Why pygmy snails lay giant eggs: the kiwi syndrome

Julián Monge-Nájera

doi:10.15517/rbt.v0i1.43811

Abstract

Some minute land snails lay disproportionally large eggs, and the reason is unknown. A possibility is the “Kiwi Syndrome”, in which natural selection pressures associated with low egg predation, heavy predation of the young, and a minimal viable size for hatchlings, force small females to invest in relatively large offspring at the cost of reduced fecundity.

Highlights

Barrientos (2000) suggested that the constraint for small eggs in a land snail could be a minimal quantity of nutrients needed for a viable egg, and presented the case of Ovachlamys fulgens, a land snail that maybe had larger ancestors and has difficulties laying its oversized eggs; to be able to lay these eggs, the snail has to invaginate its four tentacles and lays partially dehydrated eggs that absorb moisture from the substrate to reach their final size (Barrientos, 2000)
Egg size is unknown for the smallest land snails (Páll-Gergely, Hunyadi, Jochum, & Asami, 2015), but at least the idea of minimal size for a viable egg has a parallel in another group: in velvet worms, there is a minimal size for viable offspring, and small females are forced to give birth to large babies at the cost of reduced fecundity (Monge-Nájera, 1994)
A similar case among vertebrates is the kiwi, which produces a single egg that occupies much of the mother’s body cavity

Summary

Introduction

Baur (1989) suggested that there was some unknown structural or physiological constraint preventing the production of eggs smaller than 0.40 mm in diameter. Barrientos (2000) suggested that the constraint for small eggs in a land snail could be a minimal quantity of nutrients needed for a viable egg, and presented the case of Ovachlamys fulgens, a land snail that maybe had larger ancestors and has difficulties laying its oversized eggs; to be able to lay these eggs, the snail has to invaginate its four tentacles and lays partially dehydrated eggs that absorb moisture from the substrate to reach their final size (Barrientos, 2000). Baur (1989) suggested that there was some unknown structural or physiological constraint preventing the production of eggs smaller than 0.40 mm in diameter.

Results

Conclusion