River Clyde Fisheries Management Trust Ltd.
 

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The Biology Page.                            

This page is designed to help in the understanding of life and life forms in our river systems, it is not a succinct scientific page as such, but a beginners starting point.
The Ecology pages, are kept separate from the Biology section as a different path will be sought.

The freshwater habitats are divided into two groups; Rivers and Lochs.

Water has a tremendous fascination for most of us. We like to swim in it, walk by it or sail on it. There are many hobbies and pursuits which depend on it - fishing, sailing, canoeing, swimming and water skiing.
Each sport or hobby takes its sights further as they need to know more of  which gives them pleasure, e.g. The fisherman needs to know what insect lives within and around; the canoeist and yachtsman for the weeds and the rambler for the water birds and plants.

Water the life within. - There are many life forms in our water systems and they all go towards the life cycle of our planet; as we know life would not exist in the form it takes at present if water were not present.

  • We often perceive liquid water (H2O) to be ordinary as it is transparent, odourless, tasteless and ubiquitous.
    It is the simplest compound of the two most common reactive elements in the Universe, consisting of just two hydrogen atoms attached to an oxygen atom. Indeed, very few molecules are smaller or lighter. Water is the second most common molecule in the Universe behind hydrogen, H2. To end the subject on water,
    water's unique properties and chameleonic nature seem to fit ideally into the requirements for life as can no other molecule.

Some H2O life forms - Click drawings for further explanation. Video available.

Protozoa
video		 Flagellates (One of many.)
(those that photosynthesise are often classed as algae).
Rotifers
video		 Wheel-like, hairy appendages, transparent, free swimming or attached.  0.2 - 1 mm.  
Hydra
video		 Green, brown or colourless, body and tentacles contract and stretch can extend: 20 mm.
Arthropods
 video		 Jointed limbs; many groups e.g. crustaceans ('water fleas') mites. Picture of Cyclopsida.
Other:
Insect stages

E.g. caddisfly larvae, dragonfly nymphs, water beetles, etc.
Alderfly nymph One tail, long filaments along the abdomen.
Caddisfly larva
picture		 Most species build a cylindrical case for protection, other species make a distinct case from different materials.
Stonefly nymph
video		 Two jointed tails.
Mayfly nymph
video		 Three jointed tails, leaf-like (or other shaped) 'gills' on its sides. Picture of Baetis Nymph gills (mayfly).
Damselfly nymph
video		 Three leaf-like tail appendages (gills), extendable jaws.
Dragonfly nymph Robust, no tail appendages, 
extendable jaws.
Water bug
nymph/adult
video		 No jaws, like all water bugs they possess a tube-like beak, the nymphs don't have wings. 
Common forms: Backswimmer, Water boatman. Water surface: Pond skater.
Water-beetle larva Strong jaws, long segmented body, short legs.
Water beetle adult

Strong jaws, tough shield, many water beetles are fierce predators.

Drawings by kind permission of -
         Wim van Egmond		 For further information - Web Site:
www.microscopy-uk.org.uk

Animals of the lotic and lentic regions.

LOTIC   

Where it is rapid streams with stony beds (eroding substrata) most animals are bottom living, surprisingly this type of water most often produce the largest variety of bottom living organisms. Limpet, leeches, flatworms, black fly larva and a variety of mayfly nymphs and stoneflies. The freshwater shrimp lives in crevices in the stony river base to which they adjust to the streams current as do the other insecta of fast waters.

Depositing substrata:
                                Depositing substrata consists of sand or soft silt which is the least favourable for animal and only will support the smallest number of species. The surface will hold animals such as the water louse (Asellus), the alder fly larva (Sialis), various snails (Valvata & Bithynia) and in the silt the pea mussel. The substratas with lower oxygen content you will find e.g. Tubiflex & Chironomous).

LENTIC

A stony shore line is similar to the eroding substrata of running water, due to the wave action.
The species of animals found in lochs or lochans are not always the same. For example a species of mayfly with the genus Ecdyonurus can be found in both lotic and lentic waters the other two species are only found in rivers. Further out beyond the shore line (littoral area) is the offshore area (limnetic zone), this area is generally made up of fewer animal species but in much greater quantities.