Biology Reference
In-Depth Information
2009
) and another polybrominated compound 1,1,3,3-tetrabromo-2-heptanone
inhibits also bacterial colonization (Nylund et al.
2008
).
Other examples of allelopathic interactions have been also recently reviewed by
Jormalainen and Honkanen (
2008
) in bloom-forming macroalgae, such as
Ulva
fenestrata
,
Ulvaria,
and
Pylaiella littoralis
that gain competitive success using
toxic exudates against germlings of canopy-forming seaweeds (Nelson et al.
2003
;
R
˚
berg et al.
2005
). Recently also, the invasive red alga
Lophocladia lallemandii
was observed growing as an epiphyte on
C. taxifolia
, and levels of caulerpenyne
were found to be higher on
C. taxifolia
that was epiphytized by
L. lallemandii
(Box et al.
2008
). Additionally, activities of antioxidant enzymes, catalase and
superoxide dismutase, and H
2
O
2
production were higher in epiphytized
C. taxifolia
than in thalli that were not epiphytized by
L. lallemandii
, pointing as the evolution of
a defensive mechanism against the new invasive algal epiphyte using caulerpynyne,
previously proposed as an allelopathic substance in the invasion success of
C. taxifolia
(Pohnert
2004
).
In crustose coralline algae also, allelopathy may be an important means to
prevent overgrowth by canopy-forming macroalgae (reviewed by Gross
2003
).
The crustose coralline alga,
Lithophyllum
sp., produces an allelopathic, nonpolar
substance that destroys zoospores of the brown alga,
Laminaria religiosa
(Suzuki
et al.
1998
). Suzuki et al. (
1998
) suggested that the reduction of epiphytes due to
allelopathy may contribute to the predominance of crustose coralline algae in the
coastal region of the Northern Japan Sea. In another study, extracts from the
crustose coralline alga
Lithophyllum yessoense
inhibited spore settlement of 14,
and germination of spores of 13, of the total of 17 tested macroalgal species (Kim
et al.
2004
). Kim et al. (
2004
) suggested that
L. yessoense
probably has multiple
allelochemicals, including water-soluble exudates, to cope with macroalgal
recruits. More recently, the algal spore lytic fatty acid hydroperoxide of
heptadeca-5,8,11-trienoic acid (HpDTE: C17:3) was isolated from the crustose
coralline seaweed
Lithophyllum yessoense
. HpDTE showed more than 50% lysis
at a concentration of 5
gmL
1
against the spores of three chlorophyte species,
nine rhodophytes, four phaeophytes, and the cells of four phytoplankton species.
Lysis activity increased with the number of double bonds and carbon atoms in the
fatty acid derivatives (Luyen et al.
2008
).
The wound response of the red alga
G. chilensis
involves the release of free fatty
acids as well as the hydroxylated eicosanoids, 8R-hydroxy eicosatetraenoic acid
(8-HETE) and 7S,8R-dihydroxy eicosatetraenoic acid (7,8-di-HETE) (Lion et al.
2006
). While the release of free arachidonic acid and subsequent formation of
8-HETE is likely controlled by phospholipase A, 7,8-di-HETE production is inde-
pendent of this lipase. This dihydroxylated fatty acid might be directly released
from galactolipids that contained 8-HETE or 7,8-di-HETE (Lion et al.
2006
). In this
context, the induced chemical defense response of the red alga
G. chilensis
against
epiphytes was also investigated. An extract of an epiphyte challenged alga was
shown to trigger a defense response (Weinberger et al.
2011
). The hormonally
active metabolite(s) could further be purified by reverse phase RP-HPLC. Treat-
ment with the extract or the fraction resulted in pronounced changes of the chemical
m
