Balanus perforatus (1) Barnacle Crostacea Cirripedia Balanidae Plexiglas Box

Barnacle Balanus perforatus Crostacea Cirripedia Balanidae, irregular cluster colony mm 33 x 30 x 19, in plexiglas box (cm 4.2 x 3.7 x 3.2 h), only a piece, as in photo.
Family: Balanidae (barnacles).
Common name: Perforated Barnacle.
Syn. Perforatus perforatus.

Balanus perforatus is a colonial sessile barnacle crustacean that grows up to 30 millimeters, both in diameter and in height.
Its shape resembles a volcano with steep sloping sides. The six fused lateral limestone plates are light brown-purplish in color, vertically rippled. Two pairs of movable plates cover the operculum which can be sealed by a purplish-brown flap when the barnacle is exposed out of the water or does not feed.
B. perforatus is found on the coasts along the eastern side of the Atlantic Ocean, including the Mediterranean Sea and the English Channel. Its most northerly extension is found in the southern areas of England and Wales, and at this limit of its range it can be strongly affected by severe winters. It has expanded its iffusion with the temperature rises that have occurred over the past few decades. It lives on artificial rocks and structures and is also part of the community of incrustations on the hulls of ships.
It feeds on plankton and, in addition to capturing suspended food particles, pumps water through the cavity of its mantle. The faster the beat, the more water is pumped and the volume can reach one liter per hour.
The larvae are initially hatched by the adult and after their first moult they are released into the water column, becoming part of the zooplankton. Late stage cyprid larvae establish themselves and attach themselves to a suitable substrate.