|
Continuing this story of aquarium molluscs
we come to the River Limpet, of which two
species are indigenous to this country. They
resemble the limpet of the seaside in the
habit of clinging to a support. This limpet
is found, as a rule, clinging to the stems of
water lilies. The shell is smooth, not ribbed
like the marine species, and is not symmetrical.
They are of little value to the aquarist, but
are mentioned here because they are interesting to watch in the aquarette.
A small whelk-like mollusc that is fairly
common in ditches, etc., all over the country
is Succinea. This has an oval, transparent
shell with a distinctive amber colouring ; it
does not actually live in the water, but disports
itself on the leaves of aquatic vegetation.
Succinea provides considerable interest in the
aquarium.
Most of the freshwater molluscs are dull
coloured, though many are delicate in design
and structure. An exception is the Zebra
Shell, which may be found in most English
rivers. They are small and globular and have
numerous purple bands or rows of spots by
which they can be easily distinguished. The
shells are thick and have a deep gloss ;
altogether an ideal member for the aquarette.
So much for the snail-like molluscs-only a
very few of the vast family are noted here ;
they may be obtained either by collecting from
likely ponds or from the better class dealers.
The Fresh Water Mussels, as has been
mentioned earlier, by siphoning the water,
assist in keeping the water clear. Very few
species are to be found in
English waters and of these
the best are the River Mussel
(Unio fluviatilis) and the
Swan Mussel (Anodonta
cygneus).
These molluscs do not feed as a snail feeds ;
they have two tubes or siphons, one of which
draws water into the stomach and, after
filtering it and so retaining any small organ-
isms that may be in the water, ejects it as
clear water with the exhalant siphon. Thus,
provided there are sufficient mussels to cope
with the prolific reproductive powers of the
minutiae, the water should be clear eventually.
As they are fairly large, up to six inches in
length, they should not be dropped into the
pond haphazard, they should be placed on
a rake, say, and lowered gently to the desired
spot. Moreover, they are very fond of perambulating along the bottom, their mode of
progression resembling that of a snow plough.
So, if a plant should be in the way, it will be
rooted up unless well established-although
the mussel has an uncanny way of avoiding
obstacles. The mussels, then, should not be
placed in the pond until the plants are well
rooted.
|
