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Unformatted text preview: BIO1500 W07 Urochordates Hemichordates Basal deuterostome phylogeny made simple Raven Fig. 32.2 Basal deuterostome phylogeny: the complex truth Bourlat et al 2006 Genomic analysis of a hemichordate: acorn worm [Saccoglossus kowalevskii] http://www.ncbi.nlm.nih.gov/genomes/leuks.cgi Acorn worm Hox genes are differentially expressed along the longitudinal body axis Lowe et al 2003 Similar expression domains of Hox and other longitudinal patterning genes in Drosophila, mouse and acorn worm Mouse Drosophila Acorn worm Lowe et al 2003 HEMICHORDATES (anchor worms): classification HEMICHORDATES Note: Monophyly of Hemichordates is debated. 1)Enteropneusta: acorn worms (~100 species) 2) Pterobranchia (~30 species) 2) (~30 3) Planctosphaeroidea (1 species, 3) only larva known) HEMICHORDATES: Enteropneusta 1) Deposit or suspension feeders 2) 1cm - 2.5m length 3) Three main body parts: acornshaped proboscis, trunk, terminal body region 4) Skin covered with mucus and cilia 5) Movement by cilia beat and body contractions 5) Breathing by inhaling water through mouth opening and exhaling through gills 6) Live in burrows 7) About 100 species HEMICHORDATES: Enteropneusta Saccoglossus Kowalevskii Note: Now the red elements of this slide NEED to be memorized!!!!!!!!!!!!! HEMICHORDATES: Enteropneusta 1) Indirect development through tornaria larva stage HEMICHORDATES: Pterobranchia 1) 2) 3) 4) Small worm-like animals Live in sectreted tubes Plancton feeders About 30 known species H E M I C H O R D A T E S : Pterobranchia 1) Living in secreted tubes Colony and single individual of pterobranch Rhabdopleura compacta http://users.ox.ac.uk/~zool0456/Sato.htm HEMICHORDATES: Pterobranchia 1) Filtering of plancton by cilia covered tentacles Basal deuterostome phylogeny: the complex truth Bourlat et al 2006 Sea squirt [Ciona intestinalis] http://www.ncbi.nlm.nih.gov/genomes/leuks.cgi UROCHORDATES (Tunicata): basic facts 1) 2) 2) 3) ~3000 species Small worm-like animals Tadpole like larval stage Filter feeding through gil basket 4) Develop through tadpole larval stage. http://home.uchicago.edu/~egrey/ascidian_biology.htm TUNICATE diversity TUNICATE 1) 2) 3) 4) Ascidiacea Thaliacea Appendicularia Sorberacea TUNICATE diversity: Ascidiacea (sea squirts) 1) 2) 3) 4) Filter feeders Sessile Solitary species Colony forming species 5 ) Community forming species 6 ) Indirect development through free swimming larva TUNICATE diversity: Ascidiacea (sea squirts) TUNICATE
Solitary ascidians are single, discrete individuals that can only reproduce sexually. Species may have separate sexes, but many are hermaphroditic. http://home.uchicago.edu/~egrey/images/S_montereyensis01_jpg.jpg TUNICATE diversity: Ascidiacea (sea squirts)
Social ascidians include species where genetically-identical individuals, or clones, that are vascularly connected to each other in some way. Each "zooid" or discrete unit has an incurrent and excurrent siphon. Social ascidians can reproduce both sexually and asexually. http://home.uchicago.edu/~egrey/images/Metandrocarpa_jpg.jpg TUNICATE diversity: Ascidiacea (sea squirts) TUNICATE
In Compound or colonial ascidians individual zooids are integrated in a gelatinous matrix to the extent of sharing a common excurrent siphon with neighboring zooids. These species often looks like blobs, but are actually hundreds or thousands of genetically identical individuals. Compound ascidians can reproduce both sexually and asexually. http://home.uchicago.edu/~egrey/images/Botryllus_dominant_jpg.jpg TUNICATE diversity: Ascidiacea http://www.ryanphotographic.com/images/JPEGS/Phallusia%20julinea%20Australia.jpg TUNICATE diversity: Ascidiacea TUNICATE TUNICATE diversity: Ascidiacea TUNICATE diversity: Ascidiacea http://www.ryanphotographic.com/ascidians.htm TUNICATE diversity: Ascidiacea TUNICATE diversity: Ascidiacea
Megalodicopia hians: only free living carnivorous sea squirt. TUNICATE diversity: Thaliacea 1) Free floating through out entire life span 2) Filter feeders 3) Movement by jet expulson of water from siphon TUNICATE diversity: Appendicularia or Appendicularia Larvacea 1) 2) Solitary Free swimming throughout life cycle 3 ) Morphology resembles ascidian tadpole larva with trunk and tail 4 ) Notochord 5) Dorsal nerve chord UROCHORDATES (Tunicata): adult body plan traits 1) Lack of segmentation 2) Coelom reduced to pericardial cavity and gonads 3) Most organs enclosed by epicardium which is surrounded by mesenchyme Ascidians: basic body plan traits of adult stage
1. Integument: The 1. internal anatomy of ascidians is surrounded by a body wall made up of fibers and a carbohydrate known as tunicin. This body wall is called a tunic and hence the common name for ascidians "Tunicate". http://home.uchicago.edu/~egrey/ascidian_biology.htm Ascidians: basic body plan traits of adult stage
2. Digestige system: nearly all species sessile suspension feeders. Water enters through the incurrent siphons and passes through the mucouscovered pharynx (on which the food is trapped) and then exits through the excurrent siphon. The endostyle, an organ thought to be the precursor to the thyroid gland, produces the mucous, which is rolled up and ingested along with any food that has been trapped in it. A new net is then secreted over the pharynx and the process starts all over again.
http://home.uchicago.edu/~egrey/ascidian_biology.htm Ascidians: comparison of larval and adult body plan http://home.uchicago.edu/~egrey/ascidian_biology.htm Ascidians: comparison of larval and adult body plan http://home.uchicago.edu/~egrey/ascidian_biology.htm Similarity of ascidian larva body plan organization with Similarity higher chordates Sea squirt [Ciona intestinalis] http://www.ncbi.nlm.nih.gov/genomes/leuks.cgi Sea squirt cleavage Sea squirt larva development Sea squirt larva development Development from egg to tadpole in 12 hours (Phallusia). Mitochondria-rich myoplasm domain (labelled with DIOC2(3) (green) is partitioned into the posterior pair of blastomeres which give rise to primary muscle cells in the tail of the tadpole . Time lapse DIC and fluorescence microscopy. Sea squirt larva development Development from 8 cell stage to tadpoles(Phallusia): This sequence of 2 embryos held in a microchamber was recorded overnight using DIC optics and time lapse microscopy. The field is about 300 microns wide. http://biodev.obs-vlfr.fr/recherche/biomarcell/films+images/filmarchive.htm#maturation Sea squirt larva development Asymmetric cleavage in posterior blastomeres of 16 cell stage embryo (Phallusia). In the first part of the film the centrosome can be observed as a clear zone in front of the interphase nucleus . Led by the centrosome, the nucleus stretches and migrates near the posterior cortex. In the second part of the movie (from 11 seconds), the nuclei are already positioned near the cortex. After nuclear breakdown two CABs are visible as a smooth moustache-shaped zone. One spindle pole in each cell approaches the CAB and unequal cleavage ensues. DIC time lapse microscopy. Frames were collected every 10 seconds and are displayed at a rate of 30 per second. Patalano et al. (2006) J.Cell Science, 119, 1592-1603. Sea squirt larva development Movie 6. Time-lapse confocal sequence of a Phallusia embryo undergoing unequal cleavages in the posterior pole from the 8 to the 32 cell stages. ER is labeled with DiIC16(3) (red) and mitochondria with DiOC2(3) (green). Arrow shows the cER-rich CAB. Images were acquired every 2 minutes. Polarity of the ascidian egg cortex and relocalization of cER and mRNAs in the early embryo J Cell Sci Prodon et al. 118: 2393 ...
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This note was uploaded on 08/03/2010 for the course BIO 1500 taught by Professor Pandolfi during the Winter '08 term at Wayne State University.
- Winter '08