Abstracts of Selected Publications
Latz, M.I., J.C. Nauen, and J. Rohr. 2004.
Bioluminescence response of four species of dinoflagellates to fully
developed pipe flow. Journal of Plankton Research 26: 1529-1546.
Dinoflagellate bioluminescence provides a nearly instantaneous index of flow sensitivity.
This study compared flow sensitivity in four species of morphologically diverse luminescent
dinoflagellates (Ceratium fusus, Ceratocorys horrida, Lingulodinium polyedrum and
Pyrocystis fusiformis) using fully developed laminar and turbulent pipe flow.
Bioluminescence response thresholds always occurred in laminar flows with wall shear
stress levels that, depending on species, ranged from 0.02 to 0.3 N m^-2. With few
exceptions, such as breaking waves and wave-forced bottom shears in shallow nearshore
areas, these threshold shear stress levels are several orders of magnitude larger than typical
oceanic ambient flows. For laminar flows above threshold, species also differed in the
proportion of organisms responding and the minimum shear stress level where individual
flashes reached their highest intensity. Following transition to turbulent flow, there was never
a dramatic increase in bioluminescence, even when energetic turbulent length scales were
similar to the cell size. On the basis of their bioluminescence response in laminar flow, these
species were ranked in order of decreasing sensitivity as C. horrida > P. fusiformis > C.
fusus > L. polyedrum. This ranking, though not conclusive, is consistent with increased flow
sensitivity due to increasing size and the presence of spines. With the exception of a small
fraction of the C. horrida population that is sensitive enough to flash within the feeding
current of a predator, the present study suggests that flashes only occur with predator
contact. Nevertheless, flow sensitivity may serve as an index of the response to mechanical
agitation during predator contact/handling. Flow sensitivity may be constrained to maximize
the response to predator contact/handling while minimizing stimulation by background
oceanic flows to avoid depleting luminescent reserves.
Latz, M.I., A.R. Juhl, A.M. Ahmed, S.E. Elghobashi, and J. Rohr. 2004.
Hydrodynamic stimulation of dinoflagellate bioluminescence: a
computational and experimental study. Journal of Experimental Biology 207: 1941-1951.
Dinoflagellate bioluminescence provides a near-instantaneous reporter of cell
response to flow. Although both fluid shear stress and acceleration are thought to
be stimulatory, previous studies have used flow fields dominated by shear. In the
present study, computational and experimental approaches were used to assess the
relative contributions to bioluminescence stimulation of shear stress and
acceleration in a laminar converging nozzle. This flow field is characterized by
separate regions of pronounced acceleration away from the walls, and shear along
the wall. Bioluminescence of the dinoflagellates Lingulodinium polyedrum and
Ceratocorys horrida, chosen because of their previously characterized different
flow sensitivities, was imaged with a low-light video system. Numerical simulations
were used to calculate the position of stimulated cells and the levels of
acceleration and shear stress at these positions. Cells were stimulated at the
nozzle throat within the wall boundary layer where, for that downstream position,
shear stress was relatively high and acceleration relatively low. Cells of C.
horrida were always stimulated significantly higher in the flow field than cells of
L. polyedrum and at lower flow rates, consistent with their greater flow
sensitivity. For both species, shear stress levels at the position of stimulated
cells were similar to but slightly greater than previously determined response
thresholds using independent flow fields. L. polyedrum did not respond in
conditions where acceleration was as high as 20 g. These results indicate that
shear stress, rather than acceleration, was the stimulatory component of flow.
Thus, even in conditions of high acceleration, dinoflagellate bioluminescence is an
effective marker of shear stress.
Stokes, M.D., G.B. Deane, M.I. Latz, and J. Rohr. 2004.
Bioluminescence imaging of wave-induced turbulence.
Journal of Geophysical Research 109: C01004 (8 pages).
The ability to measure turbulent processes on small spatial and temporal scales
is a long standing problem in physical oceanography. Here we explore a novel
means of measuring fluid shear stress using the cell flashing behavior of
bioluminescent dinoflagellates. To illustrate this technique, we present
estimates of the heterogeneous, time-varying shear stress inside a breaking wave
crest. These results have implications for a better understanding of upper ocean
wave physics, air-sea gas transfer, and the biology of planktonic near-surface
organisms as well as providing a new quantitative fluid visualization tool.
Chen, A.K., Latz, M.I. and J.A. Frangos. 2003.
The use of dinoflagellate bioluminescence to characterize cell stimulation
in bioreactors. Biotechnology & Bioengineering 83: 93-103.
Bioluminescent dinoflagellates are flow-sensitive marine organisms that
produce light emission almost instantaneously upon stimulation by fluid
shear in a shear stress dose-dependent manner. In the present study we
tested the hypothesis that monitoring bioluminescence by suspended
dinoflagellates can be used as a tool to characterize cellular response to
hydrodynamic forces in agitated bioreactors. Specific studies were performed to
determine: (1) impeller configurations with minimum cell activation,
(2) correlations of cellular response and an integrated shear factor, and
(3) the effect of rapid acceleration in agitation. Results indicated that
(1) at a volumetric mass transfer coefficient of 3X10^-4 s^-1, marine impeller
configurations were less stimulatory than Rushton configurations,
(2) bioluminescence response and a modified volumetric integrated shear
factor had an excellent correlation, and (3) rapid acceleration in agitation
was highly stimulatory, suggesting a profound effect of temporal gradients in
shear in increasing cell stimulation. By using bioluminescence stimulation as an
indicator of agitation-induced cell stimulation and/or damage in microcarrier
cultures, the present study allows for the verification of hypotheses and
development of novel mechanisms of cell damage in bioreactors.
von Dassow, P. and M.I. Latz. 2002.
The role of calcium ions in stimulated bioluminescence of the dinoflagellate
Lingulodinium polyedrum. Journal of Experimental Biology 205:
Many marine dinoflagellates emit bright discrete flashes of light nearly
instantaneously in response to either laminar or turbulent flows as well as direct
mechanical stimulation. The flash involves a unique pH-dependent luciferase and a
proton-mediated action potential across the vacuole membrane. The
mechanotranduction process initiating this action potential is unknown. The present
study investigated the role of Ca2+ in the mechanotransduction process regulating
bioluminescence in the dinoflagellate Lingulodinium polyedrum. Calcium
ionophores and digitonin stimulated bioluminescence in a Ca2+-dependent manner in
the absence of mechanical stimulation. Mechanically stimulated bioluminescence was
strongly inhibited by the intracellular Ca2+ chelator BAPTA-AM; there was only a
partial and irreversible dependence on extracellular Ca2+. Ruthenium Red, a blocker
of intracellular Ca2+ release channels, inhibited mechanically stimulated
bioluminescence. Bioluminescence was also stimulated by increasing K+ even in the
absence of extracellular Ca2; K+ stimulation was inhibited both by BAPTA-AM and
Ruthenium Red. These results support the hypothesis that Ca2+ mediates stimulated
bioluminescence and also indicate the involvement of intracellular Ca2+ stores.
Rapid coupling between mechanical stimulation and mobilization of intracellular Ca2+
stores may occur through a mechanism similar to excitation-contraction coupling in
Juhl, A.R. and M.I. Latz. 2002.
Mechanisms of fluid shear-induced inhibition of population growth of a
red-tide dinoflagellate. Journal of Phycology 38: 683-694.
Net population growth of some dinoflagellates is inhibited by fluid shear at shear
stresses comparable to those generated during oceanic turbulence. Decreased net
growth may be due to a reduction in cell division, increased mortality, or both.
Experiments to determine the dominant mechanism under various flow conditions used
the red-tide dinoflagellate Lingulodinium polyedrum (Stein) Dodge (=
Gonyaulax polyedra). Daily cell division and mortality were determined by
direct observation of isolated cells in 0.5-mL cultures in the wells of multiwell
plates. Shaking the plates generated unquantified fluid shear in each well. Larger
volume cultures were exposed to quantified laminar shear generated in Couette-flow
chambers (shear stresses of 0.004 - 0.019 N.m^-2) and to unquantified flow in shaken
flasks. Daily cell division frequency was calculated from flow-cytometric
measurements of DNA.cell^-1. In multiwell-plate experiments and in Couette-flow
experiments with low shear stress, growth inhibition was attributed to lowered cell
division without mortality. In Couette-flow experiments at higher shear stresses
and in shaken-flask experiments, cell division did not decrease and mortality was
inferred to be responsible for the decline in net population growth.
Elevated mortality from high shear stress, and the lack thereof in lower
shear-stress exposures, was confirmed using a suite of behavioral, morphological and
physiological assays. Shear-induced mortality was characterized by increased
disrupted or dead cells, and by increases in cells with damaged outer membranes and
elevated intracellular H2O2 concentration. The lowest shear stress did not cause
mortality in early exponential-phase cultures, although it caused high mortality in
late exponential-phase cultures. High shear stress did cause mortality in early
exponential-phase cultures. The results predict that growth of rapidly growing,
healthy populations of L. polyedrum may be inhibited by oceanic turbulence through
decreased cell division but mortality would not be expected unless turbulent shear
levels were unusually high. Shear-induced mortality may occur when in situ growth
conditions resemble those in late exponential/stationary phase cultures, as may
occur during later phases of in situ blooms.
S.K. Mallipattu, M.A. Haidekker, P. von Dassow, M.I. Latz, and J.A. Frangos. 2002.
Evidence for shear-induced increase in membrane fluidity in the dinoflagellate
Lingulodinium polyedrum. Journal of Comparative Physiology A 188: 409-416.
Fluid shear stress has been demonstrated to affect the structure and
function of various cell types. In mammalian cells, it was hypothesized that
shear-induced membrane fluidization leads to activation of heterotrimetric
G-proteins. The purpose of this study was to determine if a similar mechanism exists
in the dinoflagellate Lingulodinium polyedrum, a single-celled eukaryotic
aquatic organism that bioluminesces under shear stress. Membrane fluidity changes in
L. polyedrum were monitored using the molecular rotor
9-(dicyanovinyl)-julolidine, whose fluorescence intensity changes inversely with
membrane fluidity. Dual-staining with 9-(dicyanovinyl)-julolidine and the membrane
dye 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate
indicates membrane localization. Subjecting L. polyedrum cells to increasing
shear stress reversibly decreased 9-(dicyanovinyl)-julolidine fluorescence, while
autofluorescence of the cytoplasmic chlorophyll did not change. The relationship
between shear stress (0.63 Pa, 1.25 Pa, 1.88 Pa, and 2.5 Pa) and membrane fluidity
changes was linear and dose-dependent with a 12% increase in fluidity at 2.5 Pa. To
further explore this mechanism a membrane fluidizing agent, dimethyl sulfoxide was
added. Dimethyl sulfoxide decreased 9-(dicyanovinyl)-julolidine emission by 41▒15%
and elicited a dose-dependent bioluminescent response at concentrations of 0.2%,
0.5%, 1.0%, and 1.25%. This study demonstrates a link between fluid shear stress and
membrane fluidity, and suggests that the membrane is an important flow mechanosensor
Juhl, A.R., V.L. Trainer, and M.I. Latz. 2001.
Effect of fluid shear and illumination on population growth and cellular
toxin content of the dinoflagellate Alexandrium fundyense. Limnology and
Oceanography 46: 758-764.
The potential for in situ turbulence to inhibit dinoflagellate population growth
has been demonstrated by experimentally exposing dinoflagellate cultures to
quantified shear flow. However, despite interest in understanding environmental
factors that affect the growth of toxic dinoflagellates, little is known of the
effect of shear on the growth of toxin-producing dinoflagellate species. Cultures
of the dinoflagellate, Alexandrium fundyense, a producer of toxins
responsible for paraltyic shellfish poisoning, were exposed to quantified laminar
shear generated in Couette flow for 1-24 h d^-1 over 6-8 d. Shear stress in all
experiments was 0.003 N m^-2, similar to levels expected in near-surface waters
on a windy day. Net population growth decreased with shear exposures 1 h d^-1 and
became negative with exposures 12 h d^-1. Cellular toxin content at the end of
each experiment was measured by a receptor-binding assay that used [3H]saxitoxin.
Toxin cell^-1 of cultures sheared for 1 h d^-1 increased up to three times that
of control cultures. Cellular toxin content increased significiantly as growth
rate of sheared cultures decreased. However, varying culture growth rate using
irradiance had no significant effect on toxin cell^-1. Because shear stress levels
used in this study were plausible for near-surface turbulent flows, oceanic
turbulence may inhibit population growth and increase cellular toxin content of
A. fundyense. However, in natural populations it would be difficult to
distinguish the effect of turbulence on toxin content from other influences on
toxin variability, particularly if volume- or mass-specific, rather than
cell-specific, measures of toxin are used.
Juhl, A.R., V. Velasquez, and M.I. Latz. 2000.
Effect of growth conditions on flow-induced inhibition of population growth
of a red-tide dinoflagellate. Limnology and Oceanography 45: 905-915.
The population growth of some dinoflagellates is known to be reduced by exposure to
fluid flow. The red-tide dinoflagellate Lingulodinium polyedrum, was used to
examine the effect of growth conditions on flow-induced inhibition of population
growth. Three factors were tested: time of exposure relative to the light:dark
cycle, illumination level, and culture growth phase (early vs. late exponential
phase). Cultures maintained on a 12:12 h light:dark cycle were exposed to one of two
flow conditions: quantified laminar shear produced by Couette flow or unquantified
flow generated in shaken flasks. The duration of exposure to flow was 1 h d^-1 for 5
-8 d in all experiments; the shear stress in Couette shear experiments was 0.004 N
m^-2. There were many qualitative similarities in the pattern of response to flow in
the two hydrodynamic conditions. In both cases, exposure to flow in the last hour of
the dark phase resulted in greater reduction of net growth than exposure during the
light phase. Cultures grown under lower illumination had proportionally greater
reductions in net growth than cultures under higher light. Finally, late exponential
phase cultures exhibited much greater reductions in net growth following a given
flow exposure than early exponential phase cultures. The higher sensitivity of late
exponential phase cultures did not appear to be linked to nutrient limitation or
changes in pH of the medium; it may be partially attributed to exudates from late
exponential phase cells. These results suggest that the response of red-tide
dinoflagellate population growth to in situ turbulence may depend on both
environmental conditions and the physiological state of the cells.
Zirbel, M.J., F. Veron, and M.I. Latz. 2000.
The reversible effect of flow on the morphology of
Ceratocorys horrida (Peridiniales, Dinophyta). Journal of Phycology 36: 46-58.
Most cells experience an active and variable fluid environment, in which
hydrodynamic forces can affect aspects of cell physiology including gene regulation,
growth, nutrient uptake, and viability. The present study describes a rapid yet
reversible change in cell morphology of the marine dinoflagellate, Ceratocorys
horrida Stein, due to fluid motion. Cells cultured under still conditions
possess six large spines, each almost one cell diameter in length. When gently
agitated on an orbital shaker under conditions simulating fluid motion at the sea
surface due to light wind or surface chop, as determined from digital particle
imaging velocimetry, population growth was inhibited and a short-spined cell type
appeared which possessed a 49% mean decrease in spine length and a 53% mean decrease
in cell volume. The reduction in cell size appeared to result primarily from a 39%
mean decrease in vacuole size. Short-spined cells were first observed after 1 h of
agitation at 20˚C; after 8 to 12 d of continuous agitation, long-spined cells were
no longer present. The morphological change was completely reversible; in previously
agitated populations devoid of long-spined cells, cells began to revert to the
long-spined morphology within 1 d after the return to still conditions. During
morphological reversal, spines on isolated cells grew up to 10 Ám·d-1. In 30 d the
population morphology had returned to original proportions, even though the overall
population growth was zero during this time. The reversal did not occur as a result
of cell division, because single-cell studies confirmed that the change occurred in
the absence of cell division, and much faster than the 16 d doubling time. The
threshold level of agitation causing morphology change in C. horrida was too
low to inhibit population growth in the shear-sensitive dinoflagellate,
Lingulodinium polyedrum. At the highest level of agitation tested, there was
negative population growth in C. horrida cultures, indicating that fluid
motion caused cell mortality. Small, spineless cells constituted a small percentage
of the population under all conditions. Although their abundance did not change,
single-cell studies and morphological characteristics suggest that the spineless
cells can rapidly transform to and from other cell types. The sinking rate of
individual long-spined cells in still conditions was significantly less than that of
short-spined cells, even though the former are larger and have a higher cell
density. These measurements demonstrate that the long spines of C. horrida
reduce cell sinking. Shorter spines and reduced swimming would allow cells to more
rapidly sink away from turbulent surface conditions. The ecological importance of
the morphological change may be to avoid conditions which inhibit population growth
and potentially cause cell damage.
Lindsay, S.M., Frank, T.M., Kent, J., Partridge, J.C., and M.I. Latz. 1999.
Spectral sensitivity of vision and bioluminescence in the midwater
shrimp, Sergestes similis. Biological Bulletin 197: 348-360.
In the oceanic midwater environment, many fish, squid, and shrimp use luminescent
countershading to remain cryptic to silhouette-scanning predators. The midwater
penaeid shrimp, Sergestes similis Hansen, responds to downward-directed light
with a dim bioluminescence that dynamically matches the spectral radiance of oceanic
downwelling light at depth. Although the sensory basis of luminescent countershading
behavior is visual, the relationship between visual and behavioral sensitivity is
poorly understood. In this study, visual spectral sensitivity, based on
microspectrophotometry and electrophysiological measurements of photoreceptor
response, is directly compared to the behavioral spectral efficiency of luminescent
countershading. Microspectrophotometric measurements on single photoreceptors
revealed only a single visual pigment with peak absorbance at 495 nm in the
blue-green region of the spectrum. The peak electrophysiological spectral
sensitivity of dark-adapted eyes was centered at about 500 nm. The spectral
efficiency of luminescent countershading showed a broad peak from 480 to 520 nm.
Both electrophysiological and behavioral data closely matched the normalized
spectral absorptance curve of a rhodopsin with lmax = 495 nm, when rhabdom length
and photopigment specific absorbance were considered. The close coupling between
visual spectral sensitivity and the spectral efficiency of luminescent
countershading attests to the importance of bioluminescence as a camouflage strategy
in this species.
Latz, M.I. and J. Rohr. 1999.
Luminescent response of the red tide dinoflagellate Lingulodinium polyedrum
to laminar and turbulent flow. Limnology and Oceanography 44: 1423-1435.
While it is universally accepted that plankton continually experience a dynamic
fluid environment, their sensitivity to the features of the surrounding flow
field at the relevant length and time scales of the organism is poorly
characterized. The present study uses bioluminescence as a tool to understand
how the red tide dinoflagellate Lingulodinium polyedrum (=Gonyaulax
polyedra) responds to well characterized hydrodynamic forces present in
fully developed laminar and turbulent pipe flow. The response of L. polyedrum
to hydrodynamic stimulation was best characterized by wall shear stress; at
similar values of wall shear stress the response was similar for laminar and
The response threshold occurred in laminar flow at a wall shear stress of
approximately 0.3 N m^-2. At these low flow rates, video analysis of the
velocity of flash trajectories revealed that responding cells were positioned
only near the pipe wall, where local shear stress levels were equal or greater
than threshold. For cell concentrations ranging over four orders of magnitude,
threshold values of wall shear stress were restricted to a narrow range,
consistent with an antipredation function for dinoflagellate bioluminescence.
For laminar flows with above-threshold wall shear stress values <1 N m^-2,
mean bioluminescence increased with wall shear stress according to a power
(log-log) relationship, with the slope of the power function dependent on cell
concentration. The increase in bioluminescence within this range was due primarily
to an increasing population response rate, and to a lesser extent an increase in
maximum flash intensity per cell and the increased flux of organisms with higher
flow rates. For wall shear stress levels greater than 1 N m^-2, the maximum
intensity per cell remained approximately constant with increasing wall shear
stress, even as the flow transitioned from laminar to turbulent, and the smallest
turbulent length scales became less than the average cell size.
Rohr, J., M.I. Latz, S. Fallon, J.C. Nauen, and E. Hendricks. 1998.
Experimental approaches towards interpreting dolphin-stimulated bioluminescence.
Journal of Experimental Biology 201: 1447-1460.
Flow-induced bioluminescence provides a unique opportunity for visualizing the flow
field around a swimming dolphin. Unfortunately, previous descriptions of
dolphin-stimulated bioluminescence have been largely anecdotal and often
conflicting. Most references in the scientific literature report an absence of
bioluminescence on the dolphin body, which has been invariably assumed to be
indicative of laminar flow. However, hydrodynamicists have yet to find compelling
evidence that the flow remains laminar over most of the body. The present study
integrates laboratory, computational and field approaches to begin to assess the
utility of using bioluminescence as a method for flow visualization by relating
fundamental characteristics of the flow to the stimulation of naturally occurring
Laboratory experiments using fully-developed pipe flow revealed that the
bioluminescent organisms identified in the field studies can be stimulated in both
laminar and turbulent flow when shear stress values exceeded approximately 0.1
N/m^2. Computational studies of an idealized hydrodynamic representation of a
dolphin (modeled as a 6:1 ellipsoid), gliding at a speed of 2 m/s, predicted
suprathreshold surface shear stress values everywhere on the model, regardless of
whether the boundary layer flow was laminar or turbulent. Laboratory flow
visualization of a sphere demonstrated that the intensity of bioluminescence
decreased with increasing flow due to the thinning of the boundary layer, while flow
separation caused a dramatic increase due to the significantly greater volume of
stimulating flow in the wake. Intensified video recordings of dolphins gliding at
speeds of approximately 2 m/s confirmed that brilliant displays of bioluminescence
occurred on the body of the dolphin. The distribution and intensity of
bioluminescence suggest that the flow remained attached over most of the body. A
conspicuous lack of bioluminescence was often observed on the dolphin rostrum, melon
and the leading edge of the dorsal and pectoral fins, where the boundary layer is
thought to be the thinnest. To differentiate between effects related to the
thickness of the stimulatory boundary layer and those due to the latency of the
bioluminescence response and the upstream depletion of bioluminescence, laboratory
and dolphin studies of forced separation and laminar to turbulent transition were
conducted. The observed pattern of stimulated bioluminescence is consistent with the
hypothesis that bioluminescent intensity is directly related to the thickness of the
Rohr, J., J. Allen, J. Losee, and M.I. Latz. 1997.
The use of bioluminescence as a flow diagnostic.
Physics Letters A 228: 408-416.
The flash response of luminescent plankton is studied in
laminar and turbulent pipe flow. Maximum intensity levels
of individual plankton are nearly constant for wall shear
stress values exceeding approximately 10 dyn/cm2 -- regardless
of the nature of the flow. This result necessitates a reevaluation
of previous inferences made about the stimulating flow field.
Omori, M., M.I. Latz, H. Fukami, and M. Wada. 1996. New
observations on the bioluminescence of the pelagic shrimp Sergia
lucens (Hansen, 1922). pp. 175-184. In: Zooplankton: Sensory Ecology
and Physiology. P.H. Lenz, D.K. Hartline, J.E. Purcell, and D.L. Macmillan, eds.
Gordon and Breach Publishers, Amsterdam.
Bioluminescence of the sergestid shrimp, Sergia lucens, was confirmed
experimentally. To the unaided eye, light emission was oriented downward
as a dim glow which originated from the ventral and lateral body surfaces.
Image intensification revealed that this steady glow actually consisted of
scintillating sources. Photophores first appear at 4.3 mm in carapace
length (CL), and increase in number with growth. The arrangement is completed
when the shrimp is sexually mature at 9.3 mm CL. The number of photophores
of adults ranges between 158 and 169. Physiological mechanisms controlling
the light emission are unknown. Gentle prodding of the body and electrical
stimulation were ineffective, and there was very little response to serotonin
treatment. The most effective stimuli were a strobe light flash and eyestalk
crushing. Although the average emission measured from ovigerous females was
approximately twice that from males, the differences in bioluminescence according
to gender or reproductive conditions were not statistically significant.
Latz, M.I., and H.J. Jeong. 1996. Effect of red tide
dinoflagellate diet on the bioluminescence of the heterotrophic dinoflagellate,
Protoperidinium spp. Marine Ecology Progress Series 132: 275-285.
The effects of diet and cannibalism were assessed from changes in the
bioluminescence potential of two species of the heterotrophic
dinoflagellate Protoperidinium fed on 4 species of red tide dinoflagellate
prey, and with no added prey. The use of bioluminescence as a sensitive
indicator of nutritional status and feeding was explored. The
bioluminescence of Protoperidinium cf. divergens and P. crassipes
was significantly affected by dinoflagellate diet. Total
mechanically stimulable luminescence (TMSL) of P. cf. divergens
fed different dinoflagellate diets was significantly correlated
with feeding frequency (the percent of feeding P. cf. divergens
cells) rather than with population growth rate. P. cf. divergens
displayed high levels of TMSL and feeding frequency on a diet of
Scrippsiella trochoidea which did not support population growth.
Diet did not affect the total number of flashes produced per cell;
therefore changes in TMSL with dinoflagellate diet were related to
the amount of chemical substrate available for luminescence,
rather than changes in the excitation/transduction process.
Individually isolated cells remained viable for only 3 - 5 days
without food, and exhibited reduced bioluminescence. However,
cells maintained in groups survived at least 16 days ithout added
prey and maintained levels of bioluminescence similar to those
during favorable prey conditions. Cannibalism observed during this
time may have enabled cells of Protoperidinium cf. divergens to
feed and therefore produce high levels of bioluminescence in the
absence of added prey. Changes in swimming speed were less than
changes in bioluminescence. The results of the present study
suggest that energy utilization may be prioritized in the
following order: swimming (for grazing) bioluminescence (for
reducing predation) reproduction (for increasing the
Latz, M.I. 1995. Physiological mechanisms in the control of
bioluminescent countershading in a midwater shrimp. Journal of Marine and
Freshwater Physiology and Behavior 26: 207-218.
In the oceanic midwater environment, most animals have evolved an extraordinary
anti-predation behavior using bioluminescent countershading
(counterillumination) to help them remain cryptic to visual
predators. For the midwater penaeid shrimp, Sergestes similis, the
interaction of both hormonal and neural systems may be involved in
the control of counterillumination. S. similis responds to
downward-directed illumination, detected by the eyes, with light
emission from five hepatic light organs. Dark-adapted specimens
undergo a slow induction process prior to production of the
conventional counterillumination response. The induction of
bioluminescence may involve a hormonal pathway mediated by the
light-adapting retinal distal pigment dispersing hormone. Once
induced, the rapid control of counterillumination may involve a
neural pathway. Because counterilluminating animals directly
respond to their optical environment, an understanding of the
control of bioluminescence provides an insight into the poorly
understood visual processing capabilities of deep-sea animals.
Latz, M.I. and A.O. Lee. 1995. Spontaneous and stimulated
bioluminescence of the dinoflagellate, Ceratocorys horrida
(Peridiniales). Journal of Phycology 31: 120-132.
This is the first report of spontaneous bioluminescence in the autotrophic
dinoflagellate, Ceratocorys horrida von Stein. Bioluminescence was
measured, using an automated data acquisition system, in a strain
of cultured cells isolated from the Sargasso Sea. Ceratocorys
horrida is only the second dinoflagellate species to exhibit
rhythmicity in the rate of spontaneous flashing, flash quantum
flux (intensity), and level of spontaneous glowing. The rate of
spontaneous flashing was maximal during hours 2 - 4 of the dark
phase [i.e. circadian time (CT)16-18 for a 14:10 h light:dark
cycle (LD10:14)], with approximately 2% of the population
flashing.min-1, a rate approximately one order of magnitude
greater than that of the dinoflagellate, Gonyaulax polyedra. Flash
quantum flux was also maximal during this period. Spontaneous
flashes were 134 ms in duration with a maximum flux (intensity) of
3.1 x 109 quanta.s-1. Light emission presumably originated from
blue fluorescent microsources distributed in the cell periphery
and not from the spines. Values of both spontaneous flash rate and
maximum flux were independent of cell concentration. Isolated
cells also produced spontaneous flashes. Spontaneous glowing was
dim except for a peak of 6.4 x 104 quanta.s-1.cell-1 which
occurred at CT22.9 for LD14:10 and at CT22.8 for LD12:12. The
total integrated emission of spontaneous flashing and
glowing during the dark phase was 4 x 109 quanta.cell-1,
equivalent to the total stimulable luminescence (TSL). The rhythms
for C. horrida flash and glow behavior were similar to those of
Gonyaulax polyedra, although flash rate and quantum flux were
greater. Spontaneous bioluminescence in C. horrida may be a
circadian rhythm because it persisted for at least three cycles in
constant dark conditions. This is also the first detailed study of
the stimulated bioluminescence of C. horrida, which also displayed
a diurnal rhythm. Cultures exhibited 200 times more mechanically
stimulated bioluminescence during the dark phase than during the
light phase. Mechanical stimulation during the dark phase resulted
in 6.7 flashes.cell-1; flashes were brighter and longer in
duration than spontaneous flashes. Cruise-collected cells
exhibited variability in quantum flux with few differences in
flash kinetics. The role of dinoflagellate spontaneous
bioluminescence in the dynamics of near-surface oceanic
communities is unknown, but it may be an important source of
natural in situ bioluminescence.
Latz, M.I., J.F. Case, and R.L. Gran. 1994. Excitation of
bioluminescence by laminar fluid shear associated with simple
Couette flow. Limnology and Oceanography 39: 1424-1439.
The effect of fluid motion on the excitation of bioluminescence
was examined for cultured dinoflagellates and plankton samples
subjected to steady-state laminar shear associated with simple
Couette flow established in the gap between concentric cylinders,
with only the outer cylinder rotating. The excitation threshold
for the thecate dinoflagellate, Gonyaulax polyedra, occurred
at a shear stress of 1 dyn cm^-2. At higher shear stresses light output
per cell was proportional to pproximately the second power of shear
stress. At each maintained shear stress, bioluminescence decreased
exponentially at a rate proportional to the magnitude of shear
stress. The nonthecate dinoflagellates, Pyrocystis fusiformis and
P. noctiluca, were more sensitive to stimulation and exhibited an
order of magnitude higher rate of depletion than for G. polyedra.
Plankton samples from the Sargasso Sea and eastern Pacific had
similar excitation thresholds but differed in the slope of the
intensity vs. shear response most likely due to different
luminescent populations. The excitation threshold obtained from
this study is several orders of magnitude greater than oceanic
shear stress values in the mixed layer, suggesting that ambient
fluid motion, with the exception of surface breaking waves, does
not stimulate bioluminescence.
Abstracts / Updated 7/16/03 / firstname.lastname@example.org