Phylum Ctenophora Overview

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Questions and Answers

What are ctenophores commonly referred to as due to their appearance?

Comb-jellies or sea-walnuts.

Who was the first to provide a definite description of ctenophores?

Martens in 1671.

In which habitats are ctenophores most commonly found?

They are mostly found in warm seas but can also be present in temperate and arctic regions.

What feeding mechanism do ctenophores employ to capture their prey?

They use trailing tentacles to capture food that comes in contact with them. Signup and view all the answers

Describe the locomotion of ctenophores in the water.

Ctenophores are feeble swimmers propelled by the rhythmic wave-like movements of their paddle plates. Signup and view all the answers

What distinguishes ctenophores from coelenterates in terms of classification history?

Ctenophores were recognized as a distinct group in classification by Eschscholtz between 1829-1833. Signup and view all the answers

How do ctenophores display their colors in sunlight?

Their vibrating comb-plates refract light, creating a series of rapidly changing colors. Signup and view all the answers

What characteristic feature allows ctenophores to produce light?

They produce light in the walls of their meridional canals. Signup and view all the answers

What shapes are commonly associated with ctenophores?

Ctenophores are typically spherical, pear-shaped, or cylindrical. Signup and view all the answers

Describe the symmetry observed in ctenophores.

Ctenophores exhibit biradial symmetry, with structures arranged radially around a median oral-aboral axis. Signup and view all the answers

What is the size range of most ctenophores?

Most ctenophores range in size from a few millimeters to 20 cm, with some species of Cestum reaching up to 1 meter. Signup and view all the answers

Explain the purpose of the comb-plates in ctenophores.

Comb-plates, or ctenes, help ctenophores swim by providing propulsion through coordinated movements of the cilia. Signup and view all the answers

What distinguishes the tentacles of ctenophores?

Ctenophores have two long, retractile tentacles with a row of short branches called pinnae. Signup and view all the answers

How do ctenophores typically appear in terms of color?

Ctenophores are generally transparent, with some structures like tentacles and comb-rows exhibiting tints of white, orange, or purple. Signup and view all the answers

What feature gives ctenophores their common name 'comb-jellies'?

Ctenophores are commonly called comb-jellies due to their comb-plates that resemble the teeth of a comb. Signup and view all the answers

Characterize the structural arrangement of a ctenophore’s body.

The body's structures are arranged tetramerously in a radial fashion around the oral-aboral axis. Signup and view all the answers

What are colloblasts and how do they function in ctenophores?

Colloblasts are specialized adhesive cells in ctenophores that secrete a sticky material to entangle small organisms, which are then brought to the mouth for consumption. Signup and view all the answers

Describe the structure of a colloblast.

A colloblast has a hemispherical head connected to a central mesenchymal core by a straight filament, with an elastic spiral filament coiled around it. Signup and view all the answers

What is the function of the statocyst in ctenophores?

The statocyst acts as an organ of equilibrium, helping the ctenophore maintain its orientation by responding to changes in body position. Signup and view all the answers

What happens to the ciliated furrows in the statocyst if one is severed?

If a ciliary furrow is severed, the beating of the corresponding comb rows becomes independent and no longer coordinates with the others. Signup and view all the answers

Explain the evolutionary significance of colloblasts and nematocysts in ctenophores.

Colloblasts in ctenophores and nematocysts in related organisms suggest a common evolutionary origin, with ctenophores possessing modified structures for prey capture. Signup and view all the answers

How does the structure of the epidermis in ctenophores vary among species?

The epidermis in ctenophores is typically made of cuboid or columnar cells, and it is syncytial in some forms, indicating variations among species. Signup and view all the answers

What role do the calcareous particles play in the statocyst?

The calcareous particles, or statolith, provide mass and help in detecting the orientation of the ctenophore by pressing on ciliary tufts. Signup and view all the answers

What is meant by the body being triploblastic in ctenophores?

Being triploblastic means that the ctenophore body is developed from three germ layers: ectoderm, mesoderm, and endoderm. Signup and view all the answers

Study Notes

Phylum Ctenophora

Includes a small group of free-swimming, planktonic marine animals.
Body is transparent and delicate, gelatinous.
Resembles coelenterates, often grouped with them.
Highly transparent, also called comb-jellies or sea-walnuts.
No significant economic value, but used in experiments.

History

Ctenophores have a shorter recorded history than coelenterates.
Ancient people likely recognized common forms.
First detailed description by a ship's doctor, Martens (1671).
Linnaeus and Cuvier placed some under Zoophyta, class Acalephae.
Eschscholtz (1829-1833) differentiated into orders (Ctenophorae, Discophorae and Siphonophorae).
Leuckart (1847) separated from echinoderms.
Hatschek (1839) placed all ctenophores in a distinct phylum.

Habits and Habitat

Common marine animals, often in large schools.
Widely distributed, abundant in warmer seas, but also found in temperate and arctic regions.
Cosmopolitan species exist.
Mostly planktonic, floating near the surface waters.
Some species live at significant depths (up to 3000 meters), leading a benthic or creeping existence.
They rest vertically in the water and move by feeble, wave-like movements of comb plates.

External Features

Body shape varies (spherical, pear-shaped, cylindrical).
Commonly called gooseberries or sea-walnuts.
Outer surface lacks hard skeletal parts.
Mouth at one end (oral) and sense organs at the opposite end (aboral).
Biradial symmetry; body parts radiate in equal halves on opposing sides.
Size ranges from millimeters to 1 meter or more.
Colour varies (transparent, white, orange, purple), depending on structures.
Comb plates (ctenes) are arranged in rows, used for swimming, giving a visible effect of combs.
Tentacles are retractable, found near the aboral end.
Tentacles have branches (pinnae); with a core covered by mesenchymal.

Internal Anatomy

Triploblastic body.
Outer epidermis (syncytial or cuboid/columnar cells).
Sensory, glandular, mucous, and pigment cells.
No nematocysts (except in Euchlora rubra).
Sensory organ at the aboral end (statocyst); contains calcareous particles (statolith) balanced by cilia (balancers).
Multiple ciliated furrows which lead from the sense organ into the comb-plates.

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Description

Explore the fascinating world of Ctenophora, a phylum comprising delicate, transparent marine animals known as comb-jellies. This quiz covers their history, habits, and habitat distribution, highlighting their characteristics and importance in marine ecosystems. Test your knowledge on their classification and ecological roles.