That Fish Blog – Aquarium Advice and Information

Hello, Frank Indiviglio here.  The world’s oceans harbor a great many creatures that produce medically valuable compounds. Sessile marine invertebrates (those which do not move, but rather remain fixed in one location) seem to be particularly valuable in this regard.  In fact, sponges, sea whips, sea squirts and similar animals are the source of most of the invertebrate-derived medicines in use today. 

A review of the pharmaceutically active compounds isolated from sessile marine organisms shows that, while the animals themselves are quite different from one another, their shared lifestyle has fostered similar adaptations – the evolution of powerful chemical secretions.

 Protection for Immobile Animals

Animals which cannot flee from predators must devise alternate means of protection…an arsenal of protective chemicals, for example.  Also, the feeding mode utilized by many sponges and other sessile organisms – filtering seawater – brings not only food but also harmful pathogens and parasites into their bodies.  These are attacked with potent antimicrobial compounds.

 A suitable anchorage (attachment) site is vital to the survival of an invertebrate which is unable to move about.  Competition for such sites can be keen, yet immobile animals are again faced with the dilemma of being unable to physically exclude other animals.  Many have, therefore, evolved secretions that kill other animals. The composition and function of these various chemicals often lends them medicinal value as well.

Medically Important Marine Invertebrates

Sponges, the best studied of the marine invertebrates, and have given us Topsentin, an anti-inflammatory, and Lasonolide, which fights tumors by binding with their DNA. 

Brightly colored sea whips have yielded Pseudoterosin, which reduces swelling and accelerates wound healing.  Also known as gorgonians, several species of these soft corals do well in marine aquariums.

Tunicates, or sea squirts, evolved a primitive backbone, known as a notochord, over 540 million years ago, and are thus the earliest ancestors of modern day vertebrates.  These sac-like filter feeders produce Ecteinascidin,   a compound which blocks DNA transcription.  It is believed that Ecteinascidin may someday find use in treating breast cancer. 

Bryostatin, isolated from colonial marine invertebrates known as bryozoans, or moss animals, forces cancer cells to mature, thereby halting their ability to divide.  

A number of mobile marine invertebrates also produce chemicals that are of interest to medical researchers.  Cone snails, for example, secrete virulent toxins that have yielded the powerful pain killer Ziconotide.  This calcium channel blocker inhibits the relay of neurotransmitters and is used to treat people living with severe chronic pain.

Opportunities for Aquarists and Researchers

So, please don’t ignore the small, immobile creatures in your aquarium and the world’s oceans.  Your observations of their behavior can lead to unexpected and medically important discoveries.  For those of you interested in serious medical research, the world’s marine invertebrates offer unlimited possibilities, and the field is wide open.

Further Reading

The Harbor Branch Oceanographic Institution has posted an overview of some of the exciting work being done with medically useful marine invertebrates at http://www.informaworld.com/smpp/content~content=a713743150~db=all.

Please write in with your questions and comments.  Thanks, until next time, Frank Indiviglio.

Knowing where to start and stop when it comes to writing about invertebrates is a real problem – any single group could keep one occupied for a lifetime. Today I’d like to highlight some interesting facts concerning a few commonly kept types and their relatives. I’ll add to this from time to time.

General
Invertebrates (animals without backbones) account for approximately 97% of the world’s animal species, yet we have no idea of their total numbers. The smallest are invisible to the naked eye while the largest, giant squid, may exceed 60 feet in length.

Nearly every injectable drug manufactured in the USA is tested for bacterial contamination with a chemical extracted from horseshoe crab blood (synthetics do not work as well). Several states are restricting the collection of these animals (often used as fertilizer!) and requiring that they be released after blood specimens are taken.

Invertebrates have colonized every habitat imaginable, from freezing Antarctic seas to the boiling hot water of geysers. The sponges, crabs, tubeworms and others living near deep sea vents form the only animal community that does not rely upon photosynthesis as the basis of the food chain (bacteria that consume methane function as “plants”).

Despite being a creature of legend for centuries, the giant squid, Architeuthis sp., was not captured on film until 2004. Two years later, the same Japanese scientists that filmed the animal caught a specimen on a fishing line, thus giving the world its first view of a living giant squid.

Eating and Being Eaten
Despite radically different appearances, jellyfishes, sea anemones and corals are closely related (Phylum Cnideria). All gather food and excrete wastes through a common opening, and overcome their prey with stinging cells.

Jellyfish, although comprised largely (95%) of water, are able to snare prey as large as small fishes. Surprisingly, they form the bulk of the diet of many huge sea creatures, including the world’s biggest turtle, the leatherback.

The dried krill (shrimp-like creatures of the Class Brachiopoda) that you may use as fish food form the basis of the food chain in most of the world’s oceans. Also, a number of surprisingly large creatures, including whales, manta rays and basking sharks, rely upon krill as their primary diet, consuming billions each day.

Although viewed by most as sluggish creatures, many of the world’s 70,000+ species of snails and slugs (Phylum Mollusca) are quite effective predators. Various types pry open or drill through clam shells and cone snails impale fish by shooting out barbed tongues. Certain sea slugs consume anemones and incorporate the stinging cells into their own gill tufts.

Reproduction
Australia’s Great Barrier Reef, the world’s largest, is 1,250 miles long. Somehow, its untold billions of individual coral animals synchronize reproduction so that the sperm and eggs of all are released into the sea at the same time.

Banded coral shrimps, Stenopus hispidus, form long-term pair bonds, and males have been observed to share food with gravid (pregnant) females. The eggs, which are glued to the females’ swimmerets (feathery structures below her abdomen), are aerated and protected by her. Upon hatching, however, the young may be consumed by both parents!

Surviving
Sea cucumbers make interesting if occasionally unsettling aquarium inhabitants – when disturbed, they discharge their stomachs through the anus! Amazingly, these sea star relatives can regenerate the discarded stomach.

The unique tube feet of sea stars (Phylum Echinodermata) function in locomotion, respiration and as sensory organs. Water-filled canals linking the feet can, via a series of valves, build up enough pressure to enable sea stars to pry open clam shells (try that with your hands!).

The anemone hermit crab, Parurus prideauxi, places a stinging sea anemone on its shell as protection and camouflage and re-locates it when changing shells. The anemone, in turn, gets a safe anchoring place and, perhaps, access to leftovers from the crab’s meals.

Using Invertebrates – Now and Then
Over 10,000 species of sponges (Phylum Porifora) inhabit both fresh and salt water. Several types have been collected from the Mediterranean Sea since ancient times. After drying in the sun, their fibrous structural tissue (spongin) made an excellent bath sponge.

Horseshoe crabs (Phylum Chelicerata) are among the world’s most ancient creatures and have remained relatively unchanged for over 300 million years. Closely related to spiders and not crabs at all, small specimens make interesting additions to a marine aquarium.

And, Finally…An Odd Personal Tale
Octopuses (Class Cephalopoda) are the most intelligent of the invertebrates and make fascinating aquarium subjects. They are also quite well-sighted – one I kept would, according to my grandmother, “stare” at her while she worked in the kitchen. Not wishing to upset my beloved pet, she covered its tank when preparing octopus for dinner!

Well, only a few billion more facts to go! I’ll continue next week, and periodically after that. As there are so many possibilities, I would greatly appreciate your suggestions concerning invertebrate-oriented subjects that you may wish to learn more about. Thanks, until next time, Frank.

You can learn a great deal about invertebrate biology at the web site of the Australian Museum:
http://www.amonline.net.au/invertebrates/ara/index.htm

Sponges are animals? Believe it or don’t. Most of us are familiar with the dried colorless varieties that populate the kitchens and bathrooms of the world, or worse, the cellulose fakers that our children believe dwell in pineapples at the bottom of the ocean. But that’s not what sponges are at all. To me, they are some of the most fascinating and fun sea creatures. Fun? Well, they may not actually do anything, but in the home aquarium, they are “fun” in the aspect that they are beautiful and challenging to keep. They are remarkably adaptive, and if purchased healthy many not only survive in reef tanks, but can grow well and reproduce.

“Sponge” refers to the animals classified in the phylum Porifera; which means loosely “bearer of pores”. The first type of sponges that most aquarists encounter in their aquariums belong to the class Calcarea. These little guys are the tiny little sponges you’ll find in your sump, on the standpipes, and bopping around in the bio-tower or skimmer output. They are about the size of a large grain of rice with a fine, funnel-like extension at one end. They don’t hurt anything, so if you are new at this, don’t be alarmed.

Those sponges most commonly sold in the trade as ornamental sponges belong to the class Demospongiae. They are variable in form and color – from branching blue to orange paddles, to yellow or red balls. Others in this group that are not sold, but most reefers see in their aquarium are amorphous, encrusting species in colors of white, yellow, pink or black.

Sponges are one of the most primitive animals in the sea, yet are far more complex than most hobbyists are aware. All sponges differ from other marine invertebrates in that they have no true tissues or organs. Their structure is made up of silica based spicules and/or collagenous spongin. Most sponges are constant filter feeders with little need for lighting. To feed, sponges pump an incredible amount of water through their bodies. The uni-directional flow allows the sponge to absorb fine food particles (most not larger than 1.5 micron!) and release wastes back into the water column. It’s nutrition by diffusion, Cool Thing #1! As the sponge grows, it will modify its surface and cavities to optimize the water flow around and through it. For this reason, once a sponge settles in a spot in your aquarium, it is best not to move it.

Not all sponges are obligate filter feeders. There is a group of calcareous sponges, like my current favorite, the blue finger sponge, which are moderately photosynthetic (due to symbiotic cyanobacteria) as well as filter feeders. Use high light, high water flow, and don’t forget your calcium!

A note about purchasing sponges; Do not ever EVER remove them from the water. If you remove them, air bubbles become trapped in the body cavities and there is no way to purge the air so those cells will die. When buying, look for uniformity, no transparent or fuzzy spots. Don’t buy sponges with necrotic tissue, unless you are brave and willing to eat the cost, as many retailers will not guarantee sponges. If the sponge is new, and it was exposed in shipping, it may not show dead tissue for a while. If after a few days you see some of your new sponge dying, just cut off the bad spot. Sponges have remarkable regenerative abilities due to Cool Thing #2: Totipotent Cells. Think Stem Cells. These cells can revert to any type of cell needed to ensure the regeneration of the sponge.

I feel I should include Cool Thing #3 even though it’s not really related to the hobby but it’s cool nonetheless: Sponges are one of the most chemically rich resources identified to date. They’re packed full of biochemicals that are currently the basis of the majority of new pharmaceutical research. Products from anti-inflamitories to anti-cancer agents have been derived from sponges. But that’s a different blog.
I hope I’ve manage to convince you of the hidden charm and FUN of poriferans, and I encourage aquarists who want to attempt keeping sponges to research them further and to go ahead and try them out!