Location, location, location – finding a suitable home in amongst the

noise

Jenni Stanley, Craig Radford & Andrew Jeffs

Post-doctoral Fellow

BackgroundFinal stage of larval development in

benthic marine organisms involves selecting a suitable settlement habitat.

Involves specific cue or combination of cues

Physical Chemical

Can be both general and species specific

Settlement and Metamorphosis

Not the same process

Tightly coupled in biofouling organisms

Capability of “delaying metamorphosis” in some species

Ecological costs because it extends time in the plankton

Physiological costs as it reduces post-metamorphic growth rate

Crab Settlement Studies Most crab studies that have occurred in the last decade

Blue crab (Callinectes sapidus) Common mud crab (Panopeus herbstii) Fiddler crab (Uca pugnax) Estuarine mud crab (Rhithropanopeus harrisii)

Focus on cues that shorten or lengthen time to metamorphosis (TTM)

In brachyuran crabs TTM can be shortened by 15 – 25% with exposure to chemical cues (Forward Jr. et al., 2001)

Ambient Underwater Sound

Composed of a wide range of frequencies Abiotic 50 – 1000 Hz – wind and waves Biotic 50 – 50,000 Hz – biological Anthropogenic – infrasound to ultrasound – human activities

The major component of the sound emitted from a reef is produced by the inhabitants

A cue which communicates a lot of habitat information would be of great value to larval settlers

Unique Habitat SignaturesSignificant differences in ambient sound

associated with different coastal habitats in subtropical New Zealand

Differences in acoustic profiles due to fish communities and benthic characteristics.

Unique Habitat Signatures

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Fringing Reef

Lagoon

Back Reef

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Perc

enta

ge P

rms2

Time

Fringing Reef

Unique Habitat Signatures

Lagoon

Back Reef

Unique Habitat Signatures

Fringing Reef Lagoon Back Reef

Ambient underwater sound may act as a long distance orientation cue as well as a settlement cue

Jeffs et al., 2003; 2005; Simpson et al., 2005; Radford et al., 2007; Stanley et al., 2010

Ambient Underwater Sound Studies

Induction of settlement in crab megalopae by different habitat sound signatures

Aim:Investigate the influence that sound signatures from different habitat types have on triggering settlement behaviour and/or shortening TTM

Four habitat treatments: distinct acoustically and biologically

Continuous frontal fringing coral reef Isolated back reef habitat interrupted with areas of sand and

coral rubble

Sandy bottomed lagoon

Silent (control)

Methods - Laboratory Based Experiments

Back Reef

0 6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96102

108114

120126

132138

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Frontal Reef

Back Reef

Lagoon

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Silent

Lagoon

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Results – Laboratory-based experiments

48/10248/114

60/13872/138

Reduction of 33%

30/8436/108

66/12066/120

Reduction of 47%

Perc

enta

ge m

etam

orph

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Time (h)

Cymo andreossyi

Grapsus tenuicrustatus

Silent

Lagoon

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100Frontal Reef

Back Reef

Results – Laboratory-based experiments

Perc

enta

ge m

etam

orph

osed

Time (h)

Schizophrys aspera

24/4824/60

42/7842/84

Reduction of 33%

Methods - Field Based Experiments

Isolated back reef habitat interrupted with areas of sand and coral rubble

Sandy bottomed lagoon

Two Habitat treatments: distinct acoustically and biologically

Lagoon

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Back Reef

Lagoon

Results – Field-based experiments

Perc

enta

ge m

etam

orph

osed

48/8748/144

Reduction of 29%

48/8748/159

Reduction of 32%

Grapsus tenuicrustatus

Cymo andreossyi

Time (h)

0 15 24 39 48 63 72 87 96 120 135 144 159 174 183 1980

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Back Reef

Lagoon

0 15 24 39 48 63 72 87 96 120 135 144 159 174 183 1980

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Back Reef

Results – Field-based experiments

Perc

enta

ge m

etam

orph

osed

48/8748/159

Reduction of 25%

Time (h)

Schizophrys aspera

ConclusionsSimilar results in both tropical and

temperate species

Clear preference for optimal adult habitat type

Ability to discriminate habitat by sound signatures

The acoustic cue mediates an endogenous physiological development process

Remote habitat identification using acoustic cues

Integration of all the available cues now needs to be investigated

Acknowledgements

Thanks To:Associate Professor Andrew JeffsDr Craig RadfordNZMSS Student Research FundingLeigh Marine Laboratory Staff and studentsLizard Island Research Station Staff and visiting students