UvA-DARE (Digital Academic Repository)
Daphnids respond to algae-associated odours.
van Gool, F.T.J.; Ringelberg, J.
Published in:
Journal of plankton research
DOI:
10.1093/plankt/18.2.197
Link to publication
Citation for published version (APA):
van Gool, F. T. J., & Ringelberg, J. (1996). Daphnids respond to algae-associated odours. Journal of plankton
research, 18, 197-202. DOI: 10.1093/plankt/18.2.197
General rights
It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s),
other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).
Disclaimer/Complaints regulations
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating
your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask
the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam,
The Netherlands. You will be contacted as soon as possible.
UvA-DARE is a service provided by the library of the University of Amsterdam (http://dare.uva.nl)
Download date: 15 Jun 2017
Journal of Plankton Research Vol.18 no.2 pp.197-202,1996
Daphnids respond to algae-associated odours
Erik van Gool and Joop Ringelberg
Department of Aquatic Ecology, University of Amsterdam, Kruislaan 320,1098
SM Amsterdam, The Netherlands
Abstract Using a Y-tube olfactometer, it was found that Daphnia galeata x hyalina moves to the arm
with odour from either of two edible algal species (Scenedesmus acuminatus and Oscillawria limnetica)
rather than to the alternative arm with clean water. However, no differential response was observed
when odours of the toxic cyanobacterium (Oscillaioria agardhn) were tested. We suggest that odours
associated with edible algae attract Daphnia, whereas non-edible algae do not elicit attraction of
Daphnia.
Introduction
While terrestrial ecologists recognized the importance of non-random search
guided by info-chemicals, such as pheromones and kairomones (for terminology,
see Dicke and Sabelis, 1988), aquatic ecologists were under the impression that
zooplankton float passively, largely at the mercy of water currents. At the scale of
the action radius of an individual plankton animal, the pelagic zone of lakes and
oceans seems rather homogeneous. Hence, the need for oriented horizontal movements in response to chemical cues was considered to be low.
This has all changed during the past two decades. Pioneer cinematography studies by Strickler (1975) of copepods, catching algae or prey animals, have revealed
various behavioural patterns that were influenced by chemical cues. Prey can distinguish vertebrate and invertebrate predators by smell and change behaviour
accordingly. A good example is the initiation of diel vertical migration. Extensive
migrations of copepods and cladocerans occur when fish predators are abundant
(Bollens and Frost, 1989; Ringelberg et al., 1991), and the change in behaviour is
elicited by predator kairomones (Ringelberg, 1991; Forward and Rittschof, 1993;
De Meester, 1993; Loose, 1993). Other kinds of behaviour, such as swarming and
somersaulting in Daphnia, are similarly influenced by kairomones (Pyanowska,
1994).
It is often suggested that chemical cues from potential food algae could be of
importance because some are difficult to ingest or are nutritionally poor (e.g. Larsson and Dodson, 1993). Cyanobacteria are well-known examples of unprofitable
algae (Lampert, 1987). The products released by these prokaryotes decrease the
feeding rate of Daphnia (Ostrofsky et al., 1983; Forsyth et al., 1992; Haney et al.,
1995). Particle selectivity by contact chemoreception is present in copepods
(Friedman and Strickler, 1975; Poulet and Marsot, 1978). However, the hypothesis
of remote detection of algae by kairomones was not supported by experiments of
DeMott and Watson (1991). Selectivity of particles in copepods is well established,
but cladocerans are considered to passively select food particle size.
In this paper, we present the results of experiments to test whether Daphnia
respond to water in which algae were kept for some time, and thus possibly containing algal-associated odours, when clean water was the alternative.
© Oxford University Press
197
E.van Gool and J.Ringelberg
Method
A Y-tube olfactometer was used to test whether Daphnia galeata x hyalina can
perceive odours of algae. This simple apparatus consists of a Y-shaped glass tube
with two arms (at an angle of 75°) and one basal leg, each with a length of 13 cm and
a diameter of 3.5 cm. The two arms served as inflows for water that was pumped
into them at a rate of 7.8 ml miir1. The water outflow was at the base of the leg. This
Y-tube was placed horizontally in a water bath to reduce changes in temperature
and, as far as possible, unwanted response-inducing patterns in light scatter and
breaking. Experiments were carried out in a dark room and temperature was controlled at 17-19°C. Illumination was from above by fluorescent lights. The pattern
of waterflowin the Y-tube was studied by release of ink into one of the arms. One
minute after release, this arm was completely filled and after the bifurcation point
theflowsof both arms did not mix, but remained separated up to the outflow.
Water used in the experiments originated from the hypolimnion of Lake Maarsseveen [for a description of this lake, see Ringelberg (1981) and Swain et al.
(1987)]. This water was circulated over a sand filter to stimulate the breakdown of
organic matter for at least 2 days before use.
Odour from three species of algae was tested: Scenedesmus acuminatus, the
standard source of food in our Daphnia cultures; Oscillatoria Hmnetica, a cyanobacterium on which Daphnia easily grows (S.Repka, personal communication);
and Oscillatoria agardhii, a toxic strain (M.Liirling, personal communication).
Scenedesmus acuminatus was grown as a continuous culture, both Oscillatoria
species were grown as batches. Algae were centrifuged and resuspended in the
above-mentioned water from Lake Maarsseveen, for S.acuminatus at a concentration of 0.5 mg C 1~\ for both Oscillatoria at unknown (high) concentrations.
After 1 day, the algae were removed by filtering over 0.45 (im and the filtrate was
immediately used in the experiments against clean 0.45 ^.m filtered water from
Lake Maarsseveen.
One day before tests, adult females of the hybrid D.galeata x hyalina were taken
from our standard culture and put in clean Maarsseveen water with S.acuminatus
at a concentration of —0.5 mg C I 1 .
At the start of an experiment, the Y-tube was almost completelyfilledwith clean
water. An individual daphnid was put in a small beaker with clean water and introduced with this water into the leg of the Y-tube. Next, the leg was closed with a plug
provided with the outflow. Finally, the whole Y-tube was covered by black paper,
except for a small window above the outflow leg near the bifurcation. In this way,
the daphnid was trapped optically in this part of the leg, thereby ensuring the same
starting position of successive animals. After ~5 min of detainment, the inflow
with clean water and test water containing odour of algae was started. One minute
later, the Daphnia was released by gently lifting the black covering of the inflow
arms. This resulted in the animal swimming into one of the inflow arms. Only daphnids that reached a distance of 9 cm into one of the arms were scored. Daphnids
were used only once. After each run, the Y-tube was cleaned thoroughly with a
brush and hot water. The inflow of algal odour was shifted to the other inflow arm
after 10 runs, to prevent possible position effects. Although each daphnid was able
to move freely over the whole cross-section of the outflow leg, it is possible that in
198
Daphnids respond to algae-associated odours
some cases algae-associated odour was never experienced, because the water currents from both arms remained largely separated. This increased the chance of a
type I error (Sokal and Rohlf, 1981).
The null hypothesis is derived directly from the design of the Y-tube: P(odour) =
/'(clean) = 0.5 (no preference), and the binomial test (Siegel and Castellan, 1988)
was used to test this hypothesis.
Results
Experiments with clean water entering both arms of the Y-tube showed that the
null hypothesis could not be rejected. Comparable numbers of daphnids reached
the distance of 9 cm in either arm (47 and 53%, respectively; TV = 34). Thus, no
environmentally induced position effect was present. To be certain, any such effect
in the experiments was further reduced by switching the odour side after each 10
runs.
Results of the tests were in conflict with the null hypothesis that Daphnia
showed no preference for water which previously contained edible algae. Preference for the arm containing odour of S.acuminatus was highly significant (P <
0.0001, N = 97; Figure 1) with 73% of the animals ending up at the arm containing
the odour. The tests with odour of the edible cyanobacterium O.limnetica showed
the same result: 70% of the animals were found in the arm with the algal flavour
(N = 60,P = 0.0027; Figure 1).
When water that had contained the toxic cyanobacterium O.agardhii was used
as odour source, no preference could be observed: 52% of the animals (not significant; N = 69) ended up in the arm where odour was offered (Figure 1).
Discussion
Our results show that D.galeata x hyalina discriminates between clean water and
water that previously contained algae. Because water with algae wasfiltered,leakage of the contents of damaged cells into the water cannot be excluded. However,
even if leakage products smaller than 0.45 u.m were responsible for the observed
preferences, the results may still be ascribed to odour perception. Nevertheless,
one may question whether responses to algae-associated chemicals, as shown
under ideal, artificial conditions, promote foraging under more realistic
conditions.
The differential effect of O.limnetica and O.agardhii species or strains with and
without nutritional value, or without and with toxic properties, respectively, suggests that specific information can be derived. It may be expected that water from
the toxic O.agardhii would have a repellent effect, but it elicited no significant
response. Perhaps, in the case of toxic algae, the information derived from algaeassociated chemicals is both 'attractive' and 'repellent'. Experiments comparing
species simultaneously in a Y-tube olfactometer will increase insight into the
potential of chemoperception in daphnids.
In general, the swimming behaviour of Daphnia seems to be quite erratic. However, they are very sensitive to temporal and spatial differences in light intensity,
and small irregularities in the angular light field might be held responsible for
poorly understood swimming behaviour. In our experiments, significant swim199
E.van Gool and J.Ringelberg
Scaiedesmus acuminatus
odour
clean
odour
dean
odour
dean
Oscillatoria limnetica
Oscillaloria agardhii
Fig. 1. Fraction diagram of responses of D.galeata x hyalina to algae-associated odours in a Y-tube
olfactometer, choice between clean water and water that previously contained the algae indicated
above the diagram. N values represent the numbers of Daphnia tested. Asterisks indicate the level of
significance: **P < 0.003; •*•/» < 0.0001; n.s. = not significant.
ming into one of the inflow arms of the Y-tube could be easily realized by an appropriate angular light distribution. However, careful control of the light field proved
that no bias to either arm was present in the control runs. It also proved important
to have a similar starting position in the outflow leg for all runs and this was realized
by making use of Daphnia's strong photo-orientation. The subsequent release and
directional swimming into either arm was likewise predominantly realized
optically. The arm chosen was influenced by the presence of odour in the inflowing
water.
The results do not reveal what adaptive value must be attributed to the demonstrated chemoperception of algae-associated kairomones. It is obvious to suggest
that swimming toward patches of high-quality algae is adaptive. This requires
200
Daphnids respond to algae-associated odours
remote chemoreception in the first place, but oriented swimming should follow in
order to bring the animal successfully to the source. In our setting, swimming was
predominantly directed by an experimentally induced photobehaviour. Daphnids
also tend to swim upstream (rheotaxis) and weak water currents might thus direct
the animal to a source of attractive kairomones. The action radius of these daphnids must be considered in relation to the distance between patches, however. On a
smaller scale, chemoperception might be used for continuous redistribution within
a patch when dense aggregates of animals deplete an area of algae. Swarming is
common in this species and, with regard to feeding, might offer the advantage of a
more easy assimilation of algae that pass the gut repeatedly (Kersting, 1991). On
the other hand, competition might become predominant in an aggregate when the
concentration of algae is considerably diminished. Redistribution is then profitable. Relevant experiments must be designed to deal with these aspects of optimal
foraging. The results of our experiments show that Daphnia has the potential to
discriminate between ecologically relevant odours. At what spatial scale such
information is used is an open question for future research.
Acknowledgements
We thank Jan Bruin, Arne Janssen, Maurice Sabelis and two anonymous
reviewers for their comments on an earlier version of this manuscript. Sari Repka
(Centre for Limnology, Nieuwersluis) provided us with O.limnetica and Miquel
Ltirling (Agricultural University, Wageningen) with O.agardhii. They are cordially thanked. The investigations were supported by the Life Science Foundation
(SLW), which resorts under the Netherlands Organization for Scientific Research
(NWO).
References
Bollens,S.M. and Frost.B.W. (1989) Zooplanktivorous fish and variable diel vertical migration in the
marine planktonic copepod Calanuspacificus. Limnol. Oceanogr.M, 1072-1083.
De Meester.L. (1993) Genotype, fish mediated chemicals, and phototactic behaviour in Daphnia
magna. Ecology, 74, 1467-1474.
DeMott.W.R. and Watson.M.D. (1991) Remote detection of algae by copepods: responses to algal size,
odors and motility.y. Plankton Res.. 13,1203-1222.
Dicke.M. and SabelisJvl.W. (1988) Infochemical terminology: based on cost-benefit analysis rather
than origin of compounds? Fund. Ecol, 2,131-139.
Forsyth.DJ., Haneyj.F. and James.M.R. (1992) Direct observation of toxic effects of cyanobacterial
extracellular products on Daphnia. Hydrobiologia, 228, 151-155.
Forward,R.B. and Rittschoff,D. (1993) Activation of photoresponses of brine shrimp nauplii involved
in diel vertical migration by chemical cues from fish. J. Plankton Res., 15, 693-701.
Friedman.M.M. and StricklerJ.R. (1975) Chemoreceptors and feeding in calanoid copepods (Arthropoda: Crustacea), Proc Natl Acad. Sci. USA, 72,4185-4188.
Haneyj.F., SasnerJJ. and Ikawa.M. (1995) Effects of products released by Aphanizomenon flosaquae and purified saxitoxin in the movements of Daphnia carinata feeding apendages. LimnoL
Occanogr., 40,263-272.
Kersting.K. (1991) Recycling of food by Daphnia magna Straus (Cladocera): a possible role in swarming. Hydrobiol. Bull, 25, 73-75.
Lampert.W. (1987) Feeding and nutrition in Daphnia. Mem. 1st. Ital. IdrobioL,45,143-192.
Larsson.P. and Dodson.S. (1993) Chemical communication in planktonic animals. Arch. Hydrobiol.,
129,129-155.
Loose.CJ. (1993) Daphnia diel vertical migration behavior: response to vertebrate predator abundance. Arch. Hydrobiol. Beih. Ergebn. Limnol, 39,29-36.
201
E.van Gool and J.Ringelberg
Ostrofsky.M.L.. Jacobs.F.G. and Rowan J. (1983) Evidence for the production of extracellular herbivore deterrents by Anabcnaflos-aquae.Freshwater Bioi, 13. 501-506.
PijanowskaJ.(1994) Fish enhancement patchiness in Daphnia distribution. Verh. Int. Ver. Limnol..2S,
2366-2368.
Poulet.S.A. and Marsot.P. (1978) Chemosensory grazing by marine calanoid copepods (Arthropoda.
Crustacea). Science, 200, 1403-1405.
RingelbergJ. (1981) Introduction to the research area. Hydrobiol. Bull.. 15.5-10.
RingelbergJ. (1991) Enhancement of the phototactic reaction in Daphnia hyalma by a chemical
mediated by juvenile perch {Percafluviaiilis).J. Plankton Res., 13.17-25.
RingelbergJ. Flik.BJ.G., Lindenaar, D. and Royackers.K. (1991) Diel vertical migration of Daphnia
hsaiina (sensu latiori) in Lake Maarsseveen: Part 1. Aspects of seasonal and daily timing. Arch.
Hydrobiol., 121,129-145.
Siegel.S. and Castellan.NJ. (1988) Nonparametric Statistics for the Behavioural Sciences, 2nd edn.
McGraw-Hill.
Sokal.R.R. and Rohlf.FJ. (1981) Biometry, 2nd edn. W.H.Freeman and Co., New York.
StricklerJ.R. (1975) Intra-and interspecific information flow among planktonic copepods: Receptors.
Verh. Int. Ver. Limnoi. 19, 2951-2958.
Swain.W.R., Lingeman.R. and HeinisJ. (1987) A characterization and description of the Maarsseveen
Lake system. Hydrobiol. Bull., 21, 5-16.
Received on July 31, 1995; accepted on October 13, 1995.
202