Hobbies And Interests
Description
The man-of-war's body appears as a translucent, saclike float adorned with long tentacles streaming from the float's bottom. The colony comprises four types of specialized individuals. A single polyp forms the pneumatophore, or float, portion of the colony; dactylozooids make up the tentacles; gastrozooids feature in the colony's feeding behavior; and gonozooids perform reproductive functions. A crest sits atop the pinkish-blue pneumatophore, which fills up with gases comparable to the mixture making up air. The tentacles function both as appendages for food retrieval and as instruments of defense.
Movement
Incapable of self-propelling motion, the Portuguese man-of-war drifts on ocean currents. When gas fills the pneumatophore, the organism floats to the surface of the water; by letting gas out of the pneumatophore, the organism sinks beneath the ocean surface to rehydrate. The pneumatophore acts as a sail to guide the colony's movement. Analogous to the human quality of left- or right-handedness, each colony leans either 45 degrees to the right or the left. The leaning quality of the float serves two possible functions: to direct members of the population to different corners of the oceans and to ensure that at least half of the population survives if the other half meets with unfavorable conditions. Currents sometimes carry numerous men-of-war near coastlines, where they threaten divers, swimmers and sunbathers.
Feeding Habits and Diet
The Portuguese man-of-war is a predatory creature that consumes marine animals such as shrimp and fish, its main prey. The man-of-war stretches out its tentacles to lure and trap prey, rejecting food sources enveloped in shells because the tentacles' stinging cells cannot penetrate, and thus subdue, hard-bodied animals. The organism's digestive apparatus consists of several stomach-like structures called gastrozooids attached at the float bottom. The gastrozooids, which connect to mouths, release substances called enzymes to digest the different components of food. The mouths excrete any undigested food back into the water.
Reproduction
Reproduction in the man-of-war occurs in two stages. The gonozooids of each mature Portuguese man-of-war colony produces either female or male sex cells, or gametes. During the autumn months, male colonies release sperm and female colonies release eggs near the surface of the water. The sperm fertilize eggs in the open water. Scientists are unsure whether or not the gonozooids themselves are released into the water as well. The second stage describes the fertilized eggs becoming immature swimming forms called larvae and dividing to form new colonies.
The Sting
The tentacles on the Portuguese man-of-war, which range in length from a few centimeters to tens of meters, sport stinging cells called cnidocytes. The cnidocytes lie along the tentacles and consist of coiled, barbed stingers -- the nematocysts -- that spring to action when they contact flesh. The nematocyst shoots out at lightning speed and penetrates the skin, dispersing its venom into the tissues. The cnidocyte also responds to a substance called glutathione that originates in animals that have been injured or have died. The sting causes welts to appear on the skin where the tentacles have touched. The nematocysts release physalitoxin into the tissues, causing immediate pain, vomiting and soreness in the abdomen; man-of-war stings do cause an occasional death. Sand, fresh water, alcohol or vinegar rubbed into the wound, previously thought to be effective, actually aggravate the injury. Instead, washing the wounds with seawater and packing them with ice offers some relief from the stinging.