Gastropod attractants: Potential management tool for Giant African Land Snail Lissachatina fulica? RESEARCH UPDATE Rory McDonnell 1, Amy Roda 2 and Jocelyn.

 Gastropod attractants: Potential management tool for 

Giant African Land Snail Lissachatina fulica?

RESEARCH UPDATE

Rory McDonnell1, Amy Roda2 and Jocelyn Millar1

1: Department of Entomology, University of California, Riverside

2: CPHST, USDA-APHIS, Subtropical Horticultural Research Station, Miami

Background

Chemical cues play roles in feeding, prey detection, predator avoidance, alarm responses, species recognition & reproduction in gastropods

External attractants e.g. from food sources

Possible pheromones– Sex pheromones– Aggregation pheromones

Sex pheromones

Photo: Wikimedia Commons

• Spawning and breeding in mud snails organized by at least two kairomones and three pheromones

• Gland in the head produces a pheromone that elicits courtship and copulation

Ilyanassa obsoleta Euhadra peliompha

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Aggregation Pheromones

Lissachatina oriented towards odor of conspecifics

Source reported to be the pedal mucus gland

Attractant is a pheromone

Source: Chase (1978)

Why no further work to follow up?

Our Approach

1. Attractants produced by conspecifics Follow up on preliminary work by Chase from

1978, showing attraction of GAS to odors from conspecifics

2. Attractants from other sources

Identify and develop attractants from other sources (e.g., food)

1. Pheromones

Response of Lissachatina fulica to the odor of conspecifics

X2 = 24.69, P<0.001, n=20

78%

22%

Treatment ArmControl Arm

Aeration chamber for collecting odors from live snails

Odor analysis resultsLittle difference between snail and control aerations

One compound appeared consistently in snail odor collections

2-diethylaminoethanol

Response of Lissachatina fulica to a 0.01% solution of 2-diethlyaminoethanol

X2 = 6.14, P<0.05, n = 14

64%

14%

21%

Treatment ArmControl ArmNo Choice

2. Other attractants

Fed snails a variety of different foods

With one food item, noticed a distinct oriented mass movement towards the food

Much more pronounced than normal, clearly strong attraction to odors from the food

Attraction to food odors

• Pronounced oriented movement towards food source

Replicated bioassays• Two choice bioassay

• 1ml of treatment and 1ml control on filter paper

• Position of treatment and control switched after each replicate

• Snails tested individually to prevent trail-following

• Choice made when snail touched the Petri dish or after 45min

Treatment

Control

Response to steam distillate

70%

10%

20%

Steam distillateControl (water)No Choice

X2 = 6.07, P<0.05, n = 10

Statistically significant attraction

Result: Attractants are extractable and heat stable

Response to ether extract of steam distillate

X2 = 6.07, P<0.05, n = 10

Statistically significant attraction

70%

20%

10%

Ether extract

Control (ether)

No Choice

Result: Attractant extractable into organic solvent, easier to work with

Response to acid-treated steam distillate

X2 =6.00, P<0.05, n = 10

Statistically significant attraction

Result: Attractant cannot be amine or other organic base

67%

33%

Acid-treatedControl (water)No Choice

Response to base-treated steam distillate

X2 = 7.00, P<0.05, n = 10

Statistically significant attraction

Result: Attractant cannot be organic acid

83%

17%

Base-treated

Control (water)

No Choice

Response to neutralized ether extract of steam distillate

X2 = 20.20, P<0.001, n = 10

Statistically significant attraction

100%

Neutralised extractControl (ether)No Choice

Result: Attractant is one or more neutral compounds in the steam distillate

Response to methanol elution of steam distillate volatiles trapped on solid phase extraction cartridge

X2 = 8.32, P<0.05, n = 10

Statistically significant attraction

Result: Attractant is a moderately polar compound

75%

25%

Neutralised extract

Control

No Choice

Conclusion

The attractant is a heat-stable neutral compound(s) that is moderately polar

Some attraction to a partial reconstruction of the compounds in the neutrals fraction

Next steps!Pheromone:1. Continue to analyze the aeration extracts

2. Testing of pedal mucus gland

Next steps!

Food based attractant:

1. Analysis of the neutrals fraction from the steam distillate

2. Development of a fractionation scheme

3. Reconstruction of the volatiles blend for bioassays

Questions?

Acknowledgements: APHIS-PPQ-CPHST for funding to date