Shrimps

Marine fish aquariums are almost invariably visually spectacular, but the additional impact created by a “reef” setting, with a variety of invertebrate life, is undeniably immense. Sessile invertebrate life forms may be tastefully arranged to provide a living background made up of many different structures and colours. But the compelling fascination is provided by the mobile animals which make their intermittent appearances from the labyrinth of tunnels and “cavern” niches beneath the background construction. Shrimps are some of the most readily available such creatures, albeit a fairly standard selection. Mixing the different species taken from this selection can mostly be done quite easily, as they are often found together – or in close proximity – in nature.

Cleaner Shrimps (Lysmata amboinensis) are gregarious by nature, and will join together in servicing a willing fish, removing loose mucous or other irritations from the grateful customer. So it follows that the keeping of a small group of these lovely shrimps is usually a simple matter of following their natural instinct. They will take up an area where they can partially conceal themselves, but are able to wave their exposed long white “feelers” to signal their presence and willingness to perform a cleaning service. Fish which are attracted to this display then approach the “cleaning station” and adopt a prone posture, frequently changing colour too. These signs send a message to the shrimps that they are safe to approach and intimately clean them without any threat of harm. The shrimps may then even enter the mouths of predatory fish with impunity to carry out their task, often exiting via the gill openings.

Banded Coral Shrimps, or Boxer Shrimps (Stenopus hispidus) are also frequently available to the fishkeeper. This species is very common, and is circumtropical in its distribution. But they are not gregarious like the above species, and are usually found either as individuals or more commonly as pairs. Where adjacent pairs are found there seems to be a distinct territorial boundary which neither pair will cross – or only at their peril, for this species has large chelipeds which they will use to ward off intruders of the same species. Their bodies are covered with vicious-looking spines, which makes them even more formidable. Given a secure crevice within which they can make their home, Banded Coral Shrimps will usually settle down in the reef aquarium without causing any harm to other occupants. They often prefer to live an upside-down life, clinging to the roof of their home and only coming out the other way up when feeding! Although not as enthusiastic to fastidiously clean fishy clients, this species will sometimes adopt the role as cleaners in nature. They literally feel out their prospective clients with their long antennae, and only make meaningful contact in a cleaning capacity when they feel they have the right response from the fish. If they are in too-close contact with Cleaner Shrimps they may nip off their antennae, so sufficient space should be available before any mixing of the two species is attempted. For safety it is generally better to avoid trying to house more than one matched pair of Banded Coral Shrimps in the same aquarium.

Dancing or Hingebeak Shrimps (various Rhincochinetes species, the most often collected is durbanensis, frequently misnamed as uritai), are another set of species, many of which are gregarious by nature. They are mostly found in quite concentrated groups and enjoy this social behaviour, favouring flat rocky areas within niches or under sheltering overhangs in which to congregate, often assuming an upside-down existence, “dancing on the ceiling”. Mature males may develop impressively huge chelipeds, but seem not to use them in any aggressive way. The extended rostrum, or “beak”, has many spines embellishing its entire length. These charming little shrimps needs to be kept in a social group to get the best results and maximise the enjoyment from them. The ornately striped red and white body and legs of this species makes it a very attractive shrimp for the reef aquarium, and its movements justify the common name of “Dancing Shrimp”, as they seem to skip around on tip-toes with all the grace of professional dancers.

Various species of Saron shrimps are collected for the hobby market from time to time, and some of these can be quite spectacular animals, while others are – by comparison – “ordinary”. The most ornamental specimens may have red or orange star-like markings on the body, an elongated rostrum tipped with bristles – reminiscent of a shaving brush! These same bushy cirri decorate the dorsal strip of the body, and continue down the length of the cellipeds, and along the underside of the abdominal plates. The legs and antennae are red and white hooped. This is a very shy species and will usually take some time to settle into a new environment within a reef aquarium to the point where they will move around and be seen. In addition to this shyness they are nocturnal creatures and initially retain the habit of coming out only after the aquarium lights have been doused. It takes time for them to adjust to both a captive and diurnal existence. A more frequently seen species offered to the aquarium keeper is Saron marmoratus. Although lacking the spectacular bristles which adorn the red species so liberally, maromoratus does adapt to aquarium life more readily, and is a hardy soul. The males of this species grow enormously exaggerated chelipeds, which they seem to manipulate with great success, avoiding falling over themselves with such an apparently cumbersome over-sized set of limbs before them. This is an undemanding species which is easily catered for in aquarium culture.

Given the huge range of species of Anemone Shrimps (Periclimenes species), which are frequently abundant in nature, it is something of a surprise that only relatively few species find their way into the hobby market. The best known is probably Periclimenes brevicarpalis, although this anemone shrimp is far from being the most commonly encountered species on the coral reef. It favours the shorter tentacled anemones, like the “carpet” anemones, and more rarely ends up resident in the popular longer tentacled species, like Heteractis magnifica. It may also be found occasionally in association with certain species of soft corals and some of the less conspicuous anemones which favour a sandy or muddy seabed. Maybe it is the comparative isolation of these species in their desert-like environment which causes the brevicarpalis to make an opportunist home with a host which would not normally be its first choice (?). Certainly it is not essential that this species is given an anemone in aquarium conditions, as it will adapt to life without this natural host. But for best results keeping the shrimp, as well as for aesthetic reasons, the combination of the two is to be preferred.

Another Periclimenes shrimp species which has a specialised host is amboinensis, often known as the Crinoid Shrimp. The banded markings on an elongated body allows this shrimp to live within the protective embrace of a Crinoid, or Feather Star. But it is the amazing ability to match the colour of the Crinoid which affords this shrimp such masterful camouflage. So it is possible to have specimens of this same species in many different colour forms, just as it is with Crinoids. It is a matter of regret that these highly specialised animals are collected from time to time for the aquarium hobby, but without their host crinoid they are totally lost, lacking both shelter and colour matching environment. It could be argued that only in a highly specialised aquarium situation adapted for the successful maintenance of crinoids would it be acceptable to attempt to keep this remarkable shrimp.

The prettily marked tiny shrimp, Thor amboinensis, is sometimes marketed in the UK as a “Sexy Shrimp”, referring to its continuously bobbing up and down tail end! This mini species favours the periphery of an anemone as its chosen territory, spending more time in the area immediately adjacent to the anemone, and far less actually moving around within the tentacles. Sometimes they are found in association with soft corals rather than anemones, and by this means are able to extend the amount of given territories available to them. But this is yet another species which is notably gregarious, with the tiny males usually outnumbering the much larger females. It is far less common to find a solitary pair without another nearby population. The eye stalks are made very prominent by the embellishment of opalescent pearly spots, and the same colouring is found in large saddles which span the thorax of the animal. The theme is continued along the body and into the tail of the Sexy Shrimp. Otherwise the base colouring is often a golden brown, but equally may be a much darker colour. The distribution of this remarkable shrimp is very wide indeed, being found in the Indian Ocean, Pacific Ocean, and Caribbean Sea. This diminutive shrimp is no trouble to feed and has no vices to be wary of. The matter of its small size, however, is something to take into account when planning to keep it in a mixed aquarium.

The very striking and handsome Blood Shrimp (Lysmata debelius) is difficult to spot both on the reef and in the aquarium, as it seems always to prefer a secretive existence, and is often solitary. It is another species which will willingly perform cleaning services, but does not seem to venture out into open situations to do this, but stays mostly within a restricted sheltered niche where most fish would not choose to enter. So a moray eel in its lair, for example, would be a potential client as it could be cleaned within the enclosed security the shrimp prefers. The richly coloured body can be anything from scarlet to a regal maroon. It is the red and pure white legs which are so distinctive in this species. The same pure white is featured in the spots which decorate the thorax and elongated extensions of the otherwise red antennae. This species is neither cheap and nor plentiful, and perhaps this is fortuitous for such an elegant species, helping to maintain its special appeal.

If the aquarium substrate will support the excavations of Alpheid Snapping Shrimps they make fascinating subjects in the co-existing and commensal company of an associated Prawn Goby. (The name “Snapping shrimp” refers to the sharp clicking noise they make with their pincers). But their constant and industrious burrowing is an obvious potential hazard for the essential stability of the aquarium reef structure. In nature they are more often found in open sandy areas, or in sheltered situations without obstacles likely to be undermined by their seemingly incessant excavating activity. The interaction between shrimp and fish is very interesting to observe. The shrimps are almost blind, and certainly cannot see well enough to be aware of impending danger from predators. The goby fish, on the other hand, have excellent vision – enhanced by having their eyes set high up on top of their heads. So while the fish keeps watch at the entrance to the shared burrow, the shrimp busily enlarges the warren of tunnels below by collecting stones and finer debris between its greatly enlarged chelipeds. As it shunts this pile of debris to the entrance the shrimp will make contact with the fish with its forward thrusting antennae, tentatively touching the goby’s tail fin. If all is clear the tail fin remains still and signals to the shrimp that it is safe to complete its task by pushing the debris right out of the burrow to a deposit area adjacent to the entrance. However, if danger is threatened the goby will quiver its tail, urging the shrimp to stay within the shelter of the burrow until the danger is past. When the goby snatches some passing food the shrimp is able to share the feast by catching up any bits that are dropped. One of the most colourful of these interesting snapping shrimps is Alpheus randalli, with red and gold livery.

One of the most ornamental shrimps to be made available to the hobbyist from time to time is the Orchid or Harlequin Shrimp (Hymenocera picta). This colourful, boldly patterned shrimp has disproportionately developed chelipeds and similarly extraordinary mouth extensions. These features have evolved simply to enable the shrimp to access its staple food – the feet of starfish. It is able to manipulate a starfish with the over-sized chelipeds, and eventually turn the unfortunate animal over onto its back. The numerous tube feet are then exposed to provide a meal for the shrimp. The modified mouth parts can then cope with consuming a meal of feet. Regrettably this strange feeding habit renders the beautiful orchid shrimp unsuitable for aquarium culture, unless the keeper has a ready supply of starfish to satisfy this specialised feeding requirement.

Another very spectacular shrimp which comes into the market occasionally is the large Mantis Shrimp (Odontodactylus scyallarus). But once more there are good reasons to think very hard before taking the plunge and acquiring one of these remarkable animals. Handsome thought they are, Mantis Shrimps are powerful predators, stalking a variety of prey creatures at night time. Their presence in a reef tank would be disasterous! The first of the paired front legs are modified to grasp with, while the enlarged second pair are refined into efficient catching equipment, similar to the land based Praying Mantis. These enlarged legs are capable of delivering a powerful “punch” which can stun a passing prey, but also has been known to crack the glass side of an aquarium! Another popular name for the Mantis Shrimp is “Thumb Splitter”, describing the hazard faced by fishermen who remove them from their nets without sufficient care. So, although not difficult to keep, the Mantis Shrimp needs to be kept in a species tank with sufficently thick glass to withstand an assault on it by the sole occupant. So why bother? Well, it has to be acknowledged that this big crustacean is probably the most colourful of all reef animals. It has remarkable spherical eyes, which have two lines forming a division across the centre, and are surrounded by a strong blue “mask”. The tail end is reminiscent of peacock’s feathers, with gleaming metallic greens and reds forming prominent eye spot markings. This colour-scheme is reflected in the colouration of the elaborate head end of the otherwise mainly green body, with reflecting sheens of blue. This lovely shrimp seems to be purely carniverous, willing to accept almost any meaty foods offered.

Another very colourful shrimp with specialised needs for its comfort is the Coleman’s Shrimp (Periclimenes colemani). The colours are variable, but the base colour is usually yellow to orange, overlaid with prominent large spots which can vary from red through to purple. Sounds like a great shrimp to grace the reef aquarium! But this species has a very specialised life-style in nature, and is found – usually in pairs – on the venomous sea urchin Asthenosoma varium. The shrimp carefully removes the feet and venomous spines from a small area of the urchin’s dorsal surface to provide a home base. But they are not restricted to this one area, as they are able to move quite adeptly around the entire urchin, weaving their way between the spines and pedicellaria without coming to any harm. The powerful toxin of the urchin ensures protection from would-be predators for the shrimps. Both urchin and shrimp display strong colours, a show of defiance by revealing their obvious presence on the reef in the sure knowledge that such a display can only be safely made when there is some highly effective protection in place.

The shrimps mentioned in this article are merely the tip of the ice-berg, so to speak. There are very many other species which occur in tropical seas and might well be collected from time to time and offered to the aquarium hobby. There are those which need very careful thought before acquiring them, but there are perhaps many, many more which would be make delightful and easily maintained species for inclusion in the reef aquarium.

The Painted or Cleaner Shrimp is one of the most popular aquarium species. It is a very sociable and elegant creature which is ornamental, but also brings practical services as a fish cleaner with it .

The Banded Coral Shrimp is regularly available to the fishkeeping hobby, and its stylish appearance does much to enhance the reef aquarium. As they are usually found in pairs in nature, it follows that this will be the best way to accommodate them in captivity.

Dancing Shrimps are beautifully marked creatures, which are also colourful and have amusing “jerky” movements. They are gregarious by nature, and do well in social groups. Easy to feed and keep.

Anemone Shrimps are most often viewed from above as they nestle into the protective tentacles of a sea anemone. This unusual profile view shows how glass-clear the body form is, revealing the white internal organs. The very tiny Anemone Shrimp (Thor amboinensis) is prominently marked with beautiful pearly saddles and patches. The specimen pictured is a “large” male, 2 cms. long.

The very tiny Anemone Shrimp (Thor amboinensis) is prominently marked with beautiful pearly saddles and patches.

The Blood Shrimp is one of the most spectacular species to regularly reach the aquarium market. The red colouring is quite variable, but all specimens have the distinctive white spots on the carapace, long white antennae and white tipped legs projecting from a red base.

This Crinoid Shrimp is seen within the protection of the colour-matching arms of a Feather Star. The shrimp pictured matches the crinoid colouring perfectly, and can be yellow, black and white, red and white, or any of many colours crinoids come in!

Some Saron Shrimps are highly ornamental, as is the one seen in this picture. Others may be less colourful and/or lack the array of cilli which this particular un-named species sports to such great effect.

The close association between “Prawn Goby” species and their commensal shrimps is a fascinating feature. The goby is seen here with its tail resting just inside the entrance to the shared burrow, ready to convey messages to the busy snapping shimp whether or not it is safe for it to push its gathering of debris from the burrow. Having got the “go-ahead” the shrimp has dumped the debris and will back into the hole to carry on with its excavations.

This beautiful and highly ornamental Orchid Shrimp has an entirely specialised dietary requirement of live starfish feet for its existence, causing it to be very difficult to maintain in aquarium conditions when a readily available food source is not on hand

The Mantis Shrimp is an incredibly beautiful reef animal. But it is a very powerful and strong carnivore which would wreak havoc in anything other than a specially constructed aquarium environment.

The Toxic Urchin or Coleman’s Shrimp, (Periclimenes colemani) is gorgeously coloured. They are usually found in pairs within the spines of toxic sea urchins. The large female is very obvious in this picture, but look carefully to her right and you can see the smaller male deeper with the poisonous urchin spines.

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