Rhodophyta, Red Algae

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Laurencia obtusa (Hudson) Lamouroux

Rhodophyta, Order: Ceramiales; Family: Rhodomelaceae.

Etymology

The genus Laurencia is named after the French scientist

M. de La Laurencia. Obtusa, refers to the blunted round shape at the apex of the nipples.

Description

The Laurencia obtusa is a cartilaginous alga with elongated, soft nipples. The tip of each nipple is orange and round. Microscopic examination reveals the nipple tip to be sunken, and a tuft of hair may be found in its centre.

Size

The Laurencia obtusa is smaller than the Laurencia papillosa, its length not more than 5 cm and sometimes even less. Elsewhere, the alga grows larger.

Colour

Small lumps in shades of brown tending towards pink.

Special features

The Laurencia obtusa is easily mistaken for the Laurencia papillosa and for the Chondria dasyphylla. The Chondria dasyphylla, however, is characterized by a unique bouquet of tiny nipples arranged around the central nipple. The branches of the Laurencia obtusa nipples are more sparse and softer than those of the Laurencia papillosa and, when extracted from the water, they bend.

 

 

Habitat

The Laurencia obtusa is to be found in tidal pools and in the subtidal zone. Dr. Edelstein reported individuals at a depths of 80 m. 

Biology and reproduction

The Laurencia obtusa has a three-stage life cycle. Reproductive tetraspores are whorled, forming a ring at some distance from the nipple.

Seasonality and distribution

This species is rarer that the Laurencia papillosa, although it, too, can be found the year round. The species is widely distributed throughout the world, especially in warm seas. It can be found in the Mediterranean, the Atlantic Ocean, Biology and reproduction the Indian Ocean and the Pacific Ocean.

Additional species

See catalogue on Laurencia papillosa.

 

A relatively large body of research exists regarding the substances contained in the Laurencia obtusa. Some are antibiotic; others inhibit the cell division and the development of marine wildlife, including sea urchins. The Laurencia obtusa also contains concentrates that are toxic to insects, indicating economic options for developing pesticides. Analysis in Jordan of individuals harvested in the Red Sea indicates agar production potential from both species - Laurencia obtusa and Laurencia papillosa.

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