BIOTIC Species Information for Rhodothamniella floridula
Researched byKaren Riley Data supplied byMarLIN
Refereed byThis information is not refereed.
Scientific nameRhodothamniella floridula Common nameA red seaweed
MCS CodeZM182 Recent SynonymsRhodochorton floridulum, Audouinella floridula

PhylumRhodophycota Subphylum
Superclass ClassRhodophyceae
SubclassFlorideophycidae OrderPalmariales
Suborder FamilyRhodothamniellacae
GenusRhodothamniella Speciesfloridula

Additional Information
Taxonomy References Howson & Picton, 1997, Fish & Fish, 1996,
General Biology
Growth formCushion
Feeding methodPhotoautotroph
Mobility/MovementPermanent attachment
Environmental positionEpibenthic
Typical food typesNot relevant HabitAttached
BioturbatorNot relevant FlexibilityHigh (>45 degrees)
FragilityIntermediate SizeSmall-medium(3-10cm)
HeightUp to 3 cm Growth Rate
Adult dispersal potentialNone DependencyIndependent
General Biology Additional InformationRhodothamniella floridula is perennial. The hair-like filaments are approximately 20-25µm in diameter. The species has been noted to trap sand and mud in a layer up to 5cm thick (Lobban & Wynne, 1981).

Dixon & Irvine (1977) observed that the growth of Rhodothamniella floridula (as Audouinella floridula) is much faster in winter, whilst in the summer the spongy cushion can become bleached or disrupted.
Biology References Hayward et al., 1996, Lobban & Wynne, 1981, Connor et al., 1997(b), Dixon & Irvine, 1977,
Distribution and Habitat
Distribution in Britain & IrelandRhodothamniella floridula occurs on the coast of Scotland, the north east, south and south west coasts of England and in Wales and Northern Ireland.
Global distributionOccurs in northwest Europe
Biogeographic rangeNot researched Depth rangeLittoral to 5m
MigratoryNon-migratory / Resident   
Distribution Additional InformationRhodothamniella floridula has been found on substrata other than sandy rock. For example, in St. Andrews Bay, Rhodothamniella floridula (as Rhodochorton spp.) occurred in tufts on %Halidrys siliquosa% (a brown seaweed) and in pools where %Fabricia sabella% (a polychaete worm) was common (Laverack & Blackler, 1974). In Co. Kerry, Ireland Rhodothamniella floridula (as Audouinella floridula) was also found growing on peat masses, where it binds the peat and sand together (Murphy, 1981).

Substratum preferencesBedrock
Large to very large boulders
Small boulders
Physiographic preferencesOpen coast
Enclosed coast / Embayment
Strait / sound
Biological zoneUpper Littoral Fringe
Lower Littoral Fringe
Upper Eulittoral
Wave exposureModerately Exposed
Very Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
SalinityFull (30-40 psu)
Habitat Preferences Additional Information
Distribution References Murphy, 1981, Hayward et al., 1996, Connor et al., 1997(b), Dickinson, 1963, Dixon & Irvine, 1977, Laverack & Blackler, 1974, Hardy & Guiry, 2003,
Reproduction/Life History
Reproductive typeOogamous
Developmental mechanismSpores (sexual / asexual)
Reproductive SeasonInsufficient information Reproductive LocationInsufficient information
Reproductive frequency Regeneration potential No
Life span6-10 years Age at reproductive maturityInsufficient information
Generation timeInsufficient information FecundityInsufficient information
Egg/propagule sizeInsufficient information Fertilization typeInsufficient information
Larval/Juvenile dispersal potentialInsufficient information Larval settlement periodInsufficient information
Duration of larval stageInsufficient information   
Reproduction Preferences Additional InformationLife span
No information was found concerning the longevity of Rhodothamniella floridula. However, it is likely to have a life span of 5-10 years, similar to other red seaweeds, such as Furcellaria lumbricalis.

Reproductive type
Dickinson (1963) and Dixon & Irvine (1977) found that asexual Rhodothamniella floridula (as Rhodochorton floridulum and Audouinella floridula respectively) plants bear cruciate tetrasporangia. The tetrasporangia are ovoid and are arranged on the upper parts of the erect axes, occurring singly or in clusters (Dixon & Irvine, 1977). Stegenga (1978) found that tetraspores of cultured Rhodothamniella floridula (as Rhodochorton floridulum) measured up to 35 x 30 µm. He also noted that these were formed under all combinations of temperatures from 4 °C to 16 °C at any length of daylight. A tetrasporophyte, rather than a carposporophyte, of Rhodothamniella floridula (as Rhodochorton floridulum) develops directly from the fertilised carpogonium with only one erect filament and one rhizoid (Lobban & Wynne, 1981, Cole & Sheath, 1990). Stegenga (1978) observed that gametophytes of Rhodothamniella floridula (as Rhodochorton floridulum) were unisexual and possessed a unicellular base from which only one filament arose. It is also known that the subclass Florideophyceae specialise in oogamous reproduction in which the zygote is returned on the female gametophyte, giving rise to complex post-fertilisation development, known as the carposporophyte. Observations on Rhodothamniella floridula (as Rhodochorton floridulum) showed that the tetraspores germinate to give gametangial plants which were small compared with the tetrasporangial phase (Knaggs & Conway, 1964)

Red algae are typically high fecund, but their spores are non-motile (Norton, 1992) and therefore highly reliant on the hydrodynamic regime for dispersal. Stegenga (1978) noted that tetrasporangia germinated in 'rather low numbers', but most abundantly at high temperatures and long days.

Timing of reproduction
Dixon & Irvine (1977) noted that the greatest abundance of tetrasporangia occurred between November and March. Furthermore, Rhodothamniella floridula (as Rhodochorton spp.) are present throughout the year (Laverack & Blackler, 1974). However, Stegenga (1978) found that there were no tetrasporangia present during the winter.
Reproduction References Lobban & Wynne, 1981, Stegenga, 1978, Dickinson, 1963, Dixon & Irvine, 1977, Cole & Sheath, 1990, Knaggs & Conway, 1964, Norton, 1992, Laverack & Blackler, 1974,
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