Annelida
Annelida are phylum that are classified by their soft bodies, metamerism or segmentation, and soft bristles made of chitin called chaetae that surround the body of annelida worms. About 9,000 species of annelida have been identified biologists. All 9,000 species can be classified into three categories: earthworms and freshwater worms (oligochaeta), leeches (hirudinea), and marine dwelling worms (polychaeta). Each category of annelida are comprised of many discrete defensive tactics and movement techniques that best suit their inhabited environment. Despite the differences, each species of annelida have evolved their tactics to best ensure survival long enough to reproduce.
Polychaeta Defense/Movement
Polychaeta possesses a muscular appendages called parapodia surrounding their body. The parapodia are utilized as paddles to assist the polychaeta in swimming, or used for locomotion across the ocean floor and digging out burrows. However, the tiny bristles protruding from the bodies of Polychaeta are not only used for movement. For example, fireworms, marine Polychaeta, utilize their chaetae for defensive reasons. Their fragile and hollow tubes are filled with a deadly and painful toxin, that when touched the brittle tubes break releasing the poison. The toxin released is highly effective, for when in contact with the skin it causes immense pain to the victim. Additionally, many polychaeta have the ability to secrete bright bioluminescent light when threatened. The bright light distracts predators as they make an escape.
Some polychaeta (Alciopid polychaeta) have large complex eyes. Their eyes consist of corneas, irises, lenses, and other structures needed for the high-resolution they have. Additionally, they don’t have a blind spot, as people do, because their retinas are directed towards the light instead of away from light. As a result of their advanced vision, it makes it incredibly hard for predators to catch them, for these small marine worms can see a predator coming from a substantial distance away.
Oligochaeta Defense
Bristles, known as setae, are used as sensing devices that identify vibration in the soil and digging mechanisms. The setae stick to dirt and the earthworm then contracts its body to force itself through the dirt. The defenses of earthworms begin on a microscopic level against the harmful bacteria they encounter. Mucus is excreted out of the worm’s coelomic cavity dorsal pours and serves as an important component in keeping bacteria out of the worm’s coelomic cavity. However, once bacteria enter into the cavity via the dorsal pour, it is met phagocytes, a cell produced within the worm capable of consuming the bacteria, and other humoral factors that easily prevent the spread of bacteria in the coelomic cavity. When it comes to predators oligochaeta basically no defense and are a fairly easy target, however, they are expert burrowers to escape winter or a predator oligochaeta can burrow itself dozen of feet underground in a short amount of time. Worms also have the ability to tell when it is night time and safer to return to the surface. However, these worms are not completely useless when it comes to defenses. When attacked by a predator oligochaeta have the ability to rigorously twist about to escape the clenches of its predator. Its mucus-coated skin creates a slippery seal around the worm that also helps in escaping. Additionally, some worms can give off an odor that will turn off its attacker.
Hirudinea Defense
Along the surface Hirudinea (leeches) creep in looping movements of the body using muscle contractions, by attaching their mouth, which acts as a sucker, on the surface, and pulling their body towards their mouth. Aquatic leeches have the ability to freely swim through and up-and-down undulation of the body that propels the leech forwards.
Leeches show the most carnivorous traits out of all other annelida species. For such reason, they show little defense mechanisms other than their ability to quickly swim, the pigmentation of their body allows for optimal camouflage in their swampy freshwater terrains, and the ability to contract their muscles into tight segments to fit into small spaces which acts as an evasive strategy when threatened.
Polychaeta Defense/Movement
Polychaeta possesses a muscular appendages called parapodia surrounding their body. The parapodia are utilized as paddles to assist the polychaeta in swimming, or used for locomotion across the ocean floor and digging out burrows. However, the tiny bristles protruding from the bodies of Polychaeta are not only used for movement. For example, fireworms, marine Polychaeta, utilize their chaetae for defensive reasons. Their fragile and hollow tubes are filled with a deadly and painful toxin, that when touched the brittle tubes break releasing the poison. The toxin released is highly effective, for when in contact with the skin it causes immense pain to the victim. Additionally, many polychaeta have the ability to secrete bright bioluminescent light when threatened. The bright light distracts predators as they make an escape.
Some polychaeta (Alciopid polychaeta) have large complex eyes. Their eyes consist of corneas, irises, lenses, and other structures needed for the high-resolution they have. Additionally, they don’t have a blind spot, as people do, because their retinas are directed towards the light instead of away from light. As a result of their advanced vision, it makes it incredibly hard for predators to catch them, for these small marine worms can see a predator coming from a substantial distance away.
Oligochaeta Defense
Bristles, known as setae, are used as sensing devices that identify vibration in the soil and digging mechanisms. The setae stick to dirt and the earthworm then contracts its body to force itself through the dirt. The defenses of earthworms begin on a microscopic level against the harmful bacteria they encounter. Mucus is excreted out of the worm’s coelomic cavity dorsal pours and serves as an important component in keeping bacteria out of the worm’s coelomic cavity. However, once bacteria enter into the cavity via the dorsal pour, it is met phagocytes, a cell produced within the worm capable of consuming the bacteria, and other humoral factors that easily prevent the spread of bacteria in the coelomic cavity. When it comes to predators oligochaeta basically no defense and are a fairly easy target, however, they are expert burrowers to escape winter or a predator oligochaeta can burrow itself dozen of feet underground in a short amount of time. Worms also have the ability to tell when it is night time and safer to return to the surface. However, these worms are not completely useless when it comes to defenses. When attacked by a predator oligochaeta have the ability to rigorously twist about to escape the clenches of its predator. Its mucus-coated skin creates a slippery seal around the worm that also helps in escaping. Additionally, some worms can give off an odor that will turn off its attacker.
Hirudinea Defense
Along the surface Hirudinea (leeches) creep in looping movements of the body using muscle contractions, by attaching their mouth, which acts as a sucker, on the surface, and pulling their body towards their mouth. Aquatic leeches have the ability to freely swim through and up-and-down undulation of the body that propels the leech forwards.
Leeches show the most carnivorous traits out of all other annelida species. For such reason, they show little defense mechanisms other than their ability to quickly swim, the pigmentation of their body allows for optimal camouflage in their swampy freshwater terrains, and the ability to contract their muscles into tight segments to fit into small spaces which acts as an evasive strategy when threatened.
