Submitted by Caroline Penn

A chance encounter with a Pacific Sideband Snail on a hiking trail on the slopes of Mt. Tuam on Salt Spring Island this fall led me to learn about the intriguing reproductive details of these snails.

Much like the Cupid (or Eros) of ancient mythology, these snails make use of a love dart during their mating ritual, which enhances their reproductive outcome.

The Sideband snail, Genus Monadenia, is already unique in that it is a pulmonate snail, and breathes through a cavity in its mantle like a few other land snails and slugs.

Pacific Sideband Snails are hermaphroditic, carrying both male and female reproductive organs. These are located internally but have an outer opening called a “genital pore” near their head. Close to this area they also have a dart sac, where their love dart is created and stored.

The love dart, or gypsobelum, is usually made of calcium carbonate, and not created until these snails have mated once. The mating dance of these snails is very tactile, involving their tentacles, and goes on for hours, until they align their genital pores. This stimulates eversion of their penis and also the firing of the love darts, which is somewhat haphazard, but may embed into the other snail’s body. Once they have fired their darts they copulate and exchange sperm with each other.

Recent research has shown that the love dart is covered in a mucous that contains allohormone a pheromone like substance that has an effect on the reproductive organs, ensuring that the sperm will be able to access the stored eggs and fertilize them.

These beautiful snails are threatened by habitat changes such as logging, fires, and urban development and activity as they are generally found in the leaf litter on the forest floor.

References:

https://academic.oup.com/mollus/article/82/1/1/2460173

https://www.jbc.org/article/S0021-9258(20)40763-X/fulltext

http://www.sccp.ca/species-habitat/pacific-sideband

Pacific Sideband Snail