Past Articles
Seahorses & Marine Life

Feed Ezy Frozen Mysis

Past Articles
Seahorses & Marine Life

Feed Ezy Frozen Mysis

Past Articles
Seahorses & Marine Life

Feed Ezy Frozen Mysis

Past Articles
Seahorses & Marine Life

Feed Ezy Frozen Mysis

Past Articles
Seahorses & Marine Life

Feed Ezy Frozen Mysis

by Pete Giwojna – from the February 1997 issue of Freshwater and Marine Aquarium magazine (FAMA)


In last month’s installment of “Sea Horse Nutrition” (Part IV: Feeding & Rearing the Fry), you learned how to feed and raise newborn Hippocampids through the crucial ”infant” stage using a diet of newly-hatched brine shrimp supplemented with rotifers during the first week or two of their lives. By the age of about 6 weeks, the young sea horses should have quadrupled in size, reaching a stage in their life where a staple diet of day-old Artemia nauplii can no longer sustain further growth and development*.

In fact, if sea horses are maintained on this inadequate diet beyond the age of 6-8 weeks, there are only two likely outcomes: (1) malnutrition resulting in premature death24 or (2) permanent stunting of the young3.

In 1983, Dr. C.W. Emmens reported an interesting example of the second outcome, in which artificial dwarfing resulted when a brood of Australian Big-Bellied Sea Horses (Hippocampus abdominalis) were raised on a strict diet of newly-hatched brine shrimp3. The young sea horses remained in a neotenic condition, never growing to their full adult length of 10-14 inches (25-35 cm)23, but reaching sexual maturity at a fraction of that size. The dwarf Big Bellies were otherwise perfectly normal in appearance, yet remained at an adult size of less than 3 inches, which allowed them to eat baby brine shrimp throughout their lives3. They bred successfully as runts, and produced stunted young that did the same, so that several successive generations of miniature H. abdominalis were eventually raised. The only difference was that the stunted Big Bellies no longer produced the hundreds of fry typical for their species, but gave birth to around 30 babies3–a brood size that is normal for the Dwarf Sea Horse (H. zosterae).

This is a remarkable case, however, for the consequences of stunting are usually far more severe. As a rule, stunted juveniles develop dietary deficiencies that result in serious health problems, or they simply refuse to accept newly-hatched Artemia once they reach a certain size, starving to death. Ordinarily those that do manage to survive never reach sexual maturity.

This article will therefore pick up where last month’s installment left off, discussing the best foods for raising young sea horses once they outgrow day-old brine shrimp. Sea Horses at this stage are the most difficult to feed, since they are too small to accept readily available foods such as adult Artemia, grass shrimp, Gammarus, or newborn guppies and mollies, yet too large to eat newly-hatched brine shrimp as their sole diet.

This change in dietary requirements marks the transition of the fry from the infant stage to the juvenile stage*, which takes place at 6-8 weeks when they have grown to a length of approximately 1.5 inches. At this size, the young are no longer delicate babies, and the mortality rate of the juveniles drops to less than half that of the fry during the first 1.5-2 months of life9. The period from 2-4 months is a time of rapid growth and increasing survivorship for the juveniles.

THE REARING TANK

At this stage in their development, in addition to a more substantial diet, the young sea horses will also need more spacious accommodations with sufficient room for further growth. (Dwarf sea horses* are an exception. Since they mature at an early age, reaching their full adult size of 1.5-2 inches at around 2 months22, the fry can be transferred directly from the nursery tank to your main display tank with their parents after the age of 6 weeks.)

Juveniles of the larger species, however, should be transferred from their nursery tanks into 10-gallon rearing tanks once they reach a length of 1.5 inches. These tanks should be all-glass aquaria with bare bottoms that have been equipped exactly the same as the nursery tanks with one exception: rather than airstones, the rearing tanks should be provided with air-operated sponge filters of the type commonly known as ”dirt magnets.” Besides aeration, these sponge filters will eventually provide the juveniles with badly needed biological filtration6. In the meantime, follow the same maintenance schedule as you used for the nursery tanks, siphoning off the fecal matter and detritus from the bottom at least once a day while performing a 10%-20% water exchange21.

A STAPLE DIET FOR JUVENILE SEAHORSES:

Cultured Brine Shrimp (Artemia salina)

Once they reach the juvenile stage, the basis of your sea horses’ diet should be enriched brine shrimp between 2-6 days old. This will provide the rapidly growing young with a range of prey of various sizes, since there will nauplii available at all stages of development. (Under ideal conditions, Artemia reach adulthood in 8 days after molting 15 times10.)

The easiest way to raise brine shrimp is to set up 5 or 10 gallon tanks in a sunny location that will encourage an algae bloom, seed these tanks with freshly-hatched Artemia nauplii, and feed them sparingly as described in Part I of this series (FAMA, October 1996). If you set up several small culture tanks according to the instructions in ”Sea Horse Nutrition Part I: Live Foods for Adults,” and harvest small amounts of Artemia from each as needed, the cultures will be self-sustaining and produce enough nauplii to raise a few dozen juvenile sea horses24.

However, this simple system for culturing Artemia is inadequate if you need to provide enough nauplii to feed hundreds of hungry juveniles. This is often the case when you’re dealing with a large, healthy brood from a prolific species such as Hippocampus erectus or H. reidi, or when you have several mated pairs and more than one male gives birth within a short period.

A more sophisticated Artemia culture system is called for under these circumstances. This can be achieved by modifying your conventional rectangular culture tanks to form closed brine shrimp ”raceways” with improved circulation patterns that boost productivity10. The modification involves installing a central partition that is equidistant from all four sides of the tank and then mounting 4 or more air-lift tubes on the sides of the partition (see diagram). The air lifts are positioned so they provide optimum circulation and aeration by producing a circular flow with sufficient upwelling to keep the food particles and shrimp evenly distributed and in a state of constant suspension10.

The converted raceway tanks are then stocked with nauplii at the rate of 1000-3800/liter and maintained under optimum conditions that will maximize brine shrimp production (pH = 8.0, specific gravity = 1.022 to 1.035, temperature = , and low light levels)10. (See the Plankton Culture Manual by Frank Hoff and Terry Snell* for complete instructions on this high-productivity, raceway culture method.)

If you live in an area with a favorable climate, there is an easier method for culturing brine shrimp in large quantities that might be just right for you: raising them outdoors in wading pools or small ponds. Simply install the pond in a suitable sunny location of your yard, fertilize the water with manure, and inoculate it with a starter culture of unicellular marine algae4. Once the algae takes hold and the weather is right, the pond is seeded with brine shrimp eggs and nature is allowed to take its course. Voila! If all goes well, after a few weeks, you can begin harvesting large amounts of brine shrimp in various stages of development on a daily basis4. For a more detailed discussion of the pond culture method, see William Gant’s article in the October 1996 issue of FAMA (”The Brine Shrimp, Part 1V”).

ENRICHING BRINE SHRIMP

No matter which culture method you use, feeding is the key to raising nutritious nauplii for your juvenile sea horses. Newly-hatched brine shrimp deplete their yolk supply within 24-48 hours and must be fed regularly thereafter to maintain their food value18.

Fortunately, brine shrimp are filter feeders and will take in whatever is suspended in water with them. This makes it easy for the aquarist to load the shrimp he is raising with nutritional value by giving them a healthy diet supplemented with special food additives.

Commonly used foods for culturing Artemia include unicellular algae; rotifers; yeast-based emulsions; micronized egg yolk, rice bran, wheat flour or whey; and dried Spirulina algae10.

Research has proven that brine shrimp can be further enriched by adding supplements such as cuttlefish liver oil, cod liver oil, corn oil, fat-soluble vitamins, amino acids, and mineral formulations to their culture water25. Analysis of the nutritional content of culture animals after they had been exposed to such supplemental additives showed a dramatic increase in long-chain fatty acids and many vitamins15.

Rather than experimenting with your own concoctions, I recommend using one of the lipid-rich food concentrates such as Selcon* which have recently been developed specifically for use in aquaculture. Selcon Concentrate is rich in highly unsaturated fatty acids (HUFA) and vitamins C and B-12, which makes it an ideal supplement for culturing Artemia.

For best results, 24 hours after the culture tanks are seeded with newly-hatched brine shrimp, begin feeding the nauplii sparingly by adding Selcon Concentrate at the rate of 0.5 ml per 5 gallons18. Adjust the amount so that a slight haze barely clouds the water for a few hours every day. Do not feed again until the water is crystal clear and do not overfeed. As the brine shrimp grow, you will need to adjust the dosage of Selcon by either increasing the frequency or the amount of the feedings.

The importance of fortifying Artemia in this manner cannot be overstated, since the survival of marine fish fry increases dramatically if they are fed lipid-enriched brine shrimp10. For example, Dynasty Marine Associates* has raised Lined Sea Horses (Hippocampus erectus) and Dwarf Sea Horses (H. zosterae) on a commercial basis using a strict diet of brine shrimp26. Poor survival rates hampered Dynasty initially, but when they began fortifying the nauplii with special additives, the survival rate of the fry improved twelve-fold, and they succeeded in raising large numbers of sea horses to marketable size. The rearing project was eventually discontinued only because the price of the tank-raised specimens was greater than the cost of wild procurement26.

The best way to harvest the enriched nauplii is to use a plankton collector or strain the culture water through a plankton net (available from Florida Aqua Farms). As your sea horses grow, you can sift the nauplii through plankton screens with progressively larger mesh, selecting only the shrimp that are at just the right stage of development for the size of your juveniles.

Some breeders switch their sea horses over to a 14-hour feeding period after the first 6 weeks of life24, but it’s better to continue feeding the juveniles around the clock if you can manage it. Either way, the rapidly-growing sea horses should never be totally without fortified brine shrimp at this stage of their development, so feed them 5-7 times a day or whenever no shrimp are visible in the rearing tanks24.

SUPPLEMENTAL FOODS FOR JUVENILE SEAHORSES

For best results, the juveniles’ staple diet of lipid-enriched brine shrimp should be supplemented with wild zooplankton or artificially-raised plankton in the form of Daphnia, mosquito larvae, and Mysids or amphipods in the early stages of development.

Marine Zooplankton

Marine zooplankton can easily be collected by anyone who lives within a reasonable distance of the ocean6. Simply tow a plankton net (an elongated conical net made of fine material) slowly behind a boat in an area well away from possible sources of pollution, stopping periodically to empty its contents into a collecting container. (A mesh size of 250-500 microns will collect plankton that are about the right size for juvenile sea horses.) Cover the collecting bucket with a damp towel to keep it cool during the heat of the day and provide aeration to make sure the plankters stay alive until you get home. When you return from a collecting trip, just strain the plankton-rich water through a brine shrimp net and deposit the residue in your rearing tanks.

Adult Daphnia

Daphnia may be worth a try for inland aquarists who must raise their own zooplankton. Commonly called water fleas, adult Daphnia are 1.5-2 times bigger than newly-hatched Artemia nauplii10, making them a useful supplement for juvenile sea horses that have recently outgrown baby brine shrimp. (In fact, juveniles are the only size sea horses that consistently show any interest in Daphnia, since the water fleas are too large for newborns to eat, yet so small that adult Hippocampids ignore them.)

Proceed with caution, however. Daphnia do not last long in saltwater and even juvenile sea horses often reject them. It’s a good idea to collect a few water fleas and offer them to your sea horses on a trial basis before you swing into full production. Then, if they’re a hit, you can consider raising Daphnia according to the instructions in ”Sea Horse Nutrition Part I: Live Foods for Adults” (FAMA, October 1996).

Mosquito Larvae

If your juveniles refuse the Daphnia, mosquito larvae are a good alternative. Of all the supplemental live foods, they are the easiest to raise (indeed, many suburbanites go to great lengths every summer trying to prevent hordes of the pesky skeeters from breeding in their backyards.)

Just fill a big plastic bucket or washtub with dechlorinated tap water and place it outdoors in a shady location. Before long, the female mosquitoes in your neighborhood will have discovered the container and deposited their eggs on the surface, forming tiny rafts that contain 100-300 eggs apiece6. The eggs soon hatch into air-breathing larvae that hang at the surface to breathe through their snorkel-like tails. Known as ”wrigglers” for obvious reasons, the larvae filter the water for food, and you can hasten their development by adding a little rabbit chow or a few handfuls of leaves to the tub to stimulate the growth of the bacteria on which they feed.

The life cycle from egg to winged adult takes anywhere from six days to more than two weeks, depending on the temperature6. The larvae must be harvested regularly to prevent any of the wrigglers from maturing into biting adults. The longer you delay between harvests, the larger they will grow, allowing you to select wrigglers that are the perfect size for your juvenile sea horses.

Begin to store egg rafts in your fridge as soon as cold weather approaches. (Once refrigerated, the eggs can be hatched out up to 12 years later6!) This will allow you to hatch out the eggs as needed and provide your pampered ponies with live larvae throughout the winter.

Salt marsh mosquitoes are best, since they survive indefinitely in saltwater3, but if you don’t happen to live in a coastal area, freshwater wrigglers may also last long enough to be useful if your juveniles like them. If you’re using freshwater larvae, be sure to remove any uneaten wrigglers before they begin to die and foul the tank.

Unfortunately, as easy as mosquito larvae are to provide, not all sea horses will accept them. The air-breathing wrigglers congregate within the first few inches of the surface, where sea horses are unaccustomed to feeding, and their unorthodox swimming style–a succession of spastic lurches–puts off some of the juveniles.

Possum Shrimp (Mysis sp.)

Mysids are small shrimplike crustaceans with a heavy carapace covering their thorax. Adapted to life in estuaries, these are tough, hardy little hard-bodied crustaceans that can withstand a wide range of salinities and temperatures. They are commonly called possum shrimp because the females carrying their developing young in a bulging pouch or marsupium formed by thoracic plates at the base of their legs. Females carry broods of up 30 in their pouches, although 6 or 7 is the normal brood size, and the young are not released until they are well-developed juveniles that are 4-5 times bigger than newly-hatched Artemia nauplii–an ideal size for juvenile sea horses that have recently outgrown day-old brine shrimp. Females produce young continuously, moving more eggs into their pouch as soon as they release their latest brood. The juvenile Mysids will reach their adult size of 1 inch (1.25 cm) in about 3 weeks, producing a new generation every 30 days. Laboratory strains of tank-raised Mysids are available that have been selected for resistance to disease and are pre-adapted to aquarium life.

All in all, Mysids are a superb food for sea horses which could serve as their staple diet if only they could be produced in sufficient quantity. In fact, Australian experts are so successful in rearing the spectacular sea dragons (Phycodorus and Phyllopteryx sp.) on a diet of Mysis shrimp12–the only food the delicate dragons will accept–that tank-raised specimens of these fabulous fishes may soon be available in the U.S. I have never met a sea horse that didn’t attack Mysis shrimp with great gusto, and although they are more difficult to culture than mosquito larvae or Daphnia, it is worth the extra effort to raise them.

The following culture instructions are based on the methods used by Ray Lewis to raise disease-free Mysids on a commercial basis at Aquatic Indicators* in Florida. Mr. Lewis stresses that culturing Mysids is a time-consuming, labor-intensive project, but that it can be accomplished by anyone who is willing to put in the time and effort required.

Set up a 20-gallon high or larger all-glass aquarium equipped with standard undergravel filters at either end11, but leave the center of the tank bare (no U.G.s) to facilitate collecting the Mysids with fine-meshed nets. For example, if you’re using a 30-gallon culture tank, install U.G. filter plates designed for a 10-gallon aquarium at both ends of the culture tank, but leave bare glass at the bottom in between the undergravels. Adjust the specific gravity to about 1.022 and set the temperature at 11.

Once the tank has cycled and the biofiltration is fully established, introduce 20-30 adult Mysids to get the culture started. Establish a photoperiod of 16 hours of light and 8 hours of darkness (Mysids mate at night), and perform 10% water changes every week. Feed generously with newly-hatched Artemia nauplii at least twice a day11. To maximize growth and reproduction, try to maintain a density of 2-3 brine shrimp per ml of culture water. (You should already have your brine shrimp production line running full steam for your sea horse fry, so it should be an easy matter to divert a portion of its prodigious output toward the culture of Mysis shrimp instead.)

One of the keys to raising Mysids is separating the adults from the young to prevent cannibalism. For laboratory studies, this is often done manually by isolating the adults, transferring ovigerous (egg-bearing) females to a culture dish, and removing the juveniles with a pipette as they drop14.

A better method can be devised that will automatically separate the juveniles from the adults, if you are willing to set-up a separate tank just for the adults alongside the main culture tank. Keep the top of this isolation tank exactly even with the top of the culture tank, and position an air lift tube in a corner of the adult’s tank so that it returns water to the main culture tank, while a siphon tube in the opposite corner maintains the water level (see diagram) between the tanks. The air-lift tube should be sheathed with plankton netting or nylon screen with a mesh size (800 microns) that will restrain the adults while allowing the larvae to pass through unimpeded11. Likewise, the end of the siphon tube should be covered with 500 micron plankton netting that will allow newly-hatched brine shrimp to pass through but not the juvenile Mysids. Adjusting the air lift so it produces a slow, gentle, steady flow of water will automatically deposit the juvenile shrimp in the main culture tank while keeping the adults isolated in the adjacent tank, thereby eliminating cannibalism.

MYSID CULTURE SYSTEM

This system will automatically separate juvenile Mysids from the adults, reducing losses due to cannibalism. Identical 20-gallon high all-glass aquaria are set up side by side, connected only by an air lift and siphon tube. Adult Mysids are isolated in tank 1, and when ovigerous females release the young from their pouches, the juvenile Mysids are systematically transported into tank 2 via the air lift tube, carried along passively with the circulating water (the 800 micron screen attached to the air lift will restrain the adults while allowing the juveniles to pass through freely.) The siphon tube maintains the water level in the tanks, but it is shielded with a 500 micron screen that is too small for the juvenile shrimp to slip through, so once they pass through the air lift to tank 2, the juveniles are safely confined there. Artemia nauplii can pass freely through both screens. (Note: 1000 microns = 1 mm.) Drawings by Pete Giwojna.

It is best to let the population of Mysids build up for a couple of generations to increase your brood stock before you begin harvesting regularly. This means starting your cultures about 6-8 weeks before you need the shrimp, so if you set up the Mysid tanks when your sea horse fry have just been born, the timing should be perfect. You will be able to begin harvesting useful amounts of immature Mysids when your juvenile sea horses are 6-8 weeks old, ready to make the transition from baby brine shrimp to larger prey. For example, when your brood stock numbers 400-500 adults, you should be able to harvest about 200 Mysis nauplii per day to feed your juvenile sea horses–enough to help round out their diet.

To harvest the shrimp, sweep a net through the water column over the bare glass at the center of the tank, and select the Mysids that are the best size for your sea horses. Using nets with progressively larger mesh will allow you to gather Mysis nauplii that are the perfect size for your sea horses as they grow. Be sure to leave 20% of each generation of Mysids behind to mature in order to keep the culture self-sustaining.

One of the biggest obstacles to raising Mysids is obtaining a supply of shrimp to start a culture. Aquatic Indicators is one of the few companies that sell live Mysis shrimp11, but the smallest order they handle is $25, not including the overnight shipping, which will run about another $20 or so. An order that size will include about a hundred Mysidopsis–enough for several starter cultures–so perhaps one solution to this problem is for a group of interested hobbyists or an Aquarium Society to pool their resources to cover the minimum order and then divide up the Mysids between the members.

Leptochirus Amphipods

If your time is limited, you may be better off raising amphipods than Mysids. Leptochirus amphipods are an excellent low-maintenance food for juvenile sea horses that just about anyone can raise in their spare time.

Just fill a shallow, inert container with 1.5-2 gallons of seawater adjusted to a density of 1.015, and cover the bottom with a layer of fine silt 1/4-1/2 inches deep. (New plastic dishpans measuring 40cm x 30cm x 15cm are the preferred cultured containers, but rectangular glass or ceramic pans will work just as well.) Add an airstone to each container to provide continuous aeration. A temperature of works well for these amphipods13, but slightly higher temps will accelerate growth and development, improving productivity. However, higher temperatures also reduce the margin for error and increase the danger of a crash due to overfeeding or overpopulation.

The most important factor in the culture of Leptochirus amphipods is the layer of organic mud in the which the amphipods live. These tiny crustaceans inhabit mucous tubes in the mud, and they will be unable to construct these dwellings if the consistency of the substrate is unsuitable17. It must consist of fine silt no bigger than 500 microns in diameter13 (1000 microns = 1mm).

The best way to provide the silt is to gather mud from estuaries, mudflats, salt creeks or salt marshes at low tide (a bucket and a shovel will suffice for this) and strain it through a 500 micron sieve17. Avoid beaches since you need an area with little or no water movement where the fine silt can settle out and form thick deposits. (Inland aquarists will have to gather their mud from ponds, shallow bays in lakes, or backwaters in creeks or streams.) Scoop up the first few inches of mud only17. (If you go too deep, you will hit regions of anaerobic decay where harmful substances such as ammonia or sulfide build up. Should that happen, searing lungs and curling nosehairs will quickly alert you to the fact that you’ve dug too deep!)

Sieving the mud is necessary to remove particles of sediment that are too coarse, detritus, and numerous organisms that might prey on the amphipods or compete with them for food17. If the silt still seems to contain too many life forms after its been strained, it’s advisable to freeze it in order to kill off the unwanted organisms. Freezing will cause the silt to form clumps, and before it can be used, it must first be thawed and passed through a blender to restore its consistency17.

If you’ve done everything properly, the sifted silt should have about the same consistency as chocolate frosting. A little of this rich mud goes a long way, since you merely apply it to the bottom of the culture containers as if frosting a cake, putting down just enough silt to make a thin layer 1/4-1/2 inch thick13. (A deeper layer could result in anaerobic pockets.)

When filling the container, take care to disturb the layer of organic silt as little as possible. Set a plastic saucer above the bottom to act as a turbulence reducer27 and gently pour the culture water into the container. Seed the culture containers with 100-200 amphipods each, again taking care not to disrupt the bottom as you add the Leptochirus-laden water. Remove any injured or unhealthy amphipods which fail to burrow into the silt.

The preferred method for raising these amphipods* is to give them regular feedings of unicellular marine algae17. Three times a week, siphon off half of the water from the top of each container and replace it with freshly mixed saltwater that has been pre-adjusted to the culture parameters, and add 1-liter of diluted greenwater. [If you’re using rotifers as the first food for your sea horse fry, the microalgae cultures you’ve already established to feed the rotifers will work equally well for Leptochirus, and you should take advantage of this fact to raise these ampipods on greenwater. (See ”Sea Horse Nutrition Part IV: Feeding & Rearing the Fry” for tips on culturing microalgae).

However, most hobbyists will prefer the easier alternative of raising these hardy crustaceans with solid foods (which are also routinely used to supplement the diet of Leptochirus fed on algae). Ray Lewis (Aquatic Indicators) prefers Tetra Min for this and Chris McManis (Eastcoast Amphipods) recommends the following recipe: mix 2 parts of Tetra Min flake food with 1 part Hermit Crab Cakes and grind the mixture into a fine powder using a mortar and pestle or similar implements13. Every second or third day, after changing 60% of the culture water as described above, add a pinch or two of this food to the surface of the water as a supplement for greenwater. It must be ground finely enough so it floats on the surface and is dispersed evenly across the top of the water17.

If you are using solid foods as the amphipods’ sole diet, you should also allow small fragments of Tetra Min flakes to settle on the bottom. (Try to scatter them thinly yet evenly over the mud, and alternate between vegetable and protein-based flakes.) With experience, you will soon learn how much to feed and how to adjust your feedings as the population builds. As a rule of thumb, the bottom food should all have been eaten by the time you make the next water exchange. If the uneaten flakes start to turn white or gray, they are fungused–a sure sign that you are overfeeding27.

Culturing Leptochirus with solid foods usually results in lower yields and a greater risk of a complete wipeout than feeding them algae, but if you feed carefully and follow your maintenance schedule meticulously, it can be an effective technique that is simple enough for anyone to try. Just feed sparingly–overfeeding will lead to fungal outbreaks or fouling of the water which will cause the culture to fail 13.

Each female produces up to 60 eggs, and the larvae will grow to full size (0.6-1.2 cm) and produce a new generation every 30-40 days17. If you start out with 100-200 adult amphipods, you could begin harvesting useful numbers of juvenile Leptochirus after you let the population grow for two weeks, but its best to allow the initial culture to build up undisturbed for about 2 months. By then, the culture will need to be thinned out, and you can divide the adults into several separate containers, establishing a number of new cultures. This way, you can keep several culture containers going simultaneously, and alternate which one you harvest the crustaceans from each time. (You can monitor the progress of your cultures by counting the number of burrow openings.)

To collect the amphipods, use a turkey baster to gently suck up a little of the silt, taking care to disturb the culture as little as possible, and strain the fine mud through a 500 micron plankton screen or sieve17. (A 700 micron screen will collect amphipods 4 mm or larger; a 500 micron screen will catch amphipods 2 mm or above; and a 250 micron screen will gather tiny Leptochirus l mm in length27.) Carefully squirt a little culture water onto the screen to rinse the silt through the mesh, and the well-washed amphipods will be left stranded on the screen. Select only the specimens that are the best size for your sea horses, and return the rest of the amphipods and the strained silt/water to the culture container, using a turbulence reducer to avoid disrupting the rest of the colony.

In a regular aquarium, these crustaceans would quickly disappear into the substrate, out of your sea horses’ reach, but the glass bottoms of the rearing tanks leave the amphipods with nowhere to hide. Juvenile sea horses can’t resist chasing them down, and hunting amphipods will soon become their favorite pastime.

To sum up, baby sea horses outgrow newly-hatched brine shrimp when they reach a length of 1.5 inches or 4.0 cm at the age of 6-8 weeks. As juveniles, they require a more substantial diet with more variety than they did as newborns. The best way to meet this need is provide the juveniles with lipid-enriched brine shrimp between 2-6 days old as their staple food. This basic, everyday diet should be enhanced with liberal supplements of zooplankton, small Mysis shrimp and Leptochirus amphipods, adult Daphnia and/or salt-marsh mosquito larvae that have been sifted to provide prey of just the right size for the rapidly-growing sea horses.

Dwarf sea horses will likewise thrive on the same basic dietary regimen of fortified brine shrimp, but their supplemental foods should be limited to zooplankton or adult Daphnia. At their diminutive size, juvenile pigmies cannot swallow larval mosquitoes, mature Mysids or adult amphipods.

When they are provided with a nutritious diet such as this, there will be very few losses among the juveniles, which will reward the diligent hobbyist by growing at an amazing rate. The Steinhart Aquarium found that well-fed Lined Sea Horses (Hippocampus erectus) grew about half an inch each month during this stage, reaching a length of 2 inches after 2 months, 2.5 inches after 3 months, and 3 inches at the age of 4 months8. Dwarf Sea Horses (H. zosterae) develop at an even more blistering pace, more than doubling in size during their first 2 weeks of life20. In the aquarium, these prolific ponies reach sexual maturity and their full adult size (up to 1k inches) in just 2 months, and produce a new generation of dwarfs every 2.5-3 months21!

Juvenile sea horses of the larger species enter their subadult stage at the size of 3-4 inches, which coincides with the onset of sexual maturity between the ages of 4-6 months (depending on the species). From that point on, they can eat the same foods as fully adult sea horses 2: fortified adult Artemia, small grass shrimp, Gammarus, livebearer fry (baby mollies, guppies19, gambusia, etc.), and so on. Fortunately, the live food cultures you have already established for the juveniles can still provide the bulk of the diet for the larger subadults. Simply begin harvesting the adult Mysids, Leptochirus amphipods, and brine shrimp now that your sea horses are big enough to eat them.

We have now come full circle. The best foods and techniques for feeding sea horses of this size have already been described in Parts I, II, and III of ”Sea Horse Nutrition,” and the subadults can now be moved one last time to transfer them from the rearing tanks back into the main display tank with their parents. Before you know it, the young adults will begin courting, pair up, and produce young of their own.

Before bringing this series to a close, however, I would like to mention a new Sea Horse Feeder1 that has just come on the market and which promises to make delivering live foods to these finicky eaters much easier in the future. It is basically a screened cylindrical enclosure with a mesh size that is too small for adult Artemia to squeeze through, yet large enough that sea horses have no trouble pulling shrimp out through the holes (see photo). Sea Horses seem to get the hang of the new feeder right off and will immediately adopt the shrimp-filled enclosure as their primary feeding station1. They will anchor themselves directly to the shrimp cage and greedily suck out the shrimp all day long from this convenient perch, using their slurp-gun snouts to extricate the tasty crustaceans with all the skill and dexterity of surgeons. The way sea horses feed from this enclosure always reminds me of birds eating from a suet feeder.

This simple device will help preserve your precious live food by reducing wastage. No longer does a portion of your tank-raised treats have to be wasted when it is filtered out or disappears into the nooks and crannies where your sea horses can’t reach it1.

The sea horse feeder is designed for adult brine shrimp, but there should be a mesh size that works equally well for other live foods of similar size (3-1 inch) such as medium Mysis shrimp, Gammarus isopods, or Leptochirus amphipods. And it should be especially useful with live foods like freshwater Gammarus that have a limited life expectancy in saltwater. They can be placed directly in the enclosure, where the sea horses are accustomed to feeding and they cannot escape, making it much more likely that will be eaten before they die. Any prey items that do expire will be safely contained for easy removal before they foul the water.

SUPPLIERS

Florida Aqua Farms
5532 Old St. Joe Road
Dade City, Florida 33525
Phone: 904-567-8540

Florida Aqua Farms carries a complete line of products for use in aquaculture, including starter cultures of marine microalgae, rotifers, and Gammarus; plankton collectors and plankton netting; liquid food concentrates for enriching culture animals (Roti-Rich, MicroAlgae Grow), and the Plankton Culture Manual (tips on raising microalgae, rotifers, ciliates, Daphnia, and Artemia).

Aquatic Indicators, Inc.
P.O. Box 632
St. Augustine, Florida 32085-0632
Phone: 904-829-2780

Aquatic Indicators provides live Mysids (Mysidopsis bahia) and Leptochirus amphipods.

Chesapeake Cultures
P.O. Box 507
Hayes, Virginia 23072
Phone: 804-693-4046

Chesapeake Cultures offers live Leptochirus and starter cultures of Mysids and Daphnia.

Paul Baldassano
Urchin Searchin Enterprises
1600 Imperial Avenue
New Hyde Park, N.Y. 11040
Phone: 516-488-7324

Paul Baldassano makes the Sea Horse And Reef Fish Feeder described in this article.

American Marine
54 Danbury Rd. Suite 172
Ridgefield, CT 06877
Fax/Phone: 914-763-5367

American Marine makes Selcon Concentrate for enriching Artemia and other organisms.

Author’s Note: If you are a beginner who is considering keeping sea horses for the first time, remember that breeding these fascinating fish is a painstaking, time-consuming process. In order to breed them, they must be given a healthy, balanced diet. That means collecting live foods in the field, maintaining live food cultures at home, patiently training them to eat nonliving prey and frozen foods, and even conditioning them to accept hand feeding. Rearing the fry requires culturing microalgae and zooplankton, and converting your bedroom into a veritable brine shrimp factory. A brutal feeding regimen and a strict cleaning schedule must be adhered to without fail. Nursery and rearing tanks must receive partial water changes twice daily. Anyone who is unwilling or unable to follow these rigorous routines should stick to less demanding fish more suitable for the novice.

However, I strongly encourage experienced sea horse keepers to consider breeding and rearing their charges. Even if you are only successful in raising a few of the fry, providing your own replacement stock this way can still help preserve sea horse populations in the wild, which are already under heavy pressure from habitat destruction, dredging, trawling, pollution, the curio trade and folk medicine (dried sea horses are considered an aphrodisiac throughout the Orient). There is no greater reward for an aquarist than a herd of healthy Hippocampids you personally raised at home from birth.

Interested hobbyists are urged to join The Breeder’s Registry, which publishes the Journal of Maquaculture and operates a central depository of information on propagating marine life. Its objectives are to encourage closed-system captive breeding of marine organisms in order to limit demands on wild populations, and to act as a registry for active breeders to acquire and exchange broodstock and increase gene pools.

To become a member or just to request more information on breeding and rearing sea horses, contact Stanley D. Brown at the following address:

The Breeder’s Registry P.O. Box 255373 Sacramento, California 95865-5373

E-mail address via the Internet: [email protected] Telephone: (916) 487-3752.

In addition, in order to assist in sea horse conservation efforts, Dr. Amanda Vincent (a leading expert on the captive breeding of sea horses around the world) is currently working with Neil Garrick-Maidment to establish a central registry of serious sea horse keepers and a directory of breeding and rearing information in the U.K

Dedicated aquarists are encouraged to send their advice and suggestions on keeping sea horses to Neil Garrick-Maidment at the following address: Sea Horse Captive Breeding Coordinator 1 St. James Terrace Exeter, Devon EX4 6HQ England

Acknowledgments

The author is very grateful to Ray Lewis of Aquatic Indicators, Chris Schlekat of the Department of Environmental Health Sciences at the University of South Carolina, and Chris McManis of Eastcoast Amphipods13 for taking the time to discuss the techniques used to culture disease-free Mysis shrimp and Leptochirus amphipods in the laboratory, and for their suggestions on how these methods can best be adapted by hobbyists for raising these organisms on a smaller scale at home.

REFERENCES

(1) Baldassano, Paul. 1996. A new feeding strategy for Hippocampus sp. and other fishes. The Journal of Maquaculture. Volume 4, Issue 3: 18-19.

(2) Bellomy, Mildred D. 1969. Encyclopedia of Sea Horses. T.F.H. Publications, Inc.: Neptune City, New Jersey.

(3) Emmens, C.W., PhD. 1983. Sea horses. Tropical Fish Hobbyist. February 1983:

51-57.

(4) Gant, William (Bubba) Jr. 1996. The brine shrimp, Part IV. Freshwater And Marine Aquarium. October 1996: 144-147.

(5) Ginsburg, Isaac. 1937. Review of the sea horses (Hippocampus) found on the coasts of the American continent and Europe. Proceedings of the United States National Museum. 83, (2997): 497-594.

(6) Giwojna, Pete. 1990. A Step-By-Step Book About Sea Horses. T.F.H. Publications, Inc.: Neptune City, New Jersey.

(7) Giwojna, Pete. 1990. Color variations in the dwarf sea horse. Sea Horse Update. 11, (5): 3-4.

(8) Herald, Earl S. Living Fishes of the World. (Tube-mouthed Fishes: 146-150.) Doubleday & Company, Inc.: Garden City, New York.

(9) Herald, E.S. and Rakowicz. 1951. Stable requirements for raising sea horses. Aquarium Journal 22: 234-242.

(10) Hoff, Frank F. and Snell, Terry W. 1987. Plankton Culture Manual. Florida Aqua Farms: Dade County, Florida.

(11) Lewis, Ray. 1996. Aquatic Indicators, Inc. P.O. Box 632. St. Augustine, Florida 32085-0632. (Personal communication.)

(12) Mackay, Bruce (Curator). 1991. Underwater World. P.O. Box 424, Hillarys. Perth, Western Australia 6025. (Personal communication.)

(13) McManis, Chris. 1996. Eastcoast Amphipods. P.O. Box 377. Kingston, Rhode Island 02881. (Personal communication.)

(14) McKenney, Charles L., Jr. and Celestial, David M. 1955. Interactions among salinity, temperature, and age on growth of the estuarine mysid Mysidopsis bahia in the laboratory through a complete life cycle. I. Body mass and age-specific growth rate. Journal of Crustacean Biology. Volume 15, Number1: 169-178.

(15) Riddle, Dana. 1994. Coral Nutrition, Part V: trace elements and the reef tank. Freshwater And Marine Aquarium. August 1994: 40-56.

(16) Saldariaga, Hector. 1990. Aqualand Pet Center. P.O. Box 55-7365. Miami, Florida 33255-7365. (Personal communication.)

(17) Schlekat, Chris. 1996. University of South Carolina. Department of Environmental Health Sciences. Columbia, South Carolina 29208. (Personal communication.)

(18) Selcon Concentrate User’s Guide. 1990. American Marine, Inc.: Ridgefield, Connecticut.

(19) Schmidt, Thierry. 1995. About sea horses. SeaScope (Winter 1995) 12: 2.

(20) Strawn, Kirk. 1953. A Study of the Dwarf Sea Horse, Hippocampus regulus Ginsburg, at Cedar Key, Florida. Master of Science Thesis, University of Florida.

(21) Strawn, Kirk. 1954. Keeping and breeding the dwarf sea horse. Aquarium Journal. Volume 25, Number 10: 215-218, 227-228.

(22) Strawn, Kirk. 1958. Life history of the pigmy sea horse, Hippocampus zosterae Jordan & Gilbert, at Cedar Key, Florida. Copeia. 1958, Number 1: 16-22.

(23) Vincent, A.C.J. 1990. Reproductive Ecology of Sea Horses. Ph.D. Thesis, University of Cambridge: 15, 61.

(24) Vincent, Amanda, PhD. 1995. Sea Horse keeping: feeding adults, mating, rearing the young, mariculture. The Breeder’s Registry. Volume 3, Number 2: 1-5.

(25) Watanabe, T., Tamiya, T., Oka, A., Hirata, M., and C. Kitajima. 1983. Improvement of dietary value of live foods for fish larvae by feeding them on Omega-3 highly unsaturated fatty acids and fat soluble vitamins. Bulletin Japanese Society of Scientific Fisheries. 49 (3): 471-480.

(26) Young, Forrest. 1991. Dynasty Marine Associates. 10603 7th Avenue, Gulf; Marathon, Florida 33050. (Personal communication).

(27) 1994. Methods for Assessing the Toxicity of Sediment-associated Contaminants with Estuarine and Marine Amphipods. Office of Research and Development. U.S. Envirnmental Protection Agency. Narragansett, Rhode Island 0288.

Footnotes

The Wilhelmer Aquarium reports that young sea horses find Artemia difficult to digest, and no longer flourish on a strict diet of baby brine shrimp past the age of 6 weeks.

The life cycle of the sea horse can be divided into 4 different stages (infants, juveniles, subadults, and adults) based on changes in their dietary requirements, growth rate, and mortality. In general, as tank-raised sea horses advance through each successive stage of development, their growth becomes more gradual, their mortality rate improves, and they need a more varied diet of increasingly more substantial foods.

The infant stage lasts from birth until the fry have reached a size where newly-hatched brine shrimp can no longer sustain them. This occurs when they have grown to a length of about 11 inches at the age of approximately 6 weeks. Infancy is a period of high mortality and very rapid growth, during which the fry will roughly quadruple in size. The juvenile stage begins when the fry are 6-8 weeks old and lasts until the first indications of pouch development at the age of around 4 months. Mortality drops sharply during this 2-21 month period, which is also a time of rapid growth that will see the young roughly double in size from 11 inches to about 3 inches.

The young adult or subadult stage is marked by the onset of sexual maturity which takes place at about 4-6 months of age when the juveniles reach the size of 3-4 inches. The pouch develops in males at this size, allowing subadult sea horses to be sexed. Growth slows and there are relatively few losses at this stage.

Adulthood is the reproductive phase of the sea horses life. Growth stops at this stage, since the adults have reached their maximum size and are now sexually mature. The size and age at which sea horses reach the adult stage varies widely with the species.

Dwarf sea horses are considered to be those species, such as Hippocampus zosterae and H. bargibanti, which mature at a size of less than 3 inches. Since fully grown dwarf sea horses likewise require a more substantial diet than their fry, and fall within the size range that designates juveniles of the larger species, the suggestions in this article regarding the juveniles of larger sea horses also apply equally well to adult dwarfs.

Available from Florida Aqua Farms (Phone: 904-567-8540).

Available from American Marine (Fax/Phone: 914-763-5367).

Dynasty Marine Associates 10603 7th Avenue, Gulf Side Marathon, Florida 33050 Phone: 305-743-7666

Mysids are very sensitive to heavy metals, organic pollutants, pesticides and other toxic chemicals and are raised in large numbers by companies like Aquatic Indicators for use in research labs and environmental testing.

For more detailed instructions on culturing Leptochirus plumulosus and other amphipods, consult Methods for Assessing the Toxicity of Sediment-asociated Contaminants with Estuarine and Marine Amphipods. To obtain a copy of this reference, contact the U.S. Environmental Protection Agency, Office of Research and Development, in Narragansett, Rhode Island 02882 and ask for manual EPA/600/R-94/025.

CAPTIONS AND LEGENDS

(38) Trim Waistline: This pony shows the slender, undifferentiated abdomen typical of sea horses in the juvenile stage of development. Notice that the abdomen of this specimen is only about as big around as the base of its tail, into which its belly blends almost imperceptibly, so that it’s difficult to tell where the abdomen ends and its tail begins.

It is not until the juveniles are about 4 months old that the ovaries begin to mature in the females and the first signs of pouch development appear and in the males9, marking their transition into the subadult stage. Only then will the young adults begin to increase more in girth and start to develop the characteristic pot-bellied profile of mature adults.

Sea Horses in the size range of juveniles (approximately 1.5-3 inches) are the hardest to feed because they are at a stage that’s too large to subsist on easily-provided day-old brine shrimp, yet too small to accept the readily available foods that are suitable for fully-grown sea horses, such as adult Artemia, baby guppies and mollies, or grass shrimp. This article will explain how to overcome these obstacles and provide juvenile sea horses with a balanced, nutritious diet that can sustain their rapid rate of growth.

(39) Dining Companions: Here we see a group of colorful, 1-2inch Dwarf Sea Horses (Hippocampus zosterae) feeding alongside a dark-colored juvenile Lined Sea Horse (H. erectus) that’s twice their size. Despite the difference in their sizes, they share the same feeding requirements and can be kept together on a staple diet of lipid-enriched Artemia nauplii between 2-6 days old. The pygmies’ diet should be further enhanced with zooplankton and adult Daphnia, which are foods their larger companion might also enjoy at its present size.

However, the blackish Lined Sea Horse is nearing the end of the juvenile stage, and it should also be receiving supplemental feedings of Mysis nauplii, Leptochirus amphipods, and sifted mosquito larvae to round out its diet. A well-balanced feeding regimen such this will help prepare the rapidly-growing juvenile for the onset of sexual maturity when it makes the transition into the subadult stage of development.

(*Slides #40-45) Living Jewels: Color Morphs of the Dwarf Sea Horse (Hippocampus zosterae). The normal coloration of the Pygmy Sea Horse is a mottled shade of tan or fawn5, but as you can see here, unusually marked and brightly colored specimens of every description turn up from time to time. The specimens shown on this page arrived in single shipment from Aqualand Pet Center18 in Miami, Florida, and included no less than six distinct color variations7: canary yellow, jet black with ringed tail, pinto pattern, golden-bronze, chocolate brown, and pearly gray.

At present, very little is known about sea horse genetics, so the field is still wide open, and Dwarf Sea Horses are ideal subjects for selective breeding and genetic research. They are exceptionally tough and hardy8, breed readily in captivity, exhibit marked variation in coloration–an easy trait to track–mature rapidly, and are quite prolific, producing a new generation every 2.5-3 months20. Researchers could follow their traits through 4 generations in a single year.

Consequently, I feel it’s only a matter of time before true-breeding strains of the color morphs of H. zosterae become established in the hobby. Although co-dominance and sex-linkage may be involved in certain cases, at least some of these color patterns are single-gene, autosomal recessive traits, which can be easily developed through a careful breeding program7.

For example, if a canary yellow male was crossed with a normal fawn-colored female under these circumstances, 100% of their offspring would be heterozygous, carrying one allele for their mother’s dominant color and one allele for their father’s recessive color. They would thus all be fawn colored in appearance, yet all carry one copy of the gene for their father’s bright yellow coloration.

If brothers and sisters from this first cross are then mated together in the second generation, their offspring will be 25% homozygous dominant (normal fawn color), 50% heterozygous dominant (fawn colored in appearance, but carrying one copy of the gene for canary yellow), and 25% homozygous recessive (bright yellow in color, having received the recessive gene from both parents).

Mating the bright yellow brothers and sisters from this second cross together will then produce 100% canary yellow offspring which are homozygous for that trait, and a pure-breeding strain will have been developed in just 3 generations.

(46) Pint-Sized Ponies: As you can see, Dwarf Sea Horses (Hippocampus zosterae) are so tiny that several adults can fit comfortably inside a SeaTest Hydrometer. Pygmies reach their full adult size (1.5-2 inches) two months after birth22, and considering their diminutive dimensions, there is no need to set up separate rearing tanks for the juveniles. Rather, after the age of 6 weeks, the rapidly maturing juveniles can be transferred directly from their nursery tanks back into the main display tank with their parents.

(No animals were injured in the filming of this picture. The sea horses were released none the worse for wear after spending less than 2 minutes in their cramped quarters in order to provide a convenient size reference that all marine aquarists would instantly recognize.)

(*Slide #47 & Print #48) Alpha and the Omega: the Beginning and the End. These two photos show young Lined Sea Horses (Hippocampus erectus) at opposite ends of the juvenile stage of development. For instance, the juvenile Lined Sea Horse posing beside the Merman’s Shaving Brush in Slide #47 is already 3 inches long, and will soon be making the transition from the juvenile to the subadult stage of development. By contrast, Photo #48 shows a group of much smaller erectus at the other end of the spectrum that were breed and raised by Paul Baldassano at Urchin Searchin Enterprises. At a length of approximately 1.5 inches, they are about the same size as the adult Dwarf Sea Horses shown in the previous picture, and are just entering their juvenile growth phase.

Unlike the dwarfs, however, these youngsters have now reached the size where they must be transferred from their 2-gallon nursery tanks into larger 10-gallon rearing tanks with sufficient room for further growth2. They are still growing rapidly at this stage, and will more than double their size within the next 2-3 months, a fact that makes spacious rearing tanks a necessity for juvenile sea horses of the larger species such as erectus.

(Print #49) A New Device for Feeding Sea Horses: This picture shows a mated pair of Hippocampus erectus eating from a live food enclosure designed by Paul Baldassano at Urchin Searchin Enterprises1. As you can see, the mesh is too small for adult Artemia to escape through, yet the openings are large enough that sea horses can easily suck out the shrimp.

Called the Sea Horse and Reef Fish Feeder, this handy device is perfect for the hard-working hobbyist who can load it with ”feed-and-forget” live foods in the morning and then be on his way. Sea Horses will dine from the feeder all day long at their leisure with no danger of your precious live foods escaping into the substrate or being lost to filtration.

The shrimp cages are currently being used by a number of wholesalers and pet dealers who find them invaluable for feeding sea horses in bare tanks with continuous filtration1. Without the feeders, the brine shrimp gets filtered out in a manner of minutes under those conditions. Because of their difficult feeding requirements, sea horses arrive at our local fish stores in a state of near starvation all too often, and I’m a strong supporter of anything that makes it easier for collectors, dealers, and wholesalers to keep their stock well fed en route. (Photo by: Paul Baldassano/Urchin Searchin)

*For more detailed instructions on culturing Leptochirus plumulosus and other amphipods, consult Methods for Assessing the Toxicity of Sediment-asociated Contaminants with Estuarine and Marine Amphipods. To obtain a copy of this reference, contact the U.S. Environmental Protection Agency, Office of Research and Development, in Narragansett, Rhode Island 02882 and ask for manual EPA/600/R-94/025.

*The Wilhelmer Aquarium reports that young sea horses find Artemia difficult to digest, and no longer flourish on a strict diet of baby brine shrimp past the age of 6 weeks.

*The life cycle of the sea horse can be divided into 4 different stages (infants, juveniles, subadults, and adults) based on changes in their dietary requirements, growth rate, and mortality. In general, as tank-raised sea horses advance through each successive stage of development, their growth becomes more gradual, their mortality rate improves, and they need a more varied diet of increasingly more substantial foods.

The infant stage lasts from birth until the fry have reached a size where newly-hatched brine shrimp can no longer sustain them. This occurs when they have grown to a length of about 11 inches at the age of approximately 6 weeks. Infancy is a period of high mortality and very rapid growth, during which the fry will roughly quadruple in size. The juvenile stage begins when the fry are 6-8 weeks old and lasts until the first indications of pouch development at the age of around 4 months. Mortality drops sharply during this 2-21 month period, which is also a time of rapid growth that will see the young roughly double in size from 11 inches to about 3 inches.

The young adult or subadult stage is marked by the onset of sexual maturity which takes place at about 4-6 months of age when the juveniles reach the size of 3-4 inches. The pouch develops in males at this size, allowing subadult sea horses to be sexed. Growth slows and there are relatively few losses at this stage.

Adulthood is the reproductive phase of the sea horses life. Growth stops at this stage, since the adults have reached their maximum size and are now sexually mature. The size and age at which sea horses reach the adult stage varies widely with the species.

*Dwarf sea horses are considered to be those species, such as Hippocampus zosterae and H. bargibanti, which mature at a size of less than 3 inches. Since fully grown dwarf sea horses likewise require a more substantial diet than their fry, and fall within the size range that designates juveniles of the larger species, the suggestions in this article regarding the juveniles of larger sea horses also apply equally well to adult dwarfs.

*Available from Florida Aqua Farms (Phone: 904-567-8540).

*Available from American Marine (Fax/Phone: 914-763-5367).

*Dynasty Marine Associates 10603 7th Avenue, Gulf Side Marathon, Florida 33050 Phone: 305-743-7666

*Mysids are very sensitive to heavy metals, organic pollutants, pesticides and other toxic chemicals and are raised in large numbers by companies like Aquatic Indicators for use in research labs and environmental testing.


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