Spongilla

It is a genus of sponges found in the freshwater, slow streams and lakes, belonging to the family Spongillidae. Spongilla genus sponges stick themselves to the logs and rocks and filter the water for numerous smaller aquatic organisms including bacteria, protozoans, and other free-floating pond organisms.

Spongilla genus sponges are freshwater sponges and are different from marine sponges as they get exposed to more harsh, diverse, and changing environmental conditions. For this reason, they have gemmules developed in them for dormancy.

Knowing about the gemmules, these are internal buds that are found in sponges and play an important role in asexual reproduction. An adult sponge can develop from these asexually reproduced masses of cells.

The process of the asexual reproduction performed by sponges is budding through external or internal buds (gemmules). Since the gemmules are resistant to drying out or desiccation, lack of oxygen, freezing, and can lie around for a longer time.

When conditions are favourable, the gemmules germinate and form a new sponge. Sponges also have spicules that are present on the dermal layer providing skeletal framework and protection.

Spongilla for the NEET exam is important; let’s discuss it in more detail.

Spongilla is classified under phylum Porifera and these belong to the class Demospongiae.  The common Spongilla species is Spongilla lacustris. Below is a tabular representation of the spongilla classification.

Classification of Spongilla

Examples of Spongilla

Following are some of the spongilla examples which belong to different species:

• Spongilla alba

• Spongilla arctica

• Spongilla chaohuensis

• Spongilla cenota

• Spongilla mucronata

• Spongilla mucronata

• Spongilla helvetica

• Spongilla wagneri

• Spongilla permixta

• Spongilla prespensis

• Spongilla shikaribensis

Structure of Spongilla

Let’s learn some points about the Spongilla structure from the following section:

1. Spongilla is normally yellowish brown colored, consisting of multiple small individuals having a common flat base.

2. Spongilla is a common freshwater sponge which is usually colonial and attached to sticks or wood pieces found in lakes and ponds.

3. Every Spongilla individual is perforated with numerous Ostia and one osculum (which can be one for one individual or one for many individuals).

4. Spongilla has a rhagon type of canal system and its skeleton comprises spongin fibres having silicious monaxon spicules.

5. Being delicate in structure, sponges grow as encrusting or branching masses and because of the algae that thrive on them, they appear greenish many times.

6. Spongilla may attain a volume of over 2.5 K cubic centimetres.

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Characteristics of Spongilla

In this section, we will discuss certain spongilla characteristics that help us to identify and understand their behaviour.

• Spongilla may be unbranched/branched and consist of numerous Ostia found all over the surface.

• Their colour ranges from light yellow to green and it depends upon the number of zoochlorellae living on them. Zoochlorella is a green algae having a symbiotic association with it.

• As discussed earlier, spongilla is found in slow streams, lakes, and freshwater. These get attached to logs, sticks, and submerged plants.

• Spicules which support its outer surface may be simple, tetraxial, or siliceous.

• It has a leuconoid type of canal system which is complex and a system of interconnected canals leading to irregular symmetry to Spongilla. 

• Water enters the Ostia and then to incurrent canals that open into flagellated chambers and these chambers are lined by choanocytes. Further, the flagellated chambers open into the excurrent canal and water here flows outside from the osculum.

• Extensive division and shrinkage of the spongocoel leads to the formation of excurrent canals.

• Diffusion is the process of gaseous exchange and excretion in Spongilla.

• These feed on smaller organic particles and on them, many insects depend for feeding.

• Spongilla can reproduce asexually or sexually.

• Budding is the asexual reproduction through budding or gemmules formation.

• These are hermaphrodite and each sponge can produce egg and sperm. One sponge’s sperm reaches another sponge’s Ostia and development takes place inside the cavity to produce free-swimming larvae.

A Detailed Study about Spongillas

Under the phylum Porifera of Animalia kingdom, a special type of organism called Spongilla is found. It is a genus of different kinds of species resembling sponges that we use in our daily life. This genus comes under the family of spongillidae of order spongilida and class demosponge. These are found in both freshwater  and marine environments having a leuconoid body. Siliceous spicules build the skeleton of the body and that gives the organism a slight rigid structure to hold it together. Leonard Plukenet was the first person to discover such peculiar creatures found in lakes, ponds, streams and in most steady water bodies. These mostly stay in the water bodies by attaching themselves to a base or substrate which can be rocks, floating logs or even on the ground so are famously known as sessile organisms. 

Scientists have discovered the various beneficial services they provide to nature in terms of filtering the water they live in. This is done by the specialised parts available in the spongilla such as ostia and osculum. In turn, this filtered water gets available to the various aquatic organisms and microorganisms thus maintaining the balance of diversity in that ecosystem.

For reproduction, every spongilla produces both sperm and egg in its body so are known as hermaphroditic organisms. Only eggs get released in the water and reach the body cavity of the spongilla through the gateway of ostia. Inside the body, cavity larvae develop after the fertilisation or fusion of egg and sperm.