planaria

Planaria Ripping Themselves Apart

Planaria are little flatworms with triangle heads, beady eyes, and the ability to regenerate after being cut in half. Bet you didn’t expect that last part, did you? Unlike cell division, planarian fission is violent and … well, weird. To stimulate these little guys to split, you have to first decapitate them. Unlike mitosis, planarian binary fission is simpler. There are no chromosomes that form or mitotic spindles. The worm simply holds on to a surface with its pharynx, uses peristalsis to create a waist, and pulsating muscular contractions rip the worm in half. The tighter the worm is able…

Chlamydomonas

One to(o) Many

Multicellular Evolution Theory Recently, a study showed that Chlamydomonas were capable for multicellular “evolution” when under predatory pressure. Basically, scientists set loose some hungry Paramecia into Chlamydomonas territory and things got stressful. I wanted to write a post about this because 1) you’ve seen videos and pictures of these microorganisms before and 2) it’s important to straighten out some misunderstandings about the results. Strength in Numbers Under the threat of predation, Chlamydomonas, usually flagellated and single-celled, will begin to form multicellular structures. Even after the threat was removed, they remained “multicellular”, though I prefer to call them “advanced colonies”. There…