15 examples of PORIFERS (or sponges)

When we talk about animals, we all get an idea of ​​animals that move (with greater or lesser speed) to search food and perform its various functions, but this is not so in the case of porifers, one of the phyla of animals plus curious and primitive that exist. In this lesson from a TEACHER we will see examples of poriferous and its characteristics. Are you going to miss it? We started!

Index

1. What animals belong to the poriferous group?
2. What are the characteristics of porifers?
3. How do poriferous animals or sponges feed?
4. Poriferous respiration
5. Reproduction of porifers
6. Types of porifers according to their channel systems
7. Examples of porifers

Before presenting Poriferous Examples, it is important that we know what they are.The edge of Poriferaor poriferous is an edge of Invertebrate animals between 5,000 and 10,000 species known and commonly known as sponges.

It is one of the edges of more primitive animals and whose main characteristic is to have a body full of

Poriferous are aquatic animals, mostly marine, although there are freshwater ones, and they inhabit highly variable depths, ranging from the coast to approximately the 9000 meters deep. Unlike other animals, the organisms that make up this phylum are sessile, that is, they lack mobility.

The poriferous they are animals of radial symmetryThat is, they have a body divided by a heteropolar axis, as if it were a star, and they do not have differentiated tissues or organs. To the not have a circulatory or respiratory system as such, the water enters through the pores and flows through their cavities, thanks to the irregular shapes that their bodies adapt. There are some sponges that have a kind of internal skeleton made up of a fibrous (collagen-like) protein called spongy and they may have calcium carbonate spicules.

The body of the poriferous is composed of two layers of cells separated by a space. Its outer layer is called pinacoderm and is made up of cells similar to mammalian epithelial cells called pinacocytes. It is in this layer where the pores of the poriferous surface are formed.

Each of these pores is lined by a special tube-shaped cylindrical cell called porocyte, and that it possesses the ability to contract and relax to open and close. Its inner layer called coanoderm, is made up of flagellated cells called choanocytes and whose flagellar movement is responsible for generating the water currents that pass through the animal. Between both layers is a space called mesohilo and that it has cells with support, food or reproductive functions.

Poriferous cells

Although these invertebrates do not have differentiated tissues, they do have different cells that are responsible for different animal functions.

Thus to the pinacocytes, porocytes or choanocytes, we must add the basopinacocytes that help to fix the sponge to the substrate, the colenocytes that produce collagen and secrete it to mesohilo, sclerocytes that produce the spicules of calcium carbonate, myocytes that serve for contraction, spongiocytes producers of spongin protein, spherulous cells with secretory functions or amoebocytes, which are stem cells of the other cell types.

As we said, in poriferous all the functions related to feeding are carried out thanks to the water flow that enters through the pores and passes through all the cavities, capturing the food particles that are in the water.

Since some of these particles are too large to enter through the pores, are phagocytosed by pinacocytes and digested inside. The smallest particles that do pass through the pores, and which account for up to 80% of the sponge's nutrition, are captured and digested by the choanocytes.

However, there are some exceptions to the general type of nutrition of porifers, since there are sponges that are carnivorous and that live feeding on small animals such as crustaceans and others. In some other cases, there are porifers that are capable of living as endosymbionts inside from other organisms such as green algae or cyanobacteria, through which they obtain matter nutritious.

Image: Aprenderly.com

As in the case of feeding sponges, respiration is carried out thanks to the flow of water by its cavities.

Poriferous respiration occurs by direct diffusion of oxygen dissolved in the water into their cells and, in the same way, carbon dioxide. Carbon and ammonia generated by the animal is eliminated following the reverse path, that is, from the cells to the water that flows through its body.

Sponges or porifers can reproduce both in a sexual What asexual. Regarding its asexual reproduction, three methods used are known:

• Fragmentation: This method of asexual reproduction occurs when a fragment separates from the body of the animal. After a while, this fragment manages to regenerate the missing parts of the animal and become a functional sponge.
• External buds: in this reproductive method, buds are formed which, upon reaching a certain size, detach from the organism that originated them and float to originate a new sponge, or they remain attached to the rest of the body.
• Internal buds or gemmules: this form of reproduction usually occurs in freshwater sponges and in some marine ones. In it, the archaeocytes gather in solid masses in the mesohyle and are surrounded by spongy and siliceous spicules. When the parent dies, the gemmules survive and remain dormant during times of frost or drought. The gemmules then come out through a special opening to make room for the new sponges.

Refering to sexual reproduction of porifers, most of the sponges are hermaphrodites. Sponges do not have gonads, but male gametes or sperm are formed from choanocytes and female gametes or ovules are formed from archeocytes. Normally, the sexual reproduction of porifers is a cross-fertilization, that is, between different individuals.

The process begins when sperm from an individual are expelled with the water and penetrate through the pores of another individual, where they transform and reach the mesohilo to meet the ovules. The fertilized eggs are retained inside the new organism, until they hatch and are expelled in the form of cilia or flagella.

According to their canalicular systems, sponges can be:

Asconoids

Sponges in this group possess the simplest degree of organization. In them, the water enters through microscopic dermal pores called ostioli, due to the churning of the flagella of the choanocytes, which line the internal cavity forming a space called spongocele. Subsequently, the water leaves the body of the sponge for a kiss. This system has the limitation that some foods are inaccessible to choanocytes. Some of the species of this asconoids are Leucosolenia, inhabiting shallow waters with a body anchored to a spur, or Clathrina. The asconoid species are only found in the class Calcárea.

Siconoids

The syconoid species are a more advanced group of sponges than the asconoids. They have a tubular body, a single osculum, and a thicker wall covering the spongocele than in asconoids. Its body folds into more cavities. The flow of water in the sycon is greater and has greater dimensions. An example of a syconic organization is gender Sycon. Syconic sponges are found in the calcareous class and some are in the hexactinellid class.

Leuconoids

The leuconoid sponges are the most complex and best adapted to increase the size of the sponge. They have a large number of flagellated chambers and folds, so the flow of water through their body is very efficient. Their shapes can also be very varied, there are elongated, branched or tubular bodies. Most sponges are of the leuconoid type and an example is the genus Leuconia.

Here we present you the examples of poriferous plants. Within this edge we distinguish four classes and three of them include species that are still alive, as one of them became extinct during the Cambrian period. The other classes are the class Calcarea, Hexactinellida and Demospongiae.

Class Calcáreas or calciesponjas

The sponges that they have a calcareous skeleton, that is, they have calcium carbonate spicules. Its spicules are usually straight and its body is tubular or vessel-shaped. They are generally small sponges, 10 cm or less in height, and may have an asconoid, siphonoid, or leuconoid structure. Although they tend to have muted colors, some are bright red, yellow, or green like Lleucosolenia and Sycon. These sponges tend to live in shallower depths than others such as, for example, Clathrina coriacea, that lives in Mediterranean waters.

Class Hexactinellida, hyalosponges or vitreous sponges

This is another of the examples of poriferous that you should know. Sponges of this class usually inhabit deeper areas fixed to the substrate by stems of root spicules. They have a body of radiated symmetry normally shaped like a funnel or vessel. They reach sizes ranging from 7.5 cm to one and a half meters and are characterized by having siliceous spicules that are generally grouped in a reticular structure with a vitreous appearance. An example of a sponge of this class is known as the Philippine watering can (Euplectella aspergillum).

Sponge Class

This class includes 95% of current species and larger sponges. It also has some siliceous spicules, which may or may not be linked by spongy, and a Leuconoid body, being able to live at any depth. The so-called Spongia and Hippospongia bath sponges (formerly used in the bath) belong to this class. Another member of this class is the genus Thenea, which is quite peculiar, since it has the shape of a mushroom.

And with this, we end this lesson on poriferous examples so that you can better know this type of animal so curious and unique in the world.

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Hickman, C. P. (2009). Comprehensive principles of zoology (14a. ed. --.). Madrid: McGraw-Hill.