Ecology of Freshwater Fish 2014: 23: 656–658
Ó 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
ECOLOGY OF
FRESHWATER FISH
Letter
Fin-flicking behaviour as a means of cryptic
olfactory sampling under threat of predation
Randy Sutrisno1, Phillip M. Schotte1, Sara K. Schultz2, Brian D. Wisenden1
1
Biosciences Department, Minnesota State University Moorhead, Moorhead, MN USA
Department of Physics and Astronomy, Minnesota State University Moorhead, Moorhead, MN USA
2
Accepted for publication October 27, 2013
Risk of predation is a ubiquitous component of
behavioural decision-making (Lima & Dill 1990).
For small littoral fishes, chemical cues released from
predators and/or injured conspecifics, comprise
important sources of information about the presence
and nature of predation risk (see Kelley 2008; Ferrari
et al. 2010 for recent reviews). Behavioural responses
to these chemical cues include area avoidance,
increased shoal cohesion, reduction in activity, movement out of the water column, use of shelter and finflicking (Lawrence & Smith 1989; Ferrari et al.
2010). Collectively, these behavioural responses
reduce the probability of predation (Mathis & Smith
1993).
Fin-flicking is a behaviour in which fish quickly
sweep their pectoral fins anteriorly, matched with
concomitant counterbalancing forward thrusts of the
anal and caudal fin, resulting in no net movement.
The function of fin-flicking has not received much
attention in the context of antipredator behaviour.
Fin-flicking by glowlight tetras (Hemigrammus erythrozonus, Durbin 1909) in response to conspecific
chemical alarm cues induced greater shoal cohesion
in conspecifics and also deterred attack behaviour by
a potential predator, the Jack Dempsey cichlid (Rocio
octofasciata, Regan 1903; Brown et al. 1999). Be
that as it may, the precursor function of fin-flicking
signals may be more utilitarian in nature and only
later became co-opted into a visual signalling system.
This brief communication presents a test of the
hypothesis that fin-flicking by alarmed fish serves the
selfish benefit of allowing individuals to sample
chemical cues in the surrounding waters whilst
remaining motionless to avoid attracting attention
from predators.
Receptors that detect chemical alarm cues and
predator odours are arranged in rosettes in the nares,
which are blind pouches in the rostrum (Døving &
Lastein 2009). Advection (mass water movement) of
water to the nares is generated by ram ventilation as
fish move through the water column. When risk is
detected, fish are faced with a trade-off because the
physical swimming movements needed to assess predation risk are conspicuous to predators. Fin-flicking
behaviour may be a solution to this trade-off if it
allows individuals to discreetly create microcurrents
of water past the nares resulting in continuous sampling of chemical information of the surrounding
water without the accompanying movements that
would compromise crypsis.
Java moss (Taxiphyllum barbieri) was chopped into
2-mm pieces to create small neutrally buoyant particles that would allow us to visualise water currents
generated by fin-flicking. In one recording session, an
adult fathead minnow (Pimephales promelas, Rafinesque 1820) was placed in a shallow white plastic
trough that afforded good visual contrast with the
moss fragments. In a second recording session, an
adult fathead minnow was placed into a narrow aquarium with a small amount of clay to visualise water
currents. Skin extract was prepared by killing an adult
fathead minnow by cervical dislocation and then
lightly scoring its flanks with a clean razor blade. One
minnow was killed for each session of filming. The
minnow carcasses were then soaked in 100 ml of
deionised water for 10 min. The test dose of alarm
cue was 10 ml of minnow skin extract administered to
the side of the container to induce fin-flicking behaviour. All procedures were approved by the Minnesota
State University Moorhead Institutional Animal Care
Correspondence: B. Wisenden, Biosciences Department, Minnesota State University Moorhead, 1104 7th Ave S, Moorhead, MN 56563, USA.
E-mail: [email protected]
656
doi: 10.1111/eff.12115
Cryptic sampling of chemical alarm cues
and Use Committee (protocol number 10-T-Biol-009N-N-C/D). Movements of moss fragments or clay particles were recorded by a video camera (Casio EX-F1)
positioned directly overhead (moss) or in front of the
aquarium (clay), which captured particle motion at a
rate of 60 frames per second. Motion analysis was carried out using Logger Pro software (version 3.86).
Moss particles positioned on the sides of the minnow’s head, and flanks were swept forward and
upward past the nares by water currents generated by
flicking motions of the pectoral fins (Fig. 1). Viewed
from the side, the thrust of water generated by the
pectoral fins could be seen to create two vortices, one
above and one below the snout, which drew water
from the water column towards the nares. As pre-
dicted, fin-flicking behaviour resulted in making
chemical information in the surrounding water available to olfactory receptors in the nares that would not
otherwise be accessible without conspicuous swimming movements. Similar behaviour has been
observed in other aquatic taxa (e.g., Breithaupt
2001). In fishes, there are three similar behavioural
solutions to this trade-off reported in the literature.
The first is buccal pumping, whereby fish remain
motionless but increase rate of gill ventilation to
generate water currents about the head and nares
(Commens & Mathis 1999). Secondly, alarmed darters, a benthic percid that dwell primarily in the layer
of laminar flow, engage in head-up behaviour in
which the back is arched and the snout extended
Fig. 1. Top view and side view of path of individual particulars of java moss or clay as revealed from frame-to-frame motion tracking at
0.02-s intervals (generating a linear series of small dots). The particle tracks reveal water currents generated by flicking motions of the pectoral fins following exposure to chemical alarm cues. Arrows indicate direction of flow.
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Sutrisno et al.
upward into the overlying region of faster water flow
(Wisenden et al. 1995). A third behavioural solution
is head-bobbing behaviour by the starry goby Asterropteryx semipunctatus (R€uppell 1830) that may also
serve to facilitate olfactory sampling of the water column (Smith 1989). In the field and in laboratory fluvaria, minnows in flowing water exploit flow to
sample chemical information about predation risk
from a safe distance downstream. In the absence of
flow, fish sample chemical information from close
range relatively near to the course of danger, illustrating the fitness value of access to chemical information about risk (Wisenden et al. 2010).
Some cichlids engage in fin-flicking as a warning
signal to their young (Cole & Ward 1969; Shennan
et al. 1994), but this signalling behaviour is maintained at least in part via kin selection by genes
shared between parents and offspring. Minnows and
characins form shoals of unrelated individuals. In this
context, fin-flicking provides public information
about the presence of predation risk (Wisenden &
Chivers 2006) to both nearby conspecifics and
predators (Brown et al. 1999). The most parsimonious account of the evolutionary sequence for visual
signalling is that fin-flicking first arose as a means of
cryptic sampling of chemical cues benefitting the finflicker and only secondarily became co-opted as a
component of a visual signalling system.
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