From robert.williamson@stanfordalumni.org Thu May 19 22:00:23 2005 Return-Path: Received: from popserver3.Stanford.EDU ([unix socket]) by popserver3.Stanford.EDU (Cyrus v2.2.12) with LMTPA; Thu, 19 May 2005 22:00:23 -0700 X-Sieve: CMU Sieve 2.2 Received: from leland3.Stanford.EDU (leland3.Stanford.EDU [171.67.16.108]) by popserver3.Stanford.EDU (8.12.11/8.12.11) with ESMTP id j4K50NQh016561 for ; Thu, 19 May 2005 22:00:23 -0700 (PDT) Received: from cmsout03.mbox.net (cmsout03.mbox.net [165.212.64.33]) by leland3.Stanford.EDU (8.12.11/8.12.11) with ESMTP id j4K50MMK010996 for ; Thu, 19 May 2005 22:00:22 -0700 Received: from cmsout03.mbox.net (cmsout03.mbox.net [165.212.64.33]) by cmsout03.mbox.net (Postfix) with ESMTP id 53828F0; Fri, 20 May 2005 05:00:21 +0000 (GMT) Received: from uadvg137.cms.usa.net [165.212.11.137] by cmsout03.mbox.net via smtad (C8.MAIN.3.21U); Fri, 20 May 2005 05:00:21 GMT X-USANET-Source: 165.212.11.137 IN robert.williamson@stanfordalumni.org uadvg137.cms.usa.net X-USANET-MsgId: XID939JeTFaV8374X03 Received: from cmsweb11.cms.usa.net [165.212.8.27] by uadvg137.cms.usa.net (ASMTP/) via mtad (C8.MAIN.3.21E) with ESMTP id 427JeTFaT0078M37; Fri, 20 May 2005 05:00:19 GMT X-USANET-Auth: 165.212.8.27 AUTO robert.williamson@stanfordalumni.org cmsweb11.cms.usa.net Received: from 66.82.9.76 [66.82.9.76] by cmsweb11.cms.usa.net (USANET web-mailer CM.0402.7.24); Fri, 20 May 2005 05:00:18 -0000 Date: Thu, 19 May 2005 22:00:18 -0700 From: Robert Williamson To: Subject: What is the largest instance of precise counting in nature? Cc: X-Mailer: USANET web-mailer (CM.0402.7.24) Mime-Version: 1.0 Message-ID: <031JeTFas0016S11.1116565218@cmsweb11.cms.usa.net> Z-USANET-MsgId: XID427JeTFaT0078X37 Content-Type: text/plain; charset=UTF-8 X-Evolution-Source: imap://ashishg@ashishg.pobox.stanford.edu:993/ Content-Transfer-Encoding: 8bit Ta da!!! Here is a short list that may not be complete, but at least provides some assistance in your search and some useful search terms (e.g., eutelic). BEST FOUND EXAMPLE: If your C. Elegans example is a valid instance of counting, then Tardigrades would also be. Tardigrades always have the same number of cells, usually around 40,000. No one has ever actually counted the exact number. However, it seems that counting the number of cells in small organisms is pretty easy today, just search for this type of equipment on google. Search Terms: MUST: Organisms EXACT: “exactly the same number” 1 OF: quills feathers eyelashes cells eggs fungi sperm flagella NOT: chromosomes chromosome Other search terms: Eutelic, determined, model organism e.g., “animals that lay a determined number of eggs” RESULTS: 1.0 Cell-oriented Creatures Protista asexual daughter colony formation Property: One or more cells leave the algae colony and form an exact copy of the original colony with exactly the same number of cells. Mechanism: Daughter colony is completely formed before it can escape, therefore, binary cell division. Occurrence Rate: Rare Type of counting: # of cells in the daughter colony is precisely the same as the number of cells in the parent colony, even though perhaps only one cell leaves the parent colony to form the daughter colony. Type of counting: Not really counting, more likely just cell division. Eudorina colony size Property: All colonies are 32, 64, or 128 cells. Mechanism: Probably binary subdivision with communication or detection. Occurrence Rate: ? Type of counting: Type of counting: Variable, but more than just a trivial power of two that could be explained (in some ways) by binary mathematics of cell division. Any Eutelic Metazoan, such as a Rotifer (phylum Rotifera) Property: Eutelic. All creatures of the same species have the same number of cells. Mechanism: Probably binary cell division with termination point. Dicyemids: Mesozoans (which makes them halfway between Metazoans and Protozoans) Property: Eutelic. All members of the same Dicyemid species have exactly the same number of cells. Tardigrades Property: Eutelic Type of counting: ~40,000 cells (apparently no one has bothered to count each one. BUT! You could probably do it yourself nowadays). Reference: http://www.earthlife.net/inverts/tardigrada.html Search terms: cell counting (on google, you’ll get lots of ads) Quote from this page: “Tardigrades are what is called eutelic, meaning there is a fixed number of cells in the body of an adult of any given species, this is normally around 40,000 cells. Tardigrades have 8 legs, but these legs are not jointed like the legs of insects and spiders etc. They have a relatively large brain and a well developed nervous system with a double suboesophagal ganglia and 4 further ganglia along the body.” Eutelic organs Property: Even though an entire organism is not eutelic, sometimes specific organs are. The eutelic nematode Ascaris always has 162 neurons. http://cogprints.org/1089/00/indentifiable_neuron.htm 1.1 (Potentially) useful papers Here’s an interesting paper on how cell counts of 959 (and other values) might be occurring. http://www.nervenet.org/netpapers/Azevedo2001.pdf Some interesting data on something called pseudocoels, of which C Elegans is an example. Page doesn’t allow “Find” in I.E., but maybe there are some useful search terms. C Elegans always have 80 cells of pharynx. http://www.wncc.net/courses/dnash/zoology/pseudocoel.htm 1.2 Low-level (sub-cellular, e.g., chromosomes): Aulacantha (Protozoa) Property: All have 1600 chromosomes Mechanism: Chemical reaction Type of counting: N/A Polyploidic Endoreplication in Plants Property: Ploidy is the number of copies of chromosomes in one cell of a species. Humans have ploidy of 2. Various algae and other cellular creatures have unusual ploidy counts. Some salamanders have ploidy count of 55. Sugar cane seems to have the largest number of chromosomes, with 80. Mechanism: (Guessing) Cell chromosome duplication system that relies on exhaustible resources within the cell wall during cell division? Reference: http://www.physicsforums.com/archive/topic/t-6668_Cell_size_is_proportional_to_ploidy.html Reference: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/Polyploidy.html 1.2 Multi-species creatures and inter-related species There is something on genetic heredity, where only a certain number of symbiotes are able to be within a host animal. ____________________________________________________________________