Distance chemoreception in laboratory- reared Sepia officinalis L. and its impact on social behaviour. Bethany Lloyd MSc Marine Biology, University of.

Distance chemoreception in laboratory-reared Sepia

officinalis L. and its impact on social behaviour.

Bethany LloydMSc Marine Biology, University of Wales, Bangor

Supervisor: Chris Richardson2006

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.

Specific Objectives1. 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

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.

Methods

• Transport methods for eggs – cool boxes with various wet/dry conditions

• Rate of hatching success for each of 4 treatments (3 replicates each)

Results

• Eggs hatched between 30 and 58 days after transport.

ResultsTreatme

ntTotal No.

EggsNumber 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)

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

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)

Methods

• Width/length ratios

• 16 adult females• 13 adult males• 35 juveniles• AnalySIS software• Two-sample T-

testsFigure. 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 .

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)

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

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 - 26°C, fed ad libitum

Results

• Maturity at 75mm in mantle length

• 8 juveniles died• Remaining 7

reached maturity by 78th day of experiment – approx. 3 months after hatching

53%

20%

27%

Mortalities

Mature in 71 Days

Mature in 78 Days

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

Detection of Conspecifics by Chemoreception in a Y-maze

• Importance of visual displays• Messenger’s 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

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.

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

ResultsTrial 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)

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

Discussion

• No suggestion of chemoreception to detect conspecifics

• Possible absence of social recognition

• Impact on mate choice – based on non-chemical cues

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