Pond-Dipping
At the top of the meadow, by the wooden walkway, there are three small ponds that are used by visiting schools for pond-dipping. There are also pond-dipping events for families during the year - keep an eye on our events pages for details.
The life found in the dipping ponds will to some extent reflect that found in the main mill pond and the streams feeding the mill pond, but the range of habitats in the mill pond and streams is much greater than in the small dipping ponds. However, the dipping ponds offer a sheltered haven for many creatures and plants that would find the deeper waters of the mill pond with its larger fish and birds much less safe. The streams that feed the mill pond are usually fairly slow-flowing, but even so will offer a different environment to the largely stationary waters of the mill pond and dipping ponds. Flooding of the marsh land around the board walks offers another interesting environment and there are many small freshwater creatures that make this their home over the wet months of winter. These type of differences may lead you to think about how the different zones around the mill pond support different plants and animals, and zonation of freshwater habitats is indeed very important: conditions for life vary between the shores of the pond, the banks, marshes and reed beds and shallow water around the edges and then the deeper water towards the centre of the pond. Each zone has its particular inhabitants and they all contribute to the complex life of the Reserve. Everything in the Reserve affects everything else, from human visitors down to microbial life.
This page will try to give a flavour of the types of life found, mainly in the dipping ponds, but also in some of these other environments. Many of these creatures are largely hidden from visitors. It isn't always easy to see deep into a pond. Let's start by looking at some of the larger creatures, and then go a bit smaller, and smaller. Let's also think about who eats what and whom...
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Who hasn't been fascinated by tadpoles? The frog's life cycle of frog, spawn, tadpole and back to frog is well known and is always a source of wonder. Frogs are also a good source of food for a number of birds and in turn are themselves partial to insects, slugs and other small creatures. Their life cycle is similar to other amphibians, such as toads and newts... |
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| ...and here is a partially developed newt found in
the dipping ponds, July 2003. The type of changes seen here, with newly
growing legs typical of land animals but gills typical of fish is characteristic
of the metamorphosis common to amphibians. |
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...and here are some fully grown newts, pictured in the pond near the Reserve entrance | |
| Many other creatures undergo metamorphosis. On the insect pages you will see dragonflies and water dwelling nymphs, but in fact most insects show these types of life cycle. Here is a mosquito larva, it is about 8.5 mm long:
You often find these in water butts and bird baths. The tube attached to the tail is a sort of snorkel, used for breathing air at the water surface. |
Mayfly nymphs, on the other hand, have gills rather like the newt tadpole. These are the feathery things along the side of its body (not the "Prince of Wales" tail!):
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| Some adult insects also spend much of their life in the water and have similar means of breathing. Here is a water scorpion (Nepa cinerea) with a snorkel tail:
It uses those vicious front legs to catch its prey and is about 2 cm long snorkel tip to front of head.
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... and a Dystiscid water beetle that has taken the snorkel idea one step further by carrying a bubble of air with it tucked under its tail. This one is at the water surface to refresh its air supply:
These beetles are fierce predators and will attack almost anything, even if it is bigger than itself, including fish, other insects, freshwater shrimps etc. The Dytiscid beetles include the Great Diving Beetle (Dytiscus marginalis), which is very similar in appearance to the beetle shown, but whereas this was only about 8 mm long, the Great Diving Beetle can be up to 3 cm or more long. They are also very competent flyers - a sort of flying submarine!
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| Another fierce creature is the Backswimmer, Notonecta glauca, which also carries its air with it in the same way as our water beetle. The immature forms are green and are very common early in the year, but the adults are brown. Beware in handling these beasts - they bite! The similar but smaller Water Boatman (Corixidae) is also often found at Warnham, but this swims "right way up". |
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Of course, not all predators are found in the water. The Pond Skater, Gerris lacustris, skims around on the surface of the water and preys upon other insects that fall in. Their struggles are soon sensed by the Pond Skater, which is classified as a bug, and has specially adapted mouthparts to suck the body fluids from its victim.
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Everywhere needs its scavengers, and ponds are no different. The water louse, Asellus, is just such a creature, they look a little similar to their dry land cousins, the wood lice, and are very common in ponds and streams. They can be confused with the sideways swimming freshwater shrimp, Gammarus pulex, but are not free swimming, preferring to scuttle around mud and weed on their many feet. They are crustaceans, not insects, although of similar size to many insects. | |
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Worms, like this annelid worm, are always very common in the bottom sediment of ponds and are also great scavengers amongst the mud
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Here are a selection of molluscs:
Limpets are filter feeders and like still water. Another filter feeder commonly found is the pea shell cockle which is much like the familiar marine cockle, but only about 5 mm across.
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| If we move down in size a little to creatures
that really need the services of a microscope to be seen properly, we
come to the favourite food of many a larger creature, another crustacean,
the water flea (Family Cladocera). There are actually several types, but
best known is probably Daphnia, although there are a number of
other families commonly found in the dipping ponds at Warnham. The smallest
is Chydorus sphaericus at about 0.35 mm, a mere speck to the eye,
and the largest Eurycercus lamellatus at over a millimetre across.
Strange that these two belong to the same family, Chydoridae. There
are times when the dipping ponds are so thick with these creatures that
they resemble a form of soup. Daphnia often takes on a pink colour
and water samples viewed from a distance can have quite a distinct pinkness
as a result. The round objects that can be seen in the Daphnia
and Simocephalus photos inside the backs of the creatures are in
fact eggs in their brood pouches, and these will hatch inside the creature
which will then give birth to live young. Nearly always, the individuals
you see will be female, and in some species the male is not known, the
eggs being produced parthenogenically (without a male). The water fleas
pictured are all vegetarians and it is amazing how much salad they can
eat! |
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| The one eyed cyclops is another common
creature belonging to the Copepoda family. At Warnham we also see, if
we look very hard or use a microscope, its relations Diaptomus
(common in the spring) and Canthocampus. A young copepod is
called a nauplius. Again this gives an example of metamorphosis,
and you can see that the nauplius is rather different to the adult..
These creatures are very fast movers and often move with a characteristic
jerky motion. |
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This little fellow is an ostracod, another crustacean. They are bean-shaped bivalves that live on decaying plant matter. Very useful for eating autumn leaves that fall into the ponds. They are very common in standing water under and around the board walks and can be seen as small specks scuttling or swimming around in shallow water, especially if there are fallen leaves or other dead plant material.
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These creatures have long sting-loaded tentacles and prey upon water fleas, copepods etc. They are classed as Coelenterates. The green of the Green Hydra is due to algae which actually live inside the hydra in a relationship known as symbiosis. i.e. they cannot live without each other. |
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Moving to even smaller creatures, we should not ignore the rotifers. These were first observed by the Dutchman, Antony van Leeuwenhoek around 1670. Commonly, rotifers possess two trochal discs of cilia on their heads. The beating of these cilia looks to the eye like two rotating wheels, hence rotifera means "wheel bearers". On the right is a rotifer named Philodina roseola. It is commonly found in puddles and bird baths and often has a distinct pink colouration. It is one of a group of rotifers known as bdelloid rotifers, from the latin for leech, because of the way they move with a looping leech-like motion. They feed tethered by their tail, or foot, and draw food in by currents created by the cilia on their trochal discs. They can also use these cilia for propulsion when swimming. Although very small, they are complex creatures with a gut and jaws (mastax). There is no male of this species and reproduction is parthenogenic (i.e. without a male). |
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Here is another, free swimming rotifer, Testudinella patina, named after its resemblance to a tortoise. This resemblance is most pronounced when you can see the tail, or foot, which is out of focus in this image. It is a common rotifer in ponds and swims using the cilia on its trochal discs. Unlike P. roseola, its body is rigid and is a flatish discoid.
There are many other species of rotifer and they are common in ponds. The scale bars on these two rotifer images correspond to 0.05 mm. |
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