Chlorophyta, Green Algae
Caulerpa mexicana Sonder and Kützing
Chlorophyta, Order: Caulerpales; Family: Caulerpaceae.
Caulerpa, means ‘crawling stalk’. The species name refers to the country, Mexico, where it was apparently first classified.
The Caulerpa mexicana resembles the Caulerpa scalpelliformis but is more delicate. The indentations between the lobes are deeper and create the appearance of a compound leaf. The alga appears in several variations, but in spite of the various ecotypes, it is easy to identify. Through a microscope, lateral and vertical fibers can be seen that serve to brace the thallus. The thallus is a single, multi-nuclear cell with many chloroplasts and no walls (coenocytes).
The thallus length reaches 20-25 cm, and its width is about 1 cm. The axis at the centre of the thallus is 1-2 cm wide.
The algae are green and can be found along the entire spectrum, from light to dark green according to lighting and the algal condition.
The depth of the indentations between the lobes is more than three times their width, and they lend the alga the appearance of a compound ‘leaf’. It is easily confused with Caulerpa taxifolia that is widespread in the Western Mediterranean.
The alga can be found on rocks, potholes and in pools in the intertidal zone, but also in deep water. The Caulerpa mexicana has been reported at depths of over 50 m.
Biology and reproduction
The life cycle is similar to Caulerpa prolifera. Rarely is it found with white reproductive organs on the axis of the leaf-like thallus.
Seasonality and distribution
The Caulerpa mexicana is extant throughout the year. During certain seasons, the thallus is entirely consumed and only the extensions remain clinging to the rock. From these the plant later regenerates. The species is particularly widespread in warm seas.
Another name for the Caulerpa mexicana is C. crassifolia (C. Agardh) J. Agardh. Globally, about sixty species of Caulerpa can be found in a variety of habitats: upon rocky, sandy or silty substrates
In recent years, large colonies of Caulerpa taxifolia, which resemble Caulerpa mexicana, have flourished in the Western Mediterranean. It is unclear whether these individuals migrated from other places naturally or were artificially distributed from an aquarium. In any case, the damage to local colonies of plants and marine wildlife in the Western Mediterranean is great and demonstrates the precarious sensitivity of marine systems, specifically those in the Mediterranean, to the deeds of man.