Starfish Macro Shots! Up Close Tropical Edition!

This fantastic image by Tyson Jerry from North Sulawesi

By now, a bunch of people have seen the incredible collection of close-up asteroid photos by Alexander Semenov and I reviewed them for the Smithsonian here.

Those pictures were close ups of asteroids from cold-water settings in the North Pacific & North Atlantic. There's a very different fauna of asteroids in those parts of the world compared to the tropics.

Most of the starfish in the tropical Indian and Pacific Oceans show a lot of granules, spination and armor and of course are composed of very different families of asteroids compared to those which live in the far North.

If you'd like to see some pics of the mouth armor in these types of starfish go here!

I start with the above : a STUNNING shot of Protoreaster nodosus, a commonly encountered sea star found throughout the Pacific.  Shots below are macro shots showing skeletal features and colors of different tropical, Indo-Pacific starfish species.

More close up on Protoreaster with more pointed spines. Image by Nick Robertson Brown (Frogfish Photos)

What are these weird threads? Feeding tentacles from a benthic ctenophore? Gametes?  Weird. Photo by MerMate (Eunice Khoo)

The strange soft-warty structures are a distinguishing feature on the surface of Echinaster callosus! Function unknown. Images by Optical Allusion

Some fantastic detail on the ophidiasterid Nardoa. Image by Stephane Bailliez

Here's a close up on Gomophia gomophia. Image by Okinawa Nature Photography (Shawn Miller)

An awesome close up of the disk on Fromia nodosa from the Maldives. Image by Philippe Guillaume.

Close up of Fromia indica. Image by Jesse Claggett

The papulae (aka the gills) and spines of Acanthaster planci-the Crown of Thorns starfish. Image by Barry Fackler.

This one shows a close up of the gills of Acanthaster planci. Image by David Garcia Fonseca.

Wow! First record of the brittle star Ophiactis? living on the spines of Pentaceraster. Image by Maractwin

another tight shot of a brittle star (Ophiothela?) living on the asteroid Nardoa. Image by deco4macro

The same kind of star sans ophiuroid. Image by samui13coconut13

Surface spines on Pentaceraster. The tiny white circles on the brown spaces are papulae aka the gills. Image by Friscodive.

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Surface close up on the cushion star Culcita novaeguineae from the Maldives. Image by Frédérique Jaffeux. All the white pores are papulae aka the gills.

From the Sand star Luidia maculata Image by Kok Sheng

And another L. maculata by [WJ]

Biophysics Meets Old School Taxonomy! Ochre Star Pisaster ochraceus can adapt body shape to wave action!

Image by RJadams55

One of the things I love about biology is when you have an animal which has been studied down to the wire and become so familiar that people take it for granted, and then you discover something completely new about it!!!

And that in turn gives you insight into past events and other things around you. Cryptic? Yes..but I will explain.

This week's post is from Kurtis Hayne and A. Richard Palmer, University of Alberta in Edmonton
who have written a swell, new paper in the Journal of Experimental Biology 216: 1717-1725 (here)
(my thanks to Kurtis for an offprint of the paper).

It studies the reaction of the classic workhorse starfish Pisaster ochraceus as it reacts to one of the harshest of environmental stresses:  the ocean itself! WAVES!!      SPLOOSH!

Image by Lance and Erin Willett

Details....
Hayne and Palmer collected numerous individuals in and around Barkley Sound near the Bamfield Marine Sciences Center on Vancouver Island.  Individuals were collected and measured to assess values for drag and lift. Some were tagged and returned to the field for various field transplant experiments (look below).

Specimens were also surveyed in the field and correlated with the power of various wave forces.

Their findings!

1.  Sea stars in wave-exposed sites had narrower arms and were lighter per unit arm length than those from sheltered sites. On average, animals from the most exposed sites were 12% narrower at the base compared to the most sheltered!

2. Body form was tightly correlated with the maximum velocity of breaking waves across four different localities and over time.

3. Sea stars were transplanted between sheltered sites to more wave-exposed sites revealing that they became LIGHTER per unit arm length, developing narrower arms after 3 months! There was a tight correlation between water flow and the body shape which strongly supported the idea that wave force was affecting the body shape.

This figure 7 very nicely summarizes their findings. The animal on your left ("A") is an example of an animal from "most sheltered" going right to the one on the lower right from "most wave exposed".

 and the small box "D" even shows the extent that the abactinal spine/granules show density and a heavier degree of calcification between a sheltered (orange on the left) vs. an exposed (purple on the right) individual.  

The exposed form below is overall smaller in size, weigh less, and with a higher aspect ratio (arms narrower, etc.) and with a more dense skeleton.   
Dynamics 
1. This is thought to aid the individuals in a wave-exposed environment from being washed away. Not as much lift and not as much drag.
2. The heavier granules offer more protection against the crashing forces of the waves.
3. BUT, having a higher aspect ratio comes with some costs:
          a. such as being more prone to overheating. Sheltered are much more effective at resisting
              overheating and water loss. Although heating may be offset by cooling temperatures from
               waves and such..
          b. having smaller areas available for gonads. This results in lower overall production of
               reproductive material and so on..

Image by jkenning


Image by Shannon Robalino

The protected body form
These make more sense in protected areas away from the harsh, crashing wave-swept regions:
Some dynamics...

1. Larger animals are more likely to be caught and washed out to shore. (greater drag and lift at play)
2. BUT the larger, thicker size involves more water retention and thus better thermoregulation and better cooling.
3. Greater volume for gonads! More potential offspring!

from Scenic Beach State Park in Washington

From Samantha Russell


Bear in mind-that in order to test these interpretations, animals were actually transplanted between protected vs. wave-swept areas. Transplanted animals (from protected to the exposed wave-swept areas) decreased in mass and increased in aspect ratio over time. 

Environemntal factors directly affected the body shape of ochre stars!

Biophysics Meets old fashioned Taxonomy!

Probably the neatest footnote to all of this was that these differences in different forms of Pisaster was observed by several naturalists in California, early in the 20th Century.

The great Stanford starfish biologist and Director of the Hopkins Marine lab, Walter K. Fisher identified several "forma" or distinct morphological variants of Pisaster ochraceus in his giant 3 volume monograph documenting and describing the asteroids of the Pacific Northwest from 1930.(sadly the Asteriidae is not in the volume linked).

Fisher even observed that the differences in three of these forma seemed to be based on the degree of calcified skeleton, i.e., how built up the spines were...

It is difficult to escape the inference that the characteristic small spinelets of the abactinal area are correlated with queit water, but that this is ot the only factor is evidenced by the presence, along with confertus, of forma ochraceus and nodiferus, the latter found on open coasts and also in deep water (Monterey Bay).

The variant nodiferus is Hayne and Palmer's "exposed coast" morphological form. Fisher's comments about the inconsistency of abactinal spinelet shape/size suggest there remains even more variation and other factors to consider in future studies..

Sometimes, these "forma" turn out to be distinct taxa-perhaps subspecies or species. But sometimes its just some variation in body form in reaction to the environment.

Just as if we took a flabby, couch potato from his comfy TV room with silk bedsheets and put that person into an underground mine to dig minerals for a living. We would perhaps see changes in musculature, bone structure, and maybe even hair/eye color.

So there you have it! A cool convergence between a modern biophysics story with a fun footnote from classical taxonomy/natural history!
Are these considerations we might apply to other intertidal asteroids in similar settings? (Stichaster australis from New Zealand). Image by Jon Mollivan


Want to know more about the Ochre Star: Pisaster ochraceus?
 Here's my post about Pisaster ochraceus ecology and role in climate change. 

and what explains all the color variation in Ochre Stars?? (here)

Want to see a sea urchin that lives in a high-energy wave swept environment? See Colobocentrotus! The Shingle Urchin.

Flatworm Color Explosion! Off topic! A Panoply of Playhelminths!

Today, here in Washington DC, we have an overcast day with a rather dreary storm raining down on us..and a quick skim through the news is filled with all kinds of blah and bad news, Sequester is the buzz of the town.. so..meh.  What to do??

FLATWORM COLOR EXPLOSION!!!!!
A striking yellow/greenish Pseudoceros dimidiatus from Osprey Reef,Coral Sea.

Photo by Richard Ling

A brief zoology lesson: Flatworms are members of the phylum Platyhelminthes. This is the group of worms which includes many parasitic forms, such as the tape worms and trematodes as well as several free-living species that live on land, in freshwater and in the ocean.

If you remember those funny arrow-headed ones that you could cut and via regeneration give it two or more heads? That was a flatworm!  Many, many species are found throughout the world.

Free living flatworms are mostly predatory-feeding on immovable animals, such as tunicates to other smaller animals and worms. There's a LOT of different species with many interesting biological stories! Some (go here) are mimics with nudibranchs! 

But most folks don't realize just how colorful and gorgeous they are in the tropics!  Here is a bunch....

Pseudoceros bifurcus from Kenya.

Photo by Jim Anderson

Another of the same species (P. bifurucs) from Singapore apparently feeding on some tunicates.

Photo by Wild Singapore

Pseudoceros laingensis from Straits of Johore

Photo by Arthur Anker

Sorry, this one didn't have a name.. Amazing to look at though... From French Polynesia.

Photo by Pauline Bosserelle

Another flatworm I don't have a name for.. but apparently from the Philippines

Photo by "Jason" aka Jasdivr

Another one without a name.. This one from Oahu, Hawaii!

Photo by Bill Stohler

Possibly Cycloporus sp. on its tunicate host/food (Didemnum molle) fr. Wori Bay, Sulawasi

Photo by Christian Loader

Pseudoceros susanae?  A beauty from the Maldives!

Photo by Chris Dow

Another stunning Pseudoceros susanae? from the Maldives

Photo by Philippe Guillaume

Purple flatworm! From Bali.

Photo by Ben Naden

Pseudobiceros bedfordi, the so-called "Persian carpet flatworm." This one from Dayang, Malaysia

Photo by Dyana Wu

A neat one with a different texture! A "papillose flatworm"  Thysanozoon/Acanthozoon? From Madang, Papua New Guinea.

Photo by Arthur Anker

Thysanozoon sp. from Panama.

Another gorgeous pic by Arthur Anker

Acanthozoon sp. from the Philippines

Photo by Eunice Khoo

and that's just the marine ones!  the land ones get even better! but I'll save those for another day....

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??