Hello Nature Lovers!

After a long, weird Winter, Spring is finally here! 

It’s beautiful outside! The birds are chirping, flowers are blooming. 

On days like this, most college students like us are focusing on the return to life on land. So the best way to avoid being a mainstream nature lover … is to jump INTO THE STREAM!!! ;D

Here is a guide to what to expect in streams and lakes around this time of year!

Hydra

Hydra are a group of tiny freshwater cnidarians–distant cousins of jellyfish, coral and sea anemones. These critters sport long, trailing tentacles to catch micro crustaceans, in lieu of the fishes of their larger relatives(Reid, 2001). One species, Craspedacusta sowerbii, actually produces a penny-sized medusa form, and is known as the peach blossom jellyfish(McKerch)! The typical mode of transportation for these guys is to cartwheel across their environment on their tentacles and hold fast!

Bryozoa

Bryozoa are weird! This phylum of animals construct colonies of individuals, each playing a different role in the superorganism. Filter feeders, each individual organism feeds by channeling water to its mouth by beating a horse-shoe shaped ring of tentacles called a lophophore. Usually found in still waters, bryozoa resemble moss or algae, but are not plants. The colony will produce a capsule known as a statoblast which will germinate and start a new colony(Reid, 2001). Fredericalla, one of the major groups of bryozoa to be found in our rivers and lakes, have a branching appearance, like tiny twigs. Pectinatella, on the other hand, look like semi-transparent half-deflated basketballs. And the members of the genus, Plumatella, coat sticks, looking like a tight mass of fibers wrapped around a sunken piece of wood(accessed 2024).

Fish

Oles will find fish of all sizes in our natural lands. Flat head minnows, native to Canada and the Rockies, have been introduced to other regions. They have a light belly, a dark stripe down their side, and are about 3 inches long. Redfin shiners are native, specifically to the Mississippi River and Great Lakes region. They mostly eat vegetation and small insects, and live in gravel and substrates. A few larger fish, like the white sucker, may also be observed in rivers. These fish can grow to about a foot and a half long, and have long, silvery bodies. Northern redbelly dace reach a maximum length of 12 inches, and are identifiable by a dark green back, a bright yellow belly, two horizontal black lines and one horizontal red line. Sunfish are also super common, with their flat, oval, green bodies. Blue gills, coming in at 8 to 12 inches, are somewhat bigger, and can weigh up to a pound! You might find largemouth bass, pumpkinseed, Johnny darter, channel catfish and other beautiful fish dancing in the sparkle and foam! And while no one I talked to has seen any in our natural lands, you could also keep an eye out for a parasitic, foot-long, living fossil; the silver lamprey.

Insects

Insects occupy every freshwater niche imaginable! One of the most recognizable representations of such creatures is the dragonfly larva. Sometimes called the devil’s darning needle, these critters are voracious predators, feeding on tadpoles and fish, and propelling themselves through the water by shooting water out their anuses(Mill and Pickard, 1975)! Many caddisfly larvae build portable cases made of a wide range of materials–including snail shells–which they bind together with silk. Other species build fixed retreats where they lay in weight for food. And some species build nets in running water to catch prey! The well known water treader skates across the water on surface tension. Water boatmen flap through the water with their hind legs, and carry a pocket of water under their carapaces(Reid, 2001). In contrast to these tiny, detritivorous bugs, the terrifying giant water bug can grow up to 3 inches long and hunts vertebrates(Reid, 2001)! Not to be outdone is the menacing water scorpion. With long limbs, dark brown in color and a pair of creepy claws reminiscent of those of its namesake, these predators breathe through a snorkel on their abdomens and snatch prey with their long forelimbs(H.)!

Snails

Snails–shell-baring members of the class Gastropoda in the phylum Mollusca–reside in all aquatic ecosystems, eating algae and detritus. They sometimes hitch a ride on aquarium plants where they cause trouble for fish keepers, as they breed fast!

Water Fleas

Water Fleas are tiny crustaceans which inhabit mostly slow moving waters in lakes and streams. Some of them adapt to the presence of predatory fish by growing protective spines(Cole)! Other species are transparent, and it is so cool to get to watch their hearts beating and guts churning food under a microscope!

Copepods

Another prolific group of tiny aquatic arthropods are the copepods. Found in salty and fresh water, these tiny crustaceans sport a pair of conspicuous antennae, and between three and five segments with one pair of limbs each(Barns, 1982). Females are often identifiable by the huge masses of eggs which hang from their bodies. Most copepods have only one bright red eye, similar in structure to an insect’s, and these animals are the inspiration for the character Plankton in Spongebob Squarepants(Wilson)! 

Tadpoles

Tadpoles are the larval stage of amphibians. The most familiar group to Minnesotans are toads and frogs, but Minnesota also is home to a number of salamander species! Tadpoles tend to be herbivorous if they will grow into frogs, while the tadpoles of salamanders are carnivores. The tiger salamander, which is common in our part of the state, has a set of gill fronds. The ubiquitous American toad breeds in Spring and early Summer, and produces dark brownish tadpoles. Another familiar species, the Spring peeper, lays its eggs during warm spells in Spring, and has brownish, mottled tadpoles. Northern leopard frogs breed in March through June, and produce tadpoles that are a dark, sandy brown with black spots, and Bullfrog tadpoles are greenish with dark speckles, are bred in May through July, and take two years to mature(Reid, 2001)!

Crayfish

A more conspicuous crustacean is, of course, the crayfish. Crayfish are similar to lobsters in appearance, but have much shorter lifespans and a more herbivorous diet(accessed 2024).

Sponges 

That’s right! Freshwater sponges! These simple animals sometimes are a bright green from symbiotic algae within them, and can cover inches to meters of stream and lakebed(Reid, 2001)! Sponges are so simple that their cells can undifferentiate and change between functions; so a cell that is specialized for feeding might one day repurpose itself for structural crystal production(accessed 2024)! 

Bivalves 

These simple molluscs include such recognizable (and delicious) creatures as clams and mussels. Clams typically stay clear of deeper waters. Freshwater mussels have a fascinating way of reproducing. They grow a lure which looks like a small fish. This tricks larger predatory fish into biting on it. This in turn triggers the release of larvae–called glochidia–which will cling to the fish’s gills and thus be distributed to new places(Hartfield and Hartfield, 1996). All this in spite of the fact that the mussels are blind!

Scuds

These common crustaceans look like tiny shrimp, and can be found in every freshwater niche. They are found in every aquatic ecosystem, and form the base of many freshwater food chains(L.)!

Sources:

Reid, George K. Pond Life. (St. Martin’s Press, 2001)

McKercher, E., O; et al. Craspedacusta sowerbii Lankaster 1880. USGS freshwater jellyfish (Craspedacusta sowerbii) – Species Profile (usgs.gov) Access Date: 4/29/2024

Phylactolaemata (Freshwater Bryozoans). What-When-How Class Phylactolaemata (what-when-how.com) Access Date: 4/29/2024

Mill, P. J. & Pickard, R. S. Jet-propulsion in anisopteran dragonfly larvae Comparative Physiology 97, 329-338 (1975).

H., Rebecca Water Scorpion Facts & Information (Nepidae). Pond Informer Water Scorpion Facts & Information (Nepidae) – Pond Informer Access Date: 4/29/2024

Cole, Eric. Professor of Biology, St. Olaf College. In-person question. 4/29/2024

Barns, Robert D. Invertebrate Zoology. (Holt-Saunders International, 1982)

Wilson, Amy Stephen Hillenberg created the undersea world of Spongebob. The Orange County Register via Wayback Machine Stephen Hillenburg created the undersea world of SpongeBob.(The Orange County Register) – Knight Ridder/Tribune News Service | HighBeam Research (archive.org) February 12, 2002. Archived June 10, 2014. Access Date: 4/29/2024

Crayfish vs. Lobsters: 5 Key Differences Explained. A-Z Animals Crayfish vs Lobster: 5 Key Differences Explained – A-Z Animals (a-z-animals.com) Access Date: 4/29/2024

THE PHYLUM PORIFERA. THE CIRCULATORY SYSTEM Porifera – The Circulatory System (weebly.com) Access Date: 4/29/2024

Hartfield, Paul & Hartfield, Elizabeth. Observations on the Conglutinates of Ptychobranchus greeni (Conrad: 1834) (Mollusca: Bivalvia: Unionoidea) The American Midland Naturalist 135, 370-375 (1996). 

L., Angaline Freshwater Scud Facts (Gammaridae). Pond Informer Freshwater Scuds Facts (Gammaridae) – Pond Informer Access Date: 4/29/2024

Images:

User Shi Annan. Hydra sp. 2010.jpg. Wikimedia Commons File:Hydra sp. 2010.jpg – Wikimedia Commons Licensed under Creative Commons Attribution-Share Alike 4.0 International Licence Access Date: 4/30/2024

Phylactolaemata (Freshwater Bryozoans). What-When-How Class Phylactolaemata (what-when-how.com) Access Date: 4/29/2024

Silver Lamprey. The Land Between Silver Lamprey- Species At Risk in The Land Between Accessed: 4/30/2024

User: Jeffdelonge. Nepa cinerea01.jpg. Wikimedia Commons File:Nepa cinerea01.jpg – Wikimedia Commons Licensed under Creative Commons Attribution-Share Alike 3.0 Unported Licence & Creative Commons Attribution-Share Alike 1.0 Generic License. Access Date: 4/30/2024

Cole, Charles. Unknown snail. own work. Photographed; 4/22/2024

User: Paul Herbert. Daphnia pulex.png. Wikimedia Commons File:Daphnia pulex.png – Wikimedia Commons Licenced under Creative Commons Attribution 2.5 Generic Licence Access Date: 4/30/2024

User: PDH. Cyclops.jpg. Wikimedia Commons File:Cyclops.jpg – Wikimedia Commons Public Domain as the work of an EPA employee. Access Date: 4/30/2024

User: Renee Grayson. Relict leopard frog tadpole 6. Flickr Relict leopard frog tadpole 6 | Renee Grayson | Flickr via User: Monkeystyle3000. Wikimedia Commons File:Relict leopard frog tadpole 6.jpg – Wikimedia Commons. Licenced under Creative Commons Attribution 2.0 Generic Use. Access Date: 4/30/2024 

User: Smithsonian Environmental Research Center. Cambarus_bartonii_08-01-20_0799. Flickr Cambarus_bartonii_08-01-20_0799 | Cambarus bartonii, Common … | Flickr via User: Smithsonian Environmental Research Center. Wikimedia Commons File:Cambarus bartonii 08-01-20 0799 (50190193252).jpg – Wikimedia Commons. Licenced under Creative Commons Attribution 2.0 Generic Use. Access Date: 4/30/2024

User: Taollan82~commonswiki (Onthank, Kirt L. ). Spongilla lacustris.jpg. Wikimedia Commons File:Spongilla lacustris.jpg – Wikimedia Commons Licenced under Creative Commons Attribution-Share Alike 3.0 Unported. Access Date: 4/30/2024

Cole, Charles. Unknown bivalve. own work. Photographed; 4/22/2024

User: Snek01. Gammarus roeselii.jpg. Wikimedia Commons File:Gammarus roeselii.jpg – Wikimedia Commons Licenced under Creative Commons Attribution 2.5 Generic Licence Access Date: 4/30/2024