MPH-treated female guppies were more exploratory than control fish in novel environments and with novel objects. Specifically, MPH fish were more likely to swim in inner areas of an unfamiliar tank and approach novel objects. However, for novel males, MPH fish showed more interest only in the second male exposed to, regardless of novelty. This suggests the dopaminergic system regulates novelty-seeking in guppies, though their responses to different novel stimuli varied.

1. Novelty-seeking behaviour in Trinidadian guppies is enhancedNovelty-seeking behaviour in Trinidadian guppies is enhanced
by a widely used stimulantby a widely used stimulant
Novelty-seeking behaviour in Trinidadian guppies is enhancedNovelty-seeking behaviour in Trinidadian guppies is enhanced
by a widely used stimulantby a widely used stimulant
Environment?
Object?
Male?
Discussion
◘ Acute exposure to a stimulant (MPH) increased
interest in novel stimuli, both a novel object and
environment, in female Trinidadian guppies.
◘ As with previous studies on other species, this
suggests a role of the dopaminergic system in
guppies.
◘ Novelty-seeking in wild guppies may be
adaptive, as food-limited individuals that explore
novel food types and novel habitats may gain
access to increased resources and mating
opportunities.
◘ Behavioural phenotypes in guppies: both novelty-
seeking and side effects associated with stimulant use in
humans, e.g. stereotypies and aggression
◘ Inheritance of synaptic plasticity: specifically, epigenetic
mechanisms
◘ To survey the genes responsible for DA expression in
guppies8
, at the individual and population levels.
◘ If these alleles can be linked to behavioural
phenotypes, this could explain some of the standing
behavioural variation in natural populations of
Trinidadian guppies for behaviours such as:
◦ Exploratory behaviour in novel environments4
◦ Responses to novel objects9
Background
◘ Novelty seeking, the willingness to investigate novel stimuli, can have
important consequences in natural populations, e.g. affecting
survivorship, gene flow.
◘ Female Trinidadian guppies, Poecilia reticulata, show a preference
for rare/unfamiliar males1,2,3
and show among-population differences in
exploratory behaviour of unfamiliar environments4
.
◘ Novelty seeking in rodents is associated with the neurotransmitter
dopamine (DA): ↑ DA levels associated with ↑ novelty-seeking5
◘ However, it is not clear if an orthologous pathway is responsible in
teleosts.
Figure 1. Schematic of the novelty test
protocol (right). Purple colouration
indicates the novel stimulus in each test.
We observed all experimental fish in
tests 1 & 2 (novel environment and
object, respectively), while only a subset
were observed in test 3 (novel male).
Objectives
To determine whether:
1) the dopaminergic pathway regulates novelty-seeking
behaviour in guppies
2) different types of novel stimuli (environment, object,
and individuals) evoke a similar behavioural phenotype
in response to DA manipulation
Methods
◘ Sets of two females, randomly
assigned to either an MPH
(MPH+conditioned water) or
control (conditioned water)
treatment, were tested in a series
of novelty tests (see Figure 1).
◘ Trials were conducted at the
same time each morning by an
observer who was blind to the
treatment status of each fish.
◘ Meningeal darkness was
recorded before and after each
test as an indicator of stress
level7
Alexandra R. De Serrano, Charmaine Fong, & F. Helen Rodd
Dept. Of Ecology and Evolutionary Biology, University of Toronto
A: Yes, MPH guppies were
more exploratory in a novel
environment than control fish;
that is, MPH fish were more
likely to swim through the
inner squares of the unfamiliar
environment
A: Yes, MPH guppies
were more likely to
approach novel
objects than control
fish
Figure 2. Transformed relative proportion of inner to outer
squares traversed by female guppies (n=26) in the open field
test. The data were transformed using arcsin square root and
meningeal darkness was included as a covariate in the ANOVA
(F4,42
= 3.14, one-tailed P = 0.03).
Figure 3. Five-number summary for the
number of approaches made by MPH
(n=21) and control (n=21) guppies to
black and orange disks (novel objects).
Data were analyzed using a sign test (one-
tailed sign test: black disk, P = 0.03; orange
disk, P = 0.03.)
A: It's complicated...
MPH-treated females were more
interested than controls in the
second male (Male2) they were
exposed to, regardless of the
novelty status of Male2.
Figure 4. Mean duration spent by MPH (n=7) and control females
(n=7) within 2.5cm of the male in the novel male test (two-way
ANOVA: F1,13
= 5.42, P = 0.04). There was not a significant effect of
morph of Male1 on the response to Male2 (ANOVA: P > 0.2 )or
treatment on their responses to Male1 (ANOVA: P > 0.7).
◘ We exposed female guppies to a very low, acute dose (2.5*10-8 g/ml) of
methylphenidate hydrochloride (MPH (Ritalin®)), a stimulant known to increase DA
levels6
Do control and MPH-treated female guppies differ in
their response to a novel...
References
1. Hughes KA, Du L, Rodd FH, Reznick D, 1999, Anim. Behav., 58, 907-916; 2. Eakley AL, Houde AE,
2004, Proc. R. Soc. Lond. B, 271; 3. Zajitschek SRK, Brooks RC, 2008, Am. Nat., 172, 843-854; 4. Burns JG,
Rodd FH, Price AC, Thomson JD, ms in prep; 5. Mällo T, Alttoa A, Kõiv K, Tõnissaar M, Eller M, Harro J.
2006. Behavioural Brain Research, 177, 269-281; 6.Solanto MV, 2002, Behavioural Brain Research, 130, 65-
71; 7. Gibson R, Burns JG, Rodd FH, 2009, Can. J. Zool. 87, 529-536; 8. Fraser BA, Weadick CJ, Janowitz I,
Rodd FH, Hughes KA. 2011. BMC Genomics. 12, 202; 9. Rodd FH, Hughes KA, Grether GF, Baril CT.
2002. Proc. R. Soc. Lond. B 269, 475-481.
Future research:
Currently we are testing the effect of chronic
MPH exposure on: