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Utricularia australis [Southern Bladderwort]


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Rørslett, B. 2013. Utricularia australis R.Br. (Lentibulariaceae). Southern Bladderwort. Flowers photographed in visible and ultraviolet light. http://www.ultraviol...rn-bladderwort/

 

Utricularia australis R.Br.

Syn. U. major Schmidel, U. neglecta Lehm.

NO: Vrangblærerot

SE: Sydbläddra

DK: Slank Blærerod

FI: Lännenvesiherne

EN: Bladderwort; Southern Bladderwort

 

A free-floating aquatic macrophyte, living entirely submerged except for its flowers that are air-borne, U. australis is widely distributed throughout Europe but becoming less frequent in the Nordic region. Since it flowers infrequently and in the vegetative state is quite similar to the much more common U. vulgaris, occurrences are probably highly underreported at least towards the North. This species, or very close relatives, is found in Asia and Australia as well and the now accepted species name originates from R. Brown's description of Austrialian material.

 

Like all other members of the genus Utricularia, U. australis is carnivorous and catches small water bugs and larvae with the specialised trap bladders richly present on its foliage.

 

The flowers are strongly zygomorphic and the lower lip-formed petal carries a bulge that closes access to the style and anthers inside. There is a short but massive spur adpressed to the lower petal lip. Only heavier pollinators, for example, bumblebees, can get access to pollen and nectaria.

 

Here is an overview to show the plant in its habitat. The inflorescences contain just a few bright yellow flowers on long scapes emerging into the air. U. australis flowers late in summer, in Norway typically in August. The lower petal is flat and basically almost circular, which sets it apart from the closely similar U. vulgaris having a much narrower and saddle-shaped lip; the flowers of the latter also are much darker yellow. Insufficient data on the ecology of these two Utricularia species exists, but the general impression is that U. australis prefers small moderately rich ponds, often with water stained by humic substances whilst U. vulgaris often grows in lakes not necessarily eutrophic ones.

 

Material for the image below from Ås, southern Norway, 14. Aug. 2010.

 

UTRI_AUS_B10081421082_VIS.jpg

Image reference:UTRI_AUS_B10081421082_VIS.jpg

Nikon D3S, Nikon 70-210 mm f/4 SE lens.

 

A close-up of the flowers to show their general shape. Plants collected near Fredrikstad, southern Norway, 3 Aug 2011.

 

UTRI_AUS_B1108037514_VIS.jpg

Image reference: UTRI_AUS_B1108037514_VIS.jpg

Nikon D3S, APO-Lanthar 125 mm f/2.5 lens.

 

The UV pattern of these flowers is very strong and confined to the prominent bulge of the lower lip. Here a concentration of conical cells occur as well, so the UV mark appears almost velvet-like under UV illumination.

 

UTRI_AUS_B1108034000_UV.jpg

Image reference: UTRI_AUS_B1108034000_UV.jpg

Nikon D40X, UV-Nikkor 105 mm f/4.5 lens, Baader U 2" (Venus) filter, SB-140 flash.

 

[Published: 16 Jan 2013]

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