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Raising Stenopus and Lysmata Larvae

By Luis Magnasco and Rob Toonen. Posted to The Breeders Registry emailing list, 15th November to 7th December 1998.

Rob:

I have a bunch of comments for you but they will likely seem disjointed and irrelevant unless I cc some of your message back along with my reply, so although this is going to be much longer this way, I'm going to go through and address your comments one-by-one after your text.

Luis:

I'm glad you are active in the list. I'd like to comment on my recent attempts with zoea of L. debelius , L. amboinensis and S.hispidus . I read with interest your series on invert. culture in our Journal. But when I began trying shrimp larvae, I used a set up as for fish larvae, as shrimp larvae of these genera are large and predators since birth. Though they take rotifers, they capture and eat instar 1 and 2 of artemia nauplii.

Rob:

IME they do much better when also provided with phytoplankton culture. Many large aquaculture facilities are starting to include phytoplankton for their fish larvae as well, not because they are likely to eat it directly (although some might, who knows), but because the mortality of larvae when phytoplankton are included is significantly lower (I have seen reports of up to 75% reduction in mortality) than when it is not. I wouldn't abandon the phytoplankton just because the larvae are predatory. Furthermore the Dungeness crab (which I currently work on) produces a much larger and more voracious larva than does Lysmata , but I find that they still ingest a significant amount of algae in culture (enough so that the guts of the animal glow greenish/gold under the microscope)....

Luis:

Yes,I thought about using phyto. Although these larvae are confirmed predators,I have seen green material being passed in Stenopus larvaes gut. And Lysmata larvae wave their legs like filter feeding. Besides it would be good to have the prey organism,ie.brine shrimp gut loaded with phyto. I have done this with fish larvae and rotifers,which is aform of co-culturing.

Rob:

That's the primary idea -- if nothing else, at least the brine will be gut-loaded. There are other hypothesized benefits, but for our purposes, none of that matters as long as the mortality drops. I'll discuss this issue more at the end of the message.

Luis:

But my current problem is that my larger mesh is 200 microns which holds baby artemia and their cyst shells. I need something larger. Straining thru this mesh I am returning to culture all live and dead brine plus dead larvae. If I give phyto,brine shrimp will soon outgrow my larvae. But If I dont,I will have starved and dead nauplii,which is worse!. I could use rotifers until I get the larger mesh.

Rob:

Try fiberglass or plastic mosquito mesh (~1000 microns) from the local Home Depot (or whatever you have at hand) - you won't find anything suitable for cheaper than a roll of that, and the mesh size is almost perfect for retaining the larvae and letting the nauplii and such through. The other alternatuve is to break the tip off a pipette, turn it backwards, so that the broken portion is within the bulb, and use that to individually move the larvae into the new containers. I have done this with a varitey of larvae, and although it is the most time consuming of culture methods, it is also generally the most effective.

Luis:

Local mosquito screen is 1200 microns and shrimp larvae pass thru. I am making a sieve with some 800 microns mesh I cut from a filter media bag.

Typically the larvae feed well and grow thru their different stages without much loses in the first week. Somewhere in the second week they start to die. Very few survive the third week, molting and growing, but die in the fourth.

Rob:

Sounds like either a nutritional or water quality issue. It could also be a toxic factor.

Rob:

I could be - but in most studies of "nutritional value" of various foods, inadequate or inappropriate foods show the same pattern - very little loss in the first week (during which there is typically also very little mortality in the unfed controls), then higher and higher mortality followed by catastrophic losses at 3-4 weeks. That makes me suspect the food is insufficient, and that's why I suggested supplementing with phytoplankton.

Luis:

Mortality occurs in peaks of about 50% in certain days seemingly related to molting with change of stage.

Rob:

This is pretty normal. Molting is about the most stressful stage of development for these guys.

Luis:

They also coexist with the development of heavy growth of hydroids in the rearing systems, though I could not see any direct harm produced by them.

Rob:

Hydroids are cnidarians, and as such possess nematocysts. Depending on the species, they may not be able to penetrate the hardened exoskeleton of the shrimp, but *all* of them should be able to sting the heck out of a newly molted larva. It could very well be that your mortality is related to molting because that is when the larvae are most vulnerable to being stung by the hydroids.

Luis:

Yes and perhaps also more sensitive to toxic factors.

Rob:

Well anything is possible, but I sorta doubt that -- as I said, I am not aware of any water-soluble toxic compounds produced by any hydroids that would cause the effect you mention. It is most likely that the hydroids are stinging the larvae if there is any effect, and there is no reason to hypothesize a more complicated (and previously unknown) mechanism to explain something that is straightforward.

Irrespective of the hydroids direct impact on the larvae, they are bad for larval culture:

  • they consume a significant amount of the food provided for larvae, forcing you to increase feeding rates to provid the larvae with enough food;
  • they kill a lot of prey that they fail to ingest, and simply drop it, causing a buildup of rotting prey in the culture vessels and leading to rapid detrioration of water quality;
  • they produce nitrogenous wastes, just like any other living critter, and lead to decreased water quality.

The presence of hydroids in the system is usually a sign of negligence in water quality -- they cannot get established unless they are introduced with the water (which means that it must be unfiltered tank water or taken from some system in which the hydroids are present), and the larval water *must* be of outstanding quality for long-term success of the larvae.

Luis:

They are a pest and show up everywhere. If I feed brine,they grow like weeds. If I dont,they still survive on copepods or something. Copper doesnt affect them. I have two sp. They must have come with live rock and then contaminate my filter sponges. I wondered if they did not come with artemia,though I dont think cnidaria could possess resting cysts. I have seen fish larvae in them.

Rob:

As I said, there are no marine hydroids of which I know that could be imported with the cysts, but if you want to test your idea, decapsulate the cysts and make sure that nothing comes with them.

In general hydroids are incredibly hardy, and they can withstand the most punishing "cures" we've been able to throw at them. We've had hydroids invade our rearing systems before, and it was only when we gave up trying everything we could think of, filled the entire system with hot DI water, and allowed it to circulate for a week (we initially tried this for a couple of hours, but some of the hydroids survived) that we finally got rid of them. It only takes a little food for them to take off, and in a larval rearing system, there is more than a little food...

You are probably not willing to undertake such drastic measures with your tanks, and for that reason, you are unlikely to ever rid yourself of the hydroids completely. You can continually removes them, and inject boiling water or muriatic acid into any that you see, but you will most likely only succeed in keeping the population down, not erradicating it.

Luis:

They are too small for injecting them,easier is to siphon them out. But as you say,they come back. Now your idea of circulating fresh water for a week could be worth trying,if I only find ten tanks to house my broodstock pairs!. Im sure nitrif.bacteria will not be very much affected. I wish I could ged rid of them. I dont know if you followed my old thread here about fish eggs failing to develop in this system,but there is something strange there,eggs fail to develop,and now all fish quit spawning altogether. I suspect an UTF (unidentified toxic factor). I cant blame the hydroids,it could be bacterial,or else,but every time these guys show,I have problems. Id rather live without them.

Death is sometimes sudden; I was once watching a large amboinensis zoea when it suddenly stretched its body like in a spasm, fell to the bottom, shaked two times and died. Checked with the scope it showed the exuvia still attached to its legs.

Rob:

Unusual, but anything can happen -- death is frequently unexplained in larvae.

Luis:

But most of the times it is preceeded by some days of weakness, with the larvae remaining on the bottom ,unable to keep themselves in the water column. No pathological changes are seen in the larvae, other than the milky opacity of death.

Rob:

Again sounds like a nutritional or water quality issue.

Luis:

Diet

BS nauplii, instar 1 followed by 2, or instar 2 from the beginning was the staple. As I was convinced that I was dealing with a nutritional problem, something that the larvae need for their development but is not provided by brine shrimp, I tried many different commercial larval feeds and enriched the artemia with phyto.(Nanno,)Selcon,Selco and Algamac. The larval feeds, in different combinations, was given in addition to the staple of brine shrimp(OSI,Utah).

Rob:

Three comments:

  1. I'll reiterate my thoughts on the importance of feeding live phytoplankton along with these prey items. The prey should be gut-loaded with phytoplankton and some HUFA supplement, as you indicate, but I think it is also important to provide some algae directly to the cultures. I would aim for 10^3 - 10^5 cells per ml of the mixture I suggest in the JoM article.
  2. Nanno is a reasonable food item to include (it's about 35% protein, and one of the best "growth" foods available), but is completely lacking in DHA (22:6). It is a decent source of EPA, but unless the diet is supplemented with T-Isochrysis (almost lacking in EPA, best source of DHA), you're missing some essential nutrients.
  3. Ditch the OSI Artemia. Comparisons of the nutritional quality of Utah and San Francisco Bay nauplii showed that Selco-enriched Artemia from Utah are *the same as unenriched* nauplii from SFB. Pay the extra $10 a pouind (hmm, actually with the current market I'm not really sure of the price -- I stockpiled before the shortage) and get the SFB shrimp.

An aside that is likely of interest here is that Reed Mariculture (a large oyster aquaculture outfit here in California) is now producing a "cryopreserved algae paste" that is sold to the general public through Inland Seafarms ( http://www.seafarm.com/ ). I am currently in the process of testing the frozen algae in side-by-side trials with the live phytoplankton cultures I maintain to raise larvae here in the lab. I have a student rearing a variety of larvae on single-species cultures of all the algal pastes we could currently get from the folks at Inland (4 species, but they plan to market more) and comparing growth, survival and (possibly) metamorphic success of larvae reared entirely on the frozen algae to siblings raised entirely on the live cultures. I don't really have the results yet (at least not anything I'm willing to stand by), but the initial results are looking good, and when I get some more data, I'll post a review of the product to the list.

Luis:

Water

I used Red Sea brand. As I had reported here, adult shrimp are killed by water changes of more than 10% of new water, so I changed with good quality water of some established tank. I supplemented with iodine(said to help molting)and trace elements,from the same manufacturer.

Rob:

Two comments:

  1. If the adult shrimp die with even a 100% water change, there is something *seriously* wrong with the water. I perform 100% water changes on my breeding tanks every couple of days as a matter of maintenance and never see that sort of mortality -- even when using artificial salt. I have used Instant Ocean, Reef Crystals & Forty Fathoms all without any mortality in the crustaceans I keep. I have performed the same experiment (by accident) on my large reef tank when we had a powerhead meltdown contaminate the entire aquarium, and I had to mix up IO to replace 100% of the water -- no deaths in any of the crustaceans ( L. wurd. , L. amb. S. his among others). Get a new brand of salt!
  2. The requirement of iodine for crustacean molting is a wives tale -- there is *no* scientific basis for it. In fact, quite the opposite, iodine seems to be a poison to crustaceans, and causes premature molts. I'm told it has been used to trigger premature molting in a variety of species for research (and this might be where the myth comes from), but this is an unnnatural phenomenon and is generally accompanied by high mortality.

We had a recent discussion about this on one of the reef mailing lists. The general conclusion was that there is some evidence that iodate is useful to certain types of marine algae. It seems to be more or less inert with respect to vertebrates. Whether or not it is potentially of any use to other marine phyla is unknown, but it pretty clearly not required for normal molting in crustaceans (no matter what you read on a bottle of iodine supplement in you LFS). A search through the literally *thousands* of scientific papers on the physiology of molting in crustaceans turns up not a *single paper* that mentions iodine/iodide. Personally, I would recommend against using iodine supplements in any tank, but *especially* one in which you are trying to rear larval crustaceans!

Luis:

This last comment (one salt mixes) finally convinced me that:

  • A-There is somethig very wrong with Red Sea salt
  • B-Water from my fish system is unsuitable. Filters need badly improvement,nitrites show often and nitrates are in the 100-150 ppm range even with heavy changes.
  • C-There is nothing bad with new ASW.

Rob:

I don't know that it is Red Sea salt exactly, it could be your tap water, or it could be a function of the amount of chelating agents in the salt -- can you buy any of the "sludge" salts that don't require the addition of EDTA and the like to aid fast dissolutiona and keep the salt from clumping? I know there used to be a brand of salt (I forget the name) that was just super concentrated paste and you dilute the stuff to NSW concentrations. If I remember correctly the rep. told me that it was pure salt (although it would be worth double-checking, of course).

Luis:

So I put my three elder L.amboinensis larvae in new Instant Ocean water. Next morning they were all dead!. So it was not Red Sea,must be my tap water?. But I used it so many years without a problem!. My local tap water is pretty soft,taken from the River Plate. Nobody needs RO here,even for reef tanks. Perhaps lead poisoning from my old pipe line?.

Rob:

Unlikely, but certainly worth having checked if you're worried -- lead posioning ought to affect you just as badly as it would affect the larvae, and if this is the culprit (although I don't think it is) you should be having those lines replaced for your own health.

Luis:

Before running to have my tap water analyzed and ordering a RO unit,I dissolved IO salt in good distilled water and put my remaining 15 amboinensis larvae in it. Guess what? Next day 14 were dead and the remaining was covered of some whitish floculent stuff on all the appendices. Also all bs nauplii were dead except for some still in the hatching membrane. Only the Gammarus were unharmed. What could it be that bad?. I tried it again with some few Stenopus larvae and the same happened only that artemia survived this time.

This is driving me crazy. If it is not the salt and it is not the water,what the hell could it be?. I an theoryzing that perhaps newly dissolved ASW could have some suspended particles clogging their branchiae or something. I could try paper filtered water. But that HAD to be seen by somebody before!.

Rob:

Well, I generally prefer to use water that is at least a week or more old. I usually mix 100 gal at a time, let it circulate vigorously for a week or so before adding it to my tanks. As I mentioned in the articles, there are a variety of chelating agents in salt that are potentially toxic to larvae (although they should not be to the adult shrimp -- that's why I was concerned when you told me that a moderate water change killed the adults). Theoretically bacterial action should remove those chelating agents and render the water safe for larvae (I have not tested this, and still prefer to use only filtered NSW for my larval cultures because of these compounds).

Luis:

Now if new water kills the larvae and my used water is very polluted,I have to find some way to have used water free of nitrogenous wastes. Perhaps taking water of a 10 g. Jaubert system I set according to Tom Millers "easy reef". Or using again NSW. So many variables!

Rob:

What are the water conditions in that tank? 10g isn't very much water to run a larval culture system, though. If the water parameters on the "Jaubert-style" tank are good, you might want to consider setting up a larger tank, or making periodic trips to the coast and getting a larger amount of water when you do.

Luis:

Every 2 days I take 2 liters from it and replace with new ASW.

But I will quit with these larvae until I receive 400 and 600 mesh Nitex and some SF brine shrimp. Will see then.

Rob:

I should clarify my earlier statements regarding the nutritional quality of brine shrimp (following a reply I got to that message pointing out that it was untrue:

Your statement that nutritional quality of the San Francisco Bay instar-I brine is equivalent to Selco-enriched Utah brine is doubtful. EPA levels of SFB cyst range between 0,3-13,3% (Leger et al, 1986), DHA is not mentioned. Utah nauplii enriched with Super Selco have a EPA level of >28,6%, a DHA level of 14% and a total of 50,3% HUFA based on dry matter (Merchie, 1996).

This is all true -- I realized that I shouldn't have said they are of "equivalent nutritional quality", because it is virtually impossible to define "nutritional quality" in any useful way. I should have said: there is no difference in the growth and survival of the larvae of a variety of fishes (milkfish, striped bass, hybrid bass, cod, and others that I can't remember anymore) fed premium instar-I SFB nauplii and those fed enriched instar-II Utah nauplii (if anyone wants the references, Email me). A variety of studies presented at a recent meeting showed that unenriched instar-I SFB nauplii and a variety of enriched instar-II Utah nauplii were approixamtely equivalent in terms of growth and survivorship (there were no statistic differences among the treatments), but that both outperformed (showed significantly higher growth and/or survivorship) than unenriched Utah nauplii. I have not seen any studies providing results of the opposite pattern -- hence my flippant comment that that nutritional quality of the San Francisco Bay instar-I brine is equivalent to Selco-enriched Utah brine is certainly inaccurate in terms of the % composition listed above, but in terms of what really matters to any of us (growth & survival of the larvae) it is not. I still think it is a good idea for you to track down some premium SFB cysts if you can.

Luis:

Systems

I started with ten g, with and without filter sponge. As conditions were not the best, I switched to 10 liters cylinders, closed by 100 microns Nitex mesh. These cylinders were placed in a system consisting of 2 ten g. and a 15g with ugf and protein skimmer. This set up allowed for acceptable water conditions while providing high food concentrations. But the mesh clogged after 2 weeks, as algae and hydroids developed on it.

Rob:

Again two comments:

  1. What are "acceptable water conditions?" UGF generally lead to increased levels of nitrate in the system, and nitarte is unsually toxic to many larvae. Although levels of 10 mg/l (and sometimes as high as 40) seem to be common in many coastal regions, similar levels in aquaria seem to prove toxic to many species. I do complete water changes on the system every second day to keep levels of *all* nitrogneous byproducts below detectable levels.
  2. If there is a buildup of algae and hydroids in the system, they are coming in from somewhere. The culture water should be effectively sterile, and without any idea of what else is added to the system (e.g., toxic dinoflagellates, pathogens, ciliates, algal spores, other larvae, etc.) you have no real control over the rearing of the larvae. Ideally, you want the rearing system to be free of potential competitors, predators and pathogens. The only way to do that effectively is to filter any and all water that enters the system. This is simply accomplished by either installing an in-line micron filter off a pump to "automate" filtration, or simply dripping the water through a coffee filter. There are practically a thousand alternative ways to accomplish filtration, but without it, algal spores & hydroid larvae are bound to reinvade the system.

Luis:

I was progressing at a snails pace, may be breaking my previous survival record, just one more day, and with one or two larvae. Then I started to think that the problem might not be nutritional after all. For one thing, commercial pennaid hatcheries use brine shrimp and they replace it partially with prepared feed only to save in costs, not to improve development. Also, L. wurdemanni were raised on BS(SeaScope on line article,our web site). What could it be? Water? As I reminded your favour of natural sea water in your work, I set a 10 g with filter sponge and natural water I brought from the sea. (quite a drag living 400 km away). At first things were wonderful and I was confident I was in the good trail. But after 2 weeks the old horror scene showed: larvae dieying and hydroids spreading. Even artemia dissapeared in less than 12 hours, no matter how many I gave. A bell ringed: SOMETHING TOXIC? Perhaps the Hydroids produce it?

Rob:

Unlikely -- there are no water-soluble toxic compounds of which I am aware that are produced by hydroids of this type. I would suspect high food availablility and a general decline in water quality lead to ideal conditions for the growth of hydroids (which sting larvae -- a few are almost never fatal, but if you get stung by enough bees, you'll die too), which coupled with the water quality issue leads to the demise of your larvae.

I do prefer natural seawater (NSW) to artificial (ASW), but primarily because there are some species of larvae that do not survive when cultured in ASW (and we've just discovered tissue culture cell lines suffer the same fate on ASW in our lab). This could be due to something as simple as the larvae being bacterial feeders that require some additional nutritional input lacking in sterile ASW, or it could be due to the chelating agents (e.g., EDTA) used to prevent clumping of the artificial salt and speed the dissolution in water. In either case, for my research, I use NSW. I am unconvinced that your problem is related to either of those issues -- the more I hear, the more it sounds like a water quality issue to me.

Luis:

Only 4 larvae, 17 days old were around but probably due to die that day. So I put one in a jar of new ASW, but it died soon like the adults. Then I put two others in a 2 liters jar filled with water from my fish system, nothing special, nitrites at 0.2 ppm,UV treated. I left the fourth larva in the tank.

Rob:

Nitrites at 0.2 is pretty high for a well-established system, and is not what I would consider "acceptable water conditions" for larval culture. Ideally you should be looking at 0 nitrites, 0 ammonia and nitrates on the order of 0.2....

Luis:

Next day the larva in the tank was dead, but the two in the 2 liter jar were OK. I did some tests with artemia and the tank water trying to confirm a toxic factor for artemia,but they were inconclusive. Back to the two larvae. Again following your methods, they were kept with a weak air bubbling, fed with artemia enriched with phyto and Algamac. Every 48 hr I scooped the larvae into a new clean jar with "new"system water. The larvae kept living and growing and the method seemed perfect.

Rob:

Glad to hear that something worked!

Luis:

I wish I could now say "and they grew and became 2 beautiful happy little shrimp-The End". But no. The larvae developed up to stage 6, I believe, and then stopped growing. They still kept living past the 40 days mark and at the end became weak and died one some days after the other. But this could be a different problem, fail to metamorphose, which you also mentioned in your articles.

Rob:

That may be a problem that is due to the number of larvae remaining in your system. Often larvae are searching for a specific settlement cue in order to metamorphose into the adult form. If they find that cue, they settle & metamorphose -- if not, they delay settlement until an appropriate cue is presented. In the few species which have been examined so far, there is some proportion of larvae that settle specifically in response to the settlement inducer, but also some small proportion of larvae that settle in reposnse to just about anything. That proportion can range from 0 to about 40% or so, and was found to vary among families. Given that, it is a bit of a crap-shoot in getting the larvae to settle and metamorphose unless the specific settlement inducer is known, and unfortunately for us, that is a mystery for the *vast* majority of species.

Luis:

So lets go back to the 2 liter jar systems.

Delighted as I was with the jars, I put all new larvae coming in these. But to scoop 2 larvae out is different than moving say 200. So I strain them thru a 200 micron sieve, and wash them back into a clean jar. The problem is that this size of mesh retains most debris including brine shrimp and their cyst shells. Pollution is very bad, even if I am now changing water every 24 hr. In one case, I had a bacterial bloom with a fall of DO but was luckily washed away. Changing water more frequently is more than I can do and siphoning the bottom is not easy.

Rob:

Daily changes should not be necessary unless larval density is *very* high. Usually with larval densities on the order of 1000 per liter (for crustaceans) odd-day changes are more than sufficient. I could have sworn that I suggest using 2 screens (one for the larvae one to clear out everything else) in the JoM articles -- did I forget that? Anyhow, if you find that the 2 screen method doesn't work, you may need to go to direct scooping/pipetting of larvae, or pipetting the debris away from the filtered larvae each cleaning. If that proves too much work, it's best to cut down on the number of larvae and/or the number of cultures you keep. I know it's hard, but let some of the larvae stay in the tank as food -- you're better to end up with 1/10 the inital number of healthy metamorphs than 10X the number of sickly unmetamorphosed larvae, right?

Luis:

I think that I need a mesh size that retain larvae but let the other stuff run away, 400 or 600 microns. In the meantime,I put some amphipods in the jars as scavengers. They seem to work and are even reproducing.

Rob:

They could also be competing with/preying on the larvae, depending on the species. Personally, I think this is a bad idea for microculture techniques like we are discussing here. If you want to go to a natural system and try for a work free "mesocosm" environment in which larvae grow through metamorphosis without any specific culture, that's different. But in terms of micro-managed larval cultures, IMO, absolutely clean and pure is the best way to go.

Luis:

I hope I have not tired you and the list with this long story but would like to hear your opinion on this. This jar system could work well for larvae that withstand such a rough handling.

Rob:

It even works well for "wimpy" larvae that can't take any rough handling (like the prosobranch veligers, limpets and nudibranchs that I am culturing using this technique right now). You just have to be a lot more gentle with them, but it still works fine.

Luis:

It allows too the use of antibiotics when needed,without fear to interfere nitrification. What antibiotics and doses are currently being used in larval research?. Still penicillin/streptomycin?.

Rob:

Yep Pen/Strep is still the one of choice. Didn't I outline that in the JoM article, either? Man my memory is slipping!

Luis:

Could you indicate working doses?

Rob:

The Penncillin can be used at concentrations of 25 to 150 micrograms per ml (1 microgram is approximately 1.65 units), and once dissolved is stable for about 3 d. Thus it is important to store the mixed antibiotic in the freezer and only remove small aliquots to dose the culture as needed. Streptomycin (Dihydrostreptomycin is more stable in marine systems if you can get it) can be used at concentrations of 500 to 200 micrograms per ml, and once dissolved is stable for ~90 days (if kept cold and dark). I generally mix the two into a 100 or 1000X solution, aliquot that mix into small vials wrapped in tinfoil to prevent light penetration, and then store the stocks in a freezer. I remove a vial only long enough for it to thaw, be well mixed and the appropriate amount of solution withdrawn before placing right back in the freezer.

Luis:

Just some last minute update with a couple of interesting findings. In my last message I said I was going to quit with the larvae until I get the larger micromesh. But you know what?. New little larvae were born and I did not have the heart to let them go. So I set again them in 2 "Toonens jars". This time I decided to use only 0 ammonia,0 nitrite,0 nitrate water. Also rotifers instead of brine shrimp,as I can filter them out with my current sieves. And phytoplankton,as you advised,for the reasons given by you.

Rob:

The few studies of which I know that have compared growth on rotifers and Artemia nauplii for shrimp larvae, have found that growth on the nauplii was faster, but survival on the rotifers was initially higher (at least until the shrimp reached the stage at which energetic requirements of catching the rotifers exceeded the nutritional value of eating them). The best result was obtained by adding both to the cultures and allowing the larvae to choose for the first couple of weeks. Personally I would add both in addition to the phytoplankton and aim for the most complete diet possible.

Another thought occurred to me -- an interesting side note from this study was that there is a bell-shaped relationship between feeding density and larval growth. Growth of shrimp larvae feed that too few (<10 rotifers per ml) or too many (>40 rotifers per ml) prey items significantly decreased survival and growth rates of the larvae. The same result was obtained with Artemia nauplii (ideal feeding amount was 9 nauplii per ml). Are you over- or underfeeding your larvae?

Luis:

This time I gave rotifers at different concentrations:10-50/ml,and phyto. As all my Nanno cultures crashed,I used a "weed"algal(cyanobact.?)species,long and slender filaments,100x0.5 microns. Larvae in the three systems:Jauberts water,NSW,and carbon treated ASW,showed same evolution,living well until day 5 and all dying between day 6/10. It agains looks like a nutritional problem.

So I set:

  • Jar#1-New IO water,made in tap water. Because of the unexplained lethal effects of ASW in these shrimp already discussed,and as I suspected some undisolved particles clogging the branchial apparatus,I took the water from the surface of a tall undisturbed mixing vat,and paper filtered it. I put half of this water and half of the parents old water.
  • Jar#2-Water from a Jaubert style mini reef,again half and half.

Next morning,guess what?. All larvae in jar#1 were dead or dying! Some few stray artemia nauplii and copepods in the same jar were unaffected. Larvae in jar#2 were mostly OK.

More new larvae were coming so I set two more jars with half parents water and:

  • Jar#3-1/4 NSW
  • Jar#4-1/4 IO water,this time made in distilled water,BUT aerated overnight in a bucket with a bag of carbon.

Next (this) morning,wow!,they were all OK!. I topped the jars with NSW and IO water and they are still OK.

I have just changed the water of the 3 jars so it is now 100% Jauberts,NSW and IO. Checking the larve I saw an internal organ,shaped like a butterfly,]I[ packed with dark green material.

So I have two interesting findings today:

  • A-There IS a shrimp lethal factor in artificial sea salts,which can be removed with activated carbon.
  • B-Larval Lysmata filter feed on phytoplankton. This was unexpected as they are also predators of large preys.

Rob:

  • A-That could be one of the variety of chelating agents added to commercial salts. I believe I warned of this in the original articles, didn't I?
  • B-I have observed the same thing with the variety of shrimp larvae that I have raised. I would continue to feed them phytoplankton and also supplement the early stages with rotifers. Remember to keep the feeding densities about equal and of the appropriate amount.
Created by liquid
Reefs.org
Last modified 2006-11-24 18:41
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