Stresses of being a working mother

While I don't actually have any insight into the topic of this post (as related to humans), I'd like to share some findings from the world of spiders.

     Daiqin Li and Robert Jackson published a paper a few years ago investigating the role of predation cues on parental care in a spider. The focal species, Scytodes pallida, is a spitting spider that ejects a mixture of silk and venom from its fangs. Scytodes females carry their egg sacs around in their chelicerae (the parts attached to the fangs) until the spiderlings hatch.

A female Scytodes carrying her egg sac in her chelicerae

     This is clearly awesome, but Scytodes has a problem: it is preyed upon by another spider called Portia labiata. Portia belongs to the jumping spider family, known for excellent vision and surprisingly sophisticated cognitive abilities. Portia has learned (over evolutionary time) to preferentially consume Scytodes that are carrying eggs. The benefits are two-fold: 1) Portia gets to eat the Scytodes mother and her eggs, and 2) Portia is more successful at capturing Scytodes, since the eggs must be dropped before defensive spitting can commence.

A menacing Portia, the spider that eats other spiders

     The question Li and Jackson were interested in is whether Scytodes has any way to resolve the conflict between needing to carry eggs and defend itself from Portia. The authors predict that Scytodes may change traits related to egg hatching in order to solve this problem.

     Egg-carrying Scytodes were presented with volatile chemical cues (basically, smells) left behind by Portia. These cues could come from silk, feces, or anything else the spider leaves behind. The authors measured the time until the eggs hatched, how big the spiderlings were, and the proportion of eggs that failed to develop. They found that eggs hatched sooner and produced smaller offspring when Portia cues were present (compared to a control without any Portia cues). What's even cooler is that this effect of shorter incubation and smaller offspring was even stronger if the Portia providing the cues had recently eaten Scytodes. Although there was no statistically significant effect on the proportion of eggs that failed to develop, the trend was the same as incubation time.

Eggs from females under risk of predation hatched sooner

     What this all means is that Scytodes can sense predator cues and respond by speeding up the development of its offspring. The benefit is that the sooner the egg sac is gone, the sooner Scytodes can defend itself from Portia. A potential cost is that the offspring will be smaller than usual, which may put them at a disadvantage later in life. Presumably, this is better than getting eaten before the spiderlings even get to hatch. What a tough world these spiders live in! If only they could invent spider day care.

     Just how Scytodes changes the incubation time is not known, but this just demonstrates how science works. An observation leads to a question, and the answer to that question creates more questions. Scientists never stop questioning, and it seems like we may never run out of mysteries to solve. How's that for job security?