Hormosira
| Hormosira banksii | |
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| Young Hormosira | |
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| Genus: | Hormosira |
| Species: | H. banksii
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| Binomial name | |
| Hormosira banksii | |
Hormosira banksii, also known as Neptune's necklace, Neptune's pearls, sea grapes, or bubbleweed) is a species of seaweed (brown algae, Fucales) native to Australia and New Zealand.[2] The genus Hormosira is monotypic.
Distribution
Hormosira is native to southeastern Australia (including Tasmania) and New Zealand.[1][2][3] Despite substantial morphological variation across its range, the species represents a single species and the genus Hormosira is monotypic.[3]
Description
Hormosira is a species of seaweed (brown algae, Fucales).[2] It is abundant on low-energy rocky reefs within the intertidal zone, where it outcompetes other algal species due to its high tolerance to desiccation. The thallus of the species is made up of strings of olive-brown, spherical, gas-filled pneumatocysts, which taper towards a small holdfast that is easily dislodged from the substrate.[4] The spheres are buoyant and rise to the surface of the water during high tide, allowing plants to move with the flow of the current and obtain more sunlight. Hormosira also produces a slime layer to reduce desiccation, and plants often grows in high densities, which reduces their surface area exposed to the sun and further reduce dehydration.[5] Given the buoyant thallus, Hormosira plants can drift out to sea over considerable distances, and floating plants can remain fertile for several weeks.[3] Plants vary significantly in morphology.[3]
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High densities of Hormosira on a broad rocky platform in Kaikōura, New Zealand -
High densities of Hormosira at Long Reef, Sydney, Australia -
Hormosira at Eaglehawk Neck, Tasmania, Australia -
Hormosira growing alongside a petrified log at Curio Bay, Otago, New Zealand
Reproduction
Hormosira reproduces sexually and is monoecious. The sex organs (conceptacles) are on the surface of the beads, and are visible to the naked eye as rough-looking dimples.[6] Hormosira produces eggs throughout the year, but its peak reproduction is often confined to July–October (at least in northern New Zealand) when the sea temperature is around 14 °C, as the viability of the eggs can be low in high sea temperatures such as 17–22 °C.[7] At high tide, the eggs are released directly into the surrounding water. The eggs are negatively buoyant they sink to the substrate to develop for several days before becoming attached.[3] All individuals release at the same time, maximising fertilisation. The species can also reproduce asexually from broken and dislodged fragments.
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Female conceptacle -
Male conceptacle
Ecology
Hormosira often occurs in large patches and outcompetes other algal species due to its high tolerance to desiccation. Hormosira is a food source for sea urchins, many small crustaceans, and some juvenile fish. Young crustaceans and molluscs often rely on the dense canopies of Hormosira for niche space, protection from predators, and avoid desiccation at low tide. Hormosira provides a substrate for sessile organisms to attach onto, including sea urchins and a wide range of facultative and obligate algal epiphytes such as Notheia anomala. This is beneficial to many organisms as competition for habitat space is a primary limiting factor in the intertidal environment.[8]
References
- ^ a b Huisman, J.M. (2000). Marine Plants of Australia. University of Western Australia Press, Australian Biological Resources Study. ISBN 978-1-876268-33-6.
- ^ a b c W. A., Nelson (2013). New Zealand seaweeds : an illustrated guide. Wellington, New Zealand: Te Papa Press. p. 70. ISBN 9780987668813. OCLC 841897290.
- ^ a b c d e Mueller, Rebecca; Wright, Jeffrey T.; Bolch, Christopher J.S. (2018). "Historical demography and colonization pathways of the widespread intertidal seaweed Hormosira banksii (Phaeophyceae) in southeastern Australia". Journal of Phycology. 54: 56–65. doi:10.1111/jpy.12599.
- ^ Schiel, D.R.; Taylor, D.I. (1999). "Effects of trampling on a rocky intertidal algal assemblage in southern New Zealand". Journal of Experimental Marine Biology and Ecology. 235 (2): 213–235. doi:10.1016/S0022-0981(98)00170-1.
- ^ "Neptunes Necklace". Pathwayz. Pathwayz. Retrieved 3 May 2021.
- ^ "Neptune's necklace". na.oceana.org. Retrieved 17 March 2011.
- ^ Begum, M.; Taylor, F.J. (1991). "Seasonal egg liberation and potential output of Hormosira banksii". Pakistan Journal of Botany. 23: 145–151.
- ^ Thomsen, M.S.; Metcalfe, I.; South, P.; Schiel, D.R. (2016). "A host-specific habitat former controls biodiversity across ecological transitions in a rocky intertidal facilitation cascade". Marine and Freshwater Research. 67 (1): 144–152. doi:10.1071/MF14152.
External links
- Neptune's necklace discussed in RNZ Critter of the Week, 31 Jul 2020