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Topic: Choanoflagellate

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	Introduction to the Choanoflagellata
		Yet choanoflagellates must have existed on the Earth since the Late Precambrian, because they are the closest living protist relatives of the sponges, the most primitive metazoans.
		Choanoflagellates are almost identical in shape and function with the choanocytes, or collar cells, of sponges; these cells generate a current that draws water and food particles through the body of a sponge, and they filter out food particles with their microvilli.
		A few living choanoflagellates, such as Proterospongia, are colonial for part of their life cycle, and show a limited degree of cell differentiation and integration into a unit; these colonial choanoflagellates are the best living examples of what the ancestor of all metazoans may have looked like.
	www.ucmp.berkeley.edu /protista/choanos.html (352 words)

	Choanoflagellates
		Choanoflagellates are found globally in marine, brackish and freshwater environments from the Arctic to the tropics, occupying both pelagic and benthic zones.
		Irrespective of their distribution, choanoflagellates are in high abundance relative to other nanoplankton members in their communities, and there is a positive correlation between primary producers and choanoflagellate densities, supporting a model in which choanoflagellates play a pivotal role in the microbial food web and carbon cycling (Buck and Garrison, 1988).
		Choanoflagellates are either free-swimming in the water column or sessile, adhering to the substrate directly or through either the periplast or a thin pedicel (Leadbeater, 1983).
	tolweb.org /Choanoflagellates (1588 words)

	Choanoflagellata - MicrobeWiki
		Choanoflagellates are small single-celled protists that live in freshwater and marine environments.
		Choanoflagellates either use the flagellum for locomotion or are rooted to the substrate by a thin stalk.
		Choanoflagellates are nearly identical to the collar cells (choanocytes) of sponges, which also act as filters of bacteria and food particles.
	microbewiki.kenyon.edu /mediawiki-1.6.6/index.php/Choanoflagellata (516 words)

	Choanoflagellate
		The choanoflagellates are a group of flagellate protozoa.
		They are considered to be the closest relatives of the animals, and in particular may be the direct ancestors of sponges.
		Each choanoflagellate has a single flagellum, surrounded by a ring of hairlike protrusions called microvilli, forming a cylindrical or conical collar (choanos in Greek).
	www.ebroadcast.com.au /lookup/encyclopedia/ch/Choanoflagellate.html (174 words)

	Center for Integrative Genomics
		In addition to their ecological role, choanoflagellates are among the closest unicellular relatives of animals and provide important insights into the origin and diversity of animal phyla.
		In fact, choanoflagellates are thought to be major players in the marine carbon cycle, breaking down bacteria and returning nutrients to the water.
		The marine choanoflagellate Monosiga brevicollis was selected for genome sequencing because it is easily grown in the laboratory, is available in monoxenic (single species) culture, and has been thoroughly considered in phylogenetic studies.
	cigbrowser.berkeley.edu /index.php?option=com_content&task=view&id=21 (185 words)

	PID - Salpinogoeca Introduction
		The genus typifies one of the three main choanoflagellate families, the Salpingoecidae (the others are the Codosigidae and the Acanthoecidae).
		For this reason, choanoflagellates have long been thought to be the protist group that is the most closely related to the animals; this hypothesis was first published in 1866.
		Molecular investigations are showing that choanoflagellates belong to a clade that includes the animals, the fungi, the ichthyosporean/mesomycetozoan group of commensal/parasitic protists, and the nucleariid amoebae.
	megasun.bch.umontreal.ca /protists/salp/introduction.html (121 words)

	HHMI News: Primitive Microbe Offers Glimpse of Animal Evolution
		Choanoflagellates are a group of about 150 species of single-celled protists, which use a whip-like flagellum to swim and draw in food.
		And the circumstantial evidence supporting that notion was compelling — choanoflagellates are nearly identical to cells called choanocytes in sponges that also carry out food-gathering and some species of choanoflagellates tend to form colonies.
		According to Carroll, the studies on choanoflagellates promise to be an important part of his laboratory’s ongoing studies of animal evolution.
	www.hhmi.org /news/carroll2.html (840 words)

	choanoflagellate@Everything2.com
		A choanoflagellate is a single-celled organism that is generally believed to be the most closely related to multi-celled animals, and many would classify Choanoflagellata as one branch of the taxon Animalia.
		Some choanoflagellate colonies are balls with the flagella pointing outwards, which makes them resemble the colonial alga Volvox, while others form a cupped shape and have the flagella pointing inwards, which is how sponges are arranged.
		Sponges (phylum Porifera) are animals that strongly resemble a colony of choanoflagellates that has started to differentiate and thereby become a multicellular organism.
	everything2.com /index.pl?node_id=1725449 (522 words)

	Primitive microbe offers model for evolution of animals
		Choanoflagellates are a group of about 150 species of single-celled protists, which use a whip-like flagellum to swim and draw in food.
		The researchers first compared genes in one species of choanoflagellate, Monosiga brevicollis, to four animal genes that express proteins that are highly conserved throughout the animal kingdom.
		According to Carroll, the studies on choanoflagellates promises to be an important part of his laboratory’s ongoing studies of animal evolution.
	www.eurekalert.org /pub_releases/2001-12/hhmi-pmo121701.php (693 words)

	DPC - Videnscenter - DPC publikationer - Vol. 8
		Planktonic choanoflagellates from Disko Bugt, West Greenland, with a survey of the marine nanoplankton of the area.
		Two new choanoflagellate taxa are described on the basis of West Greeenland material: Conion groenlandicum gen. et sp.
		A summary of previous findings of the choanoflagellate species encountered in the Disko Bugt samples show that three species (Conion groenlandicum, Pleurasiga caudata and Parvicorbicula serratula) are so far known from arctic and subarctic localities only.
	www.dpc.dk /sw2939.asp (218 words)

	Animals: Tracing Their Heritage Interview with Nicole King
		Both cell biological and molecular evidence indicate that choanoflagellates are the closest living relatives of multicellular animals.
		Choanoflagellates use flagella to swim and trap food, mostly bacteria, in the walls of their collar (see image).
		Genes shared by choanoflagellates and animals were likely present in their common ancestor and may shed light on the transition to multicellularity.
	www.actionbioscience.org /evolution/king.html (1175 words)

	CRITICAL BIOLOGICAL PROCESSES AT WORK IN HUMANS WERE IN PLACE BEFORE ADVENT OF MULTICELLULAR LIFE ON EARTH (Site not responding. Last check: )
		While the use of these signaling pathways are generally known in animals, and are much studied by scientists, their functions in choanoflagellates remain a mystery, says King, the lead author of the Science report.
		Choanoflagellates are a phylum of transparent, single-celled microbes that propel themselves with whip-like appendages.
		"The expression in choanoflagellates of proteins involved in cell interactions in (animals) demonstrates that they evolved before the origin of animals and were later co-opted for development," the group writes in the Science report.
	www.newmaterials.com /news/7311.asp (928 words)

	choanoflagellate - Search Results - MSN Encarta
		The choanoflagellates are a group of flagellate protozoa.
		Choanoflagellate-like cells are also found in other animal phyla; in organisms such as flatworms and rotifers, for instance, choanoflagellate-like cells are found in flame bulbs that act as excretory...
		Co-distributed choanoflagellate species can occupy quite different microenvironments, but in general, the factors that influence the distribution and dispersion of choanoflagellates remain to be...
	encarta.msn.com /choanoflagellate.html (148 words)

	CiteULike: Observations on the ultrastructure of the choanoflagellate Codosiga botrytis (Ehr.) Saville-Kent with ... (Site not responding. Last check: )
		The ultrastructure of the choanoflagellate Codosiga botrytis is described with particular reference to the flagellar appendages, the flagellar rootlet system, the transition zone, the basal body and accessory centrioles, and the stalk.
		The structure of choanoflagellates differs widely from that of the algal class Chrysophyceae, the group in which they are included in some classifications, and from the remainder of the algae; they do not appear to have a place in either the algae or the plant kingdom.
		The structure of Codosiga botrytis is briefly compared with that of sponge choanocytes and collared cells in the Metazoa and some of the possible phylogenetic implications of this are indicated.
	www.citeulike.org /user/srfairclough/article/1237848 (771 words)

	MICROBE GENES HELP SCIENTISTS RECONSTRUCT ANIMAL ORIGINS (Site not responding. Last check: )
		Long suspected to be close relatives of animals, choanoflagellates have a lineage that dates to more than 600 million years ago, the time when animals, multicellular organisms with distinct body plans and systems of organs, are believed to have evolved in the ancient stew of microscopic protozoan life
		Undertaking a similar exploration in choanoflagellates, Carroll and his colleague, Nicole King, also of the Howard Hughes Medical Institute at UW-Madison, discovered a signaling gene in a choanoflagellate that, until now, was known only in animals.
		"Choanoflagellates express genes involved in animal development that are not found in other single-celled organisms, and that may be linked to the origin of animals.
	www.newmaterials.com /news/7376.asp (1080 words)

	BASIC SCIENCE: Single Cell Signals to Multiple Cells Applied Genetics News - Find Articles
		In analyzing single-celled choanoflagellates, Sean Carroll and Nicole King, from the University of Wisconsin, Madison, discovered that the organisms have a receptor tyrosine kinase, the first that has been found in a single-celled organism.
		Choanoflagellates are a group of about 150 species of single- celled protists, which use a whip-like flagellum to swim and draw in food.
		Carroll and King compared genes in one species of choanoflagellate, Monosiga brevicollis, to four animal genes- elongation factor 2, alpha-tubulin, beta-tubulin and actin-that are widely used as molecular markers to explore relationships among species.
	www.findarticles.com /p/articles/mi_m0DED/is_6_22/ai_82516354 (475 words)

	SYSTEMATIC BIOLOGY
		The choanoflagellates are free-living aquatic organisms (freshwater to marine) that range from unicellular to colonial species and resemble choanocytes, the flagellated collar cells of sponges (see A-D above).
		The collar is made of microvilli that surround the single flagellum and serves as a filter for catching particles caught in the vortex created by the flagellum.
		Until recently the choanoflagellates were considered to be part of the zooflagellates (Margulis and Schwartz 1988, 1998; and Buck 1990).
	comenius.susqu.edu /bi/202/Animals/CHOANOZOA/choanoflagellata.htm (684 words)

	Palaeos Metazoa: Metazoa
		Everything from sponges and jellyfish to insects and vertebrates is belongs in "Metazoa", and considered to have evolved from a single unicellular choanoflagellate ancestor, sometime during the Ediacaran period.
		The most widely held theory seems to be that a colonial choanoflagellate evolved into a hollow spherical ball of cells, the blastula, which constitutes the earliest embryonic stage of development, and even occurs in sponges.
		Animals are closely related to a particular group of protists, the choanoflagellates.
	www.palaeos.com /Invertebrates/default.htm (1353 words)

	Choanoflagellates Scientific classification Kingdom Protista ... (Site not responding. Last check: )
		"Choanoflagellates" "Scientific classification" Kingdom:Protista Phylum:Choanozoa Class:"Choanoflagellatea" The "choanoflagellates" are a group of flagellate protozoa.
		Each choanoflagellate has a single flagellum, surrounded by a ring of hairlike protrusions called microvilli, forming a cylindrical or conical collar ("choanos" in Greek).
		Planktonic Choanoflagellates from Disko Bugt, West Greenland, with a survey of the marine nanoplankton of the area (Meddelelser om Grønland.
	www.geodatabase.de /choanoflagellate (242 words)

	Nicole King
		Genes shared only by choanoflagellates and animals were likely present in their common ancestor and may shed light on the transition to multicellularity.
		The mechanisms by which choanoflagellates form colonies, establish cell polarity, and reproduce should provide crucial insights into the transition to multicellularity, but little is known about their cell or natural history.
		Therefore, we are examining the life cycles of diverse choanoflagellates using techniques ranging from classical protistology to electron and immunofluorescence microscopy to bioinformatics.
	mcb.berkeley.edu /faculty/GEN/kingn.html (510 words)

	Metazoa - Palaeos
		From a simple colonial choanoflagellate ancestor, animals developed through increasing grades of specialization and complexity, first sponges, then coelenterates, and finally bilateral animals (possessing a head and front and rear).
		The problem here is that although choanoflagellates seem clearly related to sponges, it is not clear how closely related sponges are to the rest of the Metazoa.
		The most widely held theory seems to be that a colonial choanoflagellate evolved into a hollow spherical ball of cells, the blastula, which constitutes the earliest embryonic stage of development, and even occurs in sponges.
	www.palaeos.org /Animalia (1423 words)

	Chapter 4 The Evolution of Metazoans
		In 2001 and 2002, it was established that both nuclear and mitochondrial genes confirm that choanoflagellates and metazoans are closely related.
		This study revealed that choanoflagellates have the genes to produce a variety of proteins that are used in metazoans to hold cells together and to transmit signals between cells.
		But choanoflagellates, apparently alone among protists, had the genes that made it possible for them or their close relatives to experiment with multicellularity in a way that was not possible for other protists.
	www.geology.ucdavis.edu /~cowen/HistoryofLife/CH04.html (947 words)

	Diaphanoeca grandis
		Distinctive features: Bottle shaped lorica constricted at the front, 10-13 longitudinal costae each with ten costal strips, spear with two costal strips, protoplast at the frontal part of the lorica.
		Andersen, P. Functional biology of the choanoflagellate Diaphanoeca grandis Ellis.
		Throndsen, J. Planktonic choanoflagellates from North Atlantic waters.
	www.smhi.se /oceanografi/oce_info_data/plankton_checklist/others/diaphanoeca_grandis.htm (94 words)

	CHOANOFLAGELLATE Articles The choanoflagellates are a group o
		They are considered to be the closest living relatives of the animals, and the last unicellular ancestors of animals are thought to have resembled modern choanoflagellates.
		Each choanoflagellate has a single flagellum, surrounded by a ring of actin-filled protrusions called microvilli, forming a cylindrical or conical collar (choanos in Greek).
		A number of species such as those in the genus Proterospongia are colonial, usually taking the form of a cluster of cells on a single stalk, but often forming planktonic clumps that resemble a miniature cluster of grapes in which each cell in the colony is flagellated.
	www.amazines.com /Choanoflagellate_related.html (526 words)

	Water & Atmosphere Vol. 9 No. 2, June 2001 - NIWA (Site not responding. Last check: )
		Choanoflagellates are present in almost all aquatic habitats.
		Nevertheless, Haeckel did not consider the sponges to be in the direct line of animal evolution – a position he reserved for the coelenterates – but as a curious side branch to the main line of animal evolution.
		Since this time it has remained conventional wisdom that the choanoflagellates and sponges are closely related and that either this line of evolution or an offspring gave rise to the Metazoa and the remainder of the Animal Kingdom.
	www.niwa.co.nz /pubs/wa/09-2/evolution.htm (1530 words)

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