Although ancient lakes may have different origins and characteristics, it is the diversity and endemism of their organisms that separate them from short-lived, post-glacial lakes. The latter parameters often serve as proxies for the recognition of such lakes (Martens, 1997).
However, longevity at least since before the last glacial period (i.e., ~120,000 years ago) or even since before the Pleistocene some 1.8 mya is often considered to be the only objective criterion for the recognition of ancient lakes.
Unfortunately, often the age of a given lake is poorly constrained, resulting in confusion about the designation as an ancient lake. Moreover, a lake may have come into existence a long time ago but may not have existed continuously throughout its history (e.g., Lake Victoria), thus not qualifying as ancient lake.
This and restricted knowledge of the faunas partly account for the existence of a number of disputed or unrecognized ancient lakes in the world that are outshone by their famous counterparts.
Lakes on the Balkan Peninsula and Asia Minor, for example, possess a number of these candidate lakes that all show some degree of endemism (e.g., lakes Trichonis, Skutari, Pamvotis, and Egirdir). In Asia, we find potential ancient lakes in China (e.g., lakes Dianchi and Erhai), and Mongolia (lakes Hövsgol/ Khubsugul). There are more candidate lakes that deserve to be explored regarding their evolution and biodiversity.
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Valvata klemmi (Schütt, 1962) of Lake Trichonis (photograph: K. Schreiber).
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Lake Victoria near Munyonyo/Uganda (photograph: C. Albrecht)