Influence Of Different Diatoms On Copepod Reproduction And Its Insidious Reproductive Toxic Substances

Diatom is important primary producer in ocean ecosystem and has beenconsidered as well-quality food for sustaining the growth of zooplankton. Since themid-1990s, numerous studies have challenged this traditional view. Some marinediatoms have been found to have deleterious effects on copepod reproduction.Diatoms not only interfere with egg maturation but also induce strong developmentalaberrations in those nauplii that do develop to hatching. The negative effect ofdiatoms on copepod reproduction has been explained by the differential ability ofdiatom species/strains to generate oxylipins while mechanically handled by copepods.In the present study, diatoms Thalassiosira rotula, Skeletonema marinoi,Thalassiosira weissflogii, Thalassiosira pseudonana and dinoflagellatesProrocentrum minimum and Prorocentrum donghaiensis were selected to investigatetheir potential negative effects on the survival and reproduction of copepodsPseudodiaptomus annandalei and Pseudodiaptomus poplesia. Furthermore, detectionand analysis of oxylipins from target phytoplankton by using a protocol based on gaschromatography-mass spectrometry were conducted for the better understanding oftheir reproductive toxicology to the copepods.T. rotula, S. marinoi, T. weissflogii, and P. donghaiensis were used to feed P.poplesia. All tested phytoplankton were beneficial for survival and egg production offemale adult copepod. But T. rotula and S. marinoi had a negative influence on thenaupliar survival.Six mode of diets were used to feed P. annandalei: T. weissflogii, T. pseudonana,S. marinoi, P. minimum, mixed-food treatments TTS (T. weissflogii:T. pseudonanaand S. marinoi) and PTTS(P. minimum, T. weissflogii, T. pseudonana and S. marinoi).All tested alga were supportive to the survival of adult copepod. But S. marinoi ormixed-food (TTS or PTTS) had a negative influence on the egg production of parentaland first filial generation, also on the naupliar survival of the first and the second filialgeneration. Our results showed that all tested diets would not inhabit on the survivalof parental generation. But all diet containing S. marinoi had negative effects on thereproduction of copepod.Copepod feeding experiments have showed that dinoflagellate P. minimum and P.donghaiense and diatoms T. weissflogii and T. pseudonana did not exhibit an inhibitory effect on copepod reproduction, but S. marinoi and T. rotula had stronglyinsidious effects on the reproduction of copepod.GC-MS analysis results showed that S. marinoi, T. rotula and C. didymus canproduce oxylipins, which was not detected in P. donghaiensis, T. weissflogii and T.pseudonana. P. poplesia were fed on T. rotula, C. didymus and P. donghaiensis todetermine their toxic effects on reproduction. C. didymus and T. rotula had negativeimpact on the reproduction of P. poplesia. Diatom-derived oxylipins could play keyroles in interfering with reproduction of copepods.