Another Worry From Global Warming: Parasites that EAT Starfish SPERM!!!

(Figure 1b from Stickle et al. 2005, Invertebrate Biol. 120: 88-95)

This week, we have what sounds like a horrific title: Starfish Sperm Eating Parasites!

Parasites are weird and freaky...and how many people out there knew that Sea Stars even HAD parasites???

yes! they do. So, let's get to it!

1. The Parasite- and....it does WHAT???
So, in the early 2000s, Bill Stickle, a marine biologist at Louisiana State University authored several studies looking at the parasitic relationship between a ciliated protozoan Orchitophrya stellarum (described way back in 1907) and several different sea stars from the North Pacific.

(Figure 1A from Stickle et al. 2005, Invertebrate Biol. 120: 88-95)

in a series of papers published by his lab, including this one (2005), this one (2007) and this one (2001) (this wasn't all of them) , they describe the close relationship this parasite has with its host(s).

2. Orchitophrya LIVES AMONG and EATS starfish Sperm! Yes that's right! These little single-celled animals probably enter through the gonopores (although there's lots of big spaces for a tiny critter to enter on a starfish) and invade the gonads/testes of male sea stars (location indicated below with red arrows) and get right to work eating up all of their little starfish baby-makers!

Interestingly, the parasites do NOT attack the ovaries (female reproductive structures).

(modified from Wikipedia commons)

Apparently, these parasites were FILLED with phagosomes (digestive bodies) which included numerous sperm in various stages of digestion.

Here is a pic of one of these guys right in the middle of a spermalicious FEAST!

(Figure 1b from Stickle et al. 2005, Invertebrate Biol. 120: 88-95)

This has some MAJOR impact on the amount of sperm produced by the host species, which are particularly ripe in brooding winter males and spring-summer broadcasting males (i.e., when they are ejecting sperm into the water and females are ejecting eggs into the water at the same time).

But WHAT species? Well, apparently, these parasites like asteriids..which are very familiar beasts such as (this is an incomplete list)

Pisaster ochraceus
Leptasterias spp.
and...the North Pacific Asterias amurensis (now invasive in Australia). Early studies on the interaction between the parasite and their hosts were actually performed on this species...
The Atlantic Asterias forbesi, was actually one of the first species discovered to host the parasite-from populations in Europe and the east coast of North America, which may be where it originated. But its unclear how/where this happened..

3. Orchitophrya is a KICK-ASS Starfish sperm-eating Parasite! (but can live life on its own)

(Figure 1A from Stickle et al. 2005, Invertebrate Biol. 120: 88-95)

Stickle's lab discovered that the parasites CAN actually live outside and away from sea stars, but they become smaller, they become less developed and their mouth actually moves away from the front of their body!!

Now, when you FEED them asteriid starfish sperm? ALL of these changes REVERSE themselves!! So, Orchitophrya is considered a "facultative" parasite...that is it can live free of the host when it needs to do so.

The range of the parasite seems to have gotten as far south as Washington but based on several of the surveys taken there were only a few regions that had unusually low sperm outputs from parasitized male adults.

3. When it gets (global warming) HOT, the parasites get BUSY.
There has been much concern over what will happen to various marine invertebrates as global warming intensifies. And there has been some concern about how, even our local faunas, such as the Ochre Stars will be affected.

A new paper by Amanda Bates, Bill Stickle and Christopher Harley in the Journal of Experimental Marine Biology and Ecology uses some lab results to postulate what might happen to Orchitophrya under higher temperature conditions...

The authors isolated the parasite and cultured it. Then exposed it to Pisaster ochraceus
and Patiria miniata
at variable temperatures-the control versus 10 and 15 degrees C.

Interestingly, the parasite much prefers Pisaster to Patiria, which further details how specific the relationship is...Orchitophyra likes asteriids (e.g., Pisaster, Evasterias, and Asterias)

Higher temperatures led not only to increased DENSITY of parasites but also infection INTENSITY.. That is, greater amounts of the male testes were infected.

(Fig. 3 from Bates et al. 2010)

The end result? After 21 days, so much of the sperm in the testes has been consumed that effectively, the hosts have partly to completely lost their "reproductive potential". That's effectively castration (emasculation?). Yikes!

So, what does that mean?

As all good scientists do, the authors warn that lab results don't always translate directly into what you see out in the "wild". There's a lot of variation in temperature of local areas and of course, the various populations and so on.. and more work needs to be done..

HOWEVER, they do note an interesting case of temperature increase of 1.5 degrees C per decade from 1976 to 1997 in Tokyo Bay. The temperature increase corresponded to the first detection of the parasite in Tokyo Bay in 1996! So, maybe some cause for concern is here?
This is a great example of how global warming's effect could conceivably extend beyond simply the direct effects on marine faunas. Who knows what weird combination of dominos could be altered?

In this case, the changes in water chemistry may benefit some asteroids (as indicated here), but on the other hand, SO will their parasites!

Speaking of unintended impacts, I can only wonder how many extra hits I will get from disappointed people who were looking for out of context key words in this blog's title... :-)

Pycnopodia Juvenile Stage Has Arrived!!

July 16 UPDATE!!! by Allison Gong:
What does Pycnopodia look like before it starts growing into an "adult"??? Find out below at the bottom in Green!!

My colleague Dr. Allison Gong at the UC Santa Cruz Long Marine Laboratory recently had the fortune to observe the spawning and early larval development of Pycnopodia helianthoides-the sunflower star one of my favorite animals!

(This and all pictures courtesy of Allison Gong, UCSC)

Info and the comments below are graciously provided by her (seen above in her natural habitat)!

Apparently the gametes collected were produced by these hefty beasts on display at the Seymour Center. There are four in the aquarium. Each one may be either the mother or the father of these larvae.

(This and all pictures courtesy of Allison Gong, UCSC)

Allison says: "This is a 3-day-old early dipleurula larva. It is basically a ciliated blob with an invagination in the flattened posterior end. The internal tube and knob structures are the developing larval gut."

(This and all pictures courtesy of Allison Gong, UCSC)

Allison says: "This photo is essentially the same thing, photographed under dark-field conditions for a rather cool effect."

(This and all pictures courtesy of Allison Gong, UCSC)

A neat black and white shot...

(This and all pictures courtesy of Allison Gong, UCSC)

Two More!!

(This and all pictures courtesy of Allison Gong, UCSC)

UPDATE Ladies and Gentlemen, we have BIPINNARIA!!! (an intermediate larval stage of starfish)

Sez Allison: "These guys sure don't develop as quickly as urchins! At 14 days, the larva has reach a stage called the bipinnaria. It's sort of a more elaborate version of the dipleurula. In this ventral view, you can see the stomach quite clearly as the darkish ovoid shape in the bottom part."
"Here's a left-side view of a different larva at the same stage. These guys are really transparent, and it's hard to get a feel for their three-dimensional structure because the camera focuses on a single plane."

"These guys happened to swim under the objective lens at the same time, so I snapped a shot of them. In this photo you're getting both a ventral and a dorso-lateral view."

10 June 2009-Allison Sez: These larvae are growing so slowly! I'm used to things happening more quickly. Oh well. This is a ventral (front) view of a 22-day-old bipinnaria larva. The internal ovoid structure in the lower half is the stomach, with dark food cell visible inside. Here's a trick to "seeing" the 3-dimensional structure in a 2-d photo: Imagine a capital letter 'c' and rotate it 90 degrees along its vertical axis. You're now looking into the "opening" of the 'c', right? That's exactly the view of this larva. The roughly triangular object on the top and the squarish object on the bottom correspond to the ends of the 'c'. Confusing, isn't it?
Okay, here's a nice lateral view. The gut is nicely visible in this picture. You can see the elongated esophagus and the sphincter where it meets the stomach. You are looking at the larva's left side, with its anterior end up and its posterior end down.
Bipinnaria larvae reaches the 29 day stage!

Sez Allison: We had a near miss late last week and lost about half of the larvae. I think maybe they didn't like the food we were giving them. We've altered the diet and the remaining larvae seem happy, although some of them may be arrested at an early stage of development.

This individual was the most advanced of all the larvae I observed today. At 29 days it is starting to develop little nubbins that may grow into long brachiolar arms--at least, I hope they do!--and measures 850 microns in length.
Sez Allison: This larva, at the ripe old age of 49 days, has reached the brachiolaria stage. It measures a whopping 1.5 mm long! The gut is a golden color because we've been feeding them a mixture of green algae and diatoms.

The simple band in the earlier stages has been elaborated into pointy little nubbins called brachiolar arms. In other species, such as Pisaster ochraceus, the arms get really long; I don't know how long they'll get in these Pycnopodia larvae. We'll have to wait and see.

Sez Allison: Whoa. Huge progress made in the last week! The larvae are 55 days old now and have *finally* started growing the long arms we've been expecting for weeks. I shot this photo through my Wild dissecting scope to get the cool effect of a dark background. Couldn't entirely get rid of the unwanted glare, though. Oh well.Sez Allison: Here's a closer shot of the same larva. The brownish structure in the bottom of the larva is its stomach.
From Allison: Isn't this gorgeous? At 66 days (7 weeks and counting) the larvae have reached the advanced bracholaria stage. The arms are longer and the larvae wave them as they swim around. These guys are still feeding, although they haven't grown much. It looks like they max out at about 1.5 mm in length. This particular larva may not be entirely competent (i.e., ready to metamorphose) yet, but it's getting close.
SETTLEMENT!!!

From Allison: Ta-dah! One larva has begun the process of metamorphosis. It has attached itself to a small piece of mussel shell with some suckers on the anterior end. The round structure you see at the top of the animal is the juvenile rudiment, or the earliest stage of the juvenile body, containing the water vascular system's first 5 tube feet. You can see that the brachiolar arms are still there. At this point the critter can no longer feed, as it completely re-arranges its entire body, and survives on energy reserves it put away as a feeding larva.

I never get tired of watching this kind of metamorphosis, in stars or urchins. It's the coolest thing out there. In a matter of a few days the animal transforms from a bilateral swimming creature to a pentaradial crawling beast, with a full scale re-arrangement of its external and internal anatomy. Larval parts will be resorbed or discarded, and new juvenile structures will be formed.

Amazing, isn't it?
From Allison: A star is born! The little guy we've been monitoring, seen here in side view, has completed metamorphosis, and as far as I can tell is doing fine. All of the larval body has been resorbed now, and the critter is a little round disc with tube feet and spines. It's not very active right now but I think that's because it's recovering from the trauma of metamorphosis.

From Allison: I tried to get a better view of the aboral (i.e., top) surface but immediately lost contrast because the baby star is almost the same color as the bit of mussel shell it's sitting on. At least in this view you can see that it's radial now. Quite a change from the bilateral larva it was a week ago, isn't it?

I think these new juveniles will fast for a number of weeks, living on energy reserves they packed away while they were feeding larvae. It remains to be seen whether or not we can figure out what to feed these tiny guys, but we'll try to keep them going and will hopefully be able to document how all of the arms develop. Remember, these stars have ~20 arms as adults, although they start out with the requisite echinoderm 5, and we're interested in seeing if there's a pattern to how all the arms form.
So, a late addendum... have you ever wondered what Pycnopodia looks like when they are just wee babies?? Here ya' go..
According to Allison, this is what they look like 23 days past settlement. They have FIVE rays just like ANY other SEA STAR. Neat, eh??

From here, they grow onto the enormous, multi-rayed forms that we know and love! I suspect that takes AT LEAST several months to years.... so, leave em' alone when you find em as adults! It probably takes a LONG time for them to reach even a 6 inch diameter!

"The Most Common brittle star in the world"?? The tropical-global invasion of Ophiactis savignyi!!

(this image from the Smithsonian guide to Indian River Lagoon inverts)

Of ALL the living echinoderms (starfish, sea urchins, sea cucumbers, crinoids, etc.), there's one group that has has become numerically dominant, successfully infiltrated MORE nooks, crannies, and little niches than ANY OTHER echinoderm, and probably has MORE species then any other of the living echinoderms..

That group? The BRITTLE STARS (i.e., the ophiuroids)

Some species of brittle stars have a nearly WORLDWIDE distribution. One case in point-one species that famous/infamous echinoderm taxonomist Hubert Lyman Clark called "the most common brittlestar in the world": Ophiactis savignyi!!
Ophiactis savignyi was described back in 1842 and literally occurs in the tropics ALL over the world in the tropical Pacific, Atlantic and Indian Oceans. This includes Hawaii, Egypt, Australia, Africa, Asia and so on.

Its a very tiny species and isn't much better then the tip of a pen!
This species reproduces both sexually and asexually, so when you find them, there's usually a LOT of them...
Its unusual for a brittle star in that it has 6 rays instead of 5. Its a species that is frequently encountered in the coral rubble in tropical aquaria.
The data for this post came from a neat paper by Roy and Sponer (2002) in the Proceedings of the Royal Society of London! who were studying the biogeography and population dynamics of the globally distributed tropical brittle star Ophiactis savignyi...

The authors collected samples of this species from throughout the tropics!!

(redrawn from Fig. 1 in Roy & Sponer)

They then sampled DNA (specifically the COI mitochondrial DNA gene) from each of the sampled specimens indicated above.
The gene chosen is most useful for distinguishing differences (i.e., the divergence) among populations. So, the DNA is used as kind of a "signature" for determining WHERE the specimen (within this single species) came from..

They can then analyze and compare the DNA in order to group or cluster where the "signatures" originated! Bear in mind, that for the most part, the external differences in this widely distributed species are likely very minute if present at all.. So DNA is usually the only way to determine where these specimens came from..
...AND you get a tree that looks like this:

(redrawn from Fig. 2 from Roy & Sponer 2002)

So, what does this tell you?

Well, on the lower part of the tree in bright GREEN is the Atlantic lineage. That is, those specimens sampled that were originally from the western Tropical Atlantic: Florida, Brazil and so on...

The entire remaining tree in red and blue is essentially Indo-Pacific, that is from areas throughout the Indian and Pacific Oceans-Hawaii, South Africa, Sri Lanka (off India), the Philippines, Guam and so on..

BUT WAIT. Is that GREEN I see, lodged up there amongst the RED? There are ATLANTIC specimens that cluster closely with the PACIFIC ones!

In other words, individuals collected from the Atlantic, show essentially NO (or very little) genetic differences with Indo-Pacific specimens. This implies that at some point a population of Atlantic Ophiactis savignyi migrated from the Indo-Pacific region..

They were also able to assess that there was essentially no genetic change over 3 million years!

So, what explains the presence of Atlantic haplotypes among the Indo-Pacific ones???
This suggests that there has been RECENT genetic mixing and long-distance dispersal of these different populations!!

When and HOW could this mixing have happened?? The authors began digesting the results:

How could Atlantic members be dispersed to the Indo-Pacific? Could ocean currents be the mechanism responsible for the pattern?
In most cases, long distance distribution of species, such as this, is usually due to ocean currents moving larvae away from their "home" or natal sites.

Various current hypotheses were considered.

Migration around the tip of Africa (Cape of Good Hope) was rejected because of the cold Benguela current, which would have likely killed the tropical larvae right away.
And the cold Antarctic Counter Current was thought of being similarly too cold to permit the tropical larvae to pass around the tip of Cape Horn to reach the Indo-Pacific!!

(this image from Olelog!)

They further reject either of these "migration paths" because they also don't see parallel patterns in other marine invertebrates with similar distributions.

So what does that leave?? If all of the "conventional" means of dispersal are eliminated? What's left??

Was Ophiactis savignyi artificially introduced to the Indo-Pacific???
After having eliminated currents as a means of transporting the larvae of Ophiactis savignyi, the authors considered additional facts:
1. There is low genetic diversity
2. Ophiactis can divide asexually
3. Ophiactis is VERY widely distributed.

These all suggest colonization/invasion, followed by a rapid and widespread distribution of a species! But how?

The difference among populations is SO recent, they suspect that this is likely the result of HUMAN-mediated transport.

The authors consider that just a SINGLE sponge can contain up to 3000 individuals!

(from the very fine Tide Chaser blog)

Just a SINGLE sponge containing larvae and/or a few adults could have "colonized" the Western Atlantic!! Both of the Atlantic populations could conceivably have been seeded from Indo-Pacific ancestry as recently as the early 19th Century!

They speculate that the ENTIRE presence of this species in the Atlantic could be artificial!!

The authors add further caution to the paper's conclusions that with the ready transportation from ballast water, larvae from outside regions are readily transported to foreign waters, resulting in unforseen ecological impacts.

(from Friday Harbor Labs!-note that it is NOT Ophiactis savignyi!)

I would further add that I have often frequently observed this species in the rubble of aquarium tanks. Its a species you see in many tanks with tropical inhabitants-both Atlantic and Pacific. Ophiactis is small and comes in with the "living rock" and gravel pretty easily..
Here, we discover what was thought to be a natural, widely distributed species-turns out to be the likely possible result of a human-influenced "marine invasion" from a foreign species. Sort of the echinoderm version of the rat or the cockroach.

Ophiuroids GET everywhere. Who knows how successful and out of hand they'll get??