THE FEMININE TOUCH
By Niki Wilson
1 Slipper limpets, a type of sea snail [caracol], have evolved a reproductive strategy that makes the most of their size at different points in their lifetime. Smaller limpets
are males, their tiny stature no barrier to producing energy-cheap sperm. Once larger, the limpets transition to females capable of investing energy into producing and
sheltering multiple eggs.
2 The exact size at which this sex change occurs varies between individuals. The presence of other slipper limpets can trigger or delay the change, but the mechanism
behind this social influence has been unclear. A new study from biologists Rachel Collin and Allan Carrillo-Baltodano at the Smithsonian Tropical Research Institute in
Panama provides the first step in solving this puzzle.
3 The researchers hypothesized that slipper limpets affect each other either via a waterborne chemical cue, which is a prevalent mode of signaling among aquatic species,
or via direct contact. They tested these possibilities in an experiment in which pairs of male limpets, one small and one large, were kept in plastic cups. In some cups the
snails were free to touch each other, but in others a mesh screen separated the two, while still allowing water to flow between their compartments.
4 It turned out that when limpets were allowed to touch one another, the larger males grew more quickly and generally changed into females faster than large males in
the partitioned cups. The smaller snails in the contact condition also delayed sex change longer than those partitioned. Physical touch between individuals, not chemical
messages carried through the water, thus plays an important role in timing the sex transition.
5 “That was kind of a surprise,” says Collin, given that slipper limpets spend most of their lives stationary and filter-feeding. “What we don´t know is how that contact is
facilitating transition.”
Adapted from Natural History March 2016.
The “social influence” mentioned in paragraph 2 most likely refers to the
