Sediment cores from Lake Urmia (Iran) suggest the inhabitation by parthenogenetic Artemia around 5,000 years ago

Abstract

In Lake Urmia area, northwestern Iran, parthenogenetic Artemia and the bisexual Artemia urmiana Günther 1890 are found to occupy different ecological niches determined by salinity. Given the fluctuations of the lake over geological times, we thus hypothesized that species identification of Artemia cysts, buried in the sediments, can provide information on lake conditions in the past. Therefore, encysted embryos of Artemia were recovered from lake sediments by augering at a site near the present shoreline. Cysts and associated plant remains from two studied levels yielded radiocarbon ages in the range 5,000-6,700 YBP. For determination of the type of Artemia, the constant synonym mutation in exon-7 of the Na/K ATPase gene was verified, and the diameter of the recovered cysts was compared with that of modern cysts from the Lake Urmia region. The results show that the cysts represent a parthenogenetic type of Artemia, whose cyst diameter is somewhat different from that of present-day local parthenogenetic Artemia. The present study firstly confirms the stability of DNA in ancient Artemia cysts for molecular analysis. Moreover, it suggests variation in Lake Urmia's conditions over time, and based on comparison with salinity preferences of contemporary Artemia populations, it more specifically suggests that Lake Urmia was a brackish lake dominated by a parthenogenetic Artemia population in the geological period sampled. It finally illustrates how, like in the study of freshwater propagule banks, paleogenetic analysis of Artemia DNA recovered from sediment cores can be used as a tool in the paleoecological study of generally highly fluctuating saline habitats.

Geographical distribution and evolutionary divergence times of Asian populations of the brine shrimpArtemia(Crustacea, Anostraca)

“…Manaffar et al . () have argued that A. urmiana diverged 11 Mya, whereas Urmia Lake appears to have been formed later than that, in the late Pleistocene. If these estimates are correct, A. urmiana must have originated elsewhere and was later dispersed to Urmia Lake.…”

“…Muñoz et al (2010) emphasized that EHC lineages from Africa and Europe are relatively young, and are related to Holocene refugia. Manaffar et al (2011) have argued that A. urmiana diverged 11 Mya, whereas Urmia Lake appears to have been formed later than that, in the late Pleistocene. If these estimates are correct, A. urmiana must have originated elsewhere and was later dispersed to Urmia Lake.…”

Biodiversity of the Hypersaline Urmia Lake National Park (NW Iran)

“…However, another study of Artemia cysts (which are encysted gastrula embryos) collected from the western shore-line of Urmia Lake in 1987 revealed that Urmia Lake has both bisexual and parthenogenetic populations in the surrounding lagoons, especially on the western shore of the lake [62]. Sediment cores suggest that parthenogenetic populations of Artemia have lived in Urmia Lake for at least 5000 years [11]; however, the oldest remains of Artemia that have been recovered from a sediment core from this lake are 200,000 years old [63]. The two parthenogenetic Artemia populations from the Urmia Lake basin (those in the coastal lagoons and interior of the lake) have been tentatively attributed to two morphotypes that are not yet completely separated [64].…”

“…A progressive drought has caused fundamental changes in the physio-chemical composition of the lake-the salinity exceeds >300 g/L, the surface area has decreased to less than 2366 km 2 , the lake level has decreased to 1271 m, the volume of water has decreased from 42 to 22 billion m 3 between 1995 and 2010, and the water depth has decreased to 6 m, whereas reservoirs of dams have increased from 1.624 billion m 3 to 3.568 billion m 3 [9,11,12].…”

Resurrection ecology in Artemia

“…For example, Manaffar et al. () analyzed molecularly (by sequencing the exon 7 of the Na/K ATPase gene) the cysts bank of Lake Urmia (Iran) with radiocarbon ages estimated at ~5,000 years. This analysis showed that this ancient population was dominated by A. parthenogenetica (with some A. urmiana ).…”