Molluscs` Role in NatureAnnelie Ehlvest
Tartu Environmental Education Centerwww.teec.ee
How many different molluscs live in Estonia?
On the land: about 80 species of snails
In freshwater: about 40 species of snails and 20 species of bivalves
In the Baltic around Estonia 8 species of bivalves and 20 species of snails
“Molluscdiversity” on land and in
freshwater in neighbourhood:
• In Finland: 128 species of snails and 30 species of bivalves
• In Latvia: 129 species of snails and 30 species of bivalves
• In Sweden: 437 species of snails (110 of these are landsnails and slugs) and 32 species of bivalves
How long do they live?
Big landsnails:
6 – 10 years
The freshwater pearlmussel : 150 years
River mussels Unio sp.: 40 – 90 years
Anadonta sp.: 30 years
Small landsnails and slugs: 1- 2 years
The blue mussel Mytilus edulis: 10
years
What do landsnails eat?
Different parts of flowering plants:
• leaves
• flowers
• fruits
• underground storage organs
What else do landsnails eat?
• mushrooms – both mycelium and fruiting body
• alga
• lichens
• ferns
• mosses
What else do landsnails eat?
• carrions: copse snail Arianta arbustorum can eat also dead snails
• the largest European land snail black keel back slug Limax cinereo-niger may attac otherones then in captivety
• no real carnivorous snails in our country
What else do landsnails eat?
• muldering plants, also dead wood (can decompose cellulose and partly ligneous)
• carton and paper (cellulose!)
What do watersnails eat?
• alga
• flowering plants
• dead plants and animals
• frog-spawn
What bivalves eat?
bivalves filter small organic parts from water:
• phytoplankton
• zooplankton
• detritus, floating organic material
• glochidial larval stages of uniocean mussels Unio sp. live for some weeks on host fishes gills and skin, eating their tissues
• freshwater pearlmussel
Margaritifera margaritifera does the same for several months
What else do bivalves eat?
Who eat landsnails?
Several beetles:
• carrion beetle Phosphuga atrata (1)
• carabids (2)
• fireflies, both larva and adults eat only snails (3)
1 2
3
♂ juv.
• true bugs, Heteroptera
• brown centipedes, Lithobius forficatus
• red bugs
• some fly larva develop in the snails eggs, also eating jung snails
Who else eat landsnails?
Who else eat landsnails?
Lot of birds:
• thrushes
• small songbirds
• hens and ducks
Who else eat landsnails?
• toads and other amphibians
• mole • hedgehog • shrew
• northern birch mouse• jellow-necked mouse
• rat
• squirrel
• stoat
• fox
• mink
• badger
• wild boar
Who else eat landsnails?
• mould on snaileggs
• green-banded broodsac- a parasitic flatworm (or "helminth") that uses landsnails as an intermediate host
Who else are interested of landsnails?
EGGS
Who eat molluscs in river, lake and pond?
• fishes: roach, crucian carp, tench, eel ec
• mammals: muskrat,otter, mink
Who eat molluscs in the Baltic Sea?
• fishes: sea-scorpion, flounder, god, turbot, viviparous blenny
• common starfish
• chinese mitten crab
Who else eat molluscs in the water?
• waterbirds: • eider• steller's eider• merganser• mallard• swan
Molluscs role on land?
• Food for many animals
• Consumers of plants and mushrooms
• Sorse of calcium for birds, especially in nesting time
• Decomposers of dead plants
• Intermediate hosts for parasitic flatworms
Molluscs role in fresh water?
• Food for many animals
• Consumers of plants
• Filtering plancton and detritus
• Parasites on fishes
• Intermediate hosts for parasitic flatworms
• Part of plancton in larva stage (zebra mussel)
• Empty shells are bildingmaterial for caddisflies (Limnephilus flavicornis)
Molluscs role in Baltic Sea?
• Food for many animals• Consumers of plants • Filtering plancton and detritus,
cleaning water• Empty shells are used by hermit crabs
as “homes”
Text: Anneli EhlvestPictures: Epp MargnaPhotos: Anneli Ehlvest, Tarmo Niitla
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