Are spiders mammals?

jaki01 (75)in #steemstem • 6 years ago

English version

Toxeus magnus

Its ant-like appearance (a form of mimicry) protects Toxeus magnus from 'spider wasps' (family Pompilidae), which, however, is not the subject of today's article. :)

Are spiders now in fact mammals? Or else insects?

I would bet that quite a few readers are now indignantly thinking to themselves "What a nonsense! As everyone knows, they are insects!"
Of course both is wrong. Spiders (class Arachnida) aren't insects (class Insecta) - what you can recognize by their eight instead of six legs - and certainly not mammals ... at least not in the taxonomic sense.

'Spider's milk' contains four times as much protein as cow's milk!

However, Chinese behavioral ecologists around Zhanqi Chen from the Chinese Academy of Sciences recently made an amazing discovery, which they published in the journal "Science" ^[1]: female specimens of the jumping spider species Toxeus magnus^[2} produce a milk-like liquid, whose protein content is, according to chemical analyses, about four times higher than that of cow's milk, and on which its offspring feed until shortly before reaching sexual maturity.
It's interesting to observe how in the course of convergent evolution similar behavior (in this case the suckling of young animals, which is surprisingly not only reserved for mammals) develops several times, independently of each other. At this point I venture of making a brief reference for the interested reader to 'lactating' birds^[3] and fishes (study^[4]).

As the scientists report, the young spiders are dependent during the first approximately twenty days of their life on this 'mother's milk'. While the female spider first releases this liquid in small drops into the nest, the baby spiders suck up their milk a week later directly at the mother's abdomen, where it leaves the birth canal. The researchers speculate that the milk-like liquid is formed from liquefied unfertilized eggs, with which some other invertebrates and amphibians feed their offspring.

Intense maternal care even after childhood

Even after this first stage of life, when the young spiders begin to search for food during the day, at night the mother continues to supply them with nutrient fluid until they are about 40 days old. While roughly 75 % of the offspring usually survive, this rate drops to about 50 % in nests from which the mother was removed. Interestingly, however, it is no longer above all mother's milk that increases the chances of survival: if the researchers blocked the milk flow but still left the mother in the nest, the survival rate of the young animals remained high. The reason for this may be, that, in addition to milk production, the mother keeps the nest clean by disposing of the waste produced by its children and, if necessary, repairing any damage.
Daughters are allowed to live together with their mothers until adulthood - whose cleaning behavior possible reduces the parasite load in the nest. The male young spiders have to go their own way a little earlier, a precaution which in all probability serves as prophylaxis against inbreeding.

Other Arachnids were also caught feeding.

Although parental behavior in this intensive form had not yet been observed in spiders, arachnids feeding their offspring have been described already earlier:

As researchers at Nancy University found out, the funnel-web spider Coelotes terrestris^[5] provides three different types of food to their young: caught prey, regurgitation of nutrient fluids and - it may sound macabre - its own body.^[6]
Females of the species Amaurobius ferox^[7] provide their offspring of the first generation with eggs of the following generation (whose maturation is prevented by specific interactions between mother and hatched young spiders) as food source.^[8]

Finally the link to a video presented by "Spiegel Online" about the Chinese scientists and their research object.^[9]

Sources:

#science #education #biology #spiders

6 years ago in #steemstem by jaki01 (75)

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theguruasia (68) 6 years ago (edited)

@jaki01,
I think they lay eggs isn't it? But I had that doubt, coz I heard Spider mom dies after giving birth to her kids!

Cheers~

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jaki01 (75) 6 years ago

Yes, they lay eggs, but often young spiders hatch shortly after birth. If the mother dies, and the offspring will eat her, differs from species to species.

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lauch3d (65) 6 years ago (edited)

interesting fact and at the same time it is kind of scary, when I think about how all the behavior, all the fleshy, pulsating warm things, the caring spider moms on earth are only a vehicle for information and that the real action takes place in a meta-world. Most people didnt like the thought that all the good and complex things like: faling in love, having children and giving milk to them , having fun and so on, is just about gen transfer.