SK Aquatic "Bug" Guide
A picture guide to Saskatchewan aquatic "bugs"
This is an introductory picture guide to the Saskatchewan aquatic "bug" groups.
A downloadable version of the SK Aquatic Bug Guide is available here (SK Aquatic Bug Guide pdf (2.9 meg))
Many of the major groups of "bugs" can easily be identified with the naked eye. Even some species can be identified because they are so distinctive. Unfortunately other groups, such as the non-biting midges or bloodworms (Chironomidae: Diptera), are extremely difficult and require special techniques and a good microscope to identify them below the family level.
Most formal identifications of bugs, and other animals and plants, involve the use of dichotomous keys where choices are made between two character states, such as legs are black, or, legs are white. However, these are often long and drawn out documents that are hard to follow even for experienced users. A simpler way to identify the basic groups is to use a "Peterson's Guide" approach which uses pictures to aid the identification process.
For this bug guide once the bug is identified the reader can click on the navigation links on the left to go to a more detailed account of the group.
Freshwater Sponges (Porifera) |
In clean standing or slowly flowing water, sticks and rocks may appear to have yellowish green globs on them. Often these are algae but sometimes they are sponges. Close examination will reveal some holes in the surface and possibly a spongilla fly larva. Under magnifications of 200 times or more the various supporting structures (megascleres) can be seen.
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Hydra (Cnidaria, Hydrozoa) |
The body of a Hydra is usually less than 20 mm long when fully extended. But when contracted it can shrink just a few mm. Most are coloured a somewhat translucent white to reddish brown although some are green due algal cells in the body wall. For these reasons they are easily overlooked in their natural habitat unless the debris is examined carefully. They can sometimes be seen hanging from the water film. Hydra consist of an elongated baglike "body" from which about six or so tentacles emerge from around a dome shaped mouth region. Hydra can be found in all types of freshwater from roadside ditchs and sloughs to sheltered microhabitats in relatively fast flowing streams. They feed on small insect larvae and crustaceans which they capture using their long tentacles that are covered with cells (nematocysts) which eject threads to entangle the prey and others that sting the prey into submission. The tentacles then pull the prey to the mouth where it is engulfed. Often there will be "buds" of smaller hydra growing out of the body. This is a form of asexual reproduction.
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Nematodes |
In fresh samples they can be seen as small white to clear threads about 1 cm long moving in their typical thrashing pattern. They can be found anywhere in aquatic systems but are especially abundant in soft sediments with high organic content in both running and standing waters.
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Aquatic Worms (Oligochaeta) |
Leeches (Hirudinea) |
Snails, Limpets and Clams (Mollusca: Gastropoda & Pelecypoda) |
Limpets (Gastropoda) have the shell in the shape of a low cone.
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Acari (Water Mites) |
Crayfish, Scuds, Tadpole Shrimps, etc (Crustacea) |
Crayfish (Decapoda) are lobster-like. They can often be seen scuttling between the rocks of slow moving streams and rivers or in the shallows of lakes. Only one species, Orconectes virilis (Hagen) occurs naturally in SK. Other species may have been introduced as pets that have subsequently escaped. Whether these escapees have established breeding populations and, if so, their impact is not known.
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Scuds (Amphipoda) are found in all types of permanent standing and slow flowing water. They are slightly flattened laterally. Some may reach over a cm long. Three species have be reported from SK. Gammarus lacustris Sars, has no spines along the back and a tiny "flagellum" on the first antennae. They are usually larger than Hyallela azteca (Saussure), which has spines on its back and no "flagellum". Diporeia hoyi (= Ponoporeia affinis) (Bousfield) is found only in deep, cold lakes. In this species the first antennal segment is longer than the second. Males have extremely long antennae compared to the females.
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Tadpole shrimp (Notostraca) are relatively uncommon in Saskatchewan. They inhabit temporary ponds. They can reach 2 to 3 cm long in some habitats. Three species belonging to two genera occur in SK Triops longicaudatus LeConte, Lepidurus lynchi Linder and L. couesii Packard.
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Opossum Shrimp (Mysidacea) are found in some cold, deep lakes of northern Saskatchewan. Only one species has been recorded in the province, Mysis relicta (Loven).
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Fairy shrimp (Anostraca) are usually associated with temporary ponds where they can become numerous in mid-spring. They are usually less than 2 cm long. In the picture the female is at the top. You can see the egg sacs. The male is at the bottom with claspers.
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Seed shrimps (Ostracoda) are common in ponds and lakes. They resemble swimming seeds a couple of mm long. Closer inspection will reveal a clam-like shell.
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Clam shrimp (Conchostraca) can be common in shallow ponds and lakes. They first appear to be like small swimming clams. Length is about 1.5 cm or less.
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Waterfleas (Cladocera) can become so abundant in ponds and shallow water that they form reddish clouds in the water. They swim with a jerky motion using their antennae. They rarely get larger than a couple of mm.
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Insects |
Aquatic Moths (Lepidoptera) look like other moths in the adult stage. As larvae they live in water usually associated with plants. Some create small "houses" out of plant material. And some have bodies covered in gills.
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Spongilla flies (Neuroptera) are associated with freshwater sponges, which the larvae feed on. The larvae are only a couple of mm long at most and have needle like mouthparts to suck the contents out of sponge cells. The adults have four wings and are also small.
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Alderflies (Megaloptera) usually are not very common. The larvae look like some beetle larvae with gills along the sides of the body and a terminal filament at the end of the body. The adults are dark and have very thick wing veins on their four wings.
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Wasps (Hymenoptera) are parasitic on other aquatic insects. They are usually only seen as adults. Since most look like tiny terrestrial wasps they have to be collected in traps in the water to ensure they are aquatic.
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