Reproduction and population structure of the salp Iasis zonaria (Pallas, 1774) in the southwestern Atlantic Ocean (34 30' to 39 30'S) during three successive winters (1999-2001)

DAPONTE, M.C.; PALMIERI, M.A.; CASARETO, B.E.; ESNAL, G. B.

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2013 vol. 35 p. 813 - 830

0142-7873

The salp Iasis zonaria is often found over the Argentine continental shelf of the southwestern Atlantic Ocean and, occasionally, its high densities dominate over other groups of zooplankton. Therefore, a better comprehension of the basic aspects of its life history is essential for understanding the mechanisms underlying bloom formation. In this study, I. zonaria was collected during the austral winters of 1999, 2000 and 2001. Additional data were obtained from this area from May to November 1978. The most widespread distribution and largest catches occurred in 1999 (55,100 ind. 10 m-2). Densities were markedly decreased in 2000 and the species was virtually absent in 2001. The growth of the solitary stage blastogenetic stolon and formation of several blocks of aggregates buds is described. Eight development stages were characterized and it was estimated that each solitary could produce at least 4 blocks and a total of 420 aggregates. The average number of buds per block increases from the older (first formed) to the youngest. The total number of buds (y) was related to solitary length (x) as follows: y= 4.94 x - 134.57. Four development stages were described for aggregate individuals. Based on monthly samples collected in 1978 the estimated life span of aggregate individuals was between 11 and 14 months.