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Jania rubens (Linnaeus) Lamouroux
Le Jolis
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RHODOPHYCEAE
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(reddish coral weed)
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| Photo details | ||
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Large plant formed as a result of prolific stoloniferous adventitious growth in a sheltered tide-swept environment. Scale: Growth width approximately 10 cm. Location:The Narrows, The Fleet, Dorset - Photographer:Francis Bunker - Date:22/07/2002 - Identified By:Francis Bunker - Verified By:C. Maggs |
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| Identification Notes | ||
| A species which occurs in two main varieties in the UK: Jania rubens var. rubens and Jania rubens var. corniculata. These two varieties are distinguished by shape of the calcified segments and branch interval. Both occur in diverse growth forms ranging from neat dichotomously branched fans up to 25 mm long to tangled masses over 10 cm in diameter formed by the proliferation of stolon-like adventitious branches. The simple growth form is a dichotomously branched tuft of fronds up to 25 mm long attached by a crustose base up to 600 µm in diameter which is sometimes obscured by stolons. In J. rubens var. rubens, branches occur at intervals of one to two calcified segments which are terete (or subterete) and un-lobed with occasional small lobes on the lowermost segments. The segments are 350 to 1000 µm long and 90 to 240 µm in diameter. (Segments can be up to 350 µm in diameter in basal parts and as little as 50 µm in diameter in stolons). In J. rubens var. corniculata branches occur at intervals of 1 to 6 segments which are wedge-shaped with distally bearing short projecting lobes up to 250 µm long and sometimes branches (although these lobes are obscured by unlobed fertile regions in summer). Plants are coarse and stony but delicate and a pale pink colour readily bleaching to white in bright sunlight. Other characterising features: Plants are monecious with reproductive structures within swollen segments of the plant. J. rubens var. rubens: Spermatangial segments are unlobed, terminal segments 110 to 150 µm in diameter and 170 to 225 µm long. Carpogonial segments are lobed and similar in diameter but 110 to 115 µm long. Tetrasporangial segments are lobed and larger, 225 to 240 µm in diameter and 260 to 340 µm long. J. rubens var. corniculata Spermatangial segments are unlobed and terminal 75 to 140 µm in diameter and 200 to 260 µm long. Carpogonial segments are lobed and larger, 150 to 285 µm in diameter but 80 to 110 long. Tetrasporangial segments are larger, 225 to 240 µm in diameter and 260 to 340 µm long. In both varieties, tetrasporangial and carpogonial conceptacles can bear segmented lobes and are sometimes catenate. Irvine and Chamberlain, 1994 |
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| Confusion | ||
| Haliptilon virgatum has been confused with J. rubens var. corniculata but the former has pinnate branches borne on unlobed segments. ngifurca is a more robust species which has been reported as far north as Brittany and might possibly be encountered in SW Britain. |
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| Habitat | ||
| Epiphytic, mainly on Cladostephus, Cystoseira and Halopithys in the British Isles (other substrata further south). Upper sublittoral to 8 m. |
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| Recorded distribution | ||
| Jania rubens var. rubens has an overall western distribution in mainland Britain northwards to western Inverness. Most Irish records are from the south and west coasts. J. rubens var. corniculata is confined to the south-west of the British Isles. |
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| Researched by | ||
| F. Bunker / Linda Irvine |
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| Synonyms | ||
| Acknowledgements | ||
| Linda Irvine |
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Additional Photos
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| Large plant formed as a result of prolific stoloniferous adventitious growth in a sheltered tide-swept environment. Scale: Growth width approximately 10 cm. Location:The Narrows, The Fleet, Dorset - Photographer:Francis Bunker - Date:22/07/2002 - Identified By:Francis Bunker - Verified By:C. Maggs | ||
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