Cnidaria is a large phylum composed of some of the most beautiful of all the salt and freshwater organisms: the true jellyfish, box jellyfish, coral and sea anemones, and hydra. Although Cnidaria is an incredibly diverse group of animals, there are several traits that link them together.
Most cnidarians are dipoblastic, which means that they are composed of only two layers of cells. The outer layer is known as the ectoderm or epidermis, and the inner layer is known as the endoderm or gastrodermis. These layers contain the nerve nets that control the muscular and sensory functions of the animal. Between these layers is a jelly-like noncellular substance known as mesoglea, which in true jellyfish constitute the vast bulk of the animal (hence their common name). In other species, the mesoglea may be nearly absent. All cnidarians have a single opening into the body which acts as both the mouth and anus, taking in food and expelling waste. In most species the mouth is lined with tentacles which act to capture food. The mouth leads to a body cavity known as the coelenteron, where the food is digested. This body cavity has given this phylum its other, less commonly used, name of Coelenterata.
Cnidarians have a complex life cycle that, depending on the species, may alternate between two forms. The first form is known as a polyp, which is sessile (anchored to one spot). The polyps are tubular in shape, with the mouth, often lined with tentacles, facing upwards. The bodies often con...
Fox, R. 2001. Invertebrate Anatomy OnLine: Artemia Franciscana. Lander University. http://webs.lander.edu/rsfox/invertebrates/artemia.html, retrieved February 13, 2011.
In reproduction, the female produces clusters of eggs that she carries in one or two egg sacs that are attached to her abdomen. Once hatched, The T. Californium’ life cycle has quite a few stages. The first being six naupliar (young) stages lasting 4 – 10 days. Next come the 6-copepodite stages (7-14 days for the first 5 stages) ending in the last stage where T.californicus is a sexually mature adult. Adults then live from 40 – 90 days after the stages are complete (Rickets and Calvin 1985).
“Cnidarians” is Greek for “stinging nettle” (“Introduction to Cnidaria"). Phylum Cnidaria include freshwater hydra, jellyfish, and corals. Each of these invertebrates go through transitions in body forms. Jellyfish are the most unusual and complex out of the phylum. Jellyfish are in the class Scyphozoa, which means true jellyfish.
shape]” (Veiled Chameleon, n.d.), and the movement of the organism is slow and calculating and in the
Sabellaria cementarium belongs to the phylum Annelids and is an invertebrate polychaete species. They are found in small clumps at the rocky bottoms of the sea floor where they use the rich source of natural phytoplankton as their primary diet (Qian and Chia, 1990). The tube-like worms can behave social and form extensive reefs or independently build hollow tubes in to the sandstone (pawlik and Chia, 1991). Embryos form a polar lobe that is absorbed in to the blastomeres at the end of division. Larval development and movement follows shortly after the 14-15 hour fertilization period where spiral cleaving of the fertilized oocytes appears (Render, 1983). Much is still not known about the invertebrate worm in their natural niche.
The sea cucumber, or Cucumaria frondosa, make up the class Holothuroidae, of the phylum Echinodermata. The sea cucumber is related to the starfish, and can be described as big slug-like blobs. Sea cucumbers have a rubbery-like, warty body and their length can range from 0.8 inches to 6.5 feet. They have tube-like feet that project from underneath them and give them the sluggish caterpillar-like contractions as they move. Sea cucumbers breathe through branched respiratory tubes, or trees that go from the cloaca to the body cavity. The cloaca contract, forcing water into the respiratory. The water is emptied into the body cavity and mixes with body fluids and supplies the sea cucum...
Imagine a creature that has a skeleton on the outside of its body, that has eyes that protrude on stalks, and whose blood doesn't flow through blood vessels but, instead, pools and surrounds body tissues. What is this monstrous creature? What if I were to tell you this isn't a monster, but something you've probably seen and maybe even eaten?! Yep, this strange creature is a __crustacean__! There are over 50,000 species of crustacean and they come in all shapes and sizes, from an ocean-dwelling crab to an immobile barnacle! But before we delve into the types of crustaceans, let's take a moment to go over the characteristics and anatomy they share.
Some other characteristics that make worms of the phylum Platyhelminthes unique are the fact that they are light sensitive. They often try to avoid brightly lit areas. They are so sensitive because they possess’ bundles of light-sensitive eyes that are often described as primitive eyes (Snyderman and Wiseman 84). Another interesting characteristic of the flatworms is that they are hermaphroditic. This means that they posses both male and female reproductive organs. When one learns of this they may think that self-fertilization would be common, but it is not. Flatworms also posses amazing regenerative properties. When they lose a body part, a new one will form, and it some cases, the body part often regenerates an entirely new flatworm (Snyderman and Wiseman 84).
The small intestine consists of about twenty feet of tubing that winds about itself to form the small intestine. The first foot of the small intestine is called the duodenum. This is where the majority of the digestion takes place. The pasty liquid moves from the stomach and into the duodenum where the paste is mixed with enzymes and chime. The duodenum also receives digestive juices from the pancreas and bile from the liver. Once the food comes out of the duodenum, it is ready to be absorbed into the blood vessels and used for various purposes throughout the body. The next part of the small intestine where the food get absorbed into the body is called the epithelium. The epithelium is similar to a fluffy towel in that it has large folds and it also has small finger-like outgrowths where the nutrients are grabbed and transported into the blood vessels. Whatever is not absorbed in the small intestine then move into the large intestine (2012, Pg.
Piatigorsky, Z., Kozmik. 2004.Cubozoan jellyfish: an Evo/Devo model for eyes and other sensory systems. Int J Dev Biol 48: 719–729
Coral reefs are systems of large, underwater structures that are composed of the mineralized bodies of corals. These corals are a class of marine invertebrates known as Anthozoans, and belong to the phylum Cnidaria, and are thus related to sea anemone and jellyfish. Each individual coral animal is only a few millimeters in diameter, and a few centimeters in length. Due to their sessile nature, and their ability to reproduce asexually, they are able to construct, over many generations, massive colonies of genetically identical individuals. Additionally, they secrete a hard exoskeleton of calcium carbonate to support and protect their bodies, and it is from this process that the colony constructs what is known as a single coral “head.”
The outer layer of a reef consists of living animals, or polyps, of coral. Single-celled algae called zooxanthellae live within the coral polyps, and a skeleton containing filamentous green algae surrounds them. The photosynthetic zooxanthellae and green algae transfer food energy directly to the coral polyps, while acquiring scarce nutrients from the coral. The numerous micro habitats of coral reefs and the high biological productivity support a great diversity of other life.
The four tissue layers are the mucosa, submucosa, muscularis externa, and the serosa. The mucosa is the inner most layer which also composes of its own; the epithelial, lamina propia, and muscularis mucosa. The mucosa secretes hormones, digestive enzymes and also mucus as well. The submucosa is composed of areolar connective tissue, which contains a rich blood supply, nerve fibers and lymphatic vessels and follicles. The muscularis external is the layer that is responsible for the function of segmentation and peristalsis. It contains an inner circular layer and also an outer longitudinal layer both of smooth muscle cells. The serosa is the layer that is the outermost. It is also called the visceral peritoneum and it is areolar connective tissue that is covered with mesothelium.
Arachnida is a subphylum of Arthropoda, consisting of over 100 000 species, many of them being parasites which can carry disease. They are found in all environments, and mostly have eight legs, which is a feature, together with the fact that they do not have wings or antennae, often used to distinguish them from the other subphyla, though there are exceptions. They include spiders, scorpions, ticks and mites. Their bodies are divided up into three parts: the cephalothorax, the opisthosoma and the thorax, and use a type of lung for gas exchange. Most Arachnids are carnivorous, and eat pre-digested insects and other small animals. They reproduce using internal reproduction usually lay eggs, except for the scorpion which bears living young. The word ‘Arachnid’ comes from the Greek word ‘Arachne’ meaning ‘spider’.
Comb jellies or Ctenophores are basically fake jellyfish. Like jellyfish they are transparent are transparent, but these lacking stinging cells are basically giant balls of see-through goo. These balls of goo are located throughout most marine environments, at varied depths and temperatures they are very good conformers. The most prominent feature of Ctenophores is their cilia. Cilia are hair-like structures that are used to help this species swim. Being fake jellyfish the comb jellies are extremely predacious, they entrap food and suck them up and are known for being cannibalistic and swallowing each other whole.