One of the more recognizable denizens of the ocean floor are the numerous species of sea urchins. Many people recognize them instantly by their pointy spines that extend from their body, even those who know little about aquatic life. What many may not know is how sea urchins fit into the origins debate. This article will discuss the features of the sea urchin, as well as explain their relevance to the origins debate.
Sea Urchins are recognizable for their spines, but there is far more to them than that. However, the spines do provide inspiration for their phylum name, Echidnodermata. Translated literally, it means spiny skin. Sea urchins possess rounded bodies which are radially symmetric. This means you can slice them any way you want and come up with identical halves. The trademark spines, while stiff, are not immovable, and can flex with the currents. Sea urchins can also control their movements, particularly those on the sides of the ball. If a sea urchin is touched, the spines will all point towards the area of contact. The spines also flex to clean debris off of the urchin’s body. The sea urchins mouth is turned downwards into the seabed. It has five individual chewing mechanisms, referred to jointly as Aristotle’s lantern for the Greek philosopher-scientist Aristotle who discovered them. Small feathery gills project from the lower surface of the hardened body, called a test, as well, enabling the sea urchin to breathe. Also projecting from the rounded body are tiny tube feet. Similar to sea stars, sea urchins use these tube feet to pump water in and out, allowing for movement. Most urchins are small, less than two inches in diameter, though there are species that reach over a foot across.
Sea urchins reproduce using external fertilization. Gametes are produced in five separate gonads inside the urchin, the siphoned to the underside of the urchin using specialized tubes. These tubes then release the gametes into the water where they hopefully will meet gametes of the opposite type and produce baby sea urchins. After fertilization, a free-swimming planktonic larva called a blastula develops. This will develop into something called the echinopluteus, which feeds on smaller plankton by straining them from the water. The echinopluteus will develop for in some cases months before settling onto the subtrate and morphing into a miniature adult sea urchin. Some sea urchins may live as long as twenty years in the adult state, though most only live for a few years.
Sea urchins prefer algae above all other foods, though they are omnivores so they will tackle other food if it presents itself. Their diet is varied, as they will happily feast on nudibranchs, brittle stars, sponges and other, slow moving or non-motile invertebrates. However, sea urchins lack of speed makes them easy prey for creatures as diverse as sea otters, triggerfish, and wolf eels, which are particularly fond of sea urchins. While the spines do provide some defense, sea urchin predators are often equipped to handle them.
Sea urchins do raise some issues for the evolutionists. The first is the water vascular system that operates the tube feet. Tube feet are necessary for the urchin to live. Recall that sea urchins generally dine on algae. Algae is fixed in place and does not come to the urchin. The sea urchin must actively seek its meals, meaning the tube feet are a necessity. To operate the tube feet, the water vascular system is necessary. This is not illustrative of a gradual process since all these elements need to be in place simultaneously.
A second issue is the behavior of one species of sea urchin, Psammechinus miliaris. Known commonly as the short spined sea urchin uses its tube feet to hold up seaweed, or a shell as a sort of shield from the sun. This kind of intelligent behavior is what humans do with their hands when the sun is too bright for their eyes. The problem is sea urchins do not even have a brain. Yet it somehow can figure out how to use an object to shield itself from the sun. Evolution has no explanation for that kind of intelligent behavior. Since learned behavior is not passed through genes, the information must have been locked into the genetic code from the beginning of the code.
A third issue comes from the use of the spines as a cleaning tool. As noted above, sea urchins use their spines to clean their bodies of detrius. Where did they learn to do this? How did they develop this instinct? Since, as established above and my article on Instincts, learned behavior does not pass through the genes, it must have been hardwired into the code. This, however, does not explain this behaviors origin.
Special creation has no such issues with sea urchins. God made them to function exactly how we observe them to fuction. Their instincts were built in from the beginning and, since they were formed at once, not gradually, tube feet present no problem for a designer.