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Cold Temperature Effects on Byssal Thread
Production by the Native Mussel Geukensia demissa
versus the Non-Native Mussel Mytella charruana

By: Sasha Brodsky | Mentors: Dr. Linda Walters, Dr. Kimberly Schneider, and Dr. Eric Hoffman


Temperature had a significant effect on byssal thread production for both M. charruana (F= 56.73, p<0.0001; Figure 1) and Geukensia demissa (F=10.16, p=0.012; Figure 2). Geukensia demissa had a higher survival rate at 10° C than M. charruana, but M. charruana produced twice as many byssal threads than G. demissa at the highest tested temperature. Also, M. charruana showed a difference in byssal thread production over time while G. demissa did not.

Survival of M. charruana was 100% in the control (23° C) and 13° C treatments. At 10° C, there was 66% survival. At 23° C, M. charruana had a mean of 10.8 ± 1.6 byssal threads per day over seven days (Figure 1A). This was significantly higher (p<0.0001) than the 13° and 10° C treatments, which had 0.05 ± 0.04 and 0 byssal threads per day, respectively (Figure 1A). At 13° C, only 4 of 12 individuals produced byssal threads. Specifically, two mussels produced one byssal thread on one day over the seven day trial, one mussel produced two new threads on two separate days of the trial, and one mussel made three new threads on two separate days.

Results of the one-way ANOVA for the M. charruana trial at 23° C showed that time was a significant factor for production of byssal threads (F= 5.604, p=0.004) (Figure 1B). Byssal thread production on Day 2 was significantly different from Days 1, 4, 6, and 7 (Figure 1B). No other days were different from one another.

Geukensia demissa had 100% survival in all treatments. Temperature had a significant effect on the mean number of byssal threads produced by G. demissa (F=10.16, p=0.012) (Figure 2A). At 23° C, G. demissa produced a mean of 5.78 ± 0.84 byssal threads per day (Figure 2A). This was not significantly different from the number of threads produced at 13° C, which had a mean of 4.26 ± 0.35 (Figure 2A). At 10° C there was a significant reduction in the number of byssal threads produced (mean of 2.90 ± 0.29 byssal threads per day over seven days; p=0.013) from the 23° C treatment (Figure 2A). However, time was not a significant factor for byssal thread production (F=2.072, p=0.081) (Figure 2B).

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