The Great Barrier Reef
226
BOX 21.1 TECHNIQUES USED TO COLLECT, PRESERVE AND
INVESTIGATE OCTOCORAL COLONIES
When taxonomic identification is attempted, a photograph showing the entire colony
and its growth form is advantageous, and close-ups of details of the surface and polyp
structures are useful for reference. Although with practice it is possible to identify a
number of octocorals to genus level underwater or from photographs, it is rare that
they can be identified to species level because a compound microscope is needed to
investigate sclerites in detail. Most soft corals have different sclerites in the upper
polyp-bearing surface of the colony (lobes, branches), the interior of the polyp region,
the surface and interior of the base, and within the polyps. The arrangement of the
sclerites within the polyps and polyp tentacles can also be informative as it can vary
widely between species. For a full diagnosis, until a satisfactory level of field confidence is achieved, it is therefore necessary to collect a sample with all of the main colony regions present. Note that a sampling permit is required for collection on the GBR,
and in general, sampling should be minimised wherever possible. If a sampling permit
exists and sampling is considered essential, with small colonies the whole specimen
may have to be collected. With larger specimens this is neither practical nor necessary.
In broad, thickly encrusting colonies it is sufficient to remove a segment shaped like a
pie-slice, which includes upper lobes (branches or ridges, and polyps), the surface layer
of the colony side down to the base, and the attached interior portions. In gorgonians,
one branch is sometimes sufficient to obtain surface, interior, and polyp material for
sclerite examination, but for species determination more material may have to be collected, as sclerites can vary between branches and from colony base to upper (younger)
colony parts. The branching pattern is an extremely important diagnostic feature that
may be captured by a good photograph to minimise sampling. Growth form is especially important in the family Ellisellidae because a number of genera only differ in this
character.
Long term storage of small to medium sized octocoral specimens is best in 70% ethanol
(ethyl alcohol) in fresh water, in which colonies will last indefinitely. It is not recommended
to initially fix octocorals in dilute formalin, as the calcareous octocoral sclerites are eventually eroded by the acids derived from the oxidation of formaldehyde to formic acid (even if
buffered), which will make identification impossible and complicate DNA analyses. If dilute formalin is initially used to reduce shrinkage, the storage alcohol needs to be regularly
changed until all traces of formaldehyde are removed. Numerous specimens reliably
tagged, or individually placed in plastic bags with holes, can be kept together in a single
large container suitable for alcohol storage. Larger gorgonian branches may have to be airdried unless a container of sufficient size can be found, but air-dried samples are more difficult to work with, they are more prone to abrasion and breakage, and susceptible to mould
and insect attack. A compromise then is to keep a portion of a large specimen in alcohol.
To examine sclerites they must be freed from the coenenchyme in which they are
embedded by the use of concentrated bleach (sodium hypochlorite), which dissolves
the organic tissues and leaves the sclerites untouched. Unless the sclerites are large, a
226
BOX 21.1 TECHNIQUES USED TO COLLECT, PRESERVE AND
INVESTIGATE OCTOCORAL COLONIES
When taxonomic identification is attempted, a photograph showing the entire colony
and its growth form is advantageous, and close-ups of details of the surface and polyp
structures are useful for reference. Although with practice it is possible to identify a
number of octocorals to genus level underwater or from photographs, it is rare that
they can be identified to species level because a compound microscope is needed to
investigate sclerites in detail. Most soft corals have different sclerites in the upper
polyp-bearing surface of the colony (lobes, branches), the interior of the polyp region,
the surface and interior of the base, and within the polyps. The arrangement of the
sclerites within the polyps and polyp tentacles can also be informative as it can vary
widely between species. For a full diagnosis, until a satisfactory level of field confidence is achieved, it is therefore necessary to collect a sample with all of the main colony regions present. Note that a sampling permit is required for collection on the GBR,
and in general, sampling should be minimised wherever possible. If a sampling permit
exists and sampling is considered essential, with small colonies the whole specimen
may have to be collected. With larger specimens this is neither practical nor necessary.
In broad, thickly encrusting colonies it is sufficient to remove a segment shaped like a
pie-slice, which includes upper lobes (branches or ridges, and polyps), the surface layer
of the colony side down to the base, and the attached interior portions. In gorgonians,
one branch is sometimes sufficient to obtain surface, interior, and polyp material for
sclerite examination, but for species determination more material may have to be collected, as sclerites can vary between branches and from colony base to upper (younger)
colony parts. The branching pattern is an extremely important diagnostic feature that
may be captured by a good photograph to minimise sampling. Growth form is especially important in the family Ellisellidae because a number of genera only differ in this
character.
Long term storage of small to medium sized octocoral specimens is best in 70% ethanol
(ethyl alcohol) in fresh water, in which colonies will last indefinitely. It is not recommended
to initially fix octocorals in dilute formalin, as the calcareous octocoral sclerites are eventually eroded by the acids derived from the oxidation of formaldehyde to formic acid (even if
buffered), which will make identification impossible and complicate DNA analyses. If dilute formalin is initially used to reduce shrinkage, the storage alcohol needs to be regularly
changed until all traces of formaldehyde are removed. Numerous specimens reliably
tagged, or individually placed in plastic bags with holes, can be kept together in a single
large container suitable for alcohol storage. Larger gorgonian branches may have to be airdried unless a container of sufficient size can be found, but air-dried samples are more difficult to work with, they are more prone to abrasion and breakage, and susceptible to mould
and insect attack. A compromise then is to keep a portion of a large specimen in alcohol.
To examine sclerites they must be freed from the coenenchyme in which they are
embedded by the use of concentrated bleach (sodium hypochlorite), which dissolves
the organic tissues and leaves the sclerites untouched. Unless the sclerites are large, a