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Hildenbrandia rubra is a red alga responsible for rusty-looking stains on rocks and is only noticeable as red alga upon closer inspection.
The species is a crust-forming alga that adheres closely to the substrate. It is pinkish-red, dark red, or reddish-brown in color and has no surface markings.
The thin thallus (0.2–0.5 mm thick) forms an extensive crust with irregular contours on the surface of rocks, stones, and pebbles.
Hildenbrandia rubra forms In some areas, the crusts can reach a diameter of up to 15 cm.
Hildenbrandia rubra does not form rhizoids. Vegetative reproduction is rare; asexual reproduction occurs through the formation of various types of spores.
Sexual reproduction is unique in this group due to its passive, non-flagellated sperm (spermaties).
Habitat:
On rocks and stones in all tidal zones, often in the splash zone in caves and in the subtidal zone, widespread, extremely common, especially in the upper coastal zone, where it appears to be very tolerant of extreme temperatures, light conditions, and salinity levels.
Morphology
The red color results from the dominance of the pigments phycoerythrin and phycocyanin; these mask the other pigments chlorophyll a (no chlorophyll b), beta-carotene, and a number of unique xanthophylls.
Reproduction: Vegetative reproduction is rare; asexual reproduction occurs through the formation of various types of spores; sexual reproduction is unique in this group due to its passive, non-flagellated sperm (spermatia).
The alga is very tolerant of extreme temperatures, light conditions, and salinity levels and grows horizontally very slowly, often less than 1 mm/year.
Hildenbrandia rubra can even survive for several years after being overgrown by barnacles, mussels, and other macroalgae, which is attributed to its very low metabolic requirements.
The thin, crust-forming algae are a potential food source for limpets and periwinkles.
However, grazing can cause significant damage to the radula of these grazers compared to algae with much larger cells (e.g., Ulva spp.).
The red alga attempts to protect itself from marine snails by growing in cracks, crevices, and other refuges that are not easily accessible to snails (e.g., in the high zone, under mussels, or barnacles).
If Hildenbrandia rubra is grazed nonetheless, it can regenerate damaged tissue.
Synonyms:
Hildenbrandia nardiana Zanardini, 1839 · unaccepted (deleted in Algaebase)
Hildenbrandia nardoi Zanardini, 1840 · unaccepted
Hildenbrandia prototypus Nardo, 1834 · unaccepted (synonym)
Hildenbrandia rosea Kützing, 1843 · unaccepted (synonym)
Hildenbrandia rosea var. fuscescens Caspary, 1871 · unaccepted
Hildenbrandia sanguinea Kützing, 1843 · unaccepted
Rhododermis drummondii Harvey, 1844 · unaccepted (synonym)
Verrucaria rubra Sommerfelt, 1826 · unaccepted (synonym)
The species is a crust-forming alga that adheres closely to the substrate. It is pinkish-red, dark red, or reddish-brown in color and has no surface markings.
The thin thallus (0.2–0.5 mm thick) forms an extensive crust with irregular contours on the surface of rocks, stones, and pebbles.
Hildenbrandia rubra forms In some areas, the crusts can reach a diameter of up to 15 cm.
Hildenbrandia rubra does not form rhizoids. Vegetative reproduction is rare; asexual reproduction occurs through the formation of various types of spores.
Sexual reproduction is unique in this group due to its passive, non-flagellated sperm (spermaties).
Habitat:
On rocks and stones in all tidal zones, often in the splash zone in caves and in the subtidal zone, widespread, extremely common, especially in the upper coastal zone, where it appears to be very tolerant of extreme temperatures, light conditions, and salinity levels.
Morphology
The red color results from the dominance of the pigments phycoerythrin and phycocyanin; these mask the other pigments chlorophyll a (no chlorophyll b), beta-carotene, and a number of unique xanthophylls.
Reproduction: Vegetative reproduction is rare; asexual reproduction occurs through the formation of various types of spores; sexual reproduction is unique in this group due to its passive, non-flagellated sperm (spermatia).
The alga is very tolerant of extreme temperatures, light conditions, and salinity levels and grows horizontally very slowly, often less than 1 mm/year.
Hildenbrandia rubra can even survive for several years after being overgrown by barnacles, mussels, and other macroalgae, which is attributed to its very low metabolic requirements.
The thin, crust-forming algae are a potential food source for limpets and periwinkles.
However, grazing can cause significant damage to the radula of these grazers compared to algae with much larger cells (e.g., Ulva spp.).
The red alga attempts to protect itself from marine snails by growing in cracks, crevices, and other refuges that are not easily accessible to snails (e.g., in the high zone, under mussels, or barnacles).
If Hildenbrandia rubra is grazed nonetheless, it can regenerate damaged tissue.
Synonyms:
Hildenbrandia nardiana Zanardini, 1839 · unaccepted (deleted in Algaebase)
Hildenbrandia nardoi Zanardini, 1840 · unaccepted
Hildenbrandia prototypus Nardo, 1834 · unaccepted (synonym)
Hildenbrandia rosea Kützing, 1843 · unaccepted (synonym)
Hildenbrandia rosea var. fuscescens Caspary, 1871 · unaccepted
Hildenbrandia sanguinea Kützing, 1843 · unaccepted
Rhododermis drummondii Harvey, 1844 · unaccepted (synonym)
Verrucaria rubra Sommerfelt, 1826 · unaccepted (synonym)
