Ctenophora

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Comb Jellies, a phylum of about 100 widely distributed marine animals resembling jellyfish. The comb jellies have eight rows of comblike plates arranged longitudinally around the body. The plates are moved back and forth in a rippling motion and serve to propel the animal through the water. Most species have two long tentacles at either side of the transparent body, which are used to capture prey. In general the bodies of comb jellies are oval, with a throat opening into the body cavity. They have no separate digestive system, the particles of food being ingested by the individual cells within the body. A sense organ at the opposite end of the body from the mouth is composed of a mass of tiny bony particles, supported away from the body on four legs. Impulses from this organ pass through the legs and into the body of the animal along grooves in the body that contain a large number of hairlike cilia. These grooves, although not true nerves, perform a similar function. Most of the ctenophores are only 7.5 to 10 cm (3 to 4 in) long. One species commonly called Venus's-girdle has a ribbonlike body about 1.5 m (about 5 ft) long, with a mouth on one edge of the center of the ribbon.

Scientific classification: Comb jellies make up the phylum Ctenophora. The Venus's-girdle is classified as Cestum veneris.

Types of Invertebrates

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Ctenophora -> Jellyfish-like marine animals distinguished by eight rows of cilia that propel the body in swimming. They feed on other invertebrates using two retractable sticky tentacles to capture prey. All ctenophores are hermaphroditic and reproduce sexually. Many are luminescent. – Examples: Sea walnuts, comb jellies

Platyhelminthes -> Structurally simple worms with no anus or circulatory system. Known as flatworms, their flattened bodies enable internal tissues to be near the skin surface, permitting gas and nutrient exchange with the environment. A muscular layer just beneath the skin layer aids in locomotion. Flatworms are hermaphrodites and reproduce sexually. They typically have a life cycle involving a parasitic larval stage. Many types of flatworms are parasites of vertebrates. – Examples: Flatworms, flukes, tapeworms

Mesozoa -> Minute parasitic animals of invertebrates, particularly squids and octopuses. These worms have a simple, elongated, ciliated body. They reproduce sexually and have a complex life cycle involving more than one larval form. – Exmaple: Rhopalura granosa

Nemertea or Rhynchocoela -> Animals characterized by a proboscis, a long, muscular tube used in capturing invertebrate food. Nemerteans have elongated, flattened bodies and they lack an internal body cavity. They have a mouth opening for food ingestion and an anal opening for wastes. The blood of some nermerteans contains oxygen-carrying hemoglobin. Nemerteans reproduce sexually. – Examples: Nemertine worms, ribbon worms

Gastrotricha -> Microscopic multicellular animals that inhabit both freshwater and marine water. An external layer, the cuticle, encasing these animals contains cilia that aid in locomotion. Adhesive tubes found on the sides or at the posterior end aid in surface attachment. Freshwater species have a forked tail. These animals feed on dead or living bacteria, diatoms, or small protozoa. Marine species are hermaphroditic, while most fresh water species are female, reproducing by parthenogenesis. – Examples: Turbanella cornuta, Chaetonotus anomalus

Rotifera or Rotatoria -> Microscopic aquatic animals characterized by a corona, a wheel-shaped organ on the head used in feeding and swimming. The rapid beating of the cilia on the corona draws nutrient-containing water into the mouth. A protective cuticle covers the elongated, cylindrical body. Reproduction is sexual during brief periods of the year and throughout the rest of the year females reproduce via parthenogenesis. – Examples: Synchaeta oblonga, Phylodina roseola

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