Drosera rotundifolia (Sundew, Round-leaved)
The round-leaved sundew has a number of small rounded leaves, about 1.3 cm wide, attached to a central stem, each by a 2.5 to 5 cm long petiole. The modified leaves form a sort of rosette. Each leaf has glandular hairs around its edge and most leaves have a drop of a sticky substance attached to the end of each hair. Insects such as ants become trapped in the drops. When they try to escape their frantic motions cause the leaf to fold over the insect. The whole process takes about 30 minutes. The prey is subsequently digested and the digested nutrients, containing essential, nitrogen containing amino acids, are absorbed into the plant, supplementing food produced photosynthetically. White flowers are formed at the top of an erect fertile stalk that rises from the center of the rosette. Plumbagin, a quinnone, derived from the sundew apparently has anti bacterial, anti viral and anti fungal properties. Tea brewed from the leaves has been used to treat coughs, asthma, and bronchitis and has been used as an aphrodisiac.
Drosera intermedia (Sundew, Intermediate Leaf)
Note that the leaf in this species is more elongate than the round-leaved sundew, otherwise they are similar.
Lentibulariaceae (Bladderwort Family)
Utricularia cornuta (Bladderwort, Horned)
This semi aquatic plant lacks roots. Thin, branched white leaves arise from the stem and extend throughout the upper part of the Sphagnum mat. Rows of small hollow bladders (sacs), shown above, are attached to the leaf branches. When tiny organisms come in contact with sensitive hairs near the bladder opening, a “door” opens outward creating an inward suction, drawing the prey into the bladder where they are digested usually in about one hour. The bladders shown above are from the horned bladderwort and the common yellow bladderwort. The digested nutrients are then distributed throughout the plant. All of the plant parts discussed above are intertwined with other plants on the heath surface making them difficult to isolate. Visible stalks extend from each plant base about 0.3 meters above the heath surface. Each bears 1-2 yellow flowers. The plant has been used medicinally as a diuretic.
Sarraceniaceae (Pitcher Plant Family)
Sarracenia purpurea (Pitcher Plant)
The carnivorous pitcher plant consists of a group of pitcher (Vase) shaped, hollow, reddish-green leaves, each about 10 to 30 cm tall, connected to a stem that extends roots downward into the bog. A large flower, supported by a stem arises from the center of the modified leaves. Several spider species lay their eggs inside this structure. Tea made by steeping leaves in water has been used to treat fever and subdue chills. Native Americans consumed pitcher plant roots to treat liver and lung diseases.
Each “pitcher” has an upper, flared lip that has hairs that curve downward and is generally partially filled with water. Insects attracted to the “pitcher” crawl inside the modified leaf and are prevented from leaving by the downward pointing hairs. Eventually the insects tire and fall into the water where they are digested by bacteria for the most part. The products of digestion, high in nitrogen containing amino acids, are absorbed by the leaf, supplementing photosynthetically produced organic matter. The water contained by the leaves supports a community of interesting organisms that include bacteria, protozoa,rotifers, chronomid larvae (Metriocnemus knabi) , mosquito larvae (Wyeomia smithii), and fly larvae. Videos of some of the pitcher plant inhabitants are presented below.
1. Insectivory: As mentioned above pitcher plants supplement their diet with digested insects.
2. The pitcher plant leaf, described above, is modified to trap and hold insects.
Invertebrates commonly associated with Serracenia purpurea
1. Phylum Arthropoda, Class Insecta,
a. Chironomid Larvae (Metriocnemus knabi) X40
The head capsule is the first visible structure. The two black eye-spots are locatedlaterally on the head followed by two small antennae attached to the dorsal surface of the head capsule. Two, black tipped, lateral mandibles can be seen at the beginning of the video moving back and forth. The labrum (lower lip) lies beneath the mandibles and is used to scrape food (insect remains and plant cells) into the mouth. There are 11 segments behind the head. The first segment bears a single, ventral proleg with numerous spines. It is visible briefly at the start of the video. It is responsible for pulling the animal forward. The last segment gives rise to two prolegs with hooks. Transparent finger-like anal gills are visible underneath the prolegs. A system of visible tubes (tracheae) delivers oxygen throughout the animal. A wide digestive tract runs the length of the larva. The larvae spend most of their time feeding on dead insects lying at the bottom of the pitcher. They may also feed by scraping epidermal cells from pitcher plant leaves.
b. Mosquito Larva (Weyomia smithii)
Video A: The posterior end is shown above. Note the terminal respiratory extension on the last abdominal segment. There are two dark tubes within this extension (Tracheal Tubes) that open to the outside. When this extension is pushed above the surface of the water inside the pitcher plant, air containing oxygen moves inward through the tracheal tubes and is distributed throughout the larva. Paddle-shaped gills lie below this structure and are connected to the tracheal system. There are nine abdominal segments. The most anterior is attached to a box-shaped thorax followed by the head capsule. The head capsule has a pair of lateral eye-spots and a pair of dorsal antennae. Internally two dark patches are visible. These are the feeding brushes that can be seen extending outward and then retracted over and over again. The brushes filter food from the water inside the pitcher plant.The swimming larvae are considered top predators feeding for the most part on protozoans and rotifers.
Video B: The same features mentioned above can be viewed here, however the movement of the feeding brushes is easier to see.
c. Fly Larva Blaesoxipha
Larvae of this species live exclusively in the fluid filled cup of the pitcher plant Sarracenia purpurea. I have never found more than one specimen in a single cup. They float near the liquid surface feeding on insects (mainly ants) that fall into the pitcher plant before the ants sink to the bottom. In one study, it was determined that Blaesoxipha consumed up to 50% of the insects that fell into pitcher plants. The larval head is incomplete. Note the black mandibles in the photograph and videos. They move parallel to one another as the animal feeds. Blaesoxipha floats, head down, with the deep, posterior, spiracular cavity extending slightly above the surface of the liquid. Two orange, raised ,spiracles lie within this cavity. Air is moved through the spiracles into two large tracheal tubes. The large white tubes, branch into smaller tubes (Visible) that deliver air, containing needed oxygen, to larval tissues. Larvae eventually crawl out of the pitcher plants and pupate on the bog surface.
Bacteria present in the water filled pitcher plant cup form the base of the food chain. They, as mentioned above, are mainly consumed by filter feeding protozoans and rotifers. Mosquito larvae (Top Predator) in turn use their mouth brushes to remove protozoans and rotifers from the water column. Chironomid larvae on the other hand feed on decomposing insects at the bottom of the cup. Finally, the predator Blaesoxipha feeds on dead insects near the water surface as they hang upside down in the water column.
d. Phylum Rotifera
Rotifers are multicellular organisms that can be found in many freshwater and marine habitats. They are temporarily attached to the substratum by a thin foot and two terminal toes. The toes secrete a mucus-like substance that holds them in place. The foot widens into the body (Trunk) proper (Visible) that houses most of the organs. A ciliated bi-lobed disc (Visible) is attached to the body. Disc cilia move the unattached animal through the water column, however, when the animal is attached, the cilia create water movement that brings food (small organisms such as bacteria) into the mouth. Rotifers living inside pitcher plants are filter feeders, consuming bacteria for the most part.Food passes into a muscular bulb called the mastax or pharynx. In most cases the mastax beats (contracts) constantly. The mastax grinds up food and from here it passes into the orange/Brown stomach where digestion takes place. A short intestine follows and empties to the outside through a terminal anus. A clear, round circle (Bladder) can be seen at the end of the trunk near the anal opening. It contracts periodically passing urinary waste to the outside.
Note the finger shaped sensory extension from the head