Hair Cells, Nucleomorphs, and Mongolian Barbecue

Today I Learned:
1) Hair cells (the kinds that grow hair, not the kind that let you hear) live much longer than the rest of the body after death, and Human corpses grow lots of hair very quickly for a few days after… becoming corpses. Especially on their toes.

Thanks to Bear Bear Bear for this tidbit.

2) A “nucleomorph” is a small, nucleus-like organelle found inside the chloroplasts of a few clades of algae* (for the curious, the cryptophyta and the chlorarachniophyta, and maybe the euglena? I couldn’t confirm this). They typically contain about three linear chromosomes of a few hundred kilobases total size, and invariably contain ribosomal genes (among others).

Why would a chloroplast have a nucleus-like structure, you might ask? Well, chloroplasts are thought to be descendants of photosynthesizing bacteria (probably cyanobacteria) that were endocytosed and symbiontized by an early eukaryote, the same way as mitochondria**. Plants and several other major eukaryotic lineages have chloroplasts directly derived from that line. Somewhere along the way, though, a eukaryote ingested and endosymbiontized *another* chloroplast-bearing eukaryote, an event called secondary endosymbiosis. This probably happened multiple times, but not *many* times — possibly as few as three. Since the endosymbionts in these cases were eukaryotes, they had nuclei.
In most of those lineages, those nuclei have been lost, but in a few, a presumably-vestigial nucleus remains — and this is the nucleomorph.

Thanks to Mengsha Gong for leading me down this rabbit hole of fascinating literature. Speaking of which, chloroplast evolution is really cool — I recommend “Recycled plastids: a ‘green movement’ in eukaryotic evolution” by Archibald and Keeling

*incidentally, I want to go on record saying that “algae” is terrible classification. It just means “green or red planty or slimy thing that photosynthesizes and doesn’t look like a traditional plant. Oh, and that isn’t a bacteria. Or archaea.”. The algaes are not particularly related to each other, and lots of things that are closely related to algaes are not considered algaes, so it’s useless for understanding relationships between species. Urgh.

**to head off one question I’m sure at least one of you is thinking (you know who you are), we have strong reason to believe that all chloroplasts are descendants of a single endosymbiont event about a billion and a half years ago (of course, there’s one lone exception — the amoeba Paulinella chromatophora, which relatively recently acquired a photosynthetic symbiont of its own). Most of the evidence for this is from comparative genetics — see the second section of “The Origin and Establishment of the Plastid in Algae and Plants” by Reyes-Prieto, Weber, and Bhattacharya for a short summary of the evidence, or the first half of “THE SYMBIOTIC BIRTH AND SPREAD OF PLASTIDS: HOW MANY TIMES AND WHODUNIT?” by Jeffrey Palmer for more details.

3) To get the most value out of Mongolian barbecue, stuff your bowl with vegetables before noodles — the noodles are more coherent and can be piled quite high. For even greater cost-efficiency, fan the edges of your bowl with carrots or other large, rigid vegetables to increase the effective height of the bowl. Thanks to Erik Jue for those tips.