Rhodophyta,  Order: Ceramiales; Family: Rhodomelaceae.

Etymology

Acanthophora refers to the Greek term for ‘pedicle vehicle’, and the species name -najadiformis - was chosen due to its resemblance to the Najas (Naiad) -a water plant. The researcher Alire Raffeneau-Delile, who visited the coasts of Palestine as a member of a scientific expedition that accompanied Napoleon Bonaparte, was the first to describe the Acanthophora najadiformis. The scientific name for the species appears in various forms, named after the scientist who first classified it: Acanthophora delilei Lamouroux or Acanthophora nayadiformis (Delile) Papenfuss = Acanthophora najadiformis (Delile) Papenfuss, all referring to the same species.

Description

The Acanthophora najadiformis is an erect alga, rigid, very widespread and bushy. The cartilaginous branches are overlaid with prickly protrusions that can be seen by the naked eye, but better with a magnifying glass.

Size

The branches grow as long as 20 cm, but usually no more than 10 cm. They are 1-2 mm in diameter, and the pedicles are no more than 0.5 mm long.

Colour

In spite of their belonging to the red division, the Acanthophora appear in various shades of brown - from dark to light. Olive-green individuals may also be found.

Special features

It is possible to confuse the Acanthophora with the Hypnea, since they both grow along the edges of the abrasion platforms; however, the side branches of the Acanthophora are more regular in shape than those of the Hypnea, which are thinner, more elongated and often hook-like.

Habitat

The Acanthophora is common along the sea-facing rims of abrasion platforms. It grows in an especially narrow boundary between the tidal levels, in the region exposed to wave-activity and to air.

Biology and reproduction

The reproductive organs are located within the spine’s perimeter. Two types of reproductive organs can be identified: carpospores - spores formed as a result of sexual reproduction that are located within the cystocarps; these are transparent, vase-like sporangium and wide at the bottom, through which the spores can be seen; and reproductive spores (tetraspores) - spores generated by asexual division of the mother cell into four spores. The reproductive spores are immersed amongst the branches. They are elliptical and smaller than the carpospores. Reproduction is through a three-stage life cycle.

As mentioned, the Acanthophora can be found in a short horizontal section of the habitat. It is not found in deep water and does not rise from the depths, but most of the population remains attached to the low-tide line, in regions usually moistened by waves. The rates of photosynthesis and growth improve upon exposure to air (a factor of x 5). It seems that its inferior photosynthetic ability, and not the presence of alga-eating fish, is the primary reason for scarcity in deeper water. Fish do eat Acanthophora, but this does not seem to be their preferred source of sustenance.

Seasonality and distribution

Acanthophora may be found throughout the year, although the majority of individuals disappear in the winter and reappear in summer. The genus includes species that are present in warm water.

Additional species

The species Acanthophora muscoides (Linnaeus) Bory de Saint-Vincent, has been reported in Turkey.