Appendages may become uniramous, as in insects and centipedes, where each appendage comprises a single series of segments, or it may be biramous, as in many crustaceans, where each appendage branches into two sections. Triramous (branching into three) appendages are also possible.[1]
All arthropod appendages are variations of the same basic structure (homologous), and which structure is produced is controlled by "homeobox" genes. Changes to these genes have allowed scientists to produce animals (chiefly Drosophila melanogaster) with modified appendages, such as legs instead of antennae.[2]
A number of surface appendages may be present on different archaea. Two types of appendage are species-specific; cannulae are specific to Pyrodictium species, and hami are specific to Altiarchaeum.[3] Other various types of surface structure include pili, archaella (archaeal flagella), structures called bindisomes that bind sugars, and posttranslationally modified archaellins and pilins.[4][5]
Archaella are the similar structures to bacterial flagella with the same function in motility particularly swimming, but with a different composition and action. Pili are used in attachment to surfaces, possible communication between cells enabling cell to cell contact allowing genetic transfer, and the formation of biofilms.[4]Atype IV pili model is used in the assembly of several cell surface structures. The bindisome is made up of sugar binding proteins to facilitate sugar uptake. So far studies are limited to S. solfataricus.[4] Appendage fibres described as Iho670 fibres are unique to Ignicoccus hospitalis.[4]
Bacterial surface appendages include flagella, pili, short attachment pili known as fimbriae, and on some species curli fibres.
Some bacteria also have stalks known as prosthecae.
Aleaf is the main appendage of a plant stem.
Prosthechea is a genus of orchids named for the prostheca appendage on the back of the column. Hair like structures known as trichomes are found on many types of plants.
^Emerald, B. Starling; Cohen, Stephen (March 2004). "Spatial and temporal regulation of the homeotic selector gene Antennapedia is required for the establishment of leg identity in Drosophila". Developmental Biology. 267 (2): 462–472. doi:10.1016/j.ydbio.2003.12.006. PMID15013806.