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:

• UBC STAIR Grant (2020)
• NSERC Discovery Grant (2020) "Gas exchange in water and air: Revealing fundamental mechanisms underlying the development and control of the insect respiratory system"
• NSERC Discovery Grant Accelerator (2020)
• CFI JELF (2015)
• NSERC Discovery Grants (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)

Current and past projects are outlined below.

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

To control their position in the water column, some aquatic animals have evolved the ability to actively regulate their buoyancy. However, only two groups of animals do so using compressible gas-filled sacs within their body: Teleost fish and the aquatic larvae of Chaoborid midges. While the mechanism that fish use to inflate and deflate their swim-bladder is well established, the mechanism Chaoborus larvae use to control the volume of four internal air-filled sacs has remained elusive. We are using a range of techniques to discover how these air-sacs change their volume, including immunohistochemistry in collaboration with Martin Tresguerres (Scripps Institution of Oceanography USD), transcriptomics with Ben Matthews (Zoology, UBC), and electrochemistry with Dan Bizzotto (Chemistry, UBC)

Students: Evan McKenzie, Tahnee Ames

Funding: NSERC Discovery + NSERC Accelerator

STAIR Grant UBC

Xylem sap is the dilute watery sap that flows from a plant's roots up to its leaves. It contains little sugar and traces of amino acids. As it is being pulled from the soil into the leaves, this sap exists under tension (i.e., negative pressure) As xylem tensions routinely exceed 0.7-1 MPa, it takes an even greater tension to be able to draw this liquid out. Feeding on this sap seems an unlikely choice, yet within the true bugs, several groups are adapted to feed on xylem sap exclusively. To do so, they rely on an enormous muscular pump in their head: the cibarium. Using a range of approaches, including microCT scans, muscle histology, and respirometry, we are quantifying the suction capacity of these incredible biological pumps, as well as the metabolic cost of this unusual feeding strategy. You can see 3D renderings of the cibarial pump here

Students: Elisabeth Bergman

Funding: NSERC Discovery + NSERC Accelerator

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.

Using prototype PCO2 optodes in collaboration with PreSens GmbH, we are currently investigating the role of internal PO2 and PCO2 thresholds in initiating and sustaining discontinuous gas exchange patterns in the Madagascar hissing cockroach.

Students: Raman Ubhi, Tormod Rowe

Funding: CFI JELF, NSERC USRA

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

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