Eurytemora americana egg production and morphology in the Bahía Blanca estuary, Argentina

BERASATEGUI, ANABELA A.; HOFFMEYER, MÓNICA S.; DUTTO, M. SOFÍA

Pucón

Simposio; 5th International Zooplankton Production Symposium; 2011

PICES-ICES-COPAS

The invader copepod Eurytemora americana develops a short planktonic pulse associated with the winterspring diatom bloom in the Bahía Blanca estuary. This species presents two markedly distinct reproductive strategies depending on the temporal environmental conditions. The aim of this study was to analyze the E. americana energetic balance taking into account certain metabolic and reproductive aspects. Relationships among environmental variables, clutch size (CS), female size (prosome length-PL), egg size (ES) and egg morphology by SEM were studied during the 2007 population pulse. Kruskal-Wallis tests and Principal Components Analysis (PCA- Spearman´s correlation matrix) were used in order to analyze differences between means and relationships among variables. During the population growth period, smaller ES (89.14 ? 94.48 μm, n=52), larger females and larger CS (114-101 eggs/sac) were observed. Conversely, in the population decline, an increase in ES (95.74 - 99.33μm, n=60) and a decrease in CS (40-5 eggs/sac) were registered. Very significant differences between ES (n=227, p=3.7742 E-18) were found along the population pulse. PCA showed clearly two different groups: CSPL- salinity-chlorophyll a and ES-temperature. A negative correlation (p < 0.05 n = 227) between ES-CS and ESPL, and a positive one (p<0.05 n=227) between ES and temperature were found. Morphological differences in the chorion between subitaneous and possible diapausal eggs were observed by SEM. During the population decline, E. americana would invest much of its energy in producing resting eggs showing in consequence, a reduction in its body mass and CS.