Sea star's ability to clone itself may empower this mystery globetrotter


Date:
October 13, 2020
Source:
Smithsonian Tropical Research Institute
Summary:
The identity of wild cloning sea star larvae has been a mystery
since they were first documented in the Caribbean. The most commonly
collected cloning species was thought to belong to the Oreasteridae,
on the basis of similarity with sequences from Oreaster reticulatus
and Oreaster clavatus.



FULL STORY ==========================================================================
For decades, biologists have captured tiny sea star larvae in their nets
that did not match the adults of any known species. A Smithsonian team
recently discovered what these larvae grow up to be and how a special superpower may help them move around the world. Their results are
published online in the Biological Bulletin.


========================================================================== "Thirty years ago, people noticed that these asteroid starfish larvae
could clone themselves, and they wondered what the adult form was,"
said staff scientist Rachel Collin at the Smithsonian Tropical Research Institute (STRI).

"They assumed that because the larvae were in the Caribbean the adults
must also be from the Caribbean." Scientists monitor larvae because the
larvae can be more sensitive to physical conditions than the adults and
larval dispersal has a large influence on the distribution of adult fishes
and invertebrates. Collin's team uses a technique called DNA barcoding
to identify plankton. They determine the DNA sequence of an organism,
then look for matches with a sequence from a known animal in a database.

"This mystery species was one of the most common in our samples from the Caribbean coast of Panama," Collin said. "We knew from people's studies
that the DNA matched sequences from similar larvae across the Caribbean
and it matched unidentified juvenile starfish caught in the Gulf of
Mexico -- but no one had found a match to any known adult organism in the Caribbean. So we decided to see if the DNA matched anything in the global 'Barcode of Life' data base." "That's when we got a match with Valvaster striatus, a starfish that was thought to be found only in the Indo West Pacific," Collin said. "The is the first-ever report of this species in
the Atlantic Ocean. We could not have identifed it if Gustav Paulay from
the University of Florida didn't have DNA sequences from invertebrates
on the other side of the world." But why are the larvae common in the Caribbean if adult Valvaster starfish have never been found here? Are
the adult starfish hidden inside Caribbean reefs, or are the larvae
arriving from the other side of the world? V. striatus is widespread
but rare in the western Pacific. The few reports from collectors and
the confirmed photos on iNaturalist range from the Indian Ocean to Guam
and Hawaii. These starfish live deep in the reef matrix, only coming out
at night. So, it is possible that there are adults in the Caribbean that
have never been seen. But the other possibility, that the ability to clone themselves may allow them to spread around the world, is also intriguing.

"It's possible that the ability of the larvae to clone themselves is not
just a clever way to stay forever young," Collin said. "There's a natural barrier that keeps organisms from the western Pacific and the Indian
ocean from crossing the Atlantic to the Caribbean. After they make it
around the tip of Africa, they are met by a cold current that presumably
kills tropical species." "Just how cloning could help them get through
the barrier is still not known, but it's intriguing that another sea star species from the Indo West Pacific that was collected for the first time
in the Caribbean in the 1980s also has cloning larvae," Collin said.


========================================================================== Story Source: Materials provided by
Smithsonian_Tropical_Research_Institute. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Rachel Collin, Dagoberto E. Venera-Ponto'n, Gustav Paulay,
Michael J.

Boyle. World Travelers: DNA Barcoding Unmasks the Origin of Cloning
Asteroid Larvae from the Caribbean. The Biological Bulletin, 2020;
000 DOI: 10.1086/710796 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/10/201013191019.htm

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