“Protozoans” and Porifera

“Protozoans”

•“proto” = earliest or original

•“zo” = animal

•Nonmonophyletic assemblage of unicellular organisms w/ “animal-like” characteristics

–Have no idea how they are related to each other or other organisms

•Morphologically diverse

•Mostly motile (highly diverse means of movement)

•Diverse means of nutrition

Phylum Chlorophyta

•Unicellular and colonial algae

•Have 2 flagella at some stage of life

•Mostly photoautotrophic

–Use sunlight to make own food by photosynthesis

•Probably sister to green plants

Phylum Retortamonada

•Unicellular, four flagella, lack mitochondria and Golgi bodies

•Intestinal parasites or free-living mostly in anoxic environments

•Giardia sp.

–Resembles two cells fused (ie. 2 nuclei & 8 flagella)

–Intestinal parasite common in N. America

–Contracted by drinking untreated stream water

Phylum? Euglenozoa

•Unicellular, 2 flagella attached to “apical reservoir”, mitochondria, microtubules in pellicle, many w/ chloroplasts and “stigma” (light sensing organelle)

•Heterotrophic (many autotrophic also)

•Euglena sp.

Phylum Ciliophora

•Unicellular, have cilia, micro & macronucleus, free-swimming or attached to substrate

•Heterotrophic, use cilia to generate currents used for feeding

•Very large group (#’s not size)

• Paramecium sp., Stentor sp., Vorticella sp.

Phylum Dinoflagellata

•Unicellular, many w/ 2 flagella in grooves, those lacking flagella move by pseudopodia

•Mostly free-living

•Heterotrophic, feed largely by phagocytosis

•Amoeba sp., Difflugia sp.

Stramenopiles

•Diatoms, Brown and Golden Algae

–aka. Phylum Chrysophyta

–Diatoms - split silica shells

•Very diverse (11,500 species)

•radial or bilateral symmetry

•Shell make “diatomaceous earth”

•Abundant in FW & marine ecosystems

•Important photosynthesizers/food source

–Most others generally marine

Evolutionary Relationships

•Taxonomy and systematics of “protozoans” is a complete disaster

–Many “species” described appear to be the result of morphological plasticity of single species

–Many morphologically similar lineages w/ dramatic genetic differences

•Even relationships of phyla are largely unknown

Ecological role of “Protozoans”

•Chlorophyta responsible for much of productivity in autochthonous (energy self supporting) systems (ie. Lakes and large rivers

–Can “overrun” streams and lakes due to nutrient enrichment

•Others feed largely on bacteria and fungi breaking down leaves in allochthonous (require energy input) systems (ie. most streams)

–Fed upon by microcrustaceans

–Important source of food for “detritivores”

Phylum Porifera

•Sponges

•>5000 species

•May not be monophyletic

•Mostly marine, a few freshwater (~300 worldwide)

•Sessile as adults, planktonic larvae

•No true tissues or organs

•Some w/ symbiotic algae

•Mostly filter feeders

Porifera morphology

•4 types of cells

–Pinacocytes – outer covering

–Porocytes – line pores

–Choanocytes – flagellated cells concentrated in chambers, generate current & collect food, produce gametes

–Ameobocytes – fill space (mesohyl) b/w outer covering and pores/chambers, distributes nutrients & wastes, secretes skeleton, produce asexual buds

Porifera morphology (cont.)

•Large range in number of pores and complexity of canals (increase in complexity = increase in relative surface area, larger body size)

•Collagen skeleton surrounding siliceous spicules

Porifera Reproduction

•Sexual

–Sexes separate (dioecious), may switch from year to year

–Gametes produced by choanocytes, sperm released into water, filtered by females

–Fertilized eggs retained for development

–Planktonic, flagellated larvae released

–Settle on substrate & attach

•Asexual

–Regeneration

–Gemmules – dedifferentiated cells covered w/ 3 collagen layers

•Resist drought, heat, cold

North American FW sponges

•27 species north of Mexico

•All in class Desmospongiae (99% marine)

–Also contains commercial sponges

•NA FW sponges mostly in Family Spongillidae (25 species)

–Spongilla sp.

Ecology of NA FW Porifera

•Attach mostly to hard substrate (rock, logs, plants), some on mud

•All filter feed detritus and microorganisms

•Many w/ green algae symbionts

–Algae provide organic C & O₂

–Sponge provide habitat & CO₂ for algae

•Some aquatic insects feed/live almost exclusively on FW sponges

–Spongilla flies