Blue Ecosystems יעוץ סביבתי, בהנהלת ד"ר רחלי עינב - Jania rubens


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Rhodophyta | Chlorophyta | Rhodophyta
Jania rubens (Linnaeus) Lamouroux

Rhodophyta, Order: Coralliniales; Family: Corallinaceae.
The generic name (Jania) resonates with the name of the two-faced mythological Roman god, Janus. The species name describes the algal reddish colour.
The Jania rubens is a rigid, calcified alga, consisting of an entangled web of thin tubes coloured whitish pink. It is comprised of elongated joints and dichotomous branches. Its general shape is of a dense, rounded bush. Beached individuals or those exposed to the air for extended periods lose their pinkish color and turn white. A microscope is required to examine the algal anatomic structure. Also, the calcium must first be dissolved using acid.
The joints are 0.5 mm long and their width even less. The height of some algal clumps can reach 5 cm, but they are usually smaller.
The algal colour ranges between pink and white. Following dehydration and extended exposure to the sun, the pigments decompose and the alga turns white.
Special features
The Jania rubens is probably the most common alga in the Eastern Mediterranean intertidal zone. It may be confused with its neighbour, the Corallina, but is dichotomous and its thalli are thinner. There are also distinctions of habitat, and the Jania rubens has a wider distribution. Moreover, many individuals are epiphytes upon other alga, and often one may be found upon the other.
The alga is very common in the intertidal zone, but may also be found in deep water. The Jania rubens also develops on rocks and on other algae. It is quite aggressive in dominating other species in the zone. Any alga that decreases its growth rate is soon covered with Jania rubens. Often, within a cluster of Jania rubens, one may find remnants of another species that has been dominated.
Biology and reproduction
The sporophytes and gametophtes are similar in shape although, during their vegetative state, a certain dilation of joints may be observed. The sexual reproductive organs, as well as the reproductive spores, are located within closed, calcified organs. Those that contain the male reproductive cell (antheridia) are located on the edge of the branches, and the others are often in between the branches, and sometimes also at their edges. In England, it has been found that the Jania rubens life cycle is annual - the young individuals appearing in Spring, reproduction peaking in Summer and so on. It is not clear whether the same seasonal cycle occurs in the Eastern Mediterranean.
Several studies have been done in various places around the world, some that deal with the algal physiological structure. The Jania rubens life strategy is particularly interesting, since it enables it to be so opportunistic and prevalent in its habitat. Among other things, the alga has been found to have an impressive ability to absorb phosphorus from the water 25% faster than other species.
Seasonality and distribution
As mentioned above, the Jania rubens is the most prevalent alga in the Eastern Mediterranean intertidal zone. It can be found along the coast the year round. The alga is globally distributed, common in the Mediterranean, the Atlantic Ocean, the Indian Ocean and the Pacific Ocean.
Additional species
Other species reported in this region appear below. In the comprehensive study undertaken in England (Irvine and Chamberlain, 1988), researchers tended to combine the species due - among other reasons - to their wide divergence. Accordingly, they define Jania corniculata and Jania longifurca as a sub-species of Jania rubens.
Jania adhaerens Lamouroux
Jania corniculata (Linnaeus) Lamouroux Jania longifurca Zanardini
Jania micrarthrodia Lamouroux.
Species of Jania were used in Brazil to regulate blood sugar. The Jania is a primordial alga, and fossilized examples have been found from the Cretaceous period, eighty million years ago. Calcification in its branches
enabled the algal preservation to a higher degree than in other algae.

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