Why arrows? Strike with love darts!

Why let the cupids decide? Learn from the helicid land snails ( for e.g. Helix Aspersa) and do it yourself!

 Most of us know that snails are hermaphrodites, meaning they have both male and female sexual organs, and they do not self-fertilize. But do you know that their genitals are on the necks, right behind their eye-stalks?

 Not interesting enough?

 They are the cupids themselves! But instead of arrows, the “male” (male sexual organs at work) shoots mucus-covered calcium “love darts” during the final stages of courtship to its partner preceding copulation!

Initially, it was thought that the “love darts” were gifts of nutrients, just like how we give presents to the person we fancy. However, further research has shown that there is more to it!

dart with mucus

“Love darts” are actually filled with sperm. When it is being shot to the partner, it penetrates into the body of the recipient and may get digested. However, the mucus outside paralyses the partner’s reproductive tract, allowing the sperm to avoid digestion and thus greater number of sperms can make it to the sperm storage sacs within the reproductive system (Pomiankowski et al. 2001). Good news, as the stored sperms may be enough to be used over a period of months or even years! Say YAY to more offspring!

So, why is there a need for “love dart” when snails can just simply copulate? Sadly, the chance of survival of sperm through copulation is extremely low, like only thousands in millions. Thus with “love dart”, it provides the edge over reproduction because more sperm will be available: Applying Darwin’s theory of sexual selection, snails want to reproduce as much as they can, so if one snail has a way of ensuring that its sperm and not others’ is used to fertilize the eggs, it will have advantage over other snails and sire more offspring!

Sperm competition is somehow present. Basically, 2 or more snails can shoot “love dart” at the same partner (they are promiscuous!). The depth of penetration will determine how good the shot is; the deeper the higher amount of sperm stored! Thus, if one snail is better than the other, higher percentage of the newborn will be its offspring since its sperm has greater chances of being selected by the female for fertilization!

2 snails

Sounds cool right? While the “male” can enjoy shooting the “love dart” showing its affection, the recipient would be OOL (ouching out loud). This may be a very horrifying process because the darts are just like hypodermic needle and can rip off the skin of the recipients!  So sometimes snails will try to avoid getting hit on! How apt to human beings relationship, right? =p

References:

Website

“Are Snails’ ”Love Darts” Source of Cupid Lore?” by Ian Popple. National Geographic, February 13, 2002. URL: http://news.nationalgeographic.com/news/2002/02/0213_020213_wiresnail.html (accessed on 5 April 2010)

Journals

 Menno Schilthuizen, 2005. The darting game in snails and slugs. TRENDS in Ecology and Evolution 20 (11):581-584.

Janet L. Leonard, 1992. The “love dart” in helicid snails: a gift of calcium or a firm commitment? J.theor.Biol 159:513-521.

Pomiankowski.A and Reguera.P, 2001. The point of love. TRENDS in Ecology & Evolution 16(10):533-534

Photo

Dr Ron Chase- Home Pagehttp://biology.mcgill.ca/faculty/chase/ (accessed on 6 April 2010)

Leave a Reply

Your email address will not be published.