Balanidae

Barnacles and mussels in Galicia

Barnacles ( Balanidae ) are barnacles, belonging to the group of cancers. These are sessile animals, in the adult state, they can no longer change their whereabouts. Externally visible are only whitish cones, their arms, legs and claws are modified into tendrils feet.

Habitat

Barnacles can be found mainly in the intertidal zone on the coasts, some species but also in larger ocean depths worldwide. You sit down at the end of their larval stage using two suction cups on the first pair of antennae on solid substrates such as stones and rocks, but also on crabs, mussels ( particularly common mussels ) found snail shells or humpback whales, with which the barnacles share the habitat. In Germany, only a few species are native, by attachment to ships, other types are, however, reached Germany.

Physique

The soft body surrounded four to eight small lime platelets in the form of a conical wall. These platelets are whitish to light gray and often frayed at the edges. Within the overhead opening there are two pair of shutter Deckelchen, with the help of which barnacles can help protect against dehydration. With sealed lids they can endure for days and endure greater fluctuations in water level good. On the bottom of a limestone slab connects strongly adhered to the substrate. This natural adhesive allows the barnacles to withstand the extreme conditions of waves and tides; in its effect, it surpasses the strongest epoxy adhesive.

The multi-unit, side occupied with six bristles sternum pairs act as traps with which they scour the water. The diameter of the animals is from 0.5 to 3 cm.

Nutrition

To feed the barnacles keep their comb-like widened by the lateral bristles legs like a fan next to each other and thus form a close-knit basket she regularly pull in different directions through the water. Small micro-organisms and suspended particles are quasi screened as food from the water. At low tide, however, disappear legs under the covers, in the water they stretch out their fishing feet.

Reproduction and Development

Barnacles are hermaphrodites, which are mutually beneficial. The partners must be located in the immediate vicinity due to the stationarity of the adult animal. For reproduction, they fumble with the penis, which belongs relative to the body size of the longest in the animal kingdom, the space around and seek for other barnacles.

After fertilization, the eggs they remain in Kalkpanzer. When the larvae hatch in the spring, they first have the typical for the crabs Naupliusgestalt. Then they turn into a so-called Cyprislarve with a small tank of two side dishes, like a shell. At this stage, the establishment of the permanent headquarters takes place, typically in the vicinity of other barnacles. In return, the larva attached to, turns his back to the ground and cemented on. After cementing it molts several times within the carapace. The growth rate is determined by the water temperature and food supply.

Predators

Barnacles are of crabs, sea urchins and snails ( in the North Sea in particular the Nordic purple snail ) eaten in cold winters by the sea beach runners ( from the family of the Waders ), oystercatchers and rock tomes.