''Padina'' is a genus of brown macroalgae in the family Dictyotaceae.

Taxonomy and nomenclature

There are currently 58 taxonomically accepted ''Padina'' species, considered to be a species rich genera showing high species diversity within the genus as shown by recent phylogenetic research and taxonomic studies. Species identification is considered to be a challenge in the genera, using a variety of morphological and life history traits are needed to be considered however, recent studies have used molecular markers to confirm species identification in a given locality.

Morphology

''Padina'' exhibits a flabellate-type appearance of its thalli, with a brown, off-white coloration. Its thallus consists of cells that is 2-8 layers thick, fan-shaped with hairs covering its margin. It has a stipe attached to its rhizoidal holdfast with blades conspicuously appearing as several layers of cell thick, with apparent zonations in its thalli producing coextensive rows of hair, distributed in rigid segments. ''Padina'' and ''Newhousia'' are the only genera in the brown algae group that is calcareous. ''Padina'' species are differentiated based on the cell layer number, sporangial sori arrangement relative to hair bands and hair band presence or lack of on the lower thallus surface.

Distribution

''Padina'' inhabits tropical regions, although the genus can also be found in cooler temperate waters from South America to Southeast Asia. The genus is distinguishable because of its characteristic shape resembling a peacock tail structure. It can be found a wide range of habitats, ranging from intertidal to subtidal zones. ''Padina'' are found to be more prolific in clear waters at a depth of 15–20 m but can be seen up to 110 m in depth, attached to hard substrates or growing as epiphytes on larger seaweeds (e.g. ''Sargassum''). ''Padina'' in the Indian Ocean have a much more narrow distribution, in specific localities compared to those in the Pacific with a distribution that is much more overlapping within regions

Ecology

''Padina'' can be found growing together with ''Gracilaria, Polysiphonia, Chaetomorpha,'' and ''Colpomenia''. ''Padina boergesenii'' and ''Padina jamaicensis'' may exhibit morphological plasticity which may affect herbivore interactions and grazing pressure.

Life history

''Padina'' is described to have a life history following diplohaplontic phases and are isomorphic. Its gametophytes are either dioecious or monoecious, located haphazardly in its blades sometimes even on its sori. ''Padina'' has hairs on its reproductive organs, on one thallus surface organized in a concentric margin. In some species, these get lost as they mature. Sporangial sori of ''Padina'' can be seen on one or both thallus surface, with or without indusium.

Cultivation and exploitation

No report on ''Padina'' cultivation is found.

Chemical composition

Approximately 32% of taxonomically accepted ''Padina'' species are being investigated for numerous chemical and potential pharmacological applications. Bioactive compounds, including amino acids, terpene sterols, and sulphated polysaccharides were reported to be found in ''Padina'', as well. Fucoidans can be obtained from two ''Padina'' species, ''P. tetrasomatica'' and ''P. boergesenii'', which can be used in a 2% ointment for wound treatment. Bromo-phenols and other halogenated compounds have also been found in ''Padina,'' found to affect the endocrine system by damaging calcium ions in cells. Fucosterol, diterpenes, and fucoxanthin are also found in ''Padina'' which can slow down the spread of malignant cells.

Utilization and management

''Padina'' has been shown to be capable of adsorption, effectively accumulating numerous pollutants in its biomass. As bioindicators, ''Padina'' respond to alterations in temperature, light, nutrients, and other contaminants in marine ecosystems. In one study, the specific growth rate and chlorophyll content of ''Padina'' is negatively affected as cadmium concentration increases, suggesting Cd pollution. Hence, ''Padina'' are ecologically significant macroalgae which function as excellent bioindicators of aquatic pollution and potentially, remediation in marine ecosystems. As sources of different bioactive compounds, ''Padina'' may have potential applications on many pharmacological aspects

References

{{Taxonbar, from=Q2260145 Brown algae genera Dictyotaceae Taxa named by Michel Adanson