face first, bodies inflating into pulsating balloons of blood. We attempt to ignore the unsettling fact that millions of microscopic mites graze on our dead skin cells, both separated from our bodies and still attached. We regard scorpions, prehistoric beasts made of plates, claws, stingers, and venom, as symbolic of the uninhabitable desert wilderness.

And then, of course, there are the oh-so common spiders, creatures who receive reactions from humans ranging from praise for their beautiful, radial web architecture, to mild annoyance when encountering a surprise face and mouthful of this same web on a forest trail, to revulsion and a swift, life-ending blow with a shoe or newspaper (turning the hapless critter into a drab smear of entrails), to blinding, full-on arachnophobic panic. These last group of arachnids, in particular, are the animal kingdom’s ‘black sheep’ in our culture, becoming a fixture in our conceptualization of the spooky atmosphere of Halloween; curiously, along with bats, spiders are among the few living, non-fictional entities we set alongside the stereotypical ghoulish folklore characters like zombies, skeletons, witches, and sundry other monsters. Apparently, we consider spiders among the creepiest, darkest, and most unnerving of all living things.Those that fear spiders, and creepy-crawly arachnids in general, cite these creatures’ long, spindly limbs, soul-less eyes, hairy bodies, venomous fangs, fast movements, and a tendency to inhabit abandoned, abyssal areas where we are already at unease, as some the reasoning behind their prejudice. This instinctual aversion is strong enough, and prevalent enough, to inspire scores of films and literature where spiders are featured as agents of terror. Seriously. There are plenty. Of examples. Our overwhelmingly negative view of spiders, especially, obscures some of their talents, many of which are immensely useful to humans. These include the production of a silk that is tougher than Kevlar (which has instigated research into super-strong materials), and an inarguably critical ecological role that keeps populations of their prey items (insects) in check. Spiders, like most arachnids, in the immortal words of Rodney Dangerfield, “get no respect.”

Oh jeez. Are you guys happy now?

In the same way that spiders and other more familiar arachnids are misunderstood and have unrecognized, underappreciated roles in our lives, the very definition and realization of what arachnids, in the broadest sense, actually are typically is met with limited experience and knowledge. For example, most people, if prompted to “name an arachnid” would answer firstly (overwhelmingly so) with ‘spider.’ Some might follow up with ‘scorpion’, or perhaps ticks and mites…pretty much everything with eight legs and without insect-like antennae that comes to mind. However, the diversity of arachnids extends far beyond the web-bound orb weaver bobbing in the breeze in your front yard’s hedges, or the chigger causing lovely, itchy welts to form on your skin. While these groups are the most speciose, and most common accompaniment to our daily lives (good or bad), there are entire taxonomic orders of arachnids that go quite completely, and miserably, ignored.

This entry is to serve as the first in a series of explorations into the less-loved (or, perhaps, less-persecuted, simply out of unfamiliarity) arachnids.

But first, perhaps it is helpful to start with the following question: what is an arachnid, exactly?

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Evolutionary Anachronisms

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The avocado.

You may think you have a good relationship with the avocado. The buttery fruit of this plant may regularly accompany your turkey sandwich, sliced and fanned out across the bread. Or, it may serve as a hearty dip in the form of guacamole. More recently, avocado is seemingly being utilized in a greater variety of ways, being deep-fried, thrown in macaroni and cheese, and finding its way onto burgers, Subway sandwiches, and even into ice cream. You’d expect that with all this attention, our green-fleshed, knobby-skinned friend, the avocado, would be content with its current role in human culinary efforts.

However, the avocado may very well be lonely.

Despite all our affection, this loneliness stems from the avocado potentially having eyes for another. I mean this, of course, in the sense of the concept of co-evolution (which I examined in a previous post), which is directly tied to the reproductive role of the fruit itself. The main function of a fruit (a botanical fruit, typically meaning the structure derived from the reproductive tissues of the flower housing the seed(s)), is to move seeds away from the parent plant and into areas that promote growth and survival. Many types of adaptations in fruits exist to help achieve this goal of seed dispersal; from the wind-catching dual blades of maple tree fruits (known as samara), to exploiting the appetites of the ubiquitous (and notably mobile) animals in the neighborhood. This latter evolutionary strategy involves the development of fruits that enrapture animal taste buds and provide irresistible caloric value, allowing consumed seeds to travel safely inside the gut of an unwitting, far-traveling chauffeur until being excreted away from the crippling shade of the parent plant. This is called “endozoochory.”

Most endozoochorous fruits have evolved to be eaten by fairly specific animals. Predictably, fruits adapted to be taken by songbirds are going to have different physical attributes than those associated with insects or elephants. You can try and fit a peach pit through the body of a sparrow, but you aren’t going to get very far. Similarly, expecting tiny, thin-walled seeds to withstand an elephant’s battery of grinding teeth isn’t realistic either. The suite of fruit traits evolved for dispersal by a given group of animals roughly categorize into “seed dispersal syndromes.” By interpreting these syndromes, we can often get a good idea of what the primary dispersing animal, the other partner in a co-evolved relationship, is likely to be.

In light of this, it becomes obvious that despite our love of the avocado (specifically, domesticated cultivars with lots of flesh; wild avocado fruits have a thinner layer of green deliciousness surrounding that pit), it is not “meant” for human consumption and seed dispersal. Any attempt to chew up the whole fruit and swallow the massive pit is bound to land your asphyxiating ass in the cemetery. However, the situation for avocado’s seed dispersal isn’t much better in its wild Neotropical range. Many smaller animals (like monkeys) that partake in avocado consumption are “pulp thieves”, ingesting the oily layer and tossing the seed at the base of the parent tree. In fact, no native animal is known to consistently and effectively disperse wild avocado. Why then does the avocado make a big, energetically expensive fruit that doesn’t cut the mustard on dispersal? Also, who is the true “buyer” of avocado’s product?

The answer to both those questions may be that the avocado’s chief dispersal agent is extinct. Kaput. Gone. Effectively an “ex-animal.” This would mean that the avocado fruit is an evolutionary anachronism, equipped with traits fine-tuned by evolution for interaction with a species that has quite suddenly disappeared, leaving the once perfectly capable seed vessel under-appreciated and inadequately used.

“Fruit’s almost ripe, guys. Come and get it! Hello? ….Guys?!”

It’s a very serious case of being all dressed up with nowhere to go.

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