Rhodothamniella floridula

Researched By	Karen Riley	Data Supplied By	MarLIN
Refereed by	This information is not refereed.
Taxonomy
Scientific name	Rhodothamniella floridula	Common name	A red seaweed
MCS Code	ZM182	Recent Synonyms	Rhodochorton floridulum, Audouinella floridula
Phylum	Rhodophycota	Subphylum
Superclass		Class	Rhodophyceae
Subclass	Florideophycidae	Order	Palmariales
Suborder		Family	Rhodothamniellacae
Genus	Rhodothamniella	Species	floridula
Subspecies
Additional Information
Taxonomy References	Howson & Picton, 1997, Fish & Fish, 1996
General Biology
Growth form	Cushion, Turf, Mat	Feeding method	Photoautotroph
Mobility/Movement	Permanent attachment	Environmental position	Epibenthic, Epilithic, Epiphytic
Typical food types	Not relevant	Habit	Attached
Bioturbator	Not relevant	Flexibility	High (>45 degrees)
Fragility	Intermediate	Size	Small-medium(3-10cm)
Height	Up to 3 cm	Growth Rate
Adult dispersal potential	None	Dependency	Independent
Sociability	Colonial
Toxic/Poisonous?	No
Additional Information	Rhodothamniella 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 & Ireland	Rhodothamniella floridula occurs on the coast of Scotland, the north east, south and south west coasts of England and in Wales and Northern Ireland.
Global distribution	Occurs in northwest Europe
Biogeographic range	Not researched	Depth range	Littoral to 5m
Migratory	Non-migratory / Resident
Distribution Additional Information	Rhodothamniella 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 preferences	Bedrock, Large to very large boulders, Small boulders, Rockpools	Physiographic preferences	Open coast, Enclosed coast / Embayment, Strait / sound
Biological zone	Upper Littoral Fringe, Lower Littoral Fringe, Upper Eulittoral	Wave exposure	Moderately Exposed, Sheltered, Very Sheltered
Tidal stream strength/Water flow	Moderately Strong (1-3 kn), Weak (<1 kn)	Salinity	Full (30-40 psu)
Habitat 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 type	Oogamous	Developmental mechanism	Spores (sexual / asexual)
Reproductive Season	Insufficient information	Reproductive Location	Insufficient information
Reproductive frequency		Regeneration potential	No
Life span	6-10 years	Age at reproductive maturity	Insufficient information
Generation time	Insufficient information	Fecundity	Insufficient information
Egg/propagule size	Insufficient information	Fertilization type	Insufficient information
Larvae/Juveniles Larval/Juvenile dispersal potential Insufficient information Larval settlement period Insufficient information Duration of larval stage Insufficient information
Additional Information	Life 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) Fecundity 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