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Hitchhiking jellyfish, gonad-loving parasites and the skeleton shrimp

The views expressed are those of the author and are not necessarily those of Scientific American.


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Gonionemus vertens. Credit: Alexander Semenov

I recently came across this incredible underwater photography by russian marine biologist and underwater photographer, Alexander Semenov – head of the White Sea Biological Station deep-sea diving team from the Lomonosov Moscow State University. And as always with sea creatures, an investigation into the way they work reveals that they are truly just as bizarre as they look.

Pictured above is Gonionemus vertens, small species of jellyfish made up of a transparent bell around 2.5 cm in diameter, a set of brightly coloured gonads, a tan-coloured manubrium – or mouth – and a whopping 60 to 90 tentacles. On the end of each tentacle is a pad that secretes an adhesive substance for clinging onto any available surface, which is where the species’ nickname, ‘the clinging jellyfish’, comes from. This could also explain G. vertens’ unusual distribution.

According to a 1976 Advances in Marine Biology paper by C. Edwards of the Marine Station in Millport, Scotland, G. vertens likely has its origins in Portugal, and gradually distributed to the western Pacific waters skirting China, Korea or Japan. From here, somehow made it to the Pacific and Atlantic coasts of the United States and along the British and other western European coasts, and James T. Carlton of the Marine Science Center at Williams College in the U.S. has suggested that it did this during rhw 19th century by attaching itself to the hulls of ships and hitching a ride. Edwards suggests the distribution of G. vertens happened much earlier, with the clinging jellyfish attaching itself to ships and seaplanes that transported Japanese oysters around the world.

Strangely enough, when in the young, polyps stage, G. vertens populations have been reported as highly venonous in waters near Japan and Russia, but harmless in the Atlantic.

Hyperia galba Credit: Alexander Semenov

This little guy is Hyperia galba, a one-centimetre-long arthropod from the waters of the UK coast. It has a very distinctive ‘face’, into which two large,  light green eyes are set, and a body shape similar to that of a sea slater. The species is a keen parasite of large species of jellyfish and comb-jellies, and while usually content to feed off the zooplankton that gets stuck to the tentacles of its hosts, it is particularly fond of jelly gonads. According to a 1991 paper published in the Journal of Comparative Physiology B by Birgit Dittrich, H. galba larvae cannot survive without mature gonads to burrow into for nourishment and shelter.

Caprella septentrionalis Credit: Alexander Semenov

And this incredible looking creature is Caprella septentrionalis, a species belonging to a group commonly known as the ‘ghost’ or ‘skeleton’ shrimp, named after this slender, elongate body shape. The species can grow up to 3.2 cm long, and can be found among all kinds of algae, sea grass, sponges, hydroids, alcyonarians and tunicates all over the Northern Hemisphere. While it spends most of its time attached to seagrasses, filter-feeding the microscopic scraps that float by, when it has to get somewhere, the movements of C. septentrionalis are quite incredible. Like most other species of skeleton shrimp, C. septentrionalis moves with a measured and high-aching movement, just like an underwater caterpillar. Watch a video of the walking here.

Check out more of Alexander Semenov’s photos at his homepage and over at Wired.

Bec Crew About the Author: Bec Crew is a Sydney-based science writer and award-winning blogger. She is the author of 'Zombie Tits, Astronaut Fish and Other Weird Animals' (NewSouth Press). Follow on Twitter @BecCrew.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. notscientific 6:03 am 07/31/2012

    I saw Semenov’s photos on Wired as well and totally went Pinterest-crazy!

    Link to this
  2. 2. nyog@shaw.ca 3:44 pm 08/2/2012

    Very cool. Puzzled, though. Surely the “with” should be “without” in “H. galba larvae cannot survive with mature gonads to burrow into for nourishment and shelter.”

    Link to this

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