Water Balance in Terrestrial Animals and Traits That Promote or Prevent Desiccation by vitor leite

Weight loss vs Organism

inesmorgadoo8 — 2025-05-21 10:45:53 UTC

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).

Maria Lamego A103870

maria04mane — 2025-05-21 10:51:08 UTC

Sofia Morgado A104394

maria04mane — 2025-05-21 10:51:27 UTC

Vitor Leite A104480

maria04mane — 2025-05-21 10:51:41 UTC

Snail

vitormsleite1960 — 2025-05-21 10:55:29 UTC

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).

Earthworm

inesmorgadoo8 — 2025-05-21 10:57:31 UTC

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

Slug

inesmorgadoo8 — 2025-05-21 10:59:17 UTC

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).

Beetle

vitormsleite1960 — 2025-05-21 11:00:16 UTC

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).

vitormsleite1960 — 2025-05-21 11:22:59 UTC

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

vitormsleite1960 — 2025-05-21 11:25:09 UTC

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

vitormsleite1960 — 2025-05-21 11:28:09 UTC

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.

Physiological traits

vitormsleite1960 — 2025-05-21 11:36:40 UTC

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).

The issue

maria04mane — 2025-05-21 11:37:55 UTC

Which terrestrial animals lose the most water?

Why animals lose different amounts of watert?

Procedures

vitormsleite1960 — 2025-05-27 14:21:17 UTC

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

Jars with lids, closed system
Jars without lids (with mesh), open system

vitormsleite1960 — 2025-05-27 15:01:46 UTC

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.

Discussion of results

vitormsleite1960 — 2025-05-27 16:19:32 UTC

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)

Aim of the study

maria04mane — 2025-05-28 10:34:01 UTC

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

Data Analysis

inesmorgadoo8 — 2025-05-28 10:43:17 UTC

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.

References

inesmorgadoo8 — 2025-05-28 11:16:42 UTC

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.