Are choanoflagellates closely related to sponges?
Choanoflagellates are among the closest living single-celled relatives of metazoans. This relationship means that choanoflagellates are to metazoans — all animals, from sponges to flatworms to chordates — what chimpanzees are to humans.
What are choanoflagellates and sponges?
Choanoflagellates are single-celled aquatic flagellates with a unique morphology consisting of a cell with a single flagellum surrounded by a “collar” of microvilli. They have long interested evolutionary biologists because of their striking resemblance to the collared cells (choanocytes) of sponges.
How are choanoflagellates similar to the choanocytes of sponges in terms of morphology?
This similarity suggests that sponges and choanoflagellates are closely related and likely share common ancestry. The body of the choanocyte is embedded in mesohyl and contains all the organelles required for normal cell function.
What is the difference between choanocytes and choanoflagellates?
Thus, both choanocytes and colonial choanoflagellates are typified by high-amoeboid cell activity. We also observed some ultrastructural differences between choanocytes and choanoflagellates. In contrast with cells from choanoflagellate rosettes, sponge choanocytes lack filopodia and intercellular bridges.
How are choanoflagellates and sponges similar?
Choanoflagellate cells have a whip-like flagellum surrounded by a basket-like structure that they use to capture and eat bacteria floating in sea water. Interestingly, these cells look and function very similar to feeding cells of sponges, one of the earliest-branching groups of animals.
What makes choanoflagellates unique?
Choanoflagellates are capable of both asexual and sexual reproduction. They have a distinctive cell morphology characterized by an ovoid or spherical cell body 3–10 µm in diameter with a single apical flagellum surrounded by a collar of 30–40 microvilli (see figure).
What do Pinacocytes do in sponges?
Function. Pinacocytes are part of the epithelium in sponges. They play a role in movement (contracting and stretching), cell adhesion, signaling, phagocytosis, and polarity. Pinacocytes are filled with mesohyl which is a gel like substance that helps maintain the shape and structure of the sponge.
How are sponges and Choanoflagellates similar?
Sponge choanocytes also have a flagellum and possess a collar of filaments for trapping food. These similarities indicate that the unicellular ancestor of animals probably had a flagellum and a collar, and may have been much like a choanoflagellate.
Did sponges evolve from Choanoflagellates?
Sponges evolved thus from a craspedid-like stem choanoflagellate.
What is the role of choanoflagellates?
The choanoflagellates feed on bacteria and link otherwise inaccessible forms of carbon to organisms higher in the trophic chain. Even today they are important in the carbon cycle and microbial food web. There is some evidence that choanoflagellates feast on viruses as well.
What is the Pinacocytes function?