Lecture Marine Heterotrophic Protists

Protistan Groups

Ciliates

Sarcodines

Apicomplexans

Flagellates

Protistan Anatomy

Alveloates• The alveolates (meaning "with

cavities") - the presence of cortical alveoli, flattened vesicles packed into a continuous layer supporting the membrane, typically forming a flexible pellicle.

• In dinoflagellates they often form armor plates.

• Ciliates – very common protozoa with many short cilia arranged in rows, and two nuclei

• Dinoflagellates – mostly marine flagellates many of which have chloroplasts

• Some lack chlorophyll and are only heterotrophic, but are bioluminescent –Noctiluca = “night light”. Ingests particulate matter through phagocytosis.

• Some are parasitic on invertebrates, vertebrates and other protozoans.

Noctiluca

Dinoflagellates

Immobilising and eating metazooplankton.

Karlodinium armiger ganging up and munching on a polychaete larva (Berge et al. 2012)

Phylum Ciliophora • Ciliates, a large varied group of

protists, are named for their use of cilia to move and feed

• Multinucleate– Macronucleus – controls

metabolism, synthesis of organic molecules and development of the organism

– Micronucleus – function in sexual reproduction (conjugation) and give rise to the macronucleus after sexual reproduction.

Phylum Ciliophora • feeds on organisms via a

cytostome• Defensive and predatory

adaptations– Trichocysts – defensive– Toxocysts – toxic to

paralyze prey– Mucocysts

Tintinnids

• Bell animals• Planktonic ciliates• Common in open ocean• Ring of cilia surround

mouth (locomotion & catching food).

• Hard shell of protein.

Cytostome• A cytostome (from cyto-, cell and stome-, mouth) or

cell mouth is a part of a cell specialized for phagocytosis

• Food is directed into the cytostome, and sealed into vacuoles.

• ciliates and excavates have cytostomes.

• cytostome only constitutes the opening of the invagination at the surface of the cell. The rest of the invagination is classified as the cytopharynx

Ciliophoran Reproduction

Perkinsus olseni

Rhizaria• having no clear morphological distinctive

characters, but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods.

– Cercozoa – Various amoebae and flagellates, usually with filose pseudopods and common in soil

– Foraminifera – Amoeboids with reticulose pseudopods, common as marine benthos

– Radiolaria – Amoeboids with axopods, common as marine plankton

Cercozoans and radiolarians - have threadlike pseudopodia

• A newly recognized clade, Cercozoa, contains species among the organisms called amoebas

• Amoebas were formerly defined as protists that move and feed by means of pseudopodia

• Cercozoans are distinguished from most other amoebas by their threadlike pseudopodia

Polystomella strigillata

Bolivina subaenariensis – planktonic foraminifera approximately 1mm long.

Foraminiferans• are named for

porous, generally multi-chambered shells, called tests

• Pseudopodia extend through the pores in the test

• Foram tests in marine sediments form an extensive fossil record

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero

20 µm

Facts about Forams

• Shell made of Calcium carbonate. Individuals secrete multi-chambered tests, generally made of calcium carbonate (CaCO3)

• Pseudopodia project out through holes in shell.

• Feed on diatoms & other protozoans.

• Secrete digestive juices onto their food to dissolve it!!!

• Waste expelled through body surface.

Radiolarians

http://micro.magnet.fsu.edu/micro/gallery/radiolarians/radiohead.jpg

- have tests fused into one delicate piece, usually made of silica- phagocytose microorganisms with their pseudopodia- pseudopodia, known as axopodia, radiate from the central body

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

PowerPoint Lectures for Biology, Seventh Edition

Neil Campbell and Jane Reece

Lectures by Chris Romero200 µm

Axopodia

Kinetoplastids• A kinetoplast is a network

of circular DNA (called kDNA) inside a large mitochondrion that contains many copies of the mitochondrial genome.

• Bodo is a typical genus within kinetoplastida and including various common free-living species which feed on bacteria.

Choanoflagellatges• Flagellates

• Propelled by a flagella

• Whip like

• Colonial, live attached to bottom.

• Collar filters particles from the water.

• the closest living relatives of the animals.

Some marine protists

Rhynchomonas nasuta

Parvicorbicula sp.Plagioselmis prolonga

Bodo saliens

Copyright ©, Mats Kuylenstierna & Bengt Karlson

Mesodinium rubrum5µm

5µm

Heterotrophic nanoflagellates (HNF)

Ciliates

Paradigm change of the ocean’s food web

(Sherr and Sherr 2009)

(Zobell 1946)

(Pomeroy 1974)

“Microbial loop” – by Azam et al. 1983-Transfer of organic carbon from dissolved fraction to higher trophic levels in food chain via bacteria, nanoflagellates, and ciliates

sloppy feeding

Marine Microbial Foodweb