[Biology Class Notes] on Gemmules Pdf for EXAM

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

1. Inner layer

2. Spicule

3. Micropyle

4. Archaeocytes

5. Outer pneumatic layer

Gemmules Classification

In general, there are two categories of gemmules, and the names are:

Features of Gemmules

1. Gemmules can survive without oxygen.

2. They are the same as a bacterium’s endospore.

3. 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 app today!