Reproductive strategy and egg morphology of the copepod Acartia tonsa in a temperate estuary, Argentina

BERASATEGUI, A. A.; HOFFMEYER M.S.; BIANCALANA F.; DUTTO, M.S.

Pucón

Simposio; 5th International Zooplankton Production Symosium; 2011

PICES-ICES-COPAS

The warm-water species Acartia tonsa has a wide distribution in estuarine areas, showing variation inmorphological and physiological characteristics of its subitaneous and resting eggs. This work aims to evaluatethe temporal variability in female size (PL-prosome length), egg production (EP), egg hatching success (HS)and egg morphology of Acartia tonsa in the Bahía Blanca estuary. Experimental incubations were conductedwith field females simulating in situ environmental conditions. Non-parametric tests were used to analyze therelationships among all variables. Three morphological types of eggs (I, II, III) were described according to theirspine length (SL) by optic microscopy and SEM (SL I: ≤2.55 μm; SL II: 3, 25-7.95 μm; SL III: 8.5 -16.15μm).Low egg production was recorded during the winter period (6.56 eggs. f-1.d-1) in which the presence of the threemorphotypes was observed. However, the chorion morphology was independent of the hatching response, beingthe three morphological types, resting eggs with delayed hatching. Eggs differed significantly in diameter (D) andSL during winter from the eggs that were laid during summer. Negative correlations between SL - temperature(- 0.95) and between D-temperature (-0.75), were found. On the other hand, a positive correlation (0.74) betweenD (including spines) and PL was detected. During the summer period smaller females, higher egg production ofsubitaneous type I eggs (12.95 eggs. f-1.d-1) and higher hatching success, were observed. Temporal variability inthe reproductive A. tonsa strategy, would allow it to remain in the plankton throughout the year.