Biology of Boeckella poopoensis Marsh, 1906 (Copepoda, Calanoida) in natural conditions in temporary saline lakes of the central Argentina

Embryos of an Antarctic zooplankton require anoxia for dormancy, are permeable to lipophilic chemicals, and reside in sediments containing PCBs

Zooplankton in Antarctic maritime lakes face challenges imposed by anthropogenic chemicals. Studies on temperate species suggest that lipophilic chemicals will accumulate in dormant embryos of Antarctic zooplankton and decrease hatching success, thereby threatening centuries of accumulated genetic diversity that would increase population resilience in the face of climate change. We evaluated the potential for lakes to act as sinks for legacy pollutants in the maritime Antarctic by testing sediments for polychlorinated biphenyls (PCBs) previously identified in soil, flora and fauna of lake catchments. Direct tests of embryo permeability to chemicals are confounded by potential adhesion of chemicals to the embryo surface and limited biomass available. Therefore, in order to assess the potential for lipophilic chemicals to penetrate and passively accumulate in dormant embryos of Antarctic lacustrine zooplankton, we evaluated the effect of anoxia on post-diapause development in the calanoid copepod, Boeckella poppei, and then used chemical anoxia induced by rotenone as a reporter for permeability of these embryos to moderately lipophilic chemicals. The data presented demonstrate that embryos of B. poppei from Antarctic lake sediments will passively accumulate moderately lipophilic chemicals while lying dormant in anoxic sediments. Implications for legacy POPs in sediments of Antarctic maritime lakes are discussed.

Description of the postembryonic stages of Boeckella poopoensis (Crustacea, Copepoda, Centropagidae)

ABSTRACT Boeckella poopoensis Marsh, 1906 is one of the most common copepods in the saline lakes of South America, where generally is the species that greater contributes to the zooplankton community biomass. Despite of its wide geographic distribution and ecological importance, the characteristics of the postembryonic stages are unknown, which prevents a detailed understanding of the structure and dynamics of natural populations. The objective of this work was to describe the morphology of the postembryonic stages and to compare it with other species of Centropagidae. The specimens were obtained from a monospecific culture acclimatized in the laboratory. The lineage comes from El Carancho shallow lake (65°03’W, 37°27’S). The identification of the postembryonic stages was performed according to the characteristics established for copepod calanoids. Based in all developing stages, some characteristics that distinguish B. poopoensis from another species of the genus are: lobes of nauplii with the same number of setae of equal length; beginning of body segmentation from nauplii III; sexual dimorphism from copepodite IV (although only evident in the V leg); the endopod of the V leg of copepodites V males and females are biarticulate, but while females endopod add setae respect to the previous stage, males endopod lose them and remain glabrous as in the adults. Copepodites V do not present characteristics typical of adults, such as, the most developed thoracic left wing of females and in the geniculate right antenna of males. All stages of B. poopoensis are larger than those corresponding to other species of centropagids, and in the immature stages, the appendages show their own patterns of setae and have a slightly smaller number of setae than that of the other species of the family.