chapter 18

Protists II

Lecture Overview

  • Title: Protists II
  • Date: 18 June 2016
  • Location: Santa Cruz Island, California
  • Focus: Chapter 28 - Exploration of various protist groups within the Kingdom Chromista

Quote

  • Biblical Reference:
    • "The Lord said to Moses, 'Tell Aaron, ‘Take your staff and stretch out your hand over the waters of Egypt—over the streams and canals, over the ponds and all the reservoirs—and they will turn to blood.’" – Exodus 7:19 NIV

Kingdom Chromista

  • Overview
    • Includes several protist groups, mainly characterized by the presence of chlorophyll for photosynthetic species.
Apicomplexans
  • General Characteristics:
    • Unicellular organisms, nearly all are intracellular parasites.
    • Only two species are photosynthetic.
  • Apical Complex:
    • Definition: A unique collection of specialized organelles located at one end of the cell.
    • Function: Enables apicomplexans to attach, penetrate, and invade host cells.
    • Components of the Apical Complex:
    • Micronemes
    • Apicoplast
    • Centrosome
    • Subpellicular microtubules
    • Inner membrane complex
    • Plasma membrane with conoid, preconoidal, and polar rings
    • Rhoptries
    • Dense granules
    • Golgi apparatus
    • Endoplasmic reticulum
    • Mitochondrion
    • Basal complex with basal polar ring.
  • Life Cycles:
    • Most apicomplexans have complex life cycles featuring both sexual and asexual reproduction stages.
    • Life cycles often necessitate two or more host species.
Vectors
  • Definition: An agent that transfers genetic material or a disease from one organism to another.
Plasmodium spp.
  • General Information:
    • Over 200 species exist that cause malaria in vertebrates.
    • Five species are specifically known to cause malaria in humans.
    • Vectors: Females of approximately 60 species of Anopheles mosquitoes.
Plasmodium Life Cycle

  • Stages in the Mosquito:

    • Oocyst: Ruptures releasing sporozoites.
    • Mosquito takes a blood meal injecting sporozoites.
    • Sporogonic Cycle:
    • Involves exflagellated microgametocyte turning into a macrogametocyte.
    • Microgamete enters macrogamete and forms oocyst.
    • Human Liver Stages:
    • Exo-erythrocytic Cycle: Release of sporozoites.

  • Human Blood Stages:

    • Infected liver cells lead to the formation of immature trophozoites (ring stage).
    • Progression to mature trophozoites and then to ruptured schizonts.
    • Species involved: P. falciparum, P. vivax, P. ovale, P. malariae, and gametocytes.
Distribution of Human Malaria
  • Areas of Risk for Malaria:
    • Maps depict regions with high, seasonal, moderate, low and no risk.
    • Notable locations include:
    • Dominican Republic
    • Puerto Rico
    • Cape Verde
    • Haiti
    • Various regions in Asia including Macao, Palawan, etc.
  • Prevention:
    • Emphasis on mosquito bite prevention and chemoprophylaxis is recommended in higher-risk areas.
  • Important Note: Rare sporadic cases of malaria can still occur even in lower-risk areas like Fiji.
Ciliates (Phylum Ciliophora)
  • Characteristics:
    • Unicellular organisms with two types of nuclei (micronucleus and macronucleus).
    • Most are predators; some are parasites.
    • Structures include cilia, contractile vacuoles, and oral grooves for feeding along with food vacuoles.
    • Organelle arrangement:
    • Cytoplasm organized into specialized areas for feeding and waste excretion.
Cilia
  • Definition: Many short, hair-like organelles found on the outer cell membrane.
Kleptoplasty
  • Definition: The process of capturing, retaining, and using chloroplasts from prey for photosynthesis.
  • Occurrence: Notably present in some photosynthetic ciliate species, such as Mesodinium rubrum.
Paramecium spp.
  • Habitat: Commonly found in still freshwater ecosystems.
Rhizarians Group
  • Description:
    • Majority are unicellular (with one genus being multicellular).
    • Mostly heterotrophic; some are mixotrophic (combining photosynthesis and heterotrophy).
  • Photosynthesis: One known species exhibits photosynthetic abilities.
Pseudopodia
  • Definition: Temporary, foot-like extensions of a cell that are instrumental for locomotion and food capture.
Radiolarians (Phylum Radiozoa)
  • Characteristics:
    • Typically possess cell membranes formed of silica (SiO2).
    • Have spine-like pseudopodia supported by microtubules.
    • Found predominantly in the surface layers of water as part of phytoplankton.
    • Their remains contribute to thick sediment deposits.
Foraminiferans (Phylum Foraminifera)
  • Description:
    • Cell membranes composed of calcium carbonate (CaCO3).
    • Exhibit thread-like pseudopodia that extend through porous holes in their membrane.
    • Create chambered structures, primarily benthic, but some are found as zooplankton near the surface, being significant in sea sediment composition.
  • Deposits: Responsible for extensive limestone and chalk deposits during historical geological periods (Mesozoic and early Cenozoic).
Cercozoans (Phylum Cercozoa)
  • General Characteristics:
    • Exhibit ameoba-like features with thin, thread-like pseudopodia and include other flagellated protists.
    • Found in both aquatic environments and terrestrial settings.
    • Many species are parasitic; one of note, Paulinella chromatophora, is photosynthetic.
Secondary Endosymbiosis
  • Explanation: This process entails the engulfment of one eukaryotic cell by another, subsequently evolving multiple membrane structures from the incorporated organism, noted specifically in certain lineages.
    • Diagrammatic Influence: Visual representation indicating primary endosymbiosis leading to subsequent secondary events.

Major Clades and Relationships in Protists

  • Overview of the relationship between major groups:
    • Excavata: Diplomonads, Parabasalids, Euglenozoans.
    • SAR Clade: Diatoms, Golden algae, Brown algae, Dinoflagellates, Apicomplexans, Ciliates, Foraminiferans, Cercozoans, Radiolarians.
    • Archaeplastida: Red algae, Chlorophytes, Charophytes, and Land plants.
    • Unikonta: Includes amoebozoans, slime molds, tubulinids, entamoebas, as well as fungi and choanoflagellates leading to animals.
Kingdom Plantae
  • Overview:
    • Encompasses a range of organisms,
    • Majority are multicellular, some are unicellular.
    • Characterized by a primarily cellulose-based cell wall and high rates of photosynthesis, with a few heterotrophic forms.
Red Algae (Phylum Rhodophyta)
  • Pigmentation: Typically reddish due to pigment phycoerythrin.
  • Habitat: Found primarily in marine environments, with robust specimens recorded in multiple locations including Duxbury Reef and various Californian coasts.
  • Reproductive Strategy:
    • Both asexual and sexual reproduction modes are utilized.
    • Most exhibit alternation of generations, alternating between gametophyte (1n) and sporophyte (2n) stages.
Alternation of Generations in Red Algae
  • Lifecycle Stages:
    • Diploid (2n) Sporophyte produces carpospores through mitosis, with fertilization leading to haploid (1n) gametes and formation of a gametophyte.
    • The gametophyte further goes through mitosis producing spores, completing the lifecycle.
Red Algae Distribution and Examples
  • Notable Species:
    • Nori (Pyropia spp.) is cultivated for food.
    • Sample findings of various seaweeds in distinct California coastlines including Black Pine Seaweed (Neorhodomela larix) and Sea Sacks (Halosaccion glandiforme).
Green Algae (Phyta Chlorophyta and Charophyta)
  • Characteristics:
    • Predominantly green due to chlorophyll.
    • Can be unicellular or multicellular:
    • Some unicellular species can be multinucleate.
    • Habitat diversity: Found within aquatic and terrestrial environments, and can thrive on various surfaces.
  • Reproductive Modes: Includes both asexual and sexual reproduction strategies; also characterized by an alternation of generations.
Zoochlorellae
  • Definition: Photosynthetic green algae living within cells or tissues of other organisms, contributing to symbiotic interactions.
  • Occurrence: Found in various organisms in different protist groups including amoebozoans, cercozoans, and in anemones.
Additional Observations
  • Environmental presence of specific genera like Broadleaf Sea Lettuce (Ulva Lactuca) and Dead Man's Fingers (Codium fragile), noted in California regions observed on various dates.

Interactive Components

  • Future Discussion: Nonvascular and vascular plants will be discussed in subsequent lectures.