Rhodophyta, Red Algae
Spyridia Harvey 1833
Rhodophyta, Order: Ceramiales; Family: Ceramiaceae.
The name of the genus means ‘basket’. The species name of Spyridia hypnoides describes the hooked edges of the alga, and the species name, Spyridia aculeatea, describes its sharpened edges.
The Spyridia is a light, thin and delicate alga that is branched and resembles a bush. Its thallus is soft and flexible. The branches are knit together, and the skeleton is loose. The Spyridia loses its shape when extracted from the water. Through a microscope, the branches are revealed to be composed of dense cells. Sometimes, rings can be seen containing colour, as is typical among Ceramiales; however, the Spyridia’s rings are distanced from each other.A central axis made of colourless cells passes through the centre of the thallus.
The central branches are up to 1 mm in diameter. The side branches are thinner and shorter. The entire bush reaches a length of 10-15 cm.
The algal colour is light and faded. Sometimes there is an addition of faded green, brown or pink.
The thallus’ soft touch and its light colour are characteristic. The alga may be confused with the Dasya, which is also soft but darker. Microscopic examination requires observation of large plant sections to prevent confusion with other species of the Ceramiaceae family.
The Spyridia can be found in the upper regions of the intertidal zone. It is mostly found on abrasion platforms, usually close to the sides above the water line and far from the wave break. The Spyridia sometimes appears as an epiphyte upon other species.
Biology and reproduction
The Spyridia has a three-stage life cycle. The dark red and globular sporangium, the cystocarps, are parasitic on the female gametophyte, and spread along its branches. Reproductive spores are located on the rings. Often, ring concentrations can be seen using a magnifying glass.
Seasonality and distribution
The Spyridia can be found year round, although waves of population are felt: the amount of Spyridia decreases during winter and increases in summer. The Spyridia can be found almost everywhere in tropical and subtropical seas.
The Spyridia genus includes about fifteen species. In our region, two have been reported. The Spyridia filamentosa (Wulfen) Harvey and Spyridia hypnoides (Bory) Papenfuss which was formerly known as Spyridia aculeata (C. Agardh and Decaisne) Kutzing . Both species are generally similar, and a magnifying glass or microscope is required to discern the two. The Spyridia hypnoides’ branches are hooked and (through a microscope) one may see the difference in branch edges (see diagram). The Spyridia’s branch tips are sharp, whereas those of the Spyridia hypnoides end in three tips each. The Spyridia hypnoides migrated from the Red Sea, and is more common in the south of the country, especially during the warmer months. The Spyridia aculeata is more common and found on nearly any rocky beach in the Eastern Mediterranean.