Axis formation in spider embryos

Blogging on Peer-Reviewed Research

Some of you may have never seen an arthropod embryo (or any embryo, for that matter). You’re missing something: embryos are gorgeous and dynamic and just all around wonderful, so let’s correct that lack. Here are two photographs of an insect and a spider embryo. The one on the left is a grasshopper, Schistocerca nitens at about a third of the way through development; the one on the right is Achaearanea tepidariorum. Both are lying on their backs, or dorsal side, with their legs wiggling up towards you.

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There are differences in the photographic technique — one is an SEM, the other is a DAPI-stained fluorescence photograph — and the spider embryo has had yolk removed and been flattened (it’s usually curled backward to wrap around a ball of yolk), and you can probably see the expected difference in limb number, but the cool thing is that they look so much alike. The affinities in the body plans just leap out at you. (You may also notice that it doesn’t seem to resemble a certain other rendition of spider development).

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Male pregnancy?

Yesterday’s discussion of future biological advances that will piss off the religious right had me thinking about other innovations that I expect will happen within a few decades that might just cause wingnuts to freak out. First thing to come to mind is that it will be something to do with reproduction, of course, and it will scramble gender roles and expectations…so, how about modifying men to bear children? It sounds feasible to me. Zygotes are aggressive little parasites that will implant just about anywhere in the coelom — it’s why ectopic pregnancies are a serious problem — so all we need to do there is culture a bit of highly vascularized tissue in the male abdomen that will serve as a secure home for a few months. We’ll have to play some endocrine games, too, which may effect his love life but will also prepare him to lactate post-partum. There’s the minor anatomical problem that the vagina is a unique tissue, and no, the urethra is not homologous or analogous (fortunately; we wouldn’t want to have to push an 8 pound baby through the penis, even if female hyenas can manage it) — but that’s what c-sections are for. Given money, time, and a few weird volunteers, it could be done.

The next question is, has it been done? Are there any other vertebrates that have males doing the hard work of pregnancy? There were the gastric brooding frogs, which one would think could have made the leap easily — the eggs were just swallowed and developed in the stomach — but only the mothers seemed to have done the job. They’re all extinct, anyway. Male frogs of the genus Rhinoderma brood their young in their mouths, but this is after external fertilization and development, so they’re actually simply holding larvae in a safe place — and they’re also endangered. The precedents aren’t promising.

There is an extremely interesting and successful example, though: the syngnathid fishes, sea horses and pipefish. In all 232 species, the female lays her eggs in a specialized male structure called the brood pouch, where they are fertilized and develop. It’s a true male pregnancy!

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Your mama’s soul doesn’t love you

If it existed, it might also be profoundly autistic and … diabetic? So science cannot disprove the existence of a soul, but one thing we’re learning is how much valued human properties such as love and attachment and awareness of others are a product of our biology — emotions like love are an outcome of chemistry, and can’t be separated from our meaty natures.

The latest issue of BioEssays has an excellent review of the role of the hormone oxytocin in regulating behaviors. It highlights how much biochemistry is a determinant of what we regard as virtues.

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