''Zanardinia'' is a monotypic

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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

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 are the major seaweeds of the temperate and po ...

(class Phaeophyceae). The only

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

, ''Zanardinia typus'', commonly known as penny weed, is native to the northeastern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

and the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

. The genus was

circumscribed In geometry, the circumscribed circle or circumcircle of a polygon is a circle that passes through all the vertices of the polygon. The center of this circle is called the circumcenter and its radius is called the circumradius. Not every polyg ...

Giovanni Domenico Nardo Giovanni Domenico Nardo (4 March 1802 – 7 April 1877) was an Italian naturalist from Venice, although he spent most of his life in Chioggia, home port of the biggest fishing flotilla of the Adriatic. He learned taxidermy and specimen preparatio ...

ex Giovanni Antonia Maria Zanardini in Mem. Real. Accad. Sci. Torino ser.2, vol.4 on page 236 in 1841. The genus name of ''Zanardinia'' is in honour of Giovanni Antonio Maria Zanardini (1804–1878), who was an Italian physician and

botanist Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the Ancient Greek wo ...

who specialized in the field of

phycology Phycology () is the scientific study of algae. Also known as algology, phycology is a branch of life science. Algae are important as primary producers in aquatic ecosystems. Most algae are eukaryotic, photosynthetic organisms that live in a w ...

Description

This brown alga is loosely secured to the rock by the felted

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be unic ...

s on the underside. Young individuals are circular and have a smooth surface and a double fringe of short hairs round the margin. Older individuals may be up to across and be fan-shaped or have broad blades with irregular margins. The consistency of the

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

is cartilaginous or leathery, and the colour is yellowish-brown or olive brown. Portions that become detached and wash up on the shore may crinkle as they dry and resemble pieces of blackish leather. This species could be confused with '' Cutleria adspersa'', but that species tends to grow in brightly-lit, very shallow places while ''Z. typus'' prefers deeper, shadier habitats. Also, the upper and lower surfaces of the thallus of ''C. adspersa'' appear similar, but ''Z. typus'' has a distinctively-felted under surface.

Distribution and habitat

''Zanardinia typus'' is found in the northeastern

and the

, its range including southwestern Britain and Ireland, the Atlantic coast of France, Spain and Portugal, the western Mediterranean Sea, the

Adriatic Sea The Adriatic Sea () is a body of water separating the Italian Peninsula from the Balkan Peninsula. The Adriatic is the northernmost arm of the Mediterranean Sea, extending from the Strait of Otranto (where it connects to the Ionian Sea) to t ...

and the

Black Sea The Black Sea is a marginal mediterranean sea of the Atlantic Ocean lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bounded by Bulgaria, Georgia, Roma ...

. It grows on rock and silty boulders in the shallow

subtidal zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

at depths down to about .

Biology

Growth in this species is "trichothallic", meaning that it occurs at the base of the marginal hairs. The edge of the thallus is two cells thick, and in the growth zone, the cells divide several times to form a thickened area with an upper

cortex Cortex or cortical may refer to: Biology * Cortex (anatomy), the outermost layer of an organ ** Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the ''forebrain'' *** Motor cortex, the regions of the cerebral cortex i ...

with about five rows of cells, a central

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 ...

composed of long, thick-walled cells, and a lower cortex, with one or two rows of cells from which the rhizoids emerge. There is an alternation of generations in this brown alga into

sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...

s and

gametophyte A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

s, although these are similar in appearance. The reproductive organs differentiate on the upper surface of the thallus. The alga can also

reproduce vegetatively Vegetative reproduction (also known as vegetative propagation, vegetative multiplication or cloning) is any form of asexual reproduction occurring in plants in which a new plant grows from a fragment or Cutting (plant), cutting of the paren ...

, with cup-shaped new growths developing on old

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

References

{{Taxonbar, from1=Q19798267, from2=Q18472344 Brown algae Monotypic brown algae genera