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Behavioural responses of juvenile cuttlefish (Sepia officinalis) to local water movements

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Behavioural responses of juvenile cuttlefish (Sepia officinalis) to local water movements
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   Marine and Freshwater Behaviour and Physiology   June 2005; 38(2): 117–125 Behavioural responses of juvenile cuttlefish( Sepia officinalis ) to local water movements SPOGMAI KOMAK  1 , JEAN G. BOAL  2 , LUDOVIC DICKEL  3 & BERND U. BUDELMANN 1,4 1 School of Medicine, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA, 2 Department of Biology, Millersville University, Millersville, Pennsylvania 17551-0302,USA,  3 Universite´ de Caen, Laboratoire de Physiologie du Comportement des Cephalopodes,14032 Caen, France and   4 Department of Neuroscience and Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555-1069, USA (Received 2 August 2004; in final form 8 March 2005) Abstract Physiological studies have shown that the epidermal head and arm lines in cephalopods are a mechano-receptive system that is similar to the fish and amphibian lateral lines (Budelmann BU, Bleckmann H.1988. A lateral line analogue in cephalopods: Water waves generate microphonic potentials in theepidermal head lines of   Sepia officinalis  and  Lolliguncula brevis . J. Comp. Physiol. A 164:1–5.); however,the biological significance of the epidermal lines remains unclear. To test whether cuttlefish showbehavioural responses to local water movements, juvenile  Sepia officinalis  were exposed to localsinusoidal water movements of different frequencies (0.01–1000Hz) produced by a vibratingsphere. Five behavioural responses were recorded: body pattern changing, moving, burrowing,orienting, and swimming. Cuttlefish responded to a wide range of frequencies (20–600Hz), but notto all of the frequencies tested within that range. No habituation to repeated stimuli was seen.Results indicate that cuttlefish can detect local water movements (most likely with the epidermalhead and arm lines) and are able to integrate that information into behavioural responses. Keywords:  Cephalopods, mechanoreception, lateral line, hearing  Introduction Cephalopods (octopods, cuttlefishes, and squids) have a receptor system that is equivalentto the lateral line system of fishes and aquatic amphibians (Sundermann-Meister 1978;Sundermann 1983; Budelmann & Bleckmann 1988). The system is comprised of lines of polarized epidermal hair cells on the head and arms. The cells are sensitive to local watermovements as small as 0.06 m m (Budelmann & Bleckmann 1988); this sensitivity is close to Correspondence: Jean Geary Boal, PhD, Department of Biology, Millersville University, P.O. Box 1002, Millersville,PA 17551-0302, USA. Fax: (717)872-3905. Tel.: (717)871-4773. E-mail: jean.boal@millersville.eduISSN 1023–6244 print/ISSN 1029–0362 online/00/000117–125 # 2005 Taylor & Francis Group LtdDOI: 10.1080/10236240500139206  that of the hair cells in the fish lateral lines (Bleckmann et al. 1991). Octopods have eight,and cuttlefishes and squids ten, epidermal lines that run in anterior/posterior directionover the dorsal, lateral, and ventral sides of the head and continue onto the arms(in cuttlefishes and squids, two of the lines, one below each eye, are restricted to the head).One additional line is located on the ventral side of the funnel (Sundermann-Meister 1978;Sundermann 1983; Lenz et al. 1995; Lenz 1997).The behavioural significance of the cephalopod epidermal lines remains unclear. Becauseof their similarity to the vertebrate lateral lines, it is reasonable to assume that they areinvolved in functions similar to those known for fishes: prey detection, predator avoidance,the localization of stationary objects, and schooling behaviour (Montgomery & MacDonald1987). Preliminary behavioural experiments have shown that the cuttlefish’s ability to catchshrimp in complete darkness most likely depends on the functioning of the epidermal lines(Budelmann et al. 1991).The present experiments were performed to test whether cuttlefish perceive local watermovements (sinusoidal water oscillations of various frequencies but constant amplitudes)and are able to integrate that information into behavioural responses. Methods Thirty-four juvenile cuttlefish  Sepia officinalis  were used for the experiments. Twenty-fourcuttlefish were one-month old with a dorsal mantle length of 30  1mm; the remaining10 cuttlefish were three-month old with a dorsal mantle length of 57  1mm. All cuttlefishwere hatched and reared under standard laboratory conditions at the National ResourceCenter for Cephalopods in Galveston, Texas (Forsythe et al. 1991).The cuttlefish were exposed to the water movements and the incidences (occurrences)of the following five behaviours were observed:  pattern changing   (change of coloration,texture, or pattern on the head, arms or mantle),  moving   (skin, mantle, head, or armmovements),  burrowing   (small back and forth movements in place similar to those usedwhen burrowing),  orienting   (change in orientation relative to the stimulus but no changeof location), and  swimming   (movements resulting in a change of location). Experimental apparatus and stimulation All experiments were performed in a small glass tank (75  35  35cm) with the four sidesand the bottom covered with black plastic to minimize visual stimulation from the outside.The tank was placed on an air tire to eliminate potential vibrations of the building (e.g.caused by the air conditioning). Sinusoidal water movements of various frequencies wereproduced by a vibrating sphere (diameter 14.6mm) attached to a rod and moved in thedirection of the rod by a vibrator (model 102, Ling Dynamic Systems, Royston, England).The vibrator was driven by a function generator to produce sinusoidal water movementswith constant amplitudes and oscillation frequencies between 0.01 and 1000Hz(Budelmann & Williamson 1994). Each stimulus frequency was applied for 30s, with aninter-stimulus interval of 5min.In each experiment, the cuttlefish were placed individually into a small circular basket(diameter 9cm, formed from a wide-meshed plastic net) suspended in the middle of thetank. During stimulation, the sphere was positioned 5mm above the head of the cuttlefish,directly above the dorsal epidermal lines. Sphere movement (in the range of a fewmicrometers; cp. Budelmann & Williamson 1994) was towards and away from thecuttlefish. Before the stimuli were applied, the cuttlefish were acclimated to the experimental118  S. Komak et al.  apparatus for 60–90min until they were resting calmly on the bottom of the basket andthe body patterns had stabilized for a period of at least 10min. During the experiments,the water circulation of the tank was turned off to eliminate any stimulation side effectscaused by the movement of the circulating water.Preliminary trials using groups of cuttlefish and frequencies ranging from 0.01–1000Hzindicated that the cuttlefish responded to frequencies ranging from 10–600Hz.Frequencies in this range were selected for further testing.For the statistical analyses, behavioural activity was computed as the sum of the incidences of all five behaviours. In Experiment 3, the different behaviouralresponses were also analyzed separately. All statistics were two-tailed unless otherwisestated. Experiment 1 Three cuttlefish (one-month old, already used in preliminary trials) were placed individually into the basket in the experimental tank. The following 19 frequencies were applied: 40, 45,50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 180, 200, 550, 600, and 650Hz. Experiment 2 Six cuttlefish (one-month old, already used in preliminary trials and in Experiment 1) wereindividually placed into the basket and, based on the responses seen in Experiment 1, thefollowing five frequencies were applied: 40, 45, 70, 180, and 600Hz. In addition, thefrequencies 0.01 and 1000Hz were applied as controls because they elicited no response inpreliminary trials. Each frequency was tested five consecutive times to test for possiblehabituation. Experiment 3 Twenty-eight experimentally naı¨ve cuttlefish (one-month old [  N  ¼ 18], three-month old[  N  ¼ 10]) were individually placed into the basket and the following six frequencies applied:20, 45, 70, 180, 300, and 600Hz. Behaviour immediately before ( T  1) and after ( T  3) thestimulation was recorded as well as during stimulation ( T  2) (cp. Figure 1), for furtherclarification of the response. First, the number of cuttlefish showing any behavioural activity (sum of all behaviours) during  T  1,  T  2, and  T  3 was determined. Second, the numberof cuttlefish that responded to stimulation with burrowing, moving, and pattern changingwas determined. Behavioural responses were recorded with a Sony   video camera placedvertically 30cm above the experimental tank. T1T2T330s5minT1T2T330s Figure 1. Stimulation diagram. All frequencies were applied at 5min intervals.  T  1 ¼ 30speriod before stimulation,  T  2 ¼ 30s period during stimulation, and  T  3 ¼ 30s period afterstimulation. Cuttlefish responses to water movements  119  Results In all the experiments, each specific frequency was applied for a duration of 30s; however,almost all responses occurred within the first five to eight seconds of stimulus application. Experiment 1 The following frequencies caused significantly higher activities than during the controlperiod: 40, 45, 50, 65, 70, 75, 80, 85, 180, and 600Hz (repeated-measures ANOVA;  N  ¼ 3,df  ¼ 19,  P  <0.05 all) (Figure 2); five of these frequencies were again tested in Experiment 2.Frequencies of 55, 60, 90, 105, and 200Hz did not cause any significant response. Experiment 2 When stimulated five consecutive times with the same frequency (0.01, 40, 45, 70, 180, 600,or 1000Hz), between one and five of the six cuttlefish responded to each of the fivepresentations of the 40, 45, 70, 180, and 600Hz stimulus (Table I). No habituation torepeated stimulation was seen. **** ****** 01234    0   4   0   4   5   5   0   5   5   6   0   6   5   7   0   7   5   8   0   8   5   9   0   9   5   1   0   0   1   0   5   1   8   0   2   0   0   5   5   0   6   0   0   6   5   0 Fequency (Hz)    A  c   t   i  v   i   t  y Figure 2. Experiment 1 (  N  ¼ 3, mean þ SE ) . Response activity (mean number of behaviouralincidences per cuttlefish; all behaviours combined) to a subset of frequencies; no responses were seenat stimulation frequencies of 55, 60, 90, 105, and 200Hz. Black columns with asterisks (*) show thefrequencies that caused significantly more responses than during the immediately preceding controlinterval ( P   0.05 all). Table I. Experiment 3, individual tests (  N  ¼ 6). Number of cuttlefish responding in each of the five consecutive stimuluspresentations.Stimulus presentationFrequency (Hz) 1 2 3 4 50.01 0 0 0 0 040 3 5 2 2 345 4 2 3 3 370 1 2 3 3 1180 2 2 3 3 1600 4 3 3 2 31000 0 0 0 0 0 120  S. Komak et al.  Experiment 3 The number of cuttlefish responding (all behaviours combined) was statistically higher withstimulation ( T  2) than without stimulation ( T  1,  T  3) for all frequencies applied except for600Hz, which showed no difference between the periods  T  2 and  T  3 (Wilcoxon testfor matched-paired data; one-month old cuttlefish:  Z  <  2.12,  N  ¼ 18,  P  <0.05; three-month-old cuttlefish:  Z  <  2.45,  N  ¼ 10,  P  <0.05; Figure 3). There was no difference in thelevel of activity during the no-stimulus periods  T  1 and  T  3 for any frequency applied.Of the five specific behaviours, only burrowing, moving, and pattern changing (but notswimming and orienting) occurred frequently enough for statistical analysis. Responsesof the two age groups were again similar, except for the behaviour of burrowing.One-month-old cuttlefish showed significantly more moving during stimulation for allfrequencies tested (20, 45, 70, 180, 300, and 600Hz;  Z  <2.5,  N  ¼ 18,  P  <0.05); three-month old cuttlefish showed significantly more moving during stimulation withfrequencies of 45Hz (  Z  ¼ 2.2,  N  ¼ 10,  P  <0.05) and 180Hz (  Z  ¼ 2.0,  N  ¼ 10,  P  <0.05),although the difference between the periods  T  2 and  T  3 was not significant for 180Hz.One-month-old cuttlefish showed significantly more pattern changing during stimulationwith all frequencies tested (  Z  <2.5,  N  ¼ 18,  P  <0.05); three-month-old cuttlefish showedsignificantly more pattern changing with all frequencies other than 600Hz (  Z  ¼ 2.2,  N  ¼ 10,  P  <0.05). One-month-old cuttlefish showed significantly more burrowing with( T  2) than without ( T  1,  T  3) stimulation for the frequencies 20Hz (  Z  ¼ 2.0,  N  ¼ 18, P  <0.05), 45Hz (  Z  ¼ 2.0,  N  ¼ 18,  P  <0.05), 70Hz (  Z  ¼ 2.0,  N  ¼ 18,  P  <0.05), and 180Hz(  Z  ¼ 2.2,  N  ¼ 18,  P  <0.05); three-month-old cuttlefish showed no significant burrowingresponse to any frequency. There was no difference between the periods  T  1 and  T  3 forany age group, frequency, or behaviour tested. (a) ***** 051015200 20 45 70 180 300 600 0 Frequency (Hz)    N  u  m   b  e  r  o   f  a  n   i  m  a   l  s (b) *** ** 051015200 20 45 70 180 300 600 0 Frequency (Hz)    N  u  m   b  e  r  o   f  a  n   i  m  a   l  s Figure 3. Experiment 3. Number of (a) one-month-old (  N  ¼ 18) and (b) three-month-old (  N  ¼ 10)cuttlefish showing behavioural activity (all behaviours combined) during the 30s periods beforestimulation ( T  1, open columns), during stimulation ( T  2, black columns) and after stimulation( T  3, gray columns). The * shows the frequencies that caused significantly more responses duringstimulation ( T  2), as compared with no stimulation ( T  1 or  T  3) ( P   0.05 all). Cuttlefish responses to water movements  121
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