By Guest Author 15/04/2016 1


by Professor Abby Smith, Department of Marine Science, University of Otago

Imagine if you found a creature that dropped a couple of fertilised eggs into a pouch and a week or two later gave birth to hundreds of babies.  Only a very few insects (and, oddly, armadillos) do this on land.  In the sea, only one kind of creature can do this – and they are virtually unknown.  Meet the cyclostomes.

On Sunday 10 April 2016, a group of 23 scientists from 13 countries gathered at the Melbourne Museum to take part in a workshop called “Friends of the Cyclostomes”.  Their goal: to find a way to draw these neglected and unknown marine animals to the attention of scientists, science funders, environmental managers and the public.

So what is a cyclostome?  Dr Paul Taylor from the Natural History Museum in London, the world expert on this group, described the important features of these marine colonial invertebrate animals.  While to the naked eye they might look like corals or moss or even just rock, under a microscope they show their real shape: small tubes containing interconnected tiny animals with waving tentacles.

Surviving as a colony

Cyclostomes are a group of bryozoans (“moss animals”) that are all that remain of a much bigger group that dominated the seas hundreds of millions of years ago.  They can be flat and encrusting, tall and branching, or blobby.  What they all have is a hard shell-like structure that is arranged in small tubes, each tube containing a single creature.  Together, the tubes make a colony that might be as much as 15 cm tall.  These creatures grow, reproduce, and survive as a colony.

Underwater shots from Cathedral Cave, Eaglehawk Neck, Eastern Tasmania, show why cyclostome bryozoans are sometimes called “lace corals” (even though they are not related to corals). Other marine creatures use the spaces around their fronds and branches for shelter. Credit: Dr Joanne Porter
Underwater shots from Cathedral Cave, Eaglehawk Neck, Eastern Tasmania, show why cyclostome bryozoans are sometimes called “lace corals” (even though they are not related to corals). Other marine creatures use the spaces around their fronds and branches for shelter. Credit: Dr Joanne Porter

While cyclostomes live in seas all over the world, they are especially large, abundant, and important in the waters around Australia and New Zealand.  They can be difficult to find, hard to identify, and are inedible (by humans): for these reasons studies about these animals are few and far between.  It’s particularly appropriate that experts have gathered here, in Melbourne, to discuss cyclostomes – Port Philip Bay is home to plenty of them.

A door into the Palaeozoic

Why do the Friends of the Cyclostomes think it’s important to study these creatures?  Palaeontologists are quick to point out that they are the only living relatives of the rest of the Stenolaemates – without the cyclostomes, our understanding of these ancient fossils would be much less.  Living cyclostomes open a door into the Palaeozoic.

These survivors from the Jurassic have some special features that may explain their long-term survival while most of their cousins became extinct over the ages.  They are among very few animals on Earth who produce only a few eggs, each of which divides itself up to produce hundreds of identical embryos.  How this “polyembryony” occurs and what it means for the evolution of these colonial animals is completely unknown.

High-magnification Scanning Electron Microscope photos show the wonderful shapes and sizes that cyclostome bryozoans can come in. Each tiny tube contains a separate animal, but the whole thing is a single interconnected colony. Note the scale bar in each photo; these critters are small! Credit: Dr Andrea Waeschenbach
High-magnification Scanning Electron Microscope photos show the wonderful shapes and sizes that cyclostome bryozoans can come in. Each tiny tube contains a separate animal, but the whole thing is a single interconnected colony. Note the scale bar in each photo; these critters are small! Credit: Dr Andrea Waeschenbach

Ecologists, too, think that cyclostomes are worth studying.  As they grow, they provide protected spaces and crevices for tiny fish and other creatures who have few other refuges out on the continental shelf.  When they are abundant, cyclostomes provide nursery grounds for many marine organisms – some of which are important food fish.

The ‘Friends of the Cyclostomes’ were convened by Professor Abby Smith (University of Otago) to address what she calls “the poor step-child of bryozoans”. After discussing gaps in our knowledge, the workshop developed a statement calling for action on the part of scientists, science funders, and public educators to bring this group of marine survivors out of the shadows.  Their Research Strategy was presented to the International Bryozoology Association at their meeting on Friday (at the Melbourne Museum) and was enthusiastically endorsed.  As the 17th IBA meeting comes to a close, scientists from all over the world head home with a better understanding of and a renewed commitment to cyclostomes: marine survivors.

Histological section of a cyclostome larval incubation chamber, showing developing embryos and larvae crammed in together. Credit: Dr. Andrey Ostrovsky.
Histological section of a cyclostome larval incubation chamber, showing developing embryos and larvae crammed in together. Credit: Dr. Andrey Ostrovsky.

One Response to “Cyclostomes: marine survivors from the Jurassic”

  • I got stuck, early on in the article, by the mention of armadillos, mammals that don’t drop “a couple of fertilised eggs into a pouch and a week or two later gave birth to hundreds of babies.” Obviously, what was really meant was woodlice, alias pillbugs, alias roly-polys (genus Armadillidium). If this is a New Zealand usage, it’s one I’ve never seen or heard before from NZ friends & acquaintances. My guess is that it was a spellcheck error.
    And then there’s the odd way in which cyclostomes are called “survivors from the Jurassic” as well as doors “into the Paleozoic.” Since the Jurassic began around 100,000,000 years after the end of the Paleozoic, it seems to me that professor Smith’s way of explaining the time scale of evolution is quite confusing. If the usual online references are right, cyclostomes evolved 100,000,000 years before the end of the Paleozoic Era, during the Ordovician Period of the Paleozoic, 475 million years ago or thereabouts. That puts their evolutionary emergence nearly a quarter of a billion years before the Jurassic.
    The Jurassic, then, has no special significance for cyclostomes, really. After all, every class of animal on earth today except for birds, and all plant categories except for angiosperms, could be called a “Jurassic survivor” as far as I’m aware. Come to think of it, the Jurassic didn’t end with an extinction event; every significant category of living creature survived the Jurassic. As such, “Jurassic survivor” seems to me a meaningless and confusing phrase . True, we don’t have dinosaurs, pterosaurs, ammonites, or trilobites these days, but those would more fairly be called Cretaceous non-survivors than Jurassic survivors.
    If a researcher feels that the best way to explain their work to a lay audience is by relating it to the Jurassic Park horror movie franchise, they’re in good company, as a lot of other scientists have done the same thing. But in that case, clearing away some of the fog of ignorance and misinformation about the prehistoric timeline seems to me like a high priority. Far too many people who have seen movies and TV shows about the prehistoric world think that cavemen rode around on the backs of dinosaurs, after all.