Polyides rotunda explained

Polyides rotunda is a species of small red marine alga in the family Polyidaceae.

Description

Polyides rotunda grows to 20cm (10inches) in length, its cartilaginous, terete and branches two or three times dichotomously. The branches are about 2mm in diameter reaching a uniform height. The holdfast is disc like. In colour it is purplish red.^{[1] [2]}

Habitat

Generally epilithic in rock pools in the littoral and upper sublittoral.^[1] Sand tolerant.^[3]

Distribution

Generally distributed around Ireland, Great Britain, the Isle of Man and the Channel Islands.^[4]

Reproduction

Polyides rotunda is dioecious. The spermatangial cells develop in swollen areas near the apices. Cystocarps develop near the apices.^[1] The tetrasporangia are cruciate, that is cross-shaped.^[5]

Similar species

Furcellaria lumbricalis (Hudson) Lamouroux is very similar but can be distinguished by the holdfast which has claw-like branches while that of Polyides being disc-like.^[6]

Notes and References

1. Dixon, P.S. and Irvine, L.M. 1977. Seaweeds of the British Isles Volume 1 Rhodophyta Part 1 Introduction, Nemaliales, Gigartinales British Museum (Natural History)
2. Jones, W.E. 1962. A key to the genera of the British seaweeds. Field Studies 1 (4) pp1 - 32
3. Lewis, J.R. 1964 The Ecology of Rocky Shores. The English Universities Press Ltd.
4. Bunkern F.StP, D., Brodie, J.A., Maggs, C.A. and Bunker, Ann. R.2017. Seaweeds of Britain and Ireland. Second Edition. Wild Nature Press, Plymouth.UK.
5. Newton,L. 1931 A Handbook of the British Seaweeds. British Museum (Natural History)
6. Jones, E.W. 1962. A key to the genera of the British seaweeds. Field Studies volume 1 no 4.pp1 - 32