Living In Ticks

<em>Ixodiphagus hookeri</em>

Top: Adult Ixodiphagus hookeri
Bottom: Ixodes tick with emerged wasps. The black box marks the exit hole chewed by the wasps
Image From: Plantard and Colleagues

Over half of all species of Hymenoptera are parasitoids. Host for Hymenopteran parasitoids are not exclusively insects. Some parasitize and develop on spiders and ticks. Ixodiphagus hookeri is an encyrtid wasp that uses Ixodes Spp. as hosts. Female wasps lay numerous eggs inside a tick. These develop on the tick tissues, eventually killing their host. The wasps pupate and emerge inside the tick. The adult wasps chew a hole in the tick cuticle to escape.

Ixodiphagus hookeri has attracted interest because the hosts are vectors of Lyme disease. Attempts to reduce natural populations of Ixodes ticks by rearing and releasing Ixodiphagus hookeri have not been successful to date.

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More Olympus Bioscapes

Tochanters

Tochanters of Green coneheaded planthopper
Photo: Igor Siwanowicz

Ninth place in the 2014 OlympusBioscapes contest was won by Dr Igor Siwanowicz. This sharp image of a compelling complex structure has pleasing colors. What is it?

The image shows the trochanters of an immature green coneheaded planthopper, Acanalonia conica as viewed with a confocal microscope. My previous posts discussed structural coupling of opposite wings in flies. The green coneheaded planthopper uses this structure to couple movement of its jumping legs. The planthopper has a catch mechanism that allows force to be loaded onto the leg joint by slow muscle contractions.  The force on the joint is released suddenly to move the jumping leg with both force and power. In the planthopper, the cog-like gears coordinate the movement of the jumping legs on opposite sides of the body.  The cogs ensure that the force  on both jumping leg joints is released simultaneously so the legs move in unison. The green coneheaded planthopper is the first documented use of gear structures in nature.

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Clutch Flight Maneuvers

European Robber Fly

European Robber Fly

As I discussed in the previous post, the forewings and halteres of flies are coupled by structures that keep the beating in rhythm. This is efficient for flying in a straight line, but not for maneuvers. During maneuvers, flies will beat one wing with a lower amplitude or briefly stop moving it. This turns the fly like a boat that is paddled only on one side. If the wings are coupled, how can they move at different speeds?

Deora and colleagues* describe a model in which the movement of a wing can be coupled and decoupled from the vibration of the thorax similar to the way that a clutch engages and disengages an automobile engine from the drive train. Part of the wing called the radial stop can contact the pleural wing process (a sclerite that vibrates with the thorax) in four discrete conformations. In  “Position 0″, the radial stop is moved posterior to the pleural wing process, the wing is decoupled from the movement of the thorax and the wing is at rest even when the thorax vibrates. In Position 3, the wing base is moved anteriorly so the radial stop is fully engaged with the pleural wing process and beats at maximum amplitude.

There are two positions between 0 and 3.  The pleural wing process contains two grooves that the radial stop may contact. Engaging the radial stop with either of these grooves connects the wing to the vibration of the thorax but the wing beat amplitude is less than maximal. Thus, a fly can fully engage both wings by moving the radial stop to position 3; the radial stop can be shifted posteriorly to position 2 or 1 and beat with lower amplitude than the opposite wing or the radial stop can be shifted to the extreme posterior position, disengage and stop movement.  This gear mechanism provides the basic structure that allows a fly to perform elegant maneuvers.

*Tanvi Deora, Amit Kumar Singh, and Sanjay P. Sane. Biomechanical basis of wing and haltere coordination in flies. PNAS February 3, 2015. 112, no. 5 pp. 1481–1486.
http://www.pnas.org/cgi/doi/10.1073/pnas.1412279112

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Fly Flight Coordination

Hover Fly

Hover Fly, Heliophilus fasciatus

Flies have forewings that are membranous and hind wings, called halteres,a that are shaped like balls on the end of a stalk. In a previous series of posts, I discussed the role of the halteres in providing feedback information to the fly. Flies typically beat the forewings and the halteres at the same frequency. However, in most flies, the wings and the halteres beat in anti-phase rather than in phase. A group of scientists* investigated the mechanism of wing coupling. Using  freshly killed flies, moving the wing on one side with forceps casued the opposite wing to move in phase and the halteres to move in antiphase.  This is clear evidence of mechanical coupling.  In the dead flies, the nervous system was inoperable ruling out a nervous system mechanism of coordination.

The movements of the forewings are coupled by the up and down movements of the thorax. The vibrations of the thorax are transmitted to wings causing them to beat in phase. The muscles that move the forewings and muscles that move the halteres are separate muscles that are not necessarily coupled. The scientists discovered a ridge of cuticle that coupled the right forewing with the right haltere and the left forewing with the left haltere. Surgically severing the ridge allowed the movements of the forewing and haltere to uncouple. If the linkage on only the right side was severed, only the right wing and right haltere uncouple; the left wing and left haltere remain in antiphase. The tight mechanical coupling of the wings and halteres is important to their flight dynamics.

*Tanvi Deora, Amit Kumar Singh, and Sanjay P. Sane. Biomechanical basis of wing and haltere coordination in flies. PNAS February 3, 2015. 112, no. 5 pp. 1481–1486.
http://www.pnas.org/cgi/doi/10.1073/pnas.1412279112

Posted in behavior, by jjneal, Environment, Taxonomy | 1 Comment

Composting With Black Soldier Flies

Black Soldier Fly Larvae

Black Soldier Fly Larvae
Photo: Dennis Kress

The black soldier fly, Hermetia illucens, is commonly found in animal waste and compost. This insect is of interest both for waste management and for conversion of waste into nutients and animal feed. Black soldier fly larvae purge their gut, sterilize it with gut secretions and leave the waste to pupate. Migrating larvae that are relatively disease free can be collected. A group of European scientists monitored a black soldier fly bioreactor containing compost.* They found a 55% reduction in material and 11.8 % coversion of solids to biomass. The compost had higher N and P concentration after treatment with the soldier flies. The soldier flies also significantly reduced Salmonella in the final waste product. Manipulation of insects has potential for managing the waste from livestock production.

*Cecilia H. Lalander; Jørgen Fidjeland; Stefan Diener; Sara Eriksson & Björn Vinnerås. 2015. High waste-to-biomass conversion and efficient Salmonella spp. reduction using black soldier fly for waste recycling. Agron. Sustain. Dev. 35:261–271
DOI 10.1007/s13593-014-0235-4

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Living With Hog Waste

fly

Fly

Confined animal production is an efficient way to produce meat, but creates a number of problems, one being the large amount of manure. Composting is one method of waste handling that allows its use as fertilizer. Hog manure can difficult to compost due to the high moisture level. In China, dry ingredients (bulking agents) are typically added to hog manure to reduce the water content from 75% to 60% or below. Bulking agents can be costly and dilute the fertilizer value of the resulting compost.  House flies will lay their eggs and develop in manure. A group of Chinese scientists asked, “Can house fly maggots be used to quickly reduce the water content of pig manure to facilitate composting?”*

The scientists innoculated a 7 cm thick layer of pig manure with a series of maggot concentrations and found a concentration that optimized drying times and production of maggots. Suitable concentrations of maggots could dry the manure in 6 days or less. Using maggots to compost manure could create an unwanted problem: adult flies. Therefore they collected maggots from the manure by repeatedly skimming a thin layer at the top. Maggots respond by tunneling down into the manure so that eventually the manure is removed and only the maggots remain. The maggots were collected and killed by microwave. Analysis of the maggots determined that the protein concentration was high enough and the heavy metals concentrations low enough to meet the standards for commercial fish food.

Their process could improve the ability to compost manure and at the same time contribute to the protein production that will be needed to feed the expanding human population. The resulting compost has a better fertilizer value (NPK) that compost from manure treated with bulking agents. New and creative uses of insects can help address some of our technical challenges.

*Feng-Xiang Zhu, Yan-Lai Yao, Su-Juan Wang, Rong-Guang Du, Wei-Ping Wang, Xiao-Yang Chen, Chun-Lai Hong, Bing Qi, Zhi-Yong Xue & Hong-Quan Yang. 2015. Housefly maggot-treated composting as sustainable option for pig manure management. Waste Management. 35: 62–67.

Posted in Biomaterials, by jjneal, Environment, Food | Leave a comment

Tiny Reproductive Systems

Featherwing Beetle

Featherwing Beetle showing elytra (E) and feather wings (FW).
Image: Dybas & Dybas*

Insect success can be measured in the number and survival of the progeny produced. Tiny insects have tiny abdomens and little room to devote to reproduction. A space saving arrangement in some featherwing beetles (Ptiliidae) is a reduction in the reproductive system from two to one gonads in both the male and female.

Eggs and sperm must be a minimum size to function and in tiny insects, they may be disproportionately larger in relation to the adult than in larger relatives. In tiny featherwing beetles (Bambara spp) the small eggs are so large that a female can only accommodate one mature egg at a time.* In order for the sperm to function, they are longer than the insect itself.  The minimum size for viable egg and sperm may constrain further miniaturization in this group of beetles

*Dybas LK, Dybas HS. 1987. Ultrastructure of mature spermatozoa of a minute featherwing beetle from Sri Lanka (Coleoptera, Ptiliidae: Bambara). J. Morphol. 191:63–76

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