Question

Mesoglea of sponges consists of
a. Gelatinous matrix
b. Fibers
c. Spicules
d. All of the above

Answer 1

Sponges are aquatic, invertebrate animals from the phylum Porifera. Sponges are the simplest multicellular organisms, they are classified by their primitive cellular-level of organization, their porous bodies, and filter-feeding system. Sponges have specialized cells that carry out distinct functions within the organism.

Complete answer:
- Sponges have specialized cells that can carry out distinct functions; they do not have organs or true tissues. This is called a cellular-level organization.
- Sponge consists of a body wall consisting of two layers, outer layer pinacoderm, and inner layer choanoderm, with non-cellular mesenchyme in between.
- Mesenchyme is also known as mesoglea. It is the interconnecting proteinaceous gelatinous matrix.
- Amoebocytes such as archaeocytes, myocytes, chromocytes, thymocytes, etc. are found moving in between the layers.
- Mesoglea is composed of collagen fibers, spicules, and many other types of cells.
- The mesoglea is a layer of jelly-like material between the ectoderm and endoderm cellular layers of the body of a sponge or cnidarian.
- It consists of collagen-like fibers and mucopolysaccharides. In sponges, it contains many motile cells.
- Mesoglea is found between the two epithelial cell layers in the bodies of cnidarians and sponges and are translucent, non-living, jelly-like substances.
- Mesoglea refers to the tissue found in jellyfish and it functions as a hydro-static skeleton.
- It resembles a type of connective tissue and contains several amoeboid cells such as amebocytes, as well as fibrils and skeletal elements.
- The collagen, fibronectin-like molecules, galectin, and dermatopontin are the composition of mesoglea.
- These polypeptides form an extracellular matrix and they provide the platform for cell adhesion and signal transduction and cellular growth.
- Sponges are divided into classes based on the composition of their spicules and skeletal fibers. Spicules are rod-shaped cellular projections and make up the skeleton of sponges.
- Skeletal spicules made up of calcium carbonate are a feature of Calcarea.
- Hexactinellida is called glass sponges because their skeletons consist of spicules made of silica.
- Spicules made up of silica and skeletal fibers made from spongin, a type of collagen protein is a feature of Desmospongia. They are the most abundant class of sponges alive today.
- Hence mesoglea of sponges consists of Gelatinous matrix, Fibers, Spicules.

So, the correct answer is option (D).

Note: - Sponges are species in Phylum Porifera, they are the simple multicellular organisms
- Sponges are sessile and they do not carry photosynthesis.
- They have specialized cells to carry out distinct functions in the cells.
- They are divided into three classes based on their spicules and skeletal fibers.