A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, colonial cnidarians, and sponges, to the substrate. ROOT is an object-oriented program and library developed by CERN. An aquatic animal is an Animal which lives in water for most or all of the time Sessile is a term in Biology with two distinct meanings In botany and medicine In Botany, sessile means "without a stalk Seaweed is a loose colloquial term encompassing macroscopic Multicellular, benthic marine Algae. Algae ( sing. alga are a large and diverse group of simple typically Autotrophic organisms ranging from Unicellular to Multicellular forms Crinoids, also known as sea lilies or feather-stars, are marine animals that make up the class Crinoidea of the Echinoderms (phylum Echinodermata Cnidaria (naɪˈdɛəriə is a phylum containing some 9000 Species of Animals found exclusively in aquatic mostly marine, environments [1]
Holdfasts vary in shape and form depending on both the species and the substrate type. The holdfasts of organisms that live in muddy substrates often have complex tangles of root-like growths, while those of organisms that live in sandy substrates are bulb-like and very flexible, such as the holdfast of sea pens, allowing the organism(s) to pull the entire body into the substrate when the holdfast is contracted. Sea pens are colonial marine Cnidarians belonging to the order Pennatulacea. The holdfasts of organisms that live on smooth surfaces (such as the surface of a boulder) have the base of the holdfast literally glued to the surface. The organism derives no nutrients from this intimate contact with the substrate, primarily because if the organism attempted to extract nutrients enzymatically from the substrate, the substrate would be eroded away, thereby increasing the risk of falling off of the substrate.
References
- ^ D. N. Thomas (2002). Seaweeds. Natural History Museum, London. The Natural History Museum is one of three large Museums on Exhibition Road, South Kensington, London (the others are the Science Museum ISBN 0-565-09175-1.
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