Thursday, August 25, 2011

The Lowdown on Legs

One of the best things about choosing invertebrates as my blog topic is that I’ll never run out of subject matter! But that also makes it challenging to pick what to write about now. So, today’s topic is legs.

Legs are one of the main characteristics scientists use to separate invertebrates into various groups. For example, all insects, without exception, have 6 legs. Spiders always have 8. Centipedes (the name means “100 feet”) have one pair of legs per body segment and millipedes (name means “1000 feet”) have two pairs of legs per segment. The number of legs found on crustaceans such as crabs and lobsters tends to vary, but usually they have 10 or 12.

All the invertebrates mentioned above are placed in the Phylum Arthropoda, which means “jointed appendages.” Despite having no internal skeleton, arthropods have movable, jointed legs somewhat similar to our own. Below is a link to a diagram of some insect legs and how they compare to human legs.

Arthropod legs are adapted for many different functions, in the diagram. Many insects’ hearing organs, known as tympanum, are found on the first pair of legs. These organs are sensitive to vibrations and are especially useful to insects that “sing” such as cicadas, crickets, and katydids.

I may post on this topic again as I learn more about insect anatomy in my general entomology class. It’s an area I’m looking forward to understanding better!

Wednesday, August 17, 2011

The Incredible Invertebrates

On planet Earth, 99% of all animals are invertebrates. These unique animals find themselves with the challenge of surviving without the bony support system we often take for granted. Now, I mean no disrespect to the faithful backbone. I myself am very grateful for my bony vertebrae.  But we as humans are part of the vertebrate minority. Bodies without backbones far outnumber us, and so in the Animal Kingdom, it seems backbones are somewhat overrated.

So what are some examples of invertebrates? The term covers a wide variety of organisms. Because invertebrates are animals, they meet several key classification requirements. All animals are multicellular, have a plasma membrane around their cells, reproduce sexually (many reproduce asexually as well), and are heterotrophic (they must consume other organisms for sustenance). Invertebrate animals include sponges, jellyfish, flatworms, roundworms, earthworms, centipedes, millipedes, crustaceans (crabs, lobsters, etc), mollusks (octopi, snails, clams, etc), spiders, scorpions, and insects. There are also dozens of less well-known and rather bizarre invertebrate groups.

Now while I find all invertebrates fascinating, I am particularly intrigued by insects. They are the most numerous animals on the planet. They exhibit an astounding variety of body plans, colors, and sizes. Insects have exploited every major ecosystem and are found on every continent (including Antarctica!). They can cause devastation and disease, but are also vital to our survival. Pollinators such as bees allow us to enjoy many varieties of fruits and vegetables. Many insects are predators of the pests that can wreak havoc on our agricultural system. Insects exhibit many fascinating behaviors seen nowhere else in the Animal Kingdom, yet they are often overlooked because of their size and alien (sometimes even scary!) appearance.

The purpose of my blog is to explore the amazing world of insects on a weekly basis. I also plan to highlight some other interesting invertebrates as well. My hope is to educate, inspire, and maybe even change a few minds regarding insects. But even if I never do persuade you to touch or even look at an insect, I hope you will gain a greater appreciation and respect for these remarkable six-legged creatures. And perhaps you may find yourself contemplating the overratedness of backbones.