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Desiccation is one of the greatest challenges faced by terrestrial organisms (McCluney et al., 2017).

In closed systems, weight variation was less than 5%. One would expect that in a closed system there would be no variation; this is due to weighing errors.

In an open system, variations occurred because the water was able to escape from the system

The slug and the earthworm lost between 20% and 50% of their body weight in water.

The beetle and the snail were the species that lost the least amount of water.

Animals such as the snail and beetle are more resistant to desiccation, whereas the slug and earthworm are less resistant. This is due to the physiological make-up of these organisms (Willmer et al., 2004).

Terrestrial organisms exhibit the highest rates of transpiration, as they lose water more easily through evaporation (Willmer et al., 2004)

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Source: Photo provided by Andreia Abreu, taken during the class

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1- The organisms were transferred from the Petri dishes to the jars.

Jars with lids, closed system

Jars without lids (with mesh), open system

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Source: Photo provided by Andreia Abreu, taken during the class

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2-A mesh was placed on top of the jars to prevent the animals from escaping and to allow water to exit through the air.

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Which terrestrial animals lose the most water?

Why animals lose different amounts of watert?

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desenho para uma introdução do solo com os animais como minhoca, escaravelho, caracol

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https://imgur.com/upload.   Biology and Geology student, University of Minho

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Biology and Geology student, University of Minho

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Biology and Geology student, University of Minho

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Terrestrial snails possess physical protection such as a shell and an epiphragm, and during periods of drought, they have the ability to withdraw into their shells and enter dormancy(Slotsbo et al. 2011).

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Earthworms in soil are only partially hydrated and gain weight when transferred to pond water (W.Carley et al.1978).

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The moist permeable integument of terrestrial molluscs demands adaptations to avoid or cope with excessive dehydration. The most obvious water regulating behaviour of slugs is their preference for moist habitats (Prior et al. 1983; Prior 1985).

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Beetles stand out for their remarkable resistance, ability to conserve water, tolerance to dry and hot environments, efficient metabolism, and capacity to survive under adverse environmental conditions (Wilmer et al., 2004).

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Source: Photo provided by Andreia Abreu, taken during the class

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3- The initial weight (iw) of the jars with the animals was measured.

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Source: Photo provided by Andreia Abreu, taken during the class

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4- The organisms were exposed to a fan for 45 minutes to accelerate the desiccation process.

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Source: Photo provided by Andreia Abreu, taken during the class

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5- Following the procedure, the organisms were reweighed(fw) to allow comparison of weight differences due to water loss. The variation was obtain by pw-iw.

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The fact that the snail has an exoskeleton (shell) and the beetle has a chitinous covering coated with impermeable waxy layers explains why these organisms lose less water (Wilmer et al., 2004).

The earthworm and slug have bodies covered in mucus, making them more prone to desiccation (Wilmer et al., 2004).

Organisms with a body covering and impermeable structures are less susceptible to water loss (Chown, Sørensen & Terblanche, 2011).

Organisms with moist, unprotected body surfaces are more susceptible to water loss (Wilmer et al., 2004).

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McCluney, K. E., & Sabo, J. L. (2017). Animal water balance drives top-down effects in a riparian arthropod community. Ecology, 98(3), 681–693.

Ecology, 98(4), 1005–1015.

W.Carley (1978)

Slotsbo, S., Fisker, K. V., Hansen, L. M., & Holmstrup, M. (2011). Drought tolerance in eggs and juveniles of the Iberian slug, Arion lusitanicus. Journal of Comparative Physiology B, 181(8), 1001–1009.

Prior, D. J. (1985). Water-regulatory behavior in terrestrial gastropods. Biological Reviews, 60(4), 403–424.

Prior, D. J., Hume, M., Varga, D., & Hess, S. D. (1983). Physiological and behavioral aspects of water balance and respiratory function in the terrestrial slug, Limax maximus. Journal of Experimental Biology, 104, 111–127.

Chown, S. L., Sørensen, J. G., & Terblanche, J. S. (2011). Water loss in insects: an environmental change perspective. Journal of insect physiology, 57(8), 1070-1084.

Willmer, P., Stone, G., & Johnston, I. (2004)

Environmental physiology of animals (2ª ed.). Wiley-Blackwell.

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The aim of this study is to determine and compare among the 4 organisms which ones lose the most weight and why!

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The data obtained were processed in RStudio.

To compare the variation in water loss among the different animals and to determine where significant differences occurred, we performed an analysis of variance followed by a Tukey test.

A significance level of 0.05 was used for all analyses.

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Fig. 1: Different letters (a, b) indicate significant differences.

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There is a clear difference in weight loss among the various organisms: snail/beetle and slug/earthworm; within these groups, no significant differences were observed, as indicated by high p-values.

Group a comprises the snail and beetle, and group b includes the slug and earthworm.

The slug and earthworm lose more weight (water) than the snail and beetle.

p-value: 4.8 × 10⁻⁶, indicating significant differences in water loss between the organisms (p-value < 0.05).