Acorn Barnacles (Balanus or Chthamalus)

(hard to differentiate between them in the field)

Contributed by Dr. Bonnie Becker

Where institute:Along upper limit of intertidal zone.

Interesting facts:Although they await more than like they are molluscs (related to animals with shells, similar mussels and clams), they are actually crustaceans. That means they are more closely related to lobsters and crabs.

Adaptations:These dirty-looking shells announced to be dead remnants of old animals. They are sessile (not-moving) animals that oversupply together on higher rocks, out of the water most of the day, during which they are exposed to a lot of sun, rain, and wind. Although they appear to be dead, they are holding their operculum, a set of hinged plates, tightly closed. During the farthermost loftier tides, they are immersed in water and all of a sudden spring to life. The operculum is opened and the animals pulse their appendages, bringing in microscopic food.

Studies done with Chthamalus fissus (yous pronounce this as if the Ch isn't there) showed they are quite hardy. They can tolerate long periods of desiccation. Some animals survived four months continuously immersed in fresh water. Some even lived for two months in Vaseline.

Nutrient:Acorn barnacles are filter feeders, using their appendages to force water (and its microscopic plants and animals) to their feeding parts.

Life history:Eggs and embryos are retained, or brooded, within the shell of the parent to be released as nauplii. Nauplii are complimentary-swimming, planktotrophic larvae with i center, ane crush, and iii pairs of legs. After a number of changes, it becomes a cypris, with iii eyes, ii shells, and six pairs of legs. At this point it is set to settle. The cypris attaches itself to its substrate, cements itself, and secretes its vanquish. As an adult, the barnacle is bullheaded with its head attached to the substrate and its feathery legs extended equally feeding appendages. Since information technology is sessile equally an developed, the settling of the cypris is a crucial event in the life bike of a barnacle. Newly settled barnacles will inhabit a wide range of shoreline, although their predators quickly pare down the populations to a narrow band of survivors. As an adult, barnacles molt, releasing their thin pare-similar covering, not their outer shell. They attain maturity at the end of their get-go twelvemonth, can alive for 8 to ten years, and produce one to 3 broods of up to thirty,000 larvae during each winter and jump.

Other species of barnacles:The pinkish thatched barnacles (Tetraclita rubescens) are much larger than the acorn barnacles, and tend to be more than solitary. They are found in similar locations equally acorn barnacles. Larvae are released during the summer and animals that are not victims of predation tin live upwards to 15 years.

Nomenclature:
 Phylum: Arthropoda (Business firm, jointed exoskeleton and jointed appendages)
Class:              Crustacea (Barnacles, Beach hoppers, Shrimps, Lobsters, Crabs, etc.)
SubClass:        Cirripedia (Barnacles)
Order:             Thoracica

Acorn Barnacles

Last revised 29-Jul-13