Matthews Lab

Comparative Respiratory Physiology

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The Matthews Lab receives generous funding from NSERC, and was awarded a research infrastructure grant from the Canadian Foundation for Innovation's John R. Evans Leaders Fund to establish a facility for the study of insect respiratory adaptation.

 

Grants Received:

 

  • NSERC Discovery Grant (2014) "From water breathing nymphs to air-breathing adults: Insects as a model system to investigate the physiological challenges associated with the transition of life from water to land"
  • NSERC Discovery Grant Accelerator (2014)
  • CFI JELF (2015)

 

Current projects are outlined below.

Darner nymph exuviae (Aeshna sp.)

Respiratory physiology of developmentally amphibious insects

Our current understanding of the respiratory challenges associated with moving between water and air comes from studying how aquatic animals, particularly vertebrates, have adapted their morphology and physiology to function on land. From this perspective, water-breathing is the ancestral condition and air-breathing is a derived state. The insects, however, have performed this feat in reverse, adapting their terrestrial air-breathing physiology to function in water.

 

Although all adult insects are air-breathers, representatives of nine insect orders have evolved to be developmentally amphibious, spending the juvenile portion of their life cycle as aquatic nymphs or larvae that possess gills and breathe water. These insect groups provide an exceptional opportunity to examine the evolution of adaptations associated with aquatic respiration, and to determine whether environmental constraints have caused gill-bearing insects to converge on a respiratory physiology comparable to other aquatic animals, or whether the phylogenetic constraints of their terrestrial ancestry have resulted in a respiratory physiology similar to air-breathing animals.

 

We are currently examining the respiratory physiology of dragonflies. While their ancestors were fully terrestrial, nearly 300-million years ago they adopted a developmentally amphibious life-cycle: their nymphs are fully aquatic, breathing water using a rectal gill, while the winged adults are aerial predators that breathe air through their spiracles. The physiological consequences of this transition between water and air are being explored.

 

Students: Daniel Lee

Funding: NSERC Discovery + NSERC Accelerator

Aquatic dragonfly nymph (Aeshna sp.)

Implantable fluorescent sensors for O2 measurement

~50 um-diameter silicone beads produced using microfluidics

Much of the difficulty associated with advancing the field of insect physiology is that of scale: how to measure, non-destructively, the internal environment of an insect. Even comparatively small diameter (140 µm) fiber-optic probes can be implanted only in the larger insect species, and require the insect to be artificially restrained or sedated during measurement. To overcome these problems, our lab is developing microscopic implantable sensors based on the principle of quenched fluorescence. The sensor itself is a silicone elastomer bead which contains a fluorescent probe. The beads are produced using a co-flow microfluidic chip. A video of the chip can be seen here.

 

These Fluorescent Implantable Elastomer Tags (FIETs) will be implanted into small semi-transparent organisms. The fluorescent signal from the FIETs will be read out non-invasively using a fluorescent microscope.

 

Students: Anna Robertson

Funding: CFI JELF

Discontinuous breathing patterns in cockroaches

Insects display a range of gas exchange patterns, from the continuous release of CO2 and uptake of O2, through to regular periods of breath-holding interspersed with bouts of ventilation: the so-called discontinuous gas-exchange cycle or DGC. DGCs are found among many different orders of insect, but the mechanisms that underly its occurrence, and its possible adaptive value, remain controversial.

One explanation for the emergence of this breathing pattern is its association with inactive resting or 'sleep-like' states. To investigate this further we are examining the relationship between breathing patterns, activity and arousal level in cockroaches.

 

Students: Raman Ubhi

Funding: CFI JELF, NSERC USRA

Nauphoeta cinerea cockroaches photographed while breathing continuously (top) and discontinuously (bottom)

Hot flowers: thermogenic waterlilies

A side project in the lab is looking at the thermogenic flowers of Victoria waterlilies. These flowers bloom at sunset and are able to generate sufficient heat to warm themselves up. This allows them to produce a warm internal environment that is ideal for poikilothermic beetle pollinators, as well as volatilizing the flower's perfume, which rises out of the flower in a plume of warm air.

 

The metabolic cost of generating this heat, as well as how the flower regulates its metabolic rate to control its temperature, is being investigated with the University of Stellenbosch Botanical Gardens. Time-lapse videos of these flowers opening over their two-night flowering cycle can be seen here

Victoria cruziana flower in cross-section showing the large floral chamber. The flower can increase the temperature in this chamber by up to 10 °C above the temperature of the ambient air

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