Distance chemoreception in laboratory-reared Sepia officinalis L. and its impact on social behaviour.

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Distance chemoreception in laboratory-reared
Sepia officinalis L. and its impact on social
behaviour.

• Bethany Lloyd
• MSc Marine Biology, University of Wales, Bangor
• Supervisor Chris Richardson

2006
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Aim of Research

• To add to the conflicting pool of data regarding
  chemoreception in S. officinalis and determine
  their ability to detect conspecifics using only
  olfactory cues. Develop techniques in animal
  husbandry and behavioural experimentation.

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Specific Objectives

1. Egg transport, care and hatching
2. Rear juveniles to maturity within 4 months
3. Determine method of using cuttlebone features to
   sex individuals
4. Determine ability of S. officinalis to detect
   other cuttlefish using chemoreception

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Impact of Egg Transport Methods on Hatching
Success

• Acquired eggs from Portsmouth Harbour, UK and
  transported by train to Bangor, UK (8 hours) then
  by car to Menai Bridge, UK (20 min.)
• Tested ability of eggs to withstand possible
  desiccation, lack of oxygen, jostling, and change
  in temperature during transport.

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Methods

• Transport methods for eggs cool boxes with
  various wet/dry conditions
• Rate of hatching success for each of 4 treatments
  (3 replicates each)

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Results

• Eggs hatched between 30 and 58 days after
  transport.

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Results
Treatment Total No. Eggs Number Hatched Average age Hatched
Dry 642 423 64.9 13.1
Damp 609 359 60.1 7.3
Water 671 268 39.4 14.2
Water Air 701 505 72.1 3.1

• Analysis of variance of hatching percentages
  revealed no significant difference among
  treatments (F 1.80, P 0.225, DF 11)

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Discussion

• No significant difference among treatments.
• Practicalities outweigh benefits (water air
  best but potentially costly)
• S. officinalis eggs appear hardy
• Further investigation
• - Clusters of eggs vs. separated eggs
• - Transport over longer distances, shipped
  through postal organizations

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Analysis of Cuttlebones for Sexual Dimorphism

• Sexual dimorphism only outwardly apparent in
  adult animals

• No non-lethal methods for sexing juveniles
  impact on sexual selection studies
• Investigation of report of wider cuttlebones in
  females than in males (Boletzky, 1987)

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Methods

• Width/length ratios
• 16 adult females
• 13 adult males
• 35 juveniles
• AnalySIS software
• Two-sample T-tests

Figure. Ventral view of a cuttlebone of Sepia
officinalis. A the chitinous rim, B
calcareous main body of the cuttlebone, C
measurement of total length, D measurement of
maximum width .
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Results

• Two-factor ANOVA significant difference between
  slopes of regression lines for length/width
  relationship of cuttlebones of adults males and
  females (F 7.17, P 0.013, DF 1)

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Discussion

• Despite significant difference between
  length/width ratios for adult males and female,
  ratios overlap
• Range of ratios for juveniles separate from adult
  ratios
• No practical use of ratios for certainty of sex
  identification in juveniles
• Use of ratios for adults limited

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Accelerated Rearing to Maturity

• Forsythe Effect (Forsythe, 2004)
• Greatest potential for growth in first 2-3 months
  after hatching
• Maturity dependent on size, not age
• Fifteen juveniles reared from 19 - 26C, fed ad
  libitum

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Results

• Maturity at 75mm in mantle length
• 8 juveniles died
• Remaining 7 reached maturity by 78th day of
  experiment approx. 3 months after hatching

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Discussion

• Suggests these could become reproductively active
  within 4 months
• Limitations high mortality rate, infection,
  water quality issues, expensive diet
• Further research impact of fast maturity on
  reproductive behaviour

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Detection of Conspecifics by Chemoreception in a
Y-maze

• Importance of visual displays
• Messengers 1970 study on blinded males
• Conflicting reports (Boal and Golden, 1999
  Messenger, 1968 Boal, 1996, 1997 Boal and
  Marsh, 1998)
• Studies focus on discriminatory chemoreception,
  not presence or absence of ability

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Methods

• Husbandry of animals in established facilities,
  SOS collaboration with Nick Jones, PhD student
• Y-maze designed and built for purpose

Figure Tank design and measurements (in mm) of a
Y-maze constructed at the School of Ocean
Sciences, Menai Bridge, UK for experiments on
chemoreception in Sepia officinalis. A seawater
outflow, B sliding gate moved by
rope-and-pulley system, C choice region, D
partitions with holes for water flow, E divider
to increase the length of the arms. Black
ellipses indicate placement of S. officinalis at
the start of each trial.
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Methods

• Control trials seawater vs. seawater,
  right/left bias
• Experimental trials conspecific vs. seawater
• Scoring 1) arm entered first, 2) latency to
  first entry, 3) arm in which most time spent

Figure Key A sliding gate operated manually by
a rope-and-pulley system, B partition with a
series of holes to allow flow-through of
seawater, C plastic tubing carrying seawater
inflow to both arms of the maze, and D plastic
tubing with a T-joint providing aeration to both
arms
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Results
Trial Choices Subjects
1. Control Left 9
Right 7
No choice 1 (1 aborted)
2. Experimental Left 7
Right 8
No choice 2 (1 aborted)
(Arm with conspecific) (7)
(Arm w/o conspecific) (8)
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Results

• Chi-square goodness of fit, no right/left bias in
  control (X² 0.25, P 0.617, DF 1)
• Experimental trials chi-square revealed no
  significant deviation from control (X² 0.56, P
  0.454, DF 1)
• Only 7 of the 15 chose arm with conspecific
• Observed no Zebra patterns or other outward
  behaviours that might indicate detection

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Discussion

• No suggestion of chemoreception to detect
  conspecifics
• Possible absence of social recognition
• Impact on mate choice based on non-chemical cues

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References

• Boal, J.G. (1996). Absence of social recognition
  in laboratory-reared cuttlefish, Sepia
  officinalis L. (Mollusca Cephalopoda). Animal
  Behaviour, 52, 529-537.
• Boal, J.G. (1997). Female choice of males in
  cuttlefish (Mollusca Cephalopoda). Behaviour,
  134, 975-988.
• Boal, J.G. and Marsh, S.E. (1998). Social
  recognition using chemical cues in cuttlefish
  (Sepia officinalis Linnaeus, 1758). Journal of
  Experimental Marine Biology and Ecology, 230,
  183-192.
• Boal, J.G. and Golden, D.K. (1999). Distance
  chemoreception in the common cuttlefish, Sepia
  officinalis (Mollusca, Cephalopoda). Journal of
  Experimental Marine Biology and Ecology, 235,
  307-317.
• Forsythe, J.W. (2004). Accounting for the effect
  of temperature on squid growth in nature from
  hypothesis to practice. Marine and Freshwater
  Research, 55, 331-339.
• Hanlon, R.T. and Messenger, J.B. (1996).
  Cephalopod Behaviour. Cambridge University Press,
  Cambridge.
• Messenger, J.B. (1970). Optomotor responses and
  nystagmus in intact, blinded and statocystless
  cuttlefish (Sepia officinalis L.). Journal of
  Experimental Biology, 53, 789-796.
• Tinbergen, L. (1939). Zur Fortpflanzungsethologie
  von Sepia officinalis L. Archives Néerlandaises
  de Zoologie, 3, 323-364.
• Dave Roberts, SOS photographer