Anti-caturday post

I have been trying to understand the peculiar popularity of these posts about sharp-clawed carnivores called “cats”, and near as I can tell it has something to do with the property of cuteness. “Cute” seems mostly undefinable, however, but usually seems to involve playful juvenile behavior by large-eyed creatures. This seems to qualify: Sepiolid burying behavior. It’s adorable!

It’s cute how it so quickly conceals itself to lurk and wait for prey to swim by.

I’m still trying to grasp the concept of cute, though. Is this cute? It’s a giant Pacific octopus swimming up an Alaskan creek.

Do you live near water? Then you are not safe. The giant tentacled molluscs will find a way to get to you, and I find that charming.

(Also on FtB)

Botanical Wednesday: Yes, mistress

I don’t know whether to be intimidated or aroused by the description that goes with this image. Or both.

i-3b36017fa0f4b2a1d96a41e4d1387d6a-bucketorchid.jpeg

The dominatrices of the orchid world are the Bucket Orchids. They are pollinated by orchid bees that want the plant’s aromatic oils to use them in their courtship dance with females. But what the poor bees go through to get them!

The orchids secrete the aromatic fluid into the bucket-shaped lip, and
the bee will often fall into the fluid at the bottom of the bucket. There are knobs inside that go one way but the rest of the bucket is lined with smooth hairs pointing downwards and so that they can’t climb back up.

Finally following the knobs, the bees come to what looks like freedom, a spout exiting. The orchid, however, has no intention of letting the bee go yet. Instead, it constricts the spout and presses pollen packets against its thorax, keeping it there until the “glue” has set. Finally, it is set free to go and find another orchid and this time displace the pollen packets to pollinate it. It can take up to 45 minutes for the bee to escape the orchid as it is kept trapped for the orchids sexual needs and bent to her will.

Wait, this sounds like my home life!

(Also on FtB)

Bacterial fossil doubts resolved

I raised a few questions about those 3.4 billion year old bacterial fossils, primarily that I was bugged by the large size and that they cited a discredited source to say that they were in the appropriate range of diameters for bacteria. Now my questions have been answered by Chris Nedin, and I’m satisfied. In particular, he shows data from 0.8 and 1.9 billion year old fossils in which the bacterial sizes are in the same range. It’s also a good review of the other evidence used to infer that they actually are bacterial microfossils.

(Also on FtB)

A questions about those ancient bacterial fossils…

Both Jerry Coyne and Larry Moran have good write-ups on the recent discovery of what are purportedly the oldest fossil cells, at 3.4 billion years old. I just have to add one little comment: a small, niggling doubt and something that bugs me about them. All the smart guys are impressed with this paper, but this one little thing gives me pause.

I’m a microscopist — I look at micrographs all the time, and one of the things I always mentally do is place the size of things in context. And I was looking at the micrographs of these fossils, and what jumped out at me is how large they are. They’re not impossibly large, they’re just well out of the range I expect for prokaryotes.

Most prokaryotes have diameters in the range of 1-10µm, while typical eukaryotes are about 10 times that size. There are exceptions: Thiomargarita gets up to 500µm across, so like I say, there’s nothing impossible about these cells, it’s just that the micrographs show lots of cells with 10-30µm diameters. And the authors come right out and report that:

The size range is also typical of such assemblages, with small spheres and ellipsoids 5-25 µm in diameter, rare examples (<10) of larger cellular envelopes up to 80 µm in diameter, and tubes 7-20 µm across (see ref. 24).

How odd. When I poke into the nervous system of an embryonic insect or fish, those are the sizes of cells I often see (well, except there aren’t many tubes of that size!). When I poke into a culture or embryo contaminated with bacteria, they’re much, much smaller. So maybe paleoarchaean bacteria tended to be larger? And they do cite a source for that size range of prokaryotes…

Then here’s a new problem: the source cited, ref. 24, is the Schopf paper, the older paper that claimed to have found ancient bacterial fossils, a claim that has since been discredited! Uh-oh. What they’re calling “typical of such assemblages” is a data set that’s widely considered artifactual now. Furthermore, that’s a simplified version of what Schopf said — he actually broke the sizes down into categories, and the range was more like 1-30 µm.

  • Very small solitary, paired or clustered rods (ca 0.75 µm broad, ca 1.5 µm long), inferred to be prokaryotic (bacterial) unicells: one unit (ca 2600 Myr old), one morphotype.
  • Small, solitary, paired or clustered coccoids (average diameter ca 3 µm, range ca 2-5 µm), inferred to be prokaryotic (bacterial, perhaps cyanobacterial) unicells: three units (range 3320-2600 Myr old), three morphotypes.
  • Large solitary or colonial coccoids (average diameter ca 13 µm, range ca 5-23 µm), inferred to be prokaryotic (bacterial, perhaps cyanobacterial) unicells: three units (range 3388-2560 Myr old), four morphotypes.
  • Narrow unbranched sinuous filaments (average diameter ca 1.25 µm, range ca 0.2-3 µm), with or without discernable septations, inferred to be prokaryotic (bacterial, perhaps cyanobacterial) cellular trichomes and/or trichome-encompassing sheaths: 10 units (range 3496-2560 Myr old), 17 morphotypes.
  • Broad unbranched septate filaments (average diameter ca 8 µm, range ca 2-19.5 µm), inferred to be prokaryotic (perhaps cyanobacterial) cellular trichomes: four units (range 3496-2723 Myr old), 10 morphotypes.
  • Broad unbranched tubular or partially flattened cylinders (average diameter ca 13 µm, range ca 3-28 µm), inferred to be prokaryotic (perhaps cyanobacterial) trichome-encompassing sheaths: five units (range 3496-2516 Myr old), five morphotypes (e.g. figures 3a-e and 4l).

So Schopf was reporting larger cells in his older samples, and now Wacey et al. are describing what look like very large cells to me in their 3.4 billion year old rocks. I’m not a microbiologist so I could be way off on this, but…isn’t this just a little bit strange? Maybe there are some micro people out there who can reassure me that this isn’t a surprising result.

Wacey D, Kilburn MR, Saudners M, Cliff J, and Brasier MD (2011) Microfossils of sulphur-metabolizing cells in 3.4-billion-year-old rocks of Western Australia. Nature Geoscience Published online Aug. 21, 20110 [doi:10.1038/ngeo1238]

(Also on FtB)