Egg production and hatching patterns of Acartia erythraea (Copepoda, Calanoida), with a note on its two egg types, in a eutrophic bay in Korea

Abstract

Abstract Acartia erythraea, a copepod species commonly found in the summer, was sampled weekly using a conical net, in Gamak Bay (southern Korea) from 19 July to 14 November 2013. Egg production rate (EPR) and hatching success rate (HS) were estimated weekly during the study period, for egg types with distinct surface morphologies, i.e. smooth or spiny. EPR ranged from 1.0 to 25.0 eggs female−1 day−1 with a mean of 12.0 eggs female−1 day−1. The weight-specific growth rate (WSGR) ranged from 0.01 to 0.19 day−1 with a mean value of 0.09 day−1. Of these, all the eggs were smooth until August, whereas spiny eggs were produced from September, and the spiny eggs contributed 88% of the total eggs in November. Both egg types hatched within 12 to 48 h, and the average HS was 80% or higher. The EPR and WSGR were significantly related to water temperature but weakly related to chlorophyll-a concentration. Contrary to previous studies, our findings suggest that it is impossible to determine whether an egg is subitaneous or diapause based on the egg surface structure. Spines on the surface of A. erythraea eggs in Gamak Bay could be an adaptation to seasonal variations and a rapidly changing coastal environment.