Land-snail eggs as a proxy of abrupt climatic cooling events during the reproductive season

Glacial-interglacial evolution of seasonal cooling events documented by land-snail eggs from Chinese loess

“…In this study, we investigate the evolution of seasonal cooling events on the glacial-interglacial timescale with an average resolution of about 600e1000 yr. First, we present a highresolution time series of land-snail eggs and shells from the Huining section spanning the last three glacial-interglacial cycles. Second, based on our recent studies (Li et al, 2021), we further confirm seasonal cooling events as the main potential factor controlling egg abundance. Third, we describe the changes in egg abundance and the evolution of seasonal cooling events during different stages of glacial-interglacial cycles for the last 350 kyr.…”

“…Abrupt cooling events during the reproductive season (spring in the CLP) can impact the egg abundance, and are therefore the most likely factor responsible for our observations (Li et al, 2021). Biological studies indicate that, although moisture has an impact, temperature is the most important limiting factor influencing egg hatching of all oviparous animals including land snails (e.g., Barker, 1985;Baur and Baur, 1993;Kozlowski, 2000;Chen, 2006;Panigrahi, 2008;Myzyk, 2011;Welter-Schultes, 2012).…”

“…They generate rapid temperature decreases of more than 8e10 C within 3e7 days or more (Qian, 1991), causing low spring temperatures (Fig. 1B) and therefore a large numbers of snail eggs not to hatch (Li et al, 2021). The spring daily average temperature minima and maxima in the Huining region vary between 0.6e10.3 C and 10.4e23.7 C, respectively (http://data.cma.…”

“…Among the various stages in the life cycle of animals, egg hatching is very sensitive to temperature changes during the reproductive season (Baur and Baur, 1993;Heller, 2001;Chen, 2006;Panigrahi, 2008;Myzyk, 2011). Eggs, therefore, have the potential to be a new and reliable proxy of seasonal cooling events (Li et al, 2021). However, our knowledge of fossil eggs comes mainly from dinosaurs and birds and these vertebrate eggs have rarely been used to study the evolution of seasonal events because they commonly have, like bone remains, a relatively discontinuous stratigraphic distribution (e.g., Miller et al, 1992;Wang et al, 2017).…”

“…Fortunately, abundant land-snail eggs have recently been observed to distribute continuously, at least over the last 1.3 Ma, in the loesspaleosol sequences of the Chinese Loess Plateau (CLP), East Asia (Li et al, 2019). Moreover, samplings in modern environments across the continental climate gradient from the CLP to East China reveal that unhatched land-snail eggs are likely to be a proxy of cold spring events (Li et al, 2021).…”