Content Writer-SME | Updated On - Jun 24, 2024
The small asexual reproductive structures found in sponges & poriferans are called gemmules. Gemmule formation takes place as a result of asexual reproduction. The appearance of gemmules are like small internal buds that play a significant role in reproduction in sponges.
- In sponges, the process of asexual reproduction either takes place through budding or gemmule formation.
- The production of gemmule is initiated by the aggregation of ameboid cells around the achaeocytes.
- The process of gemmule formation ocuurs in freshwater & marine sponges, hydra, planaria, and ficulina ficus.
What is Gemmule?
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An asexually formed group of cells that later develops into an adult sponge or organism is called gemmule. These are bud like cells which are capable of tolerating extreme temperature & environmental conditions.
- These gemmules are hard and coated with a cluster of embryonic cells.
- In sponges, asexual reproduction usually takes place through budding and gemmulation.
Formation of Gemmules
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Gemmule is created by few genus of fresh sponges like Spongilla and a few marine species of Ficulina genus, ocean sponges, and different poriferans. Gemmule Formation starts with the aggregation of ameboid cell in sponges. These cells are further surrounded by protein coating of spicules and collagen.
Gemmule formation in sponges
- During gemmule formation, archaeocytes filled with food materials in the form of conjugated protiens become organized into a single mass of cells.
- Associated amoebocyte (motile part) moves and surrounds the central mass of archaeocytes and starts to secrete thick solid polysaccharide around archaeocytes.
- Meanwhile, the scleretic oblasts starts secreting amphidisc spicules in between the inner and external membranes.
- These spicules futher protect the gemmules from the extreme weather conditions.
- The freshwater sponges survive till the autumn season, after that they die leaving a large mass of gemmules.
- These gemmules remain active in both winter and summer seasons, enduring adverse environmental conditions.
- They can withstand harsh and humid temperatures.
Structure of Gemmules
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The gemmule appears like small ball-like structure which is surrounded by spicule and collagen proteins. Structure of the gemmule resembles internal buds (embryonic shoot) in the sponges, that plays a major role in reproduction. These buds helps in the development of an adult sponge.
Classification of Gemmule Formation
The classification of gemmule formation is done on the basis of composition and structure:
- Based on Structure:
Formation of gemmules based on the structure can be of two types: Simple gemmules and Complex gemmules. In simple gemmules, the main structure is composed of a protective coating around the cells and spicules. On the other hand, complex gemmules are composed of some specialized structures such as internal canals and extra protein layers.
- Based on Composition:
The presence or absence of calcium carbonate spicules categorizes the gemmule into calcified and non-calcified gemmules.
Gemmule Diagram
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The internal structure of gemmules are divided into following parts and are shown in figure given below
- Inner Membrane,
- Spicule,
- Micropyle,
- Archaeocytes,
- Outer Membrane
Figure: Gemmule Formation in Spongilla
Characteristics of Gemmules
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Following are some basic characteristics of gemmules-
- They are resistant to desiccation which occurs due to weather, temperature, etc.
- They are resistant to any physical change such as hypoxia, which suggests their succesful survival rate in absence of oxygen.
- A thin layer of spicules are present around the gemmules which protect them from their predators.
- They are also composed of generative cells called archaeocytes.
- The covering of scleroprotein around the archeocytes acts as a shielding layer by protecting them from stressful conditions.
Features of Gemmules
Gemmule formation is usually a common mode of reproduction among sponges. There are few reasons behind the prevalence of gemmule formation over other mode of reproduction among sponges as a viable mode of reproduction. Some of them are:
- Gemmules being a small bud like structure can easily survive in anaerobic (without oxygen) conditions.
- The structure of gemmules resembles the structure of bacterium endospore.
- They can survive in the adverse conditions where the survival of sponges is difficult.
Things to Remember
- Gemmule formation is a final outcome of asexual reproduction in sponges.
- Gemmules are small internal bud like structure which has the potential to survive in harsh and humid conditions
- They are present inside the songes and remain dormant in unfavourable conditions.
- Once they get suitable environment, gemmules become active and tproduce new organism.
- The process of gemmule formaltion is a characteristic feature of marine species like sponges and poriferas.
Sample Questions
Ques. What are Gemmules? Write the example of Gemmules. (1 mark)
Ans. A generative bud made by freshwater and a few marine sponges that contain a typically hardened mixture of cells. Spongilla lacustris is the best example of Gemmules.
Ques. What are the features of Gemmules? (2 marks)
Ans. There are basically 3 main features of Gemmules-
- Gemmule can live without Oxygen.
- They have the similar property as bacterium’s endospore.
- Gemmules can survive in adverse conditions also.
Ques. Which organisms favours the process of budding? (1 mark)
Ans. Organisms like hydra use regenerative cells for replication within the method of budding. In hydra, a bud develops as an outgrowth because of recurrent organic processes at one specific website. These buds transform small people and, once absolutely mature, detach from the parent body and become new freelance people.
Ques. What are the triggering factors for sponges to produce Gemmules? (1 mark)
Ans. When favourable conditions come, the gemmules germinate and give rise to new organisms. Production of gemmules is triggered by environmental factors like optimum temperature or desiccation and involves cell aggregation of thesocytes and also the parturition down of the gemmule coat.
Ques. Why do sponges produce Gemmules? (1 mark)
Ans. Gemmules are internal buds found in sponges that have a significant role in reproduction. It is asociated with asexually reproduced mass of cells which is capable of developing into a brand-new organism i.e., associate adult sponge.
Ques. What is the shape of complete Gemmules? Write about parts of gemmule. (2 mark)
Ans. A complete formed gemmule has a normal size with hardball like appearance. A gemmule is made up of micropyle, spicule, inner layer, outer pneumatic layer, and archaeocytes.
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