Difference Between Epidermis and Gastrodermis

Epidermis vs Gastrodermis

The difference between epidermis and gastrodermis can be discussed under different aspects starting from their location. Epidermis and gastrodermis are two tissue layers found in cnidarians. Since cnidarians are the simplest animals that lack any organ level organization, the epidermis and gastrodermis have a single layer of cells. Cells are differentiated into various cell types based on the location and the function. There is a gel-like, cell-free layer called mesoglea, which separates the gastrodermis from the epidermis . This body structure is unique to Cnidarians. Cnidarians belong to Phylum Cnidaria, which includes corals, Hydra, jellyfish, sea anemones and sea fans. The most characteristic features of these organisms include the presence of nematocysts, acoelomate body that lacks organ level organization, radially symmetrical body, and a simple digestive sac with only one opening (a mouth). The mouth is surrounded by a ring of tentacles that push food into the gastrovascular cavity. Cnidarians are carnivores and mainly feed on small crustaceans and fishes. All the species are exclusive aquatic, and only a few live in freshwater habitats. Having introduced the cnidarians, let’s now move on to the details of epidermis and gastrodermis and the difference between them.

What is Epidermis?

Epidermis is the outer lining of cnidarian body. Epidermis is made of a single cell layer. The cell types in the epidermis include nerve cells, sensory cells, contractile cells, and nematocysts, which are specialized to capture prey. The free-living cnidarians can move by contracting specialized cells in the epidermis.

Difference Between Epidermis and Gastrodermis


What is Gastrodermis?

Gastrodermis is the inner lining of the gastrovascular cavity. It is a single-layered tissue with gland cells and phagocytic nutritive cells. Food in the gastrovascular cavity is digested by enzymes that secretes from gland cells. The digested food is then engulfed by the nutritive cells.

Epidermis vs Gastrodermis

What is the difference between Epidermis and Gastrodermis?

• Location:

• Epidermis makes the outer layer of the cnidarian body.

• Gastrodermis lines the gastrovascular cavity of cnidarians.

• Specialized Cells Types:

• Epidermis has nematocysts, contractile cells, nerve cells, and receptor cells.

• Gastrodermis has gland cells and phagocytic nutritive cells.

• Origin:

• Epidermis originates from ectoderm.

• Gastrodermis originates from endoderm.

• Muscle Fibrils:

• There is a longitudinal muscle fibril at the basement of epidermis.

• There is a circular muscle fibril at the basement of gastrodermis.

• Function:

• Epidermis makes the outer layer of the body, supports to capture prey, and acts as a sensory cell layer.

• Gastrodermis helps in extracellular digestion of food in the gastrovascular cavity.


Images Courtesy:

  1. Jelly Fish by Luc Viatour (CC BY-SA 3.0)
  2. Anatomy of a coral polyp via Wikicommons (Public Domain)