An Attempt to Generate Benthic Biofilm for Substrate Feeders

[livinlifeinBKK]

With the spot feeding, the easiest way I can think to test this would be with multiple identical aquarium setups and multiple stars of the same size and species (preferably collected from the same area at the same time). Have a control with no supplemental feeding, and the test group with supplemental feedings. If the difference in lifespan ends up being statistically significant (even by just a month or two), the feedings make a difference, if not, they don't. Unfortunately, such a study would be pretty expensive and time consuming, and there may be some ethical issues involved too due to the risk to the stars. Plus, if the lifespan was not drastically increased or decreased, it wouldn't necessarily help explain why the feedings would make a difference.

Some other kind of interruption to the microbiome/chemical defenses of the star is possible, I'm just not sure what that interruption would be.

I'm sure a balance can be worked out (though the amount of effort necessary to figure out that balance could potentially be enormous), but I don't know if it would be able to provide enough food for a star without some severe hands-on intervention (something like rotational grazing for sheep and cattle). Additionally, I don't know if it would be plausible for a mixed species tank in smaller sizes - in other words, the setup may need to be a species specific tank to accommodate the star's diet. This would be an interesting one to find out for certain on in the future though. Something that has been coming up on the forum lately that might be of interest/use to you for providing more oxygen to the tank is the Venturi Injector concept. Supposedly (I need to do some research on this, but this is what has been stated in the threads), venturi injectors can add more oxygen (or really just more atmospheric air) to the tank than normal methods (water movement via pumps, skimmers, air stones, etc.). I can't vouch for the accuracy of that state at this point, but it might be worth looking into.

Sounds like an interesting piece of equipment to look into...and as for growing the biofilm, I'm thinking that since I don't have a way of measuring oxygen concentration of my aquarium right now it's probably safest to just grow the biofilm in a second tank and transfer a glass paper filter or rock to the stars aquarium and feed him by placing him on it for now along with spot feeding other foods every so often...I've had him about six months now which seems to be around the time these guys go downhill...btw, as for the African Biscuits I wonder if people generally have much more success with them or if things usually go the same way after a little while. That one guy is the only person I've heard from who's kept one so idk

 

[Dan_P]

With the spot feeding, the easiest way I can think to test this would be with multiple identical aquarium setups and multiple stars of the same size and species (preferably collected from the same area at the same time). Have a control with no supplemental feeding, and the test group with supplemental feedings. If the difference in lifespan ends up being statistically significant (even by just a month or two), the feedings make a difference, if not, they don't. Unfortunately, such a study would be pretty expensive and time consuming, and there may be some ethical issues involved too due to the risk to the stars. Plus, if the lifespan was not drastically increased or decreased, it wouldn't necessarily help explain why the feedings would make a difference.

Some other kind of interruption to the microbiome/chemical defenses of the star is possible, I'm just not sure what that interruption would be.

I'm sure a balance can be worked out (though the amount of effort necessary to figure out that balance could potentially be enormous), but I don't know if it would be able to provide enough food for a star without some severe hands-on intervention (something like rotational grazing for sheep and cattle). Additionally, I don't know if it would be plausible for a mixed species tank in smaller sizes - in other words, the setup may need to be a species specific tank to accommodate the star's diet. This would be an interesting one to find out for certain on in the future though. Something that has been coming up on the forum lately that might be of interest/use to you for providing more oxygen to the tank is the Venturi Injector concept. Supposedly (I need to do some research on this, but this is what has been stated in the threads), venturi injectors can add more oxygen (or really just more atmospheric air) to the tank than normal methods (water movement via pumps, skimmers, air stones, etc.). I can't vouch for the accuracy of that state at this point, but it might be worth looking into.

If I was studying sea stars, I would try tracking sea star weight to track growth.Body measurements might too variable to be reliable. I would also run a pilot study on growth measurements with sand sifting stars. I might also pilot a nutrition study with sand sifters.

 

[livinlifeinBKK]

If I was studying sea stars, I would try tracking sea star weight to track growth.Body measurements might too variable to be reliable. I would also run a pilot study on growth measurements with sand sifting stars. I might also pilot a nutrition study with sand sifters.

How would you track weight while keeping them underwater? Also it gets increasingly expensive and resource consuming to set up multiple tanks for the stars to test different feeding techniques. How would you design the nutrition study you mentioned?

 

[ISpeakForTheSeas]

If I was studying sea stars, I would try tracking sea star weight to track growth.Body measurements might too variable to be reliable. I would also run a pilot study on growth measurements with sand sifting stars. I might also pilot a nutrition study with sand sifters.

I actually have heard of a study doing weight and length measurements (see the link below) for sea stars, but they weren't testing particular different diets. They were caring for juvenile, post-metamorphosis Linckia laevigata (the survival rate was abysmal, but some did survive) and feeding them "epibenthic microorganisms encrusting dead coral skeletons (Acropora)."

https://core.ac.uk/download/pdf/5093827.pdf

Sand sifters are a good star to try feeding, as they (by all scientific/educational accounts that I’ve seen) should eat bivalves and gastropods rather than biofilms in the wild (in fact, because they swallow their prey rather than digesting them externally, some studies have been done on the stomach contents of a few similar species, so we’d have a relatively good idea where to start with the feeding). So, they should be relatively easy to feed. It would be expensive to test on a large scale, but a small pilot study should be able to show pretty cheaply (aside from the fact that you’d likely have to have certain snail species hand-collected, because they’re not readily available on the market) if that info is accurate. Figuring out proper nutrition with them might be a bit harder/more expensive, but it could probably be done. The results of such a study could potentially support or undermine my hypothesis, so I’d be curious to learn what the results are. Unfortunately, if the stars die while getting a confirmed by natural observation/dissection proper diet, that would probably raise more questions than answers about what the cause is, but if the stars are able to do well long-term, it would really give some credibility to the diet (starvation/nutrition) theory.

That said, I know researchers have been able to breed and rear Crown of Thorn Sea Stars and Sunflower Sea Stars in aquariums successfully, so that would seem to support my hypothesis. Similarly, I know at least a couple of species have been reared from egg/juvenile up in aquariums (Oreaster reticulatus and Linckia laevigata, for example) - I'm not sure how these would have done in longer studies, but they did alright in these ones that dealt with their young stages, and both of these (particularly the Linckia study linked to above, which lasted three years) seem to support my hypothesis (and the current diet speculations pertaining to most biofilm eating sea star species) as well.

 

[Dan_P]

How would you track weight while keeping them underwater? Also it gets increasingly expensive and resource consuming to set up multiple tanks for the stars to test different feeding techniques. How would you design the nutrition study you mentioned?

I would transfer a star in a known volume of water to a container and weigh it. For example, the star would be placed in the container under water and the lid placed on it. This captures a constant weight of water.

I would explore the possibility of large tank with dividers, porous dividers or weirs. This might work if what you feed the stars is attached to a surface and there is minimal cross contamination between walled off sections. The potential food source might be biofilms grown on rocks or sand in other containers and brought to the star fish tanks in shallow containers. The food might be changed out every day or so.

I would think that growing biofilms would need to be started months before the sea stars arrive and would require some work to develop a method to reliably produce this food. Food production will require multiple tanks to produce different types and to house each type at different stages of growth because you will need a continuous supply of a biofilm of a certain age week after week until you determine whether the sea star is starving or thriving.

 

[livinlifeinBKK]

I actually have heard of a study doing weight and length measurements (see the link below) for sea stars, but they weren't testing particular different diets. They were caring for juvenile, post-metamorphosis Linckia laevigata (the survival rate was abysmal, but some did survive) and feeding them "epibenthic microorganisms encrusting dead coral skeletons (Acropora)."

https://core.ac.uk/download/pdf/5093827.pdf

Sand sifters are a good star to try feeding, as they (by all scientific/educational accounts that I’ve seen) should eat bivalves and gastropods rather than biofilms in the wild (in fact, because they swallow their prey rather than digesting them externally, some studies have been done on the stomach contents of a few similar species, so we’d have a relatively good idea where to start with the feeding). So, they should be relatively easy to feed. It would be expensive to test on a large scale, but a small pilot study should be able to show pretty cheaply (aside from the fact that you’d likely have to have certain snail species hand-collected, because they’re not readily available on the market) if that info is accurate. Figuring out proper nutrition with them might be a bit harder/more expensive, but it could probably be done. The results of such a study could potentially support or undermine my hypothesis, so I’d be curious to learn what the results are. Unfortunately, if the stars die while getting a confirmed by natural observation/dissection proper diet, that would probably raise more questions than answers about what the cause is, but if the stars are able to do well long-term, it would really give some credibility to the diet (starvation/nutrition) theory.

That said, I know researchers have been able to breed and rear Crown of Thorn Sea Stars and Sunflower Sea Stars in aquariums successfully, so that would seem to support my hypothesis. Similarly, I know at least a couple of species have been reared from egg/juvenile up in aquariums (Oreaster reticulatus and Linckia laevigata, for example) - I'm not sure how these would have done in longer studies, but they did alright in these ones that dealt with their young stages, and both of these (particularly the Linckia study linked to above, which lasted three years) seem to support my hypothesis (and the current diet speculations pertaining to most biofilm eating sea star species) as well.

Wow that's a really interesting study! Wish they were a little more detailed with the feeding regimen (how often they were fed, what they looked for on the Acropora skeletons to know they were suitable, etc.) and how they housed them. I also wonder if/ to what extent starfish could benefit from probiotics since crabs and other inverts have shown positive responses from probiotics

 

[livinlifeinBKK]

I would transfer a star in a known volume of water to a container and weigh it. For example, the star would be placed in the container under water and the lid placed on it. This captures a constant weight of water.

I would explore the possibility of large tank with dividers, porous dividers or weirs. This might work if what you feed the stars is attached to a surface and there is minimal cross contamination between walled off sections. The potential food source might be biofilms grown on rocks or sand in other containers and brought to the star fish tanks in shallow containers. The food might be changed out every day or so.

I would think that growing biofilms would need to be started months before the sea stars arrive and would require some work to develop a method to reliably produce this food. Food production will require multiple tanks to produce different types and to house each type at different stages of growth because you will need a continuous supply of a biofilm of a certain age week after week until you determine whether the sea star is starving or thriving.

I don't think growing the biofilms in separate tanks would be quite as difficult or take quite as much time as you estimated but I think the hardest part would be ensuring the biofilm being fed to each star was of the same consistency and amount...I was thinking about growing the biofilm on pieces of live rock from the ocean but it would be difficult to assess when enough biofilm had grown on the rocks for the stars to get enough food and tell exactly what the biofilm consisted of because biofilms can easily change in consistency depending on environmental factors

 

[ISpeakForTheSeas]

I don't think growing the biofilms in separate tanks would be quite as difficult or take quite as much time as you estimated but I think the hardest part would be ensuring the biofilm being fed to each star was of the same consistency and amount...I was thinking about growing the biofilm on pieces of live rock from the ocean but it would be difficult to assess when enough biofilm had grown on the rocks for the stars to get enough food and tell exactly what the biofilm consisted of because biofilms can easily change in consistency depending on environmental factors

From what I’ve seen, I’d guess it could take up to six weeks for the biofilm, depending on what stage of biofilm composition is needed.

 

[livinlifeinBKK]

From what I’ve seen, I’d guess it could take up to six weeks for the biofilm, depending on what stage of biofilm composition is needed.

What leads you to think six weeks?

 

[ISpeakForTheSeas]

I’m on phone right now, so I’ll need to get to my computer to find the link, but one of the papers I’ve seen discusses changes in biofilm composition over time, and there are basically early colonization species, some intermediate colonization species, and some late colonization species. If I remember correctly, it takes about two weeks into biofilm formation for the early colonizers to fully colonize the space, two more weeks to change from early colonizers being dominant to intermediate ones being dominant, and another two weeks to transition from that to late colonizers being dominant.

 

[ISpeakForTheSeas]

So I’d guess it could take up to six weeks, but it might not be necessary to wait that long.

 

[livinlifeinBKK]

So I’d guess it could take up to six weeks, but it might not be necessary to wait that long.

I'd be interested in seeing that research...I guess the maturity needed would depend upon what exactly they need to be ingesting...if that's the case and it does take a month or so for the biofilm to mature enough then spot feeding would seem to be necessary for smaller tanks (or the idea I had for feeding pads that could be placed into the tank after being colonized by biofilm). I'd like to find a way other people could keep them that isn't impractical if possible so more people could enjoy them

 

[ISpeakForTheSeas]

I'd be interested in seeing that research...I guess the maturity needed would depend upon what exactly they need to be ingesting...if that's the case and it does take a month or so for the biofilm to mature enough then spot feeding would seem to be necessary for smaller tanks (or the idea I had for feeding pads that could be placed into the tank after being colonized by biofilm). I'd like to find a way other people could keep them that isn't impractical if possible so more people could enjoy them

Here's the specific article I was referencing:

https://www.researchgate.net/publication/356692776_Coral_reef_biofilm_bacterial_diversity_and_successional_trajectories_are_structured_by_reef_benthic_organisms_and_shift_under_chronic_nutrient_enrichment

And a related one:

Prokaryotic community successions and interactions in marine biofilms: the key role of Flavobacteriia

Marine biofilm community structure on a model surface showed a rapid colonization followed by temporal dynamics associated to inter-specific cooperation.

academic.oup.com

 

[livinlifeinBKK]

Here's the specific article I was referencing:

https://www.researchgate.net/publication/356692776_Coral_reef_biofilm_bacterial_diversity_and_successional_trajectories_are_structured_by_reef_benthic_organisms_and_shift_under_chronic_nutrient_enrichment

And a related one:

Prokaryotic community successions and interactions in marine biofilms: the key role of Flavobacteriia

Marine biofilm community structure on a model surface showed a rapid colonization followed by temporal dynamics associated to inter-specific cooperation.

academic.oup.com

Thanks! I think the reason mine has been fine for so long without much individual attention having to be given to him is because I used live rock from the ocean which I imagine was a big plus for him

 

[Timfish]

How would you track weight while keeping them underwater? . . .

Weigh a container of water with and without the starfish.

There are a few books that dive pretty deep into echinoderm biology that I've been reading through and I think I'll try to contact some of the researchers and authors to see if maybe they have some theories as to what might be restricting long term success in captivity... I was thinking that possibly their natural diet is important because starfish lack any type of specialized excretory organ for waste removal. The waste generated from digestion is primarily ammonia which has to be passed into the coelomic fluid and diffused through the body wall somehow. A theory that I see as plausible is that the bacteria and other microorganisms consumed aid in nitrogen transformations that the starfish can't otherwise carry out inside it's body to detoxify the ammonia. This would make sense since many of the microorganisms we think they're consuming naturally have this capability and sponges also contain nitrogen transforming prokaryotes...maybe instead of slowly starving to death, they're slowly being poisoned over time if they don't consume enough of these microorganisms with other foods. Since many species feed extraorally like Linckias and Fromias they might have trouble retaining these microorganisms although the ammonia would be retained in their bodies until it had time to slowly diffuse out over time.

Anoxic conditions caused by bacteria are a serious issue for corals too. Counter intuitively, algae can cause hypoxic conditions for corals.

I know you probably don't need more reading material but this search on google scholar might be interesting:

Google Scholar

scholar.google.com

Although specific to certain species of sea cucumbers and not startfish, one of the papers that pops up with those search criteria was intersting

https://onlinelibrary.wiley.com/doi/abs/10.1111/are.13829

ANd this video is only slightly related but fascinating:

 

[livinlifeinBKK]

Weigh a container of water with and without the starfish.



Anoxic conditions caused by bacteria are a serious issue for corals too. Counter intuitively, algae can cause hypoxic conditions for corals.

I know you probably don't need more reading material but this search on google scholar might be interesting:

Google Scholar

scholar.google.com

Although specific to certain species of sea cucumbers and not startfish, one of the papers that pops up with those search criteria was intersting

https://onlinelibrary.wiley.com/doi/abs/10.1111/are.13829

ANd this video is only slightly related but fascinating:

I'll check it out! Btw, it might just be my imagination but it seems like after running that airstone for a few days or so my star is actually more active... again, could just be a coincidence or my imagination

 

[livinlifeinBKK]

Just an idea but I now have a newly vacated 20 gallon tank and was thinking about carrying out a controlled experiment regarding starfish nutrition using it as the holding tank. The starfish species could be Fromia indica stars since I have easy access to them. I could buy a few of them about the same size and give each one a different mark on an arm to differentiate between each one and use a 20 gallon tank to house them together. The tank would contain sand and live rock from the ocean. One star could be given supplemental feedings of oysters once a week, one could be removed from the main tank for one day a week and placed into a smaller tank where biofilm growth on live rock is aided with a flocculant, and the other could be the control group that receives no supplemental feedings and is just grazes on anything growing on the rocks in the 20 gallon tank. Growth could be measured by weight and tracked every 2 weeks or monthly to determine the effect of the varying diets on growth and presumably health. Additionally, two stars could be used for each feeding regimen to increase likelihood effects observed are diet based. I know the design is far from perfect since I just came up with it this morning but what do you guys think?