Walking along the beach it is easy to observe shells of clams, mussels, cockles or truffles with a small perfectly circular holeready to be threaded to create a summer necklace. One of us might rightly ask: “But who made that hole?”. We find the answer by studying the behavior of some molluscs. In fact, the authors of the “little holes” on some types of shells are Predatory molluscs highly specialized. Different species of Molluscs carnivores adopt this ingenious strategy for to feed oneself: they drill a hole in the shell of the prey to reach the body and feed on it. Drilling techniques vary depending on the predator. By analyzing the size and shape of the hole, you can trace the perpetrator, a bit like what happens with the “murder weapon”. More specifically:
- a single circular holewith a diameter of approximately 0.3 to 8 mm, located in an area very close to the tip of the shell, called umbois the work of Gastropods predators of the Naticidi family or of the fMuricide family. These Molluscs block the prey and then begin to perforate the calcium carbonate shell. The process is both chemical, through the emission of corrosive enzymes, and mechanical with the use of clearinga portion of the mouthparts equipped with a sort of small teeth suitable for scraping and consuming shells. The operation is rather laborious and time-consuming; once the hole is completed, the animal inserts its mouthparts and feeds on the soft parts of the prey, enjoying a very nutritious meal.
- multiple and small diameter holesbetween 0.1 and 2 mm approximately, are instead practiced by a very different and more evolved Mollusc, the Cephalopod Common octopus (Common Octopus). The octopus pierces the shell only to inject a deadly toxin into the body of its prey and, generally, the perforation occurs right in the area corresponding to the liver gland of the victim who dies within a few minutes.Octopus he then proceeds to extract the mollusc directly from the natural opening of the shell and not from the hole.
Such strategies should not be surprising considering that Molluscs have particularly high adaptability capacities, have colonised the most diverse environments, both aquatic and terrestrial, and represent one of the largest animal groups after Arthropods, counting approximately 130,000 living species.
