Table of Contents
What are the characteristics of phylum Nemertea?
Characteristics of Nemertea:
- Bilaterally symmetrical and dorsoventrally flattened.
- Body has more than two layers of cells with tissues and organs.
- Body has a through gut with a mouth and anus.
- Body has no body cavity.
- Has a blood system with blood vessels.
- Has a well developed nervous system and a brain.
Are Nemertea Triploblastic?
Nemertean worms are ribbon-shaped, bilaterally symmetrical worms that are usually less than twenty centimeters (7.9 inches) long, although a few reach several meters in length. The body of a ribbon worm is triploblastic, meaning they have three layers of tissue (endoderm, mesoderm, and ectoderm).
What does a ribbon worm look like?
Unlike annelids, ribbon worms are not segmented. Instead, ribbon worms look a little like living linguine noodles, but are often very beautiful, with bright colors or stripes. They can stretch and contract their soft bodies, and they move by gliding over the bottom using slime and tiny hairs called cilia.
Do Nemertea have a true coelom?
Flatworms (phyla Platyhelminthes, Nemertea, and Mesozoa) lack a coelom, although nemerteans have a fluid-filled……
Are nemertean poisonous?
Certain nemertean species are known to contain remarkably potent toxins: pyridine alkaloids, tetrodotoxin (TTX), and cytolytic or neurotoxic peptides. The terms nemerteans, nemertean worms, and ribbon worms are used interchangeably.
Is Nemertea a Pseudocoelomate?
The nemertini are the simplest eucoelomates. These ribbon-shaped animals bear a specialized proboscis enclosed within a rhynchocoel. The development of a closed circulatory system derived from the coelom is a significant difference seen in this species compared to other pseudocoelomate phyla.
Is Nemertea segmented?
Taxonomic level: phylum Nemertea; grade of construction: organs derived from three tissue layers; symmetry: bilateral; type of gut: complete, with anus; type of body cavity other than gut: rhynchocoel surrounding proboscis; segmentation: absent; circulatory system: present; nervous system: small bundles of nerves ( …
What makes a ribbon worm unique?
A defining characteristic of ribbon worms is the presence of a proboscis—a unique muscular structure inside the worm’s body. When attacking prey, they compress their bodies to push out the proboscis like the finger of a latex glove turned inside-out.
Why did flatworms lose their coelom?
Flatworms would have lost the coelom secondarily. Since their acoelomate condition is no longer indicative of a primitive origin, most of their characters put them in the protostomes, with the spiralian phyla. This position suggests the ancestors of flatworms lost both the anus and the coelom.
What is the longest worm?
bootlace worm
The longest species of worm of any kind is the bootlace worm (Lineus longissimus), a species of nemertean or ribbon worm, inhabiting shallow waters of the North Sea.
Does Nemertea have nerves?
The main components of the nemertean nervous system are the central nervous system consisting of a brain and nerve cords, the peripheral nervous system that includes nerves and plexus, and finally the sensory structures.
Is Nemertea a Coelomate?
The results firmly placed nemerteans with mollusks and annelids in lophotrochozoa (Figure 4). This means that the rhynchocoel and contractile blood vessels found in nemerteans are in fact true coeloms, and implies that an acoelomate form truly is basal, and coelomate forms more derived.
What are the characteristics of the Nemertea phylum?
Nemertea are soft and unsegmented animals (Figure 1). A unique characteristic of this phylum is the presence of a proboscis enclosed in a rhynchocoel.
What kind of food does a Nemertea eat?
The carnivorous marine ribbon worms or nemertines (Phylum Nemertea or Phylum Rhyncocoela) are predators of snails, small crustaceans, mollusks, and polychaetes.
How many species of Nemertea worms are there?
Approximately 1300 valid described species of the phylum Nemertea, or ribbonworms, are known worldwide. Current fieldwork suggests that at least several times this number remain to be named or discovered. Nemerteans are unsegmented worms characterized by a unique and remarkable eversible proboscis.
What kind of proboscis does a nemertea have?
Nemeteans have eversible proboscis situated in rhynchocoel. Nemerteans range in length from a few millimeters to 30 meters (stretched) in length (most commonly 20 cm or less) and may be drab or very brightly colored. They are unsegmented, without a differentiated head, and are most often flattened (occasionally convex dorsally or cylindrical).