Picture Guide To The Common Aquatic Bugs Of Saskatchewan

Transcription

1 Picture Guide To The Common Aquatic Bugs Of Saskatchewan Prepared by Dale Parker, AquaTax Consulting 2012 This is an basic introductory picture guide to some of the aquatic macroinvertebrate (or "bug ) groups that can be regularly found in Saskatchewan waters. Links are provided to more detailed information of many of the groups. Further Reading

2 Freshwater Sponges (Porifera) Image of megascleres ~200x In clean standing or slowly flowing water, sticks and rocks may appear to have yellowish green globs on them. Often these are algal colonies 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.

3 Hydra (Cnidaria: Hydrozoa) The body of a Hydra is usually less than 20 mm long when fully extended. But when contracted it can shrink to 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 bag-like "body" from which six or so tentacles emerge from around a dome shaped mouth region. Hydra can be found in all types of freshwater from roadside ditches 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.

4 Round Worms or Nematodes (Nematoda) In fresh samples nematodes can be seen as small white to clear threads with some brown colour 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. Some nematodes (mermithids) are internal parasites of larval aquatic insects, especially diptera, where they can be seen in the body. Closely related Horsehair worms (Nematomorpha) can be many cm long and normally dark brown.

5 Aquatic Worms (Oligochaeta) ~300x showing hairs and chaetae These worms are kin to the terrestrial earthworms. They are usually found in the bottom sediments of both running and standing waters. Many are bright red when alive. Most specimens are less than 2 cm long. Some species especially in the genus Tubifex can occur in large numbers in areas of high organic pollution such as sewage outflows and lagoons. Identification for most requires mounting on slides and examining the patterns, numbers and types of hairs and setae (chaetae).

6 Leeches (Hirudinea) Leeches are easily recognised by their worm-like bodies with numerous segments. Sizes can range from 10 mm to 100 mm or more. Although they are often all lumped together as blood-suckers there are only a few species that typically suck blood. Saskatchewan Leech Web Page

7 Snails and Limpets (Mollusca: Gastropoda) Limpet Snails have a coiled shell that has a spire or is a simple flat coil like a rope. The "common pond snails" have the opening to the right when the spire is up. "Tadpole snails" have the opening on the left. Some families have a circular piece of shell, the operculum, which they can close the opening of the shell with. Limpets have the shell in the shape of a low cone and are usually restricted to running waters. Saskatchewan Snails and Limpets Web Page

8 Clams (Mollusca: Pelecypoda ) Clams have two shells. Size ranges from a few mm across for the "pea clams" (Family Sphaeriidae) to over 15 cm for some of the larger types of "floaters" and "heal splitters (Family Unionidae). The pea clams can be found in all types of water including small ponds. The larger more familiar clams are found in permanent waters and especially in flowing waters. Saskatchewan Clam Web Page

9 Acari (Water Mites) Water mites are often seen clumsily swimming or crawling amongst the water vegetation and debris. They have eight legs as adults and many are bright red in colour. Most are tiny, the largest only reaching about 3 mm in diameter. They are parasitic on other aquatic insects during part of their life cycle and can be seen attached to the insect's bodies where they suck body fluids.

10 Fairy shrimp & Water fleas (Anostraca & Cladocera: Crustacea) Fairy shrimp are usually associated with temporary ponds where they can become numerous in midspring. Most species are less than 2 cm long. In the picture the female, with egg sacs visible near the centre of the body, is at the top. The male is at the bottom with claspers visible on the head. Water fleas can be so abundant in ponds 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.

11 Seed shrimps & Clam shrimps (Ostracoda & Conchostraca: Crustacea) Seed shrimp Clam shrimp Seed and clam shrimps are common in shallow ponds and sheltered areas of lakes. Seed shrimps resemble swimming seeds a couple of mm long. While clam shrimps look like tiny swimming clams at most 1.5 cm across. On closer inspection both reveal their bodies are encased in a two part shell.

12 Tadpole shrimp (Nonostraca: Crustacea) Tadpole shrimp 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. Opossum Shrimp (Mysidacea: Crustacea) Opossum Shrimp are found in some cold, deep lakes of northern Saskatchewan. Only one species has been recorded in the province, Mysis relicta (Loven).

13 Scuds (Amphipoda: Crustacea) Hyallela azteca Gammarus lacustris Scuds 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.

14 Crayfish (Decapoda: Crustacea) Crayfish appear like small lobsters. 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.

15 Springtails (Collembola: Insecta) Snow fleas Springtails are tiny insects no more than a mm or two long). Most have a forked abdominal appendage which acts as a spring. This group is found in wet soils and on the water surface of all types of aquatic habitats except fast flowing waters. They prefer calmer conditions so they do not get trapped in the surface film. They can be seen hopping like fleas on the water. Often on warm spring days the more terrestrial forms can be seen on the snow surface. Hence their other common name "snow fleas".

16 Mayflies (Ephemeroptera: Insecta) The immature stages (larvae) of mayflies all have gills along the body (abdomen). They also have one or two filaments at the end of the abdomen. The body form can be very flattened in some groups, especially in fast flowing water, to streamlined, almost minnow-like, in other groups. Still other larvae have their bodies adapted for burrowing into the mud substrates of lakes and rivers. Adults have two large forewings and two tails. If the wings of the adult are cloudy it usually indicates the specimen is a subadult. Saskatchewan Mayfly Web Page

17 Dragonflies and Damselflies (Odonata: Insecta) Adult dragonflies and damselflies are familiar sights from late spring to late fall in Saskatchewan The adults have four wings and an elongated abdomen. The wings can be held outwards from the body or along the body depending on the group. Larvae have hinged mouthparts. The damselflies have three leaf like "gills" at the end of the body. Saskatchewan Dragonfly and Damselfly Web Page

18 Stoneflies (Plecoptera: Insecta) Stonefly larvae have some what flattened bodies, two segmented caudal tails and, in many, tufts of gills at the base of each leg and sometimes on the first two or three abdominal segments. Size can range from 5 mm to over 5 cm. The adults hold their two pairs of wings flat over their body and the caudal filaments are very much reduced. Stoneflies are usually associated with cold, clean flowing water although some can survive along rocky, wave washed shores of cold lakes. Saskatchewan Stonefly Web Page

19 Aquatic Bugs (Hemiptera: Insecta) It is relatively easy to identify the major families, and some species, of aquatic true bugs found in Saskatchewan. True bugs have in common a leathery fore wing and mouthparts shaped into a sucking beak. Water striders are common in quiet areas of rivers, lakes and ponds where they can be seen walking on the water surface. Water boatman are common in most water types. They range in size from 3 mm to about one cm. Backswimmers are usually not as common but by no means rare. They are about one cm long and have a distinctive keeled back and swim upside down. The single species of giant water bug found in Saskatchewan can be 8 cm long making it our largest aquatic insect. Saskatchewan Aquatic Bug Web Page

20 Dobsonflies (Megaloptera: Insecta) Dobsonflies or alderflies are 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. Saskatchewan Dobsonfly Web Page

21 Spongilla-flies (Neuroptera: Insecta) Spongilla-flies (Neuroptera) are most often found 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. Saskatchewan Spongilla-fly Web Page

22 Aquatic Moths (Lepidoptera: Insecta) Aquatic moths 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. Saskatchewan Aquatic Moth Web Page

23 Caddisflies (Trichoptera: Insecta) Adult caddisflies look like moths but lack the coiled mouthparts that moths and butterflies have. The adult wings are covered by hairs. The wings are held tightly over the abdomen when the insect is at rest. The larvae have a well-developed head, three pairs of legs and a soft segmented body. Many caddisfly groups build cases, "houses", out of sand grains or pieces of plant material that they drag around with them. Other larvae construct stationary houses. Saskatchewan Caddisfly Web Page

24 Aquatic Beetles (Coleoptera: Insecta) Beetles come in variety of shapes as larvae but as adults all have the forewings hardened into coverings called elytra. Saskatchewan Aquatic Beetle Web Page

25 Wasps (Hymenoptera: Insecta) Aquatic wasps 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. Saskatchewan Aquatic Wasp Web Page

26 Two-winged Flies (Diptera: Insecta) True flies as adults all have only one pair of wings. The back wings are modified into balancing structures called "halteres". All the biting flies such as mosquitoes, blackflies, horseflies, deerflies and no-see-ums belong to this group. The larvae have no true jointed legs and are tube-shaped with many different body types based on this design. Saskatchewan Aquatic Two-winged Fly Web Page

27 Further Reading: Clifford, H.F Aquatic Invertebrates of Alberta. University of Alberta Press. Edmonton, Alberta. Merritt R.W., K.W. Cummins and M.B. Berg. Ed An Introduction to the Aquatic Insects of North America. 4th Edition. Kendall/Hunt Publishing Co. Dubuque, Iowa Pennak, R.W Freshwater Invertebrates of the United States: Porifera to Crustacea, 4th Edition Wiley-Interscience, New York, Thorp, J.H. and A.P. Covich. Ed Ecology and Classification of North American Freshwater Invertebrates.