Worms & Snails that Live On/In Sea Cucumbers!

There's something about sea cucumbers which seems to make them attractive as hosts for various other animals.
Some sea cucumbers got clams that live in their throat...
The sea cucumber anal region seems to be popular as a place to live as crabs and of course, pearlfish find good homes there..

This week.. More animals that have made sea cucumbers hosts to their lives!!

Worms!
This scale worm above was identified as Gastrolepidia clavigera, living on its host sea cucumber (apparently Bohadschia graeffei). Image by Arne Kuilman.

This one by Theresa Legler, shows another polynoid worm, but it looks like a different genus/species...

Another similar looking polynoid. Image by Kevin Lee.

This one, by Ben Naden,  seems to be taking advantage of the rough skin texture...


Snails! Most of the snails shown here appear to be members of the Eulimidae, which are a diverse group of snails, which has apparently adapted a parasitic lifestyle. Many of them live on echinoderms. I review some of them here.  

Eulimids basically feed on their hosts. They have a proboscis which is inserted into the bodywall and used to suck out precious bodily fluids and other nutrients!

Here's a neat pic by Eunice Khoo showing several embedded in the epidermis.


A different kind of snail, Melanella sp. living on the sea cucumber Thelenota ananais.


Images below by "wj", what looks to be another set of eulimid snails, feeding on the sea cucumber Colochirus.



and let us not forget that eulimid snails (in this case-the genus Stilapex) ALSO inhabit deep-sea sea cucumbers... (from the sea pig post)

(from the New Zealand R/V Tangaroa weekly log, photo cred-Stefano Schiaparelli, NZ IPY-CAML) 

What makes Sea Cucumbers such desirable housing?  While there's no immediately clear data on the topic, it seems to be important that sea cucumbers are all composed of a soft, edible yet durable, tissue. So, maybe a good house that these protects and feeds?

Flukes in Cukes! Flatworm Commensals in Sea Cucumbers, Sea Urchins and Starfish!

Fantastic image by Chelsea L. Wood

Today we look at some neat examples of flatworms that live in echinoderms!

And to the flatworm and parasitic worm people reading this? YES, I know flukes aren't free-living flatworms. It rhymed! So go with it for now. thanks for your patience!

Flatworms aka the Platyhelminths (in Greek-literally the "flat worms") look like living carpets. They are mostly predatory, but may also feed on small organic particles and live all over the place. They can be parasites, such as tapeworms or free-living beasts such as the one featured in the collage below.

These include the familiar Dugesia-that you find in high school biology (brown with arrow shaped head and two weird eyes) to these big, colorful species that live throughout the tropical Atlantic and Pacific. There are some 4500 recognized species of free-living flatworms..

An awesome collage by Arthur Anker!

Papers that were used today:  this paper by George Shinn (1981)-Hydrobiologia 84: 155-162
another in Biological Bulletin 169: 182-198 (also by Shinn) and this one, from Canadian J. of Zoology 61(4): 750-760 which describes the species living in the sea cucumber

What's interesting about the ones that I'll be talking about is that none of these is exclusively parasitic (such as a tapeworm or a trematode). These are free-living species..but they live INSIDE the body cavities of echinoderms!  

Think of it as if you ended up living in the intestine or the body cavity of a whale. Lots of space there and potentially...a  lot of food. Plus protection from predators, the elements and a safe place to reproduce!

So, technically they aren't really parasites (where the host 'loses') they are commensals that are considered just kind of benign.

Image from WallaWalla University Inverts site! 

It makes sense. Sometimes, an animal with a huge internal body cavity can be a home. We've seen the classic pearlfish and even when clams that live inside the throats of sea cucumbers.

It turns out that there's something in the neighborhood of SEVENTY species of different free-living flatworms that live in echinoderms as hosts! A nice list of these can be found in this paper here.

Most of these hosts appear to be sea cucumbers with sea urchins and sea stars. Some in cold water but also in the tropics!  Crinoids and brittle stars seem to be among the minority as hosts for flatworms..probably because there's not much "living space" inside their body cavity. Or maybe they're just not as well studied?

Here are two well-documented worms from the North Pacific coast.. one that lives in several Pacific urchins and one in a North Pacific sea cucumber...

The Urchin as a "House" for flatworms! 
Urchins on the west coast of North America (in the Pacific Northwest) include the well-known purple sea urchin (Strongylocentrotus purpuratus)

Image by Joe McKenna

And the giant red urchin (Strongylocentrotus franciscanus)

Image by Dan Hershman

and the deep-sea Allocentrotus fragilis

Image by NOAA Photo Library

and even the southern California urchin Lytechinus anamesus

ALL of these are often inhabited by this beast! Syndisyrinx franciscanus

Image by Chelsea L. Wood

Syndisyrinx franciscanus lives in the digestive tract of its host and apparently, infested urchins have been found with up to 186 worms!!! (an average of about 29/individual)

Image by Chelsea L. Wood

This one is called Syndesmis dendrastrorum 

From the EOL page for S. dendrastrorum

and it lives in the common Pacific Northwest sand dollar Dendraster excentricus!! (seen below alive with spines)

Image by Patrick Warren

or perhaps more familiar if seen like this? Spines removed...

Image by Cheryl Moorehead

Even the familiar Pacific Sand Dollars can HAVE WORMS!!!  Ya' learn something new every day!

What do they do in there? Mostly, these live in the intestine feeding on the host's intestinal lining (the tissue) AND apparently also like to eat on the symbiotic protists (the ciliates) that ALSO live in the intestine of the host.  But this apparently doesn't create any detrimental effects on the host. So-commensal rather than parasitic.

Apparently, the worms produce egg capsules are released into the intestine of the host and released outside with the feces.  When the capsules are eaten by a new host, they become active.... probably a reaction to the intestinal fluid and proceed to live out their new life in the new host's intestine.

Flukes in Cukes! 
A free-living worm lives in the Pacific NW sea cucumber Parastichopus californicus.

Image by T. Van Nunnery

This beast is called Anoplodium hymanae, a worm that is named for the famous Invertebrate Zoologist Libbie Hyman

Image by Chelsea L. Wood

These are a little more aggressive than the ones that live in sea urchins.

This species reaches the body cavity by penetrating the wall of the intestine..usually through the respiratory trees (feathery structures colored in blue in the pic).  I've briefly mentioned this area as where some sea cucumbers can feed via their butt!



The eggs are spread out via the anus with the feces until they are devoured by a host.

Similar to the ones in urchins, the larvae hatch in response to digestive fluids in the intestine of the host. Get into the intestine, move to the respiratory trees and then further move out into the body cavity of their new host!

Image by Chelsea L. Wood

Starfish got worms too!
So, there aren't a lot of records of flatworms that live in/among sea stars. Six were recorded in asteroids..and oddly enough, the one below was not included. So maybe its something new?

Description of this pic indicated the cold-temperate North Atlantic asteriid species Leptasterias littoralis. Is this a commensal flatworm moving within the tube foot groove? Moving around on the surface?  Something new? A convergence of two species by chance?

Image by Nick Sleptov

For more worm-starfish relations?

Go to this pic of Echinaster callosus and look closely at the short, striped things crawling on the swellings!    this one has a tighter shot that shows them a little more easily..note the brown squares with the white stripes.. (and includes a shrimp to boot!) WOO!  Acoel flatworms? 

How many remain to be discovered?? 

Hawaiian Brisingid Starfish Munitions Mysteries!

Image courtesy of Chris Kelley, Hawaiian Undersea Research Labs

November has been a busy month! While I was hard at work in Paris other projects were underway! I often wish that I could be in two places at once because it happens that different and exciting things happen at once!

Case in point-I have discussed how I have worked with the University of Hawaii and the Hawaiian Undersea Research Laboratory before. (go here to see)

From the HUMMA Project website

Specifically, I have been working with Dr. Margo Edwards in conjunction with the Hawai'i Undersea Military Munitions Assessment Project (or HUMMA) which is a coalition of institutions including the University of Hawai'i, NOAA, the US Army and others. 

To put it briefly, there's a lot of unexploded bombs and munitions about 5 miles off the coast of the island of Oahu (and other locations throughout the Hawaiian Islands).

The HUMMA project is part of an ongoing effort to map, survey and reconcile these weapons. A Frequently Asked Questions (FAQ) about this can be found here.

A nice video about this project is here:


And in fact the HUMMA Project has a Youtube Channel with a bunch of interesting things documenting their work here

So how does a humble starfish scientist like me get involved with all of this seemingly unrelated (but interesting) work?

Brisingid starfishes!

What are brisingids? Short answer: Sea Stars/Starfish that put their arms up into the water to capture food using a special kind of "starfish velcro".  Go here to see a full write up about these weird deep-sea starfish!

In November the Hawaiian Undersea Research Lab (HURL) and the HUMMA Project took to the water with the submersible Pisces V (one of the only manned research submersibles still operating in the US!)

From the Friends of HURL Facebook page

From the Friends of HURL Facebook page!

One of their objectives during this November dive was to look at the various animal biota in and around the ordnance (go here for a HUMMA Project update) such as these sea anemones living on a vertically oriented mine...

From the HUMMA Project website

Probably one of the most abundant and interesting of the animals living in and around the ordnance and other structures were brisingid asteroids. So, there was an interest in finding out more about them.

Especially since they seemed to have large round "lesions" or swellings on the arms (note the large one on the upper center arm)..

Image courtesy of Chris Kelley, Hawaiian Undersea Research Labs

Unfortunately, there's only so much you can do with brisingids from video and pictures taken at a distance.  So many questions!

What species were these brisingids?  

How many different kinds of brisingids were present? 

What were the swellings?  Why were there so many of them? 

And so, collections were made using the Pisces V submersible's collector arm..

Being able to look over the specimens at long last gave us two valuable discoveries!

1. Possibly a new species?  The brisingids we were studying belonged to a genus that had never been seen in Hawaii before! And a species that could not be reconciled with any of the known ones!  Further work remains to be done-but it seems like there is good reason to believe at least some of the brisingids studied belong to an undiscovered species!

2. What were the swellings? An examination of the swellings revealed an even more interesting discovery!!   They were parasitic barnacles!!

There are some VERY unusual types of barnacles called Ascothoracidans that can enter into the body cavity of sea stars (and other echinoderms), affix themselves to the internal body structures.

Some relatives of ascothoracidans, called rhizocephalans have highly unusual relationships and can take over a host's reproductive system! (go here to see on case)  It is unclear what the parasites in these brisingids do however.

The Time Lapse Project!

Brisingids were the subject of a neat project undertaken by 3 intrepid students from Honolulu's famous Iolani High School: Kyle, Erin and Logan (shown here with model of their study organism)

Their efforts were largely directed at some ecology and behavior of these starfish, about which VERY little is known.  Often times, we can barely identify brisingids much less describe how they live in their natural habitat!

They participated and won awards at the 2012 International Science and Engineering Fair! Woo! Here was a pin of their crest!

One part of the student's work involved engineering and developing their very own time-lapse camera for use in observing brisingid sea stars!!

Here is a video from their early efforts in shallow water   
and extended to night time....

And finally, here is the final product observing deep-sea brisingid starfish and some deep-sea sea anemones!  Note how the brisingids move.. 
The full scientific impact and write up of all these discoveries is currently underway.

But I find it a hearty endorsement of these kids' abilities that they were able to develop such a clever and useful device given their constraints!  This was something they did in high school! I look forward to their efforts in college!

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... :-)