Natures wonders: devoted spider dads unusual (Introduction)

by David Turell @, Thursday, November 24, 2016, 17:39 (1028 days ago) @ David Turell

These male spiders attend to their offspring in most unusual ways for spiders:

https://www.newscientist.com/article/2114025-the-devoted-spider-dads-who-fix-up-nurseri...

"Most male spiders bail out after mating – if they make it through the process alive, that is, as females of many spider species cannibalise their mates.

"But not this spider. Male Manogea porracea in South America not only help with childcare, they often end up as single dads.

"The male of the species builds a dome-shaped web above the female’s and sets about helping to maintain a “nursery” web. This is built between the two domes and holds the egg sacs (see photo, below).

:The males also defend the eggs from would-be predators and even remove water from the surface of egg sacs on rainy days.

***

"By the end of the mating season, 68 per cent of egg sacs are taken care of by males alone, says Rafael Rios Moura, an ecologist at the Federal University of Uberlândia in Brazil, whose team studied the spiders in the wild.

"Single dads improve the odds of offspring surviving compared with those who lose both their parents. Once the female is gone, the male moves closer to the egg sacs by moving to the female’s web (see photo, top). Moura found that significantly more hatchlings emerge from egg sacs taken care of by the males than those that had no parents around.

"When Moura set up experiments with predators, more hatchlings survived when the male was present, then when not, probably because they move aggressively towards intruders, fending off attacks.

"Four other spider species have been seen invading the M. porracea webs and attacking the egg sacs.

"The sheer volume of predators that M. Porracea have to deal with is likely what’s driving the males to help defend their eggs, says Linda Rayor, an entomologist at Cornell University in Ithaca, New York. “The male risks losing his entire investment if he doesn’t defend the eggs.” (my bold)

"Moura isn’t sure why the females often disappear.

***

"Either way, the fact that males often outlive females has probably contributed to its evolving to take on paternal duties – the first such known case in solitary species. The only other male spiders known to defend youngsters from predators are a social species from Africa, Stegodyphus dumicola

“This was my first time studying spiders, and we found this amazing system,” says Moura.

"Most male spiders don’t provide parental care because they don’t live as long as females, or they can’t be sure that they are really the father, (my bold)

"M. porracea males, though, are unique in both respects. Building a web above that of the female means they can be fairly confident in their paternity. And as they tend to live longer than the females, there are fewer females around for them to mate with. (my bold)

Comment: Certainly an instinct. How it developed cannot be ascertained from what is observed so far. Certainly my bolded portions show how the writer has anthropomorphized the male spider. Look at the photos.


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