Temperature and age affect the life history characteristics and fatty acid profiles of Moina macrocopa (Cladocera)

• Though the information on thermal effects on organisms is available in literature, most of this is related to the physiological aspects at the organism level. Moreover, most experiments have been conducted at fixed temperatures. Thus how planktonic cladocerans cope up with thermal stress within a 24 h diel cycle (difference of 10 °C) is not known.
• In this work we quantified the demographic responses and fatty acid profiles of Moina macrocopa cultured separately under different temperature regimes (20 °C, 25 °C and 30 °C and diurnally variable 20–30 °C). Our results showed that the highest constant temperature (30 °C) reduced the density of Moina macrocopa . The cladocerans under the fluctuating temperature regime too had lower population growth (about 50% lower than that at constant 25 °C).
• The survivorship of M. macrocopa was higher at 20 °C than that at 25 °C and 30 °C or at variable temperature regime. At 20 °C, neonates had the highest proportion (67%) of myristic, palmitic and stearic acids while the adults had the lowest (26%) proportion.
• For both adults and neonates, palmitoleic, linoleic and linolenic comprised of 15–35% of the total fatty acids. Higher percentage (19%) of linoleic acid was present in adults than neonates (7%). Our results thus show that there exists an interaction between temperature and fatty acid profiles of cladocerans which may explain adaptation in natural populations to climate variation.

Demographic responses and fatty acid profiles of Moina macrocopa were quantified under different temperature regimes (20 °C, 25 °C and 30 °C and diurnally variable 20–30 °C) and at fixed ration (10.65 µg DW ml−1) of Chlorella. Highest constant temperature (30 °C) reduced the density of M. macrocopa. The cladocerans under the fluctuating temperature regime too had lower population growth (about 50% lower than that at constant 25 °C). The survivorship of M. macrocopa was higher at 20 °C than that at 25 °C and 30 °C or at variable temperature regime. Gross and net reproductive rates were higher at 25 °C. At 20 °C, neonates had the highest proportion (67%) of myristic, palmitic and stearic acids while the adults had the lowest (26%) proportion. For both adults and neonates, palmitoleic, linoleic and linolenic comprised of 15–35% of the total fatty acids. Higher percentage (19%) of linoleic acid was present in adults than neonates (7%). Adults had linolenic acid level which was 3-times higher than in neonates. Linoleic and linolenic fatty acids decreased with increasing temperature for neonates and adults from 20 °C to 30 °C. The demographic responses and fatty acid profiles of M. macrocopa were discussed in relation to level and mode of temperature exposure.