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Too many people envision the reefs of the world to
be some aquatic equivalent of "Bambi crossing a meadow" with
some sort of miraculous "balance" amongst the life that
occurs there. This is a dangerous precept for aquarists, as these areas
are veritable battle zones with the life competing for space, food,
mates... at a "tooth and claw" level. Most all benthic life
we keep continues with this behavior in captivity. Overgrowing,
shading, poisoning, stinging, eating its neighbors... Sometimes at
great distances. Herein will be my statements re approaches to
alleviate the major thrusts of this issue with stinging-celled life...
All out competition is an omnipresent situation in captive reefs.
Proper set-up... Starting with smaller specimens, rinsing them,
quarantine, placing the less noxious to more in order, careful
maintenance... and observation are all useful tools
here. Intro.
Looking at most television and other media presentations re the worlds
reefs, one gets the notion that these are places of pastoral perfection
With static stands of dominant inplaced/attached life and shoals of
colorful fishes passing by. This is a far cry from the truth, as most
reef aquarists can attest. In fact, just thinking about what one sees
on tropical shallows should cause a thinking person to wonder Just why
is there so much polypoid life here? Does it make sense that predators
wouldnt consume such ready fare? Looking a bit closer, one can clearly
make out demilitarized zones between various specimens and with a bit
more cursory examination, that there are definite patterns in the
abundance, distribution and proximity of one organism type and its
relation to others.
These facts are of use, importance to home hobbyists, as obviously all
Cnidarian life has mechanisms for extending itself in space and time to
the detriment of others near it. Various tools are used as we will see
to outcompete neighbours for space, light and food and to prevent them
in turn from outright being killed. Various
Competitive Means:
There are a few ways to classify the mechanisms used by Cnidarians to
attain and retain their piece of paradise on reefs. Here is mine.
n
Growth Means Overshadowing Overgrowing Physically blocking n
Physical Means
Digestive Dominance
Stinging Mechanisms
Proximal: Nematocysts/Cnidocysts
More Distal & Specialized: Acrorhagi
Most Distal: Sweeper Tentacles n
Chemical Allelopathy
Toxins produced that are deleterious to cnidarians, other
invertebrates, often fishes and even algae. Competitive Means Details:
Growth
Means: Overshadowing/Shading:
This
is a principal strategy of the more fast-growing, reef-building
families of stony corals, the Acroporids, Pocilloporids and some
Poritids. Simply growing faster, taller, overhanging and crowding out
other life forms below and aside their colonies to deprive them of
light and settling foods.
Growth
Means: Overgrowing: Faster growing, more dominant by way of being more
noxious or better stinging species can overcome and even possibly
derive nutrition from slower growing, less noxious, less stinging ones
that lose to them. This phenomenon is especially common among
stoloniferans (polyps to hobbyists) and gorgonians (sea fans).
Blocking:
Though the contestants may not be chemically challenging to each other,
simple proximal exclusion can deprive other life of light, current,
foods, waste-dilution
Physical
Means: Digestive Dominance: Some Cnidarian groups can use their tentacles and
extend other feeding structures through their body wall (mesenterial
filaments) whose cnidocytes contain digestive elements. Some
stinging-celled organisms can egest (throw up) buccal pellets,
digesting near competitors.
Stinging
Means: Proximal:
Nematocysts/Cnidocysts are cellularly derived structures that are
everted (turned inside out) given chemical (smell) and physical
(pressure) clues with either barbed ends of various sorts or
agglutinant (sticky) processes. These can be shot out with extreme
speed and pressure penetrating even a thickened skin Some are VERY
sticky, others are EXTREMELY toxic. And theyre the gift that keeps on
giving; can continue to sting, agglutinate off-animal, at much later
times as part of released mucus that can sting, poison other life.
Theyre especially prevalent in hard and soft corals and
anemones. More
Distal Stinging Mechanisms: Acrorhagi:
This
structural defense is widespread amongst coldwater Anemones, and found
in some hard and soft coral groups. The actual stinging structures are
called holotrichs, mastigophores. Even
More Distal Stinging Mechanisms: Sweeper
Tentacles:
This
is the most common occurrence and source of trouble with stony coral
keepers but sweeper tentacles also occur in soft corals, other Classes.
Their mode of action appears as burning of adjoining species,
different genotypes of the same species. Occur in response and in the
direction of strangers. And sweepers can break off keep stinging,
digesting. The size of species, polyps is no indication of
the length of sweepers, nor most importantly, the number of cnidocysts
For example, even one inch Oculinds (Galaxeas) have sweepers of up to
12 length. Caryophylliids/Euphylliids very common as well. hierarchy of
stinginess can be arranged with species of the genera Fungia, Galaxea,
Goniopora being high, Lobophyllia being intermediate and Montiporas
being low.
Chemical
Allelopathy: Poisoning Others: Mostly gorgonians and soft corals, but about half
of cnidarians produce allelopathic compounds in some quantity; some of
their effects are profound, especially in aquariums vs. wild settings,
where concentrations can be orders of magnitude higher due to a lack of
dilution. Can be lethal to other livestock, including fishes and algae;
however, the effects, degrees of toxicity are species to species
specific and variable. Allelopathogens are used for more than
offense/defense. They also serve to shed/avoid space and metabolic
parasites. Chemically, theyre mainly 'terpenoid' and
'sarcophine' <a class of Terpenes> compounds, but there
are many others. Higher reduction-oxidation potential (e.g. the
use of Ozone) is useful in destruction of these materials.
Some of the greatest volume
producers:
Practical
Matters: What Aquarists Can and Should Do (or at least be aware
of)
Signs/Symptoms of Overt Aggression/Poisoning
Prevention:
Treatment for Effects
Recognize the Signs/Symptoms of Overt
Aggression/Poisoning: For stinging-celled
life:
For fishes: Rapid or slowed breathing and movement
death. For algae: Bleached appearance, especially in direction of
cnidarians. Slimy dissolution. Means of Prevention: Selection, Acclimation
& Quarantine:
The
best methods of treating these issues of negative interaction is
obviously to avoid them altogether. Though not entirely possible, nor
even practical, the following are valuable to prevent extreme
reactions. Selection: Look for the best in
apparently healthy specimens; these are less likely to over-react in
the presence of established Cnidarian life in your syste Acclimation of New Specimens: Is
best done in a plastic tray best, rinsing specimen/s individually, with
clean, system water, and discarding mixed water.
Quarantining: For a week or
two allows you time to examine for new specimens for health, possible
undesirable hitchhikers, and allows them to rest, shed slime, stinging
cells, wastes...
Space: For dilution and spacing specimens,
providing varied habitats: The bigger the system/volume the better.
The larger the system, the more stable and the more hodge-podge and
even crowded an assortment can be. Wastes are diluted and specimens can
be more widely spaced initially, giving them more time/space to grow,
time to undergo classical habituation (to ignore each other).
Careful stocking plan: Species selection,
placement, order: STUDY! Only through careful studying, reading,
conferring with other reefers assemble a working assortment.
Buy/Procure captive-produced stocks they do get along better. Provide
adequate initial, stinging, expansion and growth space between
specimens. Go slowly often cnidarians get used to each other over time.
Keep your system in dynamic equilibrium through regular monitoring and
maintenance.
Securing, sequestering of individuals,
colonies: Falling of specimens into each other or not must be
avoided by strapping, gluing, wedging, isolating in place ON/IN a
stable setting. Place rock, other structure on bottom of tank; larger,
flatter pieces first. Drill, tie, anchor structure together if
necessary.
Adequate feeding, lighting/regimens,
circulation All cnidarians need to be fed even principally
photosynthetic species/groups. Nutrition can be provided purposely or
indirectly via refugium culture, ancillary feeding of other stocks, or
biochemically. For most set-ups, mixes of livestock, lighting
should be consistent. Light systems should be on timers, cycled on/off
regularly. Circulation should be vigorous and non-laminar. On
the plus side of poor water movement is the lack of chemical
communication and distribution of chemical and physical materials. On
the plus side of high water movement are export of same, distribution
of foods, oxygen, elimination of wastes, carbon dioxide, provision of
steady pH, RedOx, Biominerals
Biological, Physical and Chemical filtration,
augmentation, efficient skimming The more complex the make-up of the system,
incorporating live elements, ozone/high/er ReDox, mud, reasonable
levels of biominerals and alkalinity on a steady basis the better. This
is accomplished with the use of refugium/s, macroalgae culture, DSBs, a
regular routine of established
maintenance.
Not Cnidarians Alone: Other Phyla: A Bit More
Fuel on the Fire Cnidarians arent (by far) the only organisms with
competitive mechanisms on/in reefs All animal, algal, plant and
micro-organism groups have varied means of avoiding predation, securing
space, other resources Some are much more potent than stinging-celled
animals e.g. Sponges, BGA About the best one can do is again set up a
good-sized system properly, stock it appropriately, maintain it
adequately and remember the oxymoron dynamic equilibrium in keeping it
so.
Cloze: Overall
Considerations n At times
Extreme Competition in the wild is mirrored in various fashions and
degrees in captive systems. n Much overt
aggression and poisoning amongst cnidarians and their tankmates can be
prevented, ameliorated by:
n Evidence of
Negative Interaction, Suggested Reactions
Selected Biblio.
Ates, R. 1989. "Aggressive behavior in
corals". Freshwater and Marine Aquarium 12(8):104-105, 107, 110,
112. Calfo, Anthony. 2007. Book of Coral Propagation,
2d ed. Reading Trees, Pittsburg PA. Delbeek, Charles. 2005. Reef Aquariums: Coral
Compatibility. AquariumFish.com. Dubinsky, Z. [Ed.] 1990. Coral reefs. Ecosystems
of the world. V. 25. Elsevier Sci. Publ., Amsterdam. 550
p. Hauter, Stan & Debbie, undated. Coral
Competition;Turf Wars in Coral Reef Tanks. About.com. Saltwater
Aquariums http://saltaquarium.about.com/library/blank/bl_CoralCompetition.htm Hidaka, Michio. 1985. Nematocyst Discharge,
Histoincompatibility, and the Formation of Sweeper Tentacles in the
Coral Galaxea fascicularis. Biological Bulletin, Vol. 168, No. 3
(Jun., 1985), pp. 350-358 J. B. C. Jackson and Leo Buss. 1975. Allelopathy
and Spatial Competition among Coral Reef Invertebrates. PNAS | December
1, 1975 | vol. 72 | no. 12 | 5160-5163 O. Langmeada and C. Sheppard. 2004. Coral reef
community dynamics and disturbance: a simulation model. Ecological
Modelling
Volume 175, Issue 3, 15 July 2004, Pages 271-290 Sammarco, P.W., J.C. Coll, S. La Barre and B.
Willis. 1983. "Competitive strategies of soft corals
(Coelenterata: Octocorallia): allelopathic effects on selected
scleractinian corals." Coral Reefs 2:173-178. Sebens, Kenneth P. & Julia S. Miles. 1988.
Sweeper Tentacles in a Gorgonian Octocoral: Morphological Modifications
for Interference Competition. Biological Bulletin, Vol. 175, No.
3 (Dec., 1988), pp. 378-387 Shimek, Ron. 2007. Coral crowding and combat. AFI 12/07. WetWebMedia.com: Cumulative: Cnidarian
Compatibility & FAQs on: Cnidarian
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