What Does gastropod Mean
A gastropod is a mollusk that has a foot to crawl , a head with tentacles and a body that is usually protected by a shell . These animals can be aquatic or terrestrial.
Gastropods, like all mollusks, have soft teguments and present bilateral symmetry. The ventral foot that allows its movements is fleshy and muscular. As for the head , it is cylindrical and clearly defined, exhibiting one or two pairs of sensory tentacles.
Most gastropods have a shell that winds up in a spiral. However, in some species the shell is stunted or minimized.
The snails , for example, are gastropods. These creatures, protected by a spiral shell, can be terrestrial, freshwater, or saltwater. To move around, they undulate the muscles on the bottom of their foot.
The Helix aspersa is the common garden snail , one of the best known gastropods. It is a hermaphroditic species : each specimen has female and male reproductive organs, in such a way that procreation can be carried out by any pair of these snails.
It is interesting to note that the common garden snail is consumed by humans in various Mediterranean regions, such as parts of Spain and France . As a gastronomic product, this gastropod is raised on farms through heliciculture .
Simultaneously, the snail is considered a pest that causes serious damage to crops. That is why it is tried that this gastropod is not present in the fields where activities typical of agriculture are carried out.
The oldest gastropods are known to have been marine and their appearance took place throughout the latter part of the Cambrian , during the Paleozoic Era, around 541 million years ago. The Scenella and Helcionella , two forms of gastropod belonging to the lower Cambrian, either no longer considered within this group, and the Aldanella , small and spiral, that not even included in molluscs.
In the Ordovician , 485 million years ago, there were a great variety of gastropods in more than one aquatic habitat . However, fossil remains that old are not in good enough condition for researchers to correctly identify them. This has not prevented them from describing species from the past, particularly from the Paleozoic; for example, we know of fifteen different species belonging to the genus Poleumite , dating back 444 million years.
At present there are few groups of gastropods that have been maintained since such remote times. Although those that belonged to the Carboniferous , 359 million years ago, have many characteristics in common with the current ones, almost none of them are directly related. It was only in the Mesozoic era that evolution found the ancestors of the gastropods that we know today.
Returning to the Carboniferous for a moment, the Maturipupa belonged to that time , one of the oldest terrestrial gastropods discovered so far. Snails have most of their ancestors from the Cretaceous , within the Mesozoic era, 145 million years ago. It was then that the genre called Helix emerged , mentioned in a previous paragraph.
In Mesozoic rocks it is more common to find gastropod fossils, and they have an acceptable state of conservation, both in fresh and salt water environments. Another curious fact is the many traces that can be seen in some sedimentary rocks, which are supposed to have been created by ancient gastropods when passing over sandy and muddy terrain. This claim is not supported by all scholars, but is based on the immense resemblance of these footprints to those left by current gastropods.