River-Lab 5 Guide Manual Plankton Pages PLANKTON PAGES

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1 PLANKTON PAGES Phytoplankton Phytoplankton include the microscopic green algae, the yellow-green algae (e.g. diatoms), dinoflagellates and blue-green bacteria. They all make their own food through photosynthesis. They are found in all types of water fresh and salt water; polluted and clean; hot and cold. They occur mostly as single-celled organisms, but many form filaments (strands) or colonies (clumps of cells). They are the base of food chains that start in the water. Phytoplankton are also very important because these microscopic algae that live in the oceans produce the majority of oxygen for our planet. Green Algae General Information There are over 6,000 species of green algae, most of which live in fresh water. Freshwater microscopic green algae are single-celled organisms that can occur individually, as a long string (strand, filament), or as a slippery film or mat on submerged rocks and vegetation (sticks, logs, leaves). The green color comes from the chloroplasts in the algal cell. The chloroplasts contain chlorophyll the substance that performs photosynthesis in plants and plant-like organisms. Through photosynthesis, green algae can make the food they need to grow. Green algae are called producers because they use sunlight to make the food they need to grow (they do not eat ). Since they are producers, green algae are the base of aquatic food chains. They are a major source of food for freshwater animals. Green algae produce oxygen as a by-product of photosynthesis. Spirogyra Spirogyra is a common green alga found in freshwater in quiet areas of streams, rivers, ponds, and marshes. This phytoplankton grows in long thin un-branched strands (filaments, strings) the thickness of a human hair. There are over 400 species of Spirogyra. The filaments can form clumps or mats that can be seen just under the surface of the water. Rectangular-shaped cells are connected end-to-end to form the filaments. Inside each cell are long spiral-shaped chloroplasts containing the chlorophyll. Spirogyra is named for these spiral chloroplasts; the chlorophyll is used in photosynthesis to enable Spirogyra to make its own food. Oxygen is produced as a byproduct of this process. Spirogyra Green Thread-like 2009 Mill River Wetland Committee, Inc. 5GM - 108

2 Spirogyra reproduces in two ways. One way is through simple cell division: the cell divides into two separate new cells, making the strand longer. Spirogyra can also reproduce when two strands touch. The strands exchange material through tubes that form. This contact produces a special cell that can live through very hot, cold, or dry conditions. When conditions improve, a new strand of Spirogyra can grow from this cell. Eaten by Like all green algae, spirogyra is a producer (see above for General Information on green algae) because they use sunlight to make the food they need to grow (they do not eat ). Spirogyra is an organism at the base of aquatic food chains. They are eaten by seed shrimp, aquatic worms of all types, freshwater snails, and fish. Desmids Desmids are single-celled green algae that have many shapes circular, crescent-shaped, elongated, star-shaped, and spherical. They have two equally-shaped sides (symmetrical). Desmids do not have flagella, but they do have knobs, spines, granules that can be seen sticking out of the cell wall. There are over 500 species of desmids around the world. Desmids range in size from 0.01mm to 0.4 mm. Desmids are found in freshwater in areas that are still and non-polluted. They either float or are attached to plants or rocks in the water. They grow best in acid conditions. Some can move by secreting mucus through pores in the cell wall. The desmid glides over the mucus. They move toward light in order to photosynthesize. Desmids reproduce in two ways. One is through cell division, which creates two exact copies of a desmid from one. The other way is also similar to Spirogyra: two cells touch, and a special cell forms which can grow into a new desmid. Eaten by Like all green algae, desmids are producers (see above General Information on Green Algae) and are one of the organisms at the base of aquatic food chains. Desmids are eaten by water fleas, copepods, rotifers, insect larvae, seed shrimp, and nematodes. 5GM Mill River Wetland Committee, Inc.

3 Volvox Volvox is a hollow, ball-shaped colony made up of a single outer layer of green algae cells. There are 500 or more cells per colony, linked together with jelly-like strands. The ball is semitransparent. A colony can grow up to 2 mm. Each cell has two flagella that beat together to move the colony through the water with a smooth rolling motion. Each cell also has a red eyespot that detects light and a cup-shaped chloroplast containing its chlorophyll. Volvox are found in sunny, clean freshwater areas with lots of nutrients, such as the still water areas of rivers and streams, ponds, lakes, ditches, and even puddles. Volvox cells make daughter cells inside the center of the ball through repeated cell division. When there are enough cells inside, the parent colony disintegrates and releases the cells. Eaten by Like all green algae, Volvox are producers (see above General Information on Green Algae) and are an organism at the base of aquatic food chains. Volvox are eaten by rotifers, seed shrimp, aquatic worms of all types, copepods, and water fleas. Chlorella Chlorella is a spherical, single-celled green phytoplankton which is found individually or clumped together into a ball. They are very small mm. They do not have flagella. They are found in freshwater and saltwater and in soils. They also live inside hydras (see page X) and freshwater sponges, making those organisms appear green Mill River Wetland Committee, Inc. 5GM - 110

4 Chlorella multiplies by simple cell division and when conditions are right they multiply rapidly. Eaten by Like all green algae, Chlorella are producers (see above General Information on Green Algae) and are an organism at the base of the aquatic food chain. Chlorella are eaten by water fleas, copepods, seed shrimp, rotifers, and aquatic worms. Yellow-Green Algae General Information Yellow-green algae are photosynthetic phytoplankton that are found mostly in freshwater but some species are found in saltwater, and in soils. There are over 600 species, many of which have flagella (whip-like tail). They are single-celled organisms and similar to green algae, they can occur individually, as colonies, as strands, or as slimy mats. Yellow-green algae contain chlorophyll the substance that performs photosynthesis in plants and plant-like organisms. They are yellow-green in coloring because they contain yellow pigments in addition to the green chlorophyll. The yellow pigment helps the chlorophyll capture light for photosynthesis. Through photosynthesis, yellow-green algae can make the food it needs to grow. Yellow-green algae are called producers because they use sunlight to make the food they need to grow (they do not eat ). Since they are producers, yellow-green algae are organisms at the base of aquatic food chains. They are a major source of food for freshwater animals. Yellow-green algae are important in oxygen production in the ocean. Diatoms Diatoms are yellow-green algae (phytoplankton.) They are one of the most abundant of all organisms that live in fresh and salt water. They contain chlorophyll for photosynthesis, and salt water species are important in oxygen production in the ocean..- Diatoms reproduce by simple cell division. The cell divides into two separate new cells. Diatoms Geometric Glass-like color of cell wall 5GM Mill River Wetland Committee, Inc.

5 Eaten by Like all yellow-green algae, Diatoms are producers and one of the organisms at the base of aquatic food chains. (See above General Information on Yellow-Green Algae.) Diatoms are eaten by dinoflagellates, copepods, water fleas, seed shrimp, rotifers, insect larvae, aquatic worms of all types, other small aquatic animals, and fish. Blue-Green Bacteria--Cyanobacteria Blue-green bacteria used to be called blue-green algae. Since they have features different from algae and features more like bacteria, they have been renamed. These differences include the material its cell wall is made of as well as the way material is arranged inside the cell. These bacteria are named for the blue-green color (cyan) of the pigments inside the cell that help the green chlorophyll capture light for photosynthesis. Chlorophyll is the substance that performs photosynthesis in plants and plant-like organisms. Through photosynthesis, blue-green bacteria can make the food it needs to grow. Blue-green bacteria are called producers because they use sunlight to grow (they do not eat ). Since they are producers, blue-green bacteria are at the base of aquatic food chains. They are a major source of food for freshwater animals. Blue-green bacteria produce oxygen as a by-product of photosynthesis. They are important oxygen producers. Most blue-green bacteria are single-celled but some form chains. Some have a gel-like substance surrounding them. These blue-green bacteria have no flagella but can glide on the gel. Blue-green bacteria live mostly in freshwater habitats. Some do live in the ocean. There are over 1500 species. They grow attached to rocks, plants, and are in bottom debris among the mud in quiet water areas that are rich in nutrients. Blue-green bacteria can convert nitrogen gas into a usable form of nitrogen (needed for growth) for itself and for the other phytoplankton and plants in their habitat Mill River Wetland Committee, Inc. 5GM - 112

6 Blue-green bacteria reproduce by dividing into new two cells. Eaten by Blue-green bacteria are producers and are one of the organisms at the base of aquatic food chains. Blue-green bacteria are eaten by fish, copepods, water fleas, seed shrimp, rotifers, and aquatic worms of all types. The blue-green bacterium, Nostoc, is the most common in freshwater. It grows in long strands that are enclosed in a mass of a gel-like substance. Some blue-green bacteria, such as Anabaena, produce toxins that may cause animals that drink the water to become sick and die. Zooplankton General Information Zooplankton is made up of microscopic animals and animal-like living organisms. They cannot make their own food. They are consumers. They live by eating phytoplankton or other zooplankton. Zooplankton are complex organisms composed of more than one cell, yet most zooplankton are usually less than one millimeter in length. Zooplankton are transparent nearly invisible. Zooplankton are very weak swimmers and are mostly carried about by the current. The most common and numerous zooplankton are the microscopic crustaceans, related to shrimp. There are two types of zooplankton permanent and temporary. Permanent zooplankton consists of organisms that remain microscopic for their entire life cycle. They have many strange shapes and appendages. Temporary zooplankton consists of the microscopic immature and egg stages of fish, insects, crustaceans, shellfish, etc. Some of these immature states do not look at all like the adult. As they grow larger, these animals depend on smaller plankton as their food. The descriptions that follow are of the permanent freshwater zooplankton. Water Fleas Water fleas are permanent members of the freshwater plankton community. There are hundreds of species. They are one of the most numerous forms of zooplankton in fresh water. They are found everywhere in nutrient-rich waters except for water that is fast- flowing or polluted. They range in size from 0.1mm to 3mm. The antennae beat to move them in fast, jerky, circles through the water. The jerky movements resemble the hopping of a flea hence their name. The water flea s body is enclosed by a carapace made of two shell-like flaps that are hinged at the back, similar to a clam shell. This carapace covering is thin and allows 5GM Mill River Wetland Committee, Inc.

7 light to pass through. The internal structures can be seen when viewed with a microscope. The heart can even be seen beating. Inside the carapace, the water flea body is made up of a heart, tiny brain, compound eye, mouth, digestive system, and an egg chamber. The two pair of antennae and five to six pairs of hairy legs are usually not covered by the carapace. The eye is a very prominent feature and can detect light. Water Fleas Eggs inside body Transparent When legs kick, water flea "spins." Water fleas eat microscopic phytoplankton, rotifers, bacteria, and tiny pieces of organic debris. They beat their legs rapidly, creating a water current that brings food towards them to collect on the hairy legs. The food is then passed up along the legs into the mouth. Eaten By Water fleas are a very important food source for young and adult fish such as largemouth bass. Up to ninety-five percent of the contents of some fish stomachs are water fleas. Water fleas are also eaten by hydra, copepods, planarians, nematodes, mites, and immature and adult aquatic insects. During the spring and through the summer, water fleas produce female babies from unfertilized eggs. They carry between two and fifty eggs in the egg chamber (in their body). Female water fleas can have a new brood of eggs every 10 days. When the eggs hatch, young water fleas look just like the adults, only much smaller. The young molt several times in the two weeks it takes them to mature. Once mature, they can start to have eggs and hatch babies. If a female had 50 babies and those 50 babies had 50 babies, after four weeks there could be 125,000 water fleas. [50 x 50 x 50=125,000] After ten weeks (five generations), there could be as many as 15 billion descendents. But not all 2009 Mill River Wetland Committee, Inc. 5GM - 114

8 water fleas survive to reproduce. So the actual number of water fleas after ten weeks would be smaller than 15 billion but could still be an enormous amount. In stressful conditions, or at the end of the growing season, the females will produce both females and males that can mate. Mating produces a special egg (resting egg) that is capable of surviving the stressful conditions of winter. In spring, or when conditions improve, these eggs produce more females. Copepods Copepods are members of the freshwater plankton community. There are over 6,000 kinds of copepods. They live in both fresh and salt water but are more numerous in salt water than fresh the opposite of water fleas. Freshwater copepods live among the vegetation in quiet backwaters of streams and rivers or open areas of ponds and lakes. They are one of the first kinds of zooplankton to emerge in spring from resting eggs that have rested in the bottom mud over the winter. Some adult copepods survive in the bottom mud over the winter and become active in spring. Copepods are crustaceans; they are related to larger crustaceans such as shrimp and lobsters. Crustaceans have a hard exoskeleton a covering over the body. Copepods are grayish-brown. They molt this covering as they grow. The body has nine segments connected by flexible tissue. Female copepods carry their egg sac(s) on the outside of their bodies near the tails. Copepods have a few pair of legs near the mouth that are used in eating. They have five pair of swimming legs outside of the exoskeleton and two antennae on the head. The antennae beat like tiny oars. They use the antennae and the swimming legs to swim through the water hence their name: cope=oar + pod=foot. They swim in fast jerks by kicking the legs backward and pressing their antennae straight back. This kick sends them through the water. After kicking itself forward or upward, the copepod spreads out its antennae, which act as a parachute to slow down the copepod body as it sinks. Copepods eat single-celled organisms such as diatoms and bacteria; smaller zooplankton than themselves such as water fleas and copepods; and decaying plants and animals. They grab their food with the legs near the mouth and pass the food into the mouth. Under a microscope, the food can be seen going into the digestive tract. Eaten by Copepods are eaten by fish larvae, young and small fish, other copepods, planarians, nematodes, mites, and aquatic insects. They are a very important source of food for fish. 5GM Mill River Wetland Committee, Inc.

9 Cyclops Copepod The Cyclops copepod is named because it appears to have only one eye. The eye is a combination of two eyespots that can see light and detect moving objects. Cyclops copepod is shaped like an upside-down bowling pin, with the head area wider than the tail. Cyclops copepods range in size from ½ mm to 3mm in length. Cyclops antennae are long about onethird as long as its body. Male antennae are more irregularly-shaped than the female antennae, and have pincers (claws) on them to hold the female when mating. Female cyclops copepods have an egg sac on each side of the body. Each sac holds an average of thirty eggs. The eggs are fertilized inside the female. The female carries the eggs in the two egg sacs for one to five days. Under the right conditions, a female could produce eggs three times in one month, totaling 180 eggs per month. If all her eggs hatched, one female copepod could produce 1000 eggs by fall. However, not all will become adults, since they can be eaten by other animals in all stages of their lives. The eggs hatch into a larval form that looks very different from the adult. It takes six months to a year for the young to mature. They molt eleven times as they grow into the adult form. Cyclops o Upside-down bowling pin shape o 2 egg sacs on outside of body Canthocamptus Copepod The body of the Canthocamptus copepod is shaped differently than the Cyclops. Its head is only slightly larger than the body segments which barely taper toward the tail. It has short antennae that do not go past the first body segment. The males antennae are wider than the females. Females usually have only one egg sac. Canthocamptus can be found crawling around on rocks in the quiet areas of a river Mill River Wetland Committee, Inc. 5GM - 116

10 Canthocamptus Slightly tapered body shape Short antenna 1 egg sac Seed Shrimp Seed shrimp are members of the permanent freshwater plankton community. There are over 2,000 species of seed shrimp. They are named seed shrimp because they look like a seed with a shrimp inside. A hard shell-like carapace protects the seed shrimp s soft body and head. The carapace has two parts connected by a hinge, similar to a clam shell. The carapace ranges in color from yellow to black and is covered by many little hairs. The seed shrimp s coloring prevents its insides from being seen when viewed through a microscope. Seed shrimp live on and among the submerged plants and debris in quiet areas of a river or stream. Without a microscope, the seed shrimp looks like a tiny black dot moving smoothly through the water. When viewed under a microscope, a seed shrimp does not look alive until its legs and antennae stick out from the carapace and it swims away. A seed shrimp is usually about 1mm wide. Inside the carapace, the body has five to eight pair of legs, two pair of antennae and a digestive system with a mouth. Seed shrimp have one, two, or three eyespots that detect light and dark. The antennae and all the hairs on the carapace and legs help the organism sense objects around it. Seed shrimp Opaque can't see inside of shell to body Oval shape 5GM Mill River Wetland Committee, Inc.

11 Seed shrimp eat almost anything, including bacteria, molds, algae (single-celled or colonial), other microscopic life, and decaying plants and animals. Eaten by Seed shrimp are eaten by water mites, nematodes, mallards and other ducks, and a wading bird called a Great Egret. They are only a small part of the food eaten by fish. Seed shrimp reproduce in two ways. Unfertilized eggs develop inside a female and eggs develop after a male has fertilized them. All eggs are raised in a chamber inside the female. Just-hatched seed shrimp do not look like the adults they look more like immature water fleas. Seed shrimp molt many times before becoming mature and looking like the adults. Rotifers Rotifers are members of the permanent freshwater plankton community. They are found attached to anything under water in quiet areas of the freshwater system. There are over 2,000 types of rotifers, most of which (95%) live in freshwater. They are the smallest multi-celled animals in the world 0.01mm to 0.5mm. A rotifer body is a soft, flexible bag-like structure that can change its shape by contracting or stretching out. This body has toe-like projections on one end and a pair of disks with cilia (tiny hair-like projections) that rotate around a mouth at the other ( head ) end. The rotating disks make the rotifer to swim through the water in a spiraling motion. The bag-like body surrounds a fluid-filled cavity that contains the rotifer s digestive system, consisting of its mouth, jaws, stomach, and intestines. This cavity also contains the rotifer s brain, eyespots, and reproductive system. The rotifer also moves in an inch-worm style. It brings it toes forward under its head, and then extends its head and body forward. Rotifers Move very quickly Transparent 2009 Mill River Wetland Committee, Inc. 5GM - 118

12 The rotating disks also create a current that brings food to the rotifer s mouth. Rotifers eat dead and decaying organic matter, single-celled algae, blue-green bacteria and other single-celled microscopic organisms. Before the food goes into the stomach, it is crushed and ground up by a jaw-like structure. Eaten By Rotifers are eaten by worms, copepods, water fleas, and fish. Female rotifers can produce eggs without fertilization. For some species, males have never been found. Some species lay eggs on vegetation in the water where the eggs remain to develop and hatch. In other species the eggs develop within the body and hatch as small rotifers. At certain times, males are produced that can mate with a female. The egg from mating develops inside the female and hatches into a form called a zygote that can survive extreme temperatures and heat. The adult rotifer also can protect itself from drought or excessive heat by producing a thick body covering that protects it while it waits for better conditions. Rotifers live from two to twenty days, depending on the species. Annelids (Segmented Worms) Annelids are a large family of worms that have segmented bodies. There are over 9,000 types of annelids, including earthworms and leeches. One type of annelid, the bristle worm, has several species. On land some bristle worms grow from 1 to 180 meters long. However, freshwater planktonic bristle worms grow to only 40 mm. Each segment of a bristle worm s body, except the first, has bundles of bristles. Each segment has muscles that go around the body and others that go down the body. The worm crawls by pushing the bristles against surfaces such as rocks, debris, and mud at the bottom of quiet waters of the freshwater system. Bristle worms can swim by whipping their bodies back and forth very fast in the water. An annelid s body is a tube-within-a-tube. The inner tube is a digestive tract with a mouth at one end and wastes coming out at the opposite end. Some worms are transparent. You can see the digesting food in the inner tube through a microscope. Some annelids have eyespots that detect light and dark. Freshwater microscopic bristle worms live in soil and among the debris in the quiet water areas of the freshwater system. Annelids Bristles on sides of worm 5GM Mill River Wetland Committee, Inc.

13 Bristle worms eat the decaying plants and animal matter in the mud as they borrow through it. In the mud are algae, diatoms, and other decaying plants and animals. These worms play an important role in cleaning up dead plants and algae, which helps to maintain the oxygen supply in the water. Eaten By Bristle worms are eaten by fish of all sizes, water mites, and hydra. Planktonic bristle worms can reproduce in two ways. Planktonic bristle worms have both male and female parts on the same worm. Mating between two individuals is necessary to produce young worms. Planktonic bristle worms can also reproduce by budding. In this process, a small lump forms on the end of a worm. After developing four or more segments, this section will break off, forming a new worm. Nematodes (Round Worms) Nematodes are worms that do not have segments. There are over 20,000 species, 1000 of which live in freshwater habitats. Some nematodes are harmful (if ingested) to larger animals, including humans and animals such as dogs and cats. Nematodes live in the top of the mud on the bottom of quiet waters of streams, rivers, ponds, lakes, and wetlands. Planktonic nematodes look like tiny thread-like hairs whipping around in the water. Their bodies are small 0.3mm to 1 cm long and are pointed at both ends. The body is basically a tubewithin-a-tube. The inner tube is the digestive system. One end of this tube is the worm s mouth. The other end excretes wastes. The outer tube is protected by a tough and flexible shell-like covering called a cuticle. To grow, nematodes molt this protective covering. Nematodes No bristles 2009 Mill River Wetland Committee, Inc. 5GM - 120

14 Nematodes eat a wide variety of food bacteria, fungi, algae, small animals, and dead and decaying matter. They eat much dead and decaying matter, thus helping to maintain the oxygen supply in the water. The food is pulled into the mouth and is crushed inside by a jaw-like throat just below the mouth. Eaten By Nematodes are eaten by fish, water mites and hydra. Both a male and a female are required for nematode reproduction. After fertilization, a female deposits her eggs in the mud. Nematodes can lay as many as 200,000 eggs in a day! The eggs hatch into larvae which then develop into tiny worms that resemble the adult. Young worms molt four times before becoming a mature adult. Planarians Planarians are gray, brown, or black, flat, soft, worm-like organisms that live in salt and fresh water. In freshwater they live in both quiet waters and flowing waters in a river basin. They hide under rocks and among submerged leaves and other debris on the bottom of the water. Planarians range in size from 3-12 mm. The flat body does not have a body cavity. The head is triangular-shaped and contains two eyespots that are not centered. This makes the planarian look cross-eyed. The eyespots are not real eyes; they only detect light, which planarians avoid. The mouth is on the underside of the body in the center of the animal. The mouth both ingests food and excretes wastes. The mouth releases digestive enzymes to the outside of the body to begin the digestion process and then sucks the food inside. Planarians have cilia on the underside of the body that beat to enable the animal to glide on a moist surface. Planarians can regrow lost or damaged parts of the body. Planarians Triangular-shaped head Flat 5GM Mill River Wetland Committee, Inc.

15 Planarians eat diatoms, water fleas, copepods, aquatic insects, and dead and decaying plants and animals. Many are scavengers and eat a lot of dead and decaying matter, thus helping to maintain the oxygen supply in the water. Eaten By Planarians are eaten by fish, water mites and hydra. Planarians reproduce in two ways. They have both male parts and female parts on the same animal, but mating between two separate individuals is necessary. After fertilization, an egg develops inside the female. The egg is released with a protective capsule around it. A very small planarian hatches one week later. Planarians can also reproduce by budding. A new worm grows from a part of the adult worm and then breaks off. Water Mites Water mites look like small, fat spiders and belong to the spider family. Water mites live in quiet, shallow areas of the river system, in and among the bottom debris and rooted water plants. Most water mites live in freshwater; only a few are found in saltwater. They are active during the day all year long even under the ice in winter. Mites vary in size 1 5 mm. Their rounded bodies are often brightly colored red, yellow, green, or blue. They have two double eyes and two palps (parts used for capturing food and eating), all at the front end of the body. Their four pairs of hairy-looking legs are also attached near their front end. Mites can run on the water s surface, on the bottom debris, or on plants. They can also swim by moving their legs very fast, but, if they stop moving, they will sink. The hair-like projections on their legs slow down their sinking. Water mites Often red Looks like a spider 2009 Mill River Wetland Committee, Inc. 5GM - 122

16 Some mites eat tiny worms, other mites, water fleas, and copepods. They grab the animal with their palps, pierce it with special razor-sharp jaws, and suck out the body juices, thus killing the prey. Some mites feed on larger aquatic animals by sucking out the juices, which may kill the animal, depending on its size. Some mites are scavengers and eat dead and decaying plants and animals. Eaten By Mites are eaten by hydra, aquatic insects, water fleas, copepods, and small fish. After mating, female water mites lay bright red eggs on the undersides of leaves of aquatic plants. After one to six weeks the eggs hatch into tiny larvae that do not yet look like the adult. These larvae attach to water insects such as dragonfly larvae. They suck juices from these animals. Due to the tiny size of the mite larvae, the sucking doesn t kill the much larger insect larvae. When the mite larvae are big enough, they change into a form called a nymph that resembles the adult but is not yet mature. The nymph eats the same food as an adult water mite as it grows. The nymph then it will attach to a plant and develop (through metamorphosis) into the mature adult. Hydra Hydra are freshwater cousins of jellyfish, coral, and sea anemones but are very small (up to 3mm). They are plentiful in unpolluted water. They attach to aquatic plants and submerged rocks, leaves, twigs, etc. in ponds, lakes, rivers, and streams. Hydra have a soft, sac-like body with an opening the mouth surrounded by five to eight tentacles at the top of the body. The mouth leads to the digestive system, which is a hollow tube. The hydra s wastes are also eliminated through the mouth. The tentacles and the whole outside of the body are covered with stinging cells that the hydra use to inject poison into their prey to paralyze them. Hydra are gray to brown but some appear green if green phytoplankton, Chlorella, live inside. The hydra and the algae help each other: the hydra uses the oxygen produced by the algae for the hydra s respiration, and the algae use the carbon dioxide produced by the hydra for the algae s photosynthesis. A hydra attaches itself to surfaces under the water with a sticky glue-like substance. It can change its size by contracting and extending its body while it is attached. To move, a hydra can detach and float in the water current or glide on its foot like a snail. A hydra somersaults by attaching its foot onto some underwater surface and attaching its mouth and tentacles alongside. The hydra then releases its foot, re-attaching it in a place within its reach and then releases its mouth and tentacles and brings them up to re-attach alongside the foot. Repeating this process moves the hydra in whatever direction it chooses to go. 5GM Mill River Wetland Committee, Inc.

17 Hydra Tentacles Hydra are carnivores: they eat other animals such as worms, copepods, water fleas, and just hatched fish. While attached, hydra sweep their tentacles, looking for prey. Eaten By Hydra are eaten by fish and aquatic insects. When food is plentiful, hydra reproduce by budding. A small swelling appears on the adult and grows until a new hydra is formed. The new hydra then breaks off. Under the right conditions, a bud can be formed every few days. Hydra also reproduce by mating. Under certain conditions, one hydra will grow female parts, and another will grow male parts. After the eggs are fertilized, they are covered by a tough coating and are laid among the vegetation. The eggs will rest until conditions are better for the hatching of the young hydra Mill River Wetland Committee, Inc. 5GM - 124