Commensal and Parasitic Barnacles Term Paper Example | Topics and Well Written Essays - 1500 words

Commensal and Parasitic Barnacles - Term Paper Example Barnacles are both commensals and parasites. As commensals, barnacles usually benefit from their hosts by having a place to stay, and being carried to nutrient-rich areas of the sea (â€Å"Hitchhiker†). Although the host animal, such as whales, does not benefit from barnacles attached to its body, the host remains unaffected. On the other hand, parasitic barnacles bore through the exoskeleton of the host and moves to the blood and the midgut of the animal until it branches into a mass of harmful tissue, thus killing the animal host (â€Å"Sacculina†). Overall, there are several types of barnacles but only four orders. Order Thoracica or the â€Å"True Barnacles† The first order of barnacles is the order Thoracica, or the â€Å"true barnacles† Newman & Abbott). The Thoracica are the most important because they are more abundant and more conspicuous than the species of the other orders. Although the Thoracica occur most abundantly in the tropical Indo-Pacifi c region of the ocean, they are basically found in all types of marine environments, both in saltwater and freshwater. However, it remains a fact that â€Å"none completes its life cycle in freshwater† (Newman & Abbott). ... ally dependent† on larger animals like shark, corals or worms, especially during the earlier stages of barnacle evolution, and although their symbiosis was only for â€Å"support or protection,† these relationships were still considered parasitic (Newman & Abbott). There are three suborders of Thoracica barnacles: the stalked barnacles or Lepadomorpha, the assymetrical sessile barnacles or the Verrucomorpha, and the symmetrical sessile barnacles or the Balanomorpha. The Lepadomorpha or stalked barnacles usually have a body â€Å"divided into a capitulum with cirri and mouthparts as feeding appendages, and a peduncle or stalk which attaches the animal to the substratum. Occasionally, the capitulum and the peduncle are heavily laden with calcareous plates (Newman & Abbott). Source: http://cccmkc.edu.hk/~kei-kph/Ecology/Stalked%20barnacle_Pollicepes.htm Certain Lepadomorpha barnacles, which act as commensals, are usually found in the teeth of the pygmy killer whale or Fere sa attenuata, the sperm whale or Physeter macrocephalus, the goosebeak whale or Ziphius cavirostris, and the Antillean beaked whale or Mesoplodon europaeus, as well as other cetaceans that thrive the deep marine waters (Mignucci-Giannoni, â€Å"Metazoan Parasites†). One unique Lepadomorpha barnacle is the goose barnacle or Lepas anserifa, which is similar to the Balanomorpha or acorn barnacles because of its protective shell (â€Å"Barnacles†). The buoy barnacle, or Dosima fascicularis, is also closely related to the goose barnacle. Although almost all true barnacles are commensals, based on early research, there is a Lepadomorpha barnacle which is parasitic and that is the Conchoderma virgatum (Williams; Hastings). According to information from Williams, the Conchoderma can parasitize two species of whale