Antisocial arthropods

Antisocial arthropods Bella Dubnicka, Ashley Ehlert, & Haley Krachman

The Caribbean spiny lobster is a part of a million dollar fisheries industry in the Florida Keys. Their attraction to conspecific odor and den sharing abilities facilitate their capture.

However, over the past 20 years, spiny lobster conspecific odor attraction has been decreasing.

Figure 1. Historical data of the decrease in conspecific odor attraction with the constant rate of den sharing.

To gain a better understanding of these changes, we carried out a field experiment and laboratory experiment to test the plasticity and influence of the environment on den sharing behavior.

Experiment 1: Den sharing behavioral training

16 conspecific lobster pairs were assigned to social and asocial treatment groups. Lobsters in the social treatment group were given a high quality food reward if they exhibited den sharing behaviors. Lobsters in the asocial treatment group were given high quality food rewards if they did not exhibit den sharing behavior.

Figure 2. Laboratory den sharing experiment results. Lobsters started out at a 40% den sharing rate which significantly diverged at week 5, with social lobsters increasing their den sharing and asoical lobsters decreasing their den sharing. This divergence did not last long; both treatment groups ended up sharing dens only 10% of the time.

This experiment indicates that lobster den sharing behavior is plastic in the laboratory setting.

Experiment 2: Conspecific odor attraction

We next explored if the den sharing training experiment was successful using a Y-maze trial to test conspecific odor attraction of the lobsters. We expected that the training experiment would influence the social lobsters to choose to be with each other in the Y-maze based on conspecific odor. We also expected that the training experiment would influence the asocial lobsters to not be on the same size of the Y-maze.

Figure 3. Indicates that rearing treatment had no effect on conspecific odor attraction. (p=0.7046)

Ultimately, den sharing in the lab was not correlated with conspecific attraction. This was another indication that lobster den sharing behavior was plastic.

Experiment 3: Field study of lobster environmental behavior

36 lobsters from Burnt Point in the Florida Keys were tagged and allowed to roam in a hexagonal field. Substrate composition and conspecific density was recorded by divers on the reef.

Figure 4. Shows the location of the field site and an example of the hexagonal field.

Figure 5. Graph of substrate type in Burnt Point indicates that hardbottom substrate type was strongly correlated to the amount of den sharing behavior in the field (p=0.0034).

Den sharing in the field was not correlated to lobster density but was correlated to the substrate type, specifically with hardbottom substrate. Hardbottom substrate may provide more opportunities for den sharing because of the presence of solution holes.

Our data indicate conspecific odor attraction has decreased while den sharing behaviors have largely remained the same over the past 20 years, regardless of conspecific density. Lobster behaviors have also proven to be plastic in the laboratory setting. Alternative explanations for the decrease in lobster social behavior may be related to homing behaviors, which is our next area of study.

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