Riella helicophylla (Mont.) Hook. (BRYOPHYTA; MARCHANTIOPSID

Post by **MWP admin** » Sun Dec 31, 2006 8:58 pm

Title:
Riella helicophylla (Mont.) Hook. (BRYOPHYTA; MARCHANTIOPSIDA;
RIELLACEAE ); a new addition to the macrophytic wetland flora of the Maltese Islands

Authors:
Sandro Lanfranco, Edwin Lanfranco

Abstract:
The freshwater liverwort Riella helicophylla (Mont.) Hook. is recorded for the first time from the Maltese Islands.
A number of individuals belonging to this species were cultured upon hydration of desiccated sediment collected
from Ghadira s-Safra, a saline marshland fringing the north-eastern coast of Malta. Subsequent fieldwork has not
revealed any field occurrences of the species in the Maltese Islands. This indicates that this record may be due to a
chance occurrence of viable spores in the sediment, possibly as a consequence of transport by migrating waterfowl.
The apparent absence of the species in the wild may nevertheless also be due to habitat degradation and to a suboptimal
physico-chemical environment. An intensive sampling programme, aimed at clarifying the status of this
species in the Maltese Islands, is in progress.

valerandi · Post by **valerandi** » Sun Dec 26, 2010 11:03 am

One of the rarest plants in Malta:

Riella helicophylla

IL-PINE · Post by **IL-PINE** » Sun Dec 26, 2010 4:59 pm

viva l-papri

Post by **MWP admin** » Mon Dec 27, 2010 8:01 am

Congratulations Val! Is it the same location as in the paper above or a new population? How large the specimens are - few cm or few mm !

Thanks for the info, very interesting.

valerandi · Post by **valerandi** » Mon Dec 27, 2010 5:49 pm

1 to 2 cm. Cultivated from spores from the same location. The adult gametophyte is not evident in the pool but the spores are present so there must either be a resident spore count or else the plant is reproducing in a way which is not easily evident.

Riella have been known to spend decades as spores before germinating in the right conditions. The spore count in the dry sediments is high enough to preclude the hypothesis of a single transfer by wild fowl.

The picture is not clear since the water they grow in is turbid.

Post by **MWP admin** » Mon Dec 27, 2010 7:28 pm

Very interesting, didn't realise that it does not form sporophytes in the wild, but there should be sporophytes in he pond due to the abundant spore bank in the sediment. Did you ever try to cultivate the spores at different salinity? Did you think of any aquatic 'predator'?

Keep posting val!

valerandi · Post by **valerandi** » Tue Dec 28, 2010 12:50 pm

I can't say for sure that the plant is not producing gametophytes and sprorophytes in the pool in nature. The water is frequently too murky to see the bottom at even a few cm. However given the length of time that the plant requires to develop in vitro, it highly unlikely that the full cycle is taking place in nature. The water retention at Ghadira is-safra is today measured in days not weeks. The water input has somehow been affected by the road. The pool used to host Triops but these have not been seen there for many years. If that is the case, the plant is not reproducing and the the sporebank in the pool's debris is the last refuge of the plant. I do not think that predation has anything to do with it. The only thing that would have eaten the Riella would have been the Triops but it is not there any more.

I have grown it in fresh water. Not sure if salinity is important. It is a weak grower and competitor (next to other freshwater rock pool plants), so the salinity changes may just be important for reducing competition unable to cope with the changes.

The spores appear to need a period of drought to become viable like Elatine's seeds. Still have to study it further.