Kingdom Chromista The Alveolata. Protozoan Biodiversity A guide to the major groups Species seen in...

Kingdom Chromista

The Alveolata

Protozoan Biodiversity

A guide to the major groupsSpecies seen in lab are marked with a

Alveolata

Alveolata All alveolates have tiny sacs (alveoli) beneath

the plasma membrane All single-celled Have tubular inner membranes (cristae) in their

mitochondria (Tubies). Three major taxa with very different adaptive

strategies Dinozoa

Dinoflagellates – some photosynthetic, others not Important in nearshore oceans

Apicomplexa (Mostly) medically important parasites; non-motile

Ciliophora Ciliates – conjugation

Dinoflagellates

Phylum Dinozoa = Dinoflagellata

Dinoflagellates Often classed with algae Cell complexity

Single cells or chains of cells. How are their cells organized?

Mesokaryotes – permanently condensed chromosomes Mitotic spindle located outside of the nucleus (which

remains intact during mitosis) What pigments do they possess?

Chlorophyll a, Chlorophyll c and Peridinin. What storage product is made?

Starch and oils.

Dinoflagellates Cell wall features? 

Most dinoflagellates are encased in plates of armor. Thick cellulose plates encased in vesicles beneath the

cell membrane

Some are “naked” and lack these plates Gymnodinium

2 flagella present. One trails behind One lies in groove around center of cell Cell spins slowly like a top as it swims

Ceratium

Gonyaulax: an armoured dinoflagellate. Cell wall is subdivided into multiple polygonal vesicles filled with relatively thick cellulose plates

A “naked” dinoflagellate. Cell wall does not have thickened cellulose armour plates.

Armored dinoflagellate: Know: cingulum, sulcus, epitheca, hypotheca, flagella

Dinoflagellates

Dinoflagellates Some have elaborate eyespots called ocelli, which

have a pigmented portion and a lens-like refractive portion.

Some have trichocysts, which are ejectile organelles similar to the nematocysts in Cnidarians. What other group of protists has these?

Ceratium

Ceratium

Note: nuclei with permanently condensed chromosomes

Dinoflagellates Mature dinoflagellates are haploid (1n)

Dikaryotic nuclei – 2 haploid nuclei Permanently condensed chromosomes

Reproduction Mostly asexual Reproduce by fission A few can reproduce sexually

Gametes formed by mitosis (not meiosis) because the cells are already haploid.

Gametes (1n) are motile Zygotes (2n) formed by fusion of gametes also motile

mei

osis

Dinoflagellates Ecology

90% are marine 10% freshwater About 50% are photosynthetic; the rest are heterotrophs

(parasites) Photosynthetic dinoflagellates are second only to

diatoms as primary producers in coastal waters. May be free-living or symbiotic

Zooxanthellae - symbionts of cnidarians and others Vital to the growth and survival of coral reefs

Zooxanthellae Dinoflagellate endosymbionts of animals and

protozoa Coral reef builders

Zooxanthellae Symbiotic dinoflagellates found in many marine

invertebrates Genus Symbiodinium Sponges, corals, jellyfish, Tridacnid clams and flatworms Also found within protists, such as ciliates, foraminiferans,

and colonial radiolarians.

Zooxanthellae

Zooxanthellae Endosymbionts of animals and protozoa In coral polyps zooxanthellae are found in the

second layer of cells below the epidermis; one algal cell per animal cell.

Important components of reef building corals* Provide them with nutrients Remove waste Contribute to the production of calcium carbonate

skeletons

* More about this when we study Cnidarians

Zooxanthellae Mutualism

Host organism ingests the dinoflagellate and incorporate it into its own tissues without harming it.

Dinoflagellate divides repeatedly, and begins to manufacture carbohydrates which are provided to the host.

Many corals get all their food from the zooxanthellae; build reefs much faster with the dinoflagellates present in their tissues.

Zooxanthellae

Zooxanthellae Recall observations on zooxanthellae in tissues of Aiptasia anemones from S219 aquarium

Cassiopeia jellyfish (aquarium) also have zooxanthellae and typically rest upside down in shallow mangrove beds. This provides maximum sun exposure for symbionts Jellyfish also feeds on passing zooplankton Blue structures are vesicular appendages that hold

zooxanthellae

Aiptasia anemone with zooxanthellae

The upper layer of the Acropora sp. is the epidermis. The lower layer is the gastrodermis. Within the cells are round to oval golden spheres. These are the zooxanthellae.

Cassiopeia, the Upside-Down Jelly or Mangrove Jelly (Figure 7), generally lies on upside-down on the substrate where it tends its internal garden of zooxanthellae, which give it a greenish color.  While there, the bell margins pulsate creating a current across the oral surface where plankton and other particles are subdued by nematocysts and caught in a gelatinous coating.  The captured particles are carried to the mouth or to other secondary mouths that occur on the oral arms.  These are animals of warm, shallow water of the West Indies, the Pacific, and the Indian Oceans.

Coral Bleaching = loss of zooxanthellaeCauses – discussed with Cnidarians

Bioluminescent Dinoflagellates

Bioluminescence

Some dinoflagellates are capable of producing light - bioluminescence Molecules made by the organism produce light in

a chemical reaction. Luciferin and luciferase

Same reaction that occurs in fireflies

Health Issues Many dinoflagellates produce neurotoxins

Poisons that injure the nerves of marine life that feed on the dinoflagellates

May cause massive kills of fish and shellfish, as well as other forms of marine life.

If animals containing these toxins are eaten by humans, the result may be illness or even death. Neurotoxins affect muscle function, preventing

normal transmission of electrochemical messages from the nerves to the muscles by interfering with the movement of sodium ions through the cellular membranes

Health Issues These toxins in the water can blow inland in sea

spray and cause temporary health problems for people who live near the coast.

The toxin from Gonyaulax catenella is so toxic that an aspirin sized tablet of the poison could kill 35 people; it is one of the strongest known poisons

Neurotoxins Saxitoxin - most common dinoflagellate toxin

100,000 times more potent than cocaine Found in North American shellfish from Alaska to

Mexico, and from Newfoundland to Florida Brevitoxin

Causes fish kills May also cause poisoning in humans when it accumulates

in the tissues of shellfish Red Tides

Population explosions of dinoflagellates that can color the water red.

Shellfish contain high levels of toxins during these times

Gonyaulax and views of red tidesA red tide results from a population explosion of dinoflagellates (an algal bloom). Cell densities are so high that they turn the water a red color.

Boat

Bioluminescent Red Tide

Noctiluca

Noctiluca - a bioluminescent marine dinoflagellate; also causes red tides. Can feed heterotrophically by using its longer posterior flagellum to capture prey.

Neurotoxins Humans may be poisoned:

By eating contaminated fish - Ciguatera Or by eating shellfish, such as clams or mussels -

paralytic shellfish poisoning or PSP. Poisoning is serious but not usually fatal.

Lethal concentrations lead to death from respiratory failure and cardiac arrest within twelve hours of consumption

Old rule of thumb was that shellfish should only be eaten during months with an "R" in them, and not during May to August. Summer brings runoff of nutrients and blooms of dinoflagellates. NOT VERY RELIABLE!

Pfiesteria piscicida Ulcers on fish caused (?) by PfiesteriaNote the long flagella

Pfiesteria and some of its relatives cause death in fish and respiratory and neurological complications in humans

Ciliates

Phylum Ciliophora

Functional groupings of ciliates Holotrich- uniform ciliation Heterotrich- possess membranes &/or cirri Peritrich- cilia only around the cytostome Colonial-living in colonies Suctorian- a clade of Ciliophora possessing

hollow feeding tentacles

An assortment of freshwater ciliates- biodiversity!

This figure shows 167 species- about 9500 species are known

Ciliophora (ciliates)

A major clade within the Alveolates. Synapomorphies* of ciliates include:

Ciliated pellicle and associated kinetodesmata Dimorphic nuclei Conjugation

Primarily holotrophic - few parasitic. Many can form cyst stage (resting stage).

*Shared, derived characteristic – something NEW!

c

Ciliates

Paramecium

Paramecium bursaria

Stentor coeruleus

Vorticella

Stylonychia

Cirriciliary organelles used for food handling and locomotion- form membranes or bundles

Ciliophora

Euplotesa heterotrich ciliate showing complex cirri used for feeding and locomotion

Euplotes

Spirostomum

Didinium

http://www.uga.edu/protozoa/portal/images/movies/didinium.mov

Acineta

AcinetaSphaerophrya

Acineta

Balantidiasis – Balantidium coli Most cases are asymptomatic. 

Clinical manifestations, when present, include persistent diarrhea, occasionally dysentery, abdominal pain, and weight loss. 

Symptoms can be severe in debilitated persons.

Diagnosis is based on detection of trophozoites in stool specimens or in tissue collected during endoscopy.  Repeated stool samples necessary to find trophozoites

Treatment: Tetracycline with metronidazole and iodoquinol as alternatives

Trophozoites

Cyst

B. coli trophozoites

Ichthiopthirius multifilis (Ich)

Common parasite of freshwater and marine fishes

Trophozoite burrows in skin

Mature trophozoite leaves fish and encysts.

Multiple mitoses produce hundreds of “swarmers” that reinfest fish.

Ich trophozoite in fin of freshwater drum

M. C. Barnhart