Barnacles
| Barnacles | ||||||||||
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| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Balanidae | ||||||||||
| Leach , 1806 |
Barnacles (Balanidae) are barnacles , to the group of cancers include. These are sessile animals , so in the adult state they can no longer change their whereabouts. Outwardly visible are only whitish cones, their arms, legs and scissors are transformed into tendril feet.
habitat
Barnacles can be found worldwide mainly in the intertidal zone on coasts , but some species can also be found in greater depths of the sea. At the end of their larval stage, they attach themselves to the first pair of antennas by means of two suction cups on solid surfaces such as stones and rocks, but also on crabs, mussels (particularly often on mussels ), snail shells or humpback whales , with which the barnacles share their habitat . In Germany only a few are species native to, but by attaching to ships other types to Germany have fallen.
anatomy
The soft body is surrounded by 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. Inside the opening at the top there are two pairs of sealing lids, with which the barnacles can protect themselves from drying out. With the lids closed, they can hold out for days and also tolerate larger fluctuations in the water level. On the underside, there is a lime plate that adheres firmly to the sub-floor. This natural adhesive enables the barnacles to withstand the extreme conditions of surf and tides .
The six pairs of sternum bones with bristles on the sides function as traps with which they comb the water. The diameter of the animals is 0.5 to 3 cm.
nutrition
For feeding, the barnacles hold their legs, which have been broadened in a comb-like manner by the side bristles, next to each other in a fan-like manner, thus forming a close-meshed basket that they regularly pull through the water in different directions. Small microorganisms and suspended particles are quasi sifted out of the water as food. When the tide is low, the legs disappear under the lids, but in the water they stick out their muzzle.
Reproduction and development
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Barnacles are hermaphrodites that fertilize each other. The partner must be in the immediate vicinity due to the location of the adult animal. To reproduce, they scan the area around them with their penis, which is up to eight times longer than their body size and one of the longest in the animal kingdom, and look for other barnacles.
After the eggs are inseminated, they remain in the lime shell. When the larvae hatch in spring, they initially have the nauplius shape typical of crabs . Then they transform into a so-called cypris larva with a small shell made up of two side shells, similar to a mussel. At this stage, the settlement takes place in the permanent location, typically in the vicinity of other barnacles. To do this, the larva attaches itself, turns its back to the ground and cements itself in place. After cementing, it sheds its skin several times within the shell. The rate of growth is determined by the water temperature and the food supply.
Predators
Barnacles are eaten by crabs, sea urchins and snails (in the North Sea in particular by the northern purple snail ), and in cold winters also by sandpipers (from the snipe family ), oystercatchers and turnstone . In addition, barnacles are also used for human consumption. For example, the species Austromegabalanus psittacus, called Picoroco in South America, is often used in curanto, a stew.
Individual evidence
- ↑ Barnacle glue
- ↑ Barnacle glue
- ^ Gertraud Luther: Barnacles of the German coastal waters. Helgoland marine sub. 41, 1--43 (1987) ( Online, PDF )
- ↑ Christopher J. Neufeld & A. Richard Palmer. "Precisely Proportioned: Intertidal Barnacles Alter Penis Form to Suit Coastal Wave Action." Proceedings of the Royal Society B: Biological Sciences 275.1638 (2008): 1081-1087. doi: 10.1098 / rspb.2007.1760
