Milk-producing spider

In biology, organizing living things in categories is called taxonomy. Such categories are established based on shared characteristics of the members. These characteristics were usually visual attributes. For example, a red-footed booby (it’s a bird, silly!) is obviously different than a blue-footed booby, so we put them in different categories, which Aristotle called in Greek something like species.

Biological taxonomy is very useful, not only to provide countless hours of fight (both verbal and physical!) for biologists, but to inform us of all sorts of unexpected relationships between living things. These relationships, in turn, can give us insights into our own evolution, but also the evolution of things inimical to us, like diseases, and, perhaps, their cure. Also extremely important, it allows scientists from all over the world to have a common language, thus maximizing information sharing and minimizing misunderstandings.

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All well and good. And it was all well and good since Carl Linnaeus introduced his famous taxonomy system in the 18th Century, the one we still use today with species, genus, family, order, and kingdom. Then we figured out how to map the DNAs of things around us and this information threw out the window a lot of Linnean classifications. Because it turns out that some things that look similar are not genetically similar; likewise, some living things that we thought are very different from one another, turned out that, genetically speaking, they are not so different.

You will say, then, alright, out with visual taxonomy, in with phylogenetic taxonomy. This would be absolutely peachy for a minority of organisms of the planet, like animals and plants, but a nightmare in the more promiscuous organisms who have no problem swapping bits of DNA back and forth, like some bacteria, so you don’t know anymore who’s who. And don’t even get me started on the viruses which we are still trying to figure out whether or not they are alive in the first place.

When I grew up there were 5 regna or kingdoms in our tree of life – Monera, Protista, Fungi, Plantae, Animalia – each with very distinctive characteristics. Likewise, the class Mammalia from the Animal Kingdom was characterized by the females feeding their offspring with milk from mammary glands. Period. No confusion. But now I have no idea – nor do many other biologists, rest assured – how many domains or kingdoms or empires we have, nor even what the definition of a species is anymore!

As if that’s not enough, even those Linnean characteristics that we thought set in stone are amenable to change. Which is good, shows the progress of science. But I didn’t think that something like the definition of mammal would change. Mammals are organisms whose females feed their offspring with milk from mammary glands, as I vouchsafed above. Pretty straightforward. And not spiders. Let me be clear on this: spiders did not feature in my – or anyone’s! – definition of mammals.

Until Chen et al. (2018) published their weird article a couple of weeks ago. The abstract is free for all to see and states that the females of a jumping spider species feed their young with milk secreted by their body until the age of subadulthood. Mothers continue to offer parental care past the maturity threshold. The milk is necessary for the spiderlings because without it they die. That’s all.

I read the whole paper since it was only 4 pages of it and here are some more details about their discovery. The species of spider they looked at is Toxeus magnus, a jumping spider that looks like an ant. The mother produces milk from her epigastric furrow and deposits it on the nest floor and walls from where the spiderlings ingest it (0-7 days). After the first week of this, the spiderlings suck the milk direct from the mother’s body and continue to do so for the next two weeks (7-20 days) when they start leaving the nest and forage for themselves. But they return and for the next period (20-40 days) they get their food both from the mother’s milk and from independent foraging. Spiderlings get weaned by day 40, but they still come home to sleep at night. At day 52 they are officially considered adults. Interestingly, “although the mother apparently treated all juveniles the same, only daughters were allowed to return to the breeding nest after sexual maturity. Adult sons were attacked if they tried to return. This may reduce inbreeding depression, which is considered to be a major selective agent for the evolution of mating systems (p. 1053).”

During all this time, including during the emergence into adulthood of the offsprings, the mother also supplied house maintenance, carrying out her children’s exuviae (shed exoskeletons) and repairing the nest.

The authors then did a series of experiments to see what role does the nursing and other maternal care at different stages play in the fitness and survival of the offsprings. Blocking the mother’s milk production with correction fluid immediately after hatching killed all the spiderlings, showing that they are completely dependent on the mother’s milk. Removing the mother after the spiderlings start foraging (day 20) drastically reduces survivorship and body size, showing that mother’s care is essential for her offsprings’ success. Moreover, the mother taking care of the nest and keeping it clean reduced the occurrence of parasite infections on the juveniles.

The authors analyzed the milk and it’s highly nutritious: “spider milk total sugar content was 2.0 mg/ml, total fat 5.3 mg/ml, and total protein 123.9 mg/ml, with the protein content around four times that of cow’s milk (p. 1053)”.

Speechless I am. Good for the spider, I guess. Spider milk will have exorbitant costs (Apparently, a slight finger pressure on the milk-secreting region makes the mother spider secret the milk, not at all unlike the human mother). Spiderlings die without the mother’s milk. Responsible farming? Spider milker qualifications? I’m gonna lay down, I got a headache.

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REFERENCE: Chen Z, Corlett RT, Jiao X, Liu SJ, Charles-Dominique T, Zhang S, Li H, Lai R, Long C, & Quan RC (30 Nov. 2018). Prolonged milk provisioning in a jumping spider. Science, 362(6418):1052-1055. PMID: 30498127, DOI: 10.1126/science.aat3692. ARTICLE | Supplemental info (check out the videos)

By Neuronicus, 13 December 2018

Pic of the day: Dopamine from a non-dopamine place

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Reference: Beas BS, Wright BJ, Skirzewski M, Leng Y, Hyun JH, Koita O, Ringelberg N, Kwon HB, Buonanno A, & Penzo MA (Jul 2018, Epub 18 Jun 2018). The locus coeruleus drives disinhibition in the midline thalamus via a dopaminergic mechanism. Nature Neuroscience,21(7):963-973. PMID: 29915192, PMCID: PMC6035776 [Available on 2018-12-18], DOI:10.1038/s41593-018-0167-4. ARTICLE

Pic of the day: Total amount of DNA on Earth

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Approximately… give or take…

REFERENCE: Landenmark HKE, Forgan DH, & Cockell CS (11 Jun 2915). An Estimate of the Total DNA in the Biosphere. PLoS Biology, 13(6): e1002168. PMCID: PMC4466264, PMID: 26066900, DOI: 10.1371/journal.pbio.1002168. ARTICLE | FREE FULLTEXT PDF

By Neuronicus, 1 September 2018

Pic of the day: Skunky beer

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REFERENCE: Burns CS, Heyerick A, De Keukeleire D, Forbes MD. (5 Nov 2001). Mechanism for formation of the lightstruck flavor in beer revealed by time-resolved electron paramagnetic resonance. Chemistry – The European Journal, 7(21): 4553-4561. PMID: 11757646, DOI: 10.1002/1521-3765(20011105)7:21<4553::AID-CHEM4553>3.0.CO;2-0. ABSTRACT

By Neuronicus, 12 July 2017

Pic of the Day: Russell on stupid

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Reference: Russell, B. (10 May 1933). “The Triumph of Stupidity”. In: H. Ruja (Ed.), Mortals and Others: Bertrand Russell’s American Essays, Volume 2, 1931–1935.

The history of the quote and variations of it by others can be found on the Quote Investigator.

By Neuronicus, 6 November 2016

Pic of the Day: Neil on teaching creationism

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Dr. deGrasse Tyson’s picture is from Wikimedia released under PD and the quote is from a “Letter to the Editor” of New York Times retrieved from the Hayden Planetarium website on Nov. 2, 2016.

Pic of the day: Cortex

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Reference: von Bonin, G. (1950). Essay on the cerebral cortex. Ed. Charles C. Thomas, Springfield. ISBN 10: 0398044252, ISBN 13: 9780398044251

Image credit: geralt.The whole image: Public Domain

By Neuronicus, 15 September 2016

THE FIRSTS: The word ‘scientist’ (1834)

Scientist, by any other name…

History of science is, unfortunately, not among the mandatory classes required for earning a diploma that allows oneself to be called a scientist. Worrisomely, nor is Logic as a formal class. All the more the pity because in the Middle Ages, when the word science entered the English language, to have scientific knowledge meant you have arrived at it by following the Aristotelian way of logical reasoning (a.k.a deductions and inductions). To be fair, the word existed already in Romance languages with the same meaning: new knowledge obtained by applying the rules of Aristotelian syllogisms. By the way, Aristotle is also the guy to whom we owe the basis of the scientific method, but that’s a story for another day.

Although words like scientific or science were altogether frequently used with regards of the scholarly endeavors of the ladies and gentlemen of the early 19th Century (yes, there were ladies too that dabbled into the sciences, even if sometimes it was only to write about the spectacular discoveries and controversies of their time), the term scientist has been officially coined in 1834 by William Whewell. A man truly blessed in the art of words, being credited with coining a lot of other famous words like anode and physicist, he proposed the word in a review of a science popularization book written by one Mrs. Somerville. The circumstance of how this came to be is masterly imparted to us by Sydney Ross in a superb historical account of the word scientist, published in 1962.

For the rounded scientist or for the merely curious, I truly recommend the lecture of the referenced papers. They’re delightful!

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Reference 1. [Whewell W] (1834). Art. III. [Review of] On the Connexion of the Physical Sciences. By Mrs. Somerville. The Quarterly Review, 51: 58-61. FULLTEXT PDF at GoogleBooks

Reference 2. Ross S (1962). Scientist: The story of a word, Annals of Science, 18:2, 65-85, DOI: 10.1080/00033796200202722. FREE FULLTEXT PDF

P.S. I checked and Wikipedia is correct with the following statement:

“To be exact, the person coined the term scientist was referred to in Whewell 1834 only as “some ingenious gentleman.” Ross added a comment that this “some ingenious gentleman” was Whewell himself, without giving the reason for the identification. Ross 1962, p.72.”

Even if, by some very slim chance, the “ingenious gentleman” was not Whewell himself, Whewell did propose the term scientist in a more formal manner six years later in 1840 bringing more than just linguistic justifications, like the diversity of those engaged in scientific endeavors and how they don’t call themselves natural philosophers anymore.

By Neuronicus, 9 August 2016

Pic of the Day: First and Last Man on the Moon

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Today we celebrate the first instance the humankind stepped on the Moon. I thought only fitted to remind you of the last human there, too. As a bitter-sweet reminder that NASA is not something where budgetary concerns should lie.

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In 1987, the Apollo 11 Crew left their signed patch for safekeeping at NASA until is presented to the first manned mission to Mars. Credit: NASA

Links: NASA Apollo 11 Mission | NASA Apollo 17 Mission | Apollo 11 Patch to Mars 1 | Buzz Aldrin punching a conspiracy theorist that doubted the moon landing

By Neuronicus, 20 July 2016

Pic of the day: The most prevalent infection

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Reference: Flegr J, Prandota J, Sovickova M, Israili ZH (2014). Toxoplasmosis – A Global Threat. Correlation of Latent Toxoplasmosis with Specific Disease Burden in a Set of 88 Countries. PLoS ONE, 9(3): e90203. doi:10.1371/journal.pone.0090203. Article | FREE fulltext PDF

By Neuronicus, 22 March 2016

Pic of the day: Lungs’ taste receptors

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Reference: Deshpande DA, Wang WC, McIlmoyle EL, Robinett KS, Schillinger RM, An SS, Sham JS, & Liggett SB. (Nov 2010, Epub 24 Oct 2010). Bitter taste receptors on airway smooth muscle bronchodilate by localized calcium signaling and reverse obstruction. Nature Medicine, 16(11):1299-304. PMID: 20972434, PMCID: PMC3066567, DOI: 10.1038/nm.2237. Article | FREE FULLTEXT PDF

Pic of the day: Abundant vertebrate

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Fish Reference: Nelson, J. S. (2006). Fishes of the World. 4th ed. John Wiley & Sons, p. 209

Bird Reference: Strycker, N. (2014). The Thing with Feathers: The Surprising Lives of Birds and What They Reveal About Being Human. Riverhead Books