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