Male and female sand dollars are identical with no distinguishable markings to identify their sex. Researchers at the US National Library of Medicine report that larvae of the sand dollar Dendraster excentricus clone when predators are nearby. This means that sand dollar larvae have the ability to reproduce asexually when threatened in an attempt to protect and propagate their species.
Cloned larvae are much smaller in size than their original counterparts, making them difficult for predators to detect. In order for larvae to clone, their environmental conditions must be favorable for growth and reproduction. World View. Most beachgoers are familiar with the smooth, white, fragile sand dollars found washed up on beaches. These are skeletons of former live sand dollars and are considered prized finds. Their white color comes from having been bleached by the sun.
By gently shaking the fragile shell, you can often hear their five teeth rattling inside. Live sand dollars, on the other hand, are dark brown, or sometimes purplish or greenish and covered with short, nearly invisible bristly spines. Live sand dollars should never be collected.
For more information, visit www. Please purchase a subscription to continue reading. Subscribe today and support local community journalism. This includes access to the electronic replica edition of The Pilot.
As a print subscriber, you also have unlimited digital access. Connect your account now. Our best deal: Get all the news of Moore County delivered to your home each Wednesday and Sunday — and receive unlimited digital access to thepilot.
Sorry , an error occurred. Get Started. The tactic presumably works because hunters find smaller larvae harder to spot. As a result of the cloning process, the original larva halves in size. The newborn clones were smaller still and some were no bigger than a sand dollar egg cell, just an eighth of a millimetre across.
Almost all groups of echinoderms clone themselves in response to favourable temperatures and abundant food. In fact, asexual reproduction is a remarkably common tactic among plants and animals and is even used by some very unexpected species.
It brings several advantages; by cloning itself, an animal can rapidly produce large swathes of offspring to make the most of plentiful times and over time, asexual reproduction can even allow a lineage to divert different copies of its genes to new purposes. But this is the first example of an animal using a virgin birth to defend itself.
From their position on the sea floor, they have scant information about the risks that their young plutei may face and cannot alter the size of their eggs appropriately. Instead, Vaughan and Strathmann suggest that the cloning tactic allows the larvae themselves to alter their size in response to indicators of risk.
Reference: Vaughn, D. Predators Induce Cloning in Echinoderm Larvae. Science, , DOI: All rights reserved. Share Tweet Email. Go Further.
0コメント