Eggs Adhere in and Out of Water

a light brown spotted toad stands on dry grass with small, spherical white eggs attached to his back and back legs

Biological Strategy

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Attach Temporarily

Living systems must sometimes, temporarily, stay in one place, climb or otherwise move around, or hold things together. This entails attaching temporarily with the ability to release, which minimizes energy and material use. Some living systems repeatedly attach, detach, and reattach for an extended time, such as over their lifetimes. Despite being temporary, these attachments must withstand physical and other forces until they have achieved their purpose. Therefore, living systems have adapted attachment mechanisms optimized for the amount of time or number of times they must be used. An example is the gecko, which climbs walls by attaching its toes for less than a second. Other examples include insects that attach their eggs to a leaf until they hatch, and insects whose wings temporarily attach during flight but separate after landing.

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Amphibians

Class Amphibia (“to live a double life”): Frogs, salamanders, toads

Amphibians live a “double life” by being able to survive both on land and in water. Unlike reptiles with dry, scaly skin, amphibians have smooth skin that needs to be kept moist. Many live in the water through development and start life with gills, and then transition to breathing with lungs. They can get even more oxygen through cutaneous respiration, or breathing through their skin. This class represents the first animal group to be able to efficiently walk on land—aided by the well-defined limbs that gave them a “leg up” on their finned competitors.

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The eggs of the midwife toad stick to the male toad's legs in and out of water via sticky egg strings.

“After the pair lays and fertilizes strings of twenty to sixty eggs, the father thrusts his legs through the egg mass. The sticky egg strings adhere to him, and he stumbles around for the next few weeks with the eggs entwined around his thighs and waist. Periodically he dips into shallow water, ensuring the eggs don’t shrivel up and die. When the tadpoles are nearly ready to hatch, they flip about in their egg capsules. The wriggling of the twenty to sixty embryos likely tickles the male’s body and stimulates him to hop to a pond.” (Crump 2005:53)

Crump, M. 2005. Headless Males Make Great Lovers & Other Unusual Natural Histories. University of Chicago Press, Chicago, IL. 199 pp.

Last Updated August 18, 2016

References

Book

Headless Males Make Great Lovers: And Other Unusual Natural Histories

University of Chicago Press | 01/05/2007 | Marty Crump

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