Difference Between Sponges and Cnidarians

海绵s vs Cnidarians

One interesting difference between sponges and cnidarians is that sponges lack tissue while cnidarians have tissues but not the organ systems. Sponges and Cnidarians are very primitiveacoelomic无脊椎动物with very simple body structures. Both organisms are found in aquatic ecosystems. Sponges and Cnidarians have no organ systems. In this article, we will see the specific features of sponges and cnidarians and, from that, we will deduce the differences between sponges and cnidarians.

What are Sponges?

海绵s areaquatic animalswith a simple hollow asymmetrical bodyand categorized underPhylumPorifera。Phylum Porifera includes about 7000 identified species. Some examples for sponges include barrel sponges, boring sponges, basket sponges, bath sponges, etc. Most species are marine and very few live infreshwater。Adults aresessileand have anasymmetrical bodies。海绵体由两层组成。外部扁平的细胞层和内部鞭毛细胞系，可向其内部空腔打开。在这两个细胞层之间，有一个凝胶状细胞外基质。在大多数海绵中，这个矩阵分泌fibrous proteinthat acts like anexoskeleton。Unlike other animals, sponges haveintracellular digestion。海绵sfeed onplanktonsby filtering water. Sponges arehermaphrodites。Theirspermsare released into the water and eggs are stored in their body. Thelarva是自由生活和流动性的。人类从海中收获海绵，用于沐浴和清洁。

What are Cnidarians?

Cnidarians construct the life’s largest construction known ascoralreefs. Cnidarians (门cnidaria) includejellyfish, sea anemones,corals,Hydra, and sea fans. There are about 10,000 species found in this phylum. The key characteristic features of cnidarians includeradial symmetry,acoelomatebody with tissues, lack of organs, and the simple digestive sac that opens through a mouth, which is surrounded bytentaclesarmed withnematocysts。

All cnidarians arecarnivoresand have very simple body structures adapted aspredators。Most of them live in marine ecosystems, and very few species live in freshwater. Cnidarians have no reproductive, digestive, circulatory, or excretory systems. Moreover, they have a very primitive nerve net with nerve receptors, which are sensitive to touch, gravity and light. The only unique feature of cnidarians is the presence of nematocysts, a specialized cell for capturing their prey and for defense.

What is the difference between Sponges and Cnidarians?

•门：

• Sponges belong to Phylum Porifera.

• Cnidarians belong to Phylum Cnidaria.

• Characteristic Feature:

• Sponges have intracellular digestion and lack tissues.

• Cnidarians have nematocysts.

• Food:

• Sponges capture planktons by filtering water through their cells.

• Cnidarians are predators and feed on small fish, krill, etc.

• Presence of Tissues:

• Sponges lack tissues.

• Cnidarians have tissues but no organ systems.

• Body Symmetry:

• Most sponges have asymmetrical bodies.

• Cnidarians have radially symmetrical bodies.

• Cell Types:

• Sponges have few types of cells.

• Cnidarians have a wider range of cell types.

• Species Diversity:

• There are about 7000 species of sponges.

• There are about 10,000 species of sponges.

Images Courtesy:

1. 海绵byGéry PARENT(CC BY-SA 4.0)
2. Cnidarians通过Wikicommons（公共领域）