Chlorophyta, Green Algae

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Dasycladus vermicularis (Scopoli) Krasser = Dasycladus clavaeformis (Roth) C. Agardh

Chlorophyta, Order: Dasycladales; Family: Dasycladaceae.

 Etymology

Dasycladus means ‘hairy branch’; the name of the species, vermicularis, denotes the club-like shape.

Description

The Dasycladus vermicularis is a leaf-like, spongy, cylindrical, unbranched alga. It widens from its base and towards its upper, rounded tip. The connection to the substrate is through a vertical rhizoid. A lateral microscopic cross-section of the alga reveals a central axis, around which branches are arranged that split into secondary branches (see illustration). The branch edges form a velvety surface pointed outwards. The alga mostly appears in small groups, but also in larger groups.

Size

The height of the algae in the Eastern Mediterranean varies between 2 and 7 cm. Its width at the top reaches 5-7 cm. In the Western Mediterranean, larger Dasycladus individuals can be found.

Colour

The Dasycladus vermicularis is dark green.

Special features

The Dasycladus vermicularis is easy to identify, since it resembles no other alga. It is often difficult to find the Dasycladus, since it is covered in sand. Dried individuals colour paper brown.

 

 

Habitat

The alga develops in shaded, protected areas, in which water displacement is low, such as lagoons or on the floor of potholes. In other places, the Dasycladus has been reported as a shallow-water alga, but in the Mediterranean, findings at depths of 70 m and beyond have been reported. The Dasycladus vermicularis can also be found on rocky substrates, as well as upon sandy floors.

Biology and reproduction

The thallus is constructed as a unit with no lateral walls. Its only reproductive mode is sexual. The cellular nucleus divides by meiosis into several haploid nuclei. The nucleus wander towards tiny cysts created in fertile whorls found across the alga. The cysts are dark and contain nuclei and chloroplasts. The cysts release dozens of mobile, double- flagellate reproductive cells. The alga is dioecious. Two

reproductive cells, equal in size, form a zygote that germinates directly into a new thallus.

Seasonality and distribution

The Dasycladus can be found during nearly all months of the year. Reproductive cells have been observed in December. In Cyprus, the alga is more common, especially in slightly polluted areas. There, it develops in places exposed to the sun, and individuals are larger on average than those found along Eastern Mediterranean shores. The global distribution of the species includes the Mediterranean and the Atlantic Ocean.

Additional species

In spite of the difference in individual size, there is only one species in this genus (with two aliases.(

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