Barnacle

Description:

"A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (non-motive) suspension feeders, and have two nektonic (active swimming) larval stages. Around 1,220 barnacle species are currently known.[1] The name "Cirripedia" is Latin, meaning "curl-footed"."

Habitat:

"A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile (non-motive) suspension feeders, and have two nektonic (active swimming) larval stages. Around 1,220 barnacle species are currently known.[1] The name "Cirripedia" is Latin, meaning "curl-footed"."

Notes:

"Life cycle Barnacles have 2 distinct larval stages, the nauplius and the cyprid, before developing into a mature adult. [edit]Nauplius A fertilised egg hatches into a nauplius: a one-eyed larva comprising a head and a telson, without a thorax or abdomen. This undergoes 6 months of growth before transforming into the cyprid stage. Nauplii are typically initially brooded by the parent, and released as free-swimming larvae after the first moult. The barnacle cyprid larva [edit]Cyprid stage Main article: Cyprid The cyprid stage lasts from days to weeks. During this part of the life cycle, the barnacle searches for a place to settle. It explores potential surfaces with modified antennules; once it has found a potentially suitable spot, it attaches head-first using its antennules, and a secreted glycoproteinous substance. Larvae are thought to assess surfaces based upon their surface texture, chemistry, relative wettability, colour and the presence/absence and composition of a surface biofilm; swarming species are also more likely to attach near to other barnacles. As the larva exhausts its finite energy reserves, it becomes less selective in the sites it selects. If the spot is to its liking it cements down permanently with another proteinacous compound. This accomplished, it undergoes metamorphosis into a juvenile barnacle. [edit]Adult stage Typical acorn barnacles develop six hard calcareous plates to surround and protect their bodies. For the rest of their lives they are cemented to the ground, using their feathery legs (cirri) to capture plankton. Once metamorphosis is over and they have reached their adult form, barnacles will continue to grow by adding new material to their heavily calcified plates. These plates are not moulted; however, like all ecdysozoans, the barnacle itself will still molt its cuticle.[12] [edit]Sexual reproduction Most barnacles are hermaphroditic, although a few species are gonochoric or androdioecious. The ovaries are located in the base or stalk, and may extend into the mantle, while the testes are towards the back of the head, often extending into the thorax. Typically, recently molted hermaphroditic individuals are receptive as females. Self-fertilization, although theoretically possible, has been experimentally shown to be rare in barnacles.[13][14] The sessile lifestyle of barnacles makes sexual reproduction difficult, as the organisms cannot leave their shells to mate. To facilitate genetic transfer between isolated individuals, barnacles have extraordinarily long penises. Barnacles have the largest penis to body size ratio of the animal kingdom.[13]"