Abstract:

To date, specific studies on the seasonality of Mediterranean nudibranchs are still rather scarce. In the present study, we investigated the trend of seasonal variations in the number of nudibranch species from 2018 to 2021 in three sites located along the central-eastern coast of Sicily (Italy). Data on the seasonality were collected by photographing all nudibranch species encountered during the scuba dives performed in the study sites. Then, for each site, it was selected randomly one dive for every month, from which the number of found nudibranch species was counted. In all the examined sites, it was noted that the number of nudibranch species varies with a marked seasonal trend throughout the year: the number of species increases from mid-late autumn until spring (the season with the highest number of species). By contrast, between late spring and early summer this number begins to decline, decreasing considerably during summer and early autumn, the seasons in which there is the lowest value. This trend may be correlated with both the seasonality of sessile benthic suspension feeders, the main nudibranch preys, and the seasonal variations in the water column throughout the year.

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