Species

Trithuria inconspicua

Etymology

inconspicua: inconspicous

Common Name(s)

Hydatella

Current Conservation Status

2012 - Threatened - Nationally Endangered

Conservation status of New Zealand indigenous vascular plants, 2012
The conservation status of all known New Zealand vascular plant taxa at the rank of species and below were reassessed in 2012 using the New Zealand Threat Classification System (NZTCS). This report includes a statistical summary and brief notes on changes since 2009 and replaces all previous NZTCS lists for vascular plants. Authors: Peter J. de Lange, Jeremy R. Rolfe, Paul D. Champion, Shannel P. Courtney, Peter B. Heenan, John W. Barkla, Ewen K. Cameron, David A. Norton and Rodney A. Hitchmough. File size: 792KB

Previous Conservation Status

2009 - Threatened - Nationally Vulnerable
2004 - Serious Decline

Qualifiers

2012 - EF, PD, RR
2009 - RR

Authority

Trithuria inconspicua Cheeseman

Family

Hydatellaceae

Flora Category

Vascular - Native

Structural Class

Dicotyledonous Herbs other than Composites

Synonyms

Hydatella inconspicua (Cheeseman) Cheeseman

Distribution

Endemic. New Zealand. North Island ( confined to Northland where it is known from western dune lakes from near Awanui to the Pouto Peninsula), South Island (western Southland and Fiordland lakes).

Habitat

An aquatic of shallow to medium depth (5-7m) freshwater lakes (exact depth range dependant on water quality and light levels). Preferring reasonably stable substrates but has been found growing in fine sand, gravel and organic muds. Apparently intolerant of surrounding taller vegetation. Mature plants are often partially buried in sediment so that only their upper most leaf tips are exposed.

Features

Diminutive, aquatic plant forming small tussocks 20–40 mm tall. Roots numerous, white up to 0.2 mm diameter. Foliage often almost completely buried/obscured in lake sediment and algae, such that only the tips protrude. Leaves numerous, 0.5 mm wide, linear-filiform, appearing septate, basal portion (or that buried within sediment/algae) white, hyaline-transparent, exposed portion dark green-brown or red-brown, apex acute, base not sheathing but broader than apex. Scapes 0.2 mm diameter, bright red below inflorescences, initially 2–3 mm long, elongating in fruit to c. ¾ the length of the leaves, or the same length as the leaves. Floral bracts 2–5, 3–5 mm long, thin and membranous, ovate-lanceolate, acute, with a central nerve; occasionally with one pair of bracts not fully developed and filiform, or one of the second pair absent, the other filiform. Male flowers conspicuous, 2–8 per inflorescence, bright red, filaments 10 mm long, anthers 1 mm long. Female flowers 10–24 per inflorescence, ovary c. 0.5 × 0.4 mm, yellow-brown, with 5–10 unequal delicate styles bunched at apex. Some plants bearing "perfect flowers" with 2–4 male and 1–5 female flowers may occur within populations, the proportion of these varies. Fruit elliptic ovoid, red-brown.

Similar Taxa

Trithuria is most likely to be confused with some of the spike rushes (Eleocharis spp.) and species of Centrolepis. From these Trithuria differs by its submerged flowering habit, with the male and female flowers usually separate; by the male flowers which have much longer filaments and 2-celled anthers; and by the female flowers which have septate styles are septate. Vegetative material of Trithuria differs from Centrolepis in that the leaves are not sheathed. Trithuria could be confused with sterile plants of Eleocharis pusilla, however, E. pusilla has uniformly bright green leaves arising from a creeping rhizome.

Flowering

October - December

Flower Colours

Red / Pink,Yellow

Fruiting

December - February

Propagation Technique

Difficult. Should not be removed from the wild.

Threats

Seriously threatened in Northland due to the recent spread of the introduced bladder wort Utricularia gibba, and also by the continuing spread of oxygen weeds into these important lakes. In the South Island its habitats seem to be secure but extinction from many Northland lakes is expected. Indeed it has recently (November 2004) been confirmed as extinct in two far North lakes.

Chromosome No.

2n = c.24

Endemic Taxon

Yes

Endemic Genus

No

Endemic Family

No

Where To Buy

Not Commercially Available.

  

Attribution

Fact Sheet by P.J. de Lange (21 August 2006). Description based on Moore & Edgar (1970)

References and further reading

Moore, L.B.; Edgar, E. 1970: Flora of New Zealand. Vol. II, Wellington, Government Printer.

This page last updated on 7 May 2014