Love (for nature and biodiversity) was truly up in the air on 12 February at the jampacked UPLB MNH Conference Room when Dr. Aimee Lynn Barrion-Dupo, MNH Curator, presented a seminar entitled "Diverse Truths About Lovestruck Spiders" as part of the museum's biodiversity seminar series.

Dr. Dupo, as associate professor at the Institute of Biological Sciences, interestingly is not a "spider girl" and has originally studied moths.

But having been heavily influenced by her father and late mother who are both distinguished spider experts, Dupo gamely talked about, in time for the Valentine's season the peculiar "sex and relationships" habits of spiders.

Men are from Mars, Women are from Venus

While this all-time best-selling book by John Gray tells that the psychological differences between men and women cause the most common relationship problems between them, Dr. Dupo said that in spiders, there exists "sexual dimorphism" which cause partner problems.

"Spiders just like other organisms, exhibit sexual dimorphism, meaning there are very obvious phenotypic differences between the male and female," she said.

"For example, female spiders are much bigger than their male counterparts," Dupo added.

The male's mating apparatus consists of abdominal testes and a pair of pedipalps to which males transfer semen while they look around for mates. Females have epigyne underside their abdomen, where males insert their pedipalps mating.

Spider pedipalps and epigyne are very distinct to species, hence they serve as "lock and key," she discussed.

It's a women-eat-men world

Spiders are very territorial and of course predatory. So it has been common knowledge among many that females, specially the Black widow, eat their mates after the deed has been done. This cannibalistic habit is said to be an advantage for females which will need energy for the reproductive process they will undergo.

Fortunately evolution has made ingenious solutions so that males would have a chance to survive the sexual encounters.

"Some males of species have mating spurs on their legs which they use to block the females while they try to insert their pedipalps," Dupo explained.

"They have been able to develop interesting sexual habits, such as making "salisi," she remarked, eliciting giggles among the audience. Dupo quickly added that males "quietly crawl up near the female (which in this case is preoccupied and eating) and quickly insert their pedipalps into the females genitalia."

But also to the audience's surprise, Dupo also said that studies on Micaria sociabilis, a ground spider, revealed that the males can also eat females, as a form of reversed sexual cannibalism. According to Dupo males of this species prefer to mate with the young and eat the old.

Spider love moves in mysterious ways

Interestingly enough, scientists have also recently observed a form of "monogamy" in spiders. "Male dark fishing spiders become immobile immediately after mating and die a short time later," Dupo exemplified.

The males die because of self-sacrifice. They fill up their pedipalps with semen up to the brink, then insert these into the females.

"Basically, these species engorge their pedipalps during mating until they curl up, become immobile and die after a few hours," she explained. Of course, since the dead male is an automatic food source, the behaviour becomes to the benefit of the female.

Spider sex: Business and recreation

Spiders have also become very creative to ensure they get to their "dates."

Dupo told the audience of the Nursery web spider Pisaura mirabilis which escapes cannibalism by offering gifts to the female.

Meanwhile, female Huntsman spiders advertise themselves by leaving pheromones which males detect; the male counterpart on the other hand have recently been found to deliberately make sounds which identify themselves to the females.

The males of the Peacock spider Maratus volans raise a flap from their abdomen to display colourful arches during courting mates.

"They raise their third legs and do a side-to-side dance," Dr. Dupo demonstrated.

This guy's in love with you

Spiders heavily rely on visual cues to recognize the other members of their species. "These cues are very also important in courtship," Dupo explained.

By making actions during courtship, spiders reduce their risk of being eaten. These cues enable mutual arousal and the assessment of a female's virginity by the male.

But what if a spider lacks any form of courtship rituals?

"There are males spiders from the Family Tetragnathidae which cannot discriminate their own from the females," she told the group.

"So, when males encounter other males, kapaan lang sila ng kapaan (they feel each other) until they give up.


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