Content
- What are molluscs? Types and Examples
- Reproduction of molluscs
- Examples of reproduction of molluscs
- Reproduction of molluscs: common snail (Helix asperse)
- Reproduction of molluscs: oysters
THE mollusc reproduction it is as diverse as the different types of molluscs that exist. Reproductive strategies change according to the type of environment in which they live, whether they are terrestrial or aquatic animals, although they all reproduce sexually.
In this PeritoAnimal article, we'll explain in detail how is the reproduction of molluscs, but first let's explain what molluscs really are, some of their characteristics and important details about their reproductive system. Likewise, we will detail two examples of reproduction in molluscs according to species.
What are molluscs? Types and Examples
Molluscs form a large phylum of invertebrate animals, almost as numerous as arthropods. There is a wide variety of molluscs, but they all share certain characteristics that bring them together, although each has its own adaptations. These features we mentioned are included in the divisions of your body, categorized under four regions:
- One cephalic zone, where the sensory organs and the brain are concentrated.
- One locomotive foot too muscular to crawl. This foot is modified in some groups, such as the cephalopods, whose foot evolved into tentacles.
- A posterior zone where we find the paleal cavity, where the olfactory organs, the gills (in the molluscs of aquatic life) and the bodily orifices such as the anus are located.
- Lastly, the cloak. It is the dorsal surface of the body, which secretes protective structures such as spikes, shells and venom.
Inside of types of shellfish, there are some lesser-known classes, such as the Caudofoveata class or the Solenogastrea class. These molluscs are characterized by having worm shape and the body protected by spikes.
Some molluscs have a very primitive morphology, as is the case of molluscs belonging to the classes Monoplacophora and Polyplacophora. These animals have a muscular foot, like snails, and their body is protected by a single shell, in the case of monoplacophoras, or by several, in the case of Polyplacophoras. The animals in the first group look like clams with a single valve, and those in the second look like a very famous arthropod, the armadillo.
Other types of molluscs are the prey shells, which, as the name suggests, have all their body protected by a shell in the shape of an elephant's tusk. These animals belong to the Scahopoda class, and are exclusively marine.
The best known types of molluscs are: bivalves such as clams, oysters and mussels; gastropods such as snails and slugs; and, finally, the cephalopods, which are the octopus, sepia, squid and nautilus.
If you want to get deeper into the world of shellfish, don't miss our article on types of shellfish.
Reproduction of molluscs
In such a heterogeneous group of animals that, in addition, can live in very different habitats, the mollusc reproduction it is also quite distinct and evolved differently depending on the type of mollusk.
The molluscs reproduce through the sexual reproduction, that is, within each species there are unisexual individuals, female or male molluscs. However, some species are hermaphrodites and although most cannot self-fertilize (because they need the presence of another individual), certain species do, as is the case with some terrestrial snails.
The vast majority of mollusc species are aquatic and, in this environment, the main type of fertilization is external. Only some species have internal fertilization, as is the case with cephalopods. Therefore, aquatic molluscs have external fertilization. Both females and males release their gametes into the environment, they fertilize, develop, hatch and live as free larvae until reaching the adult stage, which in some species is practically sessile or crawling, and in others, is free-swimmers.
Terrestrial molluscs, which are lung gastropods or terrestrial snails, have a more developed reproductive system. Each individual has both sexes, but can only act as one at the time of intercourse. The male introduces sperm through the penis into the female, in which the eggs will be fertilized. Then the female will lay the fertilized eggs buried in the ground, where they will develop.
Examples of reproduction of molluscs
The large number of different species of molluscs complicates the synthesis of the explanation about their r.shellfish production, therefore, we are going to explain the two most representative examples of mollusc reproduction:
Reproduction of molluscs: common snail (Helix asperse)
When two snails reach adulthood, they are ready to perform the reproduction of snails. Previously, before intercourse, both snails court each other. This procession consists of a series of circular movements, frictions and hormonal release, which can last up to 12 hours.
When the snails are very close, what we know as "dart of love". These structures are true hormone-impregnated darts that cross the snail's skin and favor reproductive success. After the dart, one of the snails takes the penis from its genital pore and comes into contact with the partner's pore, enough so that he can deposit sperm.
After a few days, the fertilized animal will introduce its cephalic area into the moist soil and lay its eggs in a small nest. After a while, a hundred snails miniature will emerge from that nest.
Reproduction of molluscs: oysters
Generally, when the warm season arrives and the ocean waters exceed 24 ºC, the breeding season for oysters arrives. These animals release into the water some pheromones that show their reproductive status. When this occurs, both female and male oysters release millions of gametes that will be fertilized outside of their bodies.
Egg development is remarkably fast and within just a few hours they enter the larval stage. A few weeks later, they fall to a rocky bottom, often guided by the chemical signals from other adult oysters. these larvae join the substrate using a cement that they create and will spend the rest of their lives there.
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