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Animalia►
ALL PHYLA BEING UPDATED:
July-December 2010
An Introduction To
The Study of Invertebrate Zoology
Kingdoms: Protista & Chromalyeolata
(Contact) CONTENTS
CLICK on underlined file names and
included illustrations to enlarge:
Invertebrate zoology is a biological discipline that
involves the study of invertebrates. Although
vertebrates possess many characters in common with invertebrates they are
distinguished by possessing a backbone.
Invertebrates lack a backbone.
Invertebrates comprise over 95 percent of all animal species and
certainly more than that percentage in animal biomass. They have been extensively used in
biological researches of heredity, embryology and regeneration. They also have had great practical
importance related to insect damage, the causes of human and animal disease
and directly as food, pearls, buttons, etc. Zoology may also be divided further into other
principal categories such as: Arthropodology = The study of
arthropods, including Arachnology (spiders & mites), Entomology (insects)
and Carcinology (crustaceans). Malacology
= The study of mollusks. Invertebrate
Paleontology = The study of extinct invertebrates. For a classification of Invertebrates as
treated herein please see Table 1. However, the principal groups may also be
noted as follows: Arthropoda -- insects, arachnids, crustaceans Nematoda -- round worms Mollusca -- squid, snails, bivalves Annelida -- segmented worms (earthworms, leeches,
polychaetes) Nemertinea -- ribbon worms Platyhelminthes -- flat worms Rotifera -- wheel animals Acoelomorpha
(controversial phylum: probably Platyhelminthes) Ctenophora -- Comb jellies Cnidaria -- jellyfishes, corals, sea
anemones, hydras Porifera -- sponges Echinodermata -
starfishes, sea urchin The arrangement of the various subgroups is based on
ever increasing complexity and presumed evolution of the most
primitive [(e.g., Protista (Protozoa)] to the more advanced organisms. Previous names of groups is included in
parentheses. There continues to be
wide disagreement on classification, and although further rearrangements are
expected as more biological and biochemical data are forthcoming, the
presented design should enable identification of major orders, families and
genera. The Protista (Protozoa) are included herein as a primitive precursor
group. Emphasis has been placed on
morphological and behavioral characteristics that are easily discernable, and
a simple diagrammatic style suitable for lecturing is used for most of the
illustrations. A binocular microscope with a 20X magnification is advisable
for those wishing to view living and preserved specimens. Greater detail on a particular group or
species may be found by referring to publications listed in the Bibliography or through Internet searches. --------------------------------------- Kingdom: PROTISTA (Protozoa) -- unicellular
microbes, plankton Phylum: Sarcomastigophora , Class:
Rhizopoda (Sarcodina)
[Mycetozoa have been included in the Myxomycetes or Amoebozoa of Mycology] The above differ also in their nuclear content. Foraminifer and Radiolara use asexual
reproduction. Flagella also occur in
the Sarcodina. There are many that
form symbiosis with algae. For
example, Zoochlorellae are Heliozoa with green algae; Zooxanthellae are
Radiolaria with yellow algae. Their importance ranks high. Endomoeba histolytica is a notorious intestinal
parasite and they serve as an important link in the food chain. The Protista that have been called Protozoa, or "First Animals" are more like the early
primitive animals than any other living forms. They have changed less than other groups. They are usually single-celled animals
that may exit in a colony. But each
individual cell retains its independence.
Their simplicity is often deceiving.
Amoebe, for instance, do all the basic functions as humans. However, the cells of Protozoa are so
complex that they have frequently been regarded as "acellular." There are all grades of cellular
differentiation from very primitive as in amoeba and advanced as in the
higher ciliates and flagellates.
There are definite openings for the taking of food developed. Locomotor structures appear and
contractile structures show up, which function as muscle fibers. The bases of the cilia and flagellae are
connected. Different grades of
reproduction occur from binary fission, complete sexual differentiation and
an alternation of sexual generations.
Protista have reached the point of multicellular organization. Flagellates are shown to be the most
developed and it is believed that they resemble the original stock group that
gave rise to both plants and animals.
At one time all Protista were believed to have evolved from the
flagellates. The Class Rhizopoda (Sarcodina) is
characterized by pseudopodia, which are organelles that are not true
organs. They serve in locomotion and
food getting. The cytoplasm of the
cell is not provided with many visible structures that possess specific
functions. Amoeba
proteus is a common fresh water rhizopod that occurs in calm,
semi-stagnant water. It is
microscopic in size and its form is indefinite.
Ingestion
& Digestion of Food.-- The cytoplasm
of A. proteus consists of two parts: (1) a plasmagel that
includes a clear layer and an outer portion of endoplasm, and (2) a plasmasol, which is a fluid or the inner
endoplasm. The organism is holozoic, taking in solid food consisting of algae
(diatoms) and other protozoa into its body.
The food is captured by the pseudopodia, and a food cup is formed that
engulfs the food bringing it inside in a food vacuole. Another means of feeding occurs where the
food slips past the cell membrane and thereby enters the cell. There is no vacuole formed in this
type. Digestive enzymes diffuse into
the vacuole and dissolve the food. Indigestible
portions are left in the vacuole.
Protein and carbohydrate enzymes are present in abundance, but there
are few fat enzymes. Egestion is
accomplished by the vacuole migrating to the edge of the amoeba and
eventually becoming located on the outside of the organism. Amoeboid Movement.--The plasmagel
and plasmasol are interchangeable, the former holding the latter under some
pressure. When the plasmagel weakens
or converts to plasmasol anywhere on the animal, the pressure forces the
plasmasol out into a pseudopodium.
The plasmasol sets into a gel all along the edges of the pseudopodium
in the form of a tube. The posterior
end of the cell then crumples up while converting plasmagel to plasmasol so
as to form the new extension. Circulation is
accomplished by movements of the animal itself, and respiration and excretion
are simple diffusions through the cell membrane. The Contractile
Vacuole is usually located at the posterior end of the amoeba. This is a water regulating mechanism that
pumps out water that moves into the cell by osmosis. There is an incidental expulsion of water
products. With an increase in the
salt concentration of the medium the contractile vacuole slows down and
finally stops. A reduction of salt
concentration results in a reactivation of the vacuole. Support &
Protection.-- There is little support needed in a suspended animal
like Amoeba, and there are no protective mechanisms. However, when unfavorable environmental
conditions occur Amoeba forms a cyst that can resist drying,
temperature extremes, etc. Sensitivity &
Conduction.-- Amoeba behaves as if it had a nervous
system, which it does not. A stimulus
applied at one point on the animal body may cause any other portion to
react. The animal perceives and
responds to environmental changes.
There is a positive response to food and weak light, and a negative
response to all other stimuli. It
generally responds in some way to light, temperature, touch and chemical
reactions. There are no visible
sensory or motor apparatus in the cytoplasm, but Amoeba is regarded as
being generally sensitive. Reproduction is entirely asexual being
effected by binary fission (cell division).
Size determines when A. proteus will reproduce, which is
usually 150 microns. Sexual processes
doe occur within the class but not in this genus. ------------------------------------ In the Phylum Sarcomastigophora Class Mastigophora (Flagellata) movement is
primarily by means of a flagellum.
Amoeboid stages may occur in some phase of the life cycle,
however. But adults always move by
the flagellum. When parasitic they do
not form spores. Nutrition is
holozoic, saprophytic or parasitic.
The Subclass Phytomastigina include green flagellates while
Zoomastigina are the colorless flagellates. The Phytomastigina includes
the genus Euglena.
These animals occur primarily in fresh water and an
abundance of them may produce a green scum.
Their size varies from 25-500 microns and the body wall is more rigid
than that of the amoebae. There is a
rigid, grooved wall or pellicle present, however
the ecto- and endoplasm are not well defined. Nutrition is holophytic where the
animal manufactures it own food by photosynthesis. But in darkness it will live on dissolved nutrient material and
thus is saprophytic. Food is stored
in paramylum bodies, and pyrenoid bodies occur in the center of the
chloroplasts, which serve to regulate them.
In darkness chlorophyll disappears from the cell. Circulation, excretion and respiration are
the same as in Amoeba proteus. Contractile vacuoles are located around the reservoir
whose function is to serves as exit to the vacuoles. Locomotion is by movements of the
flagellum. The flagellum has a
central core and is spirally wound with cytoplasm. The flagellum separates into two extension in the reservoir and
terminates in basal bodies.
As for sensitivity, there
is an eyespot, which is positive to weak or moderate light but negative to
strong light or arkness. Conduction
is like Amoeba. The
basal bodies serve as a coordinating mechanism because their removal
discoordinates the flagellum.
Reproduction is asexual with longitudinal binary fission. All parts are regenerative and there is no
sexual reproduction in Euglena although others of the class do
show it. Cyst formation occurs to
withstand adverse environmental conditions.
Some species in the Phytomastigina order Dinoflagellata
have an armor plate (cellulose armor) that
is occasionally shed and replaced.
The order is a large group of importance in marine habitats as
plankton. Dinoflagellates produce the
"Red Tide" in oceans that results in
widespread fish kills. The flagella have been termed "Frog Flagella" that are diagrammed as
follows:
In the Subclass Zoomastigina nutrition
is holozoic, saprophytic and parasitic.
The animals are colorless. The
flagella are very numerous and their arrangement is anterior with one
flagellum extended anteriorly and the other trailing. They may be fastened to the side of the
organism by an undulating membrane.
Several genera of the Zoomastigina are of great importance
to humans and animals because of their parasitic habits. Trypanosoma
causes "African Sleeping Sickness",
Trichomonas is a parasite of humans and
animals, Leishmania causes a skin
disease known as "Oriental Sore,"
and Giardia is a severe human intestinal
parasite. Also of importance is that
species may also produce oils instead of paramylum, which results in
foul-smelling and foul-tasting water.
On the other hand, termites possess a Zoomastigina symbiont that is of
mutual benefit. Phytomastigina
have a well-developed and pronounced colonial arrangement, which is true also
of the Zoomastigina but not as pronounced.
The Phytomastigina genus Pandorina has
16-32 cells while Volvox has hundreds of
cells in a gelatinous matrix. Any division
of labor limits the boundary between colonial organisms and multicellular
organisms. Volvox may be
sometimes regarded as multicellular, but reproductive cells in Volvox
function only to reproduce the organism.
Species in the order Protomonadina possess
a funnel-shaped collar similar to cells that are found in the Porifera.
Sexual reproduction in the Phytomastigina is especially
prevalent. Isogametes of identical
appearance and behavior are formed or heterogametes may be the case as in Volvox. ------------------------------------ All members of the Phylum: Apicomplexa (Sporozoa) are parasitic, and all produce spores at
some stage. There are no locomotory
organelles in the mature stage, although the immature forms may possess
them. Life cycles vary from simple to
complex. The incitant of malaria,
Plasmodium vivax, has one of the
most complicated life cycles. There
are alternates of sexual with asexual reproduction. Malaria is considered to be one of the most important diseases
of humans and it also affects animals extensively. Its life cycle is as follows:
Other important diseases found in
the Apicomplexa are Texas Cattle Fever, Nosema (affecting honeybees and silkworms) and Coccidiosis (in chickens). ------------------------------------ Please see following plates for Example Structures of the
Protista: Plate 65 = Kingdom: Protista --
Development characteristics Plate 1 = Different body shapes in
Rotifera. Plate 2 = Protista:
Sarcomastigophora: Rhizopoda: Amoebina: Amoeba proteus Plate 3 = Protista:
Sarcomastigophora: Rhizopoda: Foraminifera & Radiolaria Plate 4 = Protista: Mastigophora:
Eglenoidea: Euglena viridis Plate 5 = Protista: Mastigophora:
Phytomastigina: Volvocina: Volvox globator Plate 6 = Protista:
Sarcomastigophora: Mastigophora & Apicomplexa (Pandorina sp., Trichonympha
sp., Trypanosoma rhodesieusi & Plasmodium
vivax ------------------------------------ The Kingdom:
CHROMALYEOLATA (Infusoria) includes the ciliates and water molds.
Members possess cilia as locomotory organelles. There are two kinds of nuclei present in
some members (1) micronuclei and (2) macronuclei). Reproduction is by conjugation. This section will discuss the Superphylum: Alveolata Phylum: Ciliophora. In the Class Ciliata there
are two subclasses: Protociliata and
Euciliata. The Protociliata
(e.g., Opalina) is a very small group all members of which are
parasites or commensals. There are
neither macro- nor micronuclei but rather the nuclei are scattered and all of
the same size. There is no
conjugation and the group may be transferred to the Mastigophora. The Euciliata are the true ciliates where
macro- and micronuclei and conjugation are present. Cilia are common in many of the Ciliata and an undulating
membrane occurs in Paramecium's gullet. Membranelle exist that generally surround the food-gathering
portion of the body. These are
paddle-like and my also function in locomotion. Vorticella is a representative genus. Cirri or leg-like
tuft cilia are present in Euplotes which are fused cilia that look and act
like legs. These have been called
"crawling cilia." Nutrition is mostly holozoic and many are saprozooic,
living off the dissolved organic matter that is taken in through the body wall. Some species are also parasitic. Contractile structures or myonemes
are present, which serve as muscle cells. Such are found in the stalk of Vorticella.
Some species of ciliates occur in the digestive tract
of animals and actually assist in cellulose digestion. Balantidium
coli is present in humans. ------------------------------------ Paramecium is a
representative genus in the Euciliata that
occurs wherever bacteria are present.
They are slipper-shaped with a lateral grove called the "Oral Groove." These organisms are uniformly clothed with cilia and the body
surface has a pellicle. One large macronucleus and a small micronucleus
are present. There are two
contractile vacuoles at opposite ends each of which operates alternately with
the other. A plasmagel and plasmasol
are easily distinguishable and the average length is 200 microns. Feeding.-- Bacteria are the principal food of Paramecium. Feeding involves cilia that beat a current
of food into the oral groove and finally into the gullet. A modified group of cilia occur in the gullet
to form the undulating membrane.
At the base of the gullet there is a food vacuole,
which detaches like a bubble when it is full and then moves throughout the
body in a well-defined path. The path
of movement is first posterior, then anterior, and finally posterior with
termination in the anus.
There is a constant circulation of plasmasol, which
causes the food vacuoles to be carried around a cyclosis. The food vacuole is acid at first and
later becomes alkaline. Circulation.-- This is accomplished by cyclosis,
and simple diffusion takes care of excretion and gas exchange. Locomotion.-- The waving of cilia accomplishes
locomotion. These resemble short,
blunt flagella but they differ by their shorter length and numbers. Each cilium terminates proximally in a
basal body that is interconnected with all basal bodies in the organism. Support is given by the pellicle. Protection is furnished by trichocysts,
which simply serve as anchors while the cilia re waving food into the
gullet. There is no cyst formation in
Paramecium, the animal being hearty and can withstand extremes in
oxygen and carbon-dioxide concentrations. Sensitivity.-- Paramecium is indifferent
to light except for one species that has a green alga symbiont. Actually all the cilia may be sensory and
able to discriminate between edible and nonedible substances. Coordination.-- There is coordination between
the many cilia and may be brought about by the interconnections of their
basal bodies. The presence of an
"amotorium" or kind of central brain
is obscure. Reproduction.-- Paramecium reproduces by
binary fission.
Conjugation is
like that found in Ciliata and Suctoria.
It occurs only in individuals with a macro- and micronucleus. Two conjugating individuals become sticky
and pair. The micronucleus is
involved in genetic transfer.
Step I = The
micronucleus divides. Step II = A second division occurs (--4 haploid
micronuclei in each conjugant) Step III = Three micronuclei degenerate; the one
remaining divides again. Step IV = There is a mutual exchange of micronuclei
(one goes to mate and one remains behind) Step V = There is a fusion of two haploid micronuclei
to form one diploid micronucleus. Step VI = The
cells separate from one another and are termed "exconjugants." The macronucleus disintegrates. Post Conjugation in Paramecium Step I = 2N micronucleus divides to produce eight 2N
micronuclei. Step II = Four micronuclei enlarge to form macronuclei,
while four micronuclei remain unchanged. Step III = The cell divides to produce four cells, each
of which possesses one micronucleus and one macronucleus.
Step IV = The macronuclei then grow enormously by
forming the polyploid condition. They
apparently regulate all the vegetative processes in the cytoplasm. In asexual reproduction the micronucleus
always divides by mitosis while the macronucleus divides by splitting almost
in half. ------------------------------------ The Class: Phyllopharyngea, Subclass: Suctoria has cilia in immature stages and
adults possess tentacles. They
paralyze their prey and the suctorial tentacles
suck the prey dry.
Macro- and micronuclei and conjugation are
present. Adults are sessile and the
group occurs in both fresh and salt water.
Many are free living, some are commensals and a few are
parasites. They have little economic
significance. ------------------------------------ Please see following plates for Example Structures of the
Chromalveolata: Plate 7 = Chromalveolata:
Ciliophora: Ciliata: Paramecium multimicronucleatum Plate 8 = Chromalveolata:
Ciliophora: Ciliata: Nyclotherus sp., Opalina sp., Didinium
nasutum & Paramecium sp. Plate 9 = Chromalveolata:
Ciliophora: Ciliata & Phyllopharyngea (Euplotes patella & Ephelota
sp.) Plate 66 = Kingdom:
Chromalyeolata, Phylum: Ciliata -- Paramecium
structure ============== |
