POPULATION STRUCTURE AND MATURITY STAGES OF FRITILLARIA BOREALIS (APPENDICULARIA, TUNICATA): SEASONAL CYCLE IN USHUAIA BAY (BEAGLE CHANNEL)

PRESTA MARIA LAURA; HOFFMEYER, MONICA; CAPITANIO, F.

BRAZILIAN JOURNAL OF OCEANOGRAPHY

INST OCEANOGRAFICO

Lugar: São Paulo; Año: 2015

1679-8759

Fritillaria borealis is a cosmopolitan species, very frequent in subantarctic and antarctic waters. The objective of this paper was to analyze its sizes structure and maturity stages at two sites of Ushuaia Bay: a coastal site exposed to anthropogenic pressure (E1) and a reference site (E2) located at the external zone of the bay. Zooplankton was collected during 2012 seasonal cycle. The sampling method involved the use of a 67 μmmesh net. Appendicularians were classified in four maturity stages: I) undifferentiated gonads, II) testis and ovary differentiated, III) expanded testis, IV)discharged testis, expanded ovary. Our results showed that highest densities of F. borealis occurred in spring and summer at both sites; coinciding with high values of chlorophylla. Percentage of juveniles (I and II) exhibited a spatial and temporal pattern similar to that observed for chlorophylla values. During springsummer,juveniles and matures (III and IV) showed a higher gonadal development than those individuals found in autumnwinter.In conclusion, the mismatching in the population structure and the pattern of densities of F. borealis between coastal and external zones would suggest the existence of two subpopulations susceptible to the influence of the anthropogenic impact in the bay.