14 research outputs found
Photoprotection in sequestered plastids of sea slugs and respective algal sources
Some sea slugs are capable of retaining functional sequestered chloroplasts (kleptoplasts) for variable
periods of time. The mechanisms supporting the maintenance of these organelles in animal hosts are still
largely unknown. Non-photochemical quenching (NPQ) and the occurrence of a xanthophyll cycle were
investigated in the sea slugs Elysia viridis and E. chlorotica using chlorophyll fluorescence measurements
and pigment analysis. The photoprotective capacity of kleptoplasts was compared to that observed in their
respective algal source, Codium tomentosum and Vaucheria litorea. A functional xanthophyll cycle and a
rapidly reversible NPQ component were found in V. litorea and E. chlorotica but not in C. tomentosum and
E. viridis. To our knowledge, this is the first report of the absence of a functional xanthophyll cycle in a green
macroalgae. The absence of a functional xanthophyll cycle in C. tomentosum could contribute to the
premature loss of photosynthetic activity and relatively short-term retention of kleptoplasts in E. viridis. On
the contrary, E. chlorotica displays one of the longest functional examples of kleptoplasty known so far. We
speculate that different efficiencies of photoprotection and repair mechanisms of algal food sources play a
role in the longevity of photosynthetic activity in kleptoplasts retained by sea slugs
Production of Cocconeis neothumensis (Bacillariophyceae) biomass in batch cultures and bioreactors for biotechnological applications: light and nutrient requirements
9 páginas, 5 figuras, 1 tablaCocconeis neothumensis, a benthic diatom
living as epiphyte on Posidonia oceanica leaves, was
hypothesised to synthesize secondary metabolites
inducing apoptosis in the androgenic gland of the
protandric shrimp Hippolyte inermis. The optimization
of C. neothumensis cultures is a primary aim in
order to identify and characterise the active compounds
produced by this diatom. Light intensity and
concentration of nutrients, such as silicates and
selenium, are of major importance in determining
the growth rate of diatoms and the maximum
produced biomass. Thus, we evaluated the growth
performances of C. neothumensis cultures at different
light intensities, corresponding to those recorded in
Posidonia oceanica meadows in April, when the
induction of sexual reversal in Hippolyte inermis
occurs; the growth performances were also determined
in relation to different selenium and silicate
availability in the culture medium and the possible
interactions between these two micronutrients were
evaluated. Two methods of cultivations were compared:
batch cultures in Petri dishes and cultures in a
bioreactor with a continuous medium flow in the
system. C. neothumensis showed a faster growth at
low light intensities, although with a good acclimation
capacity in the range from 60 to 140 μmol photons
m−2 s
−1
. The presence of selenium in the medium
improved both the exponential growth rate and the
maximum cell density. The same results were
evidenced for a silicate concentration double that in
Guillard f/2 medium. On the other hand, a simultaneous
increase of silicate concentration and the
presence of selenium led to a loss of the positive
effects detected with single nutrients. This result
suggests either a possible antagonism in selenium
and silicate uptake or a negative interaction between
these two micronutrients in Cocconeis. The yields of
the two tested cultivation methods calculated in terms
of diethyl ether extract dry weight per unit of
substrate area were highest for the bioreactor.This work was fully funded by the E.U. in
the frame of the E.U. project PHARMAPOX (NEST STREP
Adventure 4800).Peer reviewe
A few is enough: a low cover of a non-native seaweed reduces the resilience of Mediterranean macroalgal stands to disturbances of varying extent
There is increasing evidence that the severity of the ecological impact of non-native species does not necessarily scale linearly with their abundance in the introduced range. Nonetheless, the potential of low abundance invaders to alter the resilience of native communities to disturbance has been poorly explored. On Mediterranean rocky reefs, we tested the hypothesis that (1) a pulse disturbance opening gaps within canopy stands formed by the fucoid seaweed Cystoseira brachycarpa facilitates the establishment of the non-native seaweed Caulerpa cylindracea and that (2), once established, the seaweed can reduce the recovery of macroalgal canopies. In July 2011, C. cylindracea was experimentally transplanted in small and large plots that were either cleared of the canopy or left untouched. After 45 months, the cover of C. cylindracea was greatest in small canopy-removal plots, without, however, achieving values exceeding ~10%. Nonetheless, such a low abundance of C. cylindracea caused a threefold reduction in canopy recovery. The establishment of C. cylindracea in canopy-removal plots did not alter the structure of the understory assemblages or the cover of turf-forming, erect and encrusting algae and sessile invertebrates. Our results suggest that some non-native species may be stronger competitors than natives, despite their low abundance. This property has important implications for control programs since not achieving the total eradication of the targeted invader would make little progress towards the mitigation of its impacts. Finally, our results show that non-native species acting as passengers of change can ultimately promote the persistence of alternative degraded states