Population biology of Sphaeroma serratum Fabricius (Isopoda, Flabellifera) at the Port of Mar del Plata, Argentina

KITTLEIN, MARCELO J.

JOURNAL OF NATURAL HISTORY

Taylor & Francis

Año: 1991 vol. 25 p. 1449 - 1459

0022-2933

Variations in size distribution, sex ratio, fecundity and morph frequencies in apopulation of Sphaeroma serratum were studied year-round. Changes in sizedistribution are most marked during the breeding season. Growth is arrested duringthe winter months. Young are produced throughout the summer; these overwinter,reproduce and then die. Differences in size of mature males suggest an effect of thetiming of birth on life-span. Females are able to produce two broods. Offspringnumber is positively correlated with female size. Brood pouch mortality is estimatedat 39%. Marked changes in sex ratio within the breeding season are thought to beartifacts due to sexual differences in behaviour. Comparison of reproductive traits ofthis, and other, populations shows a latitudinal pattern relatedto the duration of thewarm season. Analysis of morph frequencies revealed similarities with Europeanpopulations so far studied.