Reproduction in animals seems pretty straightforward, but what about reproduction in other living organisms? Many living things have adaptations that allow them to reproduce without needing to find that special someone. An antheridium is one example of these adaptations.
What Is an Antheridium?
Simply put, an antheridium is a structure that produces and holds sperm cells in bryophytes (non-vascular plants) and ferns. This is similar to a human’s testes in that the sperm is not only produced in the structure, but is stored there until needed for reproduction. The antheridia (plural) make up the male structure in these mosses and ferns. The female structure is known as the archegonium, and it contains the egg cells of the organism.Take a look at the diagram below. A lot going on here, but notice the antheridia on the right and the archegonia on the left.
The sperm swim from the antheridia to the archegonia.
The antheridia of the organism will begin to open and allow the sperm to flow out. This occurs during a period when there are water droplets for the sperm to swim through. The sperm have flagella that are specialized, whiplike tails that allow the sperm to swim through the water from the antheridia to the archegonium.
Where Are Antheridia Found?
Antheridia are found in bryophytes and ferns which belong to the category cyptogams.
These represent the plants that reproduce via spores rather than through seeds and pollen. In fact, many pollen-bearing plants are evolutionary descendants of these, in that their antheridia have become pollen grains instead.Remember that bryophytes are classified as non-vascular plants; that is, plants that do not have specialized tissue for nutrient and water movement. So we put in this category things like mosses, lichen, liverworts; basically small, moist plants. Also recall from a moment ago in the lesson that the sperm cells need moisture (water) in order to swim to the egg cells, which is why we see mosses and the like in places of shade and moisture.
What Do Antheridia Do?
Plants go through what is referred to as the alteration of generations.
Without spending too much time on this, just understand that in this alteration of generations, we see two separate phases of the plant. One phase is a gametophyte phase and the other is a sporophyte phase. The main issue here is that during the sporophyte phase of the plant’s life, we see cells produced through mitosis, or cell division, that are multicellular and are diploid, meaning that they have all of the DNA of the plant in every cell.As the plant makes new gametes, it has to go through a special cell division called meiosis.
During this time, the plant produces sex cells that have half of the plant’s chromosomes, or DNA. This is referred to as a haploid, or half DNA phase. This gametophyte phase is named as such because we see the gametes forming. In the antheridia of the plant, the sperm cells are formed, whereas inside of the archegonia, the egg cells are formed. Once the haploid egg and the haploid sperm meet, they fuse, creating a diploid organism.The main purpose of an antheridium is to simply produce the male gamete, or sperm cell, for the plant during the gametophyte part of the alteration of generations. It then is supposed to store it until it’s needed.
This also allows the gametes that were formed here to stay moist, which is clearly a major point. Without the moisture it can dry out, killing the gametes. This is similar to adult men, where the testicles need to keep sperm cells at a certain temperature lest they are killed off. No sex cells equals no reproduction, which won’t allow the organism to pass on its specific chromosomes.
Let’s review what we’ve learned.
Simply put, an antheridium is a structure that produces and holds sperm cells in bryophytes (non-vascular plants) and ferns, while the female structure that produces egg cells is called the archegonium. The sperm cells move from the antheridium, using flagella, which are specialized, whiplike tails that allow the sperm to swim through the water from the antheridium to the archegonium in the plant and produce spores. This is characteristic of bryophytes and ferns, which belong to the category cyptogams. These represent the plants that reproduce via spores rather than through seeds and pollen.So, while there are certainly similarities, plants clearly reproduce differently than we do. In order to get themselves ready for reproduction, they have a feature called the alteration of generations. This is basically two phases they go through.
In the sporophyte phase, they produce cells through mitosis, or cell division, that are diploid and have all of the plant’s DNA and chromosomes. During the gametophyte phase, the plant begins to go through meiosis, in which the plant produces sex cells that have half of the plant’s chromosomes or DNA, or more simply put, the haploid phase, or half DNA phase. These are gametes and are produced and stored in the antheridium. Inside of this structure, they are stored until sufficient moisture occurs outside, allowing the antheridium to open.
The sperm stored here now can swim through the water and find the archegonia of the plant where the egg cells are stored. A haploid sperm and a haploid egg meet, resulting in a new diploid organism forming.