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Palp facts

March 16, 2020

Male Redback Spider

Spiders are remarkable creatures particularly the way they reproduce. In male spiders there is no internal connection between where the sperm is produced and the organ which delivers it to the female, the palp. Palps are two hairy appendages (they look like small legs) that protrude from the front of the spider. Among other things the palp acts as a siphon to collect the sperm from the male abdomen (or from a silk sac into which the sperm is deposited), and as a device to deposit that sperm into one or both female spermathecae (sperm storage containers), where the sperm can remain viable for up to two years.

I was reminded of this when I got a call last week from Michelle at Yea High School wanting to know whether I wanted to come over and photograph some Redback Spiders (Latrodectus hasseltii) outside a science block window. The sperm transferring process sounds pretty straight forward until you look at the size discrepancy between male and female redbacks (see photo below). The standard image of a black spider with a red hourglass marking is that of the female spider. Male redbacks (pictured above left) look entirely different and are way smaller.

Male (left), hidden female’s legs (top centre), egg sac (top right)

Male wrapping up prey

The redback spider provides one of the few examples in nature where the male actively participates in sexual cannibalism by offering himself to be eaten during mating. It is thought that this prolongs the mating process therefore increasing the quantity of sperm transferred. It is also thought to increase the chance of its sperm being used for reproduction (and not another male’s) by decreasing the probability that the female will mate again (no sex on a full stomach!) thereby ensuring its genetic line.

It sounds incredible but it’s not palp fiction.

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