Results and Discussion
Figure 1. Average crawling speed of 5 P. ocellatus during the day (9am) and night (9pm).
Figure 2. Graph showing average crawling speed of 5 P. ocellatus during the day (9am) and night (9pm). p-value <0.05.
Data collected showed a distinct difference in activity rate of all 5 P. ocellatus between the day and night. P. ocellatus did not produce results during night experiment due to the lack of movement. This indicate that P. ocellatus is diurnal and totally inactive at night.
A similar study was conducted by a fellow classmate (Sirada Oratanachai, 42281500) on another sacoglossa, Thuridilla bayeri. T. bayeri are very closely related to P. ocellatus, and they can be found in the same family – Plakobranchidea.
Figure 3. Picture of a T. bayeri.
Comparison of crawling speed from P. ocellatus and T. bayeri produced the following results.
Figure 4. Average day (9am) and night (9pm) crawling speed of P. ocellatus and T. bayeri.
Figure 5. Graph comparing crawling speed of P. ocellatus and T. bayeri in the day (9am) and night (9pm).
Results showed that both species were significantly more active during the day than the night. However, T. bayeri was active during the night as well, while P. ocellatus was not active at all. This difference in behaviour could be contributed to P. ocellatus being entirely diurnal. A preliminary study conducted by Pittman (2011) calculated the population size of P. ocellatus present in Hawaii. Despite having found P. ocellatus in the night as well, majority of the population were observed during the day. This suggest the likelihood that P. ocellatus is diurnal instead of nocturnal, relating to data collected in this study. This is further supported by P. ocellatus requirement of light to produce food photosynthetically.
The lack of activity of P. ocellatus in comparison to T. bayeri could also be contributed by predatory pressure. T. bayeri are brightly coloured while P. ocellatus are pale coloured. The presence of bright colours on T. bayeri could be a warning to predation of its its chemical defences (Cimino and Ghiselin, 1998). On the other hand, P. ocellatus is pale coloured, suggesting the lack/reduced chemical defences, thus requiring the need to decrease activity to enhance camouflage.
Future in-depth experiments regarding P. ocellatus response to light can be considered. Furthermore, these experiment could be enhanced by conducting them in relation to other sacoglossa species, such as T. bayeri or species from the Elysia genus.
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