What Is An Invertebrate?

To avoid becoming a squishy heap on the ground humans have a skeleton. Quite a good invention really, not having a skeleton would cause quite a few difficult problems.

Humans aren’t alone with the possession of a skeleton of course; there are all sorts of life forms that have one too, how about the elephant or man’s best friend the dog as just two examples.

Skeletons are not essential to life however; there are creatures that don’t use one at all. As a non-scientist I can say that they use a different method to maintain their body shape, I’m not sure how a scientist would put it. For example a shrimp has a hard outer shell rather than an inner skeleton.

Vertebrates, those that have a skeleton, are vastly outnumbered in the world. It is estimated that vertebrates are around 3% of the life forms in the world. It follows that a massive 97% (I just had to demonstrate my mathematical abilities) are invertebrates.

There are land dwelling insects such as spiders and worms, examples of well known invertebrates. In the cold sea there are huge numbers of plankton, anemones, sponges etc. The warm seas contain many better known (to the marine aquarist) invertebrate species, including filter feeding worms, shrimps, corals and sometimes very large anemones. It is with some anemones of course that the representatives of the vertebrate/invertebrate world have combined forces to mutual advantage; these are the clown fish with their selected hosts. There are other examples of this life style.

Invertebrates are very adaptable as demonstrated by the discovery of volcanic activity deep in the sea well beyond the sun’s light. Scientists used to accept that life basically depends on the availability of light from the sun, an example of which is that plant life uses the sun’s light to photosynthesize and grow, and then the plant life is eaten by a herbivore from which energy is obtained. Herbivores are then the prey for carnivores. They all basically depend on the plants and the sun. This belief has been changed by the life found near this deep volcanic activity, including filter feeding worms, mollusks, bacteria and crabs which depend not on the sun’s light but on heat and chemicals.*

Anyway marine aquarists, or rather those who maintain a reef system, keep various types of invertebrate including shrimps, corals, sponges, anemones, filter feeding worms etc. These very interesting life forms only ask for a few things for success, including high quality seawater, for the majority of corals and some others sufficient light of the correct spectrum, space to grow and freedom from predation. It is usually important to place for example corals in a position where they receive sufficient seawater flow.

It is worthwhile noting that all marine aquariums, big or small, fish only or reef, depend on invertebrates for their health and life. The bio-filtration system, whether this is live rock or canister filters, contains bacteria that deal with the toxins ammonia and nitrite. Without these bacteria the life in the aquarium would die. With live rock, further bacteria should be able to deal with the sometimes troublesome nitrate.

Those aquarists who make use of natural live rock could discover that they have invertebrate life forms in their aquariums that they didn’t import themselves or at least not intentionally. Some such as filter feeding worms could be welcome. Others such as the Aiptasia anemone are not welcome. The Mantis shrimp is another, though in this case it is worth keeping but needs re-housing to an area where problems won’t arise.

Invertebrates provide the aquarist with a chance to create a living reef at home, be this large or small, though compared to Mother Nature’s creations all home reefs are miniscule. Nevertheless, a successful home reef is wonderful to see.

(* Reference: Marine Invertebrates. Martyn Haywood & Sue Wells)

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How About An Apple?

Most marine aquarists are only too happy to have something different in their aquariums, as long as that something fits in with the current population.

The apple being talked of here is the Sea Apple which is definitely different! As can be seen it’s colourful too. An aquarist who has one will usually be fascinated by ‘the thing in the corner’. The Sea Apple has been available to aquarists for many years. I feel that the beginner aquarist should let experience build before keeping one, as a pure guess say about a year, or at least until the common general husbandry mistakes are no longer made and seawater quality is consistently high. This is important as will be seen.

‘Sea Apple’ is the common name; the proper one is Pseudocolochirus axiologus. They need the usual correct introduction to the aquarium, that is, acclimatization, and should not be exposed to air. They need to be handled gently but this of course is the same for all livestock.

The Sea Apple does not require reef lighting as it is not a coral but a species of sea cucumber. This can of course be confusing, the common name talks of ‘apple’ yet the species is ‘cucumber’. (This seems to happen from time to time, such as the Foxface fish (Lo vulpinus) that belongs to the rabbitfish family.) The Sea Apple is usually able to grow to about 4″ (circa 10cm) though there are larger species that grow to about 6″ (circa 15.25cm) or more though these are not so readily available and are more expensive.

The Sea Apple is able to move slowly around the aquarium and will do so until it is happy with its position, and this depends a lot on seawater flow. The flow doesn’t need to be very strong but moderate to brisk. This is because from the top centre a crown of feathery tentacles will appear and too strong a flow could cause problems. As said, the Sea Apple will make its choice and the final place could be a viewing glass, a corner, a rock or even the tube from a tubeworm. The aquarist has his or her preference for position, so keep those fingers crossed. The final position is likely to be between half way and the top of the aquarium. Once the Sea Apple has come to rest it should be left in peace unless the position is causing trouble to other livestock or presents a danger to the Sea Apple itself. It should not be irritated by the aquarist; this could be a real problem as will be seen.

The tentacles are used for feeding and are extended into the seawater column for this purpose. Fine particulate matter is captured and, one by one, the tentacles are passed into the mouth for removal of any food and then withdrawn, it’s a bit like a human sucking food off the fingers. This is a fairly slow process and is fascinating to observe.

The Sea Apple is quite hardy in a high quality environment and can live a long time. Many do fail though and this is to do with feeding, or rather the lack of it. In most aquariums there is insufficient suitable fine particulate matter in the seawater and therefore the Sea Apple doesn’t get enough to eat. This causes it to slowly shrink until it dies. Target feeding is needed, the frequency of which is best twice a day or more if the need is observed. There are plenty of commercial fine foods available that are suitable. All that is needed is for this food to be squirted into the seawater with a suitable instrument a little upstream from the Sea Apple when it has the tentacles extended, the food will then drift over them. If the seawater current is too high causing the food to pass too quickly, turning off the pumps for a short period will not do any harm. Any of the fine food that is not taken will drift off and could well be captured by corals.

Overall I would suggest that a reef system is the best aquarium for the Sea Apple to be introduced into. The reason is that there is a greater likelihood that there will not be any fish present that could nip at the tentacles, though this is not always the case. If the Sea Apple is excessively harassed then serious trouble could occur.

The problem that a Sea Apple could cause is very serious. If it is excessively harassed and stressed a toxin could be released that could, and likely will, kill the other livestock. Not a pleasant thought. That is why the Sea Apple should not be harassed excessively by the aquarist and its tank mates should be suitable. In addition it would be a good cautionary measure to protect the intakes of circulation pumps etc so that the Sea Apple cannot be accidentally damaged, this should be done before introduction.

Having said that, the Sea Apple should be a good introduction to a suitable high quality environment provided the aquarist has reasonable experience and feeding is given suitable attention.

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The Rose Anemone

One of the most intriguing sights within a marine aquarium is an anemone with a clownfish or two. The clown fish on its own, particularly certain types such as the common clown fish (Amphiprion ocellaris), could be the flag for marines. Seeing a clownfish dwelling among the stinging tentacles of an anemone adds to it. It should be mentioned that clownfish have anemone preferences, and a check should be made if a clownfish is to be offered an anemone as home.

While in cautionary mode, it should be noted that anemones are not for novices, it is necessary that experience is gained first, experience in maintaining high quality seawater and equally high quality general habitat. In addition, anemones such as the one looked at here require correct lighting, in the same way that most commonly kept corals do. This is because of the presence of zooxanthellae, single celled symbiotic algae within the flesh. The zooxanthellae give the anemone its colours.

The Rose Anemone is properly called Entacmaea quadricolor. Looking at the proper name it is clear why it is also commonly known as the four coloured anemone. It can also be recognized as a short part of the tentacles are bulbous, this occurs towards the ends. Remembering that some clownfish refuse for some reason to take up home in an anemone even though it is of the correct type, the Rose Anemone should be acceptable to Amphiprion bicinctus, A. clarki, A. ephippium, and A. frenatus. That’s quite a choice, but as said there’s no guarantee.

Some symbiotic anemones will anchor themselves in the substrata which can sometimes present a positioning problem for the aquarist. The Rose Anemone however doesn’t require substrata, it is happy on rocks. Well, that isn’t completely correct, it is happy between rocks in a fairly deep cleft, which is best smooth, meaning smooth sides and bottom. The anemone is able to contract considerably into the cleft if threatened. They should not be in the direct flow from any powerhead or the like, the seawater flow is preferred to be gentle. In a reef system positioning would need some thought because of the high seawater flow, and at the same time remembering the anemone’s light requirements.

Having mentioned the anemone’s preferences, it would seem that this particular one is fussy. However, it is reported to be one of the easiest, or perhaps the easiest anemone to keep among the symbiotic types (symbiotic = anemone/clownfish).

There is one potential habit with this anemone that some aquarists face and others not – it can without apparent reason go wandering. Even though the anemone has been provided with all necessary requirements to settle, it could go for a walk which is not going to necessarily please the aquarist. It could end up a very short distance away from where it was placed, or it could end up down the back of rocks hardly on view and the like. Or it could stay exactly where put!

If the anemone does move to a position unacceptable to the aquarist it could be transferred to a new area which again is designed to meet all its needs. Care has to be taken, as the anemone could well be well fastened to a rock and clumsy attempts to release it could cause damage and affect its health. If at all possible, if the anemone is fastened to a rock, the rock should be moved to a new area with the anemone and be used in the construction of the new cleft. With a prayer for good luck maybe the anemone will stay put.

Feeding the anemone is easy, all that is required is a smallish piece of mussel, lancefish or the like. Once or twice a week the food is placed on the tentacles, and the anemone will transport it to the mouth. If a clownfish is present it is possible that the food will become of immediate interest and it may not reach the mouth, so this needs to be watched for.

The anemone could reach a diameter of 20 inches (circa 50.75 cm) though this is unlikely in an aquarium. Having said that, I once kept a symbiotic anemone of a different type that grew so large it had to go back to the local fish shop. Sadly, the clownfish also went with it.

As said, symbiotic anemones are not for the inexperienced. If including one in the display is being considered, then this one is reported to be a little ‘easier’. Watch out for walkabouts though!

The link provides some pictures.

http://www.poppe-images.com/images/search_results.php?keyword_mh=Entacmaea+quadricolor&x=54&y=12

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Sea Hares

Many reef aquarists who have some experience in maintaining their aquariums that is maintaining seawater quality at a high level are constantly on the lookout for something that could fall into the category of ‘unusual’.

The life form that is found – if found – has to meet certain criteria in the aquarist’s mind before it receives the sea of approval. First and foremost, it has to be reef safe, in other words it must not start eating the aquarist’s coral collection! Second, it has to contribute something to the reef, this contribution could be beauty, or shape, or a combination. Or it could be just weird.

A life form that is not only interesting, could probably be called beautiful, and in addition is useful to the aquarist is the sea hare. These are often termed ‘slugs’ but this is a little unfair, as the word ‘slug’ could initiate thoughts of the gardening problem slug which eats if it has the chance much of the garden plants. Sea hares don’t deserve this kind of press. They will actively consume algae in the aquarium. The aquarist with a green hair algae problem would no doubt be delighted, but it is possible the creatures would also find decorative algae a pleasant food.

Sea hares are sometimes obtainable from the local fish shop, or if not can usually be found for sale wider afield. They are also being commercially bred too, which is a great boon. Its wonderful how many sea creatures, on a lengthening list, are now being bred.

The aquarist if intending to buy one of these creatures has to show some caution, but no more than when buying a fish. It is important to know the species that is being obtained; this information should be readily obtainable from the seller. If it isn’t, then don’t buy.

Why should caution be necessary? When buying a fish it is necessary to know the species so that the eventual size is known. Many fish are small when at the dealers but grow quite rapidly if nature intended them to do so.

Similarly, sea hares have different sizes. For example, one type which is of no interest to the aquarist is reported to grow to 39.5 inches (circa 100 cm), just a bit large for our aquariums! Another, the spotted sea hare (Aplysia californica) could grow to about 15 inches (circa 38 cm). Another much smaller species commonly called the green sea hare (Phyllaplysia taylori) could grow to between ¾ inch (circa 2 cm) and 3 inches (circa 7.5 cm). The spotted sea hare will usually eat good quantities of algae, the preference being for green. The corals that that the sea hare is living with need to be fairly robust and well anchored, particularly as the hare’s size increases. The smaller hare is not such an easy feeder, as it lives in sea grass ‘fields’, the sea grass is its reported food. They are reported to eat algae but this could prove to be inadequate. Also, predators in the aquarium could take an unhealthy interest in the creature.

Sea hares do not have any particular demands apart from the usual one of good seawater quality. If the aquarist is cautious in purchase and is able to provide the food required, then the aquarium will be enriched with a creature that some would call beautiful, others different, and others weird.

There is one link provided and a video. The link is to an advanced website, but this should not put any reader off as the text is straightforward. Just scroll down until the sections that are of interest are found. The video shows a sea hare in an aquarium. Note the camouflage.

http://www.advancedaquarist.com/issues/oct2004/invert.htm

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Clams

Those who keep a mixed reef or corals only type are the only aquarists who would be interested in clams, or at least in the clams that are being looked at here, which are in the family Tridacnidae. This includes some of the giant species from which stories of divers being trapped have been born, the stories no doubt being unsupported by fact. Not all of them have the potential to be giants, there are those that are much more aquarium sized.

The link shows some of these clams: http://www.poppe-images.com/images/search_results.php?keyword_mh=tridacna&x=73&y=11

Even if the aquarium system owned is a reef the successful keeping of these clams depends on adequate lighting, for within the flesh are zooxanthellae, the same single celled algae that reside within the flesh of most of the corals commonly kept. All reef aquariums do not have the required lighting, some use banks of fluorescent tubes. Unless the clam placement is very high on the reef this light is likely to be inadequate, and even if placed high the light could be insufficient. Insufficient light will prove to be fatal, and the sign for this is a brown coloured mantle. Once this has occurred then the clam is normally doomed and placing it under intense light in the hope of saving it is likely to fail. The best lighting for clams is properly powered (that is sufficient wattage) metal halide which can penetrate the seawater reasonably.

Placing a clam high on the reef in the hope of sufficient light has a downside in addition to the possibility there still won’t be enough light. This downside is seawater movement as the clams prefer this to be very moderate to weak. The seawater movement in an SPS reef is high and a soft coral reef is more than the preference of the clams. So at least an area where the clam is protected from high movement is required. In adequately lit aquariums (adequately meaning the lighting has sufficient power to penetrate sufficiently to the bottom) the clams should do well placed low down on the sand.

Despite the absolute necessity for adequate light the clams are easy in one respect and that is feeding. They are filter feeders, but the products of their zooxanthellae are sufficient to meet their requirements, which mean that the aquarist doesn’t need to worry about additional feeding. Any food that is placed in the aquarium that is suitable for filter feeders is likely to be useful to the clams as well.

There are three clams that are probably most of interest to the reef aquarist, and these are Tridacna crocea which grows to about 5 inches (circa 12.5 cm), Tridacna gigas which could grow to about 50 inches (circa 127 cm), and Tridacna maxima which could grow to about 14 inches (circa 35.5 cm). It would seem that the only two suitable to the aquarist are Tridacna crocea and Tridacna maxima, but all three are obtainable if searched for. If Tridacna gigas begins to become too large it could be moved very carefully to more suitable accommodation. It takes a long time to reach a large size.

The attraction for aquarists with these clams is their beautifully marked mantles. When healthy and fully open they are extremely attractive and automatically draw the eye.

If the aquarist has suitable accommodation, that is a reef aquarium with suitably powerful lighting, and also some experience has been gained the purchase of these clams is a very worthwhile consideration. (Experience means that high quality seawater can be maintained and the aquarist has an understanding of aquarium husbandry). They provide a very ‘reefy’ looking life form for the captive reef and one that has gorgeous colours when open. In addition feeding is not a problem so seawater quality will not be potentially downgraded.

Tridacna clams are now being commercially produced and if at all possible these should be the ones purchased, even though their size may be fairly small.

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What Is A Marine Invertebrate?

Invertebrates are very important to marine aquarists, particularly those that own a reef system.

The word invertebrate covers all those organisms that have neither an internal skeleton nor a backbone. They live on land and in the seas.

There are around 2,000,000 different species on the planet and in the region of 97% of these are invertebrates*. Invertebrates that live on dry land include those that are well known to us such as worms that are often dug up by the gardener and spiders who weave there webs in many places.

Common examples of marine invertebrates include well known life forms often kept in aquariums such as shrimps, crabs, anemones, worms and sponges. In the seas and oceans the invertebrate is everywhere, not only on the wild reefs in warm areas but in cold and very cold areas as well. These invertebrates can be minute to very large.

Invertebrates that have a hard exterior shell, such as the very popular shrimps, have a ready made defence somewhat like a knight of old. It gives a level of protection against predators. The battle between predator and prey is ongoing, and defences need to be updated (over very long periods) as the predators adapt to overcome the defence strategy.

It would seem that hard-shelled invertebrates have developed an excellent defensive system without many drawbacks. The defence is not totally adequate because of the constant danger from predators as mentioned, and there is another major disadvantage. Living things need to grow, and the hard skeleton of, for example, a shrimp is fixed in size. So there is only one way that the shrimp can obtain the room to grow, and that is to get rid of the current shell. This is done fairly regularly and once the old shell has been abandoned there is a new one of larger size beneath. Unfortunately the new exoskeleton is soft and time is required for it to harden. During the hardening period the shrimp is extra vulnerable and needs to hide away in a secure spot until hardening is complete.

In order to produce a good exoskeleton the shrimp (just to use the example above) needs to draw on the seawater for some materials. Fortunately, they should be available in reef aquariums where the aquarist is already maintaining adequate calcium and other levels, and a problem shouldn’t arise.

Finding the abandoned skeleton of a shrimp shows how remarkable the process of creating a new exoskeleton is, for the abandoned one has all the details of a living shrimp. This includes the long thin antennae and legs. The abandoned exoskeleton can appear a bit ‘floppy’ though which gives the game away.

I remember keeping an aquarium years ago that among other things contained a large anemone and a clownfish. A cleaner shrimp was also resident. One morning I approached the aquarium and was horrified to see that the anemone had apparently got the shrimp. It was amongst the tentacles, perfect but lifeless. I was quite irritated even though I knew that the anemone had predatory abilities. I visually searched the aquarium and there wasn’t a sign of a shrimp, and was actually debating whether to obtain another. Later, as I came to the aquarium to supply food, there was the shrimp sitting on its normal rock. I did end up getting another so that the original had a ‘friend’, they are better off with more than one.

Just out of interest, science thought that sunlight is necessary to all life forms but has had to amend that view. As has been shown on television, very deep in the sea beyond light penetration there are a few small areas of mild volcanic activity. They produce ‘chimneys’ from where the volcanic output escapes, not lava but a stream of heat and minute debris that looks like smoke. Living near these ‘chimneys’ are crabs, filter feeding worms, shrimps and sponges. They have adapted to the alien world so far from the surface and have no requirement for sunlight. The sun’s energy is replaced by the emitted heat and chemicals.

If the aquarium is suitable (this really means a captive reef though a fish only system is suitable dependant on seawater quality, fish inmates and the aquascaping), invertebrates make excellent interesting inhabitants. Many such as cleaner shrimps are commonly available. They usually require very careful acclimatization to the home aquarium seawater and must not be exposed to air.

(*Reference: Marine Invertebrates. Martyn Haywood & Sue Wells)

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The Cleaner Shrimp

One of the great advantages of running a marine system is the different types of livestock that could be housed. The diversity in the aquarium will never equal or come near that on the wild reef, but there is enough to create a great deal of interest.

In addition to various types of fish, there are snails, crabs and shrimps. The aquarist has to be sure any of these additions are safe – ‘safe’ in this instance means they will not damage or eat other livestock, and in turn other livestock will not damage or eat them. For instance, some crabs are not welcome as they blunder about the aquarium and knock things over or even attack and damage corals, and similarly some shrimps are not welcome in an aquarium with starfish as they will attack and eat them. Likewise a shrimp placed in an aquarium with certain fish is in great danger of being consumed. However, many snails are of use in the control of algae and some hermit crabs can be of use as general housekeepers.

There is a shrimp that is very often the first ‘diversion’ from fish that a fairly new aquarist with a reef aquarium will be attracted to and this is the cleaner shrimp, properly named Lysmata amboinensis. Have a look at the shrimp via the link:

http://www.oceanlight.com/lightbox.php?sp=Lysmata_amboinensis

It is commonly called the cleaner shrimp because of its fish cleaning actions on the wild reef. The shrimp, with a number of its namesakes, set up a cleaning station on the reef which becomes well known to many fish of all sorts. The fish will even patiently wait their turn if the cleaners are busy. These fish come to the cleaning station so that the shrimps can remove parasites, growths, loose scales and other irritants from the fish’s surface. The little shrimps even go inside the gills and mouth of the fish with the fish ‘opening wide’ to permit this. It would be a quick snack for the fish but presumably they recognize the shrimp from its markings and movements and let it be. I read of an experiment on a wild reef where cleaner stations were removed from a specific quite large area and the incidence of problems such as fish disease increased. When the cleaner stations were re-introduced the problems diminished.

If the shrimps are to be introduced to the home aquarium it is important that they are acclimatized properly. This means that seawater in the transport container is reduced by half and seawater from the aquarium is dripped into the container using an air line and air line clamp. The drips should be a little short of a continuous stream and the container allowed to fill to its previous level. Some aquarists then repeat the process. The shrimp should not be exposed to the air. They settle in quickly. It goes without saying that the aquarist must be sure there is nothing already in the aquarium that could threaten the welfare of the shrimp. The shrimps can be kept as a group if required.

The shrimps soon become a favourite pet as they quickly respond to the presence of the aquarist – expecting food no doubt – and will climb on the aquarist’s hand if this is in the aquarium. They probably see the hand as a fish and proceed to move about on it looking for food. Feeding them is easy as they will accept directly offered small pieces of de-frozen food such as lance fish and mussel etc. They will even attempt to capture pieces of flake food and can learn to be quite successful.

In the aquarium they may attempt to clean fish as they would on the reef but this may be an irritant to the fish. In the aquarium the fish cannot move away from the ‘cleaning station’ but usually they move away far enough and trouble does not arise.

The shrimp is ‘reef safe’ and the reef system is the place for it to be housed. Being in a reef system also allows the shrimp to molt securely. Molting is when the shrimp casts off the old exoskeleton and hardens off a new one. This occurs as the exoskeleton does not grow so the shrimp from time to time needs a larger one. If a ‘dead’ shrimp appears it could well be the result of molting.

The cleaner shrimp described is not the only one as there is another that is very similar in appearance. This one is properly called Lysmata grabhami. It displays the same colour pattern except that the white marks on the ‘tail’ are missing – the white line that runs down the top and centre of the body extends to the end of the ‘tail’.

Once established in the aquarium, which does not normally present any problems, the little shrimps are super. Not only are they colourful and a contrast to fish, they are very likeable because of their amusing and friendly antics.

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