Population structure and maturity stages of Fritillaria borealis (Appendicularia, Tunicata): seasonal cycle in Ushuaia Bay (Beagle Channel)

Authors

  • María Laura Presta Universidad de Buenos Aires; Consejo Nacional de Investigaciones Científicas y Técnicas; Instituto de Biodiversidad y Biología Experimental y Aplicada
  • Mónica Susana Hoffmeyer Universidad Nacional del Sur; Consejo Nacional de Investigaciones Científicas y Técnicas; Instituto Argentino de Oceanografía
  • Fabiana Lia Capitanio Universidad de Buenos Aires; Consejo Nacional de Investigaciones Científicas y Técnicas; Instituto de Biodiversidad y Biología Experimental y Aplicada

DOI:

https://doi.org/10.1590/S1679-87592015087206303

Abstract

Fritillaria borealis is a cosmopolitan species, very frequent in sub-antarctic and antarctic waters. The objective of this paper was to analyze its size structure and maturity stages at two sites in Ushuaia Bay: a coastal site exposed to anthropogenic pressure (E1) and a reference site (E2) located in the external zone of the bay. Zooplankton was collected during the 2012 seasonal cycle. The sampling method involved the use of a 67 µm-mesh 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 the highest densities of F. borealisoccurred in spring and summer at both sites; coinciding with high values of chlorophyll-a. The percentage of juveniles (I and II) exhibited a spatial and temporal pattern similar to that observed for chlorophyll-a values. During spring-summer, juveniles and mature specimens (III and IV) showed a greater gonadal development than those individuals found in autumn-winter. 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 sub-populations susceptible to the influence of the anthropogenic impact in the bay.

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Published

2015-09-01

How to Cite

Presta, M. L., Hoffmeyer, M. S., & Capitanio, F. L. (2015). Population structure and maturity stages of Fritillaria borealis (Appendicularia, Tunicata): seasonal cycle in Ushuaia Bay (Beagle Channel) . Brazilian Journal of Oceanography, 63(3), 279-288. https://doi.org/10.1590/S1679-87592015087206303

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Original Article