Impact of thermal variation on the naupliar development of the copepod Apocyclops spartinus (Ruber, 1968) (Copepoda: Cyclopidae), under controlled conditions

ABSTRACT Apocyclops spartinus is a subtropical resilient copepod from impacted Peruvian wetlands, widely used for marine fish larviculture and conserved as a strain at Instituto del Mar del Peru - IMARPE. This study was conducted to test the effects of three thermal conditions (16, 20 and 24 ºC) on the individual growth of conditioned nauplii. Sub-stage growth rates, three growth models and three growth rate-dependent models were evaluated. Considering these previous experiments, naupliar growth retardation and mortality were evaluated for cold shock stress (8 ºC lower). Results indicated a progressive increase in development time by reducing temperature from 24 to 20 ºC (1.75 times) and 20 to 16 ºC (4 times). Growth rates showed a tendency to decrease, prior to metamorphosis and independent of temperature. Gompertz was the best growth model by describing sigmoidal tendency of naupliar development. Arrhenius was the best growth rate-dependent model but slightly better supported than a simple allometric model. Naupliar growth retardation was noted in nauplii that were initially hatched at 24 ºC and then swiftly transferred to a culture at 16 ºC. This cold shock stress resulted in high mortality from day four onwards. In summary, A. spartinus nauplii exhibit potential as a live food source and it is recommended that targeted thermal treatments be employed to extend the time of optimal nauplii size and thereby enhance culture techniques of this species.