Desiccation Resistance Mechanisms in the Desert Locust

and Desert BeetleApril Irums and Alexa Mogle

What is Desiccation?●

It is a process in which an organism experiences extreme loss of water and appears to be drying out or is dried out completely.

- Desert Locust

- Desert Beetle

http://www.pd4pic.com/cartoon-bugs-bug-insect-beetle-insects-scarab.html

Desiccation Resistance Mechanisms of the Schistocerca

gregaria

Water, Nutrient, and Behavioural Adaptations

http://blogs.bu.edu/bioaerial2012/2012/09/25/the-locust-swarm

Schistocerca gregariaThe desert Locust

(Showler, 1996)

Recession area

Invasion area

Epidermal Water Loss

Cuticular hydrocarbons (CHCs)• Waterproofing of

the epidermis

• Research suggests chemical functions

(Chung and Carroll, 2015)

Nutrient UptakeConcurrent Flows Water Movements and Nutrient Absorption in the Locust Midgut

(Dow, 1987)

Counter-current system• Used during extreme nutrient deprivation• Maximizes nutrient absorption• Use of amaranth dye

http://blogs.bu.edu/bioaerial2012/2012/09/25/the-locust-swarm

Nutrient UptakeAn Experiment

AbbreviationsCr: cropAC: anterior caecaPC: posterior caecaAM: anterior midgutMM: middle midgutPM: posterior midgut Il: IleumRe: rectum

(Dow, 1987)

Figure 1: Observed dye density of fluid from alimentary tracts of fed and starved Schistocerca gregaria.

Starved locusts

Fed locusts

Nutrient UptakeAn Experiment

Movement of ions, water and nutrients within the alimentary canal of the locust

a) Fed Locusts• Caeca supplied with

nutrient rich fluid • Solid and excess fluid

move along midgut

b) Starved Locusts• Fluid from Malpighian

tubules moves anterior• Digest nutrients into

caeca• Re-absorption

(Dow, 1987)

Behavioural ChangesLife Phases

Solitarius• Solitary• During times of low

nutrients, following drought• Slow moving • No Flight capabilities

Gregarious • Swarms• Follow influx of rain and

nutrients• Fast moving• Flight

("Locust handbook: 2. Desert Locust-Schistocerca gregaria: Life cycle", 2016)

Tenebrionid BeetlesThe Desert Beetle

-Arid Climate

-Annual rainfall of ~ 1.4 cm

-Several different species of desert beetle

http://www.in-the-desert.com/insects.html

Components of Water Loss

(Ahearn, 1970)

-Major components of water loss include faecal production, transpiration (evaporation) , and the release of Quinone droplets

Avenues of Water Loss Thorax

Figure 1: Areas of water loss in tenebrionid beetles.

Abdominal Region

Anus

(Ahearn, 1970)

Dehydration and Rehydration Experiment

Figure 2: The effects of dehydration and hydration on the % of original weight of Physadesmia globosa.

Allowed to Rehydrate

-Rapid weight loss in the absence of water (dehydration).

-Increase in weight in the presence of water (rehydration).

(Naidu, 2001)

Dehydration and Rehydration Experiment

Figure 3: Lipid content showed a strong negative correlation.

Figure 4: Haemolymph volume declined.

(Naidu, 2001)

Desiccation Resistance1. Spiracles remain Closed

2. Discontinuous Gas Exchange

3. Fog-Basking Behaviour

(Zachariassen, 1996)

Desiccation Resistance Mechanisms of Tenebrionid Beetles

Fog Basking behaviour

(Zachariassen, 1996)

SignificanceUnderstanding desiccation resistance mechanisms:

• Strategies for population control

• Modulate species invasions

• Fog-basking design in Tenebrionid beetles

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