Reproductive strategy of the copepod Acartia tonsa in a hypersaline estuary of Southwestern Atlantic. Seasonal morphology of eggs and ecological implications

BERASATEGUI, A.A.; FERNANDEZ SEVERINI, M.D.; MENENDEZ, M.C.; BIANCALANA, F.; DUTTO, M.S.; GUINDER, V.A.; LÓPEZ ABBATE, M.C.; CHAZARRETA, C.J.; HOFFMEYER, M.S.

MARINE BIOLOGY RESEARCH

TAYLOR & FRANCIS AS

Lugar: Londres; Año: 2016 vol. 12 p. 817 - 829

1745-1000

This study investigates the seasonal variation of the production, morphology and hatching success of Acartia tonsa eggs taking into account the variations of female?s size, population abundance and environmental factors in a turbid and hypersaline estuary. Sampling were performed considering the favorable (18-23°C and 32-36 salinity) and unfavorable periods (5-7ºC; 32-38) for this species in the Bahía Blanca Estuary (BBE). Incubation of field females were performed in laboratory simulating in situ condition and specimens from fixed samples were counted. Observations of egg?s morphology were made by SEM. A positive relationship of egg production with increasing temperature and salinity was revealed. An inverse relationship of the sizes of females and eggs with decreasing temperature was also detected. Acartia tonsa displayed a marked seasonality in its reproductive strategy which enabled it to the maintenance in the water column all year round in the BBE. To ensure high offspring during favorable period, this species invested its energy in the production of subitaneous eggs (12.95±2.38 eggs f-1d-1) with smooth appearance and high percentage of viable eggs. Otherwise, during unfavorable period, A. tonsa invests energy in body mass as well as in the production of three egg morphotypes (6.56±3.2 eggs f-1d-1) which respond to a phenotypic evolution to ensure its survival. Despite of differences in the length and shape of the egg s ´ spines, these three types of eggs had the same delayed hatching behavior and the eggs with shorter spines would integrate the resting egg bank in the bottom sediments of the estuary.