Freshwater Animals

Freshwater macroinvertebrates are animals without backbones that live in or near the bottom of freshwater ponds, lakes, streams, and rivers for all or part of their life cycle. They are very important indicators of the health of these bodies of water, reflecting the quality of the water and the conditions of the habitat. Freshwater insects are a large group within the macroinvertebrates found in bodies of freshwater. They make up 90% of the organisms living at the bottom of a stream.

BENTHIC Organisms that live on the bottom are called benthic. Of the 2 million known insect species, there are over 80,000 species that fall into the macroinvertebrate category. Examples include mayflies, dragonflies, and beetles. Other benthic macroinvertebrates that do not fall into the insect group include crayfish, clams, snails, worms, and leeches.

Categories of Organisms: All living organisms in aquatic environments fall into one of three categories: Plankton – the drifters (unicellular algae, jellyfish) Nekton – the free-swimmers (fish) Benthos – the bottom dwellers (crabs, muscles)

Freshwater Animal Groups

Macroinvertebrates General Characteristics: No backbones Live in or near the bottom of ponds, lakes, streams for all or part of lifecycle Many are indicators of the health of the body of water They make up 90% of the benthic population in freshwater ecosystems Examples include: Aquatic insects Leeches and worms Clams Crayfish (Crawfish)

Aquatic Adaptations Freshwater macroinvertebrates are usually grouped by three characteristics: how they move, how they feed, and their tolerance to pollution (intolerant, moderately tolerant, or tolerant)

How They Move Macroinvertebrates have to be able to move or maintain their position in the water

How They Move Skaters – walk on the surface Planktonic - Float and/or swim in open water to get food and oxygen Can dive and swim when alarmed Mosquito Larva

How They Move Divers - Swim by rowing with hind legs in lakes and pools Swimmers – fish-like swimming in streams and lakes Predaceous Diving Beetle Scavenger Beetle

Water Penny – found in riffles How They Move Clingers - Attach to rocks and such in fast moving water Adaptations include: long claws and flattened bodies Sprawlers - Live on the surface of floating aquatic plants or fine sediments Adaptations include: Long legs Water Penny – found in riffles Riffle Beetle Deerfly Larva

How They Move Climbers - Live on overhanging branches, logs, etc. Adaptations include: Structures for climbing Burrowers - Live under fine sediment in pools of streams and lakes Adaptations include: Appendages or structures for digging Crayfish Water Scorpion

Adapted for movement on the water’s surface Type Description Skaters Adapted for movement on the water’s surface Scavenge on organisms caught in the surface film Planktonic May float and swim in open water or float at the surface to get oxygen or food; can dive when alarmed Inhabit open water (limnetic zone) of lakes, ponds, and bogs (lentic systems) Divers Can swim by rowing with the hind legs in lentic habitats and lotic pools Swimmers Adapted for fish-like swimming in lotic and lentic habitats Clingers Construct shelters, have long claws and flattened bodies for attaching to rock or other surfaces in lotic riffles and wave-swept rocky littoral zones Sprawlers Live on the surface of floating aquatic plants or fine sediments Adaptations include long legs Climbers Live on overhanging branches, logs, roots, or aquatic macrophytes Adapted for climbing plants or debris Burrowers Inhabit fine sediments of streams (pools) and lakes Adapted for digging

How They Feed Shredders Collector-gatherers Eat live or dead aquatic plant material Chew, bore, or gouge Collector-gatherers Eat small bits of decomposed organic matter Gather deposits from the bottom Scud Midge Larva

How They Feed Collector-filterers Scrapers Eat small bits of decomposed organic matter Filter out of the water Scrapers Eat algae, fungi, and other things found attached to plants or rocks Scrape food from the surface it is found on Black Fly Larva Water Penny

How They Feed Piercers Predators Eat live aquatic plants Peirce into the plant and suck fluids out Predators Eat live animals Engulf whole animals, or pierce into the animal and suck fluids out Water Boatmen Giant Water Bug

Feeding Group Food Preference Feeding Habits Shredders Live or dead aquatic plant material Chew, bore, or gouge Collector-gatherers Small bits of decomposed organic matter Gather deposits from the bottom Collector-filterers Filter matter out of the water Scrapers Algae, diatoms, bacteria, and fungi found attached to plants or rocks Scrape food from the surface it is found on Piercers Live aquatic plants Pierce into the plant and suck fluids out Predators Live animals Engulf whole animals, or pierce into the animal and suck fluids out

Pollution Tolerance Macroinvertebrates are used as indicators of pollution for many reasons: Found in all aquatic habitat types Most live or stay over a small area Well documented species and lifecycles Tolerance values range from 0-10. 0 is least tolerant 10 is most tolerant

Pollution Tolerance Examples High Tolerance Ex. Planaria High numbers indicate the water quality is very poor Low Tolerance Ex. Riffle Beetles High numbers indicate the water quality is very good

Freshwater Fish

General Characteristics Ectothermic (cold-blooded) – Their body temperature fluctuates with their surroundings Have backbones Have fins, scales, and gills Habitats Certain species of fish are adapted for certain water conditions. Some thrive in high oxygen, and some thrive in low oxygen Some prefer open water, and some prefer backwater areas

Feeding Groups Fish in each of the feeding groups have structures and adaptations to allow more efficient feeding: Ex.

Trophic Group Piscivores Invertivores Predatory fish that eat other fish Have large eyes for better sight Well-developed lateral line Invertivores Fish that eat invertebrates (crayfish, mollusks, insects, etc.) Feed on bottom Have fleshy lips or taste buds on barbels to detect prey Ex.

Trophic Groups Omnivores Herbivores Fish that eat any available food Feed on bottom Have fleshy lips or taste buds on barbels to detect prey Ex. Catfish Herbivores Fish that eat plant material Use pharyngeal teeth for crushing plant material (pharyngeal teeth are a modified gill arch in the throat from crushing plant material) Ex. Minnow

Pollution Tolerance Aquatic macroinvertebrates are also put into categories based on their tolerance to pollution. Tolerance values range from 0 to 10 with 0 being the least tolerant, and 10 the most tolerant. Tolerance values are assigned to those organisms used as pollution indicators.

Freshwater macroinvertebrates are used as indicators of pollution for many reasons: • Important part of all aquatic ecosystems • Found in all types of aquatic habitats • Fairly easy to collect • Have different levels of tolerance to an environmental disturbance • Most live or stay over a small area • Life cycles of most groups are well documented

POLLUTION TOLERANCE Fish are good indicators of water quality for many reasons: Live in water for their entire life Have long life spans Easy to identify and collect Communities are persistent and can recover from natural disasters

Freshwater Fish Families

General Characteristics Fish are cold-blooded animals, meaning their body temperature changes with the temperature of their surroundings. They have backbones and live their entire lives in water, breathing with gills and moving with fins. There are 247 species of freshwater fish in Texas alone. Some of these species are able to live in brackish (partly salty) water, such as in estuaries. All fish play an important role in the aquatic ecosystem

Fish Habitat Each species of fish has its own distribution and range of tolerance in which it can survive or thrive. The basic requirements for a fish’s survival include prey, cover, suitable water temperature, and dissolved oxygen levels.

Habitat Types Fish Species Streams Riffles (high dissolved oxygen) Darters, shiners Pools (calm) Sunfish, bass, catfish, suckers Backwater areas (low dissolved oxygen) Gar, bowfin, pirate perch Reservoirs Open water Shad, white bass, striped bass Shorelines with aquatic vegetation Sunfish, bass, shiners Quiet coves Gar, suckers

Feeding Groups Fish feed at all levels of the food chain, from bottom scavengers to top-level predators. Fish can be categorized into groups based on food preferences. Fish in each of these groups have form and structure adaptations to allow more efficient feeding.

Fish that eat plant material Trophic Group Food Preferences Adaptations Examples / Adaptations Piscivores (Predators) Fish that eat other fish Large eyes for better sight, well-developed lateral line to detect vibrations of prey in the water Large and small mouth bass,Flathead catfish, Gar, crappie Invertivores Fish that eat invertebrates (insects, worms, crayfish, mollusks, etc.) Feed on bottom – fleshy lips (suckers) or taste buds on their barbels (catfish) to detect prey Blue sucker, red shiner, bluegill, longear sunfish Omnivores Fish that eat any available food Shad, carp, channel catfish Herbivores Fish that eat plant material Use pharyngeal teeth (a modified gill arch in the throat) for crushing plant material Grass carp, stoneroller

Fish Structures

Gar Family Bodies are covered with diamond shaped plate scales Designed for backwater areas Breathe with gills or lung-like air bladder The air bladder is connected to the throat so it can breathe air. Spotted Gar Long-nose Gar Alligator Gar

Herring Family Bright, silvery, and flat-sided Feed on plankton Transparent eyelids Important for food – Fish meal in livestock feed and pet food

Carp and Minnow Family Largest freshwater fish family Can live almost anywhere and eat anything Keen sense of hearing Series of small bones connect the inner ear to the swim bladder The swim bladder picks up vibrations in the water and sends them to the inner ear Red Shiner

Invasive Carp Grass carp were brought from Asia into North America and Europe to control aquatic vegetation They became invasive, taking over waterways and eating up all the vegetation, and are regulated by Texas Parks and Wildlife Grass Carp

Sucker Family Have a toothless and sucker-like mouth with thick lips Have pharyngeal teeth Mostly omnivorous, feeding from the bottom

North American Catfish Easily recognizable by scaleless body, broad flat head, and barbels Barbels posses taste buds which help them to locate and taste food (especially in murky water and at night) Possess venomous spines at dorsal and pectoral fins

Blue Catfish Channel Catfish Flathead Catfish

Pirate Perch The position of the anus is behind the mouth Tolerant of high water temperatures and low dissolved oxygen Live mostly in swamps and backwaters

Topminnow Family Also called “killfish” Spend most of their time at the water surface Feed with upturned mouths and flattened heads

Livebearer Family The females give birth to live young Western Mosquitofish Sailfin Molly

Pupfish Family Very tolerant of high temperatures and low dissolved oxygen The most heat tolerant of all fishes Feed mostly on insects, snails, and crustaceans Most are threatened or endangered due to habitat loss or hybridization from non-native species Sheepshead Minnow

Temperate Bass Family White and yellow bass, white perch and striped bass (hybrid) Striped bass has been introduced into inland reservoirs and lakes Usually travel in schools in open water (pelagic)

White Bass Yellow Bass Striped Bass

Sunfish Family Includes sunfish, crappie, and large-mouthed bass Most are sedentary and hide under cover Green Sunfish Bluegill

Largemouth bass White Crappie

Perch Family All members are predatory Darters are adapted for life in fast-flowing streams Spend most of their time in between rocks, waiting for prey Orange-throat Darter

Drum and Croaker Family Only one member lives strictly in freshwater…the freshwater drum Makes a grunting sound by special muscles and tendons connected to its swim bladder Feed mostly on the bottom, grinding their food with pharyngeal teeth Freshwater Drum

Cichlid Family Native to Africa, Central and South America One species found in the Rio Grande River Popular aquarium fish because of bright colors Predatory, and some are considered invasive because they compete with our native basses and sunfish for food Rio Grande Cichlid

Common Freshwater Reptiles

Common Freshwater Reptiles Characteristics Reptiles are air-breathing vertebrates that are cold-blooded, meaning their body temperature is determined by their surroundings. Reptiles control their body temperature by moving to warmer or cooler areas as necessary.

There are many groups of reptiles found in freshwater ecosystems: Crocodiles and Alligators There are 21 know species of alligators, crocodiles, and caimans in the world, but only two are native to the United States—the American alligator, and the American crocodile. The American alligator (Alligator mississippiensis) is native to Texas, but the crocodile is not. The American crocodile is native to the southern-most tip of Florida.

The American alligator is the largest reptile in North America. It can grow to more than 19 feet long. They inhabit the eastern part of Texas, and most of the Gulf of Mexico coast. They are found in rivers, swamps, lakes, and bayous, and can tolerate the brackish water of coastal marshes. During the coldest months and in dry seasons, they dig deep holes in muddy banks, where they hibernate. They are carnivorous predators that feed mostly on fish, snakes, turtles, small mammals, and waterfowl. The alligator can chew underwater, but must surface to swallow. When breeding, the female builds a large mound of mud and leaves, and drops up to 60 hard-shelled eggs into the center. The female stays to protect the nest for the 9 weeks it takes for them to hatch.

Turtles Turtles are the oldest living reptiles. Freshwater turtles have a toothless, horny beak and a shell of bony dermal plates, usually covered with horny shields, enclosing a soft body. The head, limbs, and tail may be drawn into the shell when necessary. Turtles have scaly skin and are often seed basking on rocks and logs. They lay eggs in cavities dug out by the female. Texas is home to 35 species, with about 240 found worldwide. There are 4 families of Turtles found in Texas: Snapping turtles, soft-shelled turtles, box and water turtles, and musk and mud turtles

Snakes Snakes are a limbless, scaled reptile with a long tapering body. Over 2300 species of snakes are known worldwide. They live all over the world, but are absent from many islands, such as Ireland, New Zealand, and Hawaii. There are two families of snakes in Texas: vipers (poisonous) and Colubrids (nonpoisonous)

Freshwater Amphibians

General Characteristics Amphibians have many characteristics that are in between fish and reptiles. The work “amphibian” means “living a double life”. Larvae of amphibians have gills and live in water, while adults breathe air through either their skin or lungs. Amphibians, like reptiles, are vertebrates that are cold-blooded. They have moist, glandular skin and their toes lack claws. They lay gelatinous-covered eggs in moist areas. Groups include frogs, toads, salamanders, and newts. Frogs have smooth skin, webbed feet, no tail, and have long legs for leaping, while toads have warty skin and short legs for hopping. They both feed on insects, crayfish, minnows, and on almost anything smaller than themselves.

Freshwater Aquatic Plants

General Characteristics Aquatic plants have adapted to living in a variety of water conditions ranging from swift-flowing to stagnant. They are an important part of an aquatic ecosystem. Plants affect water quality by adding oxygen to the water column and by stabilizing bottom sediments and shorelines to reduce turbidity. They also provide protection, feeding areas, and spawning areas for fish, invertebrates, & waterfowl.

Groups – Aquatic plants are grouped in three categories, according to their growth habits Floating plants – plants that float freely on the surface and plants that are rooted on the bottom with their leaves floating on the surface Emergent plants – plants that are rooted to the bottom and grow above the water along shorelines and in shallow water areas. Submerged plants – plants that are generally rooted at the bottom and are completely underwater, except for seed heads or flowers.

Nearly all aquatic plants live in the littoral zone (near-shore area.) The extent to which they move away from shore depends on the depth that light penetrates into the water column. In large lakes, plants may inhabit only shallow near-shore areas. In shallow lakes, ponds, and slower-moving streams and rivers, aquatic plants may inhabit the entire water body. Free-floating plants cause problems by covering a water body and reducing the amount of light available to other aquatic organisms.

Nonnative and Invasive Species Most Texas streams or reservoirs are home to at least one nonnative species (those species that enter an ecosystem beyond their historic ranges). In Texas, at least 35 nonnative species have become established in aquatic habitats.

How Did They Get Here? Increasing local food supplies Authorized enhancement of sport and commercial fisheries Manipulating aquatic ecosystems to control pests or nuisance plants Improving the appearance of an area Unauthorized stocking of ponds or waterways by fishermen Hitchhiking on boats (snails, plants) Releases from personal aquariums (plectosimus) Escape from aquaculture facilities Canal systems Angler bait buckets

Negative Impacts of Non-native species Prey on native fish Altering established aquatic food webs Introducing new parasites or diseases Altering habitats Damaging the genetic integrity of native species by hybridization Out-competing native species for resources Clogging irrigation canals Endangering commercial and recreational fishing due to lower numbers of native species