Medusa form

Fig. 8.5 The polyp and medusa body forms characteristic of phylum Cnidaria are structurally similar, (a) The polyp form as seen in Hydra, (b) The medusa form is basically an upside-down polyp. The mouths are a primitive muscle system. Note the separation of organs.

Cnidarians are a group of animals that includes hydrozoids, sea fans, anemones, and jellyfish. All of the organisms in this group have simple, saclike bodies in the polyp or medusa forms (see Figure 3.3). The bell-shaped bodies of jellyfish are referred to as medusae, and the vaselike structures that are typical of coral and anemones are polyps. 

Another type of cnidarian that lives in the intertidal zone is the hydroid, an animal that differs from anemones in two ways Flydrozoids exist in both the polyp and medusa forms, and they form colonies in which individual polyps have specialized duties, dividing the labor needed to support the group. In colonies, some individuals assume responsibility for reproduction while others take charge of tasks such as... 

Unlike hydrozoids, jellyfish are cnidarians that spend their entire lives in the medusa form. Most live in water deeper than the intertidal area, but individuals sometimes stray or wash into the shallow water of the surf. One very unusual type of jellyfish is native to the intertidal zone, the stalked jellyfish (Haliclystus). Instead of the usual medusa form, the body of the stalked jellyfish is attached to the substrate by a stalk on which the medusa is flipped upside down, with the mouth facing up, giving the animal the appearance of a flower. The petals of the flower are eight lobes that are tipped with club-like tentacles. Haliclystus auricula is one kind of stalked jellyfish whose lobes end in hundreds of tentacles. This very small jellyfish, reaching l4 inches (4.45 cm) in height, favors quiet tide pools where it may be found attached to snails, seaweed, or rocks. H. auricula feeds on worms and other small shore animals. 

Hydrozoa. Hydrozoans may be in the form of medusae or polyps and may occur singly or in colonies. Although some hydrozoans show only the medusoid form, most species possess a polynoid... 

Individuals of the next most complex major phylum, Cnidaria (formerly Coelenterata), are radially symmetric with two distinct cell layers, the endoderm and ectoderm. Many species exist both as a polyp or hydra form (Fig. 1-13) and as a medusa or jellyfish. The jellyfish apparently has no brain but the ways in which its neurons interconnect in a primitive radial net are of interest. The Cnidaria have a very simple body form with remarkable regenerative powers. The freshwater hydra, a creature about 1 cm long (Fig. 1-13), contains a total of -105 cells. A complete hydra can be regenerated from a small piece of tissue if the latter contains some of both the inner and the outer cell layers.121 122... 

Several species of stalked, plantlike hydrozoans and octo-corals form small colonies in shallow intertidal waters. These organisms spend part of their lives as medusae and part as polyps. Like anemones, they gather food with their small tentacles. A less common but more conspicuous cnidarian along the shore is the jellyfish. Most jellyfish found in the intertidal zone are simply washed in, although the stalked jellyfish makes its home there. 

The liver is covered with an anterior reflection of the peritoneum known as Ghsson s capsule. Other extensions of the peritoneum form ligaments that hold the Hver in place. Internal extensions of the capsule provide an internal supporting framework that divides the liver into lobules and ultimately surrounds blood vessels and nerves. One of the ligaments, the ligamentum teres, is the vestigial remnant of the umbilical vein and connects the umbilicus to the inferior border of the liver. When portal hypertension occurs, the umbilical veins may reopen, leading to venous dilation around the umbilicus (termed caput medusae). 

Nanoparticles Nanoparticles can be formed from surfactants, polymers, or polyamino acids. The concept is mainly that viable particles are formed, they can maintain their shape and use during preparation, they are stable, and the particles formed are in the nanometer range. An example of nanoparticles is the Medusa concept by Flamel Technologies. 

Amphiphilic CyDs (Lollipop, Cup-and-ball, Medusa-like, Skirt-shaped, and Bouquet) have been synthesized by the grafting of various substituents to different faces of native CyDs [65]. (Syntheses of CyD derivatives are presented in Chapter 2). Among them. Medusa-like cyclodextrins and Skirt-shaped cyclodextrins have demonstrated their ability to form nanocapsules or nanospheres. 

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