DIVERSITY OF PROTOZOA Important groups of Protozoa


DIVERSITY OF PROTOZOA Important groups of Protozoa (2) Order Volvocida (Phylum Chlorophyta) •
CHLOROPHYTA is currently considered as a complex phylum of green algae •
Most species are non-motile, hence classified under green algae •
However, some are motile (order Volvocida) and included in Protozoa (! the systematic position of Chlorophyta is still uncertain !) 

Volvocida •
Key characteristics:

photoautotrophic (having chloroplasts)

Having two, four or eight flagella without mastigoneme Cup-shaped chloroplast Starch granule Volvocida •
Key characteristics:

Having both asexual and sexual reproduction & having haploid-dominant life cycle

Most colonial (living in colonies), some solitary Chlamydomonas 

•
the colony consists of specialized cells: somatic cells (with flagella) and gonidia (without flagella, for asexual and sexual reproduction) Volvox sp 

Importance of Volvocida •
although widely considered closely related to plants, instead of animals, colonial Volvox might be the clue of how multicellular organisms evolved Phylum Alveolata •
This phylum comprises three sub-phyla: a.
Ciliophora b.
Dinoflagellata c.
Apicomplexa (or Sporozoa) 

Phylum Alveolata

having pellicular aveoli = a system membranous vesicles located beneath cell membrane 5a Subphylum Ciliophora •
Key characteristics:

Having trichocysts

Having surface cilia, some arranged in longitudinal rows

Two types of nucleus: micronucleus and macronucleus 

Ciliophora

having trichocysts that can discharge threat-like shaft (for defense) 

Ciliophora’s contractile vacuoles http://www.youtube.com/watch?v=vk5NFSvp8lY 5b Ciliophora

Asexual reproduction: transverse binary fission

Sexual reproduction by conjugation

most solitary, free-living; some colonial and sedentary 



most are solitary, free-living; some are colonial and sedentary 

Importance of Ciliophora •
Many are ecto-commensals or endo-commensals •
Some live mutualistic in gut of termites, contributing in the digestion of cellulose •
Some species are parasites in fish, mammals and invertebrates 5c Subphylum Dinoflagellata

4000 species, marine and freshwater

One-half of those are photoautotrophs: chloroplasts with xanthophyll pigment, thus colored red-brown or golden brown; while the remaining are heterotrophs and colorless 

Dinoflagellata

Two flagella: transverse flagellum and longitudinal one

Complex cytoskeleton (theca) containing cellulose in alveoli

Asexual reproduction: longitudinal binary fission Importance of Dinoflagellata

Photoautotrophic species: important primary producers in ocean

Some are responsible for red tides

Some can produce and release toxins into water, causing death of fish or food poisoning in humans 

Diversity of Actinopoda: (2) Heliozoa 

INTRODUCTION TO METAZOA Mutlicellular animals METAZOA Q: What are metazoans? A: multicellular, heterotrophic, motile eukaryotes •
Chapter provides an overview on the metazoans, with basic terms printed in Bold Please read before coming to next week’s lecture! 

PRIMITIVE METAZOANS o
Phylum PORIFERA o
Phylum PLACOZOA 

Phylum Porifera •
Porifera = “pore bearers” ; a.k.a sponges •
Over 8,000 species, mostly marine, only some freshwater Key characteristics of Porifera

Asymmetrical body, size greatly varied (from millimeters to more than one meter); solitary or colonial

Porous = having many pores on the bodies 

Body structure of Porifera •
Asymmetrical, with typical designs of aquiferous system: asconoid, syconoid, and leuconoid design ASCON SYCON LEUCON Body wall

Body wall with three layers: epithelioid (l p t bào ngoài), choanoderm (l p t bào lót thành xoang trung tâm), and mesohyl (t ng trung giao v i nhi u lo i t bào)

Two forms of body wall: cellular and syncytial body wall 

A Cellular body wall •
Epithelioid (pinacoderm): the layer of cells covering the body surface •
Mesohyl (connective tissue): archeocytes (ameboid cells), spongocytes, sclerocytes, etc •
Choanoderm: the layer of choanocytes (collared cells) Collared cells (resembling choanoflagellates) 

The mesohyl containing various types of cells secrete materials for the skeleton of sponges: •
Lophocytes produce collagen fibers •
Spongocytes produce polymerized collagen fibers (spongin) •
Sclerocytes secrete mineralized spicules 

The mesohyl (2) Two types of cells function as reproductive cells: •
Spermatocytes produce sperms •
Oocytes produce eggs 

ASCON SYCON LEUCON Distribution of choanocytes in different body designs B Syncytial body wall •
Body wall lacks pinacoderm layer, but has a syncytium (large cytoplasm with multiple nuclei); syncytium usually three-dimensional and web-like •
Body wall also lacks choanoderm, but has choanosyncytium (consisting collar bodies with collar and flagellum but without a nucleus) 

Syncytial body wall Nutrition of Porifera •
Filter feeding •
Food digested in choanocytes by endocytosis (phagocytosis) 

Nutrition of Porifera •
Many species are symbiotic with green algae, dinoflagellates, cyanobacteria Reproduction of Porifera

Asexual reproduction: clonal reproduction

Sexual reproduction (some are hermaphrodites), still lacking genital organ 
Oviparous: spawn eggs before or immediately after fertilization 
Viviparous: keep embryos in the maternal body, and only release juveniles or larvae 

Key characteristics of Porifera

Asymmetrical, size greatly varied (from millimeters to more than one meter)

Specialized for filter feeding

Porous = having many pores on the bodies

Lacking nerve cells and nervous tissue What are primitive features of Porifera? 

Primitive characteristics of Porifera •
Simple asymmetrical body form •
No separation between the environment and internal body •
Differentiation of tissues still low; lacking muscle tissue and nervous tissue •
Endocytosis Diversity of Porifera •
Subphylum Symplasma (Hexactinellida), a.k.a glass sponges (having syncytial body wall) •
Subphylum Cellularia (having cellular body wall)

Class Demospongiae

Class Calcarea 

Hexactinellida Euplectella sp Class Demospongiae Haliclona sp 
... Importance of Dinoflagellata

Photoautotrophic species: important primary producers in ocean

Some are responsible for red tides

Some can produce and release toxins into water, causing death of. .. stiff, needle-like pseudopodia (= axopodia)

free-living, planktonic Diversity of Actinopoda: (1) Radiolaria 

Diversity of Actinopoda: (2) Heliozoa 

INTRODUCTION TO METAZOA... the layer of choanocytes (collared cells) Collared cells (resembling choanoflagellates) 

The mesohyl containing various types of cells secrete materials for the skeleton of sponges: