What are Gemmules Their Structure Formation and Function in Sponges
Gemmules are found in sponges, gemmules are internal buds (embryonic shoot), which plays a significant role in asexual reproduction. In other words, you can define what are gemmules as a cluster of cells capable of growing into an adult sponge.
Now that you are familiar with what are gemmules, let us proceed with what is gemmule formation?
Gemmule Formation in Sponges
Gemmule formation occurs in freshwater by several sponges like Spongilia and some water species such as sea sponges, figuline ficus, and various other types of poriferans. The organisms give out gemmules, which further give birth to new sponges.
Archaeocytes or totipotent cells are filled with food material in the form of lipoprotein or glycoprotein amalgamate to become a mass. Further, an amoebocyte moves around the archaeocyte to provide a surrounding layer. This amoebocyte releases solid chitin, which becomes a layer around archaeocytes.
Freshwater sponges usually die during the autumn season but leave behind a lot of gemmules. These produced internal buds can even withstand and live in winters and summers' adverse and unfavourable conditions. Further, these grow to become new sponges when they find an abundant quantity of water.
Structure of Gemmules
A completely formed gemmule features a standard size, and the structure of the same is similar to a hardball. Alongside reproductive cells, you can also see a food mass embedded in membranes on a grown gemmule.
Plus, gemmules have a tiny opening, which is scientifically termed as a micropyle. When the conditions are favorable for development, cells come out from this opening.
Parts of a Gemmule
Inner layer
Spicule
Micropyle
Archaeocytes
Outer pneumatic layer
Gemmules Classification
In general, there are two categories of gemmules, and the names are:
Single or double-layered coats enclosed by mono or binucleate cells
Triple-layered coats enclosed by binucleate cells
Features of Gemmules
Gemmules can survive without oxygen.
They are the same as a bacterium's endospore.
Gemmules can live in adverse conditions, where sponges may not be able to survive.
Characteristics of Gemmules
Although there isn’t much definition and structure to gemmules, they possess the following characteristics:
i. Gemmules are resistant to drying up, they are resistant to desiccation due to weather, temperature, etc.
ii. They are resistant to freezing, even in winters during the low temperatures.
iii. They are also resistant to anoxia, which means that they can survive even in extreme shortages of oxygen.
iv. They can survive and lie around for long periods of times, which means that they do not degrade, spoil, or rot.
v. Gemmules resemble the endospore of bacteria.
vi. They are composed of amoebocytes.
vii. They are surrounded by a thin layer of spicules for support and to deter the predators.
viii. These gemmules are super degrading resistant and can survive extreme environmental conditions that could even kill fully grown sponges.
ix. The gemmules only resume growing after the environment has become less hostile.
Gemmule Reproduction among Sponges
Do you know that these internal buds show resistance towards freezing and dehydration? Yes, it is true. In fact, gemmules can even live in the absence of oxygen. The exterior gemmule layer is surrounded by endospore, further surrounded by spicule, which also protects. As a result, gemmules can grow into freshwater sponges.
Do it Yourself
a) Write down the parts of a gemmule.
b) Formation of gemmule in sponges is beneficial for:
(i) Sexual reproduction
(ii) Dissemination
(iii) Parthenogenesis
(iv) Asexual reproduction
By now, you must have acquired considerable knowledge related to gemmules. Nevertheless, for more such topics, please prefer to download the Vedantu app today!
FAQs on Gemmules in Sponges and Their Role in Survival
1. What are gemmules in biology?
Gemmules are internal asexual reproductive structures formed by freshwater sponges to survive unfavorable environmental conditions. They are resistant bodies made of a mass of archaeocytes (amoeboid cells) surrounded by a tough protective coat.
- Produced mainly by freshwater sponges (e.g., Spongilla).
- Help the sponge survive drought, cold, or lack of food.
- Germinate into a new sponge when conditions become favorable.
2. What is the function of gemmules in sponges?
The main function of gemmules is to ensure survival and asexual reproduction in sponges during harsh environmental conditions.
- Act as resistant survival capsules during winter or drought.
- Protect living cells inside a thick covering.
- Develop into a new sponge through germination when conditions improve.
3. How are gemmules formed in freshwater sponges?
Gemmules are formed by the aggregation of archaeocytes that become surrounded by protective layers inside the sponge body.
- Step 1: Archaeocytes cluster together in the mesohyl.
- Step 2: A protective layer containing spongin and sometimes spicules forms around the cluster.
- Step 3: A small opening called a micropyle develops for future germination.
4. What is the structure of a gemmule?
A gemmule consists of a mass of archaeocytes enclosed within a thick protective coat and a micropyle. Its main structural components include:
- Central mass: Living archaeocytes rich in food reserves.
- Protective coat: Layers of spongin and sometimes spicules.
- Micropyle: A minute pore through which cells emerge during germination.
5. What is the difference between gemmules and buds in sponges?
The main difference between gemmules and buds is that gemmules are resistant internal structures for survival, while buds are external outgrowths for rapid asexual reproduction.
- Gemmules: Internal, thick-walled, formed during unfavorable conditions.
- Buds: External projections, formed during favorable conditions.
- Gemmules focus on survival; buds focus on colony expansion.
6. In which organisms are gemmules found?
Gemmules are found mainly in freshwater sponges belonging to the phylum Porifera.
- Common in genera like Spongilla.
- Rare or absent in most marine sponges.
- Adaptation to freshwater habitats with fluctuating conditions.
7. How do gemmules germinate?
Gemmule germination occurs when favorable conditions return, allowing archaeocytes to emerge through the micropyle and form a new sponge.
- Step 1: Environmental conditions improve (adequate water and temperature).
- Step 2: The protective coat breaks at the micropyle.
- Step 3: Archaeocytes migrate out and differentiate into various sponge cells.
8. Why are gemmules important for freshwater sponges?
Gemmules are important because they allow freshwater sponges to survive extreme conditions such as freezing or drying.
- Resist desiccation and low temperatures.
- Ensure continuity of the species.
- Enable rapid population recovery when conditions become suitable.
9. What is a micropyle in a gemmule?
The micropyle is a small opening in the gemmule wall through which archaeocytes exit during germination.
- Acts as an outlet for emerging cells.
- Remains closed during unfavorable conditions.
- Essential for the development of a new sponge.
10. Are gemmules a form of asexual reproduction?
Yes, gemmule formation is a type of asexual reproduction in sponges that produces genetically identical offspring.
- No fusion of gametes is involved.
- New individuals arise from archaeocytes.
- Ensures survival and propagation without sexual reproduction.
