Phaeophyta,  Order: Dictyotales; Family: Dictyotaceae.

Etymology

The generic name of the genus, Stypopodium, means ‘small foot’. The name of the species is dedicated to the German botanist G. W. Schimper.

Description

Young Stypopodium schimperi, like the padina, are fan- shaped. Mature individuals grow and divide into several sub-units that all emanate from a narrow, common base. Bowed, parallel concentric lines are evident along the algal breadth. These lines are darkly coloured and formed by sterile hairs that are rich in dark chlorophyll cells. The alga fastens on to the rock through a developed holdfast made of thin, dense filaments. Through a microscope, a line of apical cells can be seen at the edge of the thallus.

Size

Most individuals range in size from 5 to 15 cm. Large individuals measure up to 20 cm.

Colour

Outside the water, the Stypopodium schimperi is brown, as they appear in the records of the herbarium. In water, the alga attains a phosphorescent azure colour, sometimes turquoise or blue.

Special features

A remarkable feature of the alga is its phosphorescent colour, a brilliant turquoise, when immersed in seawater. As opposed to the padina, the Stypopodium does not calcify, and so its concentric lines do not condense. The edges of the thallus are not curled.

Habitat

In the past, the Stypopodium was usually found only as debris upon the beach and was thought to grow mainly in deep water. Lately, several plants have been spotted in shallow and deep potholes. The species apparently migrates and arrived from the Red Sea, now becoming more common along our shores, both in shallow and in deeper water. The Stypopodium schimperi, as a species, inhabits tropical and sub-tropical seas.

Biology and reproduction

The Stypopodium’s life cycle resembles that of other Dictyotales order members, and includes two externally similar generations: an asexual diploid generation that carries spores and is predominant, and a sexual haploid generation that carries reproductive organs. The reproductive organs develop adjacent to the concentric lines near the sterile hairs in groups of dense rows. The Stypopodium’s growth is stimulated by a row of vertex cells located at the upper edges of the alga.

The radiating phenomenon of marine organisms is noted in plants and creatures. In some cases, the source of light is a biological reaction (for example in the eyes of some fish); in coral, florescence is a result of changes in light-wave lengths; however, with regards to the Stypopodium, the source of the glowing colour is apparently the result of light diffracting upon hitting the alga. The turquoise is the structural colour, not unlike the metallic colours found on the wings of some insects.

Seasonality and distribution

The Stypopodium can be found throughout nearly the entire year. The alga is a characteristic of tropical and sub-tropical seas. In recent years it has become common along Mediterranean coasts. The Stypopodium grows in shallow water as well as at depths of several metres (15). I have spotted it along Israeli shores several times while diving along the Nahariya and Haifa coast. I have often found thallus that were torn and drifted to shore. I have also found individuals tied to the floors in shallow waters in Cyprus. The Jerusalem Herbarium has no examples of this alga from the Mediterranean; Tikva Edelstein, during the course of her work in deep Mediterranean waters, does not mention the species. Apparently, the Stypopodium has only recently penetrated the Mediterranean from the Red Sea, as have other species of algae and sea creatures.

Additional species

Two species of Stypopodium have been mentioned in this region, but the names are synonymous and refer to the same specie:

 

 

 

Stypopodium schimperi (Buchinger and  Kutzing ) Verlaque and Boudouresque = Stypopodium zonale (Lamouroux) Papenfuss.

Several studies have focussed on substances found in the Stypopodium’s thallus. The Stypopodium is poisonous to a large number of herbivores so the species of Acanthophora growing in its vicinity have been little eaten. A substance called Stypodione may be manufactured from the Stypopodium. The substance impedes cell division in sea-urchin embryos and sea mammals. Fish in an aquarium with Stypopodium will attempt to jump out and finally die. The active mechanism is unknown, but Stypodione does present medical and economic potential.