Ben's Blog Items Credenda|agenda: things to be believed, things to be done http://www.credenda.org/index.php/Table/Wonder/ Tue, 23 May 2017 18:36:13 +0000 Joomla! 1.5 - Open Source Content Management en-gb Cone Snails and Their Paralyzing Harpoons http://www.credenda.org/index.php/Wonder/cone-snails-and-their-paralyzing-harpoons.html http://www.credenda.org/index.php/Wonder/cone-snails-and-their-paralyzing-harpoons.html Beautiful, slow, and graceful, cone snails creep over the sands, rocks, and coral reefs of the tropical seas. The over 500 species in the genus Conus come in many sizes (small to half a cubit long) and sport a diverse array of colors and patterns (modest to ostentatious), yet they all share a very similar gestalt.  Their elegant beauty is loved by shell collectors worldwide. Although a cone snail’s empty shell may be a nice touch to the décor of a beach cottage, these little mollusks are not a nice touch when alive.

Cones are deceptively dangerous and highly effective predators. When hunting they protrude a long flexible proboscis out of their mouth. This wormlike extension can be maneuvered toward a hapless fish pausing nearby.  In Conus geographus the proboscis is brightly colored and is used as a lure to attract fish. Loaded within the proboscis is a tiny, hollow, barbed harpoon-like dart, called a radular tooth.  The dart is loaded into the ‘muzzle’ of the proboscis from the radular sac (a kind of quiver holding several other darts in various stages of development). When the snail strikes certain muscles quickly thrust the business end of the dart into the prey.

An internal bulb gland propels venom through the poison duct which leads to the mouth cavity and up through the hollow harpoon. When the dart penetrates, this complex cocktail of toxins is injected into the fish (or other prey). In species that feed on fish and worms, the harpoon is tethered to the snail so it is of paramount importance that the venom paralyzes quickly so that the snail is not dragged unceremoniously over a coral reef by its panicked prey.  The retrievable dart is then ‘reeled in’ pulling the paralyzed prey with it.  The snail’s mouth widens and engulfs the prey whole.  After it has digested its meal, the indigestible bits are regurgitated out of the mouth.

The venom is composed of about 200 different compounds. The mixture and quantity of the components differ from species to species thus the toxicity also varies ranging from bee sting intensity to paralyzing death. These so-called conotoxins are neurotoxins that target and quickly shut down the nervous system thus putting a quick stop to the struggles of fast swimming prey.  Smaller cones tend to hunt marine worms and other mollusks but the larger species hunt fish.  Since the latter can be deadly to humans, beachcombers, snorkelers, and scuba divers beware.

So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, ………... And God saw that it was good. Genesis 1:21

Here is the sea, great and wide,
which teems with creatures innumerable,
living things both small and great.
Psalms 104:25

Watch.

]]>
gwilson@nsa.edu (Gordon Wilson) Wonder Wed, 23 Jun 2010 16:42:00 +0000
Head Rush http://www.credenda.org/index.php/Wonder/head-rush.html http://www.credenda.org/index.php/Wonder/head-rush.html We all look at house flies with considerable distain. This is largely due to their disgusting habit of greedily landing on various forms of filth for dinner, and then not having the good sense to wipe their feet before they land on ours. But despite their unhygienic habits they are a marvel of divine engineering.  Let me take you on a short Tilt-a-Whirl ride and introduce you to one weird wonder of life in Lilliput.  House flies belong to a group called the Schizophora. This includes the flesh flies, Tsetse flies, stable flies, botflies, and blowflies (blue and green bottles).  They all share an anatomical feature of a curved seam situated between their two large compound eyes (on their forehead). This crack marks the spot where the door of their face once closed.  “When was this door opened?” you might ask.  I’m glad you did.  Don’t buckle the seat belt of your credulity.  Believe me, it’s true. I’m a Christian and I wouldn’t tell you falsehoods.

We all know that house flies begin life with more disgusting looks and habits than when they grow up. They don’t just visit squalor; they’re immersed in it. During these juvenile and adolescent weeks we called them maggots, a disgusting name to match their nursery. These pallid writhing worms consume their share of the earth’s refuse.  As they do, they grow and go through several molts (sheddings) and finally begin metamorphosis. During metamorphosis the fly is within a little brown sausage-shaped container.  This dry leathery casing is formed from the skin of the fully grown maggot when it shed to become the pupa. This cocoon-like bag, called the puparium now houses the pupa. Another transformation occurs. The innards of the pupa liquefy and an adult body forms within the pupal skin (This is starting to look like Russian dolls).  There is an adult body inside the pupal skin which is inside the maggot skin. Now the fun begins. When the adult is ready to immerge it easily slips out of the pupal skin but it requires a lot more oomph to break out of the more protective puparium. Almost like it was planned (ha!), the maggot skin (a.k.a. puparium) has a circular seam forming a pop-off lid at the end where the adult is to immerge.  It doesn’t actually say “tear here” because flies don’t need directions to open containers like we do. Even though it is pre-weakened, a simple nudge won’t budge it. To make its grand appearance, muscles in the fly’s abdomen contract forcefully shoving blood to its head. This is a head rush of dramatic proportions. The trapdoor on the fly’s face pops open under the pressure and a balloon-like thing called a ptilinum (the p is silent) inflates and billows out of its forehead. This blood bag pushes against the lid of the puparium, popping it open. Like Houdini, the fly immerges triumphant from both its pupal and maggot skin. The bag deflates and is withdrawn into its noggin. Its face closes back up never to open again. The exoskeleton of the fly stiffens to the right firmness and then it flies away. It’s in a hurry to carry out its God-given job of waste management.

]]>
gwilson@nsa.edu (Gordon Wilson) Wonder Fri, 07 May 2010 23:52:11 +0000