Allergic Reaction To Mosquito Bite
Congress can not agree on a budget but they did agree on a continuing resolution that contains funds for Zika. 8 months after the Obama administration requested $1.9 billion in emergency funds, Congress delivered $1.1 billion. During the interim, there have been 23,000 Zika cases confirmed in the US and its territories. The majority of cases are from Puerto Rico but over 3000 are from the 50 states. Those infections have resulted in 21 cases of microcephaly and infant deaths due to Zika.
To address the crisis, the Obama administration cannibalized other spending where it could, including Ebola vaccine research. The loss of funding will delay Ebola vaccine development. The $1.1 billion can be spent in the next fiscal year but some of the money will be needed to repay funds cannibalized from elsewhere. The emergency funds were supposed to be for the 2016-7 fiscal year. Congress missed that funding period entirely, and the $1.1 billion is still inadequate for the scope of the problem.
The fallout from Zika birth defects will be expensive, creating new health care demands in the future and is devastating for the effected families. The US was equally slow in response to the HIV/AIDS epidemic in the 1980s. Too many politicians don’t recognize the importance of public health. Yes, the request for Zika is a large sum of money. In the long run, it pales in comparison to the costs of doing nothing.
Gynandromorph Tiger Swallowtail exhibits male color pattern on left and female color on right.
Photo: James K Adams http://www.livescience.com
In butterflies, color and color patterns are essential for mate recognition and are used in defenses such as crypsis, warning coloration, disruption of visual tracking and mimicry. In the Eastern Tiger Swallowtail, Papilio glaucus, males and females exhibit drastically different color patterns, with the female mimicking the unpalatable Pipeline Swallowtail. In a close relative, Canadian Tiger Swallowtail, Papilio canadensis both the male and female display a color pattern similar to the Eastern Tiger Swallowtail male.
Wing color is under genetic control. In some point in its evolution, the female Eastern Tiger Swallowtails changed their color pattern from yellow to black. How did this happen? The black color of swallowtail wings is due to melanin, the most common type of pigment in insects. Females but not males produce melanin in the areas of the wing that in the males are yellow. Males do not produce melanin in these areas. The melanin production is controlled both by genes for proteins active in melanin synthesis and genes that suppress the melanin synthesis pathway. These genes are linked to the sex determining chromosome which is why only the females have the black coloration. These genes are present in Papilio glaucus but not Papilio canadensis and are the reason why P. glaucus, but not P. canadensis has black females.
Affect of gene suppression on Oncepeltus coloration
Image: Liu & Colleagues*
In insects, RNAi (RNA interference) is a useful technique to suppress genes and a powerful tool for understanding the function and interaction of genes. Liu & Colleagues* used RNAi to dissect genes important in creating color patterns in the large milkweed bug, Oncopeltus fasciatus. They studied four genes, ebony, black, aaNAT, tan and yellow. Ebony and black are genes that suppress the production of melanin. As shown in the figure (left) knocking out the ebony gene or the black gene with injected RNAi created an unusual color pattern. Areas of the wings and body that are typically yellow or orange become black because of the increase in melanin production. RNAi analysis demonstrates that Oncopetus color pattern is the result of expressing or repressing genes that control the amount of melanin production.
The form and color of an insect are not only the result of the presence or absence of genes but also the timing a pattern of when and where they are expressed.
*Jin Liu, Thomas R. Lemonds, James H. Marden, Aleksandar Popadić. A Pathway Analysis of Melanin Patterning in a Hemimetabolous Insect. GENETICS May 1, 2016 vol. 203 no. 1 403-413;.
The Zika Virus is an example of an invasive species. Originally from Africa, it has now spread around the globe to every continent but Antarctica and hundreds of remote islands. The Zika Virus depends on a mosquito, Aedes aegypti,
for most of its transmission.
Aedes aegypti is also an invasive species. A native of Sub-Saharan Africa, Aedes aegypti began a long association with humans when humans first moved into the African forests. Aedes aegypti was able to find suitable hosts (humans) and nearby habitat in the water collected by people. Aedes aegypti adapted to the urban environment and has lived in close association with humans since then. As trade from Europe increased, Aedes aegypti spread as larvae swimming in the casks of water brought on board the ships. Aedes aegypti had colonized much of the world by the 17th century.
Successful invasive species can pave the way for other species that depend on them. Without the spread of the mosquito, viruses such as Zika and yellow fever could not themselves become invasive.
Francesco Redi was a poet and a physician, a learned man in 17th century Florence, Italy. He is considered by some to be the author of the “experimental control” and the author of parasitology. He had a particular interest in flies and studied the life cycle of the blow fly. Redi conducted experiments that showed that maggots were produced not from rotting meat, but by flies that laid eggs on the meat. This observation was a refutation of spontaneous generation and part of the emerging paradigm of learning through observation and experimentation rather than sole reliance on authorities such as Aristotle.
Based on his observations of blow flies, Redi hypothesized that plant galls and the gall flies that emerged from galls, originated from fly eggs. However, Redi was not able to observe gall flies laying eggs or adequately exclude them in his study of galls. This led him to conclude (erroneously) that galls were produced by plants by the same process that caused plants to produce flowers and fruits. Redi’s error was soon corrected by Vallisneri, who observed the eggs laid in the plants.
Today, Redi’s error is obvious, but in the 17th century, genes, DNA and plant hormones were all unknown and no good model of flower production had been proposed. Even today, the mechanisms behind gall creation (secretions of the fly induce gall formation) are vaguely understood and are the subject of intense investigation.
Silkworm, Bombyx mori
The silk produced by larvae of the silkworm, Bombyx mori, is a long thread composed of shorter interlocking strands of silk protein. Silk thread can be disassociated into its protein units, silk nanofibrils. These nanofibrils can be dissolved in solution and when appropriately filtered, will form a membrane of interlocking silk nanofibrils.
The membranes are useful for filtration applications They are free standing, do not dissolve in water or solvent and can be cut to a desired shape. The membranes contain nanopores from 4 to 20 nm. The thickness of the membrane can be varied by altering the conditions used to produce the membrane. Increasing the membrane thickness from 40 nm to 120 nm decreases the pore size. The membranes have water permeabilities similar to other filtration materials. Insect biomaterials such as silk are increasingly important in nanoscale materials applications.
Shengjie Ling, Kai Jin, David L. Kaplan, and Markus J. Bueller. Ultrathin Free-Standing Bombyx mori Silk Nanofibril Membranes. Nano Letters 2016 16 (6), 3795-3800
Left: Silkworm caterpillar, sham injected
Right: Silkworm caterpillar injected with bacteria
Photo: Ishii & Colleagues*
Caterpillars suffering from bacterial infections often stop moving and become lethargic. The paralytic proteins (cytokines) present in caterpillar hemolymph are involved. The same contractile paralysis that is initiated by paralytic proteins can be induced by injecting bacteria into the hemocoel of caterpillars. (Note the significant contraction in the photo) This has been demonstrated* by comparing injection of bacteria to injection of the paralytic protein. The bacteria trigger the activation of the paralytic protein which affects numerous organs and stimulates nitrous oxide release. Is the paralysis adaptive? The answer is unknown. Immobilization may slow the movement of pathogens and confine their location which may make them easier for the caterpillar immune system to eliminate them. Some pathogens are present on food and paralysis will stop a caterpillar from ingesting addition food that may be contaminated.
*Ishii, K., Hamamoto, H. and Sekimizu, K. (2015), PARALYTIC PEPTIDE: AN INSECT CYTOKINE THAT MEDIATES INNATE IMMUNITY. Arch. Insect Biochem. Physiol., 88: 18–30.