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?Phylum Nemertea ?Morphology

?Baseodiscus is a genus of nemerteans whose members typically measure several meters in length.?oMost commonly found in freshwater environments there are also marine, terrestrial and parasitic species.----

?Phylum Gnatostomulida ?(jaw worms)

?Delicate worm like animals ?o0.5-1 mm in length ?oLive in interspaces of very fine sandy coastal sediments and silts ?oCan tolerate very low O2 concentration ?oHave jaws very similar to a rotifer ?oEpidermis with a single cilium on each cell ?oDigestive tract with no anus

?Gnathostomula jenneri (phylum Gnathostomulida) is a tiny member of the ?interstitial fauna between grains of sand or mud.?oThe presence of proboscis enclosed in a rhynchocoel is a unique characteristic of Nemertea ?o The proboscis serves to capture food ?oThe rhynchocoel is a fluid-filled cavity that extends from the head to nearly two-thirds of the length of the

?IN SUMMARY: PHYLUM NEMERTEA ?oThe nemertini are the simplest eucoelomates.?4.Mostly small in size, some microscopic, some a meter or longer

?5.Body wall with a cellular epidermis with thickened cuticle, sometimes molded

?6.Digestive system complete with mouth, enteron and anus, pharynx muscular and well-developed

?7.Digestive tract often only an epithelial tube with no definitive muscle layer 8.Species in this family ?are among the most commonly encountered jaw worms, found in shallow ?water and down to depths of several hundred meters

?The Pseudocoelomate Animals ?1.Symmetry bilateral, unsegmented

?2.3 germ layers

?3.Body cavity a pseudocoel.------

?The Pseudocoelomate Animals

?Phylum Rotifera

?Phylum Gastrotricha

?Phylum Kinorhyncha

?Phylum Nematoda

?Phylum Nematomorpha

?Phylum Acantocephala

?Phylum Entoprocta

?Phylum Loricifera

?Phylum Priapulida

?Phylum Rotifera ?oDerive their name from ciliated crown or corona, found at the anterior end of the animal which, when beating, gives the impression of rotating wheels.The head bears the corona, the trunk has a thickened cuticle with ridged plates and spines for defense and the foot often bears 1-4 projections called toes, which are used for attachment.?oThe development of a closed circulatory system derived from the coelom is a significant difference seen in this species compared to other pseudocoelomate phyla.Excretory system: protonephridia in some, cloaca receives excretory, reproductive and digestive products may be present

?10.?oRotifers are dioecious organisms (having either male or female genitalia) and exhibit sexual dimorphism (males and females have different forms).?o There are marine and freshwater species and they are common in lakes, ponds and seashore sands.?oThese ribbon-shaped animals bear a specialized proboscis enclosed within a rhynchocoel.-----

?Phylum Kinorhyncha ?osmall, free-living, wormlike found in marine habitats.The dorsal plates bear movable median and lateral spines.?oAlimentary, nervous, and excretory systems are more developed in the nemertini than in less advanced phyla.Circulatory and respiratory organs lacking

?9.Nervous system: cerebral ganglia or of a nerve ring connected to anterior and posterior nerves

?11.often smaller than ?, eggs microscopic with shell often containing chitin.Many species are parthenogenic

?Phylum Gastrotricha ?oMicroscopic animals, ~ 65-500 mm long.?onamed for their mode of locomotion - they pull themselves along by rings of recurved spines on their heads.?oAdults have spiny heads, spineless necks, and 11 trunk segments.Reproductive system: gonads and ducts that may be single or double; ??oThe cuticle between the plates is very flexible; in the retracted position, the neck plates close over the head.?oThis B. mexicanus from the Galapagos Islands was over 10 m long.Their bodies are roughly triangular in cross section.The head can retract into the trunk, which is covered with cuticle plates.sexes often separate, ??oThe body is usually divided into a head, trunk and foot.?oMost are < a millimeter long.?12.Development direct or within a complicated life history.

‏Phylum Nemertea
‏Morphology

‏Baseodiscus is a genus of nemerteans whose members typically measure several meters in length.
‏•This B. mexicanus from the Galápagos Islands was over 10 m long.

‏•The presence of proboscis enclosed in a rhynchocoel is a unique characteristic of Nemertea
‏• The proboscis serves to capture food
‏•The rhynchocoel is a fluid-filled cavity that extends from the head to nearly two-thirds of the length of the
—-

‏IN SUMMARY: PHYLUM NEMERTEA
‏•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.
‏•Alimentary, nervous, and excretory systems are more developed in the nemertini than in less advanced phyla.
——

‏Phylum Gnatostomulida
‏(jaw worms)

‏Delicate worm like animals
‏•0.5-1 mm in length
‏•Live in interspaces of very fine sandy coastal sediments and silts
‏•Can tolerate very low O2 concentration
‏•Have jaws very similar to a rotifer
‏•Epidermis with a single cilium on each cell
‏•Digestive tract with no anus

‏Gnathostomula jenneri (phylum Gnathostomulida) is a tiny member of the
‏interstitial fauna between grains of sand or mud. Species in this family
‏are among the most commonly encountered jaw worms, found in shallow
‏water and down to depths of several hundred meters
——-

‏The Pseudocoelomate Animals
‏1.Symmetry bilateral, unsegmented

‏2.3 germ layers

‏3.Body cavity a pseudocoel.

‏4.Mostly small in size, some microscopic, some a meter or longer

‏5.Body wall with a cellular epidermis with thickened cuticle, sometimes molded

‏6.Digestive system complete with mouth, enteron and anus, pharynx muscular and well-developed

‏7.Digestive tract often only an epithelial tube with no definitive muscle layer 8. Circulatory and respiratory organs lacking

‏9. Excretory system: protonephridia in some, cloaca receives excretory, reproductive and digestive products may be present

‏10. Nervous system: cerebral ganglia or of a nerve ring connected to anterior and posterior nerves

‏11. Reproductive system: gonads and ducts that may be single or double;
‏ sexes often separate, ♂ often smaller than ♀, eggs microscopic with shell often containing chitin.

‏12. Development direct or within a complicated life history.
———

‏The Pseudocoelomate Animals

‏Phylum Rotifera

‏Phylum Gastrotricha

‏Phylum Kinorhyncha

‏Phylum Nematoda

‏Phylum Nematomorpha

‏Phylum Acantocephala

‏Phylum Entoprocta

‏Phylum Loricifera

‏Phylum Priapulida
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‏Phylum Rotifera
‏•Derive their name from ciliated crown or corona, found at the anterior end of the animal which, when beating, gives the impression of rotating wheels.
‏•Most commonly found in freshwater environments there are also marine, terrestrial and parasitic species.

‏•The body is usually divided into a head, trunk and foot. The head bears the corona, the trunk has a thickened cuticle with ridged plates and spines for defense and the foot often bears 1-4 projections called toes, which are used for attachment.

‏•Rotifers are dioecious organisms (having either male or female genitalia) and exhibit sexual dimorphism (males and females have different forms). Many species are parthenogenic
——-

‏Phylum Gastrotricha
‏•Microscopic animals, ~ 65-500 mm long.

‏• There are marine and freshwater species and they are common in lakes, ponds and seashore sands.
——-

‏Phylum Kinorhyncha
‏•small, free-living, wormlike found in marine habitats.

‏•named for their mode of locomotion - they pull themselves along by rings of recurved spines on their heads.

‏•Most are < a millimeter long.

‏•Adults have spiny heads, spineless necks, and 11 trunk segments. Their bodies are roughly triangular in cross section. The head can retract into the trunk, which is covered with cuticle plates.

‏•The cuticle between the plates is very flexible; in the retracted position, the neck plates close over the head. The dorsal plates bear movable median and lateral spines.
——-

‏Phylum Nematomorpha
‏“horsehair worms”
‏•~ 320 species

‏•"horsehair worms," a name that reflects the superstition that these worms arise from horsehair. The animals are free-living as adults but as juveniles they are parasitic in arthropods.

‏•Adults are large and can be found in aquatic and marine environments. The adult female produces eggs which hatch and mature into juveniles. The juvenile then penetrates an appropriate arthropod host.

‏•For aquatic nematomorphs, beetles, crickets, roaches, and grasshoppers will serve as the host, while crabs serve as the host for marine forms.
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‏Phylum Acanthocephala
‏(spiny headed worms)
‏•known as spiny-headed worms due to a proboscis which bears rows of recurved spines, used for attachment to the intestine of their host.

‏•All are endoparasitic , living in the intestine of vertebrates, mainly birds and fishes. The intermediate hosts are either crustaceans or insects.
‏•They have no gut.

‏•If an intermediate host eats the egg, the larva hatches from the shell and bores through the gut wall into the hemocoel . The larva completes its cycle of development in the gut of the primary host when the intermediate host is eaten. The adult maintains position in the gut by attachment of the spiny proboscis to the mucosa.
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‏Phylum Loricifera
‏•They have not been known until the discovery of Cycliophora in 1995.

‏•very small (200-400 µm) and found living in the interstitial space between marine gravel.

‏•First discovered off the coast of France they are apparently widely distributed.
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‏Phylum Priapulida
‏•9 species of marine worms found predominantly in colder water.

‏• Most are predaceous burrowing mud with their mouth at the surface in order to capture passing prey.
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‏Phylum Nematoda: Roundworms
‏1.Body bilaterally symmetrical, cylindrical in shape
‏2. Body covered with a secreted, flexible, nonliving cuticle
‏3.Motile cilia and flagella completely lacking; some sensory endings derived from cilia present
‏4.Muscles in body wall running in longitudinal direction only
‏5.Excretory system of either one or more gland cells opening by an excretory pore, a canal system without gland cells, or both Pharynx usually muscular and triradiate in cross section.
‏2.Male reproductive tract opening into rectum to form a cloaca; female reproductive tract opening a separate gonopore
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‏Phylum Nematoda (roundworms)
‏•Nematodes move by contraction of the longitudinal muscles. Because their internal pressure is high, this causes the body to flex rather than flatten. No cilia or flagella are present.

‏•Some nematodes have specialized cells that excrete nitrogenous wastes; in others, canals or canals plus these specialized cells are present. Nematodes do not have flame cells
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‏Phylum Nematoda (roundworms)
‏•Most are dioecious. Fertilization takes place when males use special copulatory spines to open the females' reproductive tracts and inject sperm into them.

‏•The sperm are unique in that they lack flagella and move by pseudopodia, like amoebas.

‏Development of fertilized eggs is usually direct
——

‏Phylum Nematoda (roundworms)
‏•~90,000 nematode individual in a single rotting apple.

‏•~ 236 species living in a few cubic centimeters of mud.

‏•The number of described species is around 12,000, the true number may be closer to 500,000.

‏•Some species are generalists, occurring across wide areas and in many habitats; others are much more specialized.
‏•Many nematodes are free living and play critical ecological roles as decomposers and predators on microorganisms.

‏•But nematodes also include parasitic species, a number of which affect humans directly or indirectly through their domestic animals
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‏Some Nematode Parasites
‏•Nearly all vertebrates and many invertebrates are parasitized by nematodes. A number of these are very important pathogens of humans and domestic animals. A few nematodes are common in humans in North America
‏•Many others are usually abound in tropical countries
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‏Ascaris lumbricoides:
‏The Large Roundworm of Humans
‏•The large human roundworm (Gr. askaris, intestinal worm) is one of the most common worm parasites of humans
‏•Ascaris suum , a parasite of pigs, is morphologically similar and was long considered the same species.
‏•Females of both are up to 30 cm in length and can produce 200,000 eggs a day. Adults live in their host’s small intestine, and eggs pass out in feces.
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‏A, Intestinal roundworm Ascaris lumbricoides, male and female.
‏•Male (top) is smaller and has characteristic sharp kink in the end of the tail.
‏•The females of this large nematode may be over 30 cm long.
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‏Trichina Worm
‏•Trichinella spiralis (Gr. trichinos, of hair,+ -ella, diminutive) is one of the species of tiny nematodes responsible for the potentially lethal disease trichinosis.
‏•Adult worms burrow in the mucosa of the small intestine where females produce living young.
‏•Juveniles penetrate blood vessels and are carried throughout the body, where they may be found in almost any tissue or body space.
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‏Humans contract Trichinella (which causes the disease trichinosis) by eating raw pork containing encysted larvae. Mature female adults burrow into the wall of the small intestine. Live offspring are carried by the bloodstream to the skeletal muscles where they encyst.
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‏Pinworms
‏•Pinworms, Enterobius vermicularis cause relatively little disease, but they are the most common helminth parasite in human.
‏•Adult parasites live in the large intestine and cecum.
‏•Females are up to about 12 mm in length and migrate to the anal region at night