Isopods Cause Reproductive Death in Shrimp

Isopods, you know them as those adorable little roly-poly bugs under rocks in the forest or the gigantic Bathynomus of the deep sea. They are also those cute and cuddly parasites in the gill chamber of shrimp too! Awww, How special! In the recent issue of JMBA-UK, Calado et al. describe how these fuzzy wittle darlings castrate their shrimpity hosts.

The isopod in question is the Argeiopsis inhacae, a member of the parasitic family of isopods - Bopyridae. They don't start off as the lovely parasite "friend" of shrimp. The larvae begins life as a free swimmer until it finds a copepod to attach itself too, then metamorphoses into another larval stage and looks to buddy up with the nearest shrimp it can find.

Calado et al. found that when pairing unparasitized males and females together, females laid perfectly fine clutches of eggs. However, when unparasitized males were paired with females containing the isopod, there were never any egg clutches laid. This is in spite of similar courtship behavior and no differences in moult patterns. Furthermore, parasitized adult female shrimp did not develop a key feature denoting fertile production, a bright green spot on the back that marks the presence of large yolky oocytes. It appears that this bopyrid isopod causes "reproductive death" in females Stenopus hisidus. Unfortunately, they never tested whether parasitized males can make viable offspring. It is still not known whether parasitism is sex-biased or appears as such because of the author's limited sampling.

This short study is interesting because it is the first experimental study to nail down reproductive cessation due to the isopod parasite. What use is it to stop reproduction? One reason may be to divert the host's resources away from reproduction, an energy expensive process. The isopod would ensure its survival and its continuance to leech off the shrimp.

The isopod, Argeiopsis inhacae, forces the shrimp's carapace to bulge, as it grows inside the branchial chamber. Figure 2 from Calado et al. (2008).

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Calado, R., Bartilotti, C., Goy, J.W., Dinis, M.T. (2008). Parasitic castration of the stenopodid shrimp Stenopus hispidus (Decapoda: Stenopodidae) induced by the bopyrid isopod Argeiopsis inhacae (Isopoda: Bopyridae). Journal of the Marine Biological Association of the UK, 88(02) DOI: 10.1017/S0025315408000684

Words of Wisdom from a Clownfish

h/t to S.A.L.-P.

Return of the Spineless Song - Symbiosis Is Everywhere

"Symbiosis is ubiquitous in terrestrial, freshwater and marine communities. It has played a key role in the emergence of major life forms on Earth and in the generation of biological diversity."
- Nancy Moran (2006). Symbiosis. Current Biology 16 (20): R866-R871

Yes my friends, its true. Everywhere. You can't avoid. You are in a symbiosis. You might as well accept it. You have several phyla of eukaryotes on you as we speak. Some are cleaning up dead skin, some are burrowing under your skin. Lets not even talk bacteria and viruses. Everyone does it whether they want it not.

When symbiosis comes to mind, what do you think of first? My guess is that the majority of you thought about mutualism, two or more organisms helping each out, positive-positive relationships. But symbiosis spans the gamut from parasitism to mutualism. Symbiosis is the relationship between 2 (or more) organisms - "Living together". It is a fascinating subject of study. I have been studying chemoautotrophic fauna with with endosymbiotic bacteria for several years now. Thats "chemical self-feeding" critters with "internal" bacteria living inside of it. I never ceased to be amazed at the diversity of interactions. These bacteria can utilize a variety of chemicals, hydrogen sulfide and its derivatives, methane and other gases, iron (and other polymetallic) sulfides, oil, who knows what else we might find as we look closer and delve deeper. To most animals, these chemicals are harmful, if not lethal, at certain concentrations.

My work in the Fisher Lab has made me appreciate symbiosis much more deeply than I would have thought. In this song I sing my praise of symbiosis, in the sense of mutualism (required reading: Ruby E, Henderson B, McFall-Ngai MJ. 2004. We get by with a little help from our (little) friends. Science 303:1305-1307). You can find a link to song in the Spineless Songs Sidebar on your left

Symbiosis is Everywhere

You can in through my skin
Just like infection
But now I can’t live without you

I could never ask you to leave
I need you to feed
We’ve evolved so much to together

When I was but a larva
So young and unsure
You came into my life and showed me the way

We could never be apart
I’ve a place for you
In a specialized organ, maybe two

Cows do it, termites too
corals tubeworms squid who knew?
Symbiosis is everywhere (x4)

I give you a home
you give me some food
Together we can make it in this ocean blue

With our pathways linked
Short chain fatty acids
Is what I want is what I gets

I may bring you sunlight
Methane gas or sulfide
For you I will make exposure so high

You don’t grow too much
Man, don’t parasitize
Theres no prize for oversized

Mussels do it, clams do too
Nematodes, anemone even kangaroo
Symbiosis is everywhere (x4)

Fate of Carbon Derived From Different Origins in Zooxanthellate Anemones

An intriguing new study by Bachar et al., published in the latest Journal of Experimental Marine Biology and Ecology (JEMBE) shows that carbon derived from different metabolic pathways is used differently by anemones with algal symbionts. It has been well-known for a long time that some anemones, such as the Aiptasia sp. used in their study, form a symbiotic relationship with zooxanthellae (called autotrophy). For a while it was assumed that the anemones persisted by mostly utilizing carbon translocated from its symbionts, but they can also supplement this by heterotrophic feeding on plankton. Bachar and colleagues studied the fate of carbon derived from autotrophy versus the fate of carbon derived from heterotrophy using radiolabeled carbon sources.

To trace the fate of autotrophic carbon the standard is to radiolabel carbon dioxide (14C via sodium carbonate) since this is the carbon substrate of photosynthesis. To trace the fate of heterotrophic carbon they grew brine shrimp (Artemia sp.) fed on algae incubated with the same radiolabeled carbon dioxide source. This what is called a pulse-chase experiment in symbiosis lingo. The idea is that you pulse the anemone with labeled seawater for a certain amount of time, for instance 12 hours in the light and 12 in dark in this study. Then, there is a chase period where you take the anemone out of its radiolabeled environment and let it "digest" the carbon. It is during this time that the products of photosynthesis are making its way from the zooxanthellae into the tissues of the anemone. Then you make an anemone slushy, basically using something resembling a modified coffee bean grinder. Centrifuge the sample, all the algae fall to the bottom while the animal cells lyse into the supernatant. Add a dash of acid to drive out unassimilated inorganic carbon and Voila! You have yourself a delicious Anemone Slushy, a tasty family treat.

What Bachar et al. did was to trace the fate of carbon in the lipid portion of the Anemone Slushy as well as the whole tissue (i.e. animal) portion of the slushy. What they found was very interesting.

"The radioactivity levels of both the lipids and the total tissue of the sea anemones that were fed labelled autotrophic or heterotrophic carbon show that for the autotrophic anemones, the fastest change occurred in the lipid tissue, while for the heterotrophic anemones, it took place in the entire tissue."-Bachar et al. 2007 (see Fig. 2 from their paper below)

This is the first I have seen (and they make that claim in their abstract) that differentiates between the fate of autotrophically and heterotrophically derived carbon in a mixotrophic organism. It suggests that autotrophically derived carbon is convert mostly to lipids, potentially as quick and dirty carbon source for metabolism and respiration, while heterotrophically derived carbon is dispersed throughout the body, possibly for structural purposes (i.e. cell membranes, growth). Autotrophic carbon, derived from carbon dioxide, is short chain molecule so it makes sense that this would be used as an immediate energetic source since it can be easily converted into molecules like pyruvate and acetate which can slide right into the the metabolic cycles. On other hand, heterotrophic carbon is typically longer chain, like fatty acids and sugars, which need to be broken down into smaller parts to be used for metabolism. Hence these might be more appropriate carbon sources for structural components which are typically longer-chain carbon compounds like collagen and phospholipids.

Though this a short study reporting their novel results I am sure they have much greater ambitions in the works so it is worth keeping an eye out for future work from this lab. Symbiosis is fascinating topic. Though scientists have known about algal-cnidarian symbioses for a long time, it has taken decades of work to just figure out what and how. Now Bachar et al. give us where and some further insight in some more how. It is still unclear "why" though and the "how" in an evolutionary sense. Symbiosis is a field still much ripe for exploration. All the studies ever done on host-symbiont phylogenies, carbon translocation, physiological ecology, etc. is just the tip of the iceberg. Autotrophic symbioses are everywhere and occur in many animal phyla from cnidarians to nematodes to molluscs. Some ugly hairy creatures with backbones (a lame evolutionary feature is ask me) of the overexaggerated 5% even form symbiotic relationships with autotrophic organisms!

Acropora palmata Spawn Collection

Nick Polato, a fellow grad student down the hall from me, is blogging Summer Spawn '07. He is a graduate student in the lab of new faculty member Iliana Baums here at Penn State. They form the second contingent of Penn State Marine Biology (which exists only in our minds). Our motto? "Come study the ocean far away from it!" Having an office overlooking a beach is overrated and an unnecessary distraction to scientific progress (damn you Scripps!! No, I'm not bitter...really...). They are out in Florida Keys (bastards!) waiting for the coral to spawn. They are studying the federally-listed endangered coral species, Acropora palmata with the goal

"...to enhance efforts to protect and expand populations of this species by promoting a better understanding of their reproduction and helping to establish new colonies for reseeding reefs."-Summer Spawn '07

So head over there for (hopefully) daily updates of their research during their field season. In addition to the underwater photos they take (like the one above), you can read some nice natural history

"There was a sense of anticipation as darkness fell and we were surrounded by glowworms spawning in the water all around us."-Summer Spawn '07

The Spoils of the Field Season

Nothing makes me more happier than collecting specimens. I feel as if I am transported back to the Victorian era and am on a grand expedition to uncover the mysteries of the deep and testing for the first time the Azoic Theory of the ocean.

Except that my expedition only lasts for 4 weeks, not 4 years, and my purpose is not prove life exists in great depths at great extremes but to study the life we expect to find at these places. One such place is the East-Lau Spreading Center between Fiji and The Kingdom of Tonga. Here I am studying, as part of my graduate work, the ecology of communities structured by three habitat-forming molluscs, the mussel Bathymodiolus brevior and the snails Alviniconcha hessleri and Ifremeria nautilei. These 3 species are large chemoautotrophic species and serve as the foundation for an intricate network of associated fauna living within the aggregations of each mollusc. I am also describing, with other colleagues, species of anemone, zoanthid and shrimp from there (6, 1, 1 species, respectively).

The picture above shows my haul from the 2006 (sept.) field season. My last field, it is time for me to write it up, turn it in and move on. I don't know how many specimens I've collected in total. But from all the quantitative collections I've made in 2005 and 2006 I have found ~55 species associated with the 3 habitat-forming communities and have counted over 50,000 individuals of this associated fauna so far weighing in at over 1,948 grams. There are still a few taxonomic details I am working out with a Polynoid Polychaete genus, so I'll let you know the final word after that is sorted out along with the counts of the habitat-forming fauna.

As a final caveat, yes all the organisms I have identified are INVERTS! Surprised? I didn't think so... We did collect some zoarcid fish that I will analyze the gut contents of, but none were caught in my quantitative collections.

Layers of Symbiosis - Visualizing the Termite Hindgut Microbial Community

This video from Dr. Jared Leadbetter at Cal Tech, courtesy of the Journal of Visualized Experiments, described in fantastic detail the layers of symbiosis in termite hindguts. Well worth the view, watch as Jared dissects a termite hindgut then views the live bacterial and protozoal community. The quality of imagery is fantastic and Jared's enthusiastic narration is informative and captivating. Head over to the Journal of Visualized Experiments for many more visual wonders! This is how science is supposed to work in my opinion. The free transfer of knowledge from one individual to another. NO password barricades, journal subscription hinderance, just open access to the tremendous wealth of information accumulated by civilization.