DISPATCHES
Photo: Solveig Østerø SchrøderPhoto: John TurnbullNO PHENOTYPE PLASTICITY FOR
FLOODED OYSTERCATCHERS
The Eurasian oystercatcher (Haematopus ostralegus) is a ground-
nesting shorebird that breeds on salt marshes and beaches close to
the estuarine intertidal flats on which they feed. During breeding
season, they are at risk from flood events that wash away eggs and
drown chicks. Scientists are exploring whether these birds respond
to sea-level rise and changing wind and storm patterns that are
increasing the frequency of extreme climatic events (ECEs), and
whether they exhibit phenotype plasticity in response. Phenotypic
plasticity may allow individuals to respond pre-emptively to ECEs
or to adapt to extreme conditions through intra-generational
behavioural or physiological change. For example, in 2002, Grieco et
al. found that nesting blue tits (Cyanistes caeruleus) changed their
laying date based on food availability the previous spring, and in
2010, Greenlees et al. found that even after a single encounter with
the poisonous cane toad, Australian marbled frogs (Limnodynastes
convexiusculus) learned to avoid them. ECEs are unlikely to prompt
such ‘learning’ if they occur infrequently over the lifespan of the
animal, but Eurasian oystercatchers are a long-lived species, with
a generation time of 11–13 years. They form stable pair bonds
and show strong site fidelity. Pairs return to the same territory year
after year in May and June to breed, the female laying eggs in
several nest cups that the male creates. Liam Bailey and colleagues
examined over 20 years of population data for oystercatchers on
the Dutch barrier island of Schiermonnikoog. Despite 51% of
nests over the course of the study being located on sites that were
inundated during the breeding season, they found no evidence that
oystercatchers were increasing the elevation of their nest sites as a
learned response to ECEs, nor was there any evidence of a response
to environmental cues in the lead-up to a flood event (such as
earlier laying dates or shortened incubation periods). This may be
a reflection of the unpredictable nature of extreme events or of
other counter-acting selective pressures that discourage increasing
nest elevation. It might be that longer-term directional selection will
eventually favour higher nest elevation (the study found that mean
nest elevation did increase over time, but only at half the rate of
maximum high-tide increase); however, in the short term, in the
absence of phenotype plasticity, increased flooding events could
pose a serious threat to the viability of this species and of similar
ground-nesting shorebirds.
Bailey, LD, et al. 2017. Phil. Trans. R. Soc. B. DOI: 10.1098/rstb.2016.0139
GENOME GUIDES
CROWN-OF-THORNS BIOCONTROLThe crown-of-thorns starfish (COTS) is an extremely fecund mass
spawner that is predisposed to population outbreaks, threatening
coral reefs. Water-borne signals probably guide adults to form
aggregations before a synchronised spawning event, meaning these
attractants have substantial potential as biocontrol agents. Michael
Hall and colleagues sequenced the genome of COTS from the Great
Barrier Reef and from Okinawa, Japan, to identify the gene products
underlying this species-specific communication. They identified
proteins that are secreted by external tissues, including the spines,
body wall and mouth, that when exposed to naïve, normally
sedentary COTS caused them to become highly active and move in
the direction of the source. Of these proteins, 26 were ependymin-
related proteins (EPDRs) that have been shown to have rapidly
evolved to give rise to species-specific communication. These EPDRs
provide a potential basis for the development of peptide mimetics
that can be used for future biocontrol measures, including mass
attraction to facilitate efficient collection and removal. The genome
of Australian and Japanese COTS showed high similarity, indicating
that genome-based mitigation strategies developed for one locale
could be applied throughout the species’ range.
Hall, MR et al. 2017. Nature. DOI: 10.1038/nature22033INK, BITE AND FIGHT: WILD
CUTTLEFISH COURTINGObservations made by Justine Allen and colleagues off the coast of
Turkey have found that male European cuttlefish (Sepia officinalis)
aggressively guard females and fend off other males with elaborate
visual and physical behaviours. The mating and courtship rituals of
this species have been observed previously in laboratory settings,
but have never before been recorded in the wild. Chromatophore
organs in the skin make S. officinalis capable of rapid changes in
pigment and appearance. Males typically determine the gender of
others within their species by engaging in an intense ‘zebra’ display- a visual signal-response system that sees them adopt a striped
pattern that is mirrored by other males but not by females. In
1996, Adamo and Hanlon found that aspects of this display could
predict whether an encounter between two males will escalate to
a fight, specifically the level of dark colouration around the eye
and on the face. Allen et al. recorded consort mate guarding and
fighting behaviour in cuttlefish in the Aegean Sea, taking images
with a Canon DSLR camera and a FlipCam compact camera and
then comparing and analysing zebra banding and aggressive
behaviour. They observed a male mate with and then act as consort
to a female before being challenged by a second male. Violence
escalated progressively in stages, with aggressive acts including
extending the fourth arm towards the other male, inking and
jetting, grappling, barrel rolling and biting. Actions were overall
more violent than those observed in a laboratory setting.
Allen J, et al. 2017. The American Naturalist. DOI: 10.1086/692009
48 | Wildlife Australia | SPRING 2017