cniadarian notes
What is unique about the sensory structures in class Cubozoa?
Ocelli = responsive to light (around edge of bell) Tactile sense - responsive to touch (general body surface) Statocyst - stimulated by gravity, maintains orientation of the animal with respect to the earth (equilibrium)
Describe the form, function and importance of the cnidarian gastrovascular cavity.
The gastrovascular cavity is essentially an empty space in the organism that is surrounded by tissue. Food is brought into the cavity. The tissue surrounding the cavity secretes enzymes to enable digestion.Nutrients are then absorbed directly by the cells surrounding the cavity and distributed to the rest of the organism through diffusion. The gastrovascular cavity in Cnidaria is surrounded by an inner tissue layer called the gastrodermis. The outside of the organism has a tissue layer called the epidermis. Between these two tissue layers is a gel-like region called the mesoglea.
What is meant when an organism is described as "colonial"? What are some examples of colonial cnidarians? How do colonies form?
The polypoid (POL-ip-oyd) is the configuration of corals and anemones, with the tentacles and mouth generally facing up, and the other side affixed to a substrate or connected to a colony of other creatures of the same species.
Distinguish between the subclasses of anthozoans
Anthozoa is a class within the phylum Cnidaria. Unlike other cnidarians, anthozoans do not have a medusa stage in their development. Instead, they release sperm and eggs that form a planula, which attaches to some substrate on which the cnidarian grows Hexacorallia includes coral reef builders the stony corals Octocorallia comprises the sea pens (Pennatulacea), soft corals (Alcyonacea), and blue coral Ceriantharia comprises the related tube-dwelling anemones
Name and distinguish between the classes in phylum Cnidaria. (Be able to describe at least 2 unique characteristics that would allow you to distinguish between the different classes)
1. Class Hydrozoa: Solitary or Colonial with asexual polyps and sexual medusa; one form may be suppressed as in hydra freshwater and marine; hydranths with no mesenteries. These don't have stinging cells in the gut and must kill prey before eating ( the reason that the stings are worse). Include: Portuguese Man-of-War and fresh water jellies. 2. Class Scyphozoa: Solitary; polyp stage reduced or absent; Bell-shaped madusae with no Velum (subumbrellar membrane); Enlarged mesoglea (Jelly material between ectoderm and gastroderm); all marine; eight notched umbrella that houses sensory organs. Thier toxin is a protein that can be denatured by shifting the PH. Include: "true" jellyfish (Cannonball jellyfish, sea nevil.) 3. Class Cubozoa: All solitary marine with reduced polyp stage; bell shaped medusa square in cross section; tentacles hang from corner of umbrella; no velum but velarium. These are the deadliest and can kill fish up to 5 times bigger than they are. (Sometimes they flip upside down and stick their tentacles up) 4. Class Anthozoa: All solitary or Colonial marine polyps; gastrovascular cavity subdivided by eight mesenteries or septa with nematocysts; gonads endodermal. Coral are a group of sea anemones (Anthozoans) that create a hard skeleton
What are cnidocytes? Where are they found and what are they used for? What are cnidae? What is a nematocyst? How is it different from a cnidocyte? Describe the functions of different types of cnidae.
A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one giant secretory organelle or cnida (plural cnidae) that defines the phylum Cnidaria (corals, sea anemones, hydrae, jellyfish, etc.). Cnidae are used for prey capture and defense from predators. A Nematocyst is a specialized sub-cellular organelle (part of the cell) present in cnidocyte. Thus, a nematocyst is essentially a part of a cnidocyte Types of cnidae Penetrant: a harpoon-like structure used to penetrate, referred to as nematocysts Glutinant: a sticky surface used to stick to prey, referred to as ptychocysts and found on burrowing (tube) anemones, which help create the tube in which the animal lives Volvent: a lasso-like string that is fired at prey and wraps around a cellular projection on the prey, referred to as spirocysts
Why is hydra atypical of hydrozoans?
Hydra, which is used in many textbooks to illustrate the phylum, is utterly atypical: a hydrozoan, it lacks a medusa, it has aggregations of gametogenic tissue that function as gonads, and it is among only a handful of freshwater cnidarian species
Describe the structure of a colonial hydrozoan. How can colonial hydrozoans be distinguished from colonial anthozoans
In the class Anthozoa, comprising the sea anemones and corals, the individual is always a polyp; in the class Hydrozoa, however, the individual may be either a polyp or a medusa, with most species undergoing a life cycle with both a polyp stage and a medusa stage
How can you distinguish between medusae of different cnidarian classes?
Schpozoan medusae are larger, live longer and have a more complicated structure than hydrozoan medusae
Describe the life cycle of scyphozoans, colonial hydrozoans, and sexually reproducing anthozoans. What are the various stages in each life cycle?
Scyphozoans fertilized eggs produce planular larva that attach to the sea bottom, larva turn into a polyp which either buds off or develops into a medusa to achieve sexual reproduction Most hydrozoans show the same alternation between polyp and medusa phases that the Scyphozoa, or "true" jellyfish, have. A fertilized egg develops into a sessile polyp, which buds asexually and eventually buds off one or more medusae. The medusa produce eggs and sperm, reproduce sexually, and thus the cycle is repeated. The difference between most hydrozoans and most scyphozoans is that in hydrozoans, the polyp stage usually predominates, with the medusa small or sometimes absent. Anthozoans have no medusa stage
What is a statocyst and how does it work?
Statocyst - stimulated by gravity, maintains orientation of the animal with respect to the earth (equilibrium)
What are the distinguishing characteristics of phylum Cnidaria?
The characteristic that most distinguishes them, is their "cnidocytes" (whence comes the name). These are specialized, venomous cells, used to stun, capture, and hold prey. All cnidaria are aquatic animals, and most are marine. All are radially symmetrical and have a single orifice and body cavity that performs digestive and respiratory functions.
What are septa in sea anemones? What do they do? What are acontia threads? What is the siphonoglyph and what does it do?
These septa provide body support, as well as greater surface area for the digestive layer or gastrodermis acontia thin white or colored threads attached at one end to the borders of the mesenteries, as a rule below the filaments, while the other end is free. They are laden with extraordinarily numerous nematocysts of various categories. They can be protruded through the mouth, and in some cases through special pores (cinclides) in the body-wall, for purposes of defense or paralyses of prey. In histological structure they differ completely from the mesenterial filaments The siphonoglyph is a ciliated groove at one or both ends of the mouth of sea anemones and some corals. The siphonoglyph extends into a pharynx and is used to create currents of water into the pharynx. These water currents are important for respiration and maintenance of internal pressure
What is an unusual feature of the nervous system of cnidarians (hint: in which directions are signals transmitted)? What is a rhopalium? Where are rhopalia located on a medusa and what sensory structures are found there?
They also have rhopalium, a complex of sensory structures (one statocyst, two simple eyes, and two chemosensory pits).
Why are coral reefs generally limited in distribution to shallow marine waters?
Well, coral tends to be in relativley shall water because they need zooxanthellae in order to survive (this is why coral bleaching is such a hge problem; the zooxanthellae is being expelled... http://en.wikipedia.org/wiki/Coral_bleac... Anywho...the zooxanthellae (that the coral is dependant on) needs sunlight in order to survive and in order for sunlight to reach the zooxanthellae they have to be in shallow water where the sun's rays still penetrate the water.
Describe various forms of asexual reproduction in different classes of cnidarians.
budding, fragmentation
How do cnidarians feed? What do they eat?
cnidarians are predators that catch their prey with their cnidae
What anatomical innovations are found in phylum Cnidaria? Why are these innovations significant (how are they an improvement over what is seen in a sponge)?
cnidarians can move and have a digestion system
What types of skeletal support systems are observed in different groups of cnidarians? Contrast the skeletons of hexacorallian (zoantharian) and octocorallian (alcyonarian) corals
hexacorallian zoantharian (sea anemone) These organisms are formed of individual soft polyps which in some species live in colonies and can secrete a calcite skeleton can also have hydro static skeleton octocorallian (alcyonarian) corals These organisms have an internal skeleton secreted by mesoglea and polyps with eight tentacles and eight mesentaries
Describe 3 different types of interactions between cnidarians and other organisms.
nuddibranch consume snidarians and use heir cnidocytes , cnidarians eating other animals by killing them with their cnidae, coral forming a symbiotic relationship with zooxanthellae
How is the body of a polyp and medusa organized? How are the two forms similar and different?
polyp and medusa, names for the two body forms, one nonmotile and one typically free swimming, found in the aquatic invertebrate phylum Cnidaria (the coelenterates). Some animals of this group are always polyps, some are always medusae, and some exhibit both a polyp and a medusa stage in their life cycle. The polyp is a sessile, or nonmotile, organism; well-known solitary polyps are the sea anemone and the freshwater hydra. The medusa, when free swimming, is popularly known as a jellyfish
What is polymorphism?
the occurrence of different forms among the members of a population or colony, or in the life cycle of an individual organism( medusa vs polyp)
