Aquatic
Macroinvertebrates
What are Aquatic
Macroinvertebrates?

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Macroinvertebrates are small organisms
that do not have a backbone.
A great diversity of types.
 Insects
 Spiders
 Leeches
 Snails and clams
 Worms
What are Aquatic
Macroinvertebrates?
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
Aquatic macroinvertebrates are those that
live in water.
The majority of aquatic macroinvertebrates
are insects
 Insects can have three different life
stages: larvae, pupae, and adult
 Which stage is aquatic depends on the
type of insect
Insect Lifecycles - Incomplete
Metamorphosis
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Some insects do
not have a pupae
They molt from a
larval form to the
adult
Insect Lifecycles - Complete
Metamorphosis
What are Aquatic
Macroinvertebrates?


For most insects it is the larval form that is
aquatic
Common insect orders that have aquatic
larvae but terrestrial adults include
 Odonata – dragon flies and damselflies
 Ephemeroptera – Mayflies
 Plecoptera – Stoneflies
 Trichoptera – Caddisflies
 Diptera – Flies and Mosquitos
What are Aquatic
Macroinvertebrates?


Beetles, Order Coleoptera, have both
aquatic larvae and adults
 Interestingly, the pupae are often
terrestrial
Many of the true bugs, Order Hemiptera,
spend their entire life cycle in the water
What are Aquatic
Macroinvertebrates?

While insects are the most common
aquatic macroinvertebrates, there is a
wide variety of non insect forms
 Includes members of the Mollusc,
Annelid, and Arthropod Phyla to name a
few
Types of Aquatic
Macroinvertebrates
I. MOLLUSCS (SNAILS AND
CLAMS)
I. Molluscs
A. The Phylum Mollusca is the second
largest animal phylum in terms of number
of species
 While most species are marine (saltwater),
two groups are common in North Dakota
 Clams or mussels (bivalves) – not
usually found in wetlands
 Snails (gastropods)
I. Molluscs
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B. Gastropods –
the snails
Several different
kinds
Common snails in
wetlands include
the genus Physa
II. ANNELIDS (WORMS AND
LEECHES)
II. Annelida
A. Class Hirudinea – The Leeches
 Several different types
 Usually considered indicators of poorer
water quality
 Probably some exceptions to this
 Characterized by suckers on both the
anterior and posterior end
 Also called blood suckers
II. Annelida

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Many are ectoparasites that feed on a
blood meal
 They attach to their host, inject an
anticoagulant and an anesthetic
 This allows them to feed on a blood
meal usually undetected
There are some species that are
vegetarians and some that are scavengers
II. Annelida
B. Class Oligochaeta
 Aquatic worms - small segmented worms
that live in the bottom sediments of rivers,
streams, lakes, and marshes
 Actually quite a few different kinds
 Often overlooked because of their small
size
 Tubifex worms are often used for fish
food
Oligochaetes
III. The Arthropods
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Include the insects, crsutaceans, and
others
Largest group of aquatic
macroinvertebrates
Aquatic Insects
Aquatic insects
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There is a great diversity of insect species
that are aquatic
Many have an aquatic larval stage, but the
adult has wings and lives in the habitat
near water
A few groups have an entire life cycle in
the water
Aquatic insects
A. Order Ephemeroptera - Mayflies

Larvae are aquatic

Spend the majority of their life as larvae

Adults are short lived – 24 – 48 hours

Where the term Ephemeroptera comes
from - ephemeral
Aquatic insects

Many different roles and adaptations


Some cling to rocks, others burrow, and
some swim
Usually considered indicators of good
water quality
Burrowing
mayflies
Hexagenia limbata
 Usually found in
the bottoms
sediments

The small squaregills
Aquatic insects
B. Order Trichoptera - Caddisflies
 Larval and pupal forms are aquatic
 Considered to be indicators of good to
moderate water quality
 In many of the species the larvae form
elaborate cases that they live in
Aquatic insects

Larvae can often be identified by the
following features
 Usually live in a case
 Have two “legs” on the back of their
abdomen
 These have hooks that the animal uses
to anchor itself
Longhorned Case makerCeraclea sp.
Northern Case maker larvae
with case
Aquatic insects
C. Diptera – Flies and Mosquitoes
 Larval and pupal stages are aquatic
 Wide variety – some indicators of good
water quality, others indicate poor water
quality
 Larvae do not have legs – most are
wormlike with very strange features
Crane Fly Larvae
Mosquito – Aedes sp.
Aquatic insects
D. Order Hemiptera – True bugs
 Spend their entire life cycle in the water –
although many can fly and migrate
 Mouthparts consist of a tube used for
sucking
 Many are predators
Mesoveliidae
Gerridae
Hebridae
Giant water bugs
Water Boatman
Aquatic insects
E. Order Odonata – Dragonflies and
Damselflies
 Larval forms (called nymphs or naiads) are
aquatic
 Both larvae and adults are predators
III. Aquatic insects
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Both damselfly and dragonfly larvae have
a prehensile jaw that they can use to
spear prey
Damselfly larvae are usually thinner, have
three caudal gills
Dragonfly larvae have a stouter body,
caudal appendages are much reduced
Dragonfly Larvae
Jaws of Dragon fly larvae
Odonata Adults
Dragonfly adult
Damselfly adult
Aquatic insects
F. Order Coleoptera – Aquatic Beetles
 Beetles are the most diverse group of
animals on earth
 Many forms are aquatic
 One of the few groups where both larvae
and adults are aquatic
 While some are considered to have little
value in water quality determination,
others are useful
Chrysomelidae
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Most members of
this group are
terrestrial
Do not have many
obvious
adaptations for
aquatic life
Found mainly on
aquatic vegetation
Haliplidae – Crawling water
beetles
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Small aquatic
beetles
Crawl around on
submerged
vegetation and
debris
Top picture – adult
Bottom picture larvae
Gyrinidae – Whirlygig beetles
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Often found
buzzing around on
waters surface
Unique in that they
have two sets of
eyes
Dytiscidae – Predaceous
diving beetles
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Many different types found in wetlands
Both adults and larvae are aquatic
Both adults and larvae are predators
Dytiscidae – Predaceous diving
beetles – Example adult
Dytiscidae – Predaceous diving
beetles – Example larvae
IV. OTHER ARTHROPODS
IV. Other Arthropods
A. Order Amphipoda – Scuds (see picture
on previous slide)
 Can be very common in some areas
 One type, the genus Gammarus, is found
primarily in lakes and marshes
 Larger of the two types found in ND
 An important forage food for fish in
Devils Lake
IV. Other Arthropods
B. Order Decapoda – the Crayfish
 Common inhabitants of rivers, streams,
and lakes
 Only a couple of species in North Dakota
 Crayfish usually feed at night and are
primarily scavengers
 Fairly short lived with a life span usually of
2 years or less
Crayfish
IV. Other Arthropods
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C. Class Branchiopoda – the water fleas,
clam shrimp, fairly shrimp, and others
Water fleas are commonly known as
Daphnia
Usually found in lentic waters
Their body is covered by a carapace
They can be an important part of the food
chain in aquatic ecosystems
Daphnia
Fairy Shrimp
Clam Shrimp