MARINE Invertebrates BIOL 505 Understanding 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 heterotrophic some photosynthetic (although not in primitive forms) some detritivorous some 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 Protozoans Organelles, 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 Protozoans Organelles 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 Protozoans Locomotion Most protozoans move by: 1. using cilia 2. using flagella 3. using psuedopodia Some spp use different forms at different life history stages.

Protozoans Protozoan Anatomy

Protozoans Protozoan Anatomy

Protozoans Protozoan Anatomy

Protozoans Ciliophoran 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.

Protozoans Ciliophoran Ciliation Oxyticha marcili marginal cirrus membranelles Ciliophoran Ciliation 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.

Protozoans Ciliophoran Ciliation Oxyticha marcili marginal cirrus membranelles Ciliophoran Ciliation 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.

Protozoans Ciliophoran 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.

Protozoans Ciliophoran Reproduction All 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.

Protozoans Ciliophoran Reproduction Micronuclei – 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.

Protozoans Ciliophoran Reproduction Conjugation Steps (Sexual Reproduction) Macronuclei disintegrate. Diploid micronuclei divide by meiosis  4 haploid pronuclei form from each micronuclei. All but one pronuclei break down. Remaining undergoes mitosis  2 identical haploid pronuclei. One of these migrates through conjugation tube to other individual. Migratory pronuclei fuses with stationary pronuclei to form 2N synkaryon.

Protozoans Ciliophoran Reproduction Conjugation Steps (Sexual Reproduction) Conjugates separate and synkaryon of each conjugate divides several times by mitosis. Some products form micronuclei, others form macronuclei. Cytoplasmic division may follow  several individuals genetically distinct from parents.

Protozoans Ciliophoran Reproduction

Protozoans Ciliophoran Reproduction Autogamy (Special Case of INDIVIDUAL Sexual Reproduction) Much like the first stages of conjugation. Macronuclei degenerate. Micronuclei undergo meiosis  pronuclei. Meiosis followed by several mitotic divisions of pronuclei. Two pronuclei form synkaryon and remaining products disintegrate.

Protozoans Ciliophoran Reproduction Autogamy (Special Case of INDIVIDUAL Sexual Reproduction) Synkaryon divides several times by mitosis. Some products form micronuclei, others form macronuclei. Cytoplasmic division may follow  several individuals genetically distinct from parents.

Protozoans Ciliophoran Reproduction Binary Fission Steps (Asexual Reproduction) Micronuclei divide by mitosis and redistribute through cytoplasm. Macronuclei elongate but don’t undergo mitosis. Macronuclei develops cleavage furrow and divides.

Protozoans Ciliophoran Reproduction Binary Fission Steps (Asexual Reproduction) 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. Each half must develop the opposite section lost during division. Unicellular individuals “daughter cells” genetically identical and mirror images of each other.

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Protozoans Protozoan 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.

Protozoans Protozoan Diversity 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.

Protozoans Protozoan Diversity Phylum Dinozoa (Dinoflagellata).

Protozoans Protozoan Diversity Phylum 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.

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

Protozoans Protozoan Diversity Phylum Dinozoa (Dinoflagellata). 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.

Protozoans Protozoan Diversity Noctiluca Protozoan Diversity 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.

Protozoans Protozoan Diversity 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

Protozoans Protozoan Diversity 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.

Protozoans Protozoan Diversity Phylum Granuloreticulosa; Class Foraminiferans. Bolivina subaenariensis – planktonic foraminifera approximately 1mm long. Polystomella strigillata

Protozoans Protozoan Diversity Phylum Granuloreticulosa; Class Foraminiferans.

Protozoans Protozoan Diversity 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.

Protozoans Protozoan Diversity Phylum Radiozoa (Radiolarians).

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