Week Eleven: Chigger Mite

Common Name: Chigger Mite

Scientific Name: Leptotrombidium sp.

Not-So-Fun Fact: Chigger mites transmit scrub typhus, which is also referred to colloquially as tsutsugamushi fever and scientifically as Orientia tsutsugamushi. Symptoms of scrub typhus begin as influenza-like but eventually cause fatal damage to the cardiovascular system, the lungs, and the kidneys if left untreated.

Domain: Eukaryota

Kingdom: Animalia

Phylum: Arthropoda

Class: Arachnida

Order: Acari

Family: Trombiculidae

Genus: Leptotrombidium

Description: The chigger mite is an ovoid arachnid so small that its sharp mouth cannot penetrate the skin far enough to suck directly from a blood vessel (for the actual mode of feeding, see Nutrition). This is a quite different organism from its harmless though irritating cousin the harvest mite, which in the United States is often referred to as a chigger.

Environment: Chigger mites inhabit low, damp grass and woodland areas in Asia, Australia, and the surrounding island archipelagos. During World War II, soldiers fighting in these areas were extremely susceptible to scrub typhus because their clothes were impossible to fully seal against the depredations of the mites and because of the necessity of marching through fields of tall kunai grass, a favorite haunt of the chigger mite.

Reproduction & Development: Chigger mites reproduce sexually and lay eggs. The larva of the chigger mite ingests one blood meal in its short childhood before molting and becoming an adult. The reason the chigger larva is able to pass on scrub typhus while only feeding once is that chiggers are capable of a process called “transovarial transmission.” In this process, the adult female becomes infected with the disease and passes it on to her unborn offspring, producing larvae born infected with scrub typhus.

Nutrition: The chigger mite’s single blood meal is made through a tiny feeding tube, which pokes minutely through the skin, liquefies the surrounding tissue, and sucks up this mixture of blood and fluid flesh. The irritation around a chigger bite comes mainly from its sloppy habit of leaving behind the feeding tube. The adult feeds entirely on plants and causes no harm to any animal except through its potentially diseased progeny.

 

Week Ten: West Nile Virus

Common Name: West Nile Virus

Scientific Name: Flavivirus, West Nile Virus type

Not-So-Fun Fact: There is no current vaccine to protect the public against West Nile virus, though scientists are hoping that they will soon be able to create one.

Taxonomy: It is contested among the scientific community exactly how viruses should be classified, because many scientists do not consider them to be proper organisms. Below is the taxonomic classification after the general grouping of Virus:

Class: Class 4 ssRNA positive-sense viruses

Order: The family flaviviridae has not been assigned to a specific order yet.

Family: Flaviviridae

Genus: Flavivirus

Environment: West Nile Virus is carried by mosquitoes, and other hosts susceptible to the virus include humans and various birds. This virus is prevalent in Africa, the Middle East, parts of Asia, and since 1999, in the continental United States.

Description: The Center for Disease Control and Prevention estimates that seventy to eighty percent of people infected with West Nile Virus never experience symptoms. Those who do are divided into two groups based on the severity of their illness. Twenty percent of those infected experience this milder but still temporarily debilitating set, which includes aching of the head and body, joint pain, vomiting, diarrhea, and a rash. The general weakness or malaise of this type can last for weeks or even months after the initial onset of disease, though these victims are far more fortunate than the severe cases. This latter group can develop the swelling and inflammation of the brain and spinal tissues known as encephalitis and meningitis.

Reproduction & Development: West Nile Virus is spread between humans, other mammals, and birds only via the bite of a mosquito. Once inside its host, it spreads between cells, invading each and copying itself using cellular material until it bursts out and spreads again throughout the body. If another mosquito feeds on the host, it may contract the infection itself and continue to spread the parasite.

Nutrition: West Nile Virus is a parasite. It attacks its host cells and steals nutrients and water to survive, in the process severely damaging or in rare cases even killing the host.

 

Week Nine: Lily (Not Me)

Common Name: Easter Lily, Bermuda Lily

Scientific Name: Lilium longiflorum

Not-So-Fun Fact: Yes, even my namesake can be poisonous. All parts of the lily plant are highly poisonous to cats. Symptoms are experienced over twenty-four to forty-eight hours and slide from kidney failure to death.

Domain: Eukaryota

Kingdom: Plantae

Phylum: Magnoliophyta

Class: Liliopsida

Order: Liliiales

Family: Liliaceae

Genus: Lilium

Species: L. longiflorum

Taxonomical note: Most cultivated Easter lilies are the variant called “Nellie White” and are named after the wife of the grower who bred them.

Description: The most striking feature of the Easter lily is its large, white, trumpet-shaped flowers, which feature bright yellow anthers. In Christianity, the lily is often used as a symbol for Mary, mother of Jesus, and lilies are often used as symbols of purity and happiness.

Environment: Easter lilies are native to Japan, specifically the Ryukyu islands at the southern end of the great archipelago. In 1819, the species was introduced to the British Isles, and in 1853 it was introduced to the island of Bermuda. Lilies thrive best in habitats with nutrient-rich soil and mild temperatures year-round.

Reproduction & Development: Lilies are angiosperms, or flowering plants. They grow from bulbs and naturally bloom in summer, although many plants are artificially forced to bloom in spring using greenhouse temperature and artificial lighting. To bloom, bulbs require a thousand hours’ worth of exposure to cold, damp air. Lilies reproduce sexually through the classic model of pollination, though they may also sprout as bulblets on the subterraneous stems of their parent plants.

Nutrition: The University of Vermont recommends bright but indirect sunlight on Easter lilies, and warns the readers of its article on the subject not to overly water their plants; watering when the soil feels dry is recommended. Lilies take in water and nutrients through their roots in the soil and perform photosynthesis in their broad, dark green leaves.

Week Eight: Dwarf Mistletoe

Common Name: Dwarf Mistletoe

Scientific Name: Arceuthobium sp.

Fun Fact: Dwarf mistletoe fruits each contain a single bullet-shaped seed. As the fruit grows, tension tightens on the seed and eventually it flies outward, shooting toward a new host at up to 56 miles per hour. The dwarf mistletoe embryo, it can be said, is a feisty youth.

Domain: Eukaryota

Kingdom: Plantae

Phylum: Magnoliophyta

Class: Magnoliopsida

Order: Santalales

Family: Viscaceae

Genus: Arceuthobium

Description: Dwarf mistletoe is a different genus than its better-known and also parasitic relative. The plant itself is as small yellow structure that latches onto the branches of conifer trees, its natural host. Almost all species of conifer tree are vulnerable to infection except for cedar and juniper, which can be colonised by the dwarf’s relative, true mistletoe. Signs of infection in host trees include swelling of the bark, the visible yellow shoots, and branch growth said to be shaped like a “witch’s broom.” Eventually, the host tree will begin to die from the top down until branches, trunk, and roots all are dry husks.

Environment: Dwarf mistletoe is found in conifer forests in all of southern Canada, Alaska, the western United States from Texas to Washington State, and the northern states from Maine to Minnesota and down to Pennsylvania.

Reproduction & Development:  In accordance with the Fun Fact, dwarf mistletoe produces fruits containing small, sticky projectile seeds capable of flying 56 miles per hour and landing 50 feet from their original position. Once on a new host tree, the plant establishes itself as a parasite (see Nutrition) and is visible within two to four years of infecting the tree. After one to two more years, the plant is sexually mature and begins to fruit.

Nutrition: Dwarf mistletoe has little to no chlorophyll of its own, and therefore cannot perform photosynthesis to a degree sufficient to feed itself. This is why it is forced to parasitize conifers. The plant injects parasitic roots called “hautoria” into the branches of its host. These structures leech nutrients from the vascular tissue of the host tree until the tree dies.