Tideline barnacles

Virtually all rocky seashores in Malta sport millions of these unassuming, pyramidal entities that close or open to feed or reproduce depending on the availability of seawater from tide or waves. They are barnacles mostly belonging to the species Chthamalus stellatus Poli, 1791, though other species of Chthamalus are also present on Maltese shores.

As seen in the photograph above (lower right hand corner and upper centre), dead individuals leave behind calcareous volcano-shaped cavities which may be used as a refuge by other intertidal organisms, such as the amphibious and very interesting snail Melarhaphe neritoides (L., 1758) or even other crustaceans such as amphipods. The photograph was taken at Dwejra, Gozo, during receding tide. On the other hand, the photograph below shows completely dry specimens from Buġibba, waiting for the presence of water to resume any activity.

Melarhaphe neritoides - before and after

Melarhaphe neritoides (Linn., 1758) is a seasnail which spends the summer months aestivating in cracks on bare rock, in a part of the shore where the sea does not reach, sealing up its aperture with a solid horny operculum to prevent losing water in the extreme heat accumulating during the day.

As soon as winter comes, more powerful waves and heavier mist start wetting the area where the snail lives, eventually filling pools in the rock and allowing the snail to resume its 'normal' lifestyle - moving about, grazing on algae, mating and laying eggs, in time before the dryness returns.

The following photographs were taken in the same rock hollow in August (photo 1) and December (photo 2) on the limestone shore of Buġibba, Malta, showing the snail during its period of inactivity and its subsequent 'resurrection'.