Phylum Ctenophora Overview

Ctenophora is a phylum of marine animals with transparent, gelatinous bodies, often called comb jellies or sea walnuts. They are free-swimming or planktonic and resemble coelenterates.

Ctenophores are recognized as a separate group because of their unique features, including comb plates for movement, the absence of stinging cells (nematocysts), and a different embryonic development.

Ctenophores are commonly found in marine environments, especially in warmer waters. They are usually planktonic, floating in surface waters, although some species live in deeper depths.

Ctenophores move rhythmically using comb plates, which are rows of cilia that beat in a coordinated fashion. This creates a wave-like motion that propels them through the water.

Ctenophores are carnivores that feed on plankton, including eggs and larvae of various marine animals. They capture prey with their tentacles, which trail behind their bodies.

Many Ctenophores show a beautiful display of colors when sunlight refracts off their vibrating comb plates. Additionally, they often exhibit bioluminescence, emitting light from their meridional canals.

Ctenophores play a significant role in the marine food web as predators of plankton. They help control populations of various organisms and contribute to energy transfer within the ecosystem.

Ctenophores are typically spherical, pear-shaped, or cylindrical, resembling a gooseberry or sea walnut.

Ctenophores possess biradial symmetry, meaning their body parts are arranged radially around a central axis, with two planes of symmetry.

Most ctenophores are moderate in size, ranging from a few millimeters to 20 cm, but some species can reach over a meter long.

Ctenophores are usually transparent, but some structures, like tentacles and comb rows, can have shades of white, orange, or purple.

Ctenophores have 8 rows of comb-plates (ctenes), which are bands of fused cilia that act like paddles for swimming.

Another name for ctenophores, referring to the roughened ridges formed by the rows of comb-plates.

Ctenophores have two long, retractable tentacles with branches or pinnae, used for capturing prey.

A deep pouch where the tentacles can be retracted for protection or concealment.

Lasso cells, also called colloblasts, are specialized adhesive cells found on the tentacles of ctenophores. They are unique to these organisms and replace the nematocysts (stinging cells) found in cnidarians.

Colloblasts have a spring-like filament coiled around a stiff filament. When prey touches the colloblast, the springy filament shoots out, entangling the prey. The head of the colloblast also secretes glue to further secure the prey.

The statocyst is a sensory organ found in ctenophores. It's located at the aboral end of the animal and helps the ctenophore maintain its balance and orientation.

The statolith is a small, rounded mass of calcium carbonate particles found within the statocyst. It acts as a weight that helps the ctenophore sense changes in orientation.

The statolith rests on four tufts of cilia called balancers. When the ctenophore tilts, the statolith presses more heavily on one side. This sends signals via ciliated furrows to the comb plates, causing them to beat faster and right the animal.

Comb plates are rows of fused cilia that run along the body of a ctenophore. They beat rhythmically, creating a wave-like motion that propels the animal through the water.

Ctenophores are distinct from coelenterates (like jellyfish) in several ways. They lack stinging cells (nematocysts), have comb plates for movement, and their embryonic development differs. But they share a common ancestor, as shown by the presence of nematocysts in one ctenophore, Euchlora rubra.

Yes, ctenophores are triploblastic animals. Their bodies have three embryonic germ layers: ectoderm, mesoderm, and endoderm, which give rise to different tissues and organs.