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The Importance of Fish and Other Sea Life in Medical Research

It has been a long-understood fact that the tranquility of aquariums has been known to help relieve stress and lower heartrate and blood pressure in some. As the biomedical field continues to grow and become more important to advancements in health care, the methods and options used by research also continue to expand. During this expansion, aquatic and marine organisms are becoming important in making advancements towards the health of all of us. Some of the fish and invertebrates you have in your home aquariums may someday help to save your life. Here are just a few of the organisms researchers have turned to:

Zebra Danio (Danio rerio): This fish is one of the most widely-used by researchers. They have Zebra Daniobecome model organisms used for genetics research, neurological and other medical research, environmental studies and even organ and tissue regeneration. Specific genes have even been identified in different color pattern mutations. One of the most brightly-colored community aquarium fish, the popular Glo-fish, is a variation of the Zebra Danio that was original spliced with jellyfish DNA to create a fluorescent fish used to detect pollution and toxins. Zebra Danios are even on the very short list of animals that have made a trip into space!

Horseshoe Crab (Limulus polyphemus): TheHorseshoe Crab Horseshoe Crab is right next to the Zebra Danio in terms of the number of studies it participates in. They have compound eyes that have become important in vision research and a substance found in their blood known as Limulus amebocyte lysate (LAL) can help researchers detect bacteria and pathogens in medications and human tissue. LAL is collected in much the same way a person donates blood and the crabs can be released after collection. You can read all about them here.

Mussels: Mussels, the clam-like bivalves popular in aquariums and seafood restaurants alike, are already helping to heal wounds and have established their staying power in the medical field with their…well, staying power. Mussels used very thin filaments known as “byssal threads” to attach to hard surfaces. The adhesive that they use to attach themselves to surfaces is similar to the “Krazy Glue” and superglues that we all use to piece together broken mugs at home, but is much more effective in the salty, wet environments where the bivalves live. This adhesives is also extremely strong but still flexible. Researchers at companies like Johnson and Johnson have developed glues from the byssal thread compounds (warning: some graphic surgical images) that help to seal wounds and reattach bone fragments without the use of foreign materials like stitches and sutures.

Mantis Shrimp: This notorious group of invertebrates has earned a bad reputation in the aquarium industry as Mantis Shrimpthe secretive live rock hitchhikers known to pick off tankmates or even break aquarium glass, all while earning a following with a select few as an original showpiece. Among researchers, their powerful strikes and extremely complex eyes have made them the subject of many studies. The strike of a mantis shrimp is one of the most powerful and fastest strikes in relations to their size and researchers have studied their mechanics to discover how this power is possible. The eyes of the mantis shrimp can convert polarized light wavelengths and function over almost the entire light spectrum from infrared to ultraviolet, a feat our own eyes can’t even come close to. Their ability to convert and filter light across this spectrum has led researchers to look at mantis shrimp as the next step in optical devices like CD and DVD systems. While most of the research on mantis shrimp still seems to be focused on the “how’s”, it is only a matter of time before scientists discover how we can use what the mantis shrimp teach us.

Platies and Swordtails (Xiphophorus sp.): These two groups of livebearers are very popular, bright little community fish but recent research has given them a much more profound meaning. These livebearers are some of the first subjects to prove that some cancers like certain melanomas are actually hereditary and can be passed to offspring. Some of the dark pigment cells in these fish have been known to multiply out of control and form cancerous tumors. Remarkably, some of these fish can actually continue to live and thrive even with these tumors – and they can reproduce and pass this condition on to their young. While some forms like the popular Mickey Mouse Platies can form melanomas in the spots by their tails, it is more apparent in fish with a lot of black in their coloration. Scientists are working to understand how this condition is passed and how the fish can continue to live with it.

Corals: In addition to providing some color to the Zebra Danios already mentioned, some corals are giving Capnella sp.biomedical scientists some inspiration in designing medications. Scientists have recently discovered capnellene, a compound found in a species of soft corals that can be used as a painkiller and may provide relief to those suffering from Multiple Sclerosis and other neurological conditions. Some of the same fluorescent proteins used to color Glo-fish are also being applied to some cancerous cells, allowing researchers to much more easily track their spread.

This is just a small sampling of how animals that have long been popular in the aquarium trade are being used to improve health and medications for all of us. As we as aquarists work to keep our own aquariums alive and healthy, those same fish and invertebrates may be working to save our lives as well.

Thanks for reading,


An Aquarist’s Glossary of Terms – Part 3

Eileen here. Below is a glossary of some general aquarium hobby terms. Once complete, we’ll try and publish the Aquarist’s Glossary of Term’s somewhere online, but in the meantime, hopefully it helps in pieces. Check out part 1 and part 2 here.

General Aquarium Hobby Terms:

  • Compatibility: This refers to how well tankmates are likely to get along. For example, Neon Tetras are compatible with Zebra Danios – they would be fine together in a tank. A ten inch Peacock Grouper however, would NOT be compatible with a one inch Skunk Cleaner Shrimp – the shrimp would likely end up a meal pretty fast.
  • Coral “Frag”: A “frag” is a small piece or colony of coral, often mounted on a small artificial plug. Frags have become very popular in recent years as an inexpensive and environmental way of trading and acquiring smaller pieces of the large and sometimes rare or expensive coral colonies available in the hobby.
  • Filtration: There are three main types of filtration used in the aquarium trade – chemical, mechanical and biological. Chemical filtration uses materials like carbon or resins to remove or neutralize chemical compounds on the water. Mechanical filtration physically removes debris and waste using mesh, sponges or other materials. Biological filtration uses bacteria, plants or other living materials to remove waste from the water. A complete filtration system will use all three of these methods in a system. Different types of filters that use some or all three of these methods include power/hang-on filters, wet/dry filters, undergravel filters, canister filters, fluidized beds and others.
  • Hardiness/ Difficulty: Both of these terms are used to describe how easy something is to care for. Their meanings tend to be relative opposites of each other and most places only use one, but they are in fact seperate terms. An item that is “hardy” is generally easy to care for (or hard to kill, dependong on how you look at it). A “difficult” item often has specific needs, a tricky diet or is very delicate. Beginning aquarists should look for a hardy fish with low difficulty. Keep in mind however that hardiness does not always equal easy; research your choices carefully!
  • Kelvin Rating: The “degrees Kelvin” are a way of measuring the temperature of the light, not to be confused with normal temperature of heat as measures in Celcius and Fahrenheit. While the technical terms and measurements of the Kelvin scale can be found in detail marine aquarium publications and on the Internet, the important thing for the average aquarist to know is the higher the number, the more blue the light. (On the good old “ROY G. BIV” rainbow scale, low Kelvin temperatures are on the R side while high temperatures are at the V). Most saltwater and reef aquariums use higher Kelvin lighting than freshwater aquariums.
  • Lighting: The most common types of lighting for aquariums, in order of intensity, are fluorescent, compact fluorescent (also known as power compact), and metal halides with different classifications within each of those types. Actinic is also a type of bulb used and refers to blue lighting with a wavelength of around 420-460nm and is used in saltwater and reef tanks. Always research what lighting would be appropriate for your tank as well as what livestock is appropriate for use with your lighting.
  • Live Rock: Live rock is used in saltwater aquariums as a natural decoration and foundation as well as for the benefits of the organisms growing in an on the rock. It is essentially rock that has been in the oceans for months or even years so that bacteria, algaes, plants, crustaceans, corals and other organisms populate and live on the rock. “Cultured live rock” refers to rock that is either manmade from concrete-like mixtures or is terrestrial rock and is placed in the ocean for a period of time to turn “live”. Live rock is also refered to as “cured” or “uncured”. “Uncured” rock is newly harvested rock that may not be fully cleaned of organisms that do not survive harvesting. “Cured” rock is usually much cleaner and stable and is safer for more established aquariums. Different types of rock are available from different regions, but the main difference between these varieties is simply the region it is harvested from and the shape or density of the rock. Tonga, Fiji, the Solomon Islands and the Caribbean are popular origin regions for live rock.
  • “Reef Safe”/ “Invert Safe”: These two terms can refer to plants and animals or to products like medications. “Reef Safe” items are safe for tanks with polyps and corals while “Invert Safe” is a broader term that includes other animals like crabs, shrimp, anemones, snails and others. While some references use these terms interchangeably, they do not always mean the same thing. For example, hawkfish are generally considered “reef safe” in that they don’t actively eat or damage corals, but they are not “invert safe” since they prey on crustaceans.
  • Starter fish: While these fish are usually very good for beginner aquariusts, the term “starter fish” usually refers to those fish which are considered hardy enough to use to start and cycle an aquarium. The spikes in ammonia, nitrite and nitrate during this cycling process can be dangerous to any livestock, but those typically used as starter fish are more likely to survive this process than others.
  • Tank-raised/ Captive-bred/ Aquacultured: These three terms generally mean the same thing, although “aquacultured” is used more for corals, plants and invertebrates and “tank-raised” and “captive-bred” usually refer more to fish. “Aquaculture” by definition is the growing of freshwater and saltwater organisms under controlled conditions, much like agriculture is the growing of crops on the land. This can range from farms used to grow fish like catfish and tilapia for food production to breeding ornamental fish for the aquarium industry. Tank-raised and captive-bred fish are typically bred on a smaller scale than farms created for the food industry. Some tank-raised fish that are commonly available are fish like clownfish, dottybacks, gobies and some cardinalfish as well as a few freshwater fish like angelfish and discus. Tank-raised fish are often more resistant to aquarium-related diseases than wild-caught fish but can be vulnerable to diseases introduced by their wild-caught counterparts. Strict regulations and pressure on wild fish populations are making captive breeding of fish more common and tank-raised fish more sought-after in the aquarium trade.
  • Territorial/ Aggressive: Some aquarists use these terms interchangeably but they have quite different meanings. “Territorial” fish or invertebrates establish and often actively (and potentially aggressively) defend a particular territory but do not necessarily harm other organisms that do not invade this territory. “Aggressive” fish may show some of the same behavior but do not do so to defend a certain area, but will instead attack and potentially harm any other organisms they may find threatening in a tank. A territorial fish (damsels, cichlids, dottybacks, etc.) can often be safely kept with other tankmates as long as they have enough territory to defend and other fish do not share this area, while tankmates for an aggressive animal (triggers, some cichlids, predators, mantis shrimp) must be chosen very carefully, if kept with any other tankmates at all.
  • Tropical: Almost all plants and animals kept in the aquarium trade are tropical, both freshwater and saltwater. This term refers to their temperature, not their water conditions or where they come from. The tropics are geographically the are between the Tropic of Cancer (23.4º N latitude) and the Tropic of Capricorn (23.4º S latitude). In terms of climate, this usually refers to water temperatures of around 74-82º F, depending on the region. Some notable exceptions are goldfish, koi and a few saltwater fish from temperate regions (the area between the Tropics of Cancer and Capricorn and the Arctic and Antarctic Circles, including the moderate subtropic region). The aquarium fish from these regions have average water temperatures of around 65-72ºF.
  • Water change: A water change as refered to within in the aquarium hobby is when an aquarist removes a portion of their tank water (usually 10-20%, once or twice a month) and replaces it with fresh, clean water. This is done to remove fish waste and to keep water levels appropriate, especially levels like nitrate and phosphate or even to promote breeding in some fish. A water change is not when an aquarist merely tops off a tank to replace water lost through evaporation – only pure water evaporates and salts, waste and other compounds are not removed when the water they are dissolved in evaporates.

Cold Water Aquariums

Oyster Toadfish

Please welcome back Frank Indiviglio for another article.

Today I’d like to introduce you to the maintenance of cold water aquariums, a fascinating but often overlooked branch of aquarium keeping focusing on marine and freshwater fishes and invertebrates from temperate regions.

Exotics Close to Home
Please don’t be misled into equating exotic and interesting creatures with “far-off, tropical places”. Shorelines, ponds, tidal pools and rivers throughout the world’s temperate regions (with the exception of extreme s. Florida, the entire USA is in the temperate zone) yield animals of unimaginable variety and interest. While it is true that many of the most spectacularly colored fishes are found in the warmer parts of the world (their bright colors likely help males and females of the same species recognize each other among the great diversity of similar species in the tropics), breeding males of many temperate fish species, i.e. the sunfishes, do rival those of their tropical counterparts.

Why keep Temperate Fishes and Invertebrates?
Animals from temperate areas offer many advantages to aquarists who live in the USA. Often, our normal seasonal rhythms of temperature and light fluctuation are sufficient to encourage such creatures to exhibit natural behaviors, and even to breed. Also, it is often easier for us to provide a wider range of foods and a more natural environment for them than we can for creatures from faraway places. In some cases, where legal, we may even be able to collect and keep native fishes and invertebrates.

Creating Natural Habitats
If you live near a body of water, try to observe firsthand the environments and habits of a variety of aquatic creatures. You might consider modeling your aquarium after a particular habitat — a tide pool, a weedy, fresh-water pond, or a river bed, for example. Take note of the local substrates, rocks and other natural items and purchase similar ones when setting up your tank prod (collecting natural substrates is risky, due to the possibility of mineral, pesticide or other chemical leaching).

Cold water aquariums are maintained in a similar fashion to tropical aquariums, but we must consider the effects of heat. Many animals from temperate regions are very sensitive to rising water temperatures and to the lower oxygen levels that accompany them. You may, therefore, need to install a chiller to moderate temperatures during the summertime.

Species to Consider
Some of the animals that I have maintained with success in cold water aquariums, and which I plan to cover in future additions to this article, include American eels, fifteen-spined sticklebacks, pygmy and other sunfishes, mantis shrimp, sea stars, Chinese sailfin suckers, weather fish, horseshoe crabs, blue claw crabs, bullheads and madtoms, white clouds, various snails, crayfish and shrimp, giant water bugs and other aquatic insects and many others.

I’ll now give a quick overview of two unusual animals – the oyster toadfish and the spider crab – which are easily maintained in unheated marine aquariums. I’ll cover their husbandry in detail in future articles.

Oyster Toadfish, Opansus tau
This unusual marine fish, ranging down the Eastern Seaboard from Maine to Cuba, seems to cross the line between fish and amphibian – its face even resembles that of a toad. In addition, toadfishes produce sounds audible above the water and certain Asian species can travel overland for considerable distances.

Oyster toadfishes will become quite tame in captivity, and, given a tank of 55 gallons or so, may well breed. Males are ferocious guardians of their eggs, and have been known to stay with nests that are exposed at low tide.

Oyster toadfishes have survived for 15 years in captivity, and will accept nearly any meat-based frozen or pelleted food as well as live shrimp, small fishes and worms. They learn to associate their owners with food, but will bite when handled, and the spines that can inflict painful wounds.

Atlantic Spider Crab, Libinia emarginata
Spider crabs, common yet fascinating if you take the time to know them, are members of a family which includes the Japanese spider crab. With legs spanning 8 feet, these giants awed me when first I observed a large group in a pubic aquarium in Osaka, Japan. American aquariums now exhibit them as well – trust me, they are well worth the trip.

The Atlantic spider crab is a valuable aquarium scavenger, and, using its tiny pointed claws to probe into nooks and crannies, misses little. Younger animals have the endearing habit of jamming algae and vegetation into the crevices of their shells, taking on the appearance of a “walking plant”. They will also nibble at this portable garden from time to time. I have found that they forgo this habit when they reach a carapace size of about 3 inches, although I have yet to discover why.

Spider crabs rarely bother tank-mates and readily consume fish flakes, pellets, blackworms, frozen food fish foods, algae and green leafy vegetables.

In the next installment of this article I’ll write about temperate, fresh water animals that are readily available in the pet trade. Until then, please write in with your questions and comments. Thanks. Until next time, Frank.

Information on the natural history of the oyster toadfish, along with a photo, is available at:

Thanks Frank
Until Next Time,