Some think that places such as this are slippery, smelly or, worst yet, dirty. I agree with the first, for marine macrophytic algae produce quantities of mucus to, in part, mitigate the effects of desiccation and temperature extremes. But surely tide pools are neither smelly nor dirty. When the tide is out, these places provide refugia for algae and animals with little or no capacity to withstand the rigors of exposure to the air. They provide windows of opportunity to commune with a rich community of invertebrates that live in the marine inter-tidal. One can see crabs (and a variety of other crustaceans), periwinkles, whelks, chitons, mussels, urchins, starfish, brittle stars, anemones, hydroids, sponges, bryozoa, and even tunicates, going about the business of finding food and make more of their own. I have admired tide pools since I was a kid. I will admire them always. I will explore them as long as I am able to negotiate the slippery substrates they present.
I first thought of Wiwaxia. But, it could not be. Although Wiwaxia and this animal are approximately the same size, the former lived nearly 500 million years ago and paleontologists have not yet been able to determine whether it was an Annelid or a Mollusc. This animal is surely an Arthropod, the caterpillar of Acronicta americana, the American Dagger Moth.
A decayed Birch had given way and toppled into the water. I recovered what I could and a chainsaw worked the remainder. As I collected the shorts, I noticed that one bore the graze marks of a snail. Many gastropods use a toothed rasp to gather food. Grazing is highly ordered and elaborate patterns may accumulate on appropriate substrate. Look closely at any one of approximately fifty arcs of activity. More than a dozen feeding strokes are taken to the left, the animal moves forward, and as many strokes are then taken to the right. The behavior is reminiscent of what a cow might do on pasture … munch, munch, munch to the left, a step or two forward, and munch, munch, munch to the right.
Opportunities to use the word aposematism do not present themselves often. Today, however, it is warranted because Monarchs provide a textbook example of the phenomenon of warning coloration. The bold stripes are a clear signal to predators to stay away. And, for good reason. The primary food of this instar is Milkweed, a plant which contains cardiac glycosides, compounds which are highly toxic. The pharmacodynamics of glycosides, especially the cardenolide steroids, are widely known. Digitalis or digoxin, perhaps the best known of these compounds, is derived from Foxglove. In humans, the compound increases the force of heart muscle contraction and reduces heart rate. It has been used, clinically, as an antiarrhythmic. Such agents are therapeutic at low doses and can be lethal at higher ones.
Arion subfuscus is common and may be found when conditions are wet and, especially, in the early morning. Slugs are snails. Like other gastropod molluscs they have a shell but theirs is carried internally and has been reduced to just a sliver. Like other land snails, Arion has a pneumostome which allows air to reach the lung. In this image you can see a hint of this feature if you look a third the way down the right side of the mantle (the oval structure which leads from the base of the optic tentacles). I think this is a very pretty animal indeed.
I don’t like beer, but I do remember the classic Budweiser tagline, This Bud’s for You.
Well … This Post’s for Me.
The long tentacles are for vision, the short ones are for olfaction. Members of the group respire in air. The pore, the pneumostome, allows respiratory gasses to reach the lung. Succinids live in wet, terrestrial, habitat.