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Individual Recognition and Memory in Homurus americanus Male

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					                                                            CHEMORECEPTION   AND      BEHAVIOR                                                       253

should be due mainly to the different slopes. The spike frequency            discrimination could be very useful for orienting and tracking in a
(and rise time) during this portion of each slope was 3.1 Hz (1800           fluid environment, because so much physical information about the
ms) for the Low slope, 5.5 Hz (980 ms) for the Medium slope, and             plume and odor source is present in the distribution of slopes in the
70 Hz (160 ms) for the High slope. Once the concentration stopped            eddy field (4). In this study, single cells could discriminate be-
rising, cells adapted to the constant background within a couple of          tween a range of odor onset slopes with rise times similar to those
seconds. We note that the lack of a response to the second slope             measured in laboratory studies of jet plumes (1, 4). In general,
rise in the Medium slope (middle panel between 7 and 8 seconds)              animals may have different chemoreceptor cells “tuned” to partic-
of Figure 1 may be due to the large fluctuations in the output of the        ular ranges of pulse characteristics, such as frequency, height,
piston pumps preceding this rise. These periodic fluctuations                length, and slope (1, 2, 3).
(some of which exceed 5 /J,IVQwould cause cumulative adaptation                  Thanks to D. Mellon and G. Gomez for helpful discussions.
in the chemoreceptor cell such that the overall response is de-              Supported by NSF grant IBN-9723542 to JA and a B.U.M.P.
pressed (5). Because spike adaptation can occur rapidly, beginning           Humes alumni Award to EZ.
within 500 ms of the stimulus presentation, a steeper onset slope
may minimize adaptation and provide the highest frequency for a
given concentration. We will not discuss here the intracellular                                           Literature    Cited
signal transduction pathways that may be involved in the excita-             1. Atema,      J. 1996.   Bid. Bull. 191: 129-138.
tion and adaptation phenomena observed.                                      2.    Borroni,   P., and J. Atema. 1988. J. Comp. Physiol. A. 164: 67-74.
    These preliminary results demonstrate the feasibility of deliver-        3.    Gomez, G., and J. Atema. 19%.         J. Exp. Biol. 199: 1771-1779.
ing measured concentration slopes and provide initial evidence               4.    Moore, P., and J. Atema. 1991.       Biol. Bull. 181: 408-418.
that chemoreceptor cells can act as “slope detectors.” Odor slope            5.    Voigt, R., and J. Atema. 1990.     J. Comp. Physiol. A. 166: 865-874.



Reference:   Biol. Bull.   197: 253-254.   (October 1999)


           Individual Recognition and Memory in Homurus americanus Male-Female Interactions
    Cristin Berkey’ and Jelle Aterna (Boston University Marine Program, Woods Hole, Massachusetts 02543)

   Individual    recognition and memory have been studied in Ho-              show a definite loser and winner after the first 20-min period was
rnarus   americanus,     the American lobster. It has previously been         disqualified and the fight was not included in the data analysis.
demonstrated, through lobster boxing matches, that males can                     The fights were scored using a pre-established scale of agonistic
recognize individuals. When a male encounters the same male it                levels (1) with some additions made for differences that arose as a
lost to previously, it avoids a new fight. The same animal will fight         result of the fights being between males and females. An agonistic
on subsequent occasions if presented with an unfamiliar opponent              level was assigned to each animal every 5 s. The levels ranged
(1). The ability to recognize a previous opponent lasts for up to a           from -2 to 5, with -2 demonstrating fleeing behavior and 5
week, and it is based on olfactory recollection of the opponents’             demonstrating claw snapping or claw ripping at the opponent. An
urine (2). The same results have been obtained in female-female               overall agonistic scale was calculated for each animal in each fight
encounters (3). We therefore hypothesize that male-female pairs of            by summing all of the agonistic values. A fight was determined to
Homarus     americanus      can also recognize individuals, as demon-         be over when one animal ceased to show an agonistic level above
strated by shorter periods of fighting on the second encounter with           one. In this way, the duration of each fight was scored. To prevent
familiar individuals.                                                         bias during analysis of the behavioral tapes, the scorer was blind to
    Males and females were paired by carapace length, with no pair            whether the tapes were from a first or second fight.
differing by more than 3 mm. It was also ensured that in all                     In group A, 10 pairs of fights were carried out. Significantly, in
matched pairs, the animals had not previously met. Animals were               9 out of 10 instances, no fighting occurred on the second encoun-
kept in isolation for 24 h before their first boxing match and for the        ter; fighting did occur in the tenth case. In group B, 13 pairs of
24 h between the first and second matches. All boxing matches                 fights were carried out. Two sets were disqualified because there
took place in a 240-I glass aquarium and were videotaped. One                 was no clear winner after the first fight. In 3 out of 11 instances, no
male and one female were placed in the tank and separated by a                fighting occurred on the second encounter. In 8 instances, fighting
removable, opaque divider. The lobsters were allowed to acclimate            occurred. The fraction of times in which fighting occurred on the
for 10 min before the divider was removed, and then allowed to                second encounter is significantly different between the two groups
interact for 20 min. There were two sets of fights, group A and               (P < 0.005 .x? = 8.416 df = 1).
group B. In group A, the same pair of animals fought twice. In
                                                                                 When a fight was between familiar opponents, the aggression
group B, the animals were rotated so that each animal met a new
                                                                             level of the loser was significantly lower in the second boxing
opponent in the second fight. In both sets, the first and second
                                                                             match than in the first boxing match (P < 0.05 paired t test).
fights were separated by 24 h. Any pair of animals that did not
                                                                             However, for unfamiliar opponents, the aggression level of the
                                                                             loser was not significantly lower in the second boxing match than
  ’ Tufts University, Medford, Massachusetts.                                in the first (paired t test). The aggression level of the winner was
 254                                          REPORTS           PROM   THE   MBL   GENERAL     SCIENTIFIC      MEETINGS

not significantly different between the two fights in either group A                    determines the end of the fight: in male-female pairs, females
or group B (paired t test).                                                             typically lost.
    We observed two behaviors that had not previously been seen in                         The fact that second encounters were much shorter, to the point
either male-male (1) or female-female (3) matches. One of these                         that no fighting occurred, supports the hypothesis that male and
was mounting behavior, which typically occurs just prior to mating                      female lobsters can recognize each other as individuals. The results
 (4): the male climbs on the back of the female and attempts to turn                    also demonstrated differences, such as nonreactive contact and
her onto her back using his first two pairs of walking legs and his                     mounting behavior, in the way male and female lobsters interact
third maxillipeds. In our encounters, however, this mounting be-                        within the boxing match situation, compared to male-male and
havior never progressed to actual mating. We observed male-                             female-female interactions. It is possible that these differences
female mounting behavior in five separate encounters, two of                            parallel the natural interactions between male and female lobsters.
which involved the same pair of animals. A second form of                               Females are allowed to enter male shelters, whereas other males
behavior not seen in same-sex boxing matches was nonreactive                            are not (5). Therefore, males and females must be capable of being
contact. This included any situation in which the two animals were                      near to each other without demonstrating aggressive behavior.
in physical contact but did not seem to be reacting to each other.                         Financial support from NSF-REU (OCE-9605099           site award
The average time spent in contact across the 42 fights analyzed                         to Boston University). We thank Leslie McLaughlin,           Jennifer
was 179 s per 20-min fight. This value had no obvious correlation                       Walters, and Dr. Frank Grass0 for their assistance with this project.
with previous exposure to the opponent. In addition to the differ-
ences already mentioned, fight duration in first encounters was
significantly shorter in male-female fights than in male-male fights                                                Literature      Cited
(P < 0.05, t test). The average fight duration was 250 s (SE ? 50 s)
                                                                                         1. Karavauich,      C., and J. Atema. 1998.     Anim. Behav. 56: 1553-1560.
in male-female pairs, but 457 (SE + 73 s) in male-male pairs (1).                       2. Karavanich,       C., and J. Atema. 1998.      Behaviour   135: 719-730.
However, there was no significant difference in fight duration                          3. Atema, J., T. Breithaupt,        A. LeVay, J. Morrison,    M. Mallidis,  and
between male-female and female-female first fights: the average                             M. Edattukaran.        1999.   Chem. Senses (in press).
fight duration in female-female pairs was 206 s (SE ? 73 s) (3).                        4. Atema, J., and D. G. Engstrom.          1971.   Nature 232: 261-263.
The similarity in fight duration between female-female and male-                        5. Bushmann,        P., and J. Atema.    1997.   Can. J. Fish. Aquat. Sci. 54:
female pairs is consistent with the observation that the loser                              647-656.




Reference:   Bid.   Bull.   197: 254-255.   (October    1999)


     Urinary  Protein Concentration    in Connection with Ago&tic       Interactions in Homuncs americanus
                Leslie C. McLaughlin’,   Jennifer Walters2, Jelle Atema, and Norman Wainwright
     (Boston University Marine Program, Marine Biological Laboratory, Woods Hole, Massachusetts 02543)


    Homarus   americanus,    the American lobster, relies heavily on                       Twenty-three wild-caught female lobsters (79-83 mm carapace
chemical signals as a source of information (1). Urine in particular                    length) were used. They were kept in groups of 5 to 15 in 400-l
has notable behavioral effects on these animals, suggesting that it                     communal tanks with flow-through seawater and artificial shelters
is an important source of chemical information, specifically in                         made from PVC pipe. All lobsters were healthy and fed squid
social communication. Lobsters store urine and, in different be-                        twice a week. Lobsters were isolated in individual aquaria 48 h
havioral contexts, release it from two paired, frontally facing                        before their first agonistic encounters with unfamiliar lobsters,
nephropores into their gill current (2, 3). Previous studies (4, 5, 6)                 following Karavanich and Atema (4). Isolated lobsters were fed a
have shown that lobsters recognize conspecifics as individuals for                      small piece of squid at least 1 h before each interaction. All
at least 24 h and up to a week after one 20-min staged agonistic                       agonistic interactions took place in a 240-l glass aquarium that was
interaction. Both urine release and antennular chemoreception are                      rinsed and filled with unfiltered seawater immediately before each
necessary for this recognition (7). Evidently lobster urine carries a                  lobster interaction. Two female lobsters unfamiliar to one another
chemical signal that allows for individual recognition among an-                       were placed in the aquarium on either side of a removable, opaque
imals; the challenge is to identify the chemical composition of the                    divider and were allowed 10 min to acclimate to their new sur-
signal. One candidate is the proteinaceous content of the nephro-                      roundings. To initiate the encounter, the plastic divider was raised
pore gland (8). We set out to study protein concentration in the                       and the lobsters were allowed to interact for 20 mitt, after which
urine of lobsters subjected to two agonistic encounters separated                      they were returned to their respective isolation tanks. Twenty-four
by 24 h.                                                                               hours later this procedure was repeated: about half (n = 13) of the
                                                                                       animals were exposed to the same lobster they had encountered the
  ’ Brown University, Providence, Rhode Island.                                        day before; the other half (n = 10) were paired with an unfamiliar
  * Oregon State University, Corvallis, Oregon.                                        lobster. All encounters were videotaped for later analysis.

				
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