Living With Glassworms

Glassworm

Glassworm
Photo: Viridiflavus

Glassworms or Phantom Midges are midge larvae in the Genus Chaoborus. This genus is distributed globally and is found in lakes. The larvae are predators that feed on small crustaceans and mosquito larvae. Glassworms capture prey with their prehensile antennae. Their transparency helps conceal them from their prey and from predatory fish.

Posted in by jjneal, Environment | 1 Comment

A Herculean Color Change

Hercules

Dynastes hercules
Photo: Didier Descouens

The Hercules beetle, Dynastes hercules, is able to change its color from a greenish yellow to black and back. How does this occur?

This color changes was investigated by H.E. Hinton and G.M. Jarman*. They discovered that the color was due to the way elytra reflected light. The elytra have a transparent hard top layer and a spongy layer underneath. When the spongy layer is filled with air, the elytra reflect the yellow color. If the spongy layer is filled with water, the light is absorbed and the elytra are black. This process can work on preserved museum specimens as well as live beetles.

Why is color change important? At night when it is moist, the beetle can avoid detection with its all black color. In the daytime when the elytra dry, the color reverts to greenish yellow which is less conspicuous than all black.

*Hinton, H. E. & Jarman, G. M. (1972). Physiological colour change in the Hercules beetle. Nature 238(5360), 160–161.

Posted in Biomaterials, by jjneal, Environment | 1 Comment

Questions About Zika?

Mosquito

Mosquito

The first case of Zika virus in humans was documented in 1960. For decades, Zika remained in obscurity until an outbreak on the island of Yap in 2007. Another epidemic occurred on French Polynesia in 2013, that reached Brazil in 2014.  In 2016 over 20 countries in the Americas have Zika transmission. What changed?

It is possible that the virus has mutated to a more virulent form.
The virus could have mutated to a form that has greater transmission.
The human population in the Americas may be more susceptible to the virus.
Answers to these questions could help predict the trajectory for Zika.

Does Zika cause microcephaly?
We don’t know. There is a spike in microcephaly in Brazil that coincides with the spread of the Zika virus. Zika has been found in amniotic fluid and in the brains of babies with microcephaly who have died. Both in the 2013-14 outbreak in French Polynesia and in the 2014-15 outbreak in Brazil increases in birth defects are noted. This correlation is worrisome, but correlation is not causation. It will take further research to determine causation.

Microcephaly is difficult to diagnose. In reviewing the 4000 cases of microcephaly in Brazil, 260 cases have been confirmed and 462 reclassified. Only 6 cases of microcephaly have been positively linked to Zika so far. We await further investigation that could confirm evidence in other cases. The absence of evidence is not evidence of absence.

Was the decision to declare a public health emergency warranted?
In assessing risk, the severity of outcome must be considered. The long term consequences of microcephaly are severe. The uncertainty about the effects of Zika are large. Thus, it is good policy to urge caution while intensifying the research into the important unanswered questions so we can make more informed policy decisions.

Posted in by jjneal, Health, News, Policy | 1 Comment

Living With Public Health

Mosquito Bite

Allergic Reaction To Mosquito Bite

In the late 1800s and early 1900s a powerful new paradigm, Public Health, made great strides in reducing diseases and increasing human longevity. Public health is a concerted effort to address disease by applying measures at the society level. In the US, we often think of health efforts at the individual patient-doctor level. Public health works at a societal level to prevent illness an effort which if successful, can produce far better outcomes.

During the period between 1900 and 1945, public health efforts to control diseases spread by mosquitoes eliminated both yellow fever epidemics and malaria from the US. Controlling the mosquitoes that spread a disease and isolating contagious individuals from mosquitoes are examples of public health solutions to diseases that could not be cured by doctors.

On February 1, 2016 the World Health Organization declared the Zika virus to be a “Public Health Emergency of International Concern”. What does this entail? The WHO lists the following priorities:

A coordinated international response is needed to improve surveillance, the detection of infections, congenital malformations, and neurological complications, to intensify the control of mosquito populations, and to expedite the development of diagnostic tests and vaccines to protect people at risk, especially during pregnancy.

Zika virus moved out of Africa to become an international problem. The most likely solutions will be intensive efforts to improve public health tools and activities.

Posted in by jjneal, Health, News, Pest Management | 1 Comment

Color Coordination

Familiar Bluet

Familiar Bluet rests on a leaf in Petobago, Michigan.

Damselflies use their vision to actively hunt prey and identify mates. The color is important for mate choice and intraspecific communication. Female Familiar Bluet damselflies, Enallagma civile, will change color from turquoise to brown during mating. What causes the color change?

The turquoise color is not a pigment but a structural color. The color is created by spherical granules packed into pigment cells just beneath the cuticle. The spheres contain structured arrays that reflect light relatively equally in all directions. Thus, the turquoise color is constant irrespective of viewing angle and not iridescent as in some structural colors.

Like the chameleon grasshopper, Kosciuscola tristis, the granules can be moved by microtubules. Movement of the granules away from the surface produces the brown color. It is interesting that two very different organisms evolved very similar color change mechanisms.

Posted in Biomaterials, by jjneal, Environment | 1 Comment

Promoting Mosquito Repellent

Mosquito

Mosquito

On a November 2015 trip to Africa, Pope Francis was asked if he was worried for his safety during an upcoming visit to Kenya. The journalist was referring to recent attacks that specifically targeted Christians. Pope Francis replied,

There are good and bad people. To tell you the truth, the only thing I’m worried about are mosquitoes. I hope you carried your mosquito repellents.

Indeed. With Malaria, Dengue, Zika, West Nile and other diseases carried by mosquitoes in Africa, using mosquito repellent is a wise choice.

Posted in by jjneal, Health, News | 1 Comment

Living With Horns

Hornworm

First Instar Tobacco Hornworm

Caterpillars in the family Sphingidae are noted for the horn on the abdomen. Like many other insect parts, the scale of the horn relative to the body size changes as the caterpillar develops.  In the first instar tobacco hornworm larva, the length of the horn is over 25% of the body length.  In a fully developed 5th instar caterpillar, the horn is less than 10% of the body length.  The shape and the color also change.  The first instar horn is thin and black,  The fifth instar horn is orange and thick at the abdomen and tapers at the tip.  There is much speculation about the function of the horn.  Presumably it is used in defense against parasitoids.

Posted in by jjneal, Development, Taxonomy | 1 Comment