How many species of Nemertea are there?
How many species of Nemertea are there?
Approximately 1300 valid, described species of the phylum Nemertea, or ribbonworms, are known worldwide, inhabiting oceans, freshwaters, and land. Current field-work suggests that at least several times this number remain to be named or discovered.
Are ribbon worms nematoda?
Nemertea is a phylum of invertebrate animals also known as ribbon worms or proboscis worms. Alternative names for the phylum have included Nemertini, Nemertinea and Rhynchocoela. A highly extensible muscle in the back of the rhynchocoel pulls the proboscis in when an attack ends.
What species do worms belong to?
Worms are members of several invertebrate phyla, including Platyhelminthes (flatworms), Annelida (segmented worms), Nemertea (ribbon worms), Nematoda (roundworms, pinworms, etc.), Sipuncula (peanutworms), Echiura (spoonworms), Acanthocephala (spiny-headed worms), Pogonophora (beardworms), and Chaetognatha (arrowworms).
Does Nemertea have a Coelom?
Nemertea and Platyhelminthes have traditionally been grouped together because they possess a so-called acoelomate organization, but lateral vessels and rhynchocoel of nemerteans have been regarded as coelomic cavities.
Are Nemertea nematodes?
Nematodes possess special excretory systems. With the exception of nemerteans (see Nemertea (Nemertini), the Ribbon Worms), no circulatory organs are present. None of these animals has clearly defined respiratory organs (except, probably, the caudal appendages in priapulids).
Where are phylum Nemertea found?
The majority of the approximately 900 known nemertean species are found in marine habitats. Some, however, live in freshwater or on land. The name proboscis worm derives from the muscular eversible proboscis, which is housed in a fluid-filled chamber above the gut.
How many worm species are there?
one million species
There are about one million species of worm, living in a wide range of habitats. They have a long, thin body, and have no legs. Many worms are parasites that live on or in another animal and use strong mouthparts to feed off that animal.
What is the phylum Nemertea?
Phylum Nemertea, or ribbon worms, contains approximately 1,200 species of bilaterally symmetrical, coelomate, unsegmented worms, which are divided into two classes, each of which is divided into two orders ( Anopla: Palaeonemertea, Heteronemertea and Enopla: Hoplonemertea, Bdellonemertea ).
What is the size of a nemertean fish?
Nemertean species also exhibit a wide range in size and length, from a few millimeters to several meters (stretched lengths may reach over 30 meters, however), and may be drab or very brightly colored. ( Brusca and Brusca, 2003; McDermott and Roe, 1985; Norenburg and Gibson, 2013; Roe, et al., 2007)
Are nemerteans free living or parasitic?
Most nemerteans are free living. However, some are parasitic, living first on the gills and later preying on the egg masses of crabs. Parasitism by Carcinonemertes species in particular has caused population declines (up to 55% egg mortality) of Dungeness crabs (Cancer magister) in California.
What are the characteristics of nemerteans?
Most nemerteans have various chemoreceptors, and on their heads some species have a number of pigment-cup ocelli. These ocelli can detect light but can not form an image. Nemerteans respire through the skin. They have at least two lateral vessels which are joined at the ends to form a loop, and these and the rhynchocoel are filled with fluid.
