Notheia Anomala

''Notheia anomala'' is a macroalga in the family Notheiceae and the brown algae order Fucales. It is an obligate epiphyte of another brown algae, ''Hormosira banksii.''

Distribution

''Notheia'' is native to New Zealand and southeastern Australia, matching the distribution of its host '' Hormosira''.

Description

''Notheia'' is a small, branching brown macroalga (order Fucales).

Epiphytism and ecology

''Notheia'' is believed to be an obligate epiphyte of ''Hormosira banksii'', although there is a single unconfirmed observation of ''Notheia'' attached t
''Xiphophora chondrophylla''
.Gibson, G., & Clayton, M. N. (1987). Sexual reproduction, early development and branching in ''Notheia anomala'' (phaeophyta) and its classification in the Fucales. Phycologia, 26(3), 363-373.Raven, J. A., Beardall, J., Johnston, A. M., Kuebler, J. E., & McInroy, S. G. (1996). Inorganic carbon acquisition by Xiphophora chondrophylla (Phaeophyta, Fucales). Phycologia, 35(2), 83-89. '' Hormosira'' is also from the order Fucales - and it is rare to have an epiphyte so closely related to its host. ''Notheia'' growth appears to be entirely dependent upon its host. Attempts to grow ''Notheia'' in culture were unsuccessful until ''Hormosira'' extracts were included.Hallam, N. D., Clayton, M. N., & Parish, D. (1980). Studies on the association between ''Notheia anomala'' and ''Hormosira banksii'' (Phaeophyta). Australian Journal of Botany, 28(2), 239-248.

The costs to ''Hormosira'' in this relationship are still unclear. Although the tissues of ''Hormosira'' are pushed up tightly against the thallus of ''Notheia'', which gives the impression that ''Notheia'' emerges from deep within the host, there are no plasmodesmata observed between adjacent ''Notheia'' and ''Hormosira'' cells. Similarly, the benefits that ''Notheia'' obtains from attaching to '' Hormosira'' are also unclear. The fronds of '' Hormosira'' are weakly attached to the substratum and there is frequent dislodgement in storm events or periods of high wave energy – therefore the fronds that drift may offer long-distance dispersal to ''Notheia'' which could be a key mechanism for the distributional success of this speciesMcKenzie, P. F., & Bellgrove, A. (2009). Dislodgment and attachment strength of the intertidal macroalga Hormosira banksii (Fucales, Phaeophyceae). Phycologia, 48(5), 335-343. Capon et al. (1998) Capon, R. J., Barrow, R. A., Rochfort, S., Jobling, M., Skene, C., Lacey, E., Gill, J. H., Friedel, T., & Wadsworth, D. (1998). Marine nematocides: tetrahydrofurans from a southern Australian brown alga, Notheia anomala. Tetrahedron, 54(10), 2227-2242. highlighted for the first time that tetrahydrofurans from ''Notheia'' act as potent and selective inhibitors of the larval development of parasitic nematodes, which may be a positive effect that ''Hormosira'' receives from this symbiotic relationship. ''Notheia'' has a higher photosynthetic capacity than its host ''Hormosira'', probably because of its greater surface area or smaller allocation to chemical defences.Raven, J., Beardall, J., Johnston, A., Kübler, J., & Geoghegan, I. (1995). Inorganic carbon acquisition by ''Hormosira banksii'' (Phaeophyta: Fucales) and its epiphyte ''Notheia anomala'' (Phaeophyta: Fucales). Phycologia, 34(4), 267-277.

In natural populations of ''Hormosira'' in Australia, tide pools have a consistently higher proportion of infected plants with ''Notheia'' than the low shore reef populations. This pattern suggests that ''Notheia'' has narrower environmental tolerances than its host. Sexually mature ''Hormosira'' have been observed to carry more infections and that infections were usually most abundant on the conceptacles - usually next to the osteoles (conceptacles openings). Although ''Hormosira'' is dioecious, ''Nothiea'' does not appear to exhibit any preference towards settlement on male or female plants.

Analyses of ''Notheia'' biomass have shown a strong positive effect on invertebrate biodiversity.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. ''Notheia'' provides food, protection, and niche space for a large range of small invertebrates, which in turn are an important source of food for higher trophic levels.

Reproduction

''Notheia'' is monoecious and produces male and female gametangia in the same conceptacle. Female gametangia are present throughout the year, and they develop either on branched or unbranched stalks within the conceptacle, or directly from the walls of conceptacles. They contain 8 zooids each 10-12 µm long by 5-6 µm wide. About 4 hours after release via paraphyses, female gametes begin to settle. Male gametangia have been observed only between April and July ( Southern Hemisphere, Australia). They are borne in a similar manner to the female gametangia, and contain 64 zooids, each 5 µm long by 2-3 µm wide.

Both gametes are pyriform in shape (pear form) with two laterally inserted flagella (the anterior one longer than the posterior). They each possess one eyespot - and have never been observed to contain two or more. Male and female gametes freely intermingle within a conceptacle, but as long as female gametes are motile, males are not attracted to them. About 4 h after release, female gametes settle on surrounding ''Hormosira'' tissue, and once that has occurred, the male gametes are then attracted to the settled female gametes.

References

{{Taxonbar, from=Q26816833
Fucales