Click on an image below to discover more about the amazing wildlife in our area.
The shore is an excellent place to consider evolution; the concept of an organism changing to fit the environment. There are two misunderstandings though in what Darwin actually discovered.The first is that things change with some form of intention, that nature has some sense of purpose. The second is that evolution is for the benefit of the species, it is a long-term survival strategy. The Celtic sea slug is a good example. These are intertidal semi-marine molluscs, so they must live on the shore, they are grazers and so must live on a rock (sand does not support enough food). They hibernate in the winter and are very localised (neither adult or young free swim) so they need shelter in winter and cannot cope with being washed away by waves. All of these aspects involve physical adaptations to cope (evolution). A special tongue that resists being worn down when licking rocks, chemical use and sensors to enable slime trails to be left and followed back home and mechanisms to cope with very low metabolic rates in winter. These are all positive traits that make it fit the environment, so it has found a niche away from the marine molluscs and terrestrial cousins and adapted to it. Nature in all its glory etc.
The truth is slightly different, we start with a sense of purpose. Studies have suggested the animal loses the ability to grip in cold conditions, the slime it uses becomes less tactile in the cold. Marine molluscs do not seem to have this problem so opting for hibernation to avoid being washed away in winter is more a lazy strategy than a clever one. Winter storms batter rocks and observations have proven this to be devastating. If a hibernating niche is exposed the entire colony is destroyed. In a marine mollusc, this is not a problem as swimming larvae or free-roaming adults will move in from elsewhere, or those that survive the damage move. This home-loving nature is clearly not a good mechanism and the other species of molluscs have made other more successful choices. So either the Celtic is a little bit naive in the choices it makes or physical change is formed by a less intentional mechanism; chance. To benefit the species would require a strategy that enabled individuals to freely roam or at the least to have free-swimming larvae. It is probable that an entire cove could become devoid of Celtic slugs after a bad winter and that a stretch of wave-battered coast over many years, especially if the rocks are soft. So how did it evolve into what might become a dead-end strategy? Mobility in the winter is energy demanding and the food is reduced due to falling photosynthetic activity. Animals that could go longer without food would have more chance of getting through winter. If this was a genetic trait then it is likely more offspring would then have this ability, they, in turn, would reproduce more etc. This would become a competitive advantage. The animal would already naturally hide when not feeding due to predation risk (behavioural not a physical adaptation) so it was already out of the pounding waves not being washed away when asleep. So an extra sticky Celtic would not have had an advantage over his colleagues it might even be detrimental if it slowed it down.
Full hibernation would have been a chance adaptation with each generation slightly better equipped (more sleepy) than the last. The incremental change in generations would be tiny but having a small energy advantage might have meant reaching breeding condition earlier and so the trait dominates. Falling asleep while the Atlantic batters down your door though isn’t the smartest thing to do, is it? Evolution cannot be proactively engineered, it simply is the element of fate at play.