How do the acoelomates fit in?

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How do the acoelomates fit in?
Nemertea
Platyhelminthes
acoelomate
Complete digestive system
acoelomate
Closed circ. system
Ladder-like nervous system
Cnidaria
proboscis
Porifera
cephalization
protonephridia
organ level of organization
triploblastic
unknown common ancestor
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How do the Pseudocoelomates fit in?
Rotifera
Nematoda
the pseudocoelomates
Platyhelminthes
Nemertea
Cnidaria
Porifera
unknown common ancestor
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Pseudocoelomates
There are 9 different phyla that are classified
as pseudocoelomates. We are only covering 2
phyla
Nematoda
Rotifera
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Pseudocoelomate Characteristics
Organ level of organization
Tissues are organized to for organs which are
used to accomplish physiological functions
Triploblastic
3 Germ Layers endoderm mesoderm ectoderm
3 Tissue Layers gastrodermis mesoderm e
pidermis
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Pseudocoelomate Characteristics
false body cavity
ectoderm
ectoderm
pseudocoelom
mesoderm
Gut
endoderm
the pseudocoelom is lined by mesoderm on ONE
side only
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Pseudocoelomate Characteristics
the pseudocoelom
ectoderm

• is a closed, fluid filled cavity
• contains digestive, excretory, and reproductive
  structures
• the fluid within acts as a circulatory system
• the fluid within acts as a hydrostatic skeleton
  against which the muscles work

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Pseudocoelomate Characteristics
Bilateral Symmetry

• with anterior and posterior ends

Cephalization

• concentration of sensory organs in the head of
  the animal

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Pseudocoelomate Characteristics
Digestive System

• complete (they have an anus!)
• some regional specialization

Circulation System

• no system (or organs)
• performed by the pseudocoelom fluid

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Pseudocoelomate Characteristics
Eutely

• each individual of a species has the same of
  cells
• growth occurs by cells getting bigger rather
  than dividing

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Phylum Nematoda

• the roundworms

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Physiology

• Life Style
• Free-living
• parasitic
• Digestion
• complete system (have an anus)
• some regional specialization (e.g. an esophagus)

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Physiology

• Skeletal system
• fluid in pseudocoelom acts as a hydrostatic
  skeleton
• Cuticle
• covers body (secreted by epidermis composed
  mostly of collagen)
• functions as a primitive external skeleton

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Physiology

• Movement
• longitudinal muscles ONLY
• (results in whiplike motion)
• No external/internal cilia
• ? even sperm dont have flagella

http//www.devgen.com/devpage/largeimage/wild.html
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Physiology

• Nervous system
• cephalization, cerebral ganglia
• dorsal and ventral nerve cords

• Circulatory system
• No system (no organs)
• performed by fluid in pseudocoelom

• Excretion
• Renette glands

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Physiology

• Reproduction
• Sexual
• usually dioecious
• often the sexes are sexually dimorphic
• (males and females look different)

Males often have a spicule at the end of their
tail used to insert their sperm into the female
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Physiology

• Reproduction
• Sexual
• usually dioecious
• often the sexes are sexually dimorphic
• internal fertilization
• males have ameboid sperm

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Ecology

• There are gt12,000 species that are found in
  almost all habitats (marine, freshwater,
  underground, inside plants and animals, etc).
• They are also incredibly abundant. For example
• a m² of soil may contain gt4 million nematodes
• a decomposing apple may contain gt90,000
  nematodes of a single species

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Ecology

• Many nematodes are important parasites of both
  plants and animals.

parasite of soybean plants
parasite of tomato plants
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Parasites

• Eye worm (Loa loa)
• transmitted by fly bites
• larvae go through bloodstream
• adults live in subcutaneous tissue

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Parasites

• Intestinal roundworm (Ascaris)
• transmitted by contaminated food
• adults live in small intestine
• its estimated that 20 of worlds population is
  infected (1.3 billion people)

this intestine was completely blocked
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Parasites

• Guinea worm (Dracunculus medinensis)
• transmitted by infected copepods in drinking
  water
• larvae move into the body cavity
• female adult migrates to the subcutaneous
  tissue, causes an ulcer/blister, and releases
  eggs through hole when host comes in contact with
  water

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Parasites

• Guinea worm (Dracunculus medinensis)
• traditionally removed by winding the worm around
  a matchstick over the course of several days
• this may be the basis for the Caduceus symbol
  used in the medical field

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Parasites

• Trichinella spiralis
• causes Trichinosis
• transmitted by eating undercooked pork
• juveniles encyst within host muscle cells

juvenile
Host muscle cell
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Parasites
Heartworms (Dinofilaria immitis)
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Ecology

• The study of the model nematode C. elegans has
  resulted in important discoveries in genetics and
  development.

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Phylum Rotifera

• the rotifers

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The wheel animals
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Physiology

• Feeding
• have a crown of cilia called a corona
• the corona creates a
• current to bring food into
• the mouth

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Physiology

• Feeding
• have a specialized feeding structure called the
• mastax-trophi complex

modified jaws within the mastax
a modified muscular pharynx
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Looking down into the corona.
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Physiology

• Some of the trophi (jaws)

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Physiology

• Life Style
• Free-living
• Digestion
• complete system (have an anus)
• some regional specialization (e.g. mastax-trophi
  complex)

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Physiology

• Skeletal system
• fluid in pseudocoelom acts as a hydrostatic
  skeleton

• Movement
• the corona
• pedal glands (produce adhesive), as well as foot
  and toe (spurs) for attachment to substrate

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Physiology

• Nervous system
• cephalization, cerebral ganglia
• dorsal and ventral nerve cords

• Circulatory system
• no system (no organs)
• performed by fluid in pseudocoelom

• Excretion
• protonephridia and flame cells
• cloacal bladder (collects wastes)

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Physiology

• Reproduction
• Sexual
• complex life cycle with different types of eggs
• usually dioecious but in some groups, males are
  absent (parthenogenesis)
• Parthenogenesis
• unisexual reproduction where females produce
  offspring from unfertilized eggs (virgin birth)

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Physiology

• 2 types of eggs amictic mictic

Amictic eggs

• diploid (mitotically produced)
• cant be fertilized
• develop into diploid, amictic females

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Physiology
Mictic eggs

• haploid (meiotically produced)
• produced after some sort of environmental
  stimulus (eg. high density, change in
  temperature)
• if unfertilized, develop into haploid males
• if fertilized, secrete a thick, protective shell
  until the environment is favorable again, after
  which they develop into diploid, amictic females

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Ecology

• There are 1500 species. Although they are found
  mainly in freshwater habitats, there are a few
  marine rotifer species and a couple of species
  are even found in mosses!
• Because of the reduced role of males in
  reproduction, most males are incapable of feeding
  and do not even have a digestive tract (they are
  just there for sperm delivery!).
• Males have never been recorded in Bdelloid
  rotifers. This means they havent had sex in
  millions of years!

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Here are some of the other pseudocoelomate phyla
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Kinorhyncha
Loricifera
Priapulida
Nematomorpha
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Acanthocephala
Gastrotricha
Entoprocta
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How do the Pseudocoelomates fit in?
Rotifera
Nematoda
mastax-trophi
no cilia
corona
longitudinal muscles only
pseudocoelom
Platyhelminthes
Nemertea
Cnidaria
complete digestive system
Porifera
organ level of organization
triploblastic
unknown common ancestor