First...Go HERE and see this AWESOME video of Antarctic Starfish [Odontaster validus (99% of the ones in the pic) and some Lysasterias (the big white one) thrown in for good measure] feeding on the dead carcass of a dead seal pup!! Ha! take that mammals! And there's some big Antarctic nemertine worms (probably Parborlasia corrugatus) thrown in for good measure!!
What??? You want MORE time lapse???! Here's some Canadian Atlantic species thrown in for good measure! Looks like primarily Leptasterias polaris (big 6 rayed beast) and Solaster endeca (8-12 armed one with stripes)And to the music of Benny Hill no less!
And yet, EVEN MORE Time Lapse video?? here ya'go! A tiny aquarium asterinid extending its stomach out onto the glass to feed!
Finally, here's some Patiria miniata gliding over the bottom of the Pacific!
If ya' skip over all of the jellies and other non-echinoderm (but still pretty cool) animals, towards the end is a GREAT video of the swimming sea cucumber Enypniastes from the Gulf of Mexico!! (shown above):
There's been a flurry of "best of" type photos, including this cool shot of a bunch of brisingids (Novodinia spp.) and a goniasterid (looks like Evoplosoma) perched on a bunch of deep-sea corals in and around New Zealand (>1000 m based on the original captions). Its a light Echinoblog week but here in the US, its Thanksgiving week, and everything is just a little bit slower! Especially with everything getting colder and darker!
There will continue to be sporadic, light posts this week..with next week back to "normal"...
This week, we're talking about the Pacific Northwest Intertidal!!
And what animal is more iconic to this area then Pisaster ochraceus (family Asteriidae)-the familiar intertidal Ochre Star found on rocky, mussel-laden substrates on from Alaska to California to Mexico. Some more basic information is here. Interest on this species has shifted over the years and seems to change based on some of the "big science" of the day. Yet another sign of how the humble starfish has incorporated itself into the fabric of the BIG scientific picture!
So, today some highlights of the importance of the ever-humble intertidal Pisaster ochraceus and how its study has varied over the years....
1. The Keystone Species Concept-Ecology's Posterchild.Probably one of the most lasting ideas from the 1960s and 1970s was the hypothesis developed by ecologist Robert T. Paine who identified Pisaster ochraceus as a keystone species (keystone shown below in grey). To quote Wikipedia:
A keystone species is a species that plays a critical role in maintaining the structure of an ecological community and whose impact on the community is greater than would be expected based on its relative abundance or total biomass
This keystone is a crucial block in an arch that keeps it from collapsing. This is analogous for Pisaster's influence on the mussels and the other invertebrates that exist in a rocky intertidal ecosystem. The loss of the "keystone species" results in a drastic shift among these species....The idea has endured and while not embraced by everyone- remains a mainstay in basic ecology books. More details on this notion can be found here. Pisaster along with its prey, the mussel Mytilus are almost ALWAYS the featured example... the POSTER child for the keysone concept-and for this reason, is probably even better known then the Atlantic Asterias! This was (and continues to be) an important ecological notion during a time when the ecosystem and ecologists were in ascendance and ecology was a huge primary mainstay of biological research!
Time passes.
How has Pisaster changed to suit the most recent research paradigm??
2. Pisaster as a Portent of Change?? The Canary in the Cage of Climate Change?? Probably one of the biggest, new research directions these days?
Understanding Climate Change and in turn...increased ocean temperature, which has a HUGE impact! It affects ocean water chemistry. Water chemistry in turn can change everything from mineral absorption, feeding behavior, physiological systems to larval settlement. These in turn can have influence on MILLIONS of tiny larvae in the water. As well as the MANY adults those starfish grow into.
This translates into many people interested in the effects of increased temperature and heat relative to the ability of common species to adjust. Will Pisasterochraceus take on a new status as a possible indicator species (i.e., canary in a coal mine) for climate change effects in marine systems?
Here is a survey of three recent studies (2008-2009) that have looked at how Pisaster holds up!
Elevated water temperature and carbon dioxide concentration increase P. ochraceus growth!
(Diagrammatic graph by Echinoblog Art Department!)
This bucked the predictions that the decreased carbon dioxide resulting from increased temperature would prevent animals that use calcium carbonate to form their skeletons (such as coral)!!
Solar radiation plays a role in P. ochraceus habitat selection
(Diagrammatic graph by Echinoblog Art Department!)
Their paper details how Pisaster ochraceus was observed to increase the amount of colder water in their body cavity lowering their body temperature during the subsequent low tide in response to the temperature.
Sense it getting warm? don't like it? Just PUMP IT UP! with cold water! (see diagram above)
But climate change has a huge potential impact on animals that do this...to quote in their words:
When placed in a global change context, these results suggest that a continued increase in ocean temperature may compromise the ability of sea stars to avoid thermal stress during aerial exposure at low tide.
Has the humble Pisaster ochraceus gone from ecological poster child to a possible portent of climate change to come??? Time will tell....
But the short version is, that they are remote islands that are protected as a wildlife refuge. The Farallons are great for birdwatching and have lots of great (hopefully still...) pristine intertidal reef habitat.
Plus, as a bunch of rocky islands out on the outskirts of San Francisco Bay, you get lots of this...
Along with many of the classic California invertebrate fauna..
Leptasterias "hexactis", shown here with brooding eggs!! This is part of the Leptasterias species complex which I have written about here and here and, of course, the good ol' workhorse starfish Pisaster ochraceus, which I will be writing up in the blog later THIS WEEK!!!
and just because they're so dang beautiful...these mollusks too!!! This used to be called Tonicella lineata, but I think the name's been changed recently... ....and back in the Paleozoic when I took Intertidal Ecology, this thing was called Calliostoma, but I gots no idea what the kids are calling it these days! GO check out the Rocky Shore Partnership BLOG and I'll be back in a few days with some PISASTEROUS starfishy goodness for all o' y'all!
(one is Kate and one is Tim-can you guess which one?)
I have mentioned Tosia before on the blog...It is a starfish in the family Goniasteridae and its genus name is the Latin word for "Inestimable" which alludes, of course, to the animals' incredible natural beauty!
Tosia, asI define it, is found ONLY in Australia, where it is quite abundant and relatively well-known to the people who study marine biology thereabouts. One species in particular, Tosia australis, occurs widely throughout the temperate southern part of Australia.
(Image courtesy of Kate M. Naughton!)
Taxonomists have been noticing T. australis for YEARS and describing a myriad of species. Over the years, some FOURTEEN species have been described-but refinement of species concepts (and removal of unecessarily redundant species) have whittled down the total number to three.
It has led to the identification of what's called the Tosia australis species complex!! That's what happens when you have a lot of closely-related populations that all may or may not be different species.
Something NEW! Brooding Discovered! So, for an animal that occurs so close to shore, surprisingly little was known about it. In the 90s it was discovered that Tosia australis was a SPECIAL kind of starfish!! It showed an unusual reproductive behavior: BROODING juveniles! That is to say, its offspring live on the adults. Not too unusual in vertebrates, but VERY unusual in starfish!
Also, Tosia australis has been known since 1840-so it took over 150 years for them to discover that it brooded juveniles!! So, this led to some close observation.
(Image courtesy of Kate M. Naughton!)
So, the investigative talents of Ms. Naughton and Dr. O'Hara were applied towards the question!
Did the difference in larvae mode also translate into further biological differences??
During a museum visit to Melbourne, I was talking shop with Kate and Tim. I was pretty sure that all the morphological variation in the species complex would translate into regional or environmental differentiation VS. Tim who believed that they would split out by larval type.
Larvae in several other species is highly variable but often did not translate into phylogenetic differences..so I figured it would probably do the same here.
And in fact, I was SO confident I was right, that I wagered a gentlemen's bet with Dr. O'Hara that I would be right!
So-I said: "Go get the DNA and prove me wrong!"
And so they did (and had started before I had made the bet!)
Oops! Guess I just lost 10 bucks! The final analysis following a survey of many specimens from Victoria, Tasmania, and South Australia supported three different species, including something NEW that hadn't been observed before!!!
(Phylogenetic Tree inferred from COI and 16S RNA-and redrawn here by the Echinoblog Art Department!)
Several specimens from Tasmania and Victoria were supported on a separate clade as a NEW SPECIES. Kate came to call it Tosia neossia.The species epithet neossia is Greek for "nest" in reference to this species' brooding habit.
And here it is!
(Image courtesy of Kate M. Naughton!)
T. neossia is very similar to the well-known T. australis but, aside from a bunch of external morphological features, one important feature sets them apart....
The difference is in the Larvae (i.e., juvenile starfish)!
One of the fundamental differences here is that of the difference in larvae between Tosia australis and T. neossia!
The new species Tosia neossia had BOTTOM larvae with large yolky eggs (this kind of egg is called lecithotrophic)!!
(Image courtesy of Kate M. Naughton!)
Unlike more "typical" larvae, these tiny guys were negatively buoyant (that is to say, they sink rather then float)!
They are emitted from the mother and crawl along the bottom using little lobes to get around until they fully develop into larval adults. These little BOTTOM larvae (shown here as early stage larvae) can be seen here (courtesy of Kate Naughton!)
(Image courtesy of Kate M. Naughton!)
Here is where the larvae begin to change into what Kate calls the "tripod phase". These utilize a large lobe that helps move the larvae around before it begins to attach someplace on the ground after developing to the right stage....
(Image courtesy of Kate M. Naughton!)
....And finally, here is the settled larvae (oral view-looking up into the mouth). Note the tiny red dots, which will eventually become the eyespots!
This little fellow will develop into what will eventually become
(Image courtesy of Kate M. Naughton!)
....the adult!
This is in direct CONTRAST to Tosia australis which has SWIMMING juveniles that emerge from the aboral surface (via gonopores on the top surface). In contrast to the larval juveniles of T. neossia, T. australis has eggs that are postively buoyant and are covered with small CILIA!! That is, they have little beating hair-like threads that can keep them swimming before they settle out somewhere.
Summary Time!
In addition to the DNA and morphological evidence (you can go to the paper for details) the larval story goes like this:
Tosia neossia! Gonopores open on ORAL surface (i.e., DOWN) where the juveniles sink to the bottom. They are bottom-living and non-ciliated until they grow into juvenile adults!
Tosia australis! Gonopores open on ABORAL surface (i.e., UP) where the juveniles float and can sustain a swimming stage until they settle to the bottom and grow into juvenile adults
TWO species. VERY similar looking! but with DISTINCT juveniles growing into adults that are hiding right in plain sight!
Best 10 bucks I ever lost.
Thanks to Kate Naughton for helping me with images!
First...Go HERE and see this AWESOME video of Antarctic Starfish [Odontaster validus (99% of the ones in the pic) and some Lysasterias (the big white one) thrown in for good measure] feeding on the dead carcass of a dead seal pup!! Ha! take that mammals! And there's some big Antarctic nemertine worms (probably Parborlasia corrugatus) thrown in for good measure!!
