marine invertebrates biol 505 understanding marine invertebrates, their environments and processes

MARINE Invertebrates

BIOL 505Understanding Marine

Invertebrates,

Their Environments and Processes

The Protozoans = “first animals” Unicellular eukaryotes. Between animals and plants.Lack collagen.Lack chitinous cell walls.

Have different modes of existence:some heterotrophicsome photosynthetic (although not in

primitive forms)some detritivoroussome parasitic

The Protozoans~38,000 extant spp. ~44,000 fossil spp.

Have wide range of sizes, shapes, ultrastructure, nutrition, behavior, physiology, genetic diversity.

Of scientific and economic importance.

Many free-living forms – marine.

Most microscopic - ~5 – 20 um (but some new spp 0.5 – 2um).

Since unicellular, each cell must do all basic functions multi-cellular organisms do.

The ProtozoansOrganelles, rather than cells, specialize to increase complexity.

No specialized circulatory, respiratory or excretory structures.

How is gas exchange and excretion accomplished?

Mainly across body wall due to high SA:V ratio.

Whole body has cell membrane (plasmolemma) – same as multicellular cells.

Cytoplasm differentiated into ecto- and endoplasm.

The ProtozoansOrganelles include nuclei, nucleoli, chromosomes, Golgi, ER (smooth and rough), lysosomes, centrioles, mt, and sometimes chloroplasts.

Some organelles not found in metazoan cells are:

contractile vacuoles – help regulate volume

trichocysts – serve in defense or anchoring.

toxicysts - serve in prey capture.

The ProtozoansLocomotion

Most protozoans move by:

1. using cilia

2. using flagella

3. using psuedopodia

Some spp use different forms at different life history stages.

ProtozoansProtozoan Anatomy

ProtozoansCiliophoran Ciliation

Individual cilia associated below cell membrane with other cilia through infraciliature.

Kinetodesmos – striated fibers extending from each kinetosome (basal body of cilia).

The Kinetodesmata – cord of fibers running along side each row of basal bodies.

This infraciliature is not only found in Ciliophora, but also in all adult ciliates, even if adults lack external cilia.

Structure of infraciliature is a primary tool in identifying different ciliate spp.


Cilia usually cover entire body of some spp., but modified or reduced in others.

In some spp. cilia form specific organelles.

Undulating membrane – a flat sheet of cilia that moves as a single unit.

Membranelle – small number of cilia in neighboring rows lean toward each other making a 2-D pointed tooth.

Oxyticha marcili

marginal cirrus

membranelles


Cirrus – cilia gather together to form a bundle, pointed at tip.

Cytostome – oral opening, has specific arrangement and ultrastructure of cilia for different spp.

Cillia that form structures are same as other cilia with no permanent attachment between them. No known mechanisms of association of cilia.

Oxyticha marcili

marginal cirrus

membranelles

ProtozoansCiliophoran Ciliation Pellicle - complex series of membranes often covering body. May be rigid or flexible. May be for support in some spp. Trichocysts often associated with it.

Plasmalemma – outer surface of the body membrane.

Paramecium tetraurelia

Alveoli – series of flattened vesicles beneath plasmalemma. Cilia project to outside from between alveoli.

ProtozoansCiliophoran ReproductionAll ciliates have one or more macronuclei (less abundant) and one or more micronuclei (more abundant).

Thus nuclei are dimorphic (and thus, heterokaryotic).

Macronuclei – polyploid (contains DNA and RNA), is involved with differentiation, regeneration and daily activities of cell. No role in sexual repro.

ProtozoansCiliophoran ReproductionMicronuclei – critical for sexual repro., but not involved with daily activities.

Sex repro in ciliates does not involve gamete formation (why?).

Instead involves process of conjugation, in which 2 individuals exchange genetic material through a conjugation tube.

ProtozoansCiliophoran ReproductionConjugation Steps (Sexual Reproduction)

1. Macronuclei disintegrate.

2. Diploid micronuclei divide by meiosis 4 haploid pronuclei form from each micronuclei.

3. All but one pronuclei break down. Remaining undergoes mitosis 2 identical haploid pronuclei.

4. One of these migrates through conjugation tube to other individual.

5. Migratory pronuclei fuses with stationary pronuclei to form 2N synkaryon.

ProtozoansCiliophoran Reproduction

Conjugation Steps (Sexual Reproduction)

6. Conjugates separate and synkaryon of each conjugate divides several times by mitosis.

7. Some products form micronuclei, others form macronuclei.

8. Cytoplasmic division may follow several individuals genetically distinct from parents.

ProtozoansCiliophoran ReproductionAutogamy (Special Case of INDIVIDUAL Sexual

Reproduction)

1. Much like the first stages of conjugation.

2. Macronuclei degenerate.

3. Micronuclei undergo meiosis pronuclei.

4. Meiosis followed by several mitotic divisions of pronuclei.

5. Two pronuclei form synkaryon and remaining products disintegrate.


Autogamy (Special Case of INDIVIDUAL Sexual Reproduction)

6. Synkaryon divides several times by mitosis.

7. Some products form micronuclei, others form macronuclei.

8. Cytoplasmic division may follow several individuals genetically distinct from parents.


Binary Fission Steps (Asexual Reproduction)

1. Micronuclei divide by mitosis and redistribute through cytoplasm.

2. Macronuclei elongate but don’t undergo mitosis.

3. Macronuclei develops cleavage furrow and divides.


Binary Fission Steps (Asexual Reproduction)

4. Cell develops cleavage furrow. If perpendicular to long axis – transverse binary fission. Divides into anterior and posterior halves. If longitudinal (as in other protozoans) – binary fission.

5. Each half must develop the opposite section lost during division.

6. Unicellular individuals “daughter cells” genetically identical and mirror images of each other.

WHAT HAVE YOU LEARNED TODAY?

ProtozoansProtozoan Diversity

Phylum Dinozoa (Dinoflagellata).

~2500 extant spp.

Occur in both freshwater and marine habitats.

All dinoflagellates have two flagella. One in a longitudinal groove (sulcus) and the other in a transverse groove (girdle or cingulum) around the body.

Position and orientation of grooves is spp specific and used for ID.


Orientation of flagella cause the organism to whirl in distinctive movement patterns.

Individual covered by cellulose plates secreted within alveolar sacs just beneath cell membrane.

ProtozoansProtozoan DiversityPhylum Dinozoa (Dinoflagellata).



Most are bioluminescent.

Many are known to produce highly toxic “red tides” that cause dense aggregations of dinoflagellates that produce neurotoxins (saxitoxins and relatives) that kill fish, crustaceans and bioaccumulate in clams, oysters, mussels and cause diarrhetic shellfish poisoning.

Ciguatera poisoning – neurotoxin that accumulates in certain tropical fish. Can kill people that eat the fish, but fish unaffected by toxin.


Pfiesteria piscicida – dinoflagellate responsible for massive fish kills in estuaries.



About half of all dinoflagellates have chlorophyll and are autotrophs.

Some are important symbionts with some forams, and various multicellular invertebrates, such as ???. These are called zooxanthellae and are mainly from the genus Symnodinium.

Zooxannthellae greatly contribute to the nutritional needs of the host.


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


Phylum Granuloreticulosa; Class Foraminiferans.

Pseudopodia form granular reticulopods with bi-directional streaming.

Reticulopodia form intricate, intercommunicating networks.

Forams comprise the test-forming spp. and are among most abundant protozoans in marine systems.

Secrete multi-chambered tests usually made of CaCO3.

Reticulopodia emerge through pores in test and form branched networks. (Fig. 3.28g


Of the 4,000 extant spp. About 40 are planktonic. The rest are benthic.

No parasitic spp. Although are hosts to symbiotic algae.

Most are heterotrophic feeding on other protists, small metazoans, fungi, bacteria and detritus.

Manys spp. Found in fossil record. Some up to 15 cm diameter.

Fossil forams usually good indication of oil deposits.

ProtozoansProtozoan DiversityPhylum Granuloreticulosa; Class Foraminiferans.

Polystomella strigillata

Bolivina subaenariensis – planktonic foraminifera approximately 1mm long.

Protozoans

Protozoan DiversityPhylum Granuloreticulosa; Class Foraminiferans.


Phylum Radiozoa (Radiolarians).

Body divided into distinct intra- and extra capsular zones separated by a perforated membrane or capsule.

Have pseudopodia supported by radiating microtubules - axopodia. Give a spiny appearance to most spp.

Have rigid endoskeletons made of silica.

Many representatives in fossil record due to siliceous test; approx. 7,700 of ~11,000 described spp.

All radiolarians are planktonic.

Protozoans

Protozoan Diversity

Many spp. Have symbiotic algae and thus meet some nutrition needs through photosynthesis. But also are carnivorous spp. that use axopodia to capture microscopic prey.

Body plan is generally spherical and divided into intra – and extracapsular zones by a perforated membrane, or capsule.

Digestion occur in food vacuoles in extracapsular region. Nucleus contained in intracapsular region.


Phylum Radiozoa (Radiolarians).

WHAT HAVE YOU LEARNED TODAY?

marine invertebrates biol 505 understanding marine invertebrates, their environments and processes

Documents

ultrastructure of cilia

cilia project

kinetosome basal body

body membrane

flat sheet of cilia

different spp

adults lack external

different forms