The three body forms of sponges are – asconoid, syconoid and leuconoid forms. Among the three, asconoid is the simplest form. Here, let’s discuss more about the asconoid sponges and their canal system.
Table of Contents
Types of Sponges
The phylum Porifera or sponges are mostly aquatic organisms whose body is composed of loosely arranged cells. These cells are of three types – mesenchyme cells, pinacocytes and choanocytes.
Sponges are radially symmetrical or asymmetrical organisms with no tissue or organs. Based on the body form, the calcareous sponges can be classified into three:
- Syconoid
- Asconoid
- Leuconoid
Ascon – Description
- The simplest and least common sponge body form is asconoid. Ascon sponges have a vase-like body. Rarely do asconoid sponges exceed a diameter of 0.039 in (1 mm).
- A modified cell called a porocyte allows water to enter the sponge.
- Ostia are the outer openings of porocytes and lead directly to a chamber called the spongocoel.
- These animals are distinguished by their distinct water circulatory system and distinctive collar cells, known as choanocytes.
- The spongocoel is lined by flagellated choanocytes or collar cells and their flagellar motions suck water into the spongocoel via the ostia.
- Water exits the asconoid sponge via the osculum which is a single big opening at the sponge’s top.
- Clathrina clathrus, Leucosolenia and Olynthus are some examples of asconoid sponges.
Let’s further explore the asconoid type of canal system in detail.
Also Check: MCQs on Sycon
Ascon Type Canal System
The asconoid canal system is the simplest of all. The spongocoel opening of the ascon is present at the summit and is enclosed by a thin wall. The thin wall is made up of mesenchyme in between the outer and inner epithelia.
The epidermis, also known as the outer or dermal epithelium, is made up of a single layer of flat cells called pinacocytes. Choanocytes make up the inner epithelium lining the spongocoel. Meanwhile, skeletal spicules and several amoebocytes embedded in the gelatinous matrix make up the mesenchyme. This thin-walled structure of the asconoid sponges is perforated by numerous microscopic apertures called ostia or incurrent pores. These pores extend from the external surface to the spongocoel.
The flagella of the choanocytes propel water through incurrent pores into the spongocoel and through the osculum, supplying food and oxygen in its path and removing metabolic waste.
Water flows through the asconoid sponges in the following order:
Water from exterior
↓
Ostia or incurrent pores
↓
Spongocoel
↓
Osculum
↓
Water out
Functions of Canal System
- The ascon sponges’ canal system aids them in excretion, respiration and reproduction.
- The water that circulates through the system of canals transports food and oxygen while removing carbon dioxide, nitrogenous waste and faeces.
- It transfers sperm from one sponge to another so that the ova can be fertilised.
This was a brief note on the asconoid sponges. For more NEET related content, visit BYJU’S.
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