Annelida: Segmented Worms PDF

Annelida: The Wonders of Segmented Worms Annelida is a diverse phylum of segmented worms that have captivated the interest of biologists and nature enthusiasts alike. From the humble earthworm to the mesmerizing marine polychaetes...

Annelida: The Wonders of Segmented Worms Annelida is a diverse phylum of segmented worms that have captivated the interest of biologists and nature enthusiasts alike. From the humble earthworm to the mesmerizing marine polychaetes, these remarkable creatures exhibit a remarkable array of adaptations that enable them to thrive in a wide range of environments. group members: Angieviev B. Rejean S. Marjorie Canoy Bionat Toraya ANNELIDA Phylum Annelida is a very broad phylum belonging to the kingdom Animalia. The Annelids are found in aquatic as well as terrestrial environments. These are bilaterally symmetrical invertebrate organisms. Their segmented body distinguishes them from any Taxonomy and Classification 1. Phylum Annelida Annelids are classified under the phylum Annelida, which is derived from the Latin word "annellus" meaning "little ring." This refers to their distinctive segmented body plan. 2. Classes The phylum Annelida is divided into three main classes: Polychaeta (marine worms), Oligochaeta (earthworms and their relatives), and Hirudinea (leeches). 3. Diversity Annelids are a highly diverse group, with over 17,000 species described, ranging from microscopic interstitial worms to the massive Australian giant kelp worm, which can reach up to 3 meters in length. Unique Characteristics of Annelids Segmented Body Setae Closed circulatory system Annelids are characterized by Annelids possess small, hair- their distinctive segmented Annelids have a closed circulatory like structures called setae system, meaning their blood is body plan, with a series of that protrude from their body repeating units called contained within a network of blood segments. These setae act vessels. This allows for more metameres or segments. This as bristles, helping the segmentation allows for efficient transport of oxygen, worms to move and burrow nutrients, and waste throughout the greater flexibility and through the soil or water. specialization of body parts. body. Reproduction and Life Cycle 1. Hermaphroditic Annelids are typically hermaphroditic, meaning each individual worm has both male and female reproductive organs. This allows for greater reproductive flexibility and the potential for self- fertilization. 2. External Fertilization Many annelids release their gametes (eggs and sperm) into the water, where fertilization occurs externally. The fertilized eggs then develop into free-swimming larvae. 3. Cocoon Production Some annelids, such as earthworms, produce cocoons that contain fertilized eggs. These cocoons are deposited in the soil, where the young worms develop and hatch, emerging as miniature versions of the adult worms. Locomotion and Adaptation Crawling Many annelids, such as earthworms, move by using their segmented body and setae to crawl through the soil or across surfaces. Burrowing Some annelids, particularly marine polychaetes, burrow through sediments using muscular body movements and their setae to anchor themselves. Swimming Certain marine annelids, like the ragworm, have developed specialized appendages called parapodia that allow them to swim through the water with great agility. Annelid Anatomy and Function Digestive System Nervous System Annelids have a complete digestive Annelids possess a well-developed nervous system, with a mouth, pharynx, system, with a central brain, ventral nerve esophagus, crop, gizzard, and intestine, cord, and numerous sensory receptors that allowing them to efficiently break down allow them to perceive and respond to their and absorb nutrients from their food. environment. Circulatory System Excretory System The closed circulatory system of Annelids have a specialized excretory system, annelids includes a dorsal blood vessel, with structures called nephridia that filter a ventral blood vessel, and numerous waste products from the blood and help capillaries that facilitate the efficient maintain homeostasis within the body. transport of oxygen, nutrients, and waste throughout the body. Anterior - The ‘head’ or front of the earthworm is called its anterior. Prostomium and mouth - The first segment on the earthworm’s anterior holds the prostomium and mouth. The prostomium, resembling a lip, is in front of the mouth. Skin - Earthworms breathe and lose moisture through the skin. Light-sensitive cells are scattered in their skin. They give skin the ability to detect light and changes in light intensity. Skin cells are also sensitive to touch and chemicals. Segment - The body is divided into segments. These resemble rings. Large earthworms are made up of hundreds of segments. Setae - Each segment has a number of bristly hairs that earthworms use to help them move. Sometimes, if you run your fingers on the underside (ventral) of the earthworm, you can feel the setae. Clitellum - The glandular ring or saddle found on mature earthworms. After mating, the clitellum secretes a cocoon of eggs. Dorsal - The top of the earthworm running from the anterior to the posterior. Ventral - The underside of the earthworm running from the anterior to the posterior. You can locate the ventral section by feeling for the setae. Anus - The posterior (last) segment of the earthworm’s body. The anus excretes wastes (worm casts). Pharynx - Earthworms push the pharynx out of their mouths to grasp hold of organic mattter. Gizzard - Earthworms do not have teeth, so they use the strong muscles of the gizzard (and grains of sand and soil) to grind up their food. Intestine - Once the food is ground up, it moves into the intestine where digestive fluids continue to break down the food so it can be absorbed. Aortic arches - Most earthworm species have five aortic arches or ‘hearts’ that move blood around the body. Dorsal and ventral blood vessels - The dorsal blood vessel runs along the length of the upper side of the earthworm. It contracts and pumps blood to the aortic arches. The ventral blood vessel runs along the lower length of the earthworm. Cerebral ganglion - The earthworm’s ‘brain’. The cerebral ganglion is connected to a ventral nerve cord that runs the length of the body. Each segment is connected to this cord, allowing earthworms to move and respond to light, touch, chemicals, vibrations and more. Circular muscles - Circular muscles surround each segment. When earthworms squeeze these muscles, they become long and thin. Circular muscles alternate with longitudinal muscles to help earthworms move. Longitudinal muscles - Longitudinal muscles run the length of the earthworm. When  Examples of Annelid Diversity Earthworms Leeches Polychaetes Giant Australian Marine Worm Earthworms are Leeches are another type Polychaetes, or The giant Australian marine perhaps the most well- of annelid, known for their marine bristle worms, worm, also known as the known annelids, ability to attach to the are a diverse group of Australian giant kelp worm, playing a crucial role in annelids found in a is one of the largest skin and feed on blood. variety of aquatic soil health and nutrient While some species are annelids, reaching up to 3 cycling. They are environments, from meters in length. These parasitic, others are shallow tidal pools to impressive worms live in found in a wide range important in medical the deep ocean floor. the waters off the southern of habitats, from applications. coast of Australia. gardens to forests. Fascinating Trivia about Annelids 1. Regeneration 2. Bioluminescence Many annelids have the remarkable Some marine annelids, such as the ability to regenerate lost body parts, fireworm, are capable of producing such as their head, tail, or internal bioluminescent light through a organs. This incredible capacity has chemical reaction, which they use for fascinated scientists and has communication, defense, and to potential applications in medical attract prey. research. 3. Medicinal Uses 4. Ecosystem Engineers Leeches have been used in traditional Earthworms are often referred to a medicine for centuries, and their saliva s "ecosystem engineers" due to their contains compounds that have been crucial role in aerating and enriching soil, found to have anticoagulant and pain- making it more suitable for plant growth relieving properties, making them and supporting the overall health of valuable in modern medical terrestrial ecosystems. applications. Thank You