Animal Kingdom Part II

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Animal Kingdom II
Nematode through Mollusk
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Nematoda

• The Round Worms
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Free Living Worms

• Most nematodes are free living (non-parasitic)
  and can live in almost any habitat
• Some are parasitic.

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Parasitic Nematodes

• Ascaris lumbricoides is one of the best known of
  the parasitic nematodes.
• Males and females live in the intestines of
  humans where they graze on intestinal contents.

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Parasitic Nematode Larvae

• Eggs pass out with the feces and, if they
  contaminate food, are introduced to another host.
  
• The larvae hatch out in the intestine of the new
  host and then burrow through the walls to be
  carried by the bloodstream to the lungs.
• At the lungs they burrow through the alveoli and
  crawl up the trachea and down the esophagus.

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Parasitic Nematodes

• Larvae usually burrow out of the lungs at night
  and are unknowingly swallowed by the host.
• Occasionally larvae get lost and crawl up the
  esophagus and exit at the nose.
• In some areas of the world Ascaris is so common
  that a child is not considered to be part of the
  tribe until a larva is sneezed out and found in
  the bed.

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Body Cavity and Digestive System

• Nematodes have a pseudocoelom level of body
  development.
• This allows them to have a complete digestive
  system including a
• Muscular pharynx
• A thin, ribbonlike intestine
• A slit-like anus

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Pseudocoelom

• The cavity of the nematode pseudocoelom is small.
• It is mostly filled with an intestine and
  oviducts (females) or testes (males).

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True Sex Organs

• Most nematodes are either male or female.
• Nematodes have distinct male and female sex
  organs.
• The larger animals with the straight tails are
  females while thin ones with hooked tails are
  males.
• The female's genital pore is connected to a short
  vagina.

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True Sex Organs

• The vagina leads to a pair of uteri.
• At the end of each uterine segment, a thin
  oviduct can is found, followed by the threadlike
  ovaries.
• Eggs are produced by meiosis within the ovaries.
  They then move along the oviducts to the uterus.
• While some maturation of the eggs occurs within
  the oviducts, fertilization takes place in the
  uterus.

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The Nematode Anus and Reproduction

• The anus serves as both the excretory and
  reproductive pore for the male.
• The copulatory spicule is a hook-like appendage
  used to hold the female's genital pore open and
  is located near the edge of the anus.

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Cloaca

• At the posterior end of the intestine is the
  cloaca
• The cloaca serves as a common collecting area for
  fecal material from the intestine and sperm.

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Nematode Sperm

• Sperm are produced in the testes
• Nematode sperm are unusual because they are
  amoeboid (not flagellated).

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Nematode Nervous System

• A simple nervous system consists of a ring of
  nervous tissue around the pharynx that gives rise
  to dorsal and ventral nerve cords running the
  length of the body.
• The pharynx (throat) is the muscular tube that
  connects the nose and mouth to the larynx and the
  esophagus.

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Trichinosis

• Parasitic disease caused by the roundworm
  Trichinella spiralis.
• It follows the eating of raw or inadequately
  cooked meat, especially pork.

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Trichinosis

• The larvae are released, reach maturity, and mate
  in the intestines, the females producing live
  larvae.
• The parasites are then carried from the
  gastrointestinal tract by the bloodstream to
  various muscles.

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Trichinosis

• It is estimated that 10 to 20 of the adult
  population of the United States suffers from
  trichinosis at some time.
• In many people the disease exhibits no symptoms.

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Trichinosis

• In others it causes diarrhea and other
  gastrointestinal symptoms as the worms multiply
  in the digestive tract.

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Trichinosis

• When the larvae circulate through the
  bloodstream, the patient experiences edema.
• (Edema is a condition of abnormally large fluid
  volume in the circulatory system or in tissues
  between the body's cells),
• Irregular fever, profuse sweating, muscle
  soreness and pain, and prostration.

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Trichinosis

• There may be involvement of the central nervous
  system, heart, and lungs.
• Death occurs in about 5 of clinical cases.
• Once the larvae have imbedded themselves in the
  muscle tissue, the cysts usually become
  calcified.
• Usually, the infestation usually causes no
  further symptoms except fatigue and vague
  muscular pains.
• There is no specific treatment.

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Mollusca

• Molluscs include all of the shelled creatures of
  the seashore except for barnacles which are
  arthropods.
• Molluscs are abundant in the region between high
  and low tide and are a major feature of all rocky
  ocean shores.
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Mollusca

• However, molluscs dont only include the shelled
  creatures.
• Octopi, squid and even pill bugs are also members
  of this diverse phylum.

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Soft Bodies

• The word mollusc comes from Latin meaning "soft,"
  a good description of the group's fleshy bodies.
• Of course, in a world filled with predators, a
  soft body is easily eaten.

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Evolution of the Shell

• The early molluscs that happened to develop hard
  shells not only managed to survive but also
  succeeded in launching an ever-escalating 500
  million year old battle between themselves and
  their predators.

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Mollusc Symmetry

• Molluscs are bilaterally symmetrical with an
  anterior head.

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Classification--Gastropods

• Gastropoda
• This largest and most successful class of
  mollusks contains 35,000 living species including
  snails, periwinkles, conches, whelks, limpets and
  sea slugs.

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Classification--Bivalve

• Bivalvia
• Members of this class such as clams, cockles,
  mussels, oysters and scallops, are an important
  food source for humans fish, and shore birds.

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Classification--Cephalopods

• Cephalopoda
• The most highly organized group of mollusks
  includes squids, octopuses, cuttlefish, and
  nautiluses.

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Classification--Polyplacophora

• Polyplacophora
• Members of this class are commonly referred to as
  chitons.
• These rock-clinging marine molluscs are abundant
  on rocky coasts throughout most of the world.

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Mollusc Structure

• During development, all modern molluscs undergo
  torsion.
• This is where the mollusc body twists so that the
  mantle cavity, and the organs it holds, come to
  rest over the head.
• This is so the organs face the incoming current.

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The mollusc shell

• Mussels, winkles, and snails are soft bodied
  animals with a hard external shell.
• Sea hares and cuttlefish either have an internal
  shell or have lost their shell in the course of
  evolution (nudibranchs).

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Mantle

• The mantle is a soft, fleshy sheet of tissue that
  surrounds the molluscs body and lines the inner
  surface of the shell.
• It secretes the materials that form the shell
  from the marginal glands and provides the
  periostracum.

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Mollusc Respiratory System

• Aquatic molluscs breathe by way of gills.
• Terrestrial molluscs have evolved a modified
  lung in a cavity associated with the mantle.

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The Periostracum

• The periostracum is the organic layer secreted by
  the inner surface of the outer mantle.
• It is a substrate upon which calcium carbonate
  (CaCO3) can be deposited.
• This is how the mollusc builds its shell.

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The Mollusc Circulatory System

• Molluscs evolve the first true circulatory
  system.
• Multicellular animals do not have most of their
  cells in contact with the external environment.
• Therefore, they have developed circulatory
  systems to transport nutrients
• oxygen
• carbon dioxide
• metabolic wastes.

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The Circulatory System

• Components of the circulatory system include
• blood a connective tissue of liquid plasma and
  cells
• heart a muscular pump to move the blood
• blood vessels arteries, capillaries and veins
  that deliver blood to all tissues

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Mollusc Circulatory System

• Most molluscs have an open circulatory system
  with a three chambered heart
• However, cephalopods have a closed circulatory
  system with a four chamber heart!
• Arthropods and amphibians also have a three
  chambered heart.
• Fish have a two chambered heart.

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Three vs Four Chambers

• In a three-chambered heart, oxygenated blood and
  unoxygenated mix in the single ventricle.
• In a four-chambered heart there two
  ventricles.....no mixing AND pumps more, which is
  more efficient.

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Mollusc Circulatory System

• A heart pumps blood through vessels into a
  hemocoel.
• A hemocoel is a cavity that fills with blood.
• The blood then diffuses back to the circulatory
  system between cells.
• Blood is pumped by a heart into the body
  cavities, where tissues are surrounded by the
  blood.
• The resulting blood flow is sluggish.

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• Larger, active organisms have vessels to
  transport blood and one or more pumps to force
  blood through the vessels. In an open circulatory
  system, internal organs are bathed in blood,
  while in a closed system blood is always within
  vessels.

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Mollusk Digestive System

• The mouth usually leads into a chamber known as
  the pharynx (throat).
• The pharynx which usually contains a radula.
• A radula is a flexible, ribonlike structure
  consisting of numerous rows of minute teeth.

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Mollusc Nervous System

• Some molluscs are slow moving, and have no real
  head.
• Others, like the cephalopods, are active
  predators that have a head and sense organs.
• Molluscs have eyes and tentacles.

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Mollusc Life Cycle

• The primitive mollusc life cycle has 3 main
  stages.
• The eggs hatch into a tiny, swimming larva called
  a TROCHOPOHORE, which swims and eats using
  thousands of tiny hairs called cilia.

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Mollusc Larva

• In most snails the eggs hatch directly into a
  second type of swimming larva.
• These have a thin shell with
• An operculum (a plate which covers the opening
  of the shell)
• a muscular foot (like adult snails)
• Two ciliated wing-like structures either side of
  the head for swimming and feeding.

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Mollusc Summary

• Rasping organ called a radula which is a
  toothlike tongue present in most groups.
• Muscular foot used for locomotion and other
  tasks
• A sheath of tissue called the mantle that covers
  the body and can secrete the shell (if there is
  one)
• A mantle cavity that houses the gills or lungs.

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Mollusc Systems

• Molluscs have a respiratory system consisting of
  gills or lungs protected by the mantle.
• The mantle is made from calcium carbonate
  excretions.
• They have a three chamber open circulatory
  system.
• They have a three layer digestive system that
  includes an ectoderm, endoderm and mesoderm.

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Mollusc Summary

• Nervous systemThey have a system of ganglion and
  in the cephalopods it is fairly highly organized.
• Molluscs generally have individual sexes although
  some are hermaphrodites
• A calcium shell is present in most molluscs some
  molluscs have greatly reduced their shells, e.g.,
  squid while others have completely lost it,
  e.g., slugs, nudibranchs, and octopus

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