The key difference between pinacoderm and choanoderm is that pinacoderm is an external skin or outermost epithelial layer composed of pinacocytes, which are plate-like cells. In contrast, choanoderm is the innermost body layer or inner surface composed of choanocytes, which are flagellated cells.
Sponges are simple invertebrates belonging to Phylum Porifera. They are sessile metazoans characterized as multicellular immobile animals. Also, there are approximately 5,000 living sponge species, and they possess a unique feeding system. They draw water through the tiny pores in their body walls. Therefore, they have bodies full of pores and channels, allowing water to circulate through them. They maintain a constant water flow and rely on it to obtain their food. Body of the sponge is hollow and contains different cell types including two main types: pinacocytes, choanocytes. Pinacocytes form the external skin called pinacoderm while choanocytes form the inner surface called choanoderm.
CONTENTS
1. Overview and Key Difference
2. What is Pinacoderm
3. What is Choanoderm
4. Similarities Between Pinacoderm and Choanoderm
5. Side by Side Comparison – Pinacoderm vs Choanoderm in Tabular Form
6. Summary
What is Pinacoderm?
Pinacoderm is the outermost cell layer of the body of sponges. It is composed of plate-like or flattened cells called pinacocytes. Pinacoderm is equivalent to the epidermis of other animals. Therefore, it acts as the external skin or surface of the sponge body. Pinacocytes do not have flagella. They are arranged in a single layer.
Figure 01: Sponge
Similar to other cells, pinacocytes also digest food particles. Structurally, pinacocytes are very thin and broad cells which are nucleated. They form a squamous sheet. In sponges, there exist six different types of pinacocytes; they are the exopinacocytes, endopinacocytes, basopinacocytes, prosopinacocytes, and apopinacocytes.
What is Choanoderm?
Choanoderm is the innermost epithelial-like cell layer of sponges. It acts as the inner surface or gastral epidermis. Choanoderm is composed of flagellated collar cells called choanocytes. Similar to pinacoderm, choanoderms are also a single-celled layer. There are foldings in the choanoderm, which allow the formation of spherical chambers. Choanocytes line these chambers.
Figure 02: Choanocytes
Choanocytes are used to drive their water flow systems and capture most of their food. These cells capture food particles by their basal surface and by the apical area near the collar.
What are the Similarities Between Pinacoderm and Choanoderm?
- Pinacoderm and choanoderm are two types of epithelial-like layers of sponges.
- They have nucleated cells.
- Both cell layers are involved in the feeding system of sponges.
What is the Difference Between Pinacoderm and Choanoderm?
Pinacoderm and choanoderm are two epithelial-like surfaces of sponges. Pinacoderm is the external skin of sponges, while choanoderm is the innermost surface of the sponges. So, this is the key difference between pinacoderm and choanoderm. Also, pinacocytes form the pinacoderm, while choanocytes form the choanoderm.
Moreover, pinacocytes are flattened cells without flagella, while choanocytes are flagellated collar cells. Besides these, the functional difference between pinacoderm and choanoderm is that the pinacoderm lines the external surface of the sponge, while the choanoderm lines the internal surface of sponges.
Summary – Pinacoderm vs Choanoderm
Pinacoderm is an epithelial layer of flattened cells called pinacocytes. It is the outer cell layer or external skin of sponges. In contrast, choanoderm is the inner cell layer composed of specialized flagellated cells called choanocytes. Therefore, pinacoderm is the dermal epidermis while choanoderm is the gastral epidermis of sponges. Therefore, this is the key difference between pinacoderm and choanoderm. Both pinacocytes and choanocytes are involved in drawing water into them and supporting the feeding system.
Reference:
“Pinacoderm.” Pinacoderm – an Overview | ScienceDirect Topics, Available here.
“Choanoderm.” Wikipedia, Wikimedia Foundation, 8 Oct. 2014, Available here.
Image Courtesy:
1. “Aplysina archeri (Stove-pipe Sponge-pink variation)” By Nhobgood (talk) Nick Hobgood – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Grantia Choanocytes large g” By Circa24 – Own work (CC BY-SA 3.0) via Commons Wikimedia