spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

First published online May 1, 2009
Journal of Experimental Biology 212, 1463-1476 (2009)
Published by The Company of Biologists 2009
doi: 10.1242/jeb.028381
This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Supplementary Material
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in JEB
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Harley, C. M.
Right arrow Articles by Ritzmann, R. E.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Harley, C. M.
Right arrow Articles by Ritzmann, R. E.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

Characterization of obstacle negotiation behaviors in the cockroach, Blaberus discoidalis

C. M. Harley*, B. A. English and R. E. Ritzmann

Department of Biology, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106, USA


Figure 1
View larger version (34K):
[in this window]
[in a new window]

  		Fig. 1. (A) Block climbing behavior: approaching the block (i), swinging the leg to climb (ii) and climbing (success) (iii). (B) Ethogram of block climbing in the light. Arrows represent a direct transition from one behavior to the next. The number on the arrow and its thickness represent the frequency of that transition. This was calculated by dividing the number of times a specific transition was made by the total number of transitions exiting a specific element. All behavioral sequences begin with the cockroach approaching the block (approach). It can then turn around and walk away from the obstacle (return) before or after antennal contact (antennal contact). The cockroaches would then enter a climbing sequence (climb), which could either be successful, with their foot reaching the top of the obstacle (success), or not be successful (miss). In the event that the cockroach missed, it would then produce another climbing motion, which again could either be successful or not. The end of the behavioral sequence occurred when the cockroach climbed the block. The beginning and end of the sequence must be `approach' and `end', respectively, for this reason these elements are represented in bold. This sequence represents the responses of 58 individuals (one trial per individual).

 

Figure 2
View larger version (21K):
[in this window]
[in a new window]

  		Fig. 2. Distance from obstacle, and climbing success. (A) Success is dependent on the distance from the block. The horizontal straight line distance was measured between the cockroach and the obstacle at the beginning of each climbing attempt. Climbing attempts were categorized as success or miss. The data from 88 steps by 58 individuals are represented as a histogram. The distance from the obstacle for successful attempts is significantly less than that for unsuccessful attempts [P<0.0001, generalized estimating equation (GEE)]. Statistics were performed on raw data. (B) Shortening antennae results in cockroaches getting closer to the block before climbing. Mean distance from the block on first attempts in sham (white), short (gray) and bilateral (black). Each individual performed up to four trials. The horizontal distance was measured in the same manner as in A. The number of trials (n) and number of individuals (N) is as follows: sham (n=36, N=14), short (n=42, N=15) and bilateral (n=31, N=14). Individuals with bilateral antennectomies were significantly closer than individuals with short antennae and shams (P<0.001, GEE). Individuals with short antennae were significantly closer to the block than shams (P<0.001, GEE). (C) Shortening antennae changes success for first attempts. Black bars indicate bilateral antennectomies (n=40, N=16), gray bars indicate shortened antennae (n=57, N=15) and white bars indicate shams (n=35, N=14). The first climbing attempt made in each trial of each individual is counted as either a success or a miss, calculated as the percentage of first attempts that are misses for a given individual. No significant differences existed between light and dark. Individuals with shortened antennae miss less than shams (P<0.05 Tukey means comparison) and individuals with bilateral antennectomies (P<0.001, Tukey means comparison). Individuals with bilateral antennectomies miss more often than shams in (P<0.01, Tukey means comparison). Letters in B and C indicate the independence of statistical comparisons whereby if two conditions were not significantly different they would share the same letter.

 

Figure 3
View larger version (11K):
[in this window]
[in a new window]

  		Fig. 3. Strategies used for block climbing in sham (striped), short (gray) and bilateral antennectomies (black). There is no significant difference between the distribution of climb strategies in individuals with short antennae and shams but there is a significant difference between both of these groups and bilateral antennectomies (P<0.001, Pearson's {chi}2 test). Each animal performed up to four trials, which may have contained more than one climbing attempt. The number of trials (n), number of measured climbing attempts and number of individuals (N) are as follows: sham (n=36, attempts=56, N=14), short (n=42, attempts=46, N=15) and bilateral (n=31, attempts=48, N=14). Despite the fact that by definition they contain more than one climbing swing, elevator strategies were only counted once.

 

Figure 4
View larger version (18K):
[in this window]
[in a new window]

  		Fig. 4. Ethograms of block climbing in sham (A), shortened antennae (B) and bilateral antennectomy (C) cockroaches under light conditions. Arrows represent a direct transition from one behavior to the next (behaviors described in Fig. 1). The number on the arrow and its thickness represent the frequency of that transition. Broken squares and circles represent regions, which will be focused on within the paper. Each individual performed up to four trials; number of trials (n) and number of individuals (N) is as follows: sham (n=36, N=14), short (n=42, N=15) and bilateral (n=31, N=15).

 

Figure 5
View larger version (40K):
[in this window]
[in a new window]

  		Fig. 5. Shelf climbing and tunneling is related to antennal contact. (A) Pictures of climbing (i) and tunneling (ii) behavior. Ethograms of shelf behavior in the light (B) and dark (E). Arrows represent a direct transition from one behavior to the next. The number on the arrow and its thickness represent the frequency of that transition (behaviors are described in Fig. 1). Dotted lines were used when two or fewer individuals preformed a specific transition. Antennal position relative to the shelf was determined as being both over the shelf (over/over), both under the shelf (under/under) or if one antenna contacted the top of the shelf and the other contacted the underside the pattern was recorded as (over/under). Either the first [(C,F) initial antennal contact] or last antennal contact [(D,G) ultimate antennal contact] with the shelf prior to climbing or tunneling was recorded. For over/under initial antennal contacts, the following contact pattern was also recorded. This situation always resolved such that both antennae were on one side. Usually the two antennae contacted the shelf around the same time. In cases when one antenna contacted the shelf first on one side then the opposite before the second antenna could contact the shelf, that contact was scored the same as if one antenna contacted the top of the shelf and the other contacted the underside. Data for light (B–D) represents 58 sequences from 56 individuals (14 climbs and 42 tunnels). Data for dark (E–G) represents 86 sequences from 86 individuals.

 

Figure 6
View larger version (19K):
[in this window]
[in a new window]

  		Fig. 6. The influence of shelf height and ambient lighting on climbing behavior. (A) Climbing and tunneling in insects presented with a shelf under different ambient lighting conditions. Naïve cockroaches were placed in the experimental arena with an obstacle they could climb over or tunnel under. The light condition represents 56 trials (14 climbs and 42 tunnels). The dark condition represents 61 trials (26 climbs, 35 tunnels). The error bars in this and subsequent figures represent the ± standard deviation (±s.d.) (calculated using methods for binomial data). In the light, the climbing and tunneling percentages are significantly different (P<0.01, {chi}2 test). In the dark, this difference is not significant (P>0.5, {chi}2 test). (B) Prevalence of climbing with different shelf heights. The open circles represent the light condition whereas the closed circles represent the same behavior under dark conditions. Individuals faced multiple shelf heights but were not exposed to a single height more than once. All responses from all individuals were averaged to create a percentage response. When examined as a whole distribution, the light and dark distributions are significantly different at P<0.05 [generalized estimating equation (GEE)]. The effect of shelf height on climbing proportion is significant (P<0.001, GEE). When examined individually, points at 10.8, 11 and 11.7 mm differed significantly from their counterparts in the opposite lighting condition (P<0.001, GEE). Square symbols represent data from the shelf height used to create the ethogram (Fig. 5A,D) and represents 58 naïve individuals for the light and 86 naïve individuals for the dark.

 

Figure 7
View larger version (19K):
[in this window]
[in a new window]

  		Fig. 7. Ocelli determine if it is light or dark. Each individual performed at least two and up to four trials. Climbs were scored as 1 and tunnels were scored as 0. The trials for each individual were then averaged to get the individual's response. The mean response of all individuals was then averaged creating the mean percentage of climbs (y axis). All experiments were preformed in both the dark (black) and light (gray) conditions. One day before the start of any trials, the eyes were covered with translucent wax (A) sham eye covering or carbonized wax, (B) ocelli covering, (C) compound eye covering and (D) compound eye and ocelli covering. Squares on B, C and D represent the sham light (gray) and dark (black) responses. Closed circles in A represent our ethogram data for naïve individuals in light (gray, n=56) and dark (black, n=86). Both shams (A) and compound eye covering (C) showed a significant difference in climbing proportion between the light and dark conditions (P<0.05, ANOVA, Tukey means comparison). This was not present in ocelli (B) or coverings of both the compound eyes and ocelli (D). Light values for the ocelli (B) and combination compound eye and ocelli (D) coverings were significantly different than that of the shams (A) [P<0.01, generalized estimating equation (GEE) and P<0.001, GEE, respectively]. Compound eye coverings and shams were not found to be significantly different (P<0.24, GEE). The error bars represent ± standard deviation (±s.d.).

 

Figure 8
View larger version (33K):
[in this window]
[in a new window]

  		Fig. 8. Antennae sample the same space regardless of lighting. Naïve cockroaches were placed in the empty arena (A,B) or in the arena when a block obstacle was present (C,D). Vertical movements of the antenna ipsilateral to the camera (occurring prior to antennal contact with the block when it was present in the arena) were digitized. This is presented above in black where the angle is the angle between the antennal tip, antennal base, and the most posterior point on the abdomen (to approximate the body axis). To calculate distance from the origin, the antennal movements were divided into 5 deg. bins. The proportion of each trial represented by a given bin was calculated. These proportions were then added together for the individuals with a given treatment to approximation the amount of time spent in a given region of space. The circular means are represented by the dotted white line and standard deviations by the gray triangle. No significant differences were found between the means or variances of treatment groups (ANOVA). Means and standard deviations (±s.d.) are as follows: empty arena light, mean=179.6 deg., s.d.=46.3 deg.; empty arena dark, mean=173.1 deg., s.d.=26.8 deg.; block light, mean=172.7 deg., s.d.=38.9 deg.; block dark, mean=175.3 deg., s.d.=26.1 deg.

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2009