''Dictyota'' is a genus of brown

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals ( diterpenes) which have potential medicinal value. As at the end of 2017, some 237 different diterpenes had been identified from across the genus.

Taxonomy and Nomenclature

The genus ''Dictyota'' was first described by Jean Vincent Lamouroux in 1809. The name ''Dictyota'' is derived from the Greek word “Διχτυον” meaning “net” or “network”, referring to the inner cellular structure of specimens when viewed under a microscope, which features netted cortical and medullary cells. ''Dictyota'' belongs to the order Dictyotales and the SSDO-clade, which also includes the orders

Sphacelariales Sphacelariales is an order of brown algae Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae ...

, Syringodermatales, and Onslowiales. The family Dictyotaceae is divided into two tribes: Dictyoteae and Zonarieae. The former have a single lens-shaped apical cell from which the thallus grows, while the latter are characterized by a row or cluster of apical cells. The genera ''Glossophora'', ''Glossophorella'', and ''Pachdictyon'' are synonyms of ''Dictyota'' as DNA sequencing revealed that they were closely related.

Morphology

External characteristics

''Dictyota'' has "flat, ribbon-like axes" which exhibit dichotomous branching that may be either isotomous (equal or symmetrical) or anisotomous (unequal). Isotomous branches may be recurved, while anisotomous branches may become falcate (hooked), or cervicorn, if combined with twisting axes. Apical meristems of ''Dictyota'' species have been reported to be either truncate, rounded, or acute. A considerable degree of morphological plasticity has been observed from branching patterns, thus making molecular analyses indispensable when identifying species. Colors of living thalli range from dark brown to green (as in ''D. friabilis'') or blue (as in ''D. cyanoloma''). The thalli grow from apical cells which differentiate into an outer cortical and an inner medullary cell layer. Cortical cells on the margins of the thalli may grow into leaf-like projections or teeth (as in ''D. ciliolata'' and ''D. cyanoloma'') while adventitious branches may grow from the central cortical cells. Thalli may also grow hair (20-50 um in diameter). Thalli attach to the substrate via rhizoids which are multicellular, uniseriate, branching, and hyaline (glassy or transparent). Different species may have one or several attachment points which can lead to a wide range of growth forms (i.e. creeping thalli or fully erect). Dictyota-dichotoma-19880601-a

Internal anatomy

The thalli are

parenchyma Parenchyma () is the bulk of functional substance in an animal organ or structure such as a tumour. In zoology it is the name for the tissue that fills the interior of flatworms. Etymology The term ''parenchyma'' is New Latin from the word π ...

tous and are characterized by one or more

apical cells Apical means "pertaining to an apex". It may refer to: * Apical ancestor, refers to the last common ancestor of an entire group, such as a species (biology) or a clan (anthropology) *Apical (anatomy), an anatomical term of location for features l ...

that divide into an outer cortical and an inner medullary cell layer which can have several different configurations (e.g. uni-layered cortex with unilayered medulla, uni-layered cortex with multi-layered medulla, etc.).

Distribution

''Dictyota'' is distributed along tropical to temperate waters with species having generally restricted geographic ranges. It is the most abundant genus of brown algae in the Mediterranean Sea as well as the Atlantic coasts of Europe.

Ecology

Species of the genus are commonly found in subtidal to intertidal rocky pools. Seasonality in species' abundances as well as fertility are driven mainly by temperature, photoperiod, and solar radiation. For instance, populations of ''D. dichotoma'' in the southern hemisphere are highly abundant for a majority of the year but are largely absent in the warmer months, which is when its northern counterparts are most abundant and fertile.

Life History

''Dictyota'' exhibits an isomorphic life cycle wherein the alternating gametophyte and sporophyte phases appear morphologically similar. This alternation co-occurs with a change in ploidy. The gametophytes produce gametes which undergo fertilization to produce the diploid sporophyte, which then produces sporangia which will release 4 haploid spores through meiosis. Half of the haploid spores will develop into the female gametophytes while the other half will develop into male gametophytes, starting the process over again. ''Dictyota'' is

dioecious Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproductio ...

and reproduces both sexually and asexually. Release of gametes follows a diurnal and lunar periodicity. Gametes are often released 20–30 minutes after first light, with peaks occurring once or twice a month depending on the species. Asexual reproduction may occur via adventitious branching following the loss of the apical meristem.

Chemical Composition

''Dictyota'' is known to have high levels of fatty acids and lipids which makes the genus ideal for use as feedstock. The pigments found in ''Dictyota'' are Chlorophyll ''a'', ''c,'' fucoxanthin and violaxanthin which are present in a ratio of 13:3:10:1. This ratio may be altered by depth.

Exploitation/Utilization and Management

The genus is not currently cultivated nor harvested on an industrial scale. It is mainly exploited for its secondary metabolites which are known to have anticoagulant, antibacterial, anti-inflammatory properties, among others, making them useful for a wide range of pharmaceutical applications. For instance, there is evidence that methanolic extracts of ''Dictyota'' inhibits the butyrylcholinesterase (BuChE) enzyme in humans, which could potentially treat Alzheimer's disease. Other applications include its use as biofuel - due to the high lipid content of some species - and as supplemental feeds for poultry, cattle, and fish. A study in 2014 found that feeds with ''D. bartayresiana'' supplements could potentially reduce in vitro methane production of ruminants by 92.2%, which may have implications for reducing emissions from the agricultural sector.

Species

The genus ''Dictyota'' contains the following species:Guiry, M.D. & Guiry, G.M. (2018). AlgaeBase. World-wide electronic publication, National University of Ireland, Galway (taxonomic information republished from AlgaeBase with permission of M.D. Guiry). Dictyota J.V.Lamouroux, 1809. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=144086 on 2018-07-12M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org/search/genus/detail/?genus_id=oe101e7b01e405395 ; searched on 12 July 2018. *'' Dictyota acutiloba'' J.Agardh, 1848 *'' Dictyota adhaerens'' Noda, 1965 *'' Dictyota adnata'' Zanardini, 1878 **'' Dictyota adnata f. nana'' Post *'' Dictyota aegerrima'' ( Allender &

Kraft The second incarnation of Kraft Foods is an American food manufacturing and processing conglomerate, split from Kraft Foods Inc. in 2012 and headquartered in Chicago, Illinois. It became part of Kraft Heinz in 2015. A merger with Heinz, arra ...

) De Clerck, 2006 *'' Dictyota alternifida'' J.Agardh, 1894 *'' Dictyota anastomosans'' Steen et al. *'' Dictyota apiculata var. Agardh'' Weber-van Bosse *'' Dictyota asiatica'' I.K.Hwang *''

Dictyota attenuata ''Dictyota'' is a genus of brown seaweed in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals ( diterpenes) which have potential medicinal value. As at the end ...

'' P.Crouan & H.Crouan, 1842 *''

Dictyota bartayresiana ''Dictyota bartayresiana'', commonly known as a forded sea tumbleweed, is a species of brown alga found in the tropical western Indo-Pacific region and the Gulf of Mexico. It contains chemicals that are being researched for possible use as antimi ...

'' J.V.Lamouroux, 1809 **'' Dictyota bartayresiana var. divaricata'' Kützing *''

Dictyota bifurca ''Dictyota'' is a genus of brown seaweed in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals ( diterpenes) which have potential medicinal value. As at the end ...

'' J.Agardh, 1894 *'' Dictyota binghamiae'' J.Agardh, 1894 *'' Dictyota canaliculata'' O.De Clerck & E.Coppejans, 1997 *'' Dictyota canariensis'' ( Grunow) Tronholm, 2013 *''

Dictyota caribaea ''Dictyota'' is a genus of brown seaweed in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals (diterpenes) which have potential medicinal value. As at the end o ...

'' Hörnig & Schnetter, 1992 **'' Dictyota cervicornis f. pseudodichotoma'' Taylor **''

Dictyota cervicornis f. spiralis ''Dictyota'' is a genus of brown seaweed in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals (diterpenes) which have potential medicinal value. As at the end o ...

'' Taylor **''

Dictyota ceylanica var. anastomosans ''Dictyota'' is a genus of brown seaweed in the family Dictyotaceae. Species are predominantly found in tropical and subtropical seas, and are known to contain numerous chemicals ( diterpenes) which have potential medicinal value. As at the end ...

'' Yukio Yamada, Yamada *''Dictyota chalchicueyecanensis'' Lozano-Orozco & Sentíes **''Dictyota ciliata var. humilis'' Grunow *''Dictyota ciliolata'' Otto Wilhelm Sonder, Sonder ex Kützing, 1859 *''Dictyota concrescens'' W.R.Taylor, 1945 *''Dictyota coriacea'' (Edward Morell Holmes, Holmes) I.K.Wang, H.-S.Kim & W.J.Lee, 2004 *''Dictyota crenulata'' J.Agardh, 1847 *''Dictyota cribrosa'' William Albert Setchell, Setchell & N.L.Gardner, 1930 *''Dictyota crinita'' ( J.Agardh) Hörnig, Schnetter & Prud'Homme van Reine, 1992 *''Dictyota crux'' **''Dictyota crux f. parva'' A.Bachmann *''Dictyota cuneata'' George Dickie (botanist), Dickie, 1874 *''Dictyota cyanoloma'' Tronholm, De Clerck, A.Gómez-Garreta & Rull Lluch, 2010 *''Dictyota cymatophila'' Tronholm, M.Sanson & Afonso-Carrillo, 2010 *''Dictyota decumbens'' (R.W.Ricker) Hörnig, Schnetter & Prud'homme van Reine, 1992 *''Dictyota detergenda''

, 2009 *''Dictyota dhofarensis'' (Mohammed Nizamuddin (botanist), Nizamuddin & A.C.Campbell) De Clerck, 2006 *''Dictyota dichotoma'' (William Hudson (botanist), Hudson) J.V.Lamouroux, 1809 *''Dictyota dichotoma'' Johannes Nicolaus von Suhr, Suhr, 1839 **''Dictyota dichotoma f. angustior'' Victor Félix Schiffner, Schiffner **''Dictyota dichotoma var. fimbriata'' Antonio Piccone, Piccone & Grunow **''Dictyota dichotoma var. genuina'' Grunow **''Dictyota dichotoma var. guinea'' Grunow **''Dictyota dichotoma var. inequalis'' Samuel Frederick Gray, S.F.Gray **''Dictyota dichotoma var. intricata'' (Carl Adolph Agardh, C.Agardh) Robert Kaye Greville, Greville **''Dictyota dichotoma var. patens'' **''Dictyota dichotoma f. proliferans'' Ercegovic *''Dictyota diemensis'' Otto Wilhelm Sonder, Sonder ex Kützing, 1859 *''Dictyota dilatata'' Yukio Yamada, Yamada, 1925 *''Dictyota divaricata'' P.L.Crouan & H.M.Crouan, 1865 *''Dictyota dolabellana'' De Paula, Yoneshigue-Valentin & Alcides Ribeiro Teixeira, Teixeira, 2008 *''Dictyota dumosa'' Frederik Børgesen, Børgesen, 1935 *''Dictyota fasciculata'' Sperk, 1869 *''Dictyota fascida'' J.Agardh, 1898 **''Dictyota fasciola var. abyssinica'' J.Agardh *''Dictyota fasciola'' (Albrecht Wilhelm Roth, Roth) J.V.Lamouroux, 1809 **''Dictyota fasciola var. divergens f. major'' Victor Félix Schiffner, Schiffner **''Dictyota fasciola var. divergens f. minor'' Victor Félix Schiffner, Schiffner **''Dictyota fasciola var. elongata'' Giuseppe De Notaris, De Notaris **''Dictyota fasciola f. major'' Victor Félix Schiffner, Schiffner **''Dictyota fasciola f. minor'' Victor Félix Schiffner, Schiffner **''Dictyota fasciola var. repens'' ( J.Agardh) Francesco Ardissone, Ardissone *''Dictyota fastigiata'' Otto Wilhelm Sonder, Sonder, 1845 *''Dictyota fenestrata'' J.Agardh, 1894 *''Dictyota flabellata'' (F.S.Collins) William Albert Setchell, Setchell & N.L.Gardner, 1924 *''Dictyota flabellulata'' Michael Foster (physiologist), Foster & Schiel *''Dictyota flagellifera''

, 2009 *''Dictyota foliosa'' J.Agardh, 1892 *''Dictyota friabilis'' William Albert Setchell, Setchell, 1926 *''Dictyota furcellata'' (Carl Adolph Agardh, C.Agardh) Robert Kaye Greville, Greville, 1830 *''Dictyota galapagensis'' (William Gilson Farlow, Farlow) De Clerck, 2006 *''Dictyota grossedentata'' De Clerck & Coppejans, 1999 *''Dictyota guajirae'' Hörnig, Schnetter & J.M.Over, 1992 *''Dictyota guineënsis'' ( Kützing) P.L.Crouan & H.M.Crouan, 1878 *''Dictyota gunniana'' ( J.Agardh) I.Hörnig, R.Schnetter & Prud'homme van Reine, 1992 *''Dictyota hamifera'' William Albert Setchell, Setchell, 1926 *''Dictyota harveyana'' *''Dictyota hauckiana'' Mohammed Nizamuddin (botanist), Nizamuddin, 1975 *''Dictyota humifusa'' Hörnig, Schnetter & Coppejans, 1992 *''Dictyota implexa'' (René Louiche Desfontaines, Desfontaines) J.V.Lamouroux, 1809 *''Dictyota indica'' G.P.S. Anand, Anand, 1965 *''Dictyota inscripta'' J.Agardh, 1893 *''Dictyota intermedia'' Zanardini, 1874 *''Dictyota jamaicensis'' W.R.Taylor, 1960 *''Dictyota kunthii'' (Carl Adolph Agardh, C.Agardh) Robert Kaye Greville, Greville, 1830 *''Dictyota laciniata'' J.V.Lamouroux, 1809 *''Dictyota lata'' J.V.Lamouroux, 1809 **''Dictyota linearis var. campsosticha'' Camille Montagne, Montagne **''Dictyota linearis f. intricata'' Kützing **''Dictyota linearis var. major'' P.Crouan & H.Crouan **''Dictyota linearis var. minor'' Otto Wilhelm Sonder, Sonder *''Dictyota littoralis'' P.Anand, 1965 *''Dictyota liturata'' J.Agardh, 1848 *''Dictyota major'' W.R.Taylor, 1945 *''Dictyota masonii'' William Albert Setchell, Setchell & N.L.Gardner, 1930 *''Dictyota mayae'' Lozano-Orozco & Sentíes *''Dictyota mediterranea'' (Victor Félix Schiffner, Schiffner) G.Furnari, 1997 *''Dictyota menstrualis'' (William Dana Hoyt, Hoyt) Schnetter, Ingrid Hörnig, Hörnig & Weber-Peukert, 1987 *''Dictyota mertensii'' (C.Martius) Kützing, 1859 *''Dictyota moniliformis'' ( J.Agardh) Hörnig, Schnetter & Prud'homme van Reine, 1992 *''Dictyota multifida'' (J.E.Smith) Jean Baptiste Bory de Saint-Vincent, Bory, 1838 *''Dictyota naevosa'' (Johannes Nicolaus von Suhr, Suhr) Camille Montagne, Montagne, 1840 *''Dictyota nigrescens'' Zanardini, 1878 *''Dictyota nigricans'' J.Agardh, 1882 *''Dictyota ocellata'' J.Agardh, 1894 *''Dictyota pachyderma'' Luan Rixiao & Ding Lanping *''Dictyota paniculata'' J.Agardh, 1841 *''Dictyota papenfussii'' Victor W. Lindauer, Lindauer, 1949 **''Dictyota pavonia var. maxima'' J.V.Lamouroux *''Dictyota pedrochei'' Lozano-Orozco & Sentíes *''Dictyota pellucida'' J.Agardh, 1892 *''Dictyota penicellata'' J.V.Lamouroux *''Dictyota phlyctaenodes'' Camille Montagne, Montagne, 1852 *''Dictyota pinnata'' (E. Yale Dawson, E.Y.Dawson) I.Hörnig, R.Schnetter & Prud'homme van Reine, 1993 *''Dictyota pinnatifida'' Kützing, 1859 **''Dictyota pinnatifida var. rigida'' Grunow *''Dictyota plantaginea'' J.V.Lamouroux ex Frauenfeld, 1855 *''Dictyota plectens'' ( Allender &

)

, 2009 *''Dictyota pleiacantha'' Tronholm, 2013 *''Dictyota polyclada'' Otto Wilhelm Sonder, Sonder ex Kützing *''Dictyota pontica'' Sperk, 1869 *''Dictyota pulchella'' Hörnig & Schnetter, 1988> *''Dictyota rhizodes'' (Dawson Turner, Turner) J.V.Lamouroux *''Dictyota rigida'' De Clerck & Coppejans, 1999 *''Dictyota robusta'' J.Agardh, 1894 *''Dictyota rotunda'' Carl Adolph Agardh, C.Agardh, 1820 *''Dictyota sandvicensis'' Otto Wilhelm Sonder, Sonder, 1859 *''Dictyota serrulata'' J.V.Lamouroux, 1809 *''Dictyota spathulata'' Yukio Yamada, Yamada, 1928 *''Dictyota spinulosa'' Joseph Dalton Hooker, J.D.Hooker & George Arnott Walker-Arnott, Arnott, 1838 *''Dictyota spiralis'' Camille Montagne, Montagne, 1846 *''Dictyota stolonifera'' E. Yale Dawson, E.Y.Dawson, 1962 *''Dictyota suhrii'' ( Kützing) I.Hörnig, R.Schnetter & W.F.Prud'homme van Reine, 1992 *''Dictyota vieillardii'' Kützing, 1863 **''Dictyota vieillardii var. filiformis'' Kützing *''Dictyota virellus'' Noda, 1971 *''Dictyota vittata''

, 2009 *''Dictyota vivesii'' M.A.Howe, 1911

References

{{Authority control Dictyotaceae Brown algae genera Seaweeds